Body mass index stratified meta-analysis of genome-wide association studies of polycystic ovary syndrome in women of European ancestry.

BACKGROUND: Polycystic ovary syndrome (PCOS) is a complex multifactorial disorder with a substantial genetic component. However, the clinical manifestations of PCOS are heterogeneous with notable differences between lean and obese women, implying a different pathophysiology manifesting in differential body mass index (BMI). We performed a meta-analysis of genome-wide association study (GWAS) data from six well-characterised cohorts, using a case-control study design stratified by BMI, aiming to identify genetic variants associated with lean and overweight/obese PCOS subtypes. RESULTS: The study comprised 254,588 women (5,937 cases and 248,651 controls) from individual studies performed in Australia, Estonia, Finland, the Netherlands and United States of America, and separated according to three BMI stratifications (lean, overweight and obese). Genome-wide association analyses were performed for each stratification within each cohort, with the data for each BMI group meta-analysed using METAL software. Almost half of the total study population (47%, n = 119,584) were of lean BMI (≤ 25 kg/m2). Two genome-wide significant loci were identified for lean PCOS, led by rs12000707 within DENND1A (P = 1.55 × 10-12) and rs2228260 within XBP1 (P = 3.68 × 10-8). One additional locus, LINC02905, was highlighted as significantly associated with lean PCOS through gene-based analyses (P = 1.76 × 10-6). There were no significant loci observed for the overweight or obese sub-strata when analysed separately, however, when these strata were combined, an association signal led by rs569675099 within DENND1A reached genome-wide significance (P = 3.22 × 10-9) and a gene-based association was identified with ERBB4 (P = 1.59 × 10-6). Nineteen of 28 signals identified in previous GWAS, were replicated with consistent allelic effect in the lean stratum. There were less replicated signals in the overweight and obese groups, and only 4 SNPs were replicated in each of the three BMI strata. CONCLUSIONS: Genetic variation at the XBP1, LINC02905 and ERBB4 loci were associated with PCOS within unique BMI strata, while DENND1A demonstrated associations across multiple strata, providing evidence of both distinct and shared genetic features between lean and overweight/obese PCOS-affected women. This study demonstrated that PCOS-affected women with contrasting body weight are not only phenotypically distinct but also show variation in genetic architecture; lean PCOS women typically display elevated gonadotrophin ratios, lower insulin resistance, higher androgen levels, including adrenal androgens, and more favourable lipid profiles. Overall, these findings add to the growing body of evidence supporting a genetic basis for PCOS as well as differences in genetic patterns relevant to PCOS BMI-subtype.

Plasma 25-hydroxyvitamin D level and the risk of frailty among Chinese community-based oldest-old: evidence from the CLHLS study.

BACKGROUND: Vitamin D deficiency has been linked to the risk of frailty. However, there are limited methods for evaluations of the potential association of vitamin D with frailty in a longevous (80+) population. The aim of this study was to examine the association between plasma 25-hydroxyvitamin D [25(OH)D] levels and the risk of frailty among the Chinese community based oldest-old. METHODS: Secondary analysis of data compiled in the 2011 wave of the Chinese Longitudinal Healthy Longevity Survey (n = 1324) was performed. Frailty was assessed by the Study of Osteoporotic Fractures (SOF) index. Multivariate logistic regression and spline smoothing with threshold effect analysis were performed to investigate the association between 25(OH) D level and the risk of frailty after adjusting for socio-demographic variables, health characteristics and confounding biomarkers. RESULTS: The mean age was 92.89 ± 7.92 years, and 844 (63.7%) participants were women. In all, data from 426 (33.2, 95% confidence interval, CI: 29.66-34.69) frail participants were recorded. After adjustment for confounding covariates, the level of 25(OH) D was significantly related to frailty. By spline smoothing with threshold effect analysis, a monotonically negative association between 25(OH) D and frailty was identified. Subgroup analyses revealed that the association did not differ by sex or age. CONCLUSIONS: The 25(OH) D level was inversely associated with the risk of frailty among the Chinese community-based oldest-old.

Association between site-specific bone mineral density and glucose homeostasis and anthropometric traits in healthy men and women.

