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Atherosclerotic plaques are characterized by an accumulation of macrophages, lipids, smooth muscle cells, and fibroblasts, and, in advanced stages, necrotic debris within the arterial walls. Dietary habits such as high fat and high cholesterol (HFHC) consumption are known risk factors for atherosclerosis. However, the key metabolic contributors to diet-induced atherosclerosis are far from established. Herein, we investigate the role of a 2-year HFHC diet challenge in the metabolic changes of development and progression of atherosclerosis. We used a non-human primate (NHP) model (baboons, n = 60) fed a HFHC diet for two years and compared metabolomic profiles in serum from animals on baseline chow with serum collected after the challenge diet using two-dimensional gas chromatography time-of-flight mass-spectrometry (2D GC-ToF-MS) for untargeted metabolomic analysis, to quantify metabolites that contribute to atherosclerotic lesion formation. Further, clinical biomarkers associated with atherosclerosis, lipoprotein measures, fat indices, and arterial plaque formation (lesions) were quantified. Using two chemical derivatization (i.e., silylation) approaches, we quantified 321 metabolites belonging to 66 different metabolic pathways, which revealed significantly different metabolic profiles of HFHC diet and chow diet fed baboon sera. We found heritability of two important metabolites, lactic acid and asparagine, in the context of diet-induced metabolic changes. In addition, abundance of cholesterol, lactic acid, and asparagine were sex-dependent. Finally, 35 metabolites correlated (R2, 0.068–0.271, P < 0.05) with total lesion burden assessed in three arteries (aortic arch, common iliac artery, and descending aorta) which could serve as potential biomarkers pending further validation. This study demonstrates the feasibility of detecting sex-specific and heritable metabolites in NHPs with diet-induced atherosclerosis using untargeted metabolomics allowing understanding of atherosclerotic disease progression in humans.

Background The purpose of this study was to determine whether dietary manipulation can reliably induce early-stage atherosclerosis and clinically relevant changes in vascular function in an established, well-characterized non-human primate model. Methods We fed 112 baboons a high-cholesterol, high-fat challenge diet for two years. We assayed circulating biomarkers of cardiovascular disease (CVD) risk, at 0, 7, and 104 weeks into the challenge; assessed arterial compliance noninvasively at 104 weeks; and measured atherosclerotic lesions in three major arteries at necropsy. Results We observed evidence of atherosclerosis in all but one baboon fed the two-year challenge diet. CVD risk biomarkers, the prevalence, size, and complexity of arterial lesions, plus consequent arterial stiffness, were increased in comparison with dietary control animals. Conclusions Feeding baboons a high-cholesterol, high-fat diet for two years reliably induces atherosclerosis, with risk factor profiles, arterial lesions, and changes in vascular function also seen in humans.

Objective Waist circumference (WC), the clinical marker of central obesity, is gaining popularity as a screening tool for type 2 diabetes (T2D). While there is epidemiologic evidence favoring the WC-T2D association, its biological substantiation is generally weak. Our objective was to determine the independent association of plasma lipid repertoire with WC. Methods Samples and data from the San Antonio Family Heart Study of 1208 Mexican Americans from 42 extended families were used. Association of plasma lipidomic profiles with the cross-sectionally assessed WC was determined. Plasma lipidomic profiling entailed liquid chromatography with mass spectrometry. Statistical analyses included multivariable polygenic regression models and bivariate trait analyses using the SOLAR software. Results After adjusting for age and sex interactions, body mass index, homeostasis model of assessment—insulin resistance, total cholesterol, triglycerides, high density lipoproteins and use of lipid lowering drugs, dihydroceramides as a class were associated with WC. Dihydroceramide species 18:0, 20:0, 22:0, and 24:1 were significantly associated and genetically correlated with WC. Two sphingomyelin species (31:1 and 41:1) were also associated with WC. Conclusions Plasma dihydroceramide levels independently associate with WC. Thus, high resolution plasma lipidomic studies can provide further credence to the biological underpinnings of the association of WC with T2D.

Intracortical microstructure influences crack propagation and arrest within bone cortex. Genetic variation in intracortical remodeling may contribute to mechanical integrity and, therefore, fracture risk. Our aim was to determine the degree to which normal population-level variation in intracortical microstructure is due to genetic variation. We examined right femurs from 101 baboons (74 females, 27 males; aged 7–33 years) from a single, extended pedigree to determine osteon number, osteon area (On.Ar), haversian canal area, osteon population density, percent osteonal bone (%On.B), wall thickness (W.Th), and cortical porosity (Ct.Po). Through evaluation of the covariance in intracortical properties between pairs of relatives, we quantified the contribution of additive genetic effects (heritability [h 2]) to variation in these traits using a variance decomposition approach. Significant age and sex effects account for 9 % (Ct.Po) to 21 % (W.Th) of intracortical microstructural variation. After accounting for age and sex, significant genetic effects are evident for On.Ar (h 2 = 0.79, p = 0.002), %On.B (h 2 = 0.82, p = 0.003), and W.Th (h 2 = 0.61, p = 0.013), indicating that 61–82 % of the residual variation (after accounting for age and sex effects) is due to additive genetic effects. This corresponds to 48–75 % of the total phenotypic variance. Our results demonstrate that normal, population-level variation in cortical microstructure is significantly influenced by genes. As a critical mediator of crack behavior in bone cortex, intracortical microstructural variation provides another mechanism through which genetic variation may affect fracture risk.

Several measures of lipoprotein phenotype are significant predictors of cardiovascular risk. Although such lipoprotein phenotypes are under strong genetic control, it is not clear to what extent they are controlled by the same - and by different - genes and whether these relationships may be altered in different dietary environments. Therefore, we measured six lipoprotein traits (three LDL traits - LDLC and apoB concentrations and LDL size - and three HDL traits - HDLC and apoA1 concentrations and HDL size) on each of three diets differing in level of fat and cholesterol. In bivariate analyses, all but two metabolically related trait pairs were genetically correlated, though none were completely correlated, implying additive genetic effects by both pleiotropic and unique genes. In comparing genetic correlations for the same pair of traits across diet, we detected evidence of diet effects on genetic control of these metabolically related traits; specifically, increasing level of dietary cholesterol was associated with a significant decrease in the genetic correlation of apoA1 with HDL size, and a significant increase in the genetic correlations of LDL size with LDLC and apoB. The results suggest a complex network of genes affecting lipoprotein metabolism: the genes may exert both unique and pleiotropic effects; the genes may exert detectable effects in many or only in specific dietary environments.

Background Little is known about the degree to which baboons, an important animal model in skeletal research, spontaneously experience age-related osteopenia and osteoporosis. Methods We measured bone mineral density (BMD) in 667 baboons, assigned T-scores to older animals based on sex-specific young adult reference groups, and compared reproductive history in older females with low BMD to those with normal BMD. Results Approximately 25% of older baboon females were osteopenic. No females or males were osteoporotic. Neither parity nor interbirth interval spine clearly distinguished low vs. normal BMD groups. Intersite correspondence in low BMD was highest between sites in the same region rather than sites of the same bone type. Conclusion As with humans, osteopenia is common among older females. The absence of osteoporotic animals may be due to colony maintenance resulting in truncation of the aged population and selection for healthier animals in the oldest ranges.

Both lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) activity, a biomarker of inflammation, and concentration of its primary associated lipoprotein, LDL, are correlated with adverse coronary outcomes. We previously reported a quantitative trait locus (QTL) corresponding to HSA2p24.3-p23.2 with pleiotropic effects on Lp-PLA(2) activity and LDL-cholesterol (LDL-C) concentration in baboons fed a basal diet. Here, our goal was to locate pleiotropic QTLs influencing both traits in the same baboons fed a high-cholesterol, high-fat (HCHF) diet, and to assess whether shared genetic effects on these traits differ between diets. We assayed Lp-PLA(2) activity and LDL-C concentration in 683 baboons fed the HCHF diet. We used a bivariate maximum likelihood-based variance components approach in whole-genome linkage screens to locate a QTL [logarithm of odds (LOD) = 3.13, genome-wide P = 0.019] corresponding to HSA19q12-q13.2 with pleiotropic effects on Lp-PLA(2) activity and LDL-C levels in the HCHF diet. We additionally found significant evidence of genetic variance in response to diet for Lp-PLA(2) activity (P = 0.0017) and for LDL-C concentration (P = 0.00001), revealing a contribution of genotype-by-diet interaction to covariation in these two traits. We conclude that the pleiotropic QTLs detected at 2p24.3-p23.2 and 19q12-q13.2 on the basal and HCHF diets, respectively, exert diet-specific effects on covariation in Lp-PLA(2) activity and LDL-C concentration.

