Follistatin Mitigates Atherosclerosis Through Activation of Arginine Metabolism and Adipose Browning

Follistatin (FST) binds to and neutralizes members of the transforming growth factor-beta (TGF-β) superfamily, thereby regulating diverse physiological processes, including regulation of skeletal muscle, adipose, and bone homeostasis. FST also promotes adipose browning and enhances energy metabolism, leading to improved plasma lipid profiles and metabolic health in mice. Given the emerging association between brown adipose tissue (BAT) activation and reduced atherosclerosis, we investigated the anti-atherogenic potential of FST. Transcriptomic and metabolomic analyses of the Hybrid Mouse Diversity Panel (HMDP) revealed that Fst expression was negatively correlated with aortic lesion area and positively correlated with the expression of multiple adipose browning-associated genes. Adeno-associated viral delivery of Fst (AAV1-FST344) in Ldlr−/− mice significantly reduced aortic lesion area, improved plasma lipid profiles, and decreased expression of adhesion (VCAM1) and inflammatory (iNOS, TNF-α) markers in white adipose tissue (WAT), liver, and heart. Fst gene delivery also markedly increased uncoupling protein 1 (UCP1) expression in WAT, consistent with WAT browning. Integrated correlation analyses of Fst expression with tissue metabolites, together with plasma metabolite–lesion associations identified in the HMDP, implicated the arginase 1 (Arg1)-mediated metabolic pathway as a key regulator of atherogenesis. Consistent with these findings, Arg1 expression was significantly elevated in WAT, liver, and heart of AAV1-FST344-treated mice and in wild-type versus Fst-knockout mouse embryonic fibroblasts (MEFs). Immunostaining localized Arg1 predominantly to CD68+ macrophages in heart and liver. Given recent evidence identifying Arg1 as a novel mediator of efferocytosis, these findings suggest that Arg1 may promote macrophage metabolic reprogramming and resolution of inflammation by enhancing the clearance of apoptotic cells. Furthermore, Fst gene delivery increased the expression of fibroblast growth factor 21 (Fgf21) and adiponectin (AdipoQ) in WAT. Collectively, these findings identify Fst as a novel anti-atherogenic regulator that protects against vascular disease by promoting adipose browning, improving lipid metabolism, and activating Arg1-mediated metabolic pathways.