Exercise and metformin counteract altered mitochondrial function in the insulin-resistant brain

Area of Science:

• Neuroscience
• Metabolic Research
• Mitochondrial Biology

Background:

• Insulin resistance is linked to cognitive decline and dementia.
• The brain, rich in insulin receptors and mitochondria, may be affected by insulin resistance.
• Mechanisms linking insulin resistance to brain dysfunction are not fully understood.

Purpose of the Study:

• To investigate the impact of insulin resistance on brain mitochondrial function.
• To explore the role of oxidative stress and mitochondrial dynamics in HFD-induced brain insulin resistance.
• To determine if exercise and metformin can ameliorate these effects.

Main Methods:

• Utilized high-fat diet (HFD)-induced insulin resistance mouse models.
• Assessed mitochondrial ATP production, oxidative enzyme activity, ROS emission, and antioxidant capacity in brain tissues.
• Examined mitochondrial protein oxidation and fission.
• Investigated the effects of aerobic exercise, metformin, and an insulin receptor antagonist (S961) in vitro and in vivo.

Main Results:

• HFD-induced insulin resistance in mice decreased brain mitochondrial ATP production and oxidative enzyme activity.
• HFD increased ROS emission, reduced antioxidant enzyme activity, and led to mitochondrial damage and fission in the brain.
• Aerobic exercise and metformin improved insulin sensitivity and ameliorated HFD-induced mitochondrial dysfunction.
• Insulin receptor blockade directly impaired mitochondrial ATP production in neurons and astrocytes.
• Exercise-induced mitochondrial benefits were abolished by insulin receptor antagonism during HFD.

Conclusions:

• Insulin resistance directly impairs brain mitochondrial function, affecting energy metabolism and increasing oxidative stress.
• Exercise and metformin restore brain mitochondrial health in insulin-resistant states by improving insulin action.
• Targeting insulin signaling pathways may offer therapeutic strategies for cognitive decline associated with insulin resistance.