Resistin has been associated with inflammation and risk for cardiovascular disease. We previously reported evidence of a QTL on chromosome 19p13 affecting the abundance of resistin (RETN) mRNA in the omental adipose tissue of baboons (L0D score 3.8). In this study, whole genome transcription levels were assessed in human lymphocyte samples from 1240 adults participating in the San Antonio Family Heart Study, using the Sentrix Human-6 Expression Beadchip. Lymphocytes were surveyed, as it has been proposed that their expression levels may reflect those in harder to ascertain tissues, such as adipose tissue, that are thought to be more directly relevant to disease procesn was conducted to detect loci affecting RETN mRNA levels. We obtained significant evidence for a QTL influencing the RETN expression (LOD score 10.7) on chromosome 19p. This region is orthologous/homologous to the region previously localized on baboon chromosome 19. The strongest positional candidate gene in this region is the structural gene for resistin, itself. We also found evidence for a QTL influencing resistin protein levels (LOD score 5.3) on chromosome 14q. This differs from our previously reported QTL on chromosome 18 in baboons. The different QTLs for circulating protein suggests that post-translational processing and turnover may be influenced by different or multiple genes in baboons and humans. The parallel findings of a cis-eQTL for RETN mRNA in baboon omental tissue and human lymphocytes lends support to the strategy of using lymphocyte gene expression levels as a surrogate for gene expression levels in other tissues.

Background: Ghrelin is an orexigenic hormone that is produced primarily in the stomach, and stimulates food intake via its receptors situated in the hypothalamus. Objective: The purpose of this study was to characterize baboon ghrelin cDNA and investigate the genetic influence on the variation in plasma ghrelin levels in baboons. Methods and Procedures: The sample consisted of 376 baboons (263 females, 113 males) from a pedigreed colony at the Southwest Foundation for Biomedical Research, San Antonio, Texas. Ghrelin cDNA was cloned by reverse-transcription polymerase chain reaction (RT-PCR) and sequenced. Real-time RT-PCR was performed to quantify mRNA from the collected tissues. Genetic contribution to plasma ghrelin was estimated using a variance components method implemented in SOLAR. Results: The baboon coding region and predicted amino acid sequence for ghrelin showed 97 and 96% sequence identity with humans, respectively. Maximum expression of ghrelin mRNA was detected in hypothalamus and stomach. Mean ± s.e. plasma levels of ghrelin were 3,406 ± 99 pg/ml. A significant heritability was observed for plasma ghrelin (h2= 0.25, P < 0.001). A genome-wide scan revealed the evidence of suggestive linkage for a locus affecting plasma ghrelin on chromosome 9q22 (between markers D9S910 and D9S261, logarithm of the odds (LOD) score = 2.3). Significant genetic correlations (P < 0.001) among ghrelin, body weight, and leptin were observed. Discussion: These results indicate a significant genetic component in the variation of plasma ghrelin in baboons and reveal a high degree of similarity between baboon and human ghrelin with respect to its cDNA and its correlation with other obesity traits.

To detect and localize the effects of genes influencing variation in adiponectin mRNA and protein levels, we conducted statistical genetic analyses of circulating concentrations of adiponectin and adiponectin (ADIPOQ) mRNA expression in omental adipose tissue in adult, pedigreed baboons (Papio anubis). An omental adipose tissue biopsy and blood sample were collected from 427 baboons from the colony at the Southwest Foundation for Biomedical Research, San Antonio, TX. Total RNA was isolated from adipose tissue and adiponectin mRNA levels were assayed by real-time, quantitative reverse transcriptase-PCR. Adiponectin, insulin, glucose, cholesterol, high-density lipoproteins and triglycerides were measured in fasting serum. Quantitative genetic analyses were conducted for adiponectin mRNA and serum protein using a maximum likelihood-based variance decomposition approach. A genome-wide linkage analysis was conducted using adiponectin mRNA and protein levels as phenotypes. Significant heritability was estimated for ADIPOQ mRNA levels (h2=0.19+/-0.07, P=0.01) and protein levels (h2=0.28+/-0.14, P=0.003). Genetic correlations were found between adiponectin protein and body weight (rho(G)=-0.51, P=0.03), cell volume (rho(G)=-0.73, P=0.04), serum triglycerides (rho(G)=-0.67, P=0.03), and between adiponectin mRNA and glucose (rho(G)=0.93, P

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), the major portion of which is bound to low-density lipoprotein, is an independent biomarker of cardiovascular disease risk. To search for common genetic determinants of variation in both Lp-PLA(2) activity and LDL cholesterol (LDL-C) concentration, we assayed these substances in serum from 679 pedigreed baboons. Using a maximum likelihood-based variance components approach, we detected significant evidence for a QTL affecting Lp-PLA(2) activity (LOD=2.79, genome-wide P=0.039) and suggestive evidence for a QTL affecting LDL-C levels (LOD=2.16) at the same location on the baboon ortholog of human chromosome 2p. Because we also found a significant genetic correlation between the two traits (rho(G)=0.50, P0.00001), we conducted bivariate linkage analyses of Lp-PLA(2) activity and LDL-C concentration. These bivariate analyses improved the evidence (LOD=3.19, genome-wide P=0.015) for a QTL at the same location on 2p, corresponding to the human cytogenetic region 2p24.3-p23.2. The QTL-specific correlation between the traits (rho(Q)=0.62) was significantly different from both zero and 1 (P[rho(Q)=0]=0.047; P[rho(Q)=1]=0.022), rejecting the hypothesis of co-incident linkage and consistent with incomplete pleiotropy at this locus. We conclude that polymorphisms at the QTL described in this study exert some genetic effects that are shared between Lp-PLA(2) activity and LDL-C concentration.

Background There is growing interest in the hypertriglyceridemic waist (HTGW) phenotype, defined as high waist circumference (≥95 cm in males and ≥80 cm in females) combined with high serum triglyceride concentration (≥2.0 mmol/L in males and ≥1.5 mmol/L in females) as a marker of type 2 diabetes (T2D) and cardiovascular disease. However, the prevalence of this phenotype in high-risk populations, its association with T2D, and the genetic or epigenetic influences on HTGW are not well explored. Using data from large, extended families of Mexican Americans (a high-risk minority population in the USA) we aimed to: (1) estimate the prevalence of this phenotype, (2) test its association with T2D and related traits, and (3) dissect out the genetic and epigenetic associations with this phenotype using genome-wide and epigenome-wide studies, respectively. Results Data for this study was from 850 Mexican American participants (representing 39 families) recruited under the ongoing San Antonio Family Heart Study, 26 % of these individuals had HTGW. This phenotype was significantly heritable (h2r = 0.52, p = 1.1 × 10−5) and independently associated with T2D as well as fasting glucose levels and insulin resistance. We conducted genome-wide association analyses using 759,809 single nucleotide polymorphisms (SNPs) and epigenome-wide association analyses using 457,331 CpG sites. There was no evidence of any SNP associated with HTGW at the genome-wide level but two CpG sites (cg00574958 and cg17058475) in CPT1A and one CpG site (cg06500161) in ABCG1 were significantly associated with HTGW and remained significant after adjusting for the closely related components of metabolic syndrome. CPT1A holds a cardinal position in the metabolism of long-chain fatty acids while ABCG1 plays a role in triglyceride metabolism. Conclusions Our results reemphasize the value of HTGW as a marker of T2D. This phenotype shows association with DNA methylation within CPT1A and ABCG1, genes involved in fatty acid and triglyceride metabolism. Our results underscore the importance of epigenetics in a clinically informative phenotype. Electronic supplementary material The online version of this article (doi:10.1186/s13148-016-0173-x) contains supplementary material, which is available to authorized users.

