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Objective: A shift towards overall larger very low-density lipoprotein (VLDL), and smaller low-density lipoprotein and high-density lipoprotein (HDL) diameters occurs in insulin resistance (IR), which reflects shifts in the distribution of the subfraction concentrations. Fenofibrate, indicated for hypertriglyceridemia, simultaneously reduces IR and shifts in lipoprotein diameter. Individual responses to fenofibrate vary, and we conducted a genome-wide association study to identify genetic differences that could contribute to such differences., Methods: Association analysis was conducted between single nucleotide polymorphisms (SNPs) on the Affymetrix 6.0 array and fasting particle diameter responses to a 12-week fenofibrate trial, in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network. Linear models were conducted, which adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. The top three SNPs associated with each fraction were examined subsequently for associations with changes in subfraction concentrations., Results: SNPs in AHCYL2 and CD36 genes reached, or closely approached, genome-wide levels of significance with VLDL and HDL diameter responses to fenofibrate, respectively (P=4×10(-9) and 8×10(-8)). SNPs in AHCYL2 were associated with a decrease in the concentration of the large VLDL subfraction only (P=0.002). SNPs associated with HDL diameter change were not associated with a single subfraction concentration change (P>0.05) indicating small shifts across all subfractions., Conclusion: We report novel associations between lipoprotein diameter responses to fenofibrate and the AHCYL2 and CD36 genes. Previous associations of these genes with IR emphasize the role of IR in mediating lipoprotein response to fenofibrate.

Objective: Fenofibrate, a peroxisome proliferator-activated receptor-α (PPARα) agonist, reduces triglyceride (TG) concentrations by 25-60%. Given significant interindividual variations in the TG response, we investigated the association of PPARA rare variants with treatment response in the Genetics of Lipid-Lowering Drugs and Diet Network study., Methods: We calculated the change in the TG concentration (ΔTG) among 861 GOLDN participants treated with fenofibrate (160 mg/day) for 3 weeks. From the distribution of ΔTG adjusted for age and sex, the 150 highest and 150 lowest fenofibrate responders were selected from the tails of the distribution for PPARA resequencing. The resequencing strategy was based on VariantSEQr technology for the amplification of exons and regulatory regions., Results: We identified 73 variants with an average minor allele frequency of 4.8% (range: 0.2-16%). We tested the association of rare variants located in a coding or a regulatory region (minor allele frequency<1%, 13 variants) with treatment response group by an indicator variable (presence/absence of ≥1 rare variant) using general linear mixed models to allow for adjustment for family relationship. After adjusting for baseline, fasting TG concentration carrying at least one rare variant was associated with a low fenofibrate response (odds ratio=6.46; 95% confidence interval: 1.4-30.8). Carrier status was also associated with a relative change in the total cholesterol concentration (P=0.02), but not high-density lipoprotein or low-density lipoprotein concentration., Conclusion: Rare, potentially functional variants in PPARA may play a role in the TG response to fenofibrate, but future experimental studies will be necessary to replicate the findings and confirm functional effects.

Background: Primary biliary cirrhosis and primary sclerosing cholangitis are two cholestatic diseases characterised by hepatic accumulation of bile acids., Aims: This study compares serum bile acid levels in patients with primary biliary cirrhosis and primary sclerosing cholangitis and from age and sex-matched non cholestatic donors., Methods: Seventeen bile acids were quantified using liquid chromatography coupled to tandem mass spectrometry. Serum samples from cholestatic patients were compared with those of non-cholestatic donors., Results: The concentration of total bile acids, taurine and glycine conjugates of primary bile acids was elevated in both patients with primary biliary cirrhosis and primary sclerosing cholangitis when compared to non-cholestatic donors. Samples from primary sclerosing cholangitis patients displayed reduced levels of secondary acids, when compared to non cholestatic and primary biliary cirrhosis sera. The ratio of total glycine versus total taurine conjugates was reduced in patients with primary biliary cirrhosis, but not in primary sclerosing cholangitis., Conclusion: The present study suggests that circulating bile acids are altered differentially in primary biliary cirrhosis and primary sclerosing cholangitis patients., (Copyright © 2011 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.)

Objective: Despite the evidence in support of the anti-inflammatory and triglyceride-lowering effects of fenofibrate, little is known about genetic determinants of the observed heterogeneity in treatment response. This study provides the first genome-wide examination of fenofibrate effects on systemic inflammation., Methods: Biomarkers of inflammation were measured in participants of the Genetics of Lipid Lowering Drugs and Diet Network (n=1092) before and after a 3-week daily treatment with 160 mg of fenofibrate. Two inflammatory patterns [high-sensitivity C-reactive protein-interleukin-6 and monocyte chemoattractant protein-1-tumor necrosis factor (MCP1-TNF-α)] were derived using principal component analysis. Associations between single nucleotide polymorphisms on the Affymetrix 6.0 chip and phenotypes were assessed using mixed linear models, adjusted for age, sex, study center, and ancestry as fixed effects and pedigree as a random effect., Results: Before fenofibrate treatment, the strongest evidence for association was observed for polymorphisms near or within the IL2RA gene with the high-sensitivity C-reactive protein-interleukin-6 (IL6) pattern (rs7911500, P=5×10 and rs12722605, P=5×10). Associations of the MCP1-TNF-α pattern with loci in several biologically plausible genes [CYP4F8 (rs3764563), APBB1IP (rs1775246), COL13A1 (rs2683572), and COMMD10 (rs1396485)] approached genome-wide significance (P=3×10, 5×10, 6×10, and 7×10, respectively) before fenofibrate treatment. After fenofibrate treatment, the rs12722605 locus in IL2RA was also associated with the MCP1-TNF-α pattern (P=3×10). The analyses of individual biomarker response to fenofibrate did not yield genome-wide significant results, but the rs6517147 locus near the immunologically relevant IFNAR2 gene was suggestively associated with IL6 (P=7×10)., Conclusion: We have identified several novel biologically relevant loci associated with systemic inflammation before and after fenofibrate treatment.

Introduction: CYP7A1 encodes cholesterol 7α-hydroxylase, an enzyme crucial to cholesterol homeostasis. Its transcriptional activity is downregulated by fenofibrate. The goal of this study was to determine the effect of CYP7A1 polymorphisms on lipid changes in response to fenofibrate., Methods: We examined the associations of 3 tagging single nuclear polymorphisms (i6782C>T, m204T>G, 3U12536A>C) at CYP7A1 with triglyceride (TG) and high-density lipoprotein cholesterol (HDL)-C responses to a 3-week treatment with 160 mg/d of fenofibrate in 864 US white participants from the Genetics of Lipid Lowering Drugs and Diet Network study., Results: The m204T>G variant was significantly associated with TG and HDL-C responses with fenofibrate. Individuals homozygous for the common T allele of m204T>G single nuclear polymorphism displayed both the greater reduction of TG (-32% for TT, -28% for GT, -25% for GG, P = 0.004) and an increase of HDL-C response compared with noncarriers (4.1% for TT, 3.4% for GT, 1.2% for GG, P = 0.01). Conversely, individuals homozygous for the minor allele of i6782C>T showed a greater increase in the HDL-C response compared with noncarriers (2.8% CC, 4.5% for CT, 5.8% for TT, P = 0.02), albeit no significant effect on TG response., Conclusions: Our data suggest that common variants at the CYP7A1 locus modulate the TG-lowering and HDL-C-raising effects of fenofibrate, and contribute to the interindividual variation of the drug responses.

A recent large-scale meta-analysis of genome-wide studies has identified 95 loci, 59 of them novel, as statistically significant predictors of blood lipid traits; we tested whether the same loci explain the observed heterogeneity in response to lipid-lowering therapy with fenofibrate. Using data from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN, n = 861) we fit linear mixed models with the genetic markers as predictors and high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, total cholesterol, and triglyceride concentrations as outcomes. For all four traits, we analyzed both baseline levels and changes in response to treatment with fenofibrate. For the markers that were significantly associated with fenofibrate response, we fit additional models evaluating potential epistatic interactions. All models were adjusted for age, sex, and study center as fixed effects, and pedigree as a random effect. Statistically significant associations were observed between the rs964184 polymorphism near APOA1 (P-value≤0.0001) and fenofibrate response for HDL and triglycerides. The association was replicated in the Pharmacogenetics of Hypertriglyceridemia in Hispanics study (HyperTG, n = 267). Suggestive associations with fenofibrate response were observed for markers in or near PDE3A, MOSC1, FLJ36070, CETP, the APOE-APOC1-APOC4-APOC2, and CILP2. Finally, we present strong evidence for epistasis (P-value for interaction =  0.0006 in GOLDN, 0.05 in HyperTG) between rs10401969 near CILP2 and rs4420638 in the APOE-APOC1-APOC4-APOC2 cluster with total cholesterol response to fenofibrate. In conclusion, we present evidence linking several novel and biologically relevant genetic polymorphisms to lipid lowering drug response, as well as suggesting novel gene-gene interactions in fenofibrate pharmacogenetics.

