Search

Objective: apoA1 (apolipoprotein A-1) is the main lipoprotein associated with HDL (high-density lipoprotein) cholesterol. It was recently reported that intravenous infusion of apoA1 could lower insulin resistance in pregnant rats, leading to the suggestion that apoA1 could provide a target for reducing pregnancy-induced insulin resistance and the risk of gestational diabetes mellitus (GDM) in humans. However, the effects of apoA1 on insulin resistance and risk of GDM in human pregnancy are not known. Thus, we sought to systematically evaluate the relationships of apoA1 with glucose homeostasis and metabolic function in pregnant women. Approach and Results: In this study, 870 pregnant women were recruited in late second trimester and underwent metabolic characterization, including an oral glucose tolerance test on which 214 were diagnosed with GDM. Metabolic characterization included assessment of glucose tolerance, insulin sensitivity/resistance (Matsuda index, homeostasis model assessment of insulin resistance), pancreatic β-cell function, lipids (LDL [low-density lipoprotein] cholesterol, HDL cholesterol, triglycerides, apoB [apolipoprotein B], and apoA1), CRP (C-reactive protein), and adiponectin. Serum apoA1 was strongly correlated with HDL (r=0.79, P P =0.0004) but showed no association with measures of insulin sensitivity/resistance, β-cell function, glycemia, or CRP. There were no significant differences across apoA1 tertiles in mean adjusted Matsuda index ( P =0.24), homeostasis model assessment of insulin resistance ( P =0.08), or area under the glucose curve on the oral glucose tolerance test ( P =0.96). Moreover, there were no differences in risk of GDM across tertiles of apoA1, both before ( P =0.67) and after covariate adjustment ( P =0.78). Conclusions: Serum apoA1 is not associated with insulin resistance or the risk of GDM in human pregnancy.

Introduction: Identifying dietary interventions for cardiometabolic disease prevention in individuals with metabolic syndrome is relevant to a significant portion of the population. Numerous studies have investigated the effects of canola oil on cardiovascular disease risk; however, no studies have compared canola oil diets to a control diet with a fatty acid composition characteristic of Western intakes in individuals with metabolic syndrome risk factors. The objectives of this study were to evaluate effects of canola oil, high-oleic acid canola oil (HOCO), and a control oil (blend of butter, safflower, coconut, and flaxseed oils formulated to represent a Western diet fatty acid profile) on lipids, lipoproteins, and apolipoproteins. Hypothesis: We tested the hypothesis that the two canola oil diets would elicit beneficial effects on the total lipid/lipoprotein profile compared to the Western (control oil) diet. Methods: In a multi-center, double blind, randomized, three-period crossover, controlled feeding clinical trial, 119 individuals with an increased waist circumference plus at least one additional metabolic syndrome risk factor consumed prepared isocaloric, weight maintenance diets containing canola oil [17.5% E from monounsaturated fatty acids (MUFA), 9.2% polyunsaturated fatty acids (PUFA), 6.6% saturated fatty acids (SFA)], HOCO (19.1% E from MUFA, 7.0% PUFA, 6.4% SFA), or control oil (11% E from MUFA, 10% PUFA, 12% SFA) for six-weeks each separated by 4-12 week washouts. The differences at the end of 42 days of feeding were tested. Results: The canola oil and HOCO resulted in lower endpoint total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), the TC: high-density lipoprotein-cholesterol (HDL-C) ratio, apolipoprotein (apo) B, the apoB: apoA1 ratio, and non-HDL-C compared to control oil ( P P = 0.0462). There were no differences among the three diets in endpoint triglycerides or HDL-C. Conclusions: Incorporating canola or high-oleic acid canola oils into the diet improves blood lipids and lipoproteins compared to a contemporary Western diet in individuals with at least two criteria for metabolic syndrome.