BACKGROUND Oxidative stress is a widely accepted risk factor for cardiovascular disease (CVD), but the CVD benefit of dietary antioxidants, such as vitamin E, is controversial. OBJECTIVE Therefore, we have investigated, in the baboon model, the effects of dietary vitamin E supplementation on risk factors for CVD. DESIGN Pedigreed baboons (n = 251) were fed 2 atherogenic diets, high in fat and cholesterol, that differed in vitamin E concentrations. After 7 wk on each diet, blood samples were taken, and a panel of CVD risk factor traits (ie, indicators of lipoprotein metabolism and oxidative stress) were measured. RESULTS Vitamin E supplementation caused significantly higher total antioxidant status (TAS) and lower oxidized LDL as expected. In addition, vitamin E caused 2 paradoxical effects on HDL metabolism: higher apolipoprotein A-I (apo A-I) concentrations and lower HDL sizes. We calculated a difference (Delta) variable for each trait as the value on the high-vitamin E diet minus that on the low-vitamin E diet and determined that several HDL concentration Delta variables were significantly correlated with Delta TAS, but only one, Delta apo A-I, was independently correlated. Genetic analyses showed that 2 Delta variables, Delta paraoxonase and Delta HDL(2), were significantly heritable, but that neither Delta TAS nor Delta apo A-I were heritable. CONCLUSIONS Thus, our data show that dietary vitamin E improves TAS and LDL quality. They also show 2 apparently paradoxical effects on HDL metabolism: lower HDL(2), which is mediated by genes, and higher apo A-I, which is not. These effects have contrasting associations with CVD risk and may help account for the mixed results from clinical trials of dietary vitamin E.

Bone ALP and OC are under partial genetic control. This study of 591 pedigreed baboons shows a QTL corresponding to human 6p23–21.3 that accounts for 25% (bone ALP) and 20% (OC) of the genetic variance. A gene affecting osteoblast activity, number, or recruitment likely resides in this area. Bone ALP and OC are under partial genetic control. This study of 591 pedigreed baboons shows a QTL corresponding to human 6p23–21.3 that accounts for 25% (bone ALP) and 20% (OC) of the genetic variance. A gene affecting osteoblast activity, number, or recruitment likely resides in this area. Introduction: Serum levels of bone alkaline phosphatase (ALP) and osteocalcin (OC) reflect osteoblast activity. Both of these measures are under partial genetic control. Genetic effects on bone ALP have not been previously localized to chromosomal regions in primates, nor has the degree to which genetic effects are shared (pleiotropic) between bone ALP and OC been studied. Materials and Methods: We applied variance components methods to a sample of 591 adult pedigreed baboons to detect and quantify effects of genes that influence bone ALP and that have pleiotropic effects on bone ALP and OC. A univariate linkage analysis was conducted for bone ALP. Bivariate linkage analyses were conducted in areas for which the bone ALP results presented here and a previous univariate OC linkage analysis showed evidence for linkage on the same chromosome for both bone ALP and OC. Results: A quantitative trait locus (QTL) for serum levels of bone ALP is evident on the baboon ortholog of human chromosomal region 6p (LOD 2.93). Thirty-seven percent (genetic correlation [ρG] =0.61) of the genetic variance in bone ALP and OC is caused by pleiotropic effects of the same gene(s). Bivariate linkage analysis revealed a QTL in the region corresponding to human chromosome 6p23–21.3, with the strongest evidence for bivariate linkage near D6S422 (LOD =2.97 at 22 cM from our pter-most marker). D6S422 maps to 20.4 Mb in the human genome. The QTL-specific heritability (h2) is 0.25 and 0.20 for bone ALP and OC, respectively. Conclusions: This first formal test for shared genetic effects on two serum markers of osteoblast activity indicates that a significant pleiotropic effect on bone ALP and OC levels, and thus on bone formation, is detectible. The fact that this region corresponds to one on mouse chromosome 13 that has repeatedly yielded QTLs for BMD should encourage more intensive study of the effect of genes in this region on bone maintenance and turnover.

Background Inflammation and oxidative stress are processes that mark early metabolic abnormalities in vascular diseases. Objectives We explored the effects of a high-fat, high-cholesterol (HFHC) diet on vascular responses in baboons and the potential response-attenuating effects of vitamin E and coenzyme Q(10) (CoQ(10)) supplementation. Design We used a longitudinal design by subjecting 21 baboons (Papio hamadryas) to sequential dietary challenges. Results After being maintained for 3 mo on a baseline diet (low in fat and cholesterol), 21 baboons were challenged with an HFHC diet for 7 wk. The serum C-reactive protein (CRP) concentrations did not change. Subsequent supplementation of the HFHC diet with the antioxidant vitamin E (250, 500, or 1000 IU/kg diet) for 2 wk reduced serum CRP concentrations from 0.91 +/- 0.02 to 0.43 +/- 0.06 mg/dL. Additional supplementation with CoQ(10) (2 g/kg diet) further reduced serum CRP to approximately 30% of baseline (0.28 +/- 0.03 mg/dL; P = 0.036 compared with the HFHC diet). Introduction of the HFHC diet itself significantly decreased serum P-selectin (from 48.8 +/- 7.2 to 32.9 +/- 3.7 ng/dL, P = 0.02) and von Willebrand factor (from 187.0 +/- 10.1 to 161.9 +/- 9.0%, P = 0.02) concentrations. However, neither vitamin E alone nor vitamin E plus CoQ(10) significantly altered the serum concentrations of P-selectin or von Willebrand factor. Conclusions Dietary supplementation with vitamin E alone reduces the baseline inflammatory status that is indicated by the CRP concentration in healthy adult baboons. Cosupplementation with CoQ(10), however, significantly enhances this antiinflammatory effect of vitamin E.

Objective: Glucose transporter 4 (GLUT4) is an insulin-responsive glucose transporter expressed in adipose tissue. A decrease of the mRNA abundance of GLUT4 in adipose tissue has been observed in conditions of insulin resistance. The objective was to conduct quantitative genetic analyses using GLUT4 mRNA levels in omental adipose tissue of baboons as a novel phenotype. Research Methods and Procedures: A blood sample and a biopsy of omental adipose tissue were collected from 418 adult, pedigreed baboons. Total RNA was isolated from adipose tissue biopsies, and GLUT4 mRNA abundance was assayed by quantitative, real-time reverse transcription-polymerase chain reaction. Insulin and glucose were determined in fasting plasma by standard methods. Quantitative genetic analyses were conducted using GLUT4 mRNA, insulin, and glucose as quantitative traits. Results: GLUT4 mRNA expression in omental adipose tissue was heritable (h2 = 0.23, p = 0.001). Bivariate genetic analyses revealed a significant genetic correlation (ρG) between GLUT4 mRNA abundance and both body weight (ρG = 0.63, p = 0.007), BMI (ρG = 0.59, p = 0.02) and insulin (ρG = 0.72, p = 0.04). A genome scan was conducted, and a quantitative trait locus was detected on chromosome 10p12 with a logarithm of the odds ratio score of 1.1. Discussion: GLUT4 mRNA abundance in omental adipose tissue has a significant genetic component. These findings suggest that expression of GLUT4 mRNA, plasma insulin levels, and body weight may be regulated by common genes.

