The role of β cell dysfunction in the development of type 2 diabetes (DM) is not understood across populations with different levels of insulin resistance. We examined β-cell function in two cohorts of Africans and compared them to Asian Indians. Adults without known DM were examined in 3 cohorts: (1) Mixed Ancestry Africans (MAA, n=1112) living in South Africa, (2) African-born Black immigrants living in United States (A-US, n=529) and born in West, Central or East Africa and (3) Asian Indians (n=1751) living in Chennai, India. OGTT were performed with fasting and 2h glucose and insulin levels obtained. Insulin resistance was defined as HOMA-IR above cohort-specific upper quartile. Beta-cell failure was defined as hyperglycemia without insulin resistance. Beta-cell secretion (HOMA-β) and insulin resistance between ethnicities by ANOVA were compared. MAA were older than A-US or Asians [ (MAA: mean 46y SD 14) , A-US) (39y, SD 10) , Asians (39y, SD 11) with more % female (MA: 73%, A-US 36%, Asians 64%) . Newly diagnosed DM was similar across cohorts (MAA: 6.4%, A-US 7.0%, and Asians 8.1%) . When pooled, 54% total had β-cell failure as the predominant etiology of DM. Fasting glucose, adjusted for age, sex, and BMI, was highest in AI (MAA: 90 mg/dL, SE 0.8; A-US 92, SE 1.1; Asians 101, SE 0.6) . However, A-US had highest 2h glucose (MAA: 97 mg/dL, SE 2.5; A-US 128, SE 4.0; Asians 107, SE 1.8) . In the normal weight BMI group (BMI:18.5-25.0 kg/m2) adjusted for age and sex, HOMA-β was lowest in Asians [97.7, SE 14.6] and 3 times higher in MAA vs. A-US (MAA 151.6, SE 88.3; A-US 48.5, SE 143.6) , despite similar HOMA-IR [MAA: 1.1, SE 0.1; A-US: 1.1 SE 0.1]. The difference in HOMA-β between overweight and obesity strata was modest in Asians and A-US vs. MAA (MAA: 90.9, A-US: 21.6, Asians: 0.9) . Overall, β-cell function was heterogeneous across African cohorts and lowest in Asians. Differences in average β-cell function between overweight and obese participants suggest insulin secretion may be less available to A-US and Asians compared to the MAA.


L.R.Staimez: None. K.Narayan: n/a. S.Dagogo-jack: Consultant; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Janssen Pharmaceuticals, Inc., Medtronic, Merck & Co., Inc., Sanofi. A.Kengne: None. A.E.Sumner: None. R.Shah: None. M.Deepa: None. T.E.Matsha: None. R.Anjana: None. R.T.Erasmus: Speaker's Bureau; Abbott. V.Mohan: None. L.Mabundo: None. C.Dubose: None.

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