Background: Postprandial lipemia (PPL) is likely a risk factor for cardiovascular disease but these changes have not been well described and characterized in a large cohort. We assessed acute changes in the size and concentration of total and subclasses of LDL, HDL, and VLDL particles in response to a high-fat meal. Participants (n = 1048) from the Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN) Study who ingested a high-fat meal were included in this analysis. Lipids were measured at 0 hr (fasting), 3.5 hr, and 6 hr after a standardized fat meal. Particle size distributions were determined using nuclear magnetic resonance spectroscopy. Analyses were stratified by baseline triglycerides (normal vs. elevated) and gender. The effect of PPL on changes in lipoprotein subclasses was assessed using repeated measures ANOVA., Results: Postprandially, LDL-C, HDL-C, VLDL-C, and triglycerides increased regardless of baseline triglyceride status, with the largest increases in VLDL-C and TG; however, those with elevated triglycerides demonstrated larger magnitude of response. Total LDL particle number decreased over the 6-hour time interval, mostly from a decrease in the number of small LDL particles. Similarly, total VLDL particle number decreased due to reductions in medium and small VLDL particles. Large VLDL particles and chylomicrons demonstrated the largest increase in concentration. HDL particles demonstrated minimal overall changes in total particle number., Conclusions: We have characterized the changes in LDL and VLDL particle number, and their subclass patterns following a high-fat meal.

Fenofibrate belongs to the group of hypolipidemic fibrates that act as activators of the peroxisome proliferator-activated receptor-α (PPARα), which is a regulator of bile acid synthesis, metabolism, and transport. The present study aimed at evaluating the effects of fenofibrate on the circulating bile acid profile in humans. A study population of 200 healthy individuals comprising both genders completed a 3-week intervention with fenofibrate, and 17 bile acid species were measured in serum samples drawn before and after fenofibrate treatment. Fenofibrate caused significant reductions in levels of chenodeoxycholic (CDCA) (-26.4%), ursodeoxycholic (UDCA) (-30.5%), lithocholic (LCA) (-18.4%), deoxycholic (DCA) (-22.3%), and hyodeoxycholic (HDCA) (-19.2%) acids. A gender-related difference was observed in the responses of various bile acids, and the total bile acid concentration was significantly reduced only in men (-18.6%), whereas it remained almost unchanged in women (+0.36%). This difference suggests that fenofibrate would be more efficient at reducing bile acid toxicity in men than in women in cholestatic liver diseases.

Objective: Fenofibrate therapy reduces serum triglycerides (TG) and increases high-density lipoprotein-cholesterol (HDL-C) and thus addresses the atherogenic dyslipidemia associated with metabolic syndrome (MetS). Our hypothesis is that genetic factors contribute to the variability of lipid response to fenofibrate differently in subjects with MetS and without MetS., Methods: We investigated the association in 25 candidate genes with lipid responses to a 3-weeks trial on fenofibrate in subjects with and without MetS. We employed growth curve mixed models to generate the response phenotypes to fenofibrate in TG, HDL-C, and low-density lipoprotein-cholesterol (LDL-C) and examined the genetic associations accounting for family dependencies., Results: After correcting for multiple testing (p<0.05) and accounting for significant differences in the association effect sizes between subjects with and without MetS (p<0.05), variants of APOA5 (rs662799) and APOE (rs429358) were associated with HDL-C and LDL-C responses in MetS subjects, while APOA4 (rs675) was associated with TG response in non-MetS subjects. There was also suggestive evidence that MetS may interact with APOA4 (p=0.017), APOA5 (p=0.06), and APOE (p=0.09) to the variation to lipid responses., Conclusions: Genetic effects that contributed to the variability of lipid responses to fenofibrate may differ in subjects with and without MetS. This research may provide guidance for more personalized and effective therapies., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Background: Cardiovascular (CV) events are prevalent and expensive worldwide both in terms of direct medical costs at the time of the event and follow-up healthcare after the event. This study aims to determine initial and follow-up costs for cardiovascular (CV) events in US managed care enrollees and to compare to healthcare costs for matched patients without CV events., Methods: A 5.5-year retrospective matched cohort analysis of claims records for adult enrollees in ~90 US health plans. Patients hospitalized for first CV event were identified from a database containing a representative sample of the commercially-insured US population. The CV-event group (n = 29,688) was matched to a control group with similar demographics but no claims for CV-related events. Endpoints were total direct medical costs for inpatient and outpatient services and pharmacy (paid insurance amount)., Results: Overall, mean initial inpatient costs were US dollars ($) 16,981 per case (standard deviation [SD] = $20,474), ranging from $6,699 for a transient ischemic attack (mean length of stay [LOS] = 3.7 days) to $56,024 for a coronary artery bypass graft (CABG) (mean LOS = 9.2 days). Overall mean health-care cost during 1-year follow-up was $16,582 (SD = $34,425), an excess of $13,792 over the mean cost of matched controls. This difference in average costs between CV-event and matched-control subjects was $20,862 and $26,014 after two and three years of follow-up. Mean overall inpatient costs for second events were similar to those for first events ($17,705/case; SD = $22,703). The multivariable regression model adjusting for demographic and clinical characteristics indicated that the presence of a CV event was positively associated with total follow-up costs (P < 0.0001)., Conclusions: Initial hospitalization and follow-up costs vary widely by type of CV event. The 1-year follow-up costs for CV events were almost as high as the initial hospitalization costs, but much higher for 2- and 3-year follow-up.

Unlabelled: Bile acids are considered as extremely toxic at the high concentrations reached during bile duct obstruction, but each acid displays variable cytotoxic properties. This study investigates how biliary obstruction and restoration of bile flow interferes with urinary and circulating levels of 17 common bile acids. Bile acids (conjugated and unconjugated) were quantified by liquid chromatography coupled with tandem mass spectrometry in serum and urine samples from 17 patients (8 men and 9 women) with biliary obstruction, before and after biliary stenting. Results were compared with serum concentrations measured in 40 age- and sex-paired control donors (20 men and 20 women). The total circulating bile acid concentration increases from 2.7 µM in control donors to 156.9 µM in untreated patients with biliary stenosis. Serum taurocholic and glycocholic acids exhibit 304- and 241-fold accumulations in patients with biliary obstruction compared to controls. The enrichment in chenodeoxycholic acid species reached a maximum of only 39-fold, while all secondary and 6α-hydroxylated species--except taurolithocholic acids--were either unchanged or significantly reduced. Stenting was efficient in restoring an almost normal circulating profile and in reducing urinary bile acids., Conclusion: These results demonstrate that biliary obstruction affects differentially the circulating and/or urinary levels of the various bile acids. The observation that the most drastically affected acids correspond to the less toxic species supports the activation of self-protecting mechanisms aimed at limiting the inherent toxicity of bile acids in face of biliary obstruction.

Background: Although much is known about the effect of Apolipoprotein E (APOE) alleles on fasting lipid concentrations, less is known about the effect of APOE alleles on postprandial triglyceridemia or the triglyceride response to fenofibrate., Methods and Results: We evaluated the effects of the APOE locus on fasting and postprandial triglyceride concentrations as part of the Genetics of Lipid Lowering and Diet Network (GOLDN) study. Participants were evaluated after a high-fat meal challenge before (n=1072) and after 3 weeks of daily treatment with 160 mg of fenofibrate (n=738). Mixed models adjusted for sex, age, waist circumference, and family relationship were used to examine the association of the ε4 carrier and ε2 carrier status versus ε3 homozygotes with fasting triglycerides and the area under the curve (AUC) for triglycerides during the high-fat meal challenge. Compared with the ε3/ε3 genotype, ε2 carriers had on average higher fasting triglyceride concentrations (130.5 mg/dL versus 109.3 mg/dL, P<0.001). After fenofibrate treatment, the APOE genotype differences persisted in the fasting state (ε2 carriers: 85.1 mg/dL versus ε3/ε3: 75.9 mg/dL, P<0.05). Carriers of the ε4 allele had significantly higher fasting triglyceride concentrations only prefenofibrate (120.9 mg/dL versus 109.3 mg/dL, P=0.008). APOE alleles did not have an effect on response to fenofibrate. Postprandial triglycerides were significantly higher for ε2 carriers versus ε3 homozygotes (but not ε4 carriers) both before and after fenofibrate treatment (P=0.01 and P=0.005, respectively)., Conclusions: APOE polymorphisms are important determinants of triglyceride concentrations, especially in the fasting state.

