Normal insulin response to short-term intense exercise is abolished in Type 2 diabetic patients treated with gliclazide

Abstract

Background

Physical activity is an essential component of diabetes management; however, exercise is associated with the risk for metabolic decompensation. The aim of the study was to analyze insulin response to the short-term intense exercise in middle-aged Type 2 diabetic patients treated with gliclazide.

Materials and Methods

Fourteen Type 2 diabetic patients (47.9±1.6 years, mean±S.E.M.), treated with gliclazide, and 14 healthy controls (45.1±1.0 years) were submitted to standard graduated submaximal (90% HR_max) exercise treadmill testing at 2 h after standardized breakfast. Serum glucose, insulin, proinsulin, C peptide, growth hormone, insulin-like growth factor-1, and cortisol concentrations; and plasma lactate, glucagon, epinephrine, and norepinephrine concentrations were measured during the periexercise period up to the 60th min of the recovery period.

Results

Significant hemodynamic (heart rate, systolic, and diastolic blood pressure), metabolic (lactate concentration), and hormonal (epinephrine and norepinephrine levels) responses to the exercise were similar in patients and healthy subjects. Glucose, insulin, and proinsulin levels were higher in the diabetic group at the preexercise and at all the next analyzed time points. The insulin concentration increased during the postprandial period in both groups and decreased subsequently during the exercise only in the control group, without concurrent C peptide decline. The C peptide-to-insulin ratio increased during the exercise and decreased immediately postexercise only in the control group.

Conclusions

The initial decrease of the insulin serum concentration during short-term intense exercise in normal middle-aged men is primarily related to the increased clearance of the hormone. Normal insulin response to the exercise was abolished in Type 2 diabetic patients treated with gliclazide.

Introduction

Increasing prevalence of diabetes mellitus and its complications emphasize the need for better control of risk factors among diabetic patients (Candrilli et al., 2007, Fox et al., 2007, Stewart et al., 2006). Physical activity is strongly recommended to improve glycemic control, assist with weight maintenance, and reduce risk of long-term complications (American Diabetes Association, 2007, Balducci et al., 2006, Buse et al., 2007). However, an exercise bout is associated with a transient increase of risk for metabolic decompensation or cardiovascular event (Haskell et al., 2007, Nugent et al., 1997, Tabib et al., 1999, Stepka et al., 1993). Therefore, investigation of metabolic and hemodynamic responses to various types of effort in connection with the patient-related conditions is essential to provide guidelines for safe and effective exercise. On the other hand, stress can reveal additional physiological aspects of a disease. In our previous study (Szewieczek, Dulawa, Strzałkowska, Hornik, & Kawecki, 2007), we have analyzed a glycemic response to the short-term intense exercise. This study is focused on the changed insulin response to the exercise in middle-aged Type 2 diabetic patients treated with gliclazide.