Effects of Aerobic Exercise on Postprandial Glucose in Glucose intolerant Subjects

Abstract

Exercise is recommended for the treatment of all forms of glucose intolerance (i.e. impaired fasting glucose; impaired glucose tolerance; type 2 diabetes), yet little is known about the relationship between the timing of exercise and its effects on subsequent blood glucose (BG) levels throughout the day in glucose intolerance. PURPOSE: The purpose of the ongoing study is to examine the effects of early morning exercise on postprandial metabolism in glucose intolerant (n=4; f=3; m=1) and normglycemic (n=6; f=3; m=3) subjects. METHODS: Subjects were hospitalized in the General Clinical Research Center (GCRC) on two separate occasions for participation in exercise [E] and non-exercise [NE] protocols. The E protocol began at 0800 hours following an overnight fast. During the E protocol subjects walked on the treadmill for 30 minutes at 65% V0 Max. During the NE protocol, the exercise session was replaced by a 30 minute period of rest. Blood glucose levels were monitored for 18 hours following the exercise/rest sessions, using continuous glucose monitoring sensors. Patients remained in the GCRC following exercise/rest sessions; diet and physical activity were similar during each visit. RESULTS: The baseline characteristics of subjects (glucose intolerant vs. normoglycemic) were as follows: age (48±0.8 vs. 39.8± 11.1 years [mean and SD]); BMI(34.2±3.6vs. 36.5±2.6); % body fat (35.1±3.6 vs. 36.5±2.6); V02Max(23.1±10.8 vs. 28.3±3.6 ml/kg). Mean BG levels were calculated for the 3-hour postprandial period following breakfast, lunch and dinner and the entire 18 hours following exercise/rest. As expected, there were between group differences in all mean BG levels at these times (p <0.0005). Within the glucose intolerant group, exercise was associated with significant reductions in BG levels following breakfast and lunch when compared to rest (breakfast: 10.3 ± 4.2 vs. 8.5 ± 5.5 mmol/l [p <0.04]; [rest vs. exercise]; lunch (9.2 ± 3.6 vs. 7.3 ± 3.4 mmol/l [p<0.01]). In addition, there was an overall reduction in mean BG levels for the1 8-period following exercise (9.0 ±3.7 vs. 7.6 ±2.9 mmol/l [p<0.03]) within this group. CONCLUSION: An early morning bout of exercise is associated with reduced BG at least 18 hours following exercise as compared to rest in a small sample of glucose intolerant subjects. The use of glucose sensor technology will help researchers characterize glucose dynamics following different types of exercise. Study is funded by NIH grant R01NR007760-01A2, and supported by the GCRC at the University of Illinois at Chicago (NIH grant M01-RR-13987)