Background: Previous studies have shown that ATP-binding cassette transporter 1 (ABCA1) polymorphisms associated with increased ABCA1 expression result in increased small HDL (high-density lipoprotein) subclass particle concentration. This study examines the effect of treatment with fenofibrate, a drug known to bind peroxisome proliferator-activated receptor alpha (PPARalpha) which increases the expression of ABCA1 gene, on lipoprotein subclass profiles of individuals stratified by ABCA1 genotypes., Methods: Participants of Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) were treated with fenofibrate over a three week period. We analyzed six ABCA1 polymorphisms in 287 GOLDN participants with triglyceride concentrations >or=150mg/dL and studied their associations with HDL subclass particle concentrations, as measured by nuclear magnetic resonance spectroscopy, before and after treatment., Results: Fenofibrate treatment did not result in significant changes in small HDL subclass particle concentration. When changes in HDL subclasses were stratified by ABCA1 polymorphism genotypes, there were no statistically significant associations between ABCA1 genotypes and small HDL subclasses before fenofibrate treatment. However, after fenofibrate treatment the KK genotype of R1587K (mean 4.40micromol/L; p=0.004) and the RK genotype of R219K (mean 1.60micromol/L; p=0.02) polymorphisms were associated with significantly increased small HDL. The R1587KKK genotype (mean 4.80micromol/L; p=0.0002) and the R219K KK genotype (mean 2.50micromol/L; p=0.02) were also associated with increased HDL particle concentrations., Conclusion: There is a synergistic effect between ABCA1 polymorphisms and fenofibrate. Thus, our study indirectly confirms the role of fenofibrate and genotype in increasing cholesterol efflux, as evidenced by increased small HDL particles.

The fibric acid derivative, fenofibrate (FF) has been used in the US since 1998 to manage patients with dyslipidemia. Typical changes in serum lipids as result a of FF treatment include clinically important mean reductions of serum triglycerides (TG) by a mean change of -93.7 mg/dL (-39.3%), increases of high density lipoprotein cholesterol (HDLC) by +5.5 mg/dL (+12.4%), and reductions in low density lipoprotein cholesterol (LDLC) by -17.9 mg/dL (-12.3%). The greatest reductions in serum TG are usually observed in subjects with elevated baseline TGs including those with the metabolic syndrome (MetS). Although statins remain the mainstay of therapy for most dyslipidemic patients, their combined use with FF would be expected to address residual risk resulting from less than optimal TG and HDLC levels in such patients. Clinical trials examining the cardiovascular benefits of FF alone or combined with statins have produced mixed results. These observations underscore our lack of understanding of which patients may benefit from FF therapy and which do not. Although FF's basic mechanism of action is known to involve PPAR-alpha agonist activity resulting in altered transcription of several genes, the actual genetic bases for variability in lipid response is poorly understood. Studies, such as our GOLDN study and others designed to better understand the genetic determinants of variability in the response to FF treatment and lipid levels. As a result several important genetic determinants of lipid levels have been identified. For example, in the GOLDN study SNPs from different genes were significantly associated with baseline lipid levels before treatment (APOA5- rs662799, rs3135506; APOC3- rs5128, rs2854117, rs4520); APOA4- rs5104; PPARA- rs9626730, rs135543, rs11703495; LPL- rs1801177), after treatment PPARA- rs11708495; LPL- rs1801177, and appeared to modulate overall response to FF treatment (NOS3- rs1799983). In this article, we will review the literature leading up to the contemporary use of FF as an agent to manage patients with dyslipidemia and focus on emerging understanding of the genetic variability in response to FF treatment. On the basis of the available evidence, we conclude that FF is of benefit in the treatment of dyslipidemia, especially among those with MetS. However, more work is needed to specifically identify which individuals derive a benefit from FF administration in terms of clinical outcomes and which do not - particularly in the context of type 2 diabetes., Competing Interests: CONFLICTS OF INTERESTS None to declare.

Context: The fenofibrate effect on the subclass size distribution of lipoproteins before and after a high-fat challenge is not well studied., Objective: To characterize the baseline and post-prandial response (PPL) to a high-fat challenge following fenofibrate therapy, on changes in LDL, HDL, and VLDL particle subclasses, number, and size in 271 hypertriglyceridemic participants., Methods: Participants from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study who conducted PPL studies both before and after three weeks of fenofibrate (160 mg/d) treatment were analyzed. Particle size distributions were determined using nuclear magnetic resonance imaging, and lipid determinations were measured at fasting (0 hr), 3.5 hours, and 6 hours after ingestion of a standardized high-fat meal. Analyses were stratified by gender. Changes in particle subclass distributions were assessed using repeated measures analysis of variance adjusted for pedigree., Results: Before PPL, fenofibrate in men (adjusted for age, field center, smoking status, diabetes, and weight circumference) lowered fasting and postprandial VLDL primarily due to reductions in postprandial levels of large and medium VLDL particles (9 SE +/-0.7 to 4 +/-0.4 and 78 / -4 to 36 / -3 nmol/L both P < .0001, resp.). Fenofibrate also reduced fasting and postprandial total LDL particles, primarily a result of reduced small LDL particles (1497 = / - 37 to 1088 = / - 36 nmol/L, P < .0001). Directional changes were similar in men and women but the magnitude of change was different for some parameters., Conclusion: Fenofibrate treatment resulted in a lower triglyceride excursion following a high-fat meal. This investigation provides new knowledge of the magnitude and time course of fenofibrate induced attenuation of Lipoprotein subclass size distribution following a postprandial lipid challenge.

Background and Aims: Several genes have been shown to individually affect plasma lipoprotein metabolism in humans. Studies on gene-gene interactions could offer more insight into how genes affect lipid metabolism and may be useful in predicting lipid concentrations. We tested for gene-gene interactions between TaqIB SNP in the cholesterol ester transfer protein (CETP) and three novel single nucleotide polymorphisms (SNPs), namely rs11774572, rs7819412 and rs6995374 for their effect on metabolic syndrome (MetS) components and related traits., Methods and Results: The aforementioned SNPs were genotyped in 1002 subjects who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study. Lipids were measured by standard procedures and lipoprotein subfractions, by proton nuclear magnetic resonance spectroscopy. Polymorphism rs11774572 was significantly associated with MetS (P=0.020), mainly driven by the association of the C allele with lower HDL-C (P=0.043) and higher triglycerides (P=0.049) and insulin (P=0.040) concentrations than TT subjects. A significant interaction between SNPs rs11774572 and CETP-TaqIB SNPs was found for HDL-C concentrations (P=0.006) and for HDL (P=0.008) and LDL particle sizes (P=0.009), small LDL (P=0.004), and VLDL concentrations (P=0.021), in which TT homozygotes displayed higher HDL-C concentrations and for HDL and LDL particle sizes, and lower small LDL and VLDL concentrations than C carriers, if they were CETP B2 allele carriers (P values ranging from <0.001 to 0.001)., Conclusions: The rs11774572 polymorphism may play a role in the dyslipidemia that characterizes MetS. The interaction between rs11774572 and CETP-TaqIB SNPs on HDL-C concentrations provides some insights into the underlying mechanisms., (Copyright 2009 Elsevier B.V. All rights reserved.)

Fenofibric acid (FA), the active moiety of fenofibrate, is an agonist of the peroxisome proliferator-activated nuclear receptor alpha that modulates triglyceride and cholesterol profiles. Lipid response to fenofibrate and FA serum concentrations is highly variable. Although FA is reported to be almost exclusively inactivated by UDP-glucuronosyltransferases (UGTs) into FA-glucuronide (FA-G), the contribution of UGT isoenzymes has never been systematically assessed. Heterologously expressed human UGT1A and UGT2B and their coding variants were tested for FA glucuronidation using liquid chromatography/mass spectrometry. Recombinant UGT2B7 presented the highest V(max)/K(m) value (2.10 microl/min/mg), 16-fold higher than the activity of other reactive UGTs, namely, UGT1A3, UGT1A6, and UGT1A9 (0.13, 0.09, and 0.02 microl/min/mg, respectively). UGT2B7.1 (His(268)) and UGT2B7.2 (Tyr(268)) enzyme activity was similar, whereas UGT1A3.2 (R(11)A(47)), UGT1A3.3 (Trp(11)), and UGT1A9.3 (Thr(33)) showed 61 to 96% reduced V(max)/K(m) values compared with the respective (1) reference proteins. FA-G formation by a human liver bank (n = 48) varied by 10-fold, but the rate of formation was not associated with common genetic variations in UGT1A3, UGT1A6, UGT1A9, and UGT2B7. Correlation with activities for the probe substrates zidovudine (UGT2B7; r(2) = 0.75), mycophenolic acid (UGT1A9; r(2) = 0.42), fulvestrant (UGT1A3; r(2) = 0.36), but not serotonin (UGT1A6; r(2) = 0.06) indicated a primary role for UGT2B7 and lesser roles of UGT1A9 and UGT1A3 in hepatic FA glucuronidation. This was confirmed by a strong correlation of FA-G formation with UGT2B7 protein content and inhibition by fluconazole, a known UGT2B7 selective inhibitor. Additional studies are required to identify genetic factors contributing to the observed FA glucuronidation variability.

