Endurance Training Improves GLP-1 Sensitivity and Glucose Tolerance in Overweight Women.

Context and objective: Obesity and inactivity are risk factors for developing impaired glucose tolerance characterized by insulin resistance and reduced beta-cell function. The stimulatory effect of glucagon-like peptide 1 (GLP-1) on insulin secretion is also impaired in obese, inactive individuals. The aim of this study was to investigate whether endurance training influences beta-cell sensitivity to GLP-1. Participants and intervention: Twenty-four female participants, age 46 +/- 2 years, body mass index 32.4 +/- 0.9 kg/m(2), and maximal oxygen consumption 24.7 +/- 0.8 mL/kg/min participated in a 10-week exercise training study. Methods: Beta-cell sensitivity to GLP-1 was assessed in a subset of participants (n = 6) during a 120-minute hyperglycemic glucose clamp (8.5 mM) including a 1-hour GLP-1 (7-36 amide) infusion (0.4 pmol/kg/min). Changes in glucose tolerance, body composition, and cardiorespiratory fitness were assessed by oral glucose tolerance tests (OGTTs), dual-energy X-ray absorptiometry scans, magnetic resonance scans, and maximal oxygen consumption (VO(2)max) tests, respectively. Results: The c-peptide response to infusion of GLP-1 increased 28 +/- 3% (P < 0.05) toward the end of the hyperglycemic clamp. The insulin response remained unchanged. Training improved glucose tolerance and reduced GLP-1, insulin, and glucagon levels during the OGTTs. Training increased VO(2)max (from 24.7 +/- 0.8 to 27.0 +/- 0.7 mL/kg/min; P < 0.05) and reduced visceral fat volume (from 4176 +/- 265 to 3888 +/- 266 cm(3); P < 0.01). Conclusion: Along with improved glycemic control, endurance training improved beta-cell sensitivity to GLP-1 in overweight women. The study was deemed not to constitute a clinical trial and was not registered as such.