The hormone resistin was recently discovered in adipose tissue of mice. Functional tests suggest a role for resistin in the regulation of insulin sensitivity. However, human studies have reported controversial results on the metabolic function of this hormone.A 1 g omental adipose tissue biopsy was obtained from 404 adult baboons. Resistin mRNA expression was assayed by real-time, quantitative RT-PCR, and univariate and bivariate quantitative genetic analyses were performed, via the variance decomposition approach. A genome scan analysis was conducted using resistin mRNA abundance in omental adipose tissue as a quantitative phenotype.A significant heritability of h2 = 0.23 (P = 0.003) was found for resistin mRNA abundance in omental adipose tissue. A genome scan detected a quantitative trait locus for resistin expression with an LOD score of 3.8, in the region between markers D19S431 and D19S714, corresponding to human chromosome 19 p13. This chromosomal region contains genes related to insulin resistance phenotypes, such as resistin, insulin receptor, angiopoietin-like 4 protein and LDL receptor.Individual variation in resistin mRNA expression has a significant genetic component, and a gene or genes on chromosome 19 p13 may regulate resistin mRNA levels in baboon omental adipose tissue.

Over 23 months, zinc toxicosis was diagnosed in 35 baboons aged 5-12 months in one galvanized metal and concrete cage complex with conditions that led to excessive exposure to environmental zinc. Clinical signs included reduced pigmentation of hair, skin, and mucous membranes (whiteness), alopecia, dehydration, emaciation, cachexia, dermatitis, diarrhea and, in six cases, severe gangrenous dermatitis of extremities. The syndrome was characterized by pancytopenia, elevated zinc and low copper serum concentrations, low vitamin D and bone-specific alkaline phosphatase levels, and atypical myelomonocytic proliferation of bone marrow. This syndrome emphasizes the importance of proper husbandry and cage design and indicates the potential of infant baboons as a model to study the effects of excessive zinc on development. This is the first report describing the epidemiologic and clinical presentation of zinc toxicosis in infant baboons in captivity.

While more than 77% of the people in the US with osteoporosis are women, the contributions of genotype-by-sex (G×S) and environment-by-sex interactions to sex differences in osteoporosis risk factors have not been studied. To address this issue, we conducted a statistical genetic analysis of serum concentrations of bone-specific alkaline phosphatase (Bone ALP), a highly specific marker of osteoblast function that is elevated in persons with conditions like osteoporosis characterized by excessive bone turnover or rapid bone loss. We assayed Bone ALP from 657 pedigreed baboons using a commercially available ELISA kit. Using a maximum likelihood variance decomposition approach, we treated sex as an environmental milieu in which genes influencing Bone ALP levels are expressed. We modeled the genetic covariance in Bone ALP between all relative pairs conditional on their sex so that the covariance is the product of the kinship, the genetic correlation between trait levels in the two sexes, and the genetic variances in the two sexes. Sex-specific maximum likelihood estimates (MLE) of residual heritability for Bone ALP were greater for females than for males ( h 2 = 0.44 vs. h 2 = 0.26, respectively), but likelihood ratio tests revealed only a marginally significant difference in sex-specific genetic variances ( P = 0.057). In contrast, the between-sex genetic correlation ( ρ G = 0.43) was significantly less than 1.0 ( P = 0.037), and the difference in sex-specific environmental variances was highly significant ( P = 0.00006). We report the first evidence for G×S interactions influencing variation in an osteoporosis risk factor. The diminished between-sex genetic correlation implies that different genes influence Bone ALP levels in the two sexes. The significant differences between environmental variances suggest that unmeasured factors, including those from the internal, biological environments of the two sexes, account for a greater proportion of the Bone ALP variation in males.

We seek to determine whether significant gene x smoking interaction effects exist on plasma triglyceride (TG) levels, HDL cholesterol (HDL-C) level, and median LDL particle diameter (LDL-MPD) in Mexican American families enrolled in the San Antonio Family Heart Study. The sample consisted of 1,392 individuals distributed in 42 extended pedigrees, ranging in age from 16 years to 92 years. Separate quantitative genetic analyses were carried out for TG and HDL-C level and LDL-MPD using a maximum-likelihood-based variance decomposition approach while simultaneously adjusting for age and sex. Initial heritability estimates demonstrated significant (p < 0.001) additive genetic contributions to all three traits (h2 range 0.50 - 0.54). To test for a gene x smoking interaction, we included in the model additional smoking-status-specific variance terms and a genetic correlation term between smokers and nonsmokers. Comparisons of nested models revealed significant evidence (p < 0.01) for a gene X smoking interaction effect on TG level and LDL-MPD and possible evidence for an effect on HDL-C level. These results indicate that the gene or suite of genes regulating each of these phenotypes is likely the same in smokers and non-smokers but that smoking may alter the expression of genes, particularly those influencing TG level and LDL-MPD.

Small, dense LDLs and hypertriglyceridemia, two highly correlated and genetically influenced risk factors, are known to predict for risk of coronary heart disease. The objective of this study was to perform a whole-genome scan for linkage to LDL size and triglyceride (TG) levels in 26 kindreds with familial hypertriglyceridemia (FHTG). LDL size was estimated using gradient gel electrophoresis, and genotyping was performed for 355 autosomal markers with an average heterozygosity of 76% and an average spacing of 10.2 centimorgans (cMs). Using variance components linkage analysis, one possible linkage was found for LDL size [logarithm of odds (LOD) = 2.1] on chromosome 6, peak at 140 cM distal to marker F13A1 (closest marker D6S2436). With adjustment for TG and/or HDL cholesterol, the LOD scores were reduced, but remained in exactly the same location. For TG, LOD scores of 2.56 and 2.44 were observed at two locations on chromosome 15, with peaks at 29 and 61 cM distal to marker D15S822 (closest markers D15S643 and D15S211, respectively). These peaks were retained with adjustment for LDL size and/or HDL cholesterol. These findings, if confirmed, suggest that LDL particle size and plasma TG levels could be caused by two different genetic loci in FHTG.

Although published normative reference standards for hematologic and clinical chemistry measures are available for adult baboons, their applicability to infants has not been addressed. We analyzed these measures in 110 infant baboons (55 females and 55 males) from a large breeding colony at the Southwest Regional Primate Research Center in San Antonio, Texas. The sample consists of olive baboons and olive/yellow baboon hybrids, 1 week to 12 months of age. We produced cross-sectional reference values and examined the effects of age, sex, and subspecies on these variables. Hematology reference ranges for infant baboons are similar to, but wider than, those for adults. Reference ranges for blood biochemistry measures are generally more dissimilar to adults, indicating that for many variables, reference ranges for adult baboons are not adequate for infants. Although sex and subspecies differences are rare, age accounts for more than 10% of the variance in many of the variables.

Objective: Studies have reported the existence of marked sexual dimorphism in serum leptin levels in humans with women having approximately two to three times the levels of men. We have shown that this sexual dimorphism has a strong genetic component arising from a genotype by sex interaction, but adjusting leptin levels for testosterone eliminates this interaction. Because interactions such as genotype × sex can confound the detection of quantitative trait loci (QTLs), we wanted to determine if there are QTLs associated with the expression of leptin adjusted for testosterone. Research Methods and Procedures: We performed a genome-wide scan using multipoint linkage analysis and implemented a general pedigree-based variance-component approach to identify genes with measurable effects on variation in leptin levels independent of testosterone in 318 Mexican Americans from the San Antonio Family Heart Study. Results: We detected significant evidence of linkage (log of the odds ratio = 3.44) for a QTL on chromosome 22. Discussion: Given these results, we hypothesize that a QTL on chromosome 22 may influence the level of leptin adjusted for testosterone.

We fed 634 baboons three diets to assess the separate effects of increasing dietary fat and cholesterol intakes on three independent measures of HDL phenotype: concentrations of HDL cholesterol and apoAI, and size distributions of HDL cholesterol. Increasing dietary fat significantly increased concentrations of HDL cholesterol and apoAI (both, P

Abstract —The interrelationships among low density lipoprotein (LDL) particle size, plasma triglyceride (TG), and high density lipoprotein cholesterol (HDL-C) are well established and may involve underlying genetic influences. This study evaluated common genetic effects on LDL size, TG, and HDL-C by using data from 85 kindreds participating in the Genetic Epidemiology of Hypertriglyceridemia (GET) Study. A multivariate, maximum likelihood–based approach to quantitative genetic analysis was used to estimate the additive effects of shared genes and shared, unmeasured nongenetic factors on variation in LDL size and in plasma levels of TG and HDL-C. A significant ( P P ρ G ), indicative of the shared additive effects of genes on pairs of traits, were estimated between all 3 trait pairs: for LDL size and TG ρ G =−0.87, for LDL size and HDL-C ρ G =0.65, and for HDL-C and TG ρ G =−0.54. A similar pattern of significant environmental correlations between the 3 trait pairs was also observed. These results suggest that a large proportion of the well-documented correlations in LDL size, TG, and HDL-C are likely attributable to the influence of the same gene(s) in these families. That is, the gene(s) that may contribute to decreases in LDL size also contribute significantly to higher plasma levels of TG and lower plasma levels of HDL-C. These relationships may be useful in identifying genes responsible for the associations between these phenotypes and susceptibility to cardiovascular disease in these families.

