Search

In the article cited above, the affiliations for authors Stephen J. Pandol and Maike Sander were inadvertently transposed. The correct affiliation for Stephen J. Pandol is Department of Gastroenterology, Cedars-Sinai Medical Center, Los Angeles, CA. The correct affiliation for Maike Sander is Department of Pediatrics and Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA. The online version of the article (https://doi.org/10.2337/db22-0942) has been updated with the correct affiliations.

Fasting insulin (FI) is a heterogeneous trait with high variability between individuals and populations. Increased FI is associated with an increased risk of type 2 diabetes (T2D) and its complications, including coronary artery disease (CAD) and hypertension (HTN) . We hypothesize that we could use a genetic approach to cluster FI-associated variants, characterize the clusters in terms of insulin processes within the Mexican American Cardiovascular Disease Study (MACAD; N=821) , and test for association of polygenic scores (PS) created from these clusters with T2D, CAD and HTN in three cohorts: Mass General Brigham Biobank (MGBB; N=18,127) , Aspirin in Reducing Events in the Elderly (ASPREE; N=13,349) , and Framingham Heart Study (FHS; N=7,145) . We identified six clusters using a soft clustering approach with 446 FI-increasing genetic alleles and 27 FI-related traits. Associations in two of the clusters, allowed us to characterize them and show their impact on T2D and T2D-associated complications. The first cluster had alleles associated with increased subcutaneous and visceral adiposity and was characterized by reduced insulin sensitivity (from euglycemic clamp; P=0.02) , increased insulin secretion (from oral glucose tolerance test [OGTT]; P=0.04) , and increased insulin clearance (from euglycemic clamp; P=0.02) in MACAD. This cluster’s PS was associated with HTN (MGBB Odds ratio (OR) = 1.04, P=0.013) , T2D (MGBB OR = 1.04, P =0.001) and CAD (MGB OR=1.07, P =0.008; ASPREE OR=1.04, P =0.036) The second cluster had alleles associated with a lipodystrophy phenotype and was characterized by increased insulin secretion (from OGTT P =0.019) in MACAD. We observed associations of the PS with T2D (MGBB OR= 1.13, P =2.3x10-10) and HTN (MGBB OR = 1.06, P =0.001) which were replicated in ASPREE and FHS. Our results suggest the presence of two different FI-associated genetic domains and elucidate the deleterious mechanisms by which increased FI is associated with T2D and T2D complications. Disclosure M.Sevilla: None. M.O.Goodarzi: None. D.A.Dicorpo: None. J.I.Rotter: None. J.B.Meigs: Consultant; Quest Diagnostics. M.Udler: None. A.Manning: None. Funding UM1DK078616

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 between 36 butyrate-producing taxa (7 genera, 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, body mass index, and race. Genus Coprococcus was associated with higher insulin sensitivity (β=0.14, P=0.002) and disposition index (β=0.12, P=0.012) and a lower rate of dysglycemia (odds ratio 0.91, 95% confidence interval (CI) 0.85-0.97, P=0.0025); in contrast, Flavonifractor was associated with lower insulin sensitivity (β=-0.13, P=0.004) and disposition index (β=-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. While 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.

Nontargeted metabolomics methods have increased potential to identify new disease biomarkers, but assessments of the additive information provided in large human cohorts by these less biased techniques are limited. To diversify our knowledge of diabetes associated metabolites, we leveraged a method that measures 305 targeted or “known” and 2,342 nontargeted or “unknown” compounds in fasting plasma samples from 2,750 participants (315 incident cases) in the Jackson Heart Study (JHS)—a community cohort of self-identified African Americans (AAs), who are underrepresented in omics studies. We found 307 unique compounds (82 known) associated with diabetes after adjusting for age and sex at a false discovery rate (FDR)

