Exercise improves brain insulin action in sedentary overweight and obese adults

Introduction:

Exercise has beneficial effects on metabolism and brain function and is therefore recommended to prevent type 2 diabetes and support its treatment. However, little is known whether exercise can improve insulin sensitivity of the brain in overweight and obese individuals prone to brain insulin resistance.

Methods:

22 participants (15 women; BMI 31.15 ± 3.87 kg/m2; age 30.41 ± 8.6 years) underwent two functional magnetic resonance imaging (fMRI) sessions before and after an 8-week supervised exercise intervention, including cycling and walking training. Furthermore, participants received a 75 g oral glucose tolerance test before and after the intervention to assess peripheral insulin sensitivity. During the fMRI session, intranasal insulin was used to probe brain insulin action.

Results:

We observed exercise-induced changes in the dopaminergic system of the brain. In response to intranasal insulin, participants showed an increase in striatal blood flow prior to the intervention and a decrease after the intervention (p < 0.05). This insulin-driven attenuation is consistently observed in healthy lean individuals. Interestingly, the exercise-induced change in peripheral insulin sensitivity significantly correlated with the 'normalized' brain insulin action (r =-0.472, p = 0.02). Hence, participants who improved their peripheral insulin sensitivity showed the most prominent change in brain insulin action and better dopamine-dependent executive functioning based on the trail-making test after the exercise program (r =-0.521, p = 0.006).

Conclusion:

Exercise significantly improved brain insulin action, which was related to improvements in whole-body metabolism. As not all participants showed this beneficial effect, methods to boost brain insulin sensitivity are needed to improve glucose metabolism and brain functions.