Reciprocal regulation of hepatic TGF-β1 and Foxo1 controls gluconeogenesis and energy expenditure
Obesity and insulin resistance are risk factors for the pathogenesis of T2D. Here we report that hepatic TGF-β1 expression positively correlates with obesity and insulin resistance in mice and humans. Hepatic TGF-β1 deficiency decreased blood glucose in lean mice, and improved glucose and energy dysregulations in diet-induced obese (DIO) mice and diabetic mice. Conversely, overexpression of TGF-β1 in the liver exacerbated metabolic dysfunctions in DIO mice. Mechanistically, hepatic TGF-β1 and Foxo1 are reciprocally regulated: fasting or insulin resistance caused Foxo1 activation, increasing TGF-β1 expression, which in turn activated protein kinase A, stimulating Foxo1-S273 phosphorylation to promote Foxo1-mediated gluconeogenesis. Disruption of TGF-β1→Foxo1→TGF-β1 looping by deleting TGF-β1 receptor II in the liver or by blocking Foxo1-S273 phosphorylation ameliorated hyperglycemia and improved energy metabolism in adipose tissues. Taken together, our studies reveal that hepatic TGF-β1→Foxo1→TGF-β1 looping could serve as a potential therapeutic target for prevention and treatment of obesity and T2D.