Isthmin-1 as a novel adipokine: a potential target for exercise-induced metabolic modulation in obesity

Obesity is a major global health challenge, now recognized as a complex metabolic and inflammatory disorder characterized by excess adiposity and chronic low-grade inflammation. Adipose tissue functions as an endocrine organ, secreting adipokines that regulate metabolism and immune responses. Among these, Isthmin-1 (ISM1) has recently emerged as a novel adipokine with important metabolic and anti-inflammatory roles. ISM1 is widely expressed in adult tissues and is associated with central adiposity and metabolic dysfunction. It enhances glucose uptake via an insulin-independent PI3K/Akt pathway through integrin αVβ5 activation, promoting GLUT4 translocation. ISM1 also regulates lipid metabolism by inhibiting lipogenesis and stimulating fatty acid oxidation. Additionally, it exerts anti-inflammatory effects by suppressing NF-κB signaling and promoting macrophage polarization toward an anti-inflammatory phenotype. Exercise is known to improve adipokine profiles, insulin sensitivity, and inflammation, but its effects on ISM1 remain unexplored. This represents a critical gap in the literature. Understanding how different exercise modalities influence ISM1 could reveal new mechanisms underlying exercise benefits and support its potential as a biomarker or therapeutic target in obesity and metabolic disorders.