Background— Homeless people represent an extremely disadvantaged group in North America. Among older homeless men, cardiovascular disease (CVD) is the leading cause of death. The objective of this study was to examine cardiovascular risk factors in a representative sample of homeless adults and identify opportunities for improved risk factor modification. Methods and Results— Homeless persons were randomly selected at shelters for single adults in Toronto. Response rate was 79%. Participants (n=202) underwent interviews, physical measurements, and blood sampling. The mean age of participants was 42 years, and 89% were men. The prevalence of smoking among homeless subjects (78%; 95% confidence interval [CI], 72% to 84%) was significantly higher than in the general population (standardized morbidity ratio [SMR], 254; 95% CI, 216 to 297). Hypertension, high cholesterol, and diabetes were not more prevalent than in the general population but were often poorly controlled. Homeless men were significantly less likely to be overweight or obese than men in the general population (SMR, 79; 95% CI, 63 to 98). Cocaine use in the last year was reported by 29% of subjects (95% CI, 23% to 36%). CVD was reported by 15% of subjects, fewer than one third of whom reported taking aspirin or cholesterol-lowering medication. According to multiple-risk-factor equations, the median estimated 10-year absolute risk of myocardial infarction or coronary death among homeless men aged 30 to 74 years was 5% (interquartile range, 3% to 9%). Conclusions— Cardiovascular risk factor modification is suboptimal among homeless adults in Toronto, despite universal health insurance. Multiple risk factor equations may underestimate true risk in this population because of inadequate accounting for factors such as cocaine use and heavy smoking.

Adiponectin is arguably the adipokine most specifically expressed in white adipose tissue. It was described in 1995 as Acrp30, AdipoQ, apM1, and GBP28. The x-ray crystallographic observation in 1998 that there was structural homology to complement C1q and tumor necrosis factor should have been a clue that this would be a complex beast.1 Adding further to the complexity, adiponectin monomers are assembled into multimers that can be separated by size into 3 broad groups. The largest high-molecular weight adiponectin has been shown to be protease resistant, which became the basis for a selective immunoassay.2 The complexity of adiponectin structure—with both covalent and noncovalent interactions stabilizing the multimers—adds further challenges to quantification for patient–based studies. Indeed, not all assays have been found to give agreement. In the absence of a gold standard, we require stability from suppliers of assays and carefully characterized cohorts to establish biovalidation. See accompanying article on page 2259 Advances require that not all evidence be accrued in human or patient–based studies. Adiponectin has proven a challenge, as while it is found in species such as mice, there are major species-specific differences in tissue expression patterns3 (Biogps GeneAtlas …

Objective—The aim of this study was to investigate the influence of interferon-γ (IFN-γ) on atherosclerosis in low density lipoprotein receptor (LDLR)–null mice.Methods and Results—We cross-bred IFN-γ–deficient mice with LDLR-null mice and analyzed lipoprotein profiles and atherosclerosis in the compound mutant progeny after 8 and 20 weeks on a cholesterol-enriched diet. IFN-γ deficiency did not affect serum cholesterol levels or lipoprotein profiles, but it did affect the extent and phenotype of atherosclerosis. Atherosclerotic lesions in IFN-γ–deficient mice were reduced by 75% in the aortic arch and by 46% in the descending aorta compared with control mice after 8 weeks on the diet. After 20 weeks, arch lesions were reduced by 43%, and descending aorta lesions were reduced by 65% in IFN-γ–deficient mice compared with controls. At 8 weeks, percent lesional macrophage and smooth muscle content was significantly less in the IFN-γ–deficient mice, but not at 20 weeks. Although there were fewer class II major histocompatibility complex–positive cells in the lesions of IFN-γ–deficient animals compared with controls, class II major histocompatibility complex expression on endothelial cells overlying lesions persisted in the absence of IFN-γ.Conclusions—These data provide direct evidence that IFN-γ influences atherosclerosis development and phenotype in the LDLR-deficient mouse, independent of changes in blood lipoprotein profiles.

Background—The influence of complement activation on atherosclerosis is not well understood. The purpose of this study was to examine the effects of C3 deficiency on the extent and phenotype of atherosclerosis.Methods and Results—Aortic atherosclerosis was analyzed in low-density lipoprotein receptor (ldlr)/C3-deficient mice (ldlr−/−C3−/−) andldlr−/−C3+/−littermate control mice after 15 weeks on a 1.25% (wt/wt) cholesterol diet. Serum lipoprotein profiles and immunoglobulin levels were not significantly different between the 2 experimental groups. The lipid-positive en face lesional area in thoracic and abdominal aorta was greater in C3-deficient mice than in control mice (3.9% versus 2.1%, median,P=0.0076). Similarly,the lipid-positive area in aortic arch sections was greater in C3-deficient mice than in controls (0.04 mm2versus 0.02 mm2, median,P=0.0089). Analysis of aortic arch sections showed greater lesional macrophage content in C3-deficient versus control mice (8.24±1.36% versus 5.9±1.63% intimal area, mean±SEM,P=0.003), less smooth muscle cell content in C3-deficient versus control mice (0.06±0.05% versus 0.92±0.32% intimal area, mean±SEM,PP=0.008).Conclusions—The maturation of atherosclerotic lesions beyond the foam cell stage is strongly dependent on an intact complement system.

