Effects of Supervised Exercise on Gamma-Glutamyl Transferase Levels in Patients with Isolated Impaired Fasting Glucose and Those with Impaired Fasting Glucose Plus Impaired Glucose Tolerance

Aim: To study the effects of a supervised exercise program on serum gamma-glutamyl transferase (GGT), glycemic control and cardiovascular risk factors in pre-diabetic patients with isolated impaired fasting glucose (IFG) and those with IFG plus impaired glucose tolerance (IGT). Methods: Out of 60 pre-diabetic patients (30 with isolated IFG and 30 with IFG + IGT) 24 were randomly assigned to the supervised exercise program (1 h twice a week) and 36 only obtained counselling on the risk of diabetes and its prevention. Patients have been followed over a 12-month period. Results: The main findings were that patients with IFG + IGT had increased GGT levels at baseline (49.2 +/- 27.4 U/L) compared to subjects with isolated IFG (28.1 +/- 21.9 U/L) (p < 0.01), and that GGT levels improved only after the supervised exercise intervention within the IFG + IGT subjects (-17.7 + 19.6 U/L). Similarly, baseline triglyceride levels were also higher in IFG + IGT patients (p < 0.001) and there was a decrease through exercise intervention in these patients only (p < 0.05). Conclusion: GGT is an unspecific marker of oxidative stress and both high plasma glucose and triglycerides levels may produce oxidative stress. Thus, patients with IFG + IGT seem to have higher levels of oxidative stress than those with isolated IFG. Based on the known association between GGT levels and cardiovascular risk factors, IFG + IGT patients may be at higher risk for the development of cardiovascular diseases. The specific effect of regular exercise on GGT in pre-diabetic patients may contribute to the understanding of the preventive effects related to exercise.