Background: The Southern dietary pattern, derived within the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort, is characterized by high consumption of added fats, fried food, organ meats, processed meats, and sugar-sweetened beverages, and is associated with increased risk of several chronic diseases. The aim of the present study was to identify characteristics of individuals with high adherence to this dietary pattern. Design: We analyzed data from REGARDS, a national cohort of 30,239 black and white adults ≥ 45 years of age living in the US. Dietary data were collected using the Block 98 Food Frequency Questionnaire (FFQ). Multivariable linear regression was used to calculate standardized beta coefficients across all covariates for the entire sample and stratified by race and region. Results: We included 16,781 participants with complete dietary data. Among these, 34.6% were black, 45.6% male, 55.2% resided in stroke belt region, and the average age was 65 years. Black race was the factor with the largest magnitude of association to the Southern dietary pattern (Δ = 0.76 SD, p < 0.0001). Large differences in Southern dietary pattern adherence were observed between black participants and white participants in the stroke belt and non-belt (stroke belt Δ = 0.75 SD, non-belt Δ = 0.77 SD). Conclusion: There was a high consumption of the Southern dietary pattern in the US black population, regardless of other factors, underlying our previous findings showing the substantial contribution of this dietary pattern to racial disparities in incident hypertension and stroke.

OBJECTIVE The primary purpose of the current study was to test the hypothesis that the proinsulin–to–C-peptide (PI-to-CP) ratio, as an index of proinsulin secretion, would be higher and associated with indices of β-cell function in African American adults relative to European American adults without type 2 diabetes. RESEARCH DESIGN AND METHODS Participants were 114 African American and European American adult men and women. A 2-h oral glucose tolerance test was conducted to measure glucose, insulin, C-peptide, and proinsulin and derive indices of β-cell response to glucose. The Matsuda index was calculated as a measure of insulin sensitivity. The disposition index (DI), the product of insulin sensitivity and β-cell response, was calculated for each phase of β-cell responsivity. Pearson correlations were used to investigate the relationship of the PI-to-CP ratio with each phase of [beta symbol]-cell response (basal, Φb; dynamic, Φd; static, Φs; total, Φtot), disposition indices (DId, DIs, DItot), and insulin sensitivity. Multiple linear regression analysis was used to evaluate independent contributions of race, BMI, and glucose tolerance status on PI-to-CP levels before and after adjustment for insulin sensitivity. RESULTS African American participants had higher fasting and 2-h PI-to-CP ratios. The fasting PI-to-CP ratio was positively associated with Φb, and the fasting PI-to-CP ratio and 2-h PI-to-CP ratio were inversely associated with DId and insulin sensitivity only in African American participants. CONCLUSIONS The PI-to-CP ratio could be useful in identifying African American individuals at highest risk for β-cell dysfunction and ultimately type 2 diabetes.

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<p>  </p> <p><strong>Objective</strong>: The primary purpose of the present study was to test the hypothesis that the proinsulin-to-C-peptide ratio (PI:CP), as an index of proinsulin secretion, would be higher and associated with indices of beta-cell function in African American adults relative to European American adults without type 2 diabetes. </p> <p><strong>Research Design and Methods</strong>: Participants were 114 African American and European American adult men and women. A 2-h OGTT was conducted to measure glucose, insulin, C-peptide, and proinsulin, and derive indices of beta-cell response to glucose. The Matsuda index was calculated as a measure of insulin sensitivity. The disposition index (DI, the product of insulin sensitivity and beta-cell response) was calculated for each phase of beta-cell responsivity. Pearson correlations were used to investigate the relationship of PI:CP with each phase of beta-cell response (Φb, Φd, Φs, Φtot), disposition indices (DId, DIs, DItot), and insulin sensitivity. Multiple linear regression analysis was used to evaluate independent contributions of race, BMI, and glucose tolerance status on PI:CP levels, before and after adjustment for insulin sensitivity. </p> <p><strong>Results: </strong>African American participants had higher fasting and 2-h PI:CP. Fasting PI:CP was positively associated with Φb, and fasting PI:CP and 2-h PI:CP were inversely associated with DId and insulin sensitivity only in African American participants. </p> <p><strong>Conclusions: </strong>PI:CP could be useful in identifying African American individuals at highest risk for beta-cell dysfunction and ultimately type 2 diabetes. </p>

Racial disparities in health outcomes continue to be a significant public health concern and African Americans (AA) are disproportionately burdened by several risk factors for cardiovascular disease. Endothelial dysfunction has been shown to be a predictor of CVD and metabolic factors, including insulin resistance, are associated with endothelial dysfunction. Compared to EA, AA have impaired endothelial function and are more insulin resistant (less insulin sensitive). However, it remains unclear how insulin resistance may contribute to endothelial dysfunction in AA and EA. The purpose of the present study was to evaluate the relationship between insulin sensitivity and endothelial function in AA and EA. It was hypothesized that insulin sensitivity would be associated with endothelial function in both AA and EA. Skeletal muscle insulin sensitivity was measured by hyperinsulinemic-euglycemic glucose clamp technique in 112 lean, overweight, and obese AA and EA adults without diabetes. Insulin was infused at 120 mU/m 2 /min for 3 hours and an infusion of 20% dextrose was adjusted to maintain blood glucose at the fasting level. Insulin sensitivity (10 -4 .dL.kg -1 .min -1 /(μU/mL)) was defined as M/(G x ΔI), where M is steady state glucose infusion rate, G is steady state serum glucose concentration, and ΔI is the difference between basal and steady state serum insulin concentrations. M was adjusted for total lean body mass which was measured by dual-energy X-ray absorptiometry (DXA). Endothelial function was assessed by percent change in flow-mediated brachial artery dilatation (FMD). Changes in brachial artery diameter during reactive hyperemia were measured using ultrasound. Increased blood flow was induced via blood pressure cuff around the forearm, with a 5-minute inflation at 50 mmHg above the subject’s systolic blood pressure. Brachial arterial flow was determined using a pulsed-Doppler signal at baseline and 10-15 seconds after cuff release. Arterial diameter was measured at end-diastolic phase from super-VHS recordings. For reactive hyperemia response, measurements with the 5 largest diameters were averaged and the percent increase from baseline was determined as FMD. A total of 55 AA and 57 EA were included in the analysis. Mean insulin sensitivity was 4.89 in AA and 7.97 in EA (p < .0001) and mean FMD was 10.69 in AA and 10.14 in EA (p = .595). Linear regression analysis indicated a significant relationship between insulin sensitivity and endothelial function in AA but not in EA (p= .005 and p= .5, respectively). These results suggest that insulin sensitivity may play a role in determining endothelial function in AA.