Mendelian randomization analyses suggest a causal role for circulating GIP and IL-1RA levels in homeostatic model assessment-derived measures of ß-cell function and insulin sensitivity in Africans without type 2 diabetes.

BACKGROUND: In vitro and in vivo studies have shown that certain cytokines and hormones may play a role in the development and progression of type 2 diabetes (T2D). However, studies on their role in T2D in humans are scarce. We evaluated associations between 11 circulating cytokines and hormones with T2D among a population of sub-Saharan Africans and tested for causal relationships using Mendelian randomization (MR) analyses. METHODS: We used logistic regression analysis adjusted for age, sex, body mass index, and recruitment country to regress levels of 11 cytokines and hormones (adipsin, leptin, visfatin, PAI-1, GIP, GLP-1, ghrelin, resistin, IL-6, IL-10, IL-1RA) on T2D among Ghanaians, Nigerians, and Kenyans from the Africa America Diabetes Mellitus study including 2276 individuals with T2D and 2790 non-T2D individuals. Similar linear regression models were fitted with homeostatic modelling assessments of insulin sensitivity (HOMA-S) and ß-cell function (HOMA-B) as dependent variables among non-T2D individuals (n = 2790). We used 35 genetic variants previously associated with at least one of these 11 cytokines and hormones among non-T2D individuals as instrumental variables in univariable and multivariable MR analyses. Statistical significance was set at 0.0045 (0.05/11 cytokines and hormones). RESULTS: Circulating GIP and IL-1RA levels were associated with T2D. Nine of the 11 cytokines and hormones (exceptions GLP-1 and IL-6) were associated with HOMA-S, HOMA-B, or both among non-T2D individuals. Two-stage least squares MR analysis provided evidence for a causal effect of GIP and IL-RA on HOMA-S and HOMA-B in multivariable analyses (GIP ~ HOMA-S ß = - 0.67, P-value = 1.88 × 10-6 and HOMA-B ß = 0.59, P-value = 1.88 × 10-5; IL-1RA ~ HOMA-S ß = - 0.51, P-value = 8.49 × 10-5 and HOMA-B ß = 0.48, P-value = 5.71 × 10-4). IL-RA was partly mediated via BMI (30-34%), but GIP was not. Inverse variance weighted MR analysis provided evidence for a causal effect of adipsin on T2D (multivariable OR = 1.83, P-value = 9.79 × 10-6), though these associations were not consistent in all sensitivity analyses. CONCLUSIONS: The findings of this comprehensive MR analysis indicate that circulating GIP and IL-1RA levels are causal for reduced insulin sensitivity and increased ß-cell function. GIP's effect being independent of BMI suggests that circulating levels of GIP could be a promising early biomarker for T2D risk. Our MR analyses do not provide conclusive evidence for a causal role of other circulating cytokines in T2D among sub-Saharan Africans.

Demographic and sociocultural risk factors for adulthood weight gain in Hispanic/Latinos: results from the Hispanic Community Health Study / Study of Latinos (HCHS/SOL).

BACKGROUND: United States (US) Hispanic/Latinos experience a disproportionate burden of obesity, which may in part be related to demographic or sociocultural factors, including acculturation to an US diet or inactive lifestyle. Therefore, we sought to describe the association between adulthood weight histories and demographic and sociocultural factors in a large diverse community-based cohort of US Hispanic/Latinos. METHODS: We estimated the effect of several factors on weight gain across adulthood, using multivariable linear mixed models to leverage 38,759 self-reported current body weights and weight histories recalled for 21, 45 and 65 years of age, from 15,203 adults at least 21 years of age at the baseline visit of the Hispanic Community Health Study/Study of Latinos (2008-2011). RESULTS: The average rate of weight gain was nearly 10 kg per decade in early adulthood, but slowed to < 5 kg a decade among individuals 60+ years of age. Birth cohort, gender, nativity or age at immigration, Hispanic/Latino background, and study site each significantly modified the form of the predicted adulthood weight trajectory. Among immigrants, weight gain during the 5 years post-migration was on average 0.88 kg (95% CI: 0.04, 1.72) greater than the weight gain during the 5 years prior. The rate of weight gain appeared to slow after 15 years post-migration. CONCLUSIONS: Using self-reported and weight history data in a diverse sample of US Hispanic/Latinos, we revealed that both demographic and sociocultural factors were associated with the patterning of adulthood weight gain in this sample. Given the steep rate of weight gain in this population and the fact that many Hispanic/Latinos living in the US immigrated as adults, efforts to promote weight maintenance across the life course, including after immigration, should be a top priority for promoting Hispanic/Latino health and addressing US health disparities more broadly.

Prevalence, Awareness, and Treatment of Hypertension in Hispanics/Latinos With CKD in the Hispanic Community Health Study/Study of Latinos.

