Insulin‐like growth factor 2 alleviates metabolic inflammation and associated cognitive impairment in diet‐induced obesity mice

AIMS: Obesity is a chronic metabolic inflammatory disease caused by energy excess, characterized by excessive adipose tissue accumulation, and is often accompanied by multiple complications such as type 2 diabetes mellitus, metabolic-associated fatty liver disease (MAFLD), and neurological disorders. Adipose tissue plays a central role in maintaining energy homeostasis. Under conditions of energy excess, pro-inflammatory M1-type adipose tissue macrophages (ATMs) are activated, secrete inflammatory factors, inhibit lipolysis and thermogenesis pathways, and exacerbate metabolic disorders. Insulin-like growth factor 2 (IGF2) possesses both metabolic and immunomodulatory functions and is associated with obesity risk; however, its role in ATM polarization remains unclear. This study aims to clarify the regulatory role and mechanism of IGF2 in obesity-related metabolic inflammation and cognitive function. MATERIALS AND METHODS: A high-fat diet (HFD)-induced obese mouse model was established, and interventions were performed via intraperitoneal injection of recombinant IGF2 (rIGF2). Phenotypic polarization of ATMs and expression of inflammatory factors were analyzed by quantitative polymerase chain reaction (qPCR) and immunofluorescence staining. Western blotting was used to detect the expression levels of key proteins in the adrenergic signaling pathway and molecules related to lipolysis/thermogenesis in adipose tissue. Changes in the expression of hippocampal synaptic proteins and cognitive function were evaluated by Western blotting and cognition-related behavioral tests. RESULTS: The study found that rIGF2 intervention significantly promoted the polarization of ATMs from the pro-inflammatory M1 type to the anti-inflammatory M2 type, reduced the levels of inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), thereby relieving the inhibition of the β-adrenergic signaling pathway, activating the expression of hormone-sensitive lipase (HSL) and uncoupling protein 1 (UCP1), promoting lipolysis and thermogenesis, and effectively improving metabolic abnormalities such as insulin resistance and hepatic steatosis in obese mice. Meanwhile, rIGF2 treatment upregulated the expression of synaptic proteins (e.g., PSD-95, Synapsin-1) in the hippocampus of obese mice and significantly ameliorated HFD-induced cognitive impairment. CONCLUSIONS: This study is the first to systematically clarify the dual mechanism of IGF2 in regulating ATM polarization to improve metabolic inflammation, lipolysis-thermogenesis balance, and central cognitive impairment in obesity. The results suggest that IGF2 is not only a key regulator of energy metabolism but also possesses immunomodulatory and neuroprotective potential, providing a new theoretical basis and potential therapeutic target for the prevention and treatment of obesity and its related complications.