Abstract —Past studies of atherosclerosis in mice have used chow-based diets supplemented with cholesterol, lipid, and sodium cholate to overcome species resistance to lesion formation. Similar diets have been routinely used in studies with LDL receptor–deficient (LDLR −/− ) mice. The nonphysiological nature and potential toxicity of cholate-containing diets have led to speculation that atherogenesis in these mice may not accurately reflect the human disease process. We have designed a semipurified AIN-76A–based diet that can be fed in powdered, pelleted, or liquid form and manipulated for the precise evaluation of diet–genetic interactions in murine atherosclerosis. LDLR −/− mice were randomly assigned among 4 diets (n=6/diet) as follows: 1, control, 10% kcal lipid; 2, high fat (40% kcal), moderate cholesterol (0.5% by weight); 3, high fat, high cholesterol (1.25% by weight); and 4, high fat, high cholesterol, and 0.5% (wt/wt) sodium cholate. Fasting serum cholesterol was increased in all cholesterol-supplemented mice compared with controls after 6 or 12 weeks of feeding ( P P −/− mice and that precisely defined semipurified diets are a valuable tool for the examination of diet–gene interactions.

Abstract —Although naturally occurring loss-of-function mutations in human hepatic lipase ( HL ) have been described, the biochemical phenotype of heterozygous HL deficiency remains ill defined. This may be due to the relatively small numbers of heterozygous adult carriers of HL mutations in index kindreds. We have identified several new heterozygotes for the catalytically inactive, nonsecreted HL variant S267F in the kindred that was originally ascertained because of hypertriglyceridemia due to the mutant, secreted, circulating apolipoprotein (apo) CII variant apo CII-T. Pairwise comparisons with family controls showed that only the plasma low density lipoprotein triglycerides (LDL TGs) were higher in 11 simple heterozygotes for HL S267F ( P =0.002). In contrast, both plasma total TGs and LDL TGs were significantly higher in 12 simple heterozygotes for apo CII-T than in family-matched control subjects ( P =0.005 and 0.009, respectively). These findings suggest that the TG content of LDL is increased by heterozygosity for 2 different mutations that affect different proteins involved in lipolysis. However, the mechanisms underlying this compositional change in LDL appear to be different for the 2 mutations, because the total TGs are also elevated in subjects heterozygous for apo CII-T but not in subjects heterozygous for HL S267F.

Abstract We hypothesized that common genomic variation that affected the expression and/or function of the products of the APOC3 , APOE , FABP2 , and PON1 genes would be associated with variation in biochemical phenotypes in a previously unstudied human sample. We determined genotypes of functional genomic variants of APOC3 , APOE , FABP2 , and PON1 in 509 adult aboriginal Canadians from an isolated community in Northern Ontario. We tested for genotype associations with plasma lipoprotein traits. We found that (1) common variation at nucleotide −455 of the APOC3 promoter was associated with variation in plasma triglycerides ( P =.006) and (2) common variation of APOE determining plasma isoforms of apo E was associated with variation in plasma apo B ( P =.009). Analysis of subjects classed by APOC3 markers showed that homozygosity for presence of a C at nucleotide −455 and a T at nucleotide −482 was associated with significantly increased plasma triglycerides in both men and women. Furthermore, this allele was approximately twice as frequent in subjects within the highest quartile of plasma triglycerides as in subjects within the lowest quartile. Since the DNA variation detected by the APOC3 markers affects in vitro expression of the gene product, it is possible that the marker itself caused the associations. However, the associations could also have resulted from linkage disequilibrium with other functional variants in APOC3 or the closely linked APOA1 and/or APOA4 genes.