We previously reported that our genome-scanning initiative had detected a highly significant linkage (log odds ratio = 4.95; P = 9 × 10−7) between a quantitative trait locus (QTL) on chromosome 2 and leptin levels in Mexican American families. We now have typed additional microsatellite markers in this region, increasing this log odds ratio score to 7.46 (P = 2 × 10−9). This region of chromosome 2 contains a strong positional candidate gene, POMC. The POMC gene codes for POMC, the prohormone from which αMSH, ACTH, and β-endorphin are derived. Studies by others have shown that POMC-derived products are involved in the regulation of appetite and obesity. We have used polymorphisms in POMC to map its location within the 95% confidence interval of the peak for the linkage signal for the QTL. We also constructed POMC haplotypes using these polymorphisms and have found a significant association with normal variation in leptin levels (P = 0.001). We conclude that variation in POMC is associated with normal varia...

Abstract —We investigated dietary effects on pleiotropic relationships among 3 HDL cholesterol (C) subfractions (HDL 1 -C, HDL 2 -C, and HDL 3 -C; levels quantified by gradient gel electrophoresis) for 942 pedigreed baboons ( Papio hamadryas ) who were fed a basal (Chow) diet and a high cholesterol, saturated fat (HCSF) challenge diet. Using multivariate maximum likelihood methods we estimated heritabilities for all 6 traits, genetic and environmental correlations (ρ G and ρ E ) between them, and the additive genetic variance of each subfraction’s response to the diets. On the Chow diet, genetic correlations between the 3 subfractions were significant, and we observed complete pleiotropy between HDL 1 -C and HDL 3 -C (ρ G =−0.81). On the HCSF diet, only the genetic correlation between HDL 1 -C and HDL 3 -C (ρ G =−0.61) was significant. Genetic correlations between individual subfractions on the Chow and HCSF diets did not differ significantly from 1.0, indicating that the same additive genes influenced each subfraction’s levels regardless of diet. However, the additive genetic variance of response to the diets was highly significant for HDL 1 -C and HDL 2 -C, but not for HDL 3 -C. Similar sets of genes influence variation in the 3 HDL subfractions on the Chow diet, and the same set influences variation in each subfraction on the HCSF diet. However, the expression of genes influencing HDL 1 -C and HDL 2 -C is altered by the HCSF diet, disrupting the pleiotropy observed between the 3 subfractions on the Chow diet.

Leptin is the peptide product of the OB gene, which is associated with obesity in some strains of mice. Because dyslipidemias are frequently associated with obesity, we have begun to characterize the pathways connecting these related traits. In this investigation we tested for correlation of HDL phenotype measures with leptin concentrations using data from 1159 participants in the San Antonio Family Heart Study, a study of risk factors for cardiovascular disease in Mexican Americans living in and around San Antonio, Texas. In a subset of 288 unrelated individuals, we tested for correlation of leptin with nine different measures of HDL phenotype and found that only three were significantly related. However, stepwise regression analysis suggested that only two measures, HDL triglyceride concentrations (HDL-TG) and the proportion of apo A-I on HDL particles larger than HDL3 (Large HDL-apo A-I), were independently correlated with leptin. Because obesity and HDL phenotypes are both under strong genetic control, we conducted a trivariate genetic analysis, using the entire data set, to test the hypothesis that the phenotypic correlations were due to the effects of shared genes (i.e., pleiotropy). Heritabilities for the three traits were estimated to be 0.47 for leptin, 0.46 for HDL-TG, and 0.46 for Large HDL-apo A-I. Results from the genetic analyses revealed that the phenotypic correlation of leptin with HDL-TG was nongenetic (i.e., shared environment), while the phenotypic correlation with Large HDL-apo A-I was due to pleiotropy (i.e., shared genes). These results confirmed the result derived from the subset of unrelated individuals that the two measures of HDL are independently correlated with leptin. To our knowledge, this is the first report of a relationship between leptin and any aspect of lipoprotein phenotype. A better understanding of the genes responsible for this relationship may provide a molecular explanation for the aggregation of atherogenic phenotypes, such as diabetes, obesity, and dyslipoproteinemia.

Obesity is a major predisposing factor for the development of several chronic diseases including non-insulin dependent diabetes mellitus (NIDDM) and coronary heart disease (CHD). Leptin is a serum protein which is secreted by adipocytes1–4 and thought to play a role in the regulation of body fat5–8. Leptin levels in humans have been found to be highly correlated with an individual's total adiposity8,9. We performed a genome-wide scan and conducted multipoint linkage analysis using a general pedigree-based variance component approach to identify genes with measurable effects on quantitative variation in leptin levels in Mexican Americans. A microsatellite polymorphism, D2S1788, mapped to chromosome 2p21 (approximately 74 cM from the tip of the short arm) and showed strong evidence of linkage with serum leptin levels with a lod score of 4.95 (P = 9 × 10−7). This locus accounted for 47% of the variation in serum leptin levels, with a residual additive genetic component contributing an additional 24%. This region contains several potential candidate genes for obesity, including glucokinase regulatory protein (GCKR) and pro-opiomelanocortin (POMC). Our results show strong evidence of linkage of this region of chromosome 2 with serum leptin levels and indicate that this region could contain an important human obesity gene.

We have performed plasma lipid profiling using liquid chromatography electrospray ionization tandem mass spectrometry on a population cohort of more than 1,000 individuals. From 10 μl of plasma we were able to acquire comparative measures of 312 lipids across 23 lipid classes and subclasses including sphingolipids, phospholipids, glycerolipids, and cholesterol esters (CEs) in 20 min. Using linear and logistic regression, we identified statistically significant associations of lipid classes, subclasses, and individual lipid species with anthropometric and physiological measures. In addition to the expected associations of CEs and triacylglycerol with age, sex, and body mass index (BMI), ceramide was significantly higher in males and was independently associated with age and BMI. Associations were also observed for sphingomyelin with age but this lipid subclass was lower in males. Lysophospholipids were associated with age and higher in males, but showed a strong negative association with BMI. Many of these lipids have previously been associated with chronic diseases including cardiovascular disease and may mediate the interactions of age, sex, and obesity with disease risk.

Aims We aimed to determine the genetic and environmental correlation between various anthropometric indexes and incident Type 2 diabetes with a focus on waist circumference. Methods We used the data on extended Mexican-American families (808 subjects, 7617.92 person-years follow-up) from the San Antonio Family Heart Study and estimated the genetic and environmental correlations of 16 anthropometric indexes with the genetic liability of incident Type 2 diabetes. We performed bivariate trait analyses using the solar software package. Results All 16 anthropometric indexes were significantly heritable (range of heritabilities 0.24–0.99). Thirteen indexes were found to have significant environmental correlation with the liability of incident Type 2 diabetes. In contrast, only anthropometric indexes consisting of waist circumference (waist circumference, waist–hip ratio and waist–height ratio) were significantly genetically correlated (genetic correlation coefficients: 0.45, 0.55 and 0.44, respectively) with the liability of incident Type 2 diabetes. We did not observe such a correlation for BMI. Conclusions Waist circumference as a predictor of future Type 2 diabetes is supported by the finding that they share common genetic influences.

