Abstract
Fibroblast growth factor 21 (FGF21) is an important liver-secreted hormone that activates thermogenesis in white and brown fat deposits. In various models of obesity, FGF21 administration consistently facilitates weight loss and improved metabolic function. Several FGF21 variants, which have been engineered to improve protein stability and solubility in solutions containing preservatives, are currently in human clinical trials. In addition, in vivo FGF21 gene therapy using viral vector is being explored as an alternative therapeutic approach. In this study, we present a simpler method of in vivo FGF21 gene therapy, in which liver-specific delivery of an unpackaged plasmid construct expressing an HA-tagged FGF21 protein increases de novo hepatic FGF21 production and secretion in mice. Our data show that FGF21 protein expression can be successfully restored into the livers of FGF21 conditional knockout mice for at least two weeks after a single tail vein injection with the expression plasmid, and that the HA-tagged protein is secreted and readily detectable in serum. In wild-type C57BL6/J mice, in vivo plasmid delivery significantly increased hepatic FGF21 protein 2.3-fold after two weeks, and was associated with reduced body mass and a 14% reduction in fasting serum glucose. In addition, elevated hepatic FGF21 levels correlated with a 27% decrease in the ratio of fat to body mass, visibly smaller subcutaneous and visceral white fat adipocytes, and a 3.3-fold increase in uncoupling protein 1-dependent mitochondrial respiration in the white fat. Together, these data suggest that in vivo plasmid delivery may potentially be an effective strategy for promoting hepatic FGF21 expression in models of obesity. We are currently testing this hypothesis with experiments in high-fat diet-challenged mice.