Background: Patients with type 2 diabetes are at increased risk of cardiovascular events, and there is an associated economic burden attached to this risk. We conducted a retrospective claims database analysis to evaluate incremental cardiovascular costs in diabetic versus non-diabetic patients hospitalized for a cardiovascular event., Methods: Patients hospitalized for a cardiovascular event between January 1, 2001 and June 30, 2005 were identified from a large US managed-care population. Diabetic patients were identified by evidence of type 2 diabetes in the 12 months prior to the index hospitalization. Direct medical costs and resource use - including inpatient expenditures (for the index and first recurrent hospitalizations), as well as outpatient, laboratory, and pharmacy expenditures (during the 3-year follow-up period) - were determined for patients with or without diabetes., Results: Of the 29,863 patients identified with a cardiovascular hospitalization, 5,501 patients (18.4%) had a history of diabetes in the pre-index period (mean age, 57.8 years; 42.1% female). The overall mean follow-up period was 22.8 months. The incidence of subsequent cardiovascular events in the first year of follow-up was significantly higher for patients with diabetes compared with non-diabetic patients for all types of cardiovascular events except angina. Compared with non-diabetic patients, patients with diabetes had similar mean direct medical costs per patient for the index cardiovascular hospitalization ($17,435 versus $16,917; P = 0.09), and the first recurrent cardiovascular hospitalization ($18,488 versus $17,481; P = 0.2), yet higher mean total direct medical costs per patient for cardiovascular events during follow-up years (Year 1: $8,805 versus $6,982; Year 2: $13,860 versus $10,056; Year 3: $16,149 versus $12,163; all P < or = 0.0002). The cost difference between diabetic and non-diabetic patients remained significant after adjusting for age, gender and other potential confounders in multivariate regression analysis. The mean (SD) total period of inpatient cardiovascular hospitalization after 3 years of follow-up was 3.3 (12.4) days for patients with diabetes compared with 1.8 (5.8) days for non-diabetic patients (P < 0.0001)., Conclusion: Diabetic patients hospitalized for a cardiovascular event incur higher costs for cardiovascular care than their non-diabetic counterparts. This analysis of the incremental cardiovascular cost and resource use provides the basis for greater accuracy and precision when modeling the economic value of initiatives aimed at reducing cardiovascular morbidity in patients with diabetes mellitus.

The scaffolding protein PDZ domain containing 1 (PDZK1) regulates the HDL receptor scavenger receptor class B type I. However, the effect of PDZK1 genetic variants on lipids and metabolic syndrome (MetS) traits remains unknown. This study evaluated the association of 3 PDZK1 single nucleotide polymorphisms (SNP) (i33968C > T, i15371G > A, and i19738C > T) with lipids and risk of MetS and their potential interactions with diet. PDZK1 SNP were genotyped in 1000 participants (481 men, 519 women) included in the Genetics of Lipid Lowering Drugs and Diet Network study. Lipoprotein subfractions were measured by proton NMR spectroscopy and dietary intake was estimated using a validated questionnaire. The PDZK1&#95;i33968C > T polymorphism was associated with MetS (P = 0.034), mainly driven by the association of the minor T allele with higher plasma triglycerides (P = 0.004) and VLDL (P = 0.021), and lower adiponectin concentrations (P = 0.022) than in participants homozygous for the major allele (C). We found a significant gene x BMI x diet interaction, in which the deleterious association of the i33968T allele with MetS was observed in obese participants with high PUFA and carbohydrate (P-values ranging from 0.004 to 0.020) intakes. Conversely, a there was a protective effect in nonobese participants with high PUFA intake (P < 0.05). These findings suggest that PDZK1&#95;i33968C > T genetic variants may be associated with a higher risk of exhibiting MetS. This gene x BMI x diet interaction offers the potential to identify dietary and other lifestyle changes that may obviate the onset of MetS in individuals with a specific genetic background.

Adipose (adp) is an obesity gene in Drosophila and mice with crucial functions in fat metabolism. We investigated the correlation between genetic variation of the WDTC1 locus, the ortholog of adp, and human obesity. Five WDTC1 single-nucleotide polymorphisms (SNPs) were genotyped in 935 and 1,115 adults of two ethnically diverse US populations. In the Boston Puerto Rican population, we demonstrated that two WDTC1 SNPs strongly associated with obesity. Homozygote and heterozygote carriers of the major allele i22835A, representing approximately 96% of the population, had significantly higher mean BMI (31.5 and 31.0 kg/m(2), respectively) than noncarriers (28.6 kg/m(2)). Conversely, homozygotes of the minor allele i22835G were leaner and were 74% less likely to be overweight or obese (odds ratio (OR) = 0.26, P = 0.003) compared to homozygote carriers of the major allele. Haplotype analyses based on two SNPs further supported these findings. In addition, we found a strong interaction of monounsaturated fatty acid (MUFA) intake by genotype in this population. As dietary MUFA intake increased, minor allele carriers of SNP i22835A>G had higher BMIs, whereas major allele carriers had lower BMIs. A white population also exhibited a pattern of association between WDTC1 genotypes and obesity although of a different nature. Those WDTC1 variants which associated with obesity likely have experienced strong positive selection in human history, when food supply was unpredictable. Given the high frequency of the major alleles in both populations, we suggest that WDTC1 variation may be an important risk factor contributing to obesity in these populations.

The transcription factor 7-like 2 (TCF7L2) has been recently associated with diabetes risk, and it may exert its effect through metabolic syndrome (MetS)-related traits and be subjected to modification by environmental factors. We investigated the effect of single nucleotide polymorphisms (SNP), rs7903146 and rs12255372, within the TCF7L2 locus on postprandial lipemia and other MetS-related traits and their modulation by dietary fat. Data were collected from 1083 European Americans participating in the Genetics of Lipid Lowering Drugs and Diet Network Study. Carriers of the minor T allele at the C/T rs7903146 SNP had higher fasting plasma glucose (P = 0.012), lower homeostasis model assessment of beta cell function (P = 0.041), higher plasma VLDL (P = 0.035), and lower large LDL particle (P = 0.007) concentrations and higher risk of MetS (P = 0.011) than CC individuals. Moreover, we identified significant interactions between this SNP and PUFA intake modulating fasting VLDL particle concentrations (P = 0.016) and postprandial triglycerides (TG) (P = 0.028), chylomicrons (P = 0.025), total VLDL (P = 0.026), and large VLDL (P = 0.018) concentrations. Thus, only T allele carriers with a PUFA intake > or = 7.36% of energy had elevated fasting plasma VLDL concentrations and postprandial TG-rich lipoproteins. These variables did not differ in T allele carriers and noncarriers in the low-PUFA intake group. Moreover, these significant interactions were due exclusively to (n-6) PUFA intake. In summary, high (n-6) PUFA intakes (> or = 6.62% of energy intake) were associated with atherogenic dyslipidemia in carriers of the minor T allele at the TCF7L2 rs7903146 SNP and may predispose them to MetS, diabetes, and cardiovascular disease.

Serum adiponectin levels have been positively associated with insulin sensitivity and are decreased in type 2 diabetes (T2D) and obesity. Genetic and environmental factors influence serum adiponectin and may contribute to risk of metabolic syndrome and T2D. Therefore, we investigated the effect of ADIPOQ single-nucleotide polymorphisms (SNPs), -11377C>G and -11391G>A, on metabolic-related traits, and their modulation by dietary fat in white Americans. Data were collected from 1,083 subjects participating in the Genetics of Lipid Lowering Drugs and Diet Network study. Mean serum adiponectin concentration was higher for carriers of the -11391A allele (P = 0.001) but lower for the -11377G allele carriers (P = 0.017). Moreover, we found a significant association with obesity traits for the -11391G>A SNP. Carriers of the -11391A allele had significantly lower weight (P = 0.029), BMI (P = 0.019), waist (P = 0.003), and hip circumferences (P = 0.004) compared to noncarriers. Interestingly, the associations of the -11391G>A with BMI and obesity risk were modified by monounsaturated fatty acids (MUFAs) intake (P-interaction = 0.021 and 0.034 for BMI and obesity risk, respectively). In subjects with MUFA intake above the median (> or =13% of energy intake), -11391A carriers had lower BMI (27.1 kg/m(2) for GA+AA vs. 29.1 kg/m(2) for GG, P = 0.002) and decreased obesity risk (odds ratio for -11391A = 0.52, 95% confidence interval (CI); 0.28-0.96; P = 0.031). However, we did not detect genotype-related differences for BMI or obesity in subjects with MUFA intake <13%. Our findings support a significant association between the -11391G>A SNPs and obesity-related traits and the potential to moderate such effects using dietary modification.

