Improved Aerobic Capacity and Adipokine Profile Together with Weight Loss Improve Glycemic Control without Changes in Skeletal Muscle GLUT-4 Gene Expression in Middle-Aged Subjects with Impaired Glucose Tolerance

(1) Objective: The aim of this study was to clarify the role of adipokines in the regulation of glucose metabolism in middle-aged obese subjects with impaired glucose tolerance in response to a long-term exercise and dietary intervention. (2) Methods: Skeletal muscle, plasma and serum samples were examined in 22 subjects from an exercise-diet intervention study aiming to prevent type 2 diabetes. The subjects were further divided into two subgroups (non-responders n = 9 and responders n = 13) based on their achievement in losing at least 3 kg. (3) Results: The two-year exercise-diet intervention reduced leptin levels and increased adiponectin levels in responders; the changes in leptin levels were significantly associated with changes in their weights (r = 0.662, p < 0.01). In responders, insulin sensitivity (Bennett and McAuley index) increased and was associated with changes in maximal oxygen uptake (VO(2)peak) (r = 0.831, p < 0.010 and r = 0.890, p < 0.01). In addition, the VO(2)peak and oxidative capacity of skeletal muscle improved in responders, but not in non-responders. However, there were no changes between the two groups in expressions of the glucose transporter protein-4 (GLUT-4) gene or of AMP-activated protein kinase (AMPK)-alpha 1 or AMPK-alpha 2 proteins. (4) Conclusions: The exercise-diet intervention decreased serum leptin and increased serum adiponectin concentrations, improved glucose control without affecting GLUT-4 gene expression in the skeletal muscle in responders.

Automated summary

This study aimed to investigate the effects of long-term exercise and dietary intervention on glucose metabolism in middle-aged obese individuals with impaired glucose tolerance. The intervention resulted in decreased leptin levels, increased adiponectin levels, improved insulin sensitivity and maximal oxygen uptake in responders, but did not affect glucose transporter gene expression.