Lucchinetti, Claudia F.

Background: Tumor necrosis factor alpha (TNF-alpha) inhibitors, such as infliximab, are commonly used to treat rheumatoid arthritis (RA) and other immune-mediated disorders. Objective: To determine whether infliximab-associated central nervous system (CNS) demyelination can be differentiated from multiple sclerosis (MS). Methods: We present a case of pathologically proven CNS demyelination in a patient treated with infliximab and describe clinical–radiographic–neuropathological findings. Putative mechanisms of TNF-alpha inhibitor-associated CNS demyelination are described. Results and conclusion: Infliximab treatment is associated with CNS inflammatory demyelinating activity, which is histopathologically indistinguishable from MS.

Insulin resistance associates with increased risk for cognitive decline and dementia; however, the underpinning mechanisms for this increased risk remain to be fully defined. As insulin resistance impairs mitochondrial oxidative metabolism and increases ROS in skeletal muscle, we considered whether similar events occur in the brain, which — like muscle — is rich in insulin receptors and mitochondria. We show that high-fat diet–induced (HFD-induced) brain insulin resistance in mice decreased mitochondrial ATP production rate and oxidative enzyme activities in brain regions rich in insulin receptors. HFD increased ROS emission and reduced antioxidant enzyme activities, with the concurrent accumulation of oxidatively damaged mitochondrial proteins and increased mitochondrial fission. Improvement of insulin sensitivity by both aerobic exercise and metformin ameliorated HFD-induced abnormalities. Moreover, insulin-induced enhancement of ATP production in primary cortical neurons and astrocytes was counteracted by the insulin receptor antagonist S961, demonstrating a direct effect of insulin resistance on brain mitochondria. Further, intranasal S961 administration prevented exercise-induced improvements in ATP production and ROS emission during HFD, supporting that exercise enhances brain mitochondrial function by improving insulin action. These results support that insulin sensitizing by exercise and metformin restores brain mitochondrial function in insulin-resistant states.