OBJECTIVE: Patients with type 2 diabetes mellitus have an increased risk of fracture despite normal or increased bone mineral density (BMD). Studies on the relationship of glucose homeostasis with BMD phenotypes have been inconclusive because distinguishing the roles of insulin resistance and hyperglycaemia in bone remodelling is challenging. In this study, we sought to define the relationship of site-specific BMD with glucose homeostasis traits and anthropometric traits. DESIGN/PATIENTS/MEASUREMENTS: In a cross-sectional study, we examined 787 subjects from the Mexican-American Coronary Artery Disease (MACAD) cohort who had undergone euglycaemic-hyperinsulinaemic clamps, oral glucose tolerance testing and dual X-ray absorptiometry. Glucose homeostasis traits included insulinogenic index (IGI30), insulin sensitivity (M value), insulin clearance (MCRI), fasting insulin, fasting glucose and 2-hour glucose. Univariate and multivariate analyses were performed to assess the association of glucose homeostasis and anthropometric traits with site-specific BMD. RESULTS: Two-hour glucose was negatively associated with arm BMD in women, which remained significant in multivariate analysis (ß = -.15, P = .0015). Positive correlations between fasting insulin and BMD at weight-bearing sites, including pelvis (ß = .22, P < .0001) and legs (ß = .17, P = .001) in women and pelvis (ß = .33, P < .0001) in men, lost significance after multivariate adjustment. Lean mass exhibited strong independent positive associations with BMD at multiple sites in both sexes. CONCLUSION: Our findings suggest that (i) anabolic effects of insulin might work via mechanical loading from lean mass; (ii) a direct negative effect of increasing glucose might be more prominent at cortical-bone-rich sites in women; and (iii) lean mass is a strong positive predictor of bone mass.

Systems Genetics Reveals the Functional Context of PCOS Loci and Identifies Genetic and Molecular Mechanisms of Disease Heterogeneity.

Genome wide association studies (GWAS) have revealed 11 independent risk loci for polycystic ovary syndrome (PCOS), a common disorder in young women characterized by androgen excess and oligomenorrhea. To put these risk loci and the single nucleotide polymorphisms (SNPs) therein into functional context, we measured DNA methylation and gene expression in subcutaneous adipose tissue biopsies to identify PCOS-specific alterations. Two genes from the LHCGR region, STON1-GTF2A1L and LHCGR, were overexpressed in PCOS. In analysis stratified by obesity, LHCGR was overexpressed only in non-obese PCOS women. Although not differentially expressed in the entire PCOS group, INSR was underexpressed in obese PCOS subjects only. Alterations in gene expression in the LHCGR, RAB5B and INSR regions suggest that SNPs in these loci may be functional and could affect gene expression directly or indirectly via epigenetic alterations. We identified reduced methylation in the LHCGR locus and increased methylation in the INSR locus, changes that are concordant with the altered gene expression profiles. Complex patterns of meQTL and eQTL were identified in these loci, suggesting that local genetic variation plays an important role in gene regulation. We propose that non-obese PCOS women possess significant alterations in LH receptor expression, which drives excess androgen secretion from the ovary. Alternatively, obese women with PCOS possess alterations in insulin receptor expression, with underexpression in metabolic tissues and overexpression in the ovary, resulting in peripheral insulin resistance and excess ovarian androgen production. These studies provide a genetic and molecular basis for the reported clinical heterogeneity of PCOS.

CRTC3 links catecholamine signalling to energy balance.

The adipose-derived hormone leptin maintains energy balance in part through central nervous system-mediated increases in sympathetic outflow that enhance fat burning. Triggering of ß-adrenergic receptors in adipocytes stimulates energy expenditure by cyclic AMP (cAMP)-dependent increases in lipolysis and fatty-acid oxidation. Although the mechanism is unclear, catecholamine signalling is thought to be disrupted in obesity, leading to the development of insulin resistance. Here we show that the cAMP response element binding (CREB) coactivator Crtc3 promotes obesity by attenuating ß-adrenergic receptor signalling in adipose tissue. Crtc3 was activated in response to catecholamine signals, when it reduced adenyl cyclase activity by upregulating the expression of Rgs2, a GTPase-activating protein that also inhibits adenyl cyclase activity. As a common human CRTC3 variant with increased transcriptional activity is associated with adiposity in two distinct Mexican-American cohorts, these results suggest that adipocyte CRTC3 may play a role in the development of obesity in humans.

Sexually dimorphic DNA methylation and gene expression patterns in human first trimester placenta.

