Science

Stephanie Kullmann, Thomas Goj, Ralf Veit, Louise Fritsche, Lore Wagner, Patrick Schneeweiss, Miriam Hoene, Christoph Hoffmann, Jürgen Machann, Andreas Niess, Hubert Preiss, Andreas L. Birkenfeld, Andreas Peter, Hans-Ulrich Häring, Andreas Fritsche, Anja Moller, Cora Weigert, and Martin Heni

BACKGROUND. Insulin resistance of the brain can unfavorably affect long-term weight maintenance and body fat distribution. Little is known if and how brain insulin sensitivity can be restored in humans. We aimed to evaluate the effects of an exercise intervention on insulin sensitivity of the brain and how this relates to exercise-induced changes in whole-body metabolism and behavior.

METHODS. In this clinical trial, sedentary participants who were overweight and obese underwent an 8-week supervised aerobic training intervention. Brain insulin sensitivity was assessed in 21 participants (14 women, 7 men; age range 21–59 years; BMI range 27.5–45.5 kg/m2) using functional MRI, combined with intranasal administration of insulin, before and after the intervention.

RESULTS. The exercise program resulted in enhanced brain insulin action to the level of a person of healthy weight, demonstrated by increased insulin-induced striatal activity and strengthened hippocampal functional connectivity. Improved brain insulin action correlated with increased mitochondrial respiration in skeletal muscle, reductions in visceral fat and hunger, as well as improved cognition. Mediation analyses suggest that improved brain insulin responsiveness helps mediate the peripheral exercise effects leading to healthier body fat distribution and reduced perception of hunger.

CONCLUSION. Our study demonstrates that an 8-week exercise intervention in sedentary individuals can restore insulin action in the brain. Hence, the ameliorating benefits of exercise toward brain insulin resistance may provide an objective therapeutic target in humans in the challenge to reduce diabetes risk factors.