Background: The apolipoproteins (APOA1/C3/A4/A5) are key components in modulating lipoprotein metabolism. It is unknown whether variants at the APOA1/C3/A4/A5 gene cluster are associated with lipid response to pharmacologic intervention., Methods and Results: Plasma triglycerides (TGs) and high-density lipoprotein (HDL) levels were measured in 861 Genetics of Lipid-Lowering Drugs and Diet Network study participants who underwent a 3-week fenofibrate trial. We examined 18 common single nucleotide polymorphisms (SNPs) spanning the APOA1/C3/A4/A5 genes to investigate the effects of variants at the gene cluster on lipid response to fenofibrate treatment. We found that the minor alleles of the SNPs rs3135506 (APOA5&#95;S19W), rs5104 (APOA4&#95;N147S), rs4520 (APOC3&#95;G34G), and rs5128 (APOC3&#95;3U386) were associated with enhanced TG response to fenofibrate treatment (P= 0.0004-0.018). The minor allele of SNP rs2854117 (APOC3&#95;M482) was associated with reduced rather than enhanced TG response (P= 0.026). The SNP rs3135506 (APOA5&#95;S19W) was associated with HDL response, with minor allele related to reduced HDL response to fenofibrate (P= 0.002). Association analyses on haplotype provided corroborative evidence to single SNP association analyses. The common haplotypes H2, H3, and H5 were significantly associated with reduced TG response to fenofibrate., Conclusion: The genetic variants at APOA1/C3/A4/A5 gene cluster may be useful markers to predict response of lipid-lowering therapy with fenofibrate. Further studies to replicate/confirm our findings are warranted.

Background: Hypertriglyceridemia is a risk factor for cardiovascular disease. Variation in the apolipoprotein A5 (APOA5) and glucokinase regulatory protein (GCKR) genes has been associated with fasting plasma triacylglycerol., Objective: We investigated the combined effects of the GCKR rs780094C-->T, APOA5 -1131T-->C, and APOA5 56C-->G single nucleotide polymorphisms (SNPs) on fasting triacylglycerol in several independent populations and the response to a high-fat meal and fenofibrate interventions., Design: We used a cross-sectional design to investigate the association with fasting triacylglycerol in 8 populations from America, Asia, and Europe (n = 7,730 men and women) and 2 intervention studies in US whites (n = 1,061) to examine postprandial triacylglycerol after a high-fat meal and the response to fenofibrate. We defined 3 combined genotype groups: 1) protective (homozygous for the wild-type allele for all 3 SNPs); 2) intermediate (any mixed genotype not included in groups 1 and 3); and 3) risk (carriers of the variant alleles at both genes)., Results: Subjects within the risk group had significantly higher fasting triacylglycerol and a higher prevalence of hypertriglyceridemia than did subjects in the protective group across all populations. Moreover, subjects in the risk group had a greater postprandial triacylglycerol response to a high-fat meal and greater fenofibrate-induced reduction of fasting triacylglycerol than did the other groups, especially among persons with hypertriglyceridemia. Subjects with the intermediate genotype had intermediate values (P for trend <0.001)., Conclusions: SNPs in GCKR and APOA5 have an additive effect on both fasting and postprandial triacylglycerol and contribute to the interindividual variability in response to fenofibrate treatment.

Chronically elevated interleukin-6 (IL-6) affects lipid and lipoprotein metabolism. Individuals genetically predisposed to higher IL-6 secretion may be at risk of dyslipidemia, especially during the postprandial phase. We investigated the effect of genetic variants at the IL6 locus on postprandial lipemia in US Whites participating in the Genetics of Lipid Lowering Drugs and Diet Network study. Subjects were given a single fat load composed of 3% of calories as protein, 14% as carbohydrate, and 83% as fat. Blood was drawn at 0 h, 3.5 h, and 6 h to determine plasma triglyceride (TG), TG-rich lipoprotein (TRL) and lipoprotein particle size. Homozygotes (GG) and heterozygotes (CG) of the -174C/G variant displayed higher plasma IL-6 concentrations compared with major allele homozygotes (CC) (P = 0.029). GG and CG subjects showed higher fasting plasma TG (P = 0.025), VLDL (P = 0.04), and large VLDL (P = 0.02) concentrations than did CC subjects. Moreover, GG and CG subjects experienced greater postprandial response of TG (P = 0.006) and TRL, including chylomicrons (P = 0.005), total VLDL (P = 0.029), and large VLDL (P = 0.017) than did CC subjects. These results suggest that the functional polymorphism -174C>G at the IL6 locus determines the difference in both fasting and postprandial TG metabolism. This phenomenon could be responsible for the observed association of this genetic variant with cardiovascular disease risk.

Metabolic response to the triglyceride (TG)-lowering drug, fenofibrate, is shaped by interactions between genetic and environmental factors, yet knowledge regarding the genetic determinants of this response is primarily limited to single-gene effects. Since very low-density lipoprotein (VLDL) is the central carrier of fasting TG, identifying factors that affect both total TG and VLDL-TG response to fenofibrate is critical for predicting individual fenofibrate response. As part of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study, 688 individuals from 161 families were genotyped for 91 single-nucleotide polymorphisms (SNPs) in 25 genes known to be involved in lipoprotein metabolism. Using generalized estimating equations to control for family structure, we performed linear modeling to investigate whether single SNPs, single covariates, SNP-SNP interactions, and/or SNP-covariate interactions had a significant association with the change in total fasting TG and fasting VLDL-TG after 3 weeks of fenofibrate treatment. A 10-iteration fourfold cross-validation procedure was used to validate significant associations and quantify their predictive abilities. More than one-third of the significant, cross-validated SNP-SNP interactions predicting each outcome involved just five SNPs, showing that these SNPs are of key importance to fenofibrate response. Multiple variable models constructed using the top-ranked SNP--covariate interactions explained 11.9% more variation in the change in TG and 7.8% more variation in the change in VLDL than baseline TG alone. These results yield insight into the complex biology of fenofibrate response, which can be used to target fenofibrate therapy to individuals who are most likely to benefit from the drug.

The scavenger receptor class B type 1 (SCARB1) gene is a key component in the reverse cholesterol transport pathway and thus plays an important role in lipid metabolism. Studies suggest that the SCARB1 gene may contribute to variation in plasma lipid levels at fasting; however, the results have been inconsistent, and it is unclear whether SCARB1 may also influence lipid response to dietary and pharmacologic interventions. In this study, we examined genetic variation in the SCARB1 gene in participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study for associations with basal lipid levels, changes in lipid measures after dietary fat intake, and fenofibrate treatment. We found that the exon 1 variant SCARB1&#95;G2S was significantly associated with postfenofibrate change for triglycerides (TG) (P = 0.004). Subjects bearing SCARB1&#95;G2S minor allele A tend to have higher responsiveness to fenofibrate in lowering TG. In summary, our study suggested that the SCARB1 gene may serve as a useful marker that predicts variation in baseline lipid levels, postprandial lipid response, and response to fenofibrate intervention.

Chronic inflammation has been identified as an important component of the metabolic syndrome (MetS). Therefore, environmental and genetic factors contributing to the variation of inflammatory responses could affect individuals' susceptibility to MetS. We investigated the association between common IL1beta genetic polymorphisms, inflammation, and the MetS, and the modulation of diet-related variables (i.e., erythrocyte membrane fatty acid composition) in a white U.S. population. IL1beta single nucleotide polymorphisms (SNP) (-1473G > C, -511G > A, -31T > C, 3966C > T, 6054G > A), clinical and biochemical measurements were characterized in a total of 1120 subjects (540 males and 580 females) participating in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) Study. The 6054 G > A SNP was significantly associated with plasma C-reactive protein (P = 0.054), adiponectin (P = 0.021), and the prevalence of MetS (P = 0.004). Moreover, there was a significant interaction between the 6054G > A SNP and erythrocyte membrane (n-3) PUFA (P = 0.019). Among subjects with low (n-3) PUFA content (below the median), the 6054 G allele was associated with increased risk of the MetS (OR = 3.29, 95%CI = 1.49-7.26 for GG and OR = 1.95, 95%CI = 0.85-4.46 for GA, P < 0.001) compared with the AA genotype, but there were no significant genotype associations among subjects with high (n-3) PUFA content (above the median). Further analyses supported a significant haplotype global effect on the MetS (P = 0.017) among subjects with low (n-3) PUFA content. These results suggested that IL1beta genetic variants were associated with measures of chronic inflammation and the MetS risk, and that genetic influences were more evident among subjects with low (n-3) PUFA intake.

Objective: Apolipoprotein A5 (APOA5) is a key determinant of plasma triglyceride (TG) concentrations. Genetic variation at the APOA5 locus could be responsible for some of the observed differences in response to fenofibrate therapy., Methods and Results: We examined the association between tag SNPs (-1131T>C and 56C>G) at APOA5 and TG and HDL-C response to fenofibrate and a postprandial lipid challenge in 791 men and women participating in the GOLDN study. After 3-week drug treatment, APOA5 56G carriers displayed significant decrease in TG (P=0.006), and increase in HDL-C (P=0.002) levels relative to their basal values in the fasting state when compared with noncarriers (a TG reduction of -35.8+/-2.8% versus -27.9+/-0.9% and a HDL-C increase of 11.8+/-1.3% versus 6.9+/-0.5%, respectively). In the postprandial lipemia after a fat load, the 56G carriers showed a significant decrease in the area under curve for TG and increase for HDL-C than the noncarriers. These diverse beneficial responses of 56G carriers to fenofibrate were further characterized by a higher increase in large LDL-C concentrations and LDL size. On the other hand, subjects with different APOA5-1131T>C genotypes showed no significant response to fenofibrate intervention., Conclusion: This study suggests that the APOA5 56G carriers benefited more from the fenofibrate treatment than noncarriers in lowering plasma TG and increasing HDL-C levels.