Several studies have compared the stool microbiomes of people with and without type 2 diabetes (T2D), from which a pattern of depletion of butyrate producing taxa in T2D has emerged. Seventeen taxa encompass ~85% of the total butyrate producing potential in humans (mSystems 2017;2:e00130). The goal of MILES is to elucidate the effect of diet and gut microbiota on the components of insulin homeostasis (insulin sensitivity, secretion, clearance) whose dysfunction underlies T2D. MILES consists of 224 non-Hispanic Whites and 129 African Americans (mean age 59, 62% female), all of whom have completed an oral glucose tolerance test from which insulin homeostasis traits were calculated. Stool microbiome was assessed by whole metagenome shotgun sequencing (10 Gb depth), with taxonomic profiling using MetaPhlAn3. Spearman correlation was used to assess associations between the 17 dominant butyrate producing taxa (8 genera, 9 species) and insulin sensitivity, insulin secretion, disposition index (product of insulin sensitivity and insulin secretion), and insulin clearance. The Wilcoxon test was used to associate taxa with dysglycemia (prediabetes plus diabetes, 46% of cohort). Genera Coprococcus was associated with higher insulin sensitivity (ρ=0.16, P=0.003) and disposition index (ρ=0.14, P=0.009) and a lower rate of dysglycemia. Flavonifractor was associated with lower insulin sensitivity (ρ=-0.17, P=0.002) and a higher rate of dysglycemia. Eubacterium hallii was associated with insulin sensitivity (ρ=0.12, P=0.02). Analysis of 27 species from the 8 genera revealed additional associations with insulin sensitivity and disposition index, most of which displayed positive associations with these traits. These data suggest that improved insulin sensitivity and improved insulin secretion response to insulin sensitivity (i.e., disposition index) are key mechanisms whereby butyrate producing bacteria may exert metabolic protection against T2D. Disclosure J. Cui: None. M. O. Goodarzi: None. T. Zhu: None. E. T. Jensen: None. O. L. Crago: None. G. Ramesh: None. K. M. Sandow: None. Y. Chen: None. J. I. Rotter: None. J. Petrosino: None. Funding National Institutes of Health (R01DK109588)

Insulin resistance and insufficient insulin secretion lead to type 2 diabetes. A role of reduced insulin clearance has been suggested, but few studies have investigated the contribution of insulin clearance while simultaneously examining insulin sensitivity and secretion. The goal of this study was to conduct such an investigation in 224 non-Hispanic White and 129 African Americans individuals from MILES (mean age 59, 62% female). Participants underwent oral glucose tolerance tests from which insulin sensitivity, insulin secretion, insulin clearance, and disposition index were calculated. Logistic regression models (controlling for age, sex, race, and BMI) examined the individual contributions of these traits separately, as well as the joint contribution of insulin sensitivity, clearance, and secretion, to early dysglycemia (prediabetes plus newly diagnosed diabetes; 46% of cohort). Models used standardized predictors such that odds ratios (OR) represent the change in odds of dysglycemia per standard deviation change. Model performance was assessed via Akaike’s Information Criterion (AIC) and area under the receiver operator characteristic curves (AUROC). In separate models, dysglycemia was associated with insulin sensitivity (OR 0.2; 0.14-0.30; P Disclosure A. Wood: None. E. T. Jensen: None. G. Ramesh: None. Z. Arzumanyan: None. K. Lam: None. A. Bertoni: None. J. I. Rotter: None. Y. Chen: None. M. O. Goodarzi: None. Funding National Institutes of Health (R01DK109588)

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.

Background: People with new-onset diabetes face higher risk of pancreatic cancer (PC). However, data on PC risk in people with more advanced stages of diabetes are lacking. We aimed to identify factors associated with PC among people with progressing diabetes. Methods: We conducted a retrospective cohort study on veterans aged ≥50, who were treated with either combination oral hypoglycemic therapy (n=578,543) or insulin (n=609,687) at the VA in 2000-2016. Incident PC was determined through the electronic health records and cancer registries. We examined the association of multiple risk factors with PC using Cox regression analyses. Results: In both people initiating combination therapy and in those initiating insulin, increasing age, male sex, non-Hispanic ancestry, current smoking, acute and chronic pancreatitis, abdominal pain, alcoholism, increase in A1c, and decrease in weight were associated with increased risk of PC (Table). Based on the multivariable model, we can identify sub-populations with ≥5% risk of PC, such as ≥75 year-old non-Hispanic white males initiating insulin who have a history of alcoholism, and who show ≥2% increase in A1c and ≥15% decrease in weight prior to insulin initiation. Conclusion: We identified risk factors associated with PC among people initiating combination oral hypoglycemics or insulin, which may be useful for stratifying people who may benefit from screening for PC. Disclosure C.Y. Jeon: None. M.O. Goodarzi: None. Y. Lin: None. S. Kim: None. T. Moin: None. J.R. Pisegna: None. Funding National Cancer Institute (R21CA220073)

