Jessica George ’24
When the brain is resistant to insulin, the body tends to gain weight and distribute fat unfavorably. Resistance to insulin is one of the main characteristics of disorders such as type 2 diabetes and obesity. Today, it is unknown whether it is possible to completely reverse insulin resistance in the brain. Researchers at the Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich sought to examine the results of exercise as an intervention to insulin sensitivity.
The cohort for this clinical trial involved 21 participants (14 women and 7 men) who were all classified as overweight and obese (with BMIs ranging from 27.5–45.5 kg/m2). During an 8-week period, all participants underwent supervised aerobic training intervention. Functional MRI analysis combined with intranasal administration of insulin was utilized to analyze the effect of the aerobic training intervention. Immediately after the intervention, participants showed improvement in mitochondrial respiratory capacity in skeletal muscle fibers as well as a reduction in adipose tissue and fasting plasma glucose levels. The effect of exercise on brain insulin responsiveness was assessed through analysis of cerebral blood flow (CBF). CBF increased in the midbrain and cerebellum after intervention even without administration of insulin. After administration of the nasal insulin, a significant increase in CBF was noted in certain parts of the striatum. Improved brain insulin action in the hippocampus to levels comparable to an individual of a healthy weight was also observed after the intervention by assessing functional connectivity of brain regions. Researchers also explored the correlation between brain insulin responsiveness, cognitive function, and hunger levels. Overall, participants showed improvement in their cognitive functioning. Furthermore, researchers found that improved insulin response in the right putamen was associated with a reduced perception of hunger in participants.
This study demonstrated that 8-weeks of aerobic training intervention was successfully able to restore brain insulin responsiveness in overweight individuals living a sedentary life. Not only do the results suggest that insulin resistance isn’t fixed and can be altered in the brain, it also presents a viable option to increasing brain insulin activity. It is remarkable that just two months of this intervention was able to cause such a drastic change in the brains of individuals. Additionally, exercise is a natural and cost effective option to improving health, unlike certain medications.
 S. Kullmann, et al., Exercise restores brain insulin sensitivity in sedentary adults who are overweight and obese. JCI Insight 7, (2022). doi: 10.1172/jci.insight.161498.
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