RATIONALE & OBJECTIVE: Lower rates of hypertension awareness, treatment, and control have been observed in Hispanics/Latinos compared with non-Hispanic whites. These factors have not been studied in Hispanics/Latinos with chronic kidney disease (CKD). We sought to describe the prevalence, awareness, treatment, and control of hypertension in Hispanic/Latino adults with CKD. STUDY DESIGN: Cross-sectional cohort. SETTING & PARTICIPANTS: US.Hispanics/Latinos aged 18 to 74 years enrolled in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) with CKD. Comparisons were made with the National Health and Nutrition Examination Survey (NHANES) 2007 to 2010. EXPOSURE: CKD was defined as estimated glomerular filtration rate < 60 mL/min/1.73 m2 or urinry albumin-creatinine ratio ≥ 30 mg/g creatinine. OUTCOMES: Hypertension was defined as systolic blood pressure (BP) ≥ 140 or diastolic BP ≥ 90 mm Hg or use of antihypertensives. For hypertension control, 2 thresholds were examined: <140/90 and <130/80 mm Hg. RESULTS: The prevalence of hypertension was 51.5%; among those with hypertension, hypertension awareness and treatment were present in 78.1% and 70.4%, respectively. A low prevalence of BP control was observed (32.6% with BP < 140/90 mm Hg; 17.9% with BP < 130/80 mm Hg). Health insurance coverage was associated with higher odds of BP < 140/90 mm Hg (OR, 1.98; 95% CI, 1.15-3.43). Compared with non-Hispanic whites with CKD in NHANES, HCHS/SOL participants with CKD had a lower prevalence of hypertension but a lower rate of BP control (32.6% vs 48.6% for BP < 140/90 mm Hg). LIMITATIONS: Use of a single measurement of creatinine, cystatin C, and urinary albumin excretion to define CKD. Single-visit measurement of BP. CONCLUSIONS: Hispanics/Latinos with CKD residing in the United States have very low rates of BP control. The association of health insurance coverage with hypertension control suggests that improved access to health care may improve outcomes for this growing population.

Genetic, physiological, and lifestyle predictors of mortality in the general population.

OBJECTIVES: We investigated the quality of 162 variables, focusing on the contribution of genetic markers, used solely or in combination with other characteristics, when predicting mortality. METHODS: In 5974 participants from the Rotterdam Study, followed for a median of 15.1 years, 7 groups of factors including age and gender, genetics, socioeconomics, lifestyle, physiological characteristics, prevalent diseases, and indicators of general health were related to all-cause mortality. Genetic variables were identified from 8 genome-wide association scans (n = 19,033) and literature review. RESULTS: We observed 3174 deaths during follow-up. The fully adjusted model (C-statistic for 15-year follow-up [C15y] = 0.80; 95% confidence interval [CI] = 0.79, 0.81) predicted mortality well [corrected]. Most of the additional information apart from age and sex stemmed from physiological markers, prevalent diseases, and general health. Socioeconomic factors and lifestyle contributed meaningfully to mortality risk prediction with longer prediction horizon. Although specific genetic factors were independently associated with mortality, jointly they contributed little to mortality prediction (C(15y) = 0.56; 95% CI = 0.55, 0.57). CONCLUSIONS: Mortality can be predicted reasonably well over a long period. Genetic factors independently predict mortality, but only modestly more than other risk indicators.

Social- and behavioral-specific genetic effects on blood pressure traits: the Strong Heart Family Study.

BACKGROUND: Population studies have demonstrated an important role of social, behavioral, and environmental factors in blood pressure (BP) levels. Accounting for the genetic interaction of these factors may help to identify common BP susceptibility alleles. METHODS AND RESULTS: We studied the interaction of additive genetic effects and behavioral (physical activity, smoking, alcohol use) and socioeconomic (education) factors on BP in approximately 3600 American Indian participants of the Strong Heart Family Study, using variance component models. The mean and SD of resting systolic and diastolic BPs were 123 + or - 17 and 76 + or - 11 mm Hg, respectively. We detected evidence for distinct genetic effects on diastolic BP among ever smokers compared with never smokers (P = 0.01). For alcohol intake, we observed significant genotype-by-environment interactions on diastolic (rhog = 0.10, P = 0.0003) and on systolic BPs (rhog = 0.59, P = 0.0008) among current drinkers compared with former or never drinkers. We also detected genotype-by-physical activity interactions on diastolic BP (rhog = 0.35, P = 0.0004). Finally, there was evidence for distinct genetic effects on diastolic BP among individuals with less than high school education compared with those with 12 or more years of education (rhog = 0.41, P = 0.02). CONCLUSIONS: Our findings suggest that behavioral and socioeconomic factors can modify the genetic effects on BP phenotypes. Accounting for context dependent factors may help us to better understand the complexities of the gene effects on BP and other complex phenotypes with high levels of genetic heterogeneity.