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Differences in insulin secretion and sensitivity of Caucasian and African American prepubertal children
Gabriel I Uwaifo1, Tuc T Nguyen, Margaret F Keil
1Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1862, USA.
Insights
African American children have reduced insulin sensitivity and higher insulin levels compared to Caucasian children, even after accounting for body composition differences. This suggests other factors influence metabolic health in youth.
Area of Science:
- Pediatric Endocrinology
- Metabolic Health
- Body Composition Research
Background:
- Differences in insulin sensitivity and secretion exist between racial groups in children.
- Body composition is a key factor influencing metabolic health.
- Understanding these differences is crucial for early identification and intervention.
Purpose of the Study:
- To determine if body composition differences explain disparities in insulin sensitivity and secretion between African American (AA) and Caucasian (C) children.
- To investigate racial differences in insulin dynamics and metabolic parameters in prepubertal children.
Main Methods:
- A hyperglycemic clamp was used to assess insulin sensitivity (SI(clamp)) and secretion in 31 AA and 54 C prepubertal children.
- Dual-energy X-ray absorptiometry (DXA) was employed to measure body composition.
- Analysis included adjustments for body fat and lean mass.
Main Results:
- AA children exhibited greater total body fat mass and higher fasting, first-phase, second-phase, and steady-state insulin levels compared to C children.
- Despite similar glucose disposal rates, AA children had lower insulin sensitivity (SI(clamp)).
- Lower C-peptide/insulin molar ratios in AA children suggest reduced hepatic insulin clearance.
Conclusions:
- Prepubertal AA children demonstrate reduced insulin sensitivity and altered insulin/C-peptide secretion profiles compared to C children.
- These metabolic differences are not fully explained by variations in adiposity.
- Reduced hepatic insulin clearance may contribute to the observed metabolic disparities in AA children.
Objective:
To investigate whether differences in body composition of African American children (AA) and Caucasian children (C) explain differences in insulin sensitivity and secretion.
Study Design:
Prepubertal nondiabetic children (31 AA and 54 C) were studied; 84% were overweight. Participants underwent a 2-hour hyperglycemic clamp, to estimate insulin sensitivity (SI(clamp)) and secretion, and dual energy x-ray absorptiometry, to assess body composition.
Results:
AA had greater total body fat mass (P =.01), fasting, 1st phase, 2nd phase, and steady state insulin levels (P <.05). AA and C had similar glucose disposal rates, but AA had lower SI(clamp) (P <.05). Fasting, 1st phase, and steady state C-peptide were less in C (P <.05), whereas corresponding C-peptide/insulin ratios were higher (all P <.005). Insulin levels and SI(clamp) remained different in AA and C after adjustment for body fat or lean mass differences. Analyses restricted to only overweight AA and C showed similar trends.
Conclusion:
Prepubertal African American children have higher baseline and glucose-stimulated insulin and C-peptide levels, as well as reduced insulin sensitivity that is not entirely explained by differences in adiposity. The lower C-peptide/insulin molar ratio in AA suggests that they probably have lower hepatic insulin clearance than Caucasian children.