51-LB: Race Specific Effects of a Carbohydrate-Restricted Diet on Acute and Maximal C Peptide Response to Glucose in Adults with Type 2 Diabetes

Beta-cell response to glucose is compromised in individuals with type 2 diabetes (T2D), possibly due to lipid infiltration of the pancreas from excessive carbohydrate consumption. This study was conducted to determine if a eucaloric carbohydrate restricted diet (~9% energy from carbohydrate, 65% energy from fat), compared to a eucaloric fat restricted diet (~55% energy from carbohydrate, 20%energy from fat), would improve beta-cell response to glucose in participants with T2D. Participants were 43 African American and European American adults with T2D not using insulin. Medications were discontinued 1-2 weeks (depending upon the medication) prior to baseline testing. A hyperglycemic clamp was used to assess the acute (first-phase) and maximal (arginine-stimulated) C-peptide responses to glucose at baseline and after 12 weeks of controlled diet therapy (all food provided). Based on the detection of a race-by-diet interaction (P=0.06), data were analyzed within each race group. At 12 weeks, a significant effect of diet was observed by ANCOVA on acute C-peptide response in African Americans (2-fold greater with the carbohydrate restricted diet, P<0.05), and on maximal C-peptide response in European Americans (50% greater with the carbohydrate restricted diet, P<0.01), after adjusting for change in body weight. Paired t-test revealed an improvement in acute C-peptide response within African Americans on the carbohydrate restricted diet (P<0.01) from baseline to week 12, and an improvement in maximal C-peptide response within European Americans on the carbohydrate restricted diet (P<0.01). No changes in beta-cell function were observed in response to the fat restricted diet. These results suggest that a carbohydrate restricted diet has beneficial effects on beta-cell function that are race-specific and independent of weight loss.