ARS | Publication request: A 12 week aerobic exercise program improves fitness, hepatic insulin sensitivity and glucose metabolism in obese Hispanic adolescents

Submitted to: Pediatric Academic Society
Publication Type: Abstract Only
Publication Acceptance Date: February 16, 2009
Publication Date: May 3, 2009
Citation: van der Heijden, G., Toffolo, G., Sunehag, A.L. 2009. A 12 week aerobic exercise program improves fitness, hepatic insulin sensitivity and glucose metabolism in obese Hispanic adolescents [abstract]. Pediatric Academic Society.Abstract no. 3854.52.

Technical Abstract: The rise in obesity related morbidity in children and adolescents requires urgent prevention and treatment strategies. Strictly controlled exercise programs might be useful tools to improve insulin sensitivity and glucose kinetics. Our objective was to test the hypothesis that a 12-wk aerobic exercise program without intent of weight loss increases peripheral and hepatic insulin sensitivity and reduces glucose production in sedentary, obese Hispanic adolescents. Fifteen obese adolescents, 7m/8f;16+/-1 y; 33+/-1 kg/m2; 38+/-1% body fat (mean+/-se) completed 91+/-3% of a 12-wk aerobic exercise program (30 min x 4/wk) at 86+/-2% of their heart rate at VO2 peak. At baseline and at completion of the exercise program, glucose production (GPR), gluconeogenesis (GNG), and glycogenolysis (GLYC) were measured using stable isotope-GCMS techniques; overall insulin sensitivity was measured by fasting insulin and QUICKI (1/[log fasting insulin (microU/mL) + log fasting glucose (mg/dL)]; peripheral insulin sensitivity (Si) was measured by the stable labeled IV glucose tolerance test (SLIVGTT) applying the minimal model; and an index of hepatic insulin sensitivity (HISI) was calculated as 1000/[GPR (micromol/kg lean body mass (LBM)/min) x fasting insulin (microU/mL)]. Both study occasions were preceded by 7d of identical diets (energy and macronutrient content). Cardiovascular fitness (measured by VO2 peak) increased by approx. 15%. Body weight was unchanged (as intended). In response to the exercise program, fasting plasma insulin decreased from 20.2+/-2.5 to 17.5+/-2.2 microU/mL; p<0.01, while plasma glucose remained the same, 91+/-2 vs. 90+/-2 mg/dL; QUICKI increased from 0.3121+/-0.0054 to 0.3190+/-0.0059; p<0.01. Similarly HISI increased from 4.2+/-0.5 to 5.1+/-0.6; p<0.01, while the change in Si (1.6+/-0.3 vs.1.9+/-0.4 x10-4(min-1mU L-1) did not reach significance. GPR decreased from 14.6+/-0.3 to 14.1+/-0.3 µmol/kgLBM/min; p<0.01 due to a decrease in GLYC from 6.1+/-0.4 to 5.7+/-0.4 micromol/kgLBM/min; p<0.05, while GNG was unchanged. A 12-wk aerobic exercise program (without weight loss) improves insulin sensitivity as indicated by reduced fasting insulin at unchanged fasting glucose concentration, increased QUICKI and increased HISI. However, additional subjects must be studied to prove or refute an effect on peripheral insulin sensitivity. Further, although small, the reduction in GPR might be important in preventing hyperglycemia.