Type 2 diabetes in youth: are there racial differences in β-cell responsiveness relative to insulin sensitivity?

Bacha F, Gungor N, Lee S, Arslanian SA. Type 2 diabetes in youth: are there racial differences in beta-cell responsiveness relative to insulin sensitivity? Objective: Non-diabetic African American (AA) youth have an upregulated insulin secretion relative to insulin sensitivity (IS) compared with their American White (AW) peers. We investigated if similar racial differences exist in youth with T2DM. Research Design and Methods: Fourteen AAs and 14 AWs T2DM adolescents underwent evaluation of IS and clearance (hyperinsulinemiceuglycemic clamp), first- and second-phase insulin and C-peptide secretion (hyperglycemic clamp); body composition (DEXA); and abdominal adiposity (CT). Results: AA and AW T2DM had similar HbA1c, diabetes duration, BMI, and % body fat, with lower visceral fat in AAs (p = 0.013). While insulin-stimulated glucose disposal was similar in AA and AW (7.5 +/- 1.0 vs. 7.3 +/- 0.9 mg/kg FFM/min), IS tended to be lower (2.5 +/- 0.4 vs. 3.8 +/- 0.6 mg/kg FFM/min per mu U/mL, p = 0.081). First-phase insulin (175.7 +/- 52.9 vs. 66.6 +/- 10.8 mu U/mL, p = 0.01) and second-phase insulin (236.2 +/- 40.7 vs. 105.1 +/- 17.9 mu U/mL, p = 0.008), and first-phase C-peptide (8.2 +/- 1.2 vs. 5.0 +/- 0.3 ng/mL, p = 0.02) and second-phase C-peptide (10.8 +/- 0.9 vs. 7.6 +/- 0.6 ng/mL, p = 0.012) were higher in AA. beta-Cell function relative to IS was higher in AA vs. AW (259.5 +/- 35.3 vs. 168.8 +/- 25.1 mg/kg FFM/min, p = 0.043). Conclusions: Racial differences in insulin secretion can be demonstrated with the clamp technique in obese adolescents with T2DM. Similar to non-diabetic youth, AA adolescents with T2DM compared with their AW counterparts have an upregulated beta-cell function relative to IS, the reasons for which remain to be investigated.