BACKGROUND: Fetal sex and placental development impact pregnancy outcomes and fetal-maternal health, but the critical timepoint of placenta establishment in first trimester is understudied in human pregnancies. METHODS: Pregnant subjects were recruited in late first trimester (weeks 10-14) at time of chorionic villus sampling, a prenatal diagnostic test. Leftover placenta tissue was collected and stored until birth outcomes were known, then DNA and RNA were isolated from singleton, normal karyotype pregnancies resulting in live births. DNA methylation was measured with the Illumina Infinium MethylationEPIC BeadChip array (n = 56). Differential methylation analysis compared 25 females versus 31 males using a generalized linear model on 743,461 autosomal probes. Gene expression sex differences were analyzed with RNA-sequencing (n = 74). An integrated analysis was performed using linear regression to correlate gene expression and DNA methylation in 51 overlapping placentas. RESULTS: Methylation analysis identified 151 differentially methylated probes (DMPs) significant at false discovery rate < 0.05, including 89 (59%) hypermethylated in females. Probe cg17612569 (GABPA, ATP5J) was the most significant CpG site, hypermethylated in males. There were 11 differentially methylated regions affected by fetal sex, with transcription factors ZNF300 and ZNF311 most significantly hypermethylated in males and females, respectively. RNA-sequencing identified 152 genes significantly sexually dimorphic at false discovery rate < 0.05. The 151 DMPs were associated with 18 genes with gene downregulation (P < 0.05) in the direction of hypermethylation, including 2 genes significant at false discovery rate < 0.05 (ZNF300 and CUB and Sushi multiple domains 1, CSMD1). Both genes, as well as Family With Sequence Similarity 228 Member A (FAM228A), showed significant correlation between DNA methylation and sexually dimorphic gene expression, though FAM228A DNA methylation was less sexually dimorphic. Comparison with other sex differences studies found that cg17612569 is male-hypermethylated across gestation in placenta and in human blood up to adulthood. CONCLUSIONS: Overall, sex dimorphic differential methylation with associated differential gene expression in the first trimester placenta is small, but there remain significant genes that may be regulated through methylation leading to differences in the first trimester placenta.

Fetal sex and placenta development affect pregnancy outcomes for both the fetus and mother throughout pregnancy, including risk of miscarriages, preterm birth, preeclampsia, and other outcomes. Epigenetics, the "overlay" of regulatory signals on DNA which affects how DNA is read, is not well understood in early pregnancy when critical placenta developments are happening that affect the rest of pregnancy. Here, we use leftover placenta biopsy samples (n = 56) donated by Cedars-Sinai patients with informed consent to learn about first trimester human placenta DNA methylation differences due to fetal sex. Out of the total 743,461 sites analyzed, we identified 151 sites significantly affected by fetal sex after correcting p-values to reduce false positives (false discovery rate < 0.05). We also performed an analysis to look at multiple sites and identified 11 regions across the genome with significant DNA methylation changes due to fetal sex. Furthermore, because DNA methylation is a regulatory mark on DNA which typically dampens gene expression, we also compared the DNA methylation sex differences to placental RNA-sequencing gene expression analysis using the same tissue from a mostly overlapping patient group (n = 74 total sequenced, n = 51 overlap). We identify 18 genes which show both significant DNA methylation differences and gene expression changes. The most significant gene was transcription factor ZNF300 with higher DNA methylation in males and reduced gene expression in males (and thus higher gene expression in females). This study identifies some sex differences that continue until later pregnancy and others that are unique to first trimester.

Infertility and treatments used have minimal effects on first-trimester placental DNA methylation and gene expression.

OBJECTIVE: To determine whether deoxyribonucleic acid (DNA) methylation alterations exist in the first-trimester human placenta between conceptions using fertility treatments and those that do not and, if so, whether they are the result of underlying infertility or fertility treatments. We also assessed whether significant alterations led to changes in gene expression. DESIGN: We compared DNA methylation of the first-trimester placenta from singleton pregnancies that resulted in live births from unassisted, in vitro fertilization (IVF), and non-IVF fertility treatment (NIFT) conceptions using the Infinium MethylationEPIC BeadChip array. Significant CpG sites were compared with corresponding ribonucleic acid sequencing analysis in similar cohorts to determine whether methylation alterations lead to differences in gene expression. SETTING: Academic medical center. PATIENT(S): A total of 138 singleton pregnancies undergoing chorionic villus sampling resulting in a live birth were recruited for methylation analysis (56 unassisted, 38 NIFT, and 44 IVF conceptions). Ribonucleic acid-sequencing data consisted of 141 subjects (74 unassisted, 33 NIFT, and 34 IVF conceptions) of which 116 overlapped with the methylation cohort. INTERVENTION(S): In vitro fertilization-conceived pregnancy or pregnancy conceived via NIFT, such as ovulation induction and intrauterine insemination. MAIN OUTCOME MEASURE(S): Significant methylation changes at CpG sites after adjustment for multiple comparisons. The secondary outcome was gene expression changes of significant CpG sites. RESULT(S): Of the 741,145 probes analyzed in the placenta, few were significant at Bonferroni <0.05: 185 CpG sites (0.025%) significant in pregnancies conceived with the fertility treatments (NIFT + IVF) vs. unassisted conceptions; 28 in NIFT vs. unassisted; 195 in IVF vs. unassisted; and only 13 (0.0018%) in IVF vs. NIFT conceptions. Of all significant CpG sites combined, 10% (35) were located in genes with suggestive gene expression changes, but none were significant after adjustment for multiple comparisons (ribonucleic acid sequencing false discovery rate <0.05). None of the 13 differentially methylated probes in the IVF vs. NIFT placenta were located in genes with suggestive IVF vs. NIFT gene expression differences. CONCLUSION(S): Underlying infertility is the most significant contributor to the minimal differences in first-trimester placental methylation, and not the specific fertility treatment used, such as IVF.