Abstract Cross-sectional and prospective studies have shown that individuals with high plasma lipoprotein(a) [Lp(a)] concentrations are at increased risk for coronary heart disease. Size polymorphism of the apolipoprotein(a) [apo(a)] glycoprotein accounts for ≈35% of the variation in plasma Lp(a) concentrations. However, there is no convincing evidence for associations between plasma Lp(a) and common genetic variation outside APO(a) , the gene that encodes apo(a). We tested for association of common genetic variation of candidate genes in lipid metabolism and also of F7 with variation of plasma Lp(a) concentrations in Alberta Hutterites. Variation at codon 353 of F7 has been associated with variation in the plasma factor VII activity (FVIIc), with the 353Q allele associated with lower FVIIc and the 353R allele associated with higher FVIIc. We found significant associations between variation in plasma concentrations of Lp(a) and both apo(a) isoform size and F7 codon 353 genotype (both P F7 353Q and 353R alleles were, respectively, to decrease by 1.71 μg/mL and to increase by 0.301 μg/mL plasma Lp(a) concentration from the sample mean. This suggests that common genomic variation in F7 is associated with variation in plasma Lp(a) concentration.

Human serum paraoxonase is located on an HDL. It has the capacity to retard the accumulation of lipid peroxides in LDL under oxidizing conditions in vitro. Paraoxonase has a genetic polymorphism that results in a single amino acid substitution. Evidence indicates that both the serum concentration of paraoxonase and an individual's genotype are related to plasma lipid and lipoprotein concentrations, and possibly also to coronary heart disease, implicating paraoxonase in the development of atherosclerosis.

Abstract We previously found an association between blood pressure and genetic variation of angiotensinogen in Canadian Hutterites. We hypothesized that variation in other candidate genes would also be associated with variation in blood pressure. We included genotypes of 12 candidate genes, along with clinical features and biochemical variables as covariates in an association analysis. We found that sex and body mass were significantly associated with variation in both systolic and diastolic blood pressures. We found that genotypes of APOB codon 4154 and AGT codon 174 were significantly associated with variation in systolic blood pressure. We found that genotypes of APOB codon 4154, AGT codon 174, and F7 codon 353 were significantly associated with variation in diastolic blood pressure. We found a significant association between age and variation in systolic but not diastolic blood pressure. We found a significant association between plasma apo B concentration and variation in diastolic but not systolic blood pressure. The association of genomic variation with resting blood pressure is consistent with the existence of important structural elements within or proximal to some genes in lipoprotein metabolism, the renin-angiotensin system, and the coagulation cascade. The association between plasma apo B concentration and diastolic blood pressure suggests that these traits may share some determinants.

Background Interindividual variation in fat deposition in swine is determined by loci on porcine chromosome 4, which are contained in a region that is syntenic with part of the long arm of human chromosome 1. We hypothesized that genomic variation of chromosome 1q would be associated with variation in the ratio of waist-to-hip circumference in male North American Hutterites, a genetic isolate characterized by significant relatedness and sharing of environmental factors. Methods and Results In 316 male Hutterites, we tested for phenotype-genotype association of two DNA polymorphisms on chromosome 1q and the ratio of waist-to-hip circumference. We included control loci on 10 other chromosomes in the multivariate model. We observed that DNA variation on chromosome 1q was significantly associated with variation in the ratio of waist-to-hip circumference in men ( P =.0029). Conclusions The association of DNA variation chromosome 1q with the ratio of waist-to-hip circumference in male Hutterites suggests that there are important structural elements in this genomic region that have a functional impact on body fat distribution.

Abstract The Hutterite Brethren are a genetic isolate characterized by high indices of relatedness and a communal agrarian lifestyle. We hypothesized that variation of the paraoxonase (PON) gene that underlies the interindividual variation in plasma PON activity would be associated with variation in fasting plasma lipoprotein variables in this group. In 793 Hutterites, we measured plasma lipids, lipoproteins, and apolipoproteins and analyzed DNA for genotypes of the protein polymorphism at amino acid residue 192 of PON. We observed that genotypes of PON were significantly associated with variation in plasma concentrations of total, HDL, non-HDL, and LDL cholesterol, total triglycerides, and apolipoprotein (apo) B. Homozygotes for the low-activity variant of PON had significantly lower levels of plasma apoB-related biochemical variables than heterozygotes and homozygotes for the high-activity variant of PON. Homozygotes for the low-activity variant of PON also had significantly lower ratios of total cholesterol/HDL cholesterol, LDL cholesterol/HDL cholesterol, and apoB/apoA-I than heterozygotes and homozygotes for the high-activity variant of PON. We found no evidence for a gene-gender interaction for any plasma lipoprotein variable. The PON polymorphism accounted for about 1% of the variation in total cholesterol and related lipoprotein traits in the Hutterites. These observations suggest that PON is a significant genetic determinant of plasma lipoprotein levels.

