Exercise-Induced Irisin Decreases Inflammation and Improves NAFLD by Competitive Binding with MD2

Area of Science:

• Hepatology
• Immunology
• Exercise Physiology

Background:

• Non-alcoholic fatty liver disease (NAFLD) is a prevalent global health issue.
• The MD2-TLR4 signaling pathway is implicated in exacerbating NAFLD through inflammation.
• The precise mechanisms by which exercise benefits NAFLD remain incompletely understood.

Purpose of the Study:

• To investigate the protective effects of exercise on high-fat diet (HFD)-induced liver injury.
• To elucidate the molecular mechanisms underlying exercise-mediated improvements in NAFLD.
• To explore the role of irisin as a potential mediator of exercise benefits in NAFLD.

Main Methods:

• Establishment of a high-fat diet (HFD)-induced NAFLD mouse model.
• Assessment of hepatic steatosis, fibrosis, and inflammatory markers following exercise training.
• In vitro studies using palmitic acid (PA)-stimulated AML12 cells to evaluate irisin's effects.
• Binding assays to determine irisin's interaction with the MD2-TLR4 complex.

Main Results:

• Exercise training significantly reduced hepatic steatosis and fibrosis in HFD-fed mice.
• Exercise suppressed MD2-TLR4 binding and downstream inflammatory responses.
• Irisin levels (circulating and muscle expression) were elevated in exercised mice.
• In vitro, irisin ameliorated lipid metabolism, fibrosis, and inflammation, and directly inhibited MD2-TLR4 complex formation.

Conclusions:

• Exercise confers protection against NAFLD by reducing hepatic inflammation and fibrosis.
• Exercise-induced irisin plays a crucial role in mediating these protective effects.
• Irisin inhibits inflammation by competitively binding to MD2, thereby disrupting MD2-TLR4 complex formation and improving NAFLD.
• Irisin represents a promising therapeutic target for NAFLD treatment.