Heterogeneous effects on type 2 diabetes and cardiovascular outcomes of genetic variants and traits associated with fasting insulin.

Hyperinsulinemia is a complex and heterogeneous phenotype that characterizes molecular alterations that precede the development of type 2 diabetes (T2D). It results from a complex combination of molecular processes, including insulin secretion and insulin sensitivity, that differ between individuals. To better understand the physiology of hyperinsulinemia and ultimately T2D, we implemented a genetic approach grouping fasting insulin (FI)-associated genetic variants based on their molecular and phenotypic similarities. We identified seven distinctive genetic clusters representing different physiologic mechanisms leading to rising FI levels, ranging from clusters of variants with effects on increased FI, but without increased risk of T2D (non-diabetogenic hyperinsulinemia), to clusters of variants that increase FI and T2D risk with demonstrated strong effects on body fat distribution, liver, lipid, and inflammatory processes (diabetogenic hyperinsulinemia). We generated cluster-specific polygenic scores in 1,104,258 individuals from five multi-ancestry cohorts to show that the clusters differed in associations with cardiometabolic traits. Among clusters characterized by non-diabetogenic hyperinsulinemia, there was both increased and decreased risk of coronary artery disease despite the non-increased risk of T2D. Similarly, the clusters characterized by diabetogenic hyperinsulinemia were associated with an increased risk of T2D, yet had differing risks of cardiovascular conditions, including coronary artery disease, myocardial infarction, and stroke. The strongest cluster-T2D associations were observed with the same direction of effect in non-Hispanic Black, Hispanic, non-Hispanic White, and non-Hispanic East Asian populations. These genetic clusters provide important insights into granular metabolic processes underlying the physiology of hyperinsulinemia, notably highlighting specific processes that decouple increasing FI levels from T2D and cardiovascular risk. Our findings suggest that increasing FI levels are not invariably associated with adverse cardiometabolic outcomes.

Systemic soluble tumor necrosis factor receptors 1 and 2 are associated with severity of diabetic retinopathy in Hispanics.

PURPOSE: To investigate the associations of serum amyloid A (SAA) protein and soluble tumor necrosis factor receptors 1 and 2 (sTNF-R1 and sTNF-R2) with diabetic retinopathy (DR) in Hispanics. DESIGN: Prospective, nonrandomized, cross-sectional, family-based observational cohort study. PARTICIPANTS: A total of 473 Hispanic type II diabetic subjects in families ascertained via proband with DR. METHODS: Levels of SAA, sTNF-R1, and sTNF-R2 were measured with enzyme-linked immunosorbent assay. Diabetic retinopathy was assessed by fundus photography and graded using modified Airlie House classification. MAIN OUTCOME MEASURES: Levels of SAA, sTNF-R1, and sTNF-R2 to severity of DR with and without covariates. RESULTS: A direct association of sTNF-R1 (2.37±0.13, 2.15±0.09, 3.09±0.24, 3.25±0.46, 5.02±0.61 ng/ml; P < 0.0001) and sTNF-R2 (6.04±0.20, 6.25±0.52, 7.96±0.70, 8.14±1.13, 14.83±1.68 ng/ml; P < 0.0001) was found for no DR, mild nonproliferative DR (NPDR), moderate NPDR, severe NPDR, and proliferative DR, respectively. These associations remained significant after adjusting for age, gender, body mass index, glycosylated hemoglobin, diabetes duration, systolic blood pressure, and serum creatinine (P < 0.0001 for sTNF-R1 and P=0.0004 for sTNF-R2). A similar pattern was observed when we adjusted for urinary albumin:creatinine ratio in place of serum creatinine (P=0.005 for sTNF-R1 and P=0.02 for sTNF-R2). CONCLUSIONS: Levels of sTNF-R1 and sTNF-R2 are highly correlated with the severity of DR, suggesting that inflammation and insulin resistance may play a critical role in the development of DR. These may be useful biomarkers for DR, aiding in etiologic studies and possibly identifying at-risk patients for active intervention.