Background: Apolipoprotein A-II (APOA2) plays an ambiguous role in lipid metabolism, obesity, and atherosclerosis., Methods: We studied the association between a functional APOA2 promoter polymorphism (-265T>C) and plasma lipids (fasting and postprandial), anthropometric variables, and food intake in 514 men and 564 women who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study. We obtained fasting and postprandial (after consuming a high-fat meal) measures. We measured lipoprotein particle concentrations by proton nuclear magnetic resonance spectroscopy and estimated dietary intake by use of a validated questionnaire., Results: We observed recessive effects for this polymorphism that were homogeneous by sex. Individuals homozygous for the -265C allele had statistically higher body mass index (BMI) than did carriers of the T allele. Consistently, after multivariate adjustment, the odds ratio for obesity in CC individuals compared with T allele carriers was 1.70 (95% CI 1.02-2.80, P = 0.039). Interestingly, total energy intake in CC individuals was statistically higher [mean (SE) 9371 (497) vs 8456 (413) kJ/d, P = 0.005] than in T allele carriers. Likewise, total fat and protein intakes (expressed in grams per day) were statistically higher in CC individuals (P = 0.002 and P = 0.005, respectively). After adjustment for energy, percentage of carbohydrate intake was statistically lower in CC individuals. These associations remained statistically significant even after adjustment for BMI. We found no associations with fasting lipids and only some associations with HDL subfraction distribution in the postprandial state., Conclusions: The -265T>C polymorphism is consistently associated with food consumption and obesity, suggesting a new role for APOA2 in regulating dietary intake.

Triglycerides are increasingly being recognized as a risk factor for cardiovascular disease. Research efforts to identify sources of variability in triglyceride-lowering response to the lipid-lowering drug fenofibrate require quantification of the active acidic form of this PPAR-alpha agonist. Anion-exchange solid-phase extraction, in combination with reverse-phase high-performance liquid chromatography (HPLC), rapidly and accurately determines steady-state fenofibric acid serum concentrations. Chromatographic separation under isocratic conditions, with use of ultraviolet detection at 285 nm, provides clean baseline and sharp peaks for clofibric acid, 1-napthyl acetic acid (internal standards), and fenofibric acid. Commonly prescribed and over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) were screened for assay interference, and the assay was employed to quantify fenofibric acid in more than 800 human subject specimens. Fenofibric acid analysis was found to be linear over the range of 0.5 to 40 mg/L and was validated with either internal standard. Accuracies ranged from 98.65% to 102.4%, whereas the within- and between-day precisions ranged from 1.0% to 2.2% and 2.0% to 6.2%, respectively. NSAIDs had minimal interference with the assay, which succeeded in quantifying fenofibric acid in more than 843 of 846 serum samples from human subjects, many taking a variety of coadministered medications. Anion-exchange solid-phase extraction in combination with reverse-phase HPLC accurately determines steady-state fenofibric acid serum concentrations in humans without interference from NSAIDs or commonly administered medications. This method is suitable for quantification of fenofibric acid for clinical pharmacokinetic studies in patients with dyslipidemia.

Mixture models are applied in population pharmacometrics to characterize underlying population distributions that are not adequately approximated by a single normal or lognormal distribution. In addition to obtaining individualized maximum a posteriori Bayesian post hoc parameter estimates, the subpopulation to which an individual was classified can be determined. However, the accuracy of the classification of subjects to subpopulations is not well studied. We investigated the impact of several factors on the accuracy of classification in mixture models applied to pharmacokinetics using a simulation strategy. The availability of actual subject data allowed us to evaluate mixture model classification in a potentially common application, namely, the classification of clearance into poor metabolizer (PM) or extensive metabolizer (EM) subgroups with the known phenotype status in subjects receiving metoprolol. The factors explored in the simulation study were the magnitude of difference between the clearances in two subpopulations, the between subject variability in clearance, the mixing-fraction, and the population sample size. Populations were simulated at various levels of the above factors and analyzed with a mixture model using NONMEM. The population pharmacokinetics of metoprolol were modeled with the EM/PM phenotype as a known covariate, and without the phenotype covariate using a mixture model. Within the range of scenarios studied, the proportion of subjects classified into the correct subpopulation was high. The simulation-estimation study suggests that a greater separation between two subpopulations, a smaller variability in the parameter distribution, a larger sample size, and a smaller size subpopulation tend to be associated with a greater accuracy of subpopulation classification when a mixture model is applied to pharmacokinetic data. In a population pharmacokinetic analysis of metoprolol, a drug that undergoes polymorphic metabolism, it was possible to correctly identify phenotype status using a mixture model.

Southeast Asians known as the Hmong have a high prevalence of tuberculosis and select cancers. The slow acetylation (SA) phenotype for N-acetyltransferase 2 (NAT2) has been associated with toxicity from the anti-tuberculosis drug, isoniazid and in increased risk of select cancers. Previous research indicates a 74.5% prevalence of SA in Hmong which differs from other Asian populations including the Japanese and Thai (range: 7%-45%). Given this contrast, the purpose of this study was to confirm or refute this unexpected predominance of the SA phenotype in Hmong. Unrelated, Minnesota Hmong between 18 and 65 years of age consented and participated by ingesting caffeine as the probe for NAT2. A urinary caffeine metabolic ratio AFMU/1X (<0.6) was used to classify subjects as slow acetylators. Among 51 analysable samples provided by 61 enrollees (27 male, 33 female, 1 sex unknown, age 30+/-11 years [mean+/-SD]) there were 47 (92.2%) slow and 4 (7.8%) rapid acetylators. The prevalence of the SA phenotype (92.2%) from this study exceeds the 74.5% (p<0.02 by chi-square test) previously noted in Minnesota Hmong (n=98). The predominance of the SA phenotype within Minnesota Hmong is confirmed. Further studies evaluating this unexpected prevalence, its genetic basis and potential clinical relevance to drug toxicity and disease are warranted., (Copyright 2006 John Wiley & Sons, Ltd.)

Despite wide use of the influenza vaccine, relatively little is known about its effect on the measurement of inflammatory markers. Because inflammatory markers such as C-reactive protein (CRP) are increasingly being used in conjunction with lipids for the clinical assessment of cardiovascular disease and in epidemiologic studies, we evaluated the effect of influenza vaccination on markers of inflammation and plasma lipid concentrations. We drew blood from 22 healthy individuals 1 to 6 hours before they were given an influenza vaccination and 1, 3, and 7 days after the vaccination. Plasma CRP, interleukin (IL)-6, monocyte chemotactic protein 1, tumor necrosis factor alpha, IL-2 soluble receptor alpha, and serum amyloid A were measured, and differences in mean concentrations of absolute and normalized values on days 1, 3, and 7 were compared with mean baseline values. There was a significant increase in mean IL-6 (P < .01 absolute values, P < .001 normalized values) on day 1 after receiving the influenza vaccine. The mean increases in normalized high sensitivity CRP values were significant on day 1 (P < .01) and day 3 (P = .05), whereas the mean increase in normalized serum amyloid A was significant only on day 1 (P < .05). No significant changes were seen in mean concentrations of IL-2 soluble receptor alpha, monocyte chemotactic protein-1, or tumor necrosis factor-alpha. Of the lipids, significant decreases in mean concentrations of normalized triglyceride values were seen on days 1 (P < .05), 3 (P < .001), and 7 (P < .05) after vaccination. Our findings show that the influenza vaccination causes transient changes in select markers of inflammation and lipids. Consequently, clinical and epidemiologic interpretation of the biomarkers affected should take into account the possible effects of influenza vaccination.

Study Objectives: To objectively compare the results of a collaborative approach using pharmacists with the results of usual care for achieving a low-density lipoprotein cholesterol (LDL) goal of 100 mg/dl or less in outpatients with documented coronary heart disease (CHD) who are not at goal, and to document the effect on LDL after removal of such a collaborative model from the study population., Design: Prospective, multiclinic, controlled study., Setting: Four clinics of a 19-clinic staff model health maintenance organization in Minneapolis and St. Paul, Minnesota. Two clinics treated the intervention patients, two the controls; one clinic for each group was suburban, and one for each was urban., Patients: Four hundred eighty-one patients aged 18 years or older with CHD and whose LDL levels were not at goal., Intervention: Clinical pharmacists implemented the physician-approved care plan for each intervention patient; activities included managing lipid-lowering drug therapy and educating patients on cardiovascular risk reduction., Measurements and Main Results: Primary outcomes were changes in LDL level and the proportion of patients achieving goal LDL in the intervention versus the usual care (control) group. Secondary outcomes were the sustainability of the impact observed up to 18 months after discontinuation of the intervention. Mean+/-SD baseline LDL levels were 131+/-28 and 131+/-26 mg/dl (p=NS) for the intervention and control groups, respectively. After a mean of 6.5 months follow-up, 107 (72%) patients in the intervention group and 61 (18%) patients in the control group had attained their LDL goal (p<0.001). Mean LDL levels were reduced by 35.6 mg/dl (27.5%) and 6.7 mg/dl (4.6%) in the intervention and control groups, respectively (p<0.001). When the active program was discontinued, results of the 18-month follow-up indicated that 85 (65%) intervention patients remained at goal compared with 96 (42%) controls (p<0.001)., Conclusion: This trial provides quantitative evidence to support the effectiveness of the collaborative approach as an intervention to optimize management of patients with CHD whose LDL levels are not at goal; this approach is specifically called for in the executive summary of the National Cholesterol Education Program Adult Treatment Panel III. Furthermore, this study documents both the magnitude and sustainability of the impact collaborative care models can have in managed care environments.