Type 2 diabetes (T2D) is a heterogeneous disorder with contributions from peripheral insulin resistance and β-cell dysfunction. For minimization of phenotypic heterogeneity, quantitative intermediate phenotypes characterizing basal glucose homeostasis (insulin resistance and HOMA of insulin resistance [HOMAIR] and of β-cell function [HOMAB]) have shown promise in relatively large samples. We investigated the utility of dynamic measures of glucose homeostasis (insulin sensitivity [SI] and acute insulin response [AIRg]) evaluating T2D-susceptibility variants (n = 57) in Hispanic Americans from the GUARDIAN Consortium (n = 2,560). Basal and dynamic measures were genetically correlated (HOMAB-AIRg: ρG = 0.28–0.73; HOMAIR-SI: ρG = −0.73 to −0.83) with increased heritability for the dynamic measure AIRg. Significant association of variants with dynamic measures (P < 8.77 × 10−4) was observed. A pattern of superior performance of AIRg was observed for well-established loci including MTNR1B (P = 9.46 × 10−12), KCNQ1 (P = 1.35 × 10−4), and TCF7L2 (P = 5.10 × 10−4) with study-wise statistical significance. Notably, significant association of MTNR1B with AIRg (P < 1.38 × 10−9) was observed in a population one-fourteenth the size of the initial discovery cohort. These observations suggest that basal and dynamic measures provide different views and levels of sensitivity to discrete elements of glucose homeostasis. Although more costly to obtain, dynamic measures yield significant results that could be considered physiologically “closer” to causal pathways and provide insight into the discrete mechanisms of action.

We assessed the relationship of physical activity with BMD at various sites (by DEXA), and examined potential modifying factors, including insulin sensitivity by euglycemic clamp in 765 healthy subjects. Responses from physical activity questionnaires were used to determine total physical activity (PA), moderate physical activity (mod-PA), and sedentary time. Neither activity nor sedentary time correlated with rib, L-spine, or T-spine BMD in univariate analysis (Table). Significant univariate variables were included in multivariate analyses. In multivariate analyses of arm BMD, only female sex (β=-0.74, P Disclosure A. Buttan: None. X. Guo: None. Y. Chen: None. W. Hsueh: Advisory Panel; Self; Merck & Co., Inc., AstraZeneca, Novo Nordisk Inc.. J.I. Rotter: None. M.O. Goodarzi: None.

Obesity is linked to type 2 diabetes (T2D) and cardiovascular diseases; however, the underlying molecular mechanisms remain unclear. We aimed to identify obesity-associated molecular features that may contribute to obesity-related diseases. Using circulating monocytes from 1,264 Multi-Ethnic Study of Atherosclerosis (MESA) participants, we quantified the transcriptome and epigenome. We discovered that alterations in a network of coexpressed cholesterol metabolism genes are a signature feature of obesity and inflammatory stress. This network included 11 BMI-associated genes related to sterol uptake (↑LDLR, ↓MYLIP), synthesis (↑SCD, FADS1, HMGCS1, FDFT1, SQLE, CYP51A1, SC4MOL), and efflux (↓ABCA1, ABCG1), producing a molecular profile expected to increase intracellular cholesterol. Importantly, these alterations were associated with T2D and coronary artery calcium (CAC), independent from cardiometabolic factors, including serum lipid profiles. This network mediated the associations between obesity and T2D/CAC. Several genes in the network harbored C-phosphorus-G dinucleotides (e.g., ABCG1/cg06500161), which overlapped Encyclopedia of DNA Elements (ENCODE)-annotated regulatory regions and had methylation profiles that mediated the associations between BMI/inflammation and expression of their cognate genes. Taken together with several lines of previous experimental evidence, these data suggest that alterations of the cholesterol metabolism gene network represent a molecular link between obesity/inflammation and T2D/CAC.