Both as a component of metabolic syndrome and as an independent entity, hypertension poses a continued challenge with regard to its diagnosis, pathogenesis, and treatment. Previous studies have documented connections between hypertension and indicators of lipid metabolism. Novel technologies, such as plasma lipidomic profiling, promise a better understanding of disorders in which there is a derangement of the lipid metabolism. However, association of plasma lipidomic profiles with hypertension in a high-risk population, such as Mexican Americans, has not been evaluated before. Using the rich data and sample resource from the ongoing San Antonio Family Heart Study, we conducted plasma lipidomic profiling by combining high-performance liquid chromatography with tandem mass spectroscopy to characterize 319 lipid species in 1192 individuals from 42 large and extended Mexican American families. Robust statistical analyses using polygenic regression models, liability threshold models, and bivariate trait analyses implemented in the SOLAR software were conducted after accounting for obesity, insulin resistance, and relative abundance of various lipoprotein fractions. Diacylglycerols, in general, and the DG 16:0/22:5 and DG 16:0/22:6 lipid species, in particular, were significantly associated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), as well as liability of incident hypertension measured during 7140.17 person-years of follow-up. Four lipid species, including the DG 16:0/22:5 and DG 16:0/22:6 species, showed significant genetic correlations with the liability of hypertension in bivariate trait analyses. Our results demonstrate the value of plasma lipidomic profiling in the context of hypertension and identify disturbance of diacylglycerol metabolism as an independent biomarker of hypertension.

Previous studies have shown that the inverse relationship between HDL cholesterol (HDL-C) and triglyceride (TG) levels, risk factors for cardiovascular disease, is due largely to the effects of shared genes. HDL-C and TG are also known to be related to endogenous sex hormone levels, however the nature of the relationships is unclear. The objective of this study is to ascertain the extent to which these relationships are determined by shared genes. We conducted a multivariate quantitative genetic analysis of HDL-C, TG, dehydroepiandrosterone sulfate (DHEAS) and sex hormone-binding globulin (SHBG) in 635 people from 27 pedigrees participating in the San Antonio Family Heart Study. Heritabilities (h2) and genetic and environmental correlations (rho G and rho E) were estimated simultaneously by maximum likelihood methods. All four traits showed significant (P0.05) heritabilities: h2HDL-C = 0.38, h2TG = 0.54, h2DHEAS = 0.43, h2SHBG = 0.26. Significant genetic correlations were detected between HDL and each of the other traits: rho G(HDL-TG) = -0.56, rho G(HDL-DHEAS) = 0.23 and rho G(HDL-SHBG) = -0.56. However, there were no significant genetic correlations between TG and either measure of sex hormones. Thus, at least three separate groups of genes influence HDL-C levels in Mexican Americans: one group that has pleiotropic effects on HDL and TG, one group influences both HDL-C and SHBG and a third influences both HDL-C and DHEAS.

Abstract Insulin resistance is part of a metabolic syndrome that also includes non–insulin-dependent diabetes mellitus, dyslipidemia, obesity, and hypertension. It has been hypothesized that insulin resistance represents the primary physiological defect underlying this syndrome. Since insulin resistance is at least partially genetically determined, we hypothesized that genes influencing insulin resistance would have pleiotropic effects on a number of other traits, including triglyceride (TG) and HDL cholesterol levels, body mass index (BMI) and body fat distribution, and blood pressure levels. To investigate this hypothesis, we analyzed data obtained from individuals in 41 families enrolled in the San Antonio Family Heart Study. Statistical methods that take advantage of the relatedness among individuals were used to differentiate between genetic and nongenetic (ie, environmental) contributions to phenotypic variation between traits. Serum levels of fasting and 2-hour insulin (measured in 767 and 743 nondiabetic family members, respectively) were used as a measure of insulin resistance. The genetic correlations were high between insulin levels (both fasting and 2-hour) and each of the following: BMI, HDL level, waist-to-hip ratio, and subscapular-to-triceps ratio, indicating that the same gene, or set of genes, influences each pair of traits. In contrast, the genetic correlations of insulin levels with systolic and diastolic blood pressures were low. We have previously shown that a single diallelic locus accounts for 31% of the phenotypic variation in 2-hour insulin levels in this population. We conducted a bivariate segregation analysis to see if the common genetic effects on insulin and these other traits could be attributable to this single locus. These results indicated a significant effect of the 2-hour insulin locus on fasting insulin levels ( P =.02) and BMI ( P =.05), with the “high” insulin allele associated with higher levels of fasting insulin but lower levels of BMI. There was no detectable effect of this locus on HDL level, TG level, subscapular-to-triceps ratio, or blood pressure. Overall, these results suggest that a common set of genes influencing insulin levels also influences other insulin resistance syndrome–related traits, although for the most part this pleiotropy is not attributable to the 2-hour insulin level major locus.

Objective In spite of the growing recognition of the specific association of waist circumference (WC) with type 2 diabetes (T2D) and insulin resistance (IR), current guidelines still use body mass index (BMI) as a tool of choice. Our objective was to determine whether WC is a better T2D predictor than BMI in family-based settings. Research Design and Methods Using prospectively collected data on 808 individuals from 42 extended Mexican American families representing 7617.92 person-years follow-up, we examined the performance of WC and BMI as predictors of cumulative and incident risk of T2D. We used robust statistical methods that accounted for the kinships and included polygenic models, discrete trait modeling, Akaike information criterion, odds ratio (OR), relative risk (RR) and Kullback-Leibler R2. SOLAR software was used to conduct all the data analyses. Results We found that in multivariate polygenic models, WC was an independent predictor of cumulative (OR = 2.76, p = 0.0002) and future risk of T2D (RR = 2.15, p = 3.56×10−9) and outperformed BMI when compared in a head-to-head fashion. High WC (≥94.65 cm after adjusting for age and sex) was also associated with high fasting glucose, insulin and triglyceride levels and low high-density lipoprotein levels indicating a potential association with IR. Moreover, WC was specifically and significantly associated with insulin resistant T2D (OR = 4.83, p = 1.01×10−13). Conclusions Our results demonstrate the value of using WC as a screening tool of choice for future risk of T2D in Mexican American families. Also, WC is specifically associated with insulin resistant T2D.

Background The conjoint trait hypothesis proposes that combined low HDL cholesterol (HDL-C) and high triglyceride (TG) levels represent a single, inherited phenotype that adiposity may influence in an unspecified manner. We conducted formal statistical genetic tests of the conjoint trait hypothesis and the relation of the conjoint trait to adiposity using data for 569 subjects in 25 pedigrees from the San Antonio Family Heart Study. Methods and Results We conducted multivariate genetic analyses to detect the effects of genes and environmental factors on variation in plasma concentrations of HDL-C and TG, fat mass (as percent body weight [FM%], determined by bioelectric impedance), and body mass index (BMI). We used maximum-likelihood methods to simultaneously estimate the phenotypic means and SDs, heritabilities (h 2 ), effects of sex, age-by-sex, eight dietary and medical covariates, and genetic and environmental correlations. Likelihood ratio tests disclosed significant heritabilities ( P 2 HDL- C =0.55, h 2 TG =0.53, h 2 FM% =0.37, h 2 BMI =0.44) but significant genetic correlations ( P G =−0.52) and fat mass and BMI (ρ G =0.86). We obtained significant environmental correlations between all trait pairs except HDL-C and BMI ( P >.05). Conclusions Both shared genes (pleiotropy) and shared environmental factors contribute to the commonly observed inverse phenotypic association between plasma levels of HDL-C and TG. Rather than low HDL-C and high TG being a single, genetically transmissible entity, it is the inverse relation between these two phenotypes throughout their normal ranges of variation as well as at the extremes that is influenced by shared genes and shared environments. However, common environmental factors, not shared genes, account for reported associations of plasma HDL-C and TG levels with measures of adiposity.

