African-American (AA) children are hyperinsulinemic and insulin resistant compared with American White (AW) children. This study investigated 1) whether AA/AW differences in insulinemia are associated with differences in insulin clearance; 2) whether dietary patterns, mainly carbohydrate and fat intake, play a role; and 3) whether the quantitative relationship between insulin sensitivity and secretion is similar between AA and AW children. Forty-four prepubertal children (22 AA and 22 AW) with comparable body composition and visceral adiposity were studied. All underwent a 3-h hyperinsulinemic (40 mU ⅐ m ؊2 ⅐ min ؊1)-euglycemic clamp to calculate insulin sensitivity and insulin clearance and a 2-h hyperglycemic clamp (12.5 mmol/l) to assess first-and second-phase insulin responses. Twenty-four-hour food recalls were analyzed for macronutrient intake. Insulin clearance (19.5 ؎ 0.7 vs. 22.9 ؎ 1.1 ml ⅐ min ؊1 ⅐ kg ؊1 fat-free mass [FFM]; P ‫؍‬ 0.011) and insulin sensitivity were lower in AA versus AW children (14.8 ؎ 1.0 vs. 18.9 ؎ 1.4 mol ⅐ min ؊1 ⅐ kg ؊1 FFM; P ‫؍‬ 0.021). Both insulin clearance and insulin sensitivity correlated inversely with dietary fat/carbohydrate ratio, which was higher in AA than in white children. Fasting C-peptide and insulin were higher in AA children with no difference in proinsulin levels. First-and second-phase insulin concentrations and glucose disposition index (insulin sensitivity ؋ first-phase insulin) were higher in AA than in white children (12.8 ؎ 2.1 vs. 7.2 ؎ 0.6 mol ⅐ min ؊1 ⅐ kg ؊1 FFM; P ‫؍‬ 0.019). In conclusion, the hyperinsulinemia observed in AA children is due to both lower insulin clearance and higher insulin secretion compared with their white peers. The quantitative relationship between insulin secretion and sensitivity is upregulated in AA children. This suggests that increased insulin secretion in AA children is not merely a compensatory response to lower insulin sensitivity. Dietary factors may have a role. Additional studies are needed to determine whether metabolic/nutritional factors, possibly mediated through free fatty acids, may play a role in the hyperinsulinism observed in AA children. Diabetes 51:3014 -3019, 2002

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Functional adrenal hyperandrogenism occurs in women with polycystic ovary syndrome (PCOS). Insulin, similar to its ovarian effect, may impact the regulation of adrenal steroidogenesis by modulating the activity of P450c17alpha, the rate-limiting enzyme in androgen biosynthesis. We previously demonstrated that obese adolescents with PCOS are severely insulin resistant and are at heightened risk for impaired glucose tolerance and type 2 diabetes. In the present study we tested the hypothesis that metformin therapy in obese adolescents with PCOS will attenuate the adrenal steroidogenic response to ACTH, with reduction of insulin resistance/insulinemia. Fifteen adolescents with PCOS and impaired glucose tolerance received 3 months of metformin (850 mg, twice daily) therapy. Pre- and posttherapy they had oral glucose tolerance testing, ACTH stimulation test, a 3-h hyperinsulinemic (80 mU/m(2).min)-euglycemic clamp to assess insulin sensitivity and a hyperglycemic clamp to assess insulin secretion. After 3 months of metformin treatment, glucose intolerance improved, with eight subjects having normal glucose tolerance. Total and free T decreased [1.5 +/- 0.2 vs. 1.0 +/- 0.1 nmol/liter (P = 0.022) and 41.3 +/- 8.3 vs. 22.2 +/- 2.1 pmol/liter (P = 0.028), respectively]. Insulin-stimulated glucose disposal increased (21.5 +/- 2.2 vs. 25.0 +/- 2.2 micromol/kg.min; P = 0.041). Fasting insulin and oral glucose tolerance test insulin and glucose area under the curve decreased significantly. ACTH-stimulated increases in androstenedione, 17-hydroxyprogesterone, and 17-hydroxypregnenelone were lower after metformin treatment [2.8 +/- 0.4 vs. 1.7 +/- 0.3 nmol/liter (P = 0.014), 7.0 +/- 0.6 vs. 5.3 +/- 0.5 nmol/liter (P = 0.011), and 30.4 +/- 3.7 vs. 25.7 +/- 4.2 nmol/liter (P = 0.054)]. Fasting insulin correlated with the 17-hydroxypregnenelone response to ACTH stimulation (r = 0.52; P = 0.008). In summary, metformin treatment of obese adolescents with PCOS and impaired glucose tolerance is beneficial in improving glucose tolerance and insulin sensitivity, in lowering insulinemia, and in reducing elevated androgen levels. Moreover, metformin therapy is associated with attenuation of the adrenal steroidogenic response to ACTH. Metformin therapy was well tolerated. In conclusion, double blind, placebo-controlled studies will determine whether insulin-sensitizing therapy corrects not only ovarian hyperandrogenism but also functional adrenal hyperandrogenism in adolescents with PCOS.

These data suggest that in African-American children, family history of type 2 diabetes is a risk factor for insulin resistance. These children manifest important metabolic alterations, including impaired insulin-stimulated total and nonoxidative glucose disposal early in the first decade of life. We propose that this familial tendency, combined with environmental influences, could lead to type 2 diabetes decades later.