To determine the extent of achievement of goal low-density lipoprotein cholesterol (LDL) as defined by National Cholesterol Education Program-Adult Treatment Panel II (NCEP-ATP 11) and American Diabetes Association (ADA) 2000 guidelines, we conducted a retrospective study by integrating data from medical, laboratory, and pharmacy claims databases. Subjects were selected from a 232,000-member staff-model managed care organization consisting of 19 clinics in the Minneapolis-St. Paul, Minnesota, metropolitan area. A total of 124,971 members aged 18 years and older, who had been continuously enrolled from July 1, 1996-June 6, 1998, were included. Outcome measures were the extent of achievement of goal LDL as defined by NCEP-ATP II and the use of antihyperlipidemic drugs for patients with and without diabetes at various levels of risk for coronary heart disease (CHD). Of 124,971 subjects, 6538 had a history of CHD, 1523 of whom met their LDL goal. Of the population with CHD who did not achieve goal, 1141 (43%) missed by over 30 mg/dl; 621 (54%) of these patients were not receiving drug therapy A total of 17,267 had no history of CHD but had two or more risk factors; 3,298 of these achieved their LDL goal. Of those who did not achieve goal, 1,136 (35%) missed by over 30 mg/dl; 897 (79%) of these were not receiving drug therapy A total of 6,586 had a history of diabetes; 1,004 and 2,340 reached an LDL of 100 mg/dl or lower and less than 130 mg/dl, respectively Of those with diabetes who had an LDL greater than 100 mg/dl, 1,276 (49%) missed their goal by over 30 mg/dl; 898 (70%) of these were not receiving drug therapy. Inadequate use of pharmacologic agents plays a significant role in failure to achieve goal LDL for patients with CHD, without CHD, and with diabetes. Analysis of the data based on the new ADA guidelines for LDL demonstrates the need for continued vigilance. Finally, the successful merging of medical, laboratory, and pharmacy claims databases provides a benchmark for other institutions.

Study Objective: To evaluate the metabolism of antipyrine, a general metabolic probe, caffeine, a probe for cytochrome P450 (CYP) 1A2 and N-acetyltransferase activity, and dextromethorphan, a specific probe for CYP2D6 activity in patients with type 1 or 2 diabetes mellitus., Design: Prospective, controlled study., Setting: Research facility. Patients. Fifteen patients with type 1 and 16 with type 2 diabetes, and 16 healthy controls., Intervention: Each subject simultaneously received antipyrine 10 mg/kg, caffeine 100 mg, and dextromethorphan 30 mg., Measurements and Main Results: The pharmacokinetics of antipyrine and its primary metabolites were determined from saliva and urine samples. Type 1 diabetes had marked effects on antipyrine metabolism whereas type 2 disease did not alter the metabolism of any of the probe drugs. The apparent oral clearance of antipyrine was increased 72% in patients with type 1 disease compared with controls (p=0.0001). In addition, formation clearances of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine were increased by 74% and 137% in those patients relative to controls. The caffeine metabolic index (paraxanthine/caffeine) was increased 34% (p=0.11), and N-acetylation and CYP2D6 phenotype were not altered., Conclusion: The metabolism of antipyrine is increased in patients with type 1 diabetes. Based on in vitro reports of antipyrine metabolism and current caffeine metabolic index data, the predominant effect of type 1 diabetes appears to be an increase in CYP1A2 activity. Assessment of the effect of the disease on other specific CYP metabolic pathways is warranted.

Study Objective: To assess the accuracy of patient-kept diaries relative to electronic monitoring of compliance with isosorbide dinitrate prescribed 3 times/day for ischemic heart disease., Design: Unblinded, prospective, three-phase study., Methods: Patients with coronary artery disease prescribed isosorbide dinitrate 3 times/day were asked to record the time of administration of each dose in a pocket diary while being monitored for compliance with a computerized Medication-Event Monitoring System (MEMS-4) vial that electronically recorded the date and time the vial was opened., Results: Sixty-eight stable outpatients with documented coronary artery disease who were prescribed isosorbide dinitrate 3 times/day were evaluated. Based on a prospectively chosen definition including a nitrate-free period, the mean (+/-SD) overall compliance rates were 71% (+/-30) versus 55% (+/-32) for the patient-kept diaries and the MEMS vials respectively (p = 0.001). The concordance between patient-kept diaries and MEMS data indicate that 67% of patients overestimate their compliance when using a self-recording tool. An average of 30% of diary entries were in error compared with the MEMS vial recordings., Conclusions: Patient-kept diaries statistically overestimate actual compliance relative to that determined by MEMS devices. Given the prevalence of the use of diaries as the predominant tool on which researchers depend to document compliance with study drugs, our findings suggest that this practice should be reevaluated specifically when the time of the dose and documentation of administration are critical to qualifying the outcome of drug therapy. Such is the case with isosorbide dinitrate use in patients with ischemic heart disease. Furthermore, the overall poor compliance documented in this study suggests that the utility of isosorbide dinitrate prescribed 3 times/day be reevaluated as a clinically effective antianginal drug.

Recognition of the existence of circadian variation in exacerbation of cardiovascular disease may have relevance to clinical use of cardioactive agents. Physiologic rational for the chronobiology of cardiac disease exists and can provide a basis on which to examine the efficacy of agents to manage cardiac disease. The use of 24-hour ambulatory blood pressure monitoring (ABPM) devices have advanced our ability to describe the interplay of chronobiologic rhythms and pharmacodynamic response to antihypertensive medications. This review summarizes the studies evaluating the use of various antihypertensive medications in the context of using 24-hour blood pressure monitoring devices. The studies are described in an attempt to increase awareness of chronobiology and potential implications of designing chronotherapeutic regimens.

Pharmacogenetics can be an important determinant of pharmacologic response. To learn more about interpopulation differences in drug metabolism between ethnically diverse populations of subjects cared for by an International Clinic, a study was conducted to describe the prevalence of fast or slow acetylators of N-acetyltransferase (NAT2) in a population of Hmong residing in Minnesota. Ninety-eight healthy Hmong refugees from Laos volunteered to take caffeine as an oral probe drug to establish acetylator phenotype. Participants were classified as either rapid or slow acetylators based on the urinary molar ratio of select metabolites of caffeine. Assignment of phenotype was based on results from analysis of urine collected subsequent to ingestion of caffeine. The ratio of 5-acetylamino-6-formylamino-3-methyluracil (AFMU) to the combined products of the 7-demethylation pathway of paraxanthine (AFMU, 1-methylxanthine (1X), and 1-methylurate (1U)] formed the basis for this determination. A probit plot of the data collected in our subjects qualified a metabolic ratio of 0.34 as an acceptable cut point for phenotype assignment. Participants with an AFMU/(AFMU + 1X + 1U) ratio of < 0.34 were classified as slow acetylators and all others as rapid acetylators. Analysis of the data suggested a bimodal distribution with an excess (74.5%) of slow acetylators in the population. The predominance of slow acetylators found in the Hmong contrast with the prevalence of slow acetylators seen in other ethnic groups. These findings may have important clinical implications given the large number of Hmong treated each year in our International Clinic and the increasing use of medications metabolized by NAT2 in this population.

Isosorbide dinitrate is one of the most commonly prescribed medications for the treatment of ischemic heart disease. It has been demonstrated to be ineffective relative to placebo when taken inappropriately. This study objectively documents the magnitude and nature of compliance in 68 ambulatory patients who were prescribed isosorbide dinitrate three times a day. Each patient received a 9-week supply of medication in a vial equipped with a computerized monitor (MEMS-4 cap; APREX Corporation, Fremont, CA) and were informed as to the purpose of the study. Of the patients, 74% were classified into the low and 16% into the high compliance category, defined as compliant < 70% and > or = 85% of study days, respectively. The mean (+/- SD) percent days in which isosorbide dinitrate was taken three times was 66% (+/- 29), and the mean number of days in which it was taken three times with a 10-hour "nitrate free period" was 53% (+/- 31). It is concluded that the magnitude of noncompliance in patients prescribed isosorbide dinitrate three times daily is substantial (74%). The nature of this noncompliance is often due to failure to observe a 10- to 12-hour nitrate free period. Given the need to take isosorbide dinitrate appropriately and given the demonstrated magnitude of noncompliance, physicians should take these factors into consideration when selecting this agent for the management of coronary artery disease relative to other pharmacologic options.