Objective While the role of type 2 diabetes (T2D) in inducing endothelial dysfunction is fairly well-established the etiological role of endothelial dysfunction in the onset of T2D is still a matter of debate. In the light of conflicting evidence in this regard, we conducted a prospective study to determine the association of circulating levels of soluble intercellular adhesion molecule 1 (sICAM-1) and soluble vessel cell adhesion molecule 1 (sVCAM-1) with incident T2D. Methods Data from this study came from 1,269 Mexican Americans of whom 821 initially T2D-free individuals were longitudinally followed up in the San Antonio Family Heart Study. These individuals were followed for 9752.95 person-years for development of T2D. Prospective association of sICAM-1 and sVCAM-1 with incident T2D was studied using Kaplan-Meier survival plots and mixed effects Cox proportional hazards modeling to account for relatedness among study participants. Incremental value of adhesion molecule biomarkers was studied using integrated discrimination improvement (IDI) and net reclassification improvement (NRI) indexes. Results Decreasing median values for serum concentrations of sICAM-1 and sVCAM-1 were observed in the following groups in this order: individuals with T2D at baseline, individuals who developed T2D during follow-up, individuals with prediabetes at baseline and normal glucose tolerant (NGT) individuals who remained T2D-free during follow-up. Top quartiles for sICAM-1 and sVCAM-1 were strongly and significantly associated with homeostatic model of assessment—insulin resistance (HOMA-IR). Mixed effects Cox proportional hazards modeling revealed that after correcting for important clinical confounders, high sICAM-1 and sVCAM-1 concentrations were associated with 2.52 and 1.99 times faster progression to T2D as compared to low concentrations, respectively. Individuals with high concentrations for both sICAM-1 and sVCAM-1 progressed to T2D 3.42 times faster than those with low values for both sICAM-1 and sVCAM-1. The results were similar in women in reproductive age group and the remainder of the cohort. Inclusion of sICAM-1 and sVCAM-1 in predictive models significantly improved reclassification and discrimination. The majority of these results were seen even when the analyses were restricted to NGT individuals. Conclusion Serum concentrations of sICAM-1 and sVCAM-1 independently and additively predict future T2D and represent important candidate biomarkers of T2D.

We present the first cross-sectional organ weight by body weight reference standards for captive baboons (Papio hamadryas). Organ weight data were obtained from necropsy reports for 634 healthy, pedigreed, captive female and male baboons. From summary statistics we calculated and fit cross-sectional sex-specific percentile curves for: adrenals, brain, eyes, heart, kidneys, liver plus gall bladder, lungs, pancreas, pituitary gland, spleen, and thyroid gland in three kilogram body weight intervals and cross-sectional summary statistics by sex for each organ in one kilogram body weight intervals.

High-responding opossums are susceptible to developing hypercholesterolemia on a high-cholesterol diet, but low-responding opossums are resistant. The observation of low biliary cholesterol and low biliary phospholipids in high responders suggested that the ABCB4 gene affects response to dietary cholesterol. Two missense mutations (Arg29Gly and Ile235Leu) were found in the ABCB4 gene of high responders. High responders (ATHH strain) were bred with low responders (ATHE or ATHL strain) to produce F1 and F2 progeny in two different genetic crosses (KUSH6 and JCX) to determine the effect of ABCB4 allelic variants on plasma cholesterol concentrations after a dietary challenge. Pedigree-based genetic association analyses consistently implicated a variant in ABCB4 or a closely linked locus as a major, but not the sole, genetic contributor to variation in the plasma cholesterol response to dietary cholesterol. High responders, but not low responders, developed liver injury as indicated by elevated plasma biomarkers of liver function, probably reflecting damage to the canalicular membrane by bile salts because of impaired phospholipid secretion. Our results implicate ABCB4 as a major determinant of diet-induced hypercholesterolemia in high-responding opossums and suggest that other genes interact with ABCB4 to regulate lipemic response to dietary cholesterol.

γ Glutamyl transferase (GGT) and albumin (ALB) are two markers of liver function. These two proteins have been associated with non-alcoholic fatty liver disease and cardiovascular disease. The objectives of this study were to explore the genetic factors that influence variation in the plasma levels of GGT and ALB and to evaluate their genetic correlations with cardiovascular risk factors. Baboons from the Southwest National Primate Research Center at the Southwest Foundation for Biomedical Research, San Antonio, TX, were used as an animal model. The baboons were fed a standard monkey chow diet ad libitum. Fasting plasma concentrations of GGT, ALB, triglycerides, total cholesterol and LDL cholesterol were measured in 350 pedigreed adult baboons by standard assay procedures. A maximum likelihood-based variance decomposition approach implemented in the computer program SOLAR was used to conduct genetic analyses. The heritabilities of GGT (h2 = 0.55; P < 0.0001) and ALB (h2 = 0.42; P < 0.01) were significant. No statistically significant associations were found between GGT and the cardiovascular-related phenotypes. Genetic correlations between ALB and total cholesterol, LDL cholesterol and triglycerides were significant. A QTL (LOD = 2.8) for GGT plasma levels was identified on the baboon homologue of human chromosome 22 between markers D22S304 and D22S280. A QTL (LOD = 2.3) near marker D10S1432 was detected on the baboon homologue of human chromosome 10 for ALB. These results imply that variations in the plasma levels of GGT and ALB are under significant genetic regulation and that a common genetic component influences ALB and cardiovascular risk factor phenotypes.

Context: Chemerin is a novel adipokine previously associated with metabolic syndrome phenotypes in a small sample of subjects from Mauritius. Objective: The aim of the study was to determine whether plasma chemerin levels were associated with metabolic syndrome phenotypes in a larger sample from a second, unrelated human population. Design, Setting, Patients, and Intervention: Plasma samples were obtained from the San Antonio Family Heart Study (SAFHS), a large family-based genetic epidemiological study including 1431 Mexican-American individuals. Individuals were randomly sampled without regard to phenotype or disease status. This sample is well-characterized for a variety of phenotypes related to the metabolic syndrome. Main Outcomes: Plasma chemerin levels were measured by sandwich ELISA. Linear regression and correlation analyses were used to determine associations between plasma chemerin levels and metabolic syndrome phenotypes. Results: Circulating chemerin levels were significantly higher in nondiabetic subjects with body mass index (BMI) greater than 30 kg/m2 compared with those with a BMI below 25 kg/m2 (P < 0.0001). Plasma chemerin levels were significantly associated with metabolic syndrome-related parameters, including BMI (P < 0.0001), fasting serum insulin (P < 0.0001), triglycerides (P < 0.0001), and high-density lipoprotein cholesterol (P = 0.00014), independent of age and sex in nondiabetic subjects. Conclusion: Circulating chemerin levels were associated with metabolic syndrome phenotypes in a second, unrelated human population. This replicated result using a large human sample suggests that chemerin may be involved in the development of the metabolic syndrome.

Genetic effects on mechanical properties have been demonstrated in rodents, but not confirmed in primates. Our aim was to quantify the proportion of variation in vertebral trabecular bone mechanical properties that is due to the effects of genes. L3 vertebrae were collected from 110 females and 46 male baboons (6-32 years old) from a single extended pedigree. Cranio-caudally oriented trabecular bone cores were scanned with microCT then tested in monotonic compression to determine apparent ultimate stress, modulus, and toughness. Age and sex effects and heritability (h(2)) were assessed using maximum likelihood-based variance components methods. Additive effects of genes on residual trait variance were significant for ultimate stress (h(2)=0.58), toughness (h(2)=0.64), and BV/TV (h(2)=0.55). When BV/TV was accounted for, the residual variance in ultimate stress accounted for by the additive effects of genes was no longer significant. Toughness, however, showed evidence of a non-BV/TV-related genetic effect. Overall, maximum stress and modulus show strong genetic effects that are nearly entirely due to bone volume. Toughness shows strong genetic effects related to bone volume and shows additional genetic effects (accounting for 10% of the total trait variance) that are independent of bone volume. These results support continued use of bone volume as a focal trait to identify genes related to skeletal fragility, but also show that other focal traits related to toughness and variation in the organic component of bone matrix will enhance our ability to find additional genes that are particularly relevant to fatigue-related fractures.

