Visceral adipose tissue-directed FGF21 gene therapy improves metabolic and immune health in BTBR mice.

Fibroblast growth factor 21 (FGF21) is a peptide hormone that serves as a potent effector of energy homeostasis. Increasingly, FGF21 is viewed as a promising therapeutic agent for type 2 diabetes, fatty liver disease, and other metabolic complications. Exogenous administration of native FGF21 peptide has proved difficult due to unfavorable pharmacokinetic properties. Here, we utilized an engineered serotype adeno-associated viral (AAV) vector coupled with a dual-cassette design to selectively overexpress FGF21 in visceral adipose tissue of insulin-resistant BTBR T+Itpr3tf/J (BTBR) mice. Under high-fat diet conditions, a single, low-dose intraperitoneal injection of AAV-FGF21 resulted in sustained benefits, including improved insulin sensitivity, glycemic processing, and systemic metabolic function and reduced whole-body adiposity, hepatic steatosis, inflammatory cytokines, and adipose tissue macrophage inflammation. Our study highlights the potential of adipose tissue as a FGF21 gene-therapy target and the promise of minimally invasive AAV vectors as therapeutic agents for metabolic diseases.