Intravenous erythromycin has recently been associated with significant QTc interval prolongation, torsades de pointes, and sudden cardiac death. The prolonged the QTc interval attributed to erythromycin typically is associated with rapid infusion rates in excess of 10 mg/minute. We prospectively assessed the relationship between QTc interval prolongation and erythromycin administration by slow intravenous infusion (mean rate 8.9 +/- 3.5 mg/minute, range 3.9-16.7 mg/minute). Electrocardiographic (ECG) rhythm strips were prospectively obtained in 44 critically ill patients receiving intravenous antibiotics (22 received erythromycin and 22 ceftazidime, cefuroxime, cefotaxime, ceftriaxone, or ampicillin-sulbactam as controls). The ECG recordings were obtained immediately before and within 15 minutes after drug infusions. Only the first available set of ECG strips were evaluated. Two controls had evidence of hepatic dysfunction; no patients receiving erythromycin did. The QTc interval was calculated using Bazett's formula by two blinded investigators. For controls, mean +/- 1 SD (range) QTc intervals were 423 +/- 96 (300-550) msec at baseline and 419 +/- 96 (280-610) msec after infusion (p = 0.712). In contrast, in the erythromycin group, the interval was significantly prolonged from 524 +/- 105 (360-810) msec at baseline to 555 +/- 134 (400-980) msec after infusion (p = 0.034). No patients experienced a dysrhythmia as a consequence of erythromycin infusion. Despite slow rates of infusion, QTc interval prolongation was significant. The clinical importance of this finding remains to be determined.

The overuse and cost of drugs in long-term care facilities are of significant concern. To quantify potential overuse of antihypertensive agents, we conducted a retrospective chart review in four long-term care facilities. We analyzed data in 550 patient records to identify residents receiving drugs for the sole indication of hypertension. Of the 550 records, 49 (9%) residents qualified. Of these, 20 (41%) had all recorded blood pressures less than 140/90 mm Hg for the 6 months before review, and 32 (65%) had all blood pressures less than 160/90 mm Hg. Given this degree of blood pressure control and the reported success of withdrawing antihypertensive drugs from the elderly in whom the disorder is well controlled, a reevaluation of antihypertensive therapy in residents of long-term care facilities appears to be justified.

Genetic polymorphism of the P450IID6 (CYP2D6) enzyme system can be an important component of the variability in response to drug therapy. Interpopulation differences in the prevalence of deficiencies of drug-metabolizing enzymes may be clinically important in the selection and dosage of drug therapies for patients. Since 1980, the State of Minnesota has had more than a 1000% increase in population of Hmong refugees from Laos. The Hmong are frequently treated in our institution's international clinic with virtually no systematically acquired knowledge about the ability of this relatively ethnically pure population to metabolize commonly used Western medications. To further our knowledge of drug metabolism in this population, we identified the prevalence of the poor metabolizer phenotype for CYP2D6 in a sample population of Hmong subjects and compared this prevalence to that in a sample population of white subjects. Urine collected after ingestion of dextromethorphan in 237 healthy Hmong and 280 healthy white volunteers was analyzed by HPLC. Based on probit plots of the metabolic ratios (dextro-methorphan/dextrorphan), 8.9% of Hmong subjects and 6.1% of white subjects were assigned the poor metabolizer phenotype (difference not significant). Weak associations were found between body surface area and metabolic ratio for both Hmong and white men and between smoking status and metabolic ratio for white subjects only. We conclude that the prevalence of poor metabolizers for the CYP2D6 enzyme system is similar between Hmong subjects and white subjects residing in Minnesota and that an antimode of 0.3 for metabolic ratio appears to be reasonable for the populations studied.

A high-performance liquid chromatography (HPLC) assay for the simultaneous quantitation of dextromethorphan and its O-demethylated metabolite dextrorphan from urine is described. A cyano analytical column was used with a mobile phase consisting of MeOH 16%, acetonitrile 3%, and triethylamine 0.06% at pH 2.8 and a flow rate of 1.0 ml/min. Betaxolol was used as the internal standard. Standard curves from 50 ng/ml to 10,000 ng/ml (dextrorphan), and from 50 ng/ml to 8,000 ng/ml (dextromethorphan) were developed. The peaks eluted at 7.8 min (dextrorphan), 12.2 min (betaxolol), and 17.8 min (dextromethorphan). The coefficients of variance ranged from 1.3 to 4.5% at 250 ng/ml and 0.9 to 2.5% at 5,000 ng/ml. This assay was used to determine dextromethorphan/dextrorphan molar ratios in healthy male volunteers for the purpose of determining phenotype status for the P450IID6 isozyme.

Debrisoquine is an antihypertensive drug that displays polymorphic metabolism and has been used to determine hydroxylator status in human subjects. A high-performance liquid chromatographic method for the simultaneous urine analysis of debrisoquine (D) and its primary metabolite, 4-hydroxydebrisoquine (4-OHD), is described. A cyanopropyl (CN) extraction column and CN analytical column were used with a mobile phase consisting of 20% acetonitrile/20 mM sodium dihydrogen orthophosphate (pH = 7.1) at a flow rate of 1.5 ml/min. The peaks of interest, as well as the internal standard, were eluted from the column in less than 14 min. The method described was validated for within-day and between-day accuracy and precision for both D and 4-OHD. Coefficients of variation at all concentrations tested were less than 4.1% for D and less than 9.3% for 4-OHD. The assay was used to evaluate D/4-OHD ratios, thereby determining hydroxylation status in 65 healthy male volunteers.

Metoprolol is a lipophilic, cardioselective beta-adrenergic blocking agent commercially available as a racemic compound. A normal phase high-performance liquid chromatographic method was developed to directly determine individual enantiomeric concentrations of metoprolol in human serum. Separation of the enantiomers was accomplished by a cellulose-tris(3,5-dimethylphenylcarbamate) chiral stationary phase. Metoprolol enantiomers were detected by means of fluorescence with excitation and emission wavelengths of 275 and 315 nm, respectively. Standard curves were linear over the concentration range 12.5-400 ng/ml for each enantiomer. Within-day coefficient of variation was less than 15% at all concentrations and the between-day coefficient of variation ranged from 4.1 to 11.2%. The limit of detection was determined to be 5 ng/ml for each enantiomer and the stereoselective resolution (alpha) of R- and S-metoprolol was 3.08. The assay was employed to determine enantiomeric serum concentrations of metoprolol in healthy male volunteers.

After multiple oral doses, propranolol has been reported to accumulate to a greater degree than expected based on its terminal elimination rate constant and dosage interval. To determine whether the decrease in presystemic elimination can be attributed solely to a decrease in unbound intrinsic clearance or possibly a decrease in unbound fraction, we studied the pharmacokinetics of unbound propranolol in nine healthy subjects who were given 160 mg of regular or sustained-release propranolol orally as single doses, and once daily for 7 d. Unbound propranolol concentrations were calculated by HPLC and equilibrium dialysis on each serum sample. With regular propranolol, the mean unbound oral clearance (CLoral) decreased 29%, from 503 +/- 281 after a single dose to 359 +/- 143 mL/min/kg at steady state (p less than 0.05). Similarly, CLoral decreased 33% with sustained-release propranolol from 1077 +/- 514 to 721 +/- 385 mL/min/kg (NS). The corresponding accumulation ratios for regular and sustained-release propranolol were 1.39 +/- 0.49 and 1.61 +/- 0.81, respectively (NS). Therefore, the mean bioavailability of sustained-release relative to that of regular propranolol was 0.52 +/- 0.23 and 0.54 +/- 0.17 for single doses and at steady-state, respectively. The percent unbound of propranolol ranged from 6.8 to 14.0 with an average of 10.1. Neither the percent unbound nor alpha 1-acid glycoprotein (AAG) serum concentrations were statistically different between single and multiple doses. The binding ratio was significantly correlated to AAG concentration (r = 0.776, p less than 0.05). The data support a decrease in unbound intrinsic clearance of propranolol with no change in unbound fraction, leading to an increase in bioavailability at steady state.

We analyzed 99 patients' serum samples for concentrations of a new antiarrhythmic agent, flecainide acetate, by fluorescence polarization immunoassay (FPIA) and "high-performance" liquid chromatography (HPLC). Within-day and between-day coefficients of variation at concentrations in the low and high ends of the therapeutic range were less than 7% for HPLC and less than 9% for FPIA. There was no statistical difference in the mean (+/- SD) concentrations of the clinical serum samples measured by the two methods (607 +/- 334 micrograms/L by HPLC, 602 +/- 344 micrograms/L by FPIA), but results by each differed by a mean of 0.13%. FPIA and HPLC measurements correlated significantly (r = 0.98, P less than 0.05), and were linearly related (slope = 0.970, intercept = 13 micrograms/L) as assessed by orthogonal regression. Both assay methods produced similar concentration measurements and were sufficiently accurate and precise to be used in therapeutic drug monitoring.