BACKGROUND The Hutterite Brethren are a genetic isolate characterized by high indices of relatedness and a communal agrarian lifestyle. We hypothesized that variation of the angiotensinogen (AGT) and angiotensin-converting enzyme (ACE) genes would be associated with variation in resting blood pressure in this group. We also hypothesized that the association would depend on the sex of the subjects. METHODS AND RESULTS In 741 Hutterites, we measured blood pressure in quadruplicate and analyzed DNA for genotypes of an insertion/deletion (I/D) polymorphism of ACE and of two protein polymorphisms of AGT, namely, M235T and T174M. We tested for association between variation in systolic and diastolic blood pressures and genotypic class. We observed that genotypes of AGT codon 174 were significantly associated with variation in systolic blood pressure. We also tested for an interaction between the AGT genotype and sex. We observed that genotypes of AGT codon 174 were significantly associated with variation in systolic blood pressure only in men. The AGT codon 174 polymorphism accounted for 3.1% of the total variation in systolic blood pressure in men. CONCLUSIONS The association of AGT variation with resting blood pressure in men is consistent with the existence of important structural elements within, flanking, or proximal to the AGT gene, whose functional impact might be related to differences in sex.

Hepatic lipase-deficient subjects in the Ontario kindred are compound heterozygotes for hepatic lipase mutations (Ser267-->Phe and Thr383-->Met). Cholesteryl ester-rich beta-very-low-density lipoprotein (beta-VLDL) accumulates in plasma and such subjects have premature atherosclerosis. To determine a possible mechanism, we hypothesized that hepatic lipase-deficient beta-VLDL, homozygous for apolipoprotein (apo) E3, would cause cholesteryl ester accumulation and foam cell formation in macrophages. beta-VLDL and pre-beta-VLDL were isolated by Pevikon electrophoresis and incubated with J774 macrophages, cells that do not secrete apoE. beta-VLDL increased cellular cholesteryl ester content 13-fold, whereas pre-beta-VLDL increased cholesteryl ester sevenfold. beta-VLDL increased acyl CoA:cholesterol acyltransferase activity fourfold (measured as [14C]oleate incorporation into cholesteryl ester). Preincubation of hepatic lipase-deficient beta-VLDL with the anti-apoE monoclonal antibody 1D7, which inhibits binding of apoE to low-density lipoprotein receptors, inhibited cellular cholesteryl ester accumulation by 75%, whereas the anti-apoB blocking monoclonal antibody 5E11 failed to inhibit cellular cholesteryl ester accumulation. In contrast to hepatic lipase deficiency, beta-VLDL from type III subjects (E2/E2) failed to increase cellular cholesteryl ester or acyl CoA:cholesterol acyltransferase more than 1.5-fold. Thus, hepatic lipase-deficient beta-VLDL readily induces cholesteryl ester accumulation in J774 macrophages, a process mediated by functional apoE3. This may explain the premature atherosclerosis observed in this kindred.

The genes for apolipoprotein (apo) C-II, a cofactor for activation of lipoprotein lipase, and apo E, a ligand for receptor-mediated uptake of triglyceride-rich lipoproteins, are physically linked on chromosome 19q13.1. In a large Caribbean Caucasian family, several individuals had clinical features of the complete absence of lipoprotein lipase activity and were homozygous for a DNA frameshift mutation of apo C-II, imparting functional inactivity to the mutant protein. Plasma from heterozygous carriers of this mutation, when compared with plasma from relatives who were noncarriers, had significantly diminished capacity to activate lipoprotein lipase in vitro. We also observed in heterozygotes for this mutation a wide range of serum lipid and lipoprotein levels. When age and sex were taken into account, the presence of a single apo E allele encoding the E4 isoform occurring in individuals with a single mutant apo C-II allele was strongly associated with higher levels of cholesterol, triglycerides, very low density lipoprotein cholesterol, and non-high density lipoprotein cholesterol when compared with those of relatives who carried neither or only one variant allele. This suggests that a single genetic mutation that usually has a recessive effect on lipoprotein metabolism can have an interactive effect on lipid phenotype when it is coinherited with a single mutation at another gene whose product affects the same metabolic pathway.