© 2015 by the American Diabetes Association. Insulin sensitivity, insulin secretion, insulin clearance, and glucose effectiveness exhibit strong genetic components, although few studies have examined their genetic architecture or influence on type 2 diabetes (T2D) risk. We hypothesized that loci affecting variation in these quantitative traits influence T2D. We completed a multicohort genome-wide association study to search for loci influencing T2D-related quantitative traits in 4,176 Mexican Americans. Quantitative traits were measured by the frequently sampled intravenous glucose tolerance test (four cohorts) or euglycemic clamp (three cohorts), and random-effects models were used to test the association between loci and quantitative traits, adjusting for age, sex, and admixture proportions (Discovery). Analysis revealed a significant (P < 5.00 3 1028) association at 11q14.3 (MTNR1B) with acute insulin response. Loci with P < 0.0001 among the quantitative traits were examined for translation to T2D risk in 6,463 T2D case and 9,232 control subjects of Mexican ancestry (Translation). Nonparametric meta- Analysis of the Discovery and Translation cohorts identified significant associations at 6p24 (SLC35B3/TFAP2A) with glucose effectiveness/T2D, 11p15 (KCNQ1) with disposition index/T2D, and 6p22 (CDKAL1) and 11q14 (MTNR1B) with acute insulin response/T2D. These results suggest that T2D and insulin secretion and sensitivity have both shared and distinct genetic factors, potentially delineating genomic components of these quantitative traits that drive the risk for T2D.

Glycated hemoglobin A1c(HbA1c) is used as a measure of glycemic control and also as a diagnostic criterion for diabetes. To discover novel loci harboring common variants associated with HbA1cin East Asians, we conducted a meta-analysis of 13 genome-wide association studies (GWAS; N = 21,026). We replicated our findings in three additional studies comprising 11,576 individuals of East Asian ancestry. Ten variants showed associations that reached genome-wide significance in the discovery data set, of which nine (four novel variants at TMEM79 [ P value = 1.3 × 10-23], HBS1L/MYB [8.5 × 10-15], MYO9B [9.0 × 10-12], and CYBA [1.1 × 10-8] as well as five variants at loci that had been previously identified [CDKAL1, G6PC2/ ABCB11, GCK, ANK1, and FN3KI]) showed consistent evidence of association in replication data sets. These variants explained 1.76% of the variance in HbA1c. Several of these variants (TMEM79, HBS1L/MYB, CYBA, MYO9B, ANK1, and FN3K) showed no association with either blood glucose or type 2 diabetes. Among individuals with nondiabetic levels of fasting glucose (

OBJECTIVE The metabolic syndrome (MetS) is defined as concomitant disorders of lipid and glucose metabolism, central obesity, and high blood pressure, with an increased risk of type 2 diabetes and cardiovascular disease. This study tests whether common genetic variants with pleiotropic effects account for some of the correlated architecture among five metabolic phenotypes that define MetS. RESEARCH DESIGN AND METHODS Seven studies of the STAMPEED consortium, comprising 22,161 participants of European ancestry, underwent genome-wide association analyses of metabolic traits using a panel of ∼2.5 million imputed single nucleotide polymorphisms (SNPs). Phenotypes were defined by the National Cholesterol Education Program (NCEP) criteria for MetS in pairwise combinations. Individuals exceeding the NCEP thresholds for both traits of a pair were considered affected. RESULTS Twenty-nine common variants were associated with MetS or a pair of traits. Variants in the genes LPL, CETP, APOA5 (and its cluster), GCKR (and its cluster), LIPC, TRIB1, LOC100128354/MTNR1B, ABCB11, and LOC100129150 were further tested for their association with individual qualitative and quantitative traits. None of the 16 top SNPs (one per gene) associated simultaneously with more than two individual traits. Of them 11 variants showed nominal associations with MetS per se. The effects of 16 top SNPs on the quantitative traits were relatively small, together explaining from ∼9% of the variance in triglycerides, 5.8% of high-density lipoprotein cholesterol, 3.6% of fasting glucose, and 1.4% of systolic blood pressure. CONCLUSIONS Qualitative and quantitative pleiotropic tests on pairs of traits indicate that a small portion of the covariation in these traits can be explained by the reported common genetic variants.