Butyrate-Producing Bacteria and Insulin Homeostasis: The Microbiome and Insulin Longitudinal Evaluation Study (MILES).

Gut microbiome studies have documented depletion of butyrate-producing taxa in type 2 diabetes. We analyzed associations between butyrate-producing taxa and detailed measures of insulin homeostasis, whose dysfunction underlies diabetes in 224 non-Hispanic Whites and 129 African Americans, all of whom completed an oral glucose tolerance test. Stool microbiome was assessed by whole-metagenome shotgun sequencing with taxonomic profiling. We examined associations among 36 butyrate-producing taxa (n = 7 genera and 29 species) and insulin sensitivity, insulin secretion, disposition index, insulin clearance, and prevalence of dysglycemia (prediabetes plus diabetes, 46% of cohort), adjusting for age, sex, BMI, and race. The genus Coprococcus was associated with higher insulin sensitivity (ß = 0.14; P = 0.002) and disposition index (ß = 0.12; P = 0.012) and a lower rate of dysglycemia (odds ratio [OR] 0.91; 95% CI 0.85-0.97; P = 0.0025). In contrast, Flavonifractor was associated with lower insulin sensitivity (ß = -0.13; P = 0.004) and disposition index (ß = -0.11; P = 0.04) and higher prevalence of dysglycemia (OR 1.22; 95% CI 1.08-1.38; P = 0.0013). Species-level analyses found 10 bacteria associated with beneficial directions of effects and two bacteria with adverse associations on insulin homeostasis and dysglycemia. Although most butyrate producers analyzed appear to be metabolically beneficial, this is not the case for all such bacteria, suggesting that microbiome-directed therapeutic measures to prevent or treat diabetes should be targeted to specific butyrate-producing taxa rather than all butyrate producers.

Fasting insulin reflects heterogeneous physiological processes: role of insulin clearance.

Several processes contribute to variation in fasting insulin concentration, including fasting glucose, insulin resistance, insulin secretion, and insulin clearance. Our goal was to determine the relative contribution of each of these insulin-related traits, plus anthropometric parameters, to fasting insulin among 470 Mexican Americans. The euglycemic hyperinsulinemic clamp yielded insulin sensitivity (M value) and metabolic clearance rate of insulin (MCRI). Acute insulin secretion was estimated by the insulinogenic index (IGI30) from the oral glucose tolerance test. Regression (univariate) and generalized estimating equations (multivariate) were used to describe the relationship of insulin-related traits to fasting insulin. Univarate analyses were used to select which traits to include in the multivariate model. In multivariate analysis, MCRI, M, BMI, waist circumference, and fasting glucose were independently associated with fasting insulin. Decreasing M and MCRI were associated with increasing fasting insulin, whereas increasing BMI, waist circumference, and fasting glucose were associated with increasing fasting insulin. Standardized coefficients allowed determination of the relative strength of each trait's association with fasting insulin in the entire cohort (strongest to weakest): MCRI (-0.35, P < 0.0001), M (-0.24, P < 0.0001), BMI (0.20, P = 0.0011), waist circumference (0.16, P = 0.021), and fasting glucose (0.11, P = 0.014). Fasting insulin is a complex phenotype influenced by several independent processes, each of which might have its own environmental and genetic determinants. One of the most associated traits was insulin clearance, which has implications for studies that have used fasting insulin as a surrogate for insulin resistance.

Genome-wide association study identifies variants associated with histologic features of nonalcoholic Fatty liver disease.

BACKGROUND & AIMS: Little data are available from genome-wide association studies (GWASs) of liver histology in patients with nonalcoholic fatty liver disease (NAFLD). We conducted a pilot GWAS in patients with NAFLD, characterized by histology, who were enrolled in the NASH Clinical Research Network (CRN) Database Study. METHODS: We studied clinical, laboratory, and histologic data from 236 non-Hispanic white women with NAFLD. We analyzed 324,623 single nucleotide polymorphisms (SNPs) from the 22 autosomal chromosomes. Multivariate-adjusted logistic regression analyses were conducted for binary outcomes, and linear regression analysis was applied for quantitative traits. A P value < 1 × 10(-6) was considered to be significant. RESULTS: In multivariate models adjusted for age, body mass index, diabetes, waist/hip ratios, and levels of glycated hemoglobin, the NAFLD activity score was associated with the SNP rs2645424 on chromosome 8 in farnesyl diphosphate farnesyl transferase 1 (FDFT1) (P = 6.8 × 10(-7)). The degree of fibrosis was associated with the SNP rs343062 on chromosome 7 (P = 2.7 × 10(-8)). SNPs associated with lobular inflammation included SNP rs1227756 on chromosome 10 in COL13A1 (P = 2.0 × 10(-7)), rs6591182 on chromosome 11 (P = 8.6 × 10(-7)), and rs887304 on chromosome 12 in EFCAB4B (P = 7.7 × 10(-7)). SNPs associated with serum levels of alanine aminotransferase included rs2499604 on chromosome 1 (P = 2.2 × 10(-6)), rs6487679 on chromosome 12 in PZP (P = 1.3 × 10(-6)), rs1421201 on chromosome 18 (P = 1.0 × 10(-5)), and rs2710833 on chromosome 4 (P = 6.3 × 10(-7)). No significant associations were observed between genotypes and steatosis, ballooning degeneration, portal inflammation, or other features of NAFLD. CONCLUSIONS: A GWAS significantly associated genetic variants with features of hepatic histology in patients with NAFLD. These findings should be validated in larger and more diverse cohorts.

Combined influence of LDLR and HMGCR sequence variation on lipid-lowering response to simvastatin.

OBJECTIVE: Although statins are efficacious for lowering low-density lipoprotein cholesterol, there is wide interindividual variation in response. We tested the extent to which combined effects of common alleles of LDLR and HMGCR can contribute to this variability. METHODS AND RESULTS: Haplotypes in the LDLR 3'-untranslated region (3-UTR) were tested for association with lipid-lowering response to simvastatin treatment in the Cholesterol and Pharmacogenetics trial (335 blacks and 609 whites). LDLR haplotype 5 (LDLR L5) was associated with smaller simvastatin-induced reductions in low-density lipoprotein cholesterol, total cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B (P=0.0002 to 0.03) in blacks but not whites. The combined presence of LDLR L5 and previously described HMGCR haplotypes in blacks was associated with significantly attenuated apolipoprotein B reduction (-22.4+/-1.5%, N=89) compared with both noncarriers (-30.6+/-1.5%, N=78, P=0.0001) and carriers of either individual haplotype (-28.2+/-1.1%, N=158, P=0.001). We observed similar differences when measuring simvastatin-mediated induction of low-density lipoprotein receptor surface expression using lymphoblast cell lines (P=0.03). CONCLUSIONS: We have identified a common LDLR 3-UTR haplotype that is associated with attenuated lipid-lowering response to simvastatin treatment. Response was further reduced in individuals with both LDLR and previously described HMGCR haplotypes. Previously identified racial differences in statin efficacy were partially explained by the greater prevalence of these combined haplotypes in blacks.

Polycystic Ovary Syndrome and Risk of Type 2 Diabetes, Coronary Heart Disease, and Stroke.

Polycystic ovary syndrome (PCOS) has been associated with diabetes and cardiovascular disease; however, whether the relationship is causal is uncertain. We conducted a two-sample Mendelian randomization study to investigate the associations of PCOS with type 2 diabetes, coronary heart disease (CHD), and stroke. Association between PCOS and diabetes risk was examined in European and Asian cohorts, both sex specific and sex combined. Causal effects of PCOS on risks of CHD and stroke were evaluated in European cohorts. Stroke was analyzed as any stroke as well as four subtypes of stroke (ischemic, large artery, cardioembolic, small vessel). We found no association of genetically predicted PCOS with risk of diabetes, CHD, or stroke. This suggests that PCOS in and of itself does not increase the risk of these outcomes. Other features of PCOS (obesity, elevated testosterone, low sex hormone binding globulin) may explain the association between PCOS and cardiometabolic diseases. In light of these results, efforts to prevent cardiometabolic complications in PCOS should focus on women with high-risk features rather than all women with PCOS.

Physical Activity Associations with Bone Mineral Density and Modification by Metabolic Traits.

