Obesity is associated with an overactive endocannabinoid system, and selective blockade of CB1R in peripheral tissues, including the liver, reverses HFD-induced metabolic abnormalities by restoring normal lipid and glucose homeostasis and avoid unwanted adverse neuropsychiatric effects. The CB1R inverse agonist JD5037 has been shown equal effective with its brain-penetrant compound in reducing appetite, body weight, hepatic steatosis, and insulin resistance. Fibroblast growth factor-21 (FGF21) has emerged as a major endocrine regulator derived from the liver that reduces adiposity and hepatic steatosis and improves glucose tolerance and insulin sensitivity, with changes similar to those induced by CB1R blockade. Here we investigated whether FGF21 mediate the metabolic effects of CB1R blockade by JD5037 in DIO mice. In C57BL/6J wild-type mice, HFD caused a robust increase in hepatic Fgf21 mRNA and serum FGF21 levels, which were reversed by chronic peripheral CB1R antagonist JD5037 treatment to levels observed in STD or vehicle-treated hepatocyte-specific CB1R-/- (hCB1-/-) mice, indicating activation of CB1R in the liver is largely involved in HFD-induced “FGF21-resistant” state. In contrast, the expression of the FGF21 receptor Fgfr1 and co-receptor β-klotho (Klb) were dramatically reduced by HFD in both epididymal fat and brain tissue in wild-type mice, and these effects were reversed by JD5037 treatment. To address whether FGF21 mediated the metabolic effects of CB1R blockade, we repeated JD5037 treatment in liver-specific FGF21-/- (hFGF21-/-) mice. Surprisingly, JD5037 treatment was almost equally effective in both HFD-fed wild-type and in hFGF21-/- mice in reducing body weight and hepatic steatosis, attenuating hyperinsulinemia and hyperleptinemia. The current data suggest that peripheral CB1R blockade by inverse agonist in obese mice improves insulin sensitivity and energy expenditure independently of hepatic FGF21.
J. Liu: None.
National Institutes of Health