OBJECTIVE—Evaluate type 2 diabetes susceptibility variants identified from genome-wide association studies in Hispanic Americans and African Americans from the Insulin Resistance Atherosclerosis Family Study (IRAS-FS) for association with quantitative measures of glucose homeostasis and determine their biological role in vivo.RESEARCH DESIGN AND METHODS—Seventeen type 2 diabetes–associated single nucleotide polymorphisms (SNPs) were genotyped in 1,268 Hispanic- and 581 African-American participants from the IRAS-FS. SNPs were tested for association with quantitative measures of glucose homeostasis, including insulin sensitivity index (SI), acute insulin response (AIR), and disposition index.RESULTS—Previously identified risk variants in cyclin-dependent kinase 5 regulatory subunit associated protein 1-like 1 (CDKAL1) were associated with reduced AIR (P < 0.0046) in Hispanic Americans. Additionally in Hispanic Americans, the variant in a hypothetical gene (chromosome 11; LOC387761) was significantly associated with AIR (P = 0.0046) with the risk allele showing protective effects, i.e., increased AIR. In both Hispanic- and African-American populations, risk variants at the solute carrier family 30, member 8 (SLC30A8) locus were nominally associated with decreased disposition index (P < 0.078). Risk variants in the insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) locus were associated with a decreased disposition index (P = 0.011) exclusively in Hispanic Americans.CONCLUSIONS—These data indicate a distinct, limited number of diabetes-related genes, more specifically the SNPs in the genes identified in European-derived populations, with modest evidence for association with glucose homeostasis traits in Hispanic Americans and African Americans. We observe evidence that diabetes risk for CDKAL1, SLC30A8, IGF2BP2, and LOC387761 is specifically mediated through defects in insulin secretion. The mechanisms of other predisposing genes remain to be elucidated.

The powerful relation between atherosclerosis and diabetes may have a common genetic basis. However, few genes predisposing to both have been identified. Calpain-10 (CAPN10) was the first gene for type 2 diabetes identified by positional cloning, wherein a combination of haplotypes conferred increased risk of diabetes. We sought to determine whether CAPN10 influences subclinical atherosclerosis. Among nondiabetic subjects from 85 Mexican-American families with a history of coronary artery disease, subclinical atherosclerosis was assessed by common carotid artery intima-media thickness (IMT), insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp, and insulin secretion was estimated by the oral glucose tolerance test. These phenotypes were tested for association with CAPN10 haplotypes. Haplotype 1112 (of single nucleotide polymorphisms [SNPs] 44, 43, 56, and 63) was associated with increased IMT, while haplotype 1221 was associated with decreased IMT. The 112/121 haplotype combination (of SNPs 43, 56, and 63), originally found to confer increased risk for diabetes, was associated with the largest IMT in our study population. CAPN10 was also associated with both insulin sensitivity and insulin secretion. Covariate analysis suggested that CAPN10 affects IMT independently of these diabetes-related phenotypes. The fact that the diabetes gene CAPN10 also influences the risk for atherosclerosis shows that inherited factors may underlie the frequent co-occurrence of these two conditions.

The insulin resistance syndrome is increasingly recognized as a risk factor for cardiovascular disease. Lipoprotein lipase (LPL) is a candidate gene for components of the syndrome. A small number of studies have demonstrated association of single nucleotide polymorphisms within LPL and indirect or surrogate measures of insulin resistance, largely based on glucose and insulin values obtained in the fasting state or during an oral glucose tolerance test. To test directly whether LPL is an insulin resistance gene, we performed the hyperinsulinemic-euglycemic clamp in a large family-based population of Mexican Americans who were genotyped at six polymorphisms in LPL that define the most common haplotypes in the population. LPL haplotypes showed linkage to the glucose infusion rate (GINF), a direct physiologic measurement of insulin sensitivity (P = 0.034). In addition, significant associations with GINF were demonstrated for the most common haplotype (P = 0.031) and the fourth most common haplotype (P = 0.007). Haplotype 1 was associated with insulin sensitivity (mean GINF for haplotype 1 carriers = 383.0 mg/min) and haplotype 4 with insulin resistance (mean GINF for haplotype 4 carriers = 344.3 mg/min). This haplotype-based genetic analysis provides compelling evidence that variation in the LPL gene plays a role in determining insulin resistance in this ethnic group with a high prevalence of the insulin resistance syndrome.