OBJECTIVE: To assess the relationship of physical activity with bone mineral density (BMD) at various sites and examine potential modifying metabolic factors. METHODS: Responses from physical activity questionnaires were used to determine total physical activity (PA), moderate physical activity (mod-PA), and sedentary time. Regression analyses were performed to evaluate association of activity traits with insulin sensitivity by euglycemic clamp, adiponectin, C-reactive protein (CRP), and plasminogen activator inhibitor-1 (PAI-1) in 741 healthy subjects. RESULTS: The cohort was relatively sedentary. Activity level was associated with arm, pelvis, and leg BMD in univariate analyses. In multivariate association analyses of arm BMD, only female sex (ß = -0.73, P < 0.0001) and adiponectin (ß = -0.076, P = 0.0091) were significant. Multivariate analyses of pelvis BMD found independent associations with body mass index (BMI) (ß = 0.33, P < 0.0001), adiponectin (ß = -0.10, P = 0.013), female sex (ß = -0.18, P < 0.0001), sedentary time (ß = -0.088, P = 0.034), PA (ß = 0.11, P = 0.01), and mod-PA (ß = 0.11, P = 0.014). Age (ß = -0.10, P = 0.0087), female sex (ß = -0.63, P < 0.0001), BMI (ß = 0.24, P < 0.0001), and mod-PA (ß = 0.10, P = 0.0024) were independently associated with leg BMD. CONCLUSIONS: These results suggest that BMD increases with physical activity in the arms, legs, and pelvis and is inversely related to sedentary time in the pelvis and legs; these associations may be modified by age, sex, BMI, and adiponectin, depending on the site, with physical activity being more important to pelvis and leg BMD than arm BMD and sedentary time being important for pelvis BMD. Moreover, we demonstrated that CRP, PAI-1, and insulin sensitivity play a minor role in BMD.

Classification of Type 2 Diabetes Genetic Variants and a Novel Genetic Risk Score Association With Insulin Clearance.

CONTEXT: Genome-wide association studies have identified more than 450 single nucleotide polymorphisms (SNPs) for type 2 diabetes (T2D). OBJECTIVE: To facilitate use of these SNPs in future genetic risk score (GRS)-based analyses, we aimed to classify the SNPs based on physiology. We also sought to validate GRS associations with insulin-related traits in deeply phenotyped Mexican Americans. DESIGN, SETTING, AND PARTICIPANTS: A total of 457 T2D SNPs from the literature were assigned physiologic function based on association studies and cluster analyses. All SNPs (All-GRS), beta-cell (BC-GRS), insulin resistance (IR-GRS), lipodystrophy (Lipo-GRS), and body mass index plus lipids (B + L-GRS) were evaluated for association with diabetes and indices of insulin secretion (from oral glucose tolerance test), insulin sensitivity and insulin clearance (from euglycemic clamp), and adiposity and lipid markers in 1587 Mexican Americans. RESULTS: Of the 457 SNPs, 52 were classified as BC, 30 as IR, 12 as Lipo, 12 as B + L, whereas physiologic function of 351 was undefined. All-GRS was strongly associated with T2D. Among nondiabetic Mexican Americans, BC-GRS was associated with reduced insulinogenic index, IR-GRS was associated with reduced insulin sensitivity, and Lipo-GRS was associated with reduced adiposity. B + L-GRS was associated with increased insulin clearance. The latter did not replicate in an independent cohort wherein insulin clearance was assessed by a different method. CONCLUSIONS: Supporting their utility, BC-GRS, IR-GRS, and Lipo-GRS, based on SNPs discovered largely in Europeans, exhibited expected associations in Mexican Americans. The novel association of B + L-GRS with insulin clearance suggests that impaired ability to reduce insulin clearance in compensation for IR may play a role in the pathogenesis of T2D. Whether this applies to other ethnic groups remains to be determined.

Adiposity-Independent Effects of Aging on Insulin Sensitivity and Clearance in Mice and Humans.

