TY - JOUR
T1 - The metabolic syndrome and insulin-like growth factor I regulation in adolescent obesity
AU - Attia, Naja
AU - Tamborlane, William V.
AU - Heptulla, Rubina
AU - Maggs, David
AU - Grozman, Aida
AU - Sherwin, Robert S.
AU - Caprio, Sonia
PY - 1998
Y1 - 1998
N2 - Although low GH levels are commonly seen in obese adults and children, the effects of obesity on the insulin-like growth factor (IGF)/IGF-binding protein (IGFBP) system have not been established. As GH and IGF-I normally increase during adolescence, we investigated the effects of obesity on circulating total and free IGF-I levels and IGFBP-1, -2, and -3 in 19 obese adolescents [14 ± 1 yr old; body mass index (BMI), 34 ± 3], 20 lean adolescents (14 ± 1 yr old; BMI, 23 ± 0.5), and 10 lean adults (22 ± 0.7 yr; BMI, 22 ± 0.7). Fasting plasma insulin levels were significantly greater in obese adolescents than in either lean group, whereas circulating IGFBP-1 levels were suppressed in an inverse relationship to basal insulin (r = - 0.49; P < 0.01). Low IGFBP-1 levels were associated with normal to increased free IGF-I levels in obese adolescents, even though total IGF-I values were lower than those in lean adolescents. Basal GH and IGFBP-3 levels were also lower in obese vs. lean adolescents. Basal IGFBP-1 levels were markedly reduced in obese adolescents (14 ± 3 ng/mL) vs. those in adolescents and adults. No further suppression of IGFBP-1 levels was observed in the obese group during a two-step 8 and 40 mU/m2 insulin clamp. In contrast, IGFBP-1 levels were promptly lowered in lean adults. Basal IGFBP-2 levels were significantly lower in both groups of adolescents vs. lean adults (P < 0.05), and IGFBP-2 levels did not change during euglycemic hyperinsulinemia. These data suggest that the compensatory hyperinsulinemia that characterizes adolescent obesity chronically suppresses levels of IGFBP-1, and low IGFBP-1 concentrations may serve to increase the bioavailability of free IGF-I, which may, in turn, contribute to lower circulating GH, total IGF-I, and IGFBP-3 concentrations.
AB - Although low GH levels are commonly seen in obese adults and children, the effects of obesity on the insulin-like growth factor (IGF)/IGF-binding protein (IGFBP) system have not been established. As GH and IGF-I normally increase during adolescence, we investigated the effects of obesity on circulating total and free IGF-I levels and IGFBP-1, -2, and -3 in 19 obese adolescents [14 ± 1 yr old; body mass index (BMI), 34 ± 3], 20 lean adolescents (14 ± 1 yr old; BMI, 23 ± 0.5), and 10 lean adults (22 ± 0.7 yr; BMI, 22 ± 0.7). Fasting plasma insulin levels were significantly greater in obese adolescents than in either lean group, whereas circulating IGFBP-1 levels were suppressed in an inverse relationship to basal insulin (r = - 0.49; P < 0.01). Low IGFBP-1 levels were associated with normal to increased free IGF-I levels in obese adolescents, even though total IGF-I values were lower than those in lean adolescents. Basal GH and IGFBP-3 levels were also lower in obese vs. lean adolescents. Basal IGFBP-1 levels were markedly reduced in obese adolescents (14 ± 3 ng/mL) vs. those in adolescents and adults. No further suppression of IGFBP-1 levels was observed in the obese group during a two-step 8 and 40 mU/m2 insulin clamp. In contrast, IGFBP-1 levels were promptly lowered in lean adults. Basal IGFBP-2 levels were significantly lower in both groups of adolescents vs. lean adults (P < 0.05), and IGFBP-2 levels did not change during euglycemic hyperinsulinemia. These data suggest that the compensatory hyperinsulinemia that characterizes adolescent obesity chronically suppresses levels of IGFBP-1, and low IGFBP-1 concentrations may serve to increase the bioavailability of free IGF-I, which may, in turn, contribute to lower circulating GH, total IGF-I, and IGFBP-3 concentrations.
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U2 - 10.1210/jc.83.5.1467
DO - 10.1210/jc.83.5.1467
M3 - Article
C2 - 9589640
AN - SCOPUS:0031753008
VL - 83
SP - 1467
EP - 1471
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
SN - 0021-972X
IS - 5
ER -