Differential receptor selectivity of the FGF15/FGF19 orthologues determines distinct metabolic activities in db/db mice

Abstract

Fibroblast growth factors (FGF) 19, 21 and 23 are characterized by being endocrinely secreted and require co-receptor α-klotho or β-klotho (BKL) for binding and activation of the FGF receptors (FGFR). FGF15 is the rodent orthologue of human FGF19, but the two proteins share only 52% amino acid identity. Despite the physiological role of FGF21 and FGF19 being quite different, both lower blood glucose (BG) when administered to diabetic mice. The present study was designed to clarify why two human proteins with distinct physiological functions both lower BG in mice and if the mouse orthologue FGF15 has similar effect to FGF19 and FGF21. Recombinant human FGF19, -21 and a mouse FGF15 variant (C110S) were expressed and purified from While rhFGF19 (recombinant human fibroblast growth factor 19) and rhFGF21 (recombinant human fibroblast growth factor) bound FGFRs in complex with both human and mouse BKL, rmFGF15CS (recombinant mouse fibroblast growth factor 15 C110S) only bound the FGFRs when combined with mouse BKL. Recombinant hFGF21 and rhFGF19, but not rmFGF15CS, increased glucose uptake in mouse adipocytes, while rhFGF19 and rmFGF15CS potently decreased expression in rat hepatocytes. The lack of effect of rmFGF15CS on glucose uptake in adipocytes was associated with rmFGF15CS's inability to signal through the FGFR1c/mouse BKL complex. In mice, only rhFGF19 and rhFGF21 decreased BG while rmFGF15CS and rhFGF19, but not rhFGF21, increased total cholesterol. These data demonstrate receptor- and species-specific differential activity of FGF15 and FGF19 which should be taken into consideration when FGF19 is used as a substitute for FGF15.

Association of serum fibroblast growth factor 19 levels with arteriosclerosis parameters assessed by arterial stiffness and atherogenic index of plasma in patients with type 2 diabetes

“…Evidence from previous studies has shown that FGF19 participates in the synthesis of BA, the balance of glucose metabolism, and the reduction of weight in mice [20][21][22][23]. In accordance with our data, J.…”

Inverse Association of Serum Fibroblast Growth Factor 19 and Atherogenic Index of Plasma in Type 2 Diabetic Patients

“…Evidence from previous studies has shown that FGF19 participates in the synthesis of BA, the balance of glucose metabolism, and the reduction of weight in mice [18][19][20][21]. In accordance with our data, J.…”

FGF21 regulates hepatic metabolic pathways to improve steatosis and inflammation

“…Another central question is whether the hepatic improvements by FGF21 are related directly or indirectly. The literature is controversial as direct signaling in hepatocytes in vitro ( 72 ) and liver in vivo ( 73 ) are observed, while the liver-specific KLB KO display unaltered FGF21 sensitivity ( 74 ). The direct effect on liver may depend on the pharmacological dose ( 72 , 75 ), as FGF21 binds with higher affinity toward the FGFR1c/KLB complex compared to the FGFR3c/KLB complex ( 76 ).…”

“…The literature is controversial as direct signaling in hepatocytes in vitro ( 72 ) and liver in vivo ( 73 ) are observed, while the liver-specific KLB KO display unaltered FGF21 sensitivity ( 74 ). The direct effect on liver may depend on the pharmacological dose ( 72 , 75 ), as FGF21 binds with higher affinity toward the FGFR1c/KLB complex compared to the FGFR3c/KLB complex ( 76 ). FGFR1c is not expressed by the liver, but FGF21 may mediate its hepatic effect through FGFR3c/KLB signaling ( 76 , 77 , 78 ).…”