Relation of obesity to insulin secretion and clearance in adolescents: the Bogalusa Heart Study.
OBJECTIVE
Earlier we found elevated insulin levels in obese children and adolescents. The present study examines whether alterations in insulin secretion and/or clearance contribute to hyperinsulinemia in obese adolescents.


METHODS
Fasting circulating insulin and C-peptide concentrations were examined in 1157 adolescents, aged 11-18 y, from a biracial (black/white) community. In this epidemiologic study, plasma C-peptide was used as a noninvasive measure of insulin secretion by beta cells, C-peptide to insulin ratio as an indicator of hepatic insulin extraction, and insulin to glucose ratio as a measure of insulin sensitivity. Body mass index (BMI) was used as an index of obesity, since it is strongly associated with insulin levels and the C-peptide to insulin ratio more so than with measures of skinfolds and percent body fatness.


RESULTS
Obese individuals (BMI > 90th P) had higher levels of plasma insulin (23.7 mu/ml vs 11.7 mu/ml), C-peptide (2.7 ng/ml vs 1.7 ng/ml), and insulin to glucose ratio (0.29 vs 0.15), and lower C-peptide to insulin ratio (0.13 vs 0.16) than non-obese adolescents (all P < 0.001). Elevated C-peptide and decreased C-peptide to insulin ratio were noted in subjects with both obesity and hyperinsulinemia (insulin > 90th P) versus those without these conditions (P < 0.001). Individuals with obesity and low insulin clearance (C-peptide/insulin < 10th P) had 18-fold higher prevalence of hyperinsulinemia versus those without these conditions. Although black adolescents, despite their lower percent body fat, had higher insulin and lower C-peptide and C-peptide to insulin ratio than their white counterparts, BMI related positively to insulin and C-peptide, and inversely with C-peptide to insulin ratio in both races.


CONCLUSIONS
These data suggest that both increased insulin secretion and decreased insulin clearance contribute to hyperinsulinema in obese adolescents.
Tulane Center for Cardiovascular Health, Tulane School of Public Health and Tropical Medicine, New Orleans, Louisiana, USA.
X
X
Jiang
S R
SR
Srinivasan
G S
GS
Berenson
D000293:Adolescent; D044383:Black People; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D002648:Child; D005260:Female; D006801:Humans; D006946:Hyperinsulinism / Q000209:etiology; D007328:Insulin / Q000097:blood* / Q000378:metabolism*; D000078790:Insulin Secretion; D008145:Louisiana; D008297:Male; D008657:Metabolic Clearance Rate; D009765:Obesity / Q000503:physiopathology*; D044465:White People; D001741:Black or African American
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin