The Physiologic Types of Type 2 Diabetes in Africans Vary by Phenotype and Affect Both Diagnostic Paradigms and Therapy—The Africans in America Study

Introduction and Objective: Type 2 diabetes (T2D) is rapidly increasing in Africa. To optimize screening strategy and initial care, both the phenotypic presentation and physiologic determinants must be delineated. Our goals were to determine in African-born Blacks living in America: (a) glucose tolerance status, and (b) in individuals with newly diagnosed T2D, both the phenotype and balance between beta-cell insufficiency (BCI) and insulin resistance (IR). Methods: Glucose tolerance status was determined by a frequently-sampled OGTT in 633 African-born Blacks living in America (male: 62% (394/633), age 39±11, (mean±SD), range 20-70y), BMI: 27.7±4.6, range 18.8-46.2 kg/m2). IR was defined by the lowest quartile of the population distribution of the Matsuda Index (≤2.8). Insulin secretion was assessed with the Insulin Secretion Index (ISI: AUC-insulin/AUC-glucose). In individuals with T2D, BCI was defined by ISI<0.43 in the absence of IR (Matsuda>2.8). Results: T2D, prediabetes and NGT occurred in 7% (44/633), 32% (203/633) and 61% (386/633), resp. Three different physiologic types of DM were identified: BCI-only 45% (20/44), IR-only 29% (13/44), IR+BCI 25% (11/44). Age and gender did not vary by T2D type (both P≥0.4). In the 3 groups with T2D, BMI was: 26.8±2.9, 32.3±4.6, 32.2±3.9 kg/m2 (P-value for trend <0.001); WC was: 92±7,105±8, 106±9 cm (P-value for trend <0.001). AUC-glucose during the OGTT was highest in IR+BCI (P<0.001). AUC-insulin was lower in both the BCI-only and IR+BCI groups than IR-only (both P<0.001). Conclusion: Three physiologic types of T2D were identified: BC-only, IR-only and BCI+IR only. As BCI-only was the most common type of T2D and occurs often in the nonobese, Africans without obesity should be included in screening paradigms. Further, while the BCI-only group are often nonobese and the BC+IR group obese, both groups need early intervention with insulin. Disclosure: K. Ntabadde: None. E.A. Huefner: None. M. Sayed: None. G.G. Smith: None. K. Balahali: None. C. DuBose: None. A. Sherman: None. A.E. Sumner: None.