Background Serum bone-specific alkaline phosphatase (bone ALP) and intact osteocalcin (OC) are markers of bone formation of interest because of easy measurability and potential utility as identifiers of those at risk for fractures associated with bone metabolism disorders. The baboon (Papio hamadryas) exhibits extensive biological similarities to humans making it particularly well suited to studies of bone maintenance and turnover. Methods We measured serum bone ALP and OC in 591 baboons. Results We report significant sex and age effects and present reference ranges and percentile distributions for these markers. Conclusions This study is the first to characterize normal variation in bone ALP and OC levels in baboons and to assess the age and sex effects on this variation. The results provide much-needed reference standards to allow researchers to evaluate the status of their animals in cross-sectional studies and assess the meaning of changes in bone ALP and OC levels in longitudinal studies.

Thyroid hormones play major roles in the regulation of a wide range of metabolic and physiologic processes, but the genes and environmental factors that affect normal, quantitative variation in thyroid hormone concentrations are largely unknown. Using quantitative genetic methods, we evaluated the effects of genes and environmental factors on thyroid hormone variation in 586 women and 425 men from 27 randomly ascertained Mexican-American families from the San Antonio Family Heart Study. Data were available on free and total T(4), free and total T(3), TSH, thyroglobulin, and T(4)-binding globulin, as well as on covariates, including sex, age, weight, lifestyle habits, physical activity, and others. These covariates accounted for 2-18% of total phenotypic variation, whereas genes accounted for 26-64% of the variation. Overall, free T(3) had the highest heritability, which is noteworthy because it is the most biologically active thyroid hormone and accounts for the vast majority of metabolic and physiologic effects of thyroid hormones. Our results indicate that genes account for a substantial portion of variation in human thyroid hormone levels, and suggest that further studies to identify the genes involved in this variation could reveal important insights into the processes that govern thyroid-mediated metabolism.

Background Oxidative stress plays a major role in disease processes such as atherosclerosis and diabetes. Peroxynitrite is a reaction product of nitric oxide (NO) and superoxide and a potent oxidant. The peroxynitrite-mediated tyrosine nitration, which forms nitrotyrosine (NT), is associated with several pathological conditions. Methods We measured plasma NT levels using the HPLC method in 40 Mexican Americans with diabetes, but not taking medications, and 40 age- and sex-matched euglycaemic controls. Results Plasma-free NT levels were not different between subjects with diabetes (11.0 ± 1.7 nmol/l, n = 40) and with non-diabetes (10.4 ± 1.5 nmol/l, n = 40). There was also no association with levels of fasting glucose (r = −0.049, P = 0.663) or 2-h glucose (r = −0.099, P = 0.390). However, females had significantly lower free NT level (7.6 ± 1.4 nmol/l, n = 40) than males (13.8 ± 1.7 nmol/l, n = 40, P = 0.005), which were not affected by age, smoking status, BMI and glucose levels. Conclusions In contrast to some earlier reports, our study shows that diabetes has no effect on plasma NT levels in Mexican Americans. We have also demonstrated lower free NT levels in females than males, which may partly explain the lower risk profile to vascular disease in women.

Osteoporosis is a progressive condition involving structural deterioration of bone tissue, leading to skeletal fragility and an increased susceptibility to fractures due to low bone mass and high rates of bone turnover. Areal bone mineral density (aBMD) serves as the most reliable predictor of susceptibility to osteoporotic fracture. The development of animal models, including Old World Monkeys, has been essential to studies of bone mineral density. These animals, including the baboon, exhibit many biological similarities with our own species relevant to the variation in age-related changes and pathology in bone that may make them an excellent model for studies of skeletal structure and maintenance in humans. The baboon has been shown to exhibit extensive biological similarities to humans regarding skeletal biology, but little is known about the range of normal variation in skeletal traits, such as bone mineral density, in this species. Our data, collected on baboons (Papio hamadryas) that are part of a large breeding colony at the Southwest Foundation for Biomedical Research and the Southwest National Primate Research Center (San Antonio, TX), involve 466 females and 210 males, ranging in age from 5.5 to 30 years. Student's t tests, bivariate correlations, and likelihood ratio tests show sex and age effects at all spinal sites. Age effects are minimal or absent in the forearm sites. This study is the first to characterize normal variation in aBMD in baboons, to assess the effect of age and sex on this variation, and to compare this variation to those data currently available from experimental control animals. As such, it provides much-needed reference standards that will allow researchers to evaluate the status of their animals in cross-sectional studies and more fully assess the meaning of aBMD changes in longitudinal studies.

Serum LDL cholesterol (LDLC) concentrations and ACE activities are risk factors for the development of cardiovascular disease (CVD). However, the relationship between ACE and CVD susceptibility, and possible mechanisms of action, is controversial. With data on 622 pedigreed baboons, we used statistical genetic methods to determine the mode of inheritance of ACE activities and its relationship to LDLC on different diets. ACE activity was moderately heritable, and quantitative trait linkage analyses detected a quantitative trait locus (QTL) for ACE activity on the baboon homolog of human chromosome 17 (near the ACE structural locus, maximum multipoint lod=7.5, genomic P =0.000003). Bivariate analyses revealed that ACE activity was genetically correlated (ρ G ) with LDLC response (LDLC RC ) to a high-cholesterol diet (ρ G =0.30±0.13, P =0.01) but not to LDLC on a basal diet (ρ G =0.08±0.13). Bivariate genetic analyses indicated that a previously detected QTL for LDLC RC had significant ( P =0.025) pleiotropic effects on ACE activity levels and accounted for the genetic correlation. Therefore, we have detected 2 putative loci that affect ACE activity in baboons, one of which also affects LDLC dietary response. The existence of at least 2 genes that affect ACE activity, one of which is diet-responsive, may help explain the lack of consistency among studies of the relationship between ACE and CVD.

Recent studies reported a marked inverse effect of smoking on serum levels of leptin (an adipocyte derived protein), offering a possible explanation for variation in body weight between smokers and non-smokers. The goal of this study was to examine the genetic architecture of the response to smoking in leptin levels using data from the San Antonio Family Heart Study. We employed a variance decomposition analysis using maximum likelihood methods to model genotype by smoking interactions for leptin levels, examined the impact of the exclusion of smokers in a subsequent linkage analysis, and incorporated the QTL identified in the linkage analysis in a model of genotype by smoking interaction. We found significant evidence (P = 0.001) for a genotype by smoking status interaction for serum leptin levels. In the subsequent linkage analysis with smokers excluded, we obtained a maximum LOD score of 3.1 (P = 0.00008) near D8S1102. Using this QTL in a model of genotype by smoking status interaction, we identified significant evidence for an interaction at this specific locus (P = 0.04). Given these results, we hypothesize that a quantitative trait locus in this vicinity of chromosome 8 may have a differential effect on the expression of leptin in smokers versus non-smokers.

Objective: Recent studies have reported the existence of marked sexual dimorphism in serum leptin levels in humans, with women having approximately three times the levels of men. As we have shown for other measures of adiposity, such sexual dimorphism can arise from a special case of genotype by environment interaction, that of genotype by sex interaction. Research Methods and Procedures: Using maximum likelihood-based variance decomposition techniques, we examined the genetic and environmental architecture of sexual dimorphism in serum leptin levels in 1147 Mexican Americans from the San Antonio Family Heart Study. Results: Both the genetic and environmental variances for this trait differed significantly between the sexes (p < 0.001 and p < 0.01, respectively), with women displaying larger values for both components. We found significant evidence that different genes influence variation in serum leptin levels between the two sexes (p = 0.05). Furthermore, this pattern of sexual dimorphism in serum leptin levels persisted even after accounting for the effects of either the percentage of body fat or total body fat. However, this pattern of sexual dimorphism was eliminated after accounting for the effects of testosterone. Discussion: These findings suggest that the sexual dimorphism seen in leptin levels is not simply explained as differences in total adiposity between the sexes. We conclude that the genes, which influence variation in serum leptin levels, are differentially expressed depending on sex, and that the sexes also show differences in response of the expression of this obesity-related trait to unmeasured residual effects.