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Distinct tissue-specific mechanisms mediate insulin action in fasting and postprandial states. Previous genetic studies have largely focused on insulin resistance in the fasting state, where hepatic insulin action dominates. Here we studied genetic variants influencing insulin levels measured 2 h after a glucose challenge in >55,000 participants from three ancestry groups. We identified ten new loci (P< 5 × 10−8) not previously associated with postchallenge insulin resistance, eight of which were shown to share their genetic architecture with type 2 diabetes in colocalization analyses. We investigated candidate genes at a subset of associated loci in cultured cells and identified nine candidate genes newly implicated in the expression or trafficking of GLUT4, the key glucose transporter in postprandial glucose uptake in muscle and fat. By focusing on postprandial insulin resistance, we highlighted the mechanisms of action at type 2 diabetes loci that are not adequately captured by studies of fasting glycemic traits.

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Although a westernized lifestyle was associated with increased coronary heart disease (CHD), morbidity, and mortality in first- and second-generation Japanese Americans, CHD mortality was reported to be lower in this population than in whites. The risk profile of CHD for third- and fourth-generation Japanese Americans is not known. We compared the progression of carotid intima-media thickness (CIMT) between third- or fourth-generation Japanese Americans and whites.

Objective: Although a significant positive association of vitamin D deficiency with coronary heart disease has been demonstrated in cross-sectional as well as prospective studies, only a few studies have examined the association of vitamin D deficiency with subclinical atherosclerosis. We examined whether vitamin D deficiency is associated with subclinical atherosclerosis, as measured by coronary artery calcification (CAC) in asymptomatic adults.Methods: In a population-based cross-sectional study, 195 men aged 40 to 49 years without cardiovascular disease were randomly selected (98 Caucasian and 97 Japanese American men). Liquid chromatography–tandem mass spectrometry was utilized to measure serum vitamin D. CAC was examined by electron beam computed tomography using standardized protocols and read centrally at the University of Pittsburgh using Agatston's methods. To investigate an association between vitamin D deficiency (defined as 25-hydroxyvitamin D [25(OH)D] < 20 ng/mL) and CAC (defined as Agatston score ≥ 10), we utilized multivariable logistic regression models.Results: Prevalence of CAC and vitamin D deficiency was 27.2% and 10.3%, respectively. Participants with CAC were significantly older, had significantly higher body mass index (BMI), and had higher rates of smoking. Those with CAC were 3.31 times likely to be vitamin D deficient, after adjusting for traditional cardiovascular risk factors (odds ratio [OR] = 3.31, 95% confidence interval [CI], 1.12–9.77).Conclusions: In this population-based study of healthy middle-aged men, vitamin D deficiency had a significant positive association with the presence of CAC.