Abstract P430: Waist Circumference is a Key Predictor of Beta-Cell Function in Lean Rwandans With New-Onset Type 2 Diabetes Mellitus

Introduction: Type 2 diabetes mellitus (T2D) is common in Rwanda and other middle and low-income countries. Unlike high-income countries, T2D is prevalent in lean people; the reasons for this are unclear but may relate to abdominal obesity. Therefore, we examined the impact of waist circumference (WC) on insulin-resistance (IR) and insulin secretion rate (ISR) in lean, (BMI <25kg/m 2 ) Rwandan adults with and without new-onset (<1yr) T2D. Hypothesis: We hypothesized that Rwandans with T2D and normal WC would have a lower ISR than both people with T2D and elevated WC and healthy people but that ISR would not be different between Rwandans with T2D and elevated WC and healthy people. Methods: BMI, WC, and a 3-hour frequently-sampled oral-glucose tolerance-test (fsOGTT) were performed in 23 Rwandans; 15 with T2D and 8 healthy people. Normal WC was defined as <85cm for women and <90cm for men (>75 th %ile of group). ISR was determined by mathematical-modeling. Groups were compared by Student’s t-test and ANOVA. Results: Groups were well matched; glucose area under the curve (AUC) was greater and insulinogenic-index was lower in T2D overall than healthy people (Table 1). ISR area under the curve (ISR-AUC) was not different between T2D and healthy people. In contrast, Rwandans with T2D and normal WC had an ISR-AUC ~2.5 fold lower than Rwandans with T2D and elevated WC (P<0.001). Matsuda index and HOMA were greater in Rwandans with T2D and elevated WC than healthy people (P=0.09, P=0.07 respectively). Conclusions: In lean Rwandan people with new-onset T2D but normal WC, alterations in insulin secretion rather than insulin-resistance are key drivers of hyperglycemia. In T2D with elevated WC, IR rather than insulin secretion may be a major factor. This suggests that the pathogenesis of T2D differs based on WC in Rwanda with implications for prevention and therapy. Table 1. Subject Characteristics * P<0.05 vs corresponding value in other groupA, P<0.05 and B, P=0.07 vs corresponding value in other group when comparing on basis of WC.