Hyperinsulinemia in African-American Children

Abstract

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

Adiponectin Is Lower Among African Americans and Is Independently Related to Insulin Sensitivity in Children and Adolescents

“…Although African-American children and adolescents have lower S i compared with Caucasians (16,36), few studies have addressed the potential contribution of serum adiponectin to this difference. We found that among children and adolescents, adiponectin was lower among African Americans compared with Caucasians.…”

Cardiorespiratory fitness and abdominal adiposity in youth

“…A single axial image of the abdomen (L4-L5) was obtained using CT to measure abdominal subcutaneous and visceral AT. Both DEXA and CT methods were described previously (Arslanian et al, 2002). CRF VO 2max was measured using the Bruce multistage treadmill protocol (Cumming et al, 1978) using standard open-circuit spirometry (Parvo Medics, Salt Lake City, UT, USA).…”

“…Dietary intake and physical activity assessment A 24-h weekday food recall was administered by a trained nutritionist in 55 African-American and 49 white subjects using the method that was reported in detail previously (Arslanian et al, 2002). Physical activity level was assessed in 54 African-American and 42 white subjects by a Modifiable Activity Questionnaire (MAQ) as described in detail previously (Andreacci et al, 2004).…”

Glucose inhibits the insulin-induced activation of the insulin-degrading enzyme in HepG2 cells

“…Decreased hepatic insulin degradation is an early phenotypical marker of disturbances in insulin metabolism and it was observed in first-degree relatives of type 2 diabetes patients [2], in obese insulinresistant persons and children with metabolic syndrome [3][4][5]. Decreased insulin degradation may intensify insulin resistance via chronically elevated circulating fasting and postprandial insulin levels.…”