OBJECTIVE: Aging is associated with impaired insulin sensitivity and increased prevalence of type 2 diabetes. However, it remains unclear whether aging-associated insulin resistance is due to increased adiposity or other age-related factors. To address this question, the impact of aging on insulin sensitivity was investigated independently of changes in body composition. METHODS: Cohorts of mice aged 4 to 8 months ("young") and 18 to 27 months ("aged") exhibiting similar body composition were characterized for glucose metabolism on chow and high-fat diets. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analyses. The relationship between aging and insulin resistance in humans was investigated in 1,250 nondiabetic Mexican Americans who underwent hyperinsulinemic-euglycemic clamps. RESULTS: In mice with similar body composition, age had no detrimental effect on plasma glucose and insulin levels. While aging did not diminish glucose tolerance, hyperinsulinemic-euglycemic clamps demonstrated impaired insulin sensitivity and reduced insulin clearance in aged mice on chow and high-fat diets. Consistent with results in the mouse, age remained an independent determinant of insulin resistance after adjustment for body composition in Mexican American males. CONCLUSIONS: This study demonstrates that in addition to altered body composition, adiposity-independent mechanisms also contribute to aging-associated insulin resistance in mice and humans.

Genetic Risk Score in Diabetes Associated With Chronic Pancreatitis Versus Type 2 Diabetes Mellitus.

INTRODUCTION: Diabetes mellitus (DM) is a complication of chronic pancreatitis (CP). Whether pancreatogenic diabetes associated with CP-DM represents a discrete pathophysiologic entity from type 2 DM (T2DM) remains uncertain. Addressing this question is needed for development of specific measures to manage CP-DM. We approached this question from a unique standpoint, hypothesizing that if CP-DM and T2DM are separate disorders, they should be genetically distinct. To test this hypothesis, we sought to determine whether a genetic risk score (GRS) based on validated single nucleotide polymorphisms for T2DM could distinguish between groups with CP-DM and T2DM. METHODS: We used 60 T2DM single nucleotide polymorphisms to construct a weighted GRS in 1,613 subjects from the North American Pancreatitis Study 2 and 2,685 subjects from the Multi-Ethnic Study of Atherosclerosis, all of European origin. RESULTS: The mean GRS was identical between 321 subjects with CP-DM and 423 subjects with T2DM (66.53 vs 66.42, P = 0.95), and the GRS of both diabetic groups was significantly higher than that of nondiabetic controls (n = 3,554, P < 0.0001). Exploratory analyses attempting to enrich the CP-DM group for pancreatogenic diabetes, such as eliminating diabetes diagnosed before CP, requiring pancreas-specific comorbidities, or removing those with a family history of diabetes, did not improve the ability of the GRS to distinguish between CP-DM and T2DM. DISCUSSION: Recognizing that we lacked a gold standard to define CP-DM, our study suggests that CP-DM may be a subtype of T2DM, a notion that should be tested in future, large prospective studies.

Haplotypes in the lipoprotein lipase gene influence fasting insulin and discovery of a new risk haplotype.

CONTEXT: Prior studies of Mexican Americans described association of lipoprotein lipase (LPL) gene haplotypes with insulin sensitivity/resistance and atherosclerosis. The most common haplotype (haplotype 1) was protective, whereas the fourth most common haplotype (haplotype 4) conferred risk for insulin resistance and atherosclerosis. OBJECTIVE: In this study of Hispanics in the Insulin Resistance Atherosclerosis Study Family Study, we sought to replicate LPL haplotype association with insulin sensitivity/resistance. DESIGN: LPL haplotypes based on 12 single nucleotide polymorphisms were analyzed for association with indexes of insulin sensitivity and other metabolic and adiposity measures. SETTING: This study was conducted in the general community of San Antonio, Texas, and San Luis Valley, Colorado. PARTICIPANTS: Participants in this study were 978 members of 86 Hispanic families. MAIN OUTCOME MEASURES: LPL haplogenotype, metabolic phenotypes, and adiposity were measured in this study. RESULTS: The haplotype structure was identical with that observed in prior studies. Among 978 phenotyped subjects, haplotype 1 was associated with decreased fasting insulin (P = 0.01), and haplotype 4 was associated with increased fasting insulin (P = 0.02) and increased visceral fat mass (P = 0.002). Insulin sensitivity, derived from iv glucose tolerance testing, tended (P > 0.1) to be higher with haplotype 1 (S(I) = 1.72) and lower with haplotype 4 (S(I)=1.38). Haplotype 2 was associated with increases in fasting insulin, triglycerides (TGs), TG to high-density lipoprotein-cholesterol ratio, and apolipoprotein B (P = 0.01-0.04). CONCLUSIONS: This study independently replicates our prior results of LPL haplotypes 1 and 4 as associated with measures of insulin sensitivity and resistance, respectively. Haplotype 4 may confer insulin resistance by increasing visceral fat. Haplotype 2 was identified as a new risk haplotype, suggesting the complex nature of LPL's effect on features of the insulin resistance syndrome.