OBJECTIVE—A small number of susceptibility genes for human type 2 diabetes have been identified by candidate gene analysis or positional cloning. Genes found to influence diabetes or related traits in mice are likely to be susceptibility genes in humans. SorCS1 is the gene identified as responsible for the mouse chromosome 19 T2dm2 quantitative trait locus for fasting insulin levels, acting via impaired insulin secretion and increased islet disruption in obese females. Genes that impair compensatory insulin secretion in response to obesity-induced insulin resistance may be particularly relevant to human diabetes. Thus, we sought to determine whether variation in the human SORCS1 gene was associated with diabetes-related traits. RESEARCH DESIGN AND METHODS—We assessed the contribution of variation in SORCS1 to human insulin–related traits in two distinct Mexican-American cohorts. One cohort (the Mexican-American Coronary Artery Disease [MACAD] cohort) consisted of nondiabetic individuals, allowing assessment of genetic association with subclinical intermediate insulin-related traits; the second cohort (the San Antonio Family Diabetes Study [SAFADS]) contained individuals with diabetes, allowing association analyses with overt disease. RESULTS—We first found association of SORCS1 single nucleotide polymorphisms and haplotypes with fasting insulin levels and insulin secretion in the MACAD cohort. Similar to our results in the mice, the genetic association was strongest in overweight women. We then observed association with diabetes risk and age at diagnosis in women of the SAFADS cohort. CONCLUSIONS—Identification of SORCS1 as a novel gene affecting insulin secretion and diabetes risk is likely to provide important insight into the biology of obesity-induced type 2 diabetes.

The powerful relation between atherosclerosis and diabetes may have a common genetic basis. However, few genes predisposing to both have been identified. Calpain-10 (CAPN10) was the first gene for type 2 diabetes identified by positional cloning, wherein a combination of haplotypes conferred increased risk of diabetes. We sought to determine whether CAPN10 influences subclinical atherosclerosis. Among nondiabetic subjects from 85 Mexican-American families with a history of coronary artery disease, subclinical atherosclerosis was assessed by common carotid artery intima-media thickness (IMT), insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp, and insulin secretion was estimated by the oral glucose tolerance test. These phenotypes were tested for association with CAPN10 haplotypes. Haplotype 1112 (of single nucleotide polymorphisms [SNPs] 44, 43, 56, and 63) was associated with increased IMT, while haplotype 1221 was associated with decreased IMT. The 112/121 haplotype combination (of SNPs 43, 56, and 63), originally found to confer increased risk for diabetes, was associated with the largest IMT in our study population. CAPN10 was also associated with both insulin sensitivity and insulin secretion. Covariate analysis suggested that CAPN10 affects IMT independently of these diabetes-related phenotypes. The fact that the diabetes gene CAPN10 also influences the risk for atherosclerosis shows that inherited factors may underlie the frequent co-occurrence of these two conditions.

The rising prevalence of the insulin resistance syndrome in our society necessitates a better understanding of the genetic determinants of all aspects of insulin action and metabolism. We evaluated the heritability of insulin sensitivity and the metabolic clearance rate of insulin (MCRI) as quantified by the euglycemic-hyperinsulinemic clamp in 403 Mexican Americans. We tested the candidate gene AMP deaminase 1 (AMPD1) for association with insulin-related traits because it codes for an enzyme that has the potential to influence multiple aspects of insulin pharmacodynamics. By converting AMP to inosine monophosphate, AMPD1 plays a major role in regulating cellular AMP levels; AMP activates AMP kinase, an enzyme that modulates cellular energy and insulin action. We determined that nine AMPD1 single nucleotide polymorphisms (SNPs) defined two haplotype blocks. Insulin clearance was found to have a higher heritability (h 2 0.58) than fasting insulin (h 2 0.38) or insulin sensitivity (h 2 0.44). The MCRI was associated with AMPD1 SNPs and haplotypes. Insulin clearance is a highly heritable trait, and specific haplotypes within the AMPD1 gene, which encodes a skeletal musclespecific protein, are associated with variation in insulin clearance. We postulated that the processes of insulin action and insulin clearance in skeletal muscle are highly regulated and that AMPD1 function may play an important role in these phenomena. Diabetes 54: 1222–1227, 2005