Heme-Regulated eIF2α Kinase Modulates Hepatic FGF21 and is Activated by PPARβ/δ Deficiency
Valverde, Ángela M.
Date of Issue2016
Lee Kong Chian School of Medicine
Fibroblast growth factor 21 (FGF21), a peptide hormone with pleiotropic effects on carbohydrate and lipid metabolism, is considered a target for the treatment of diabetes. In this study, we investigated the role of Peroxisome Proliferator-Activated Receptor (PPAR)β/δ deficiency in hepatic FGF21 regulation. Increased Fgf21 expression was observed in liver of PPARβ/δ-null mice and in mouse primary hepatocytes when this receptor was knocked down by small interfering RNA (siRNA). Increased Fgf21 was associated with enhanced protein levels in the heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI). This increase caused enhanced levels of phosphorylated eIF2α and activating transcription factor (ATF) 4, which is essential for Fgf21-induced expression. siRNA analysis demonstrated that HRI regulates Fgf21 expression in primary hepatocytes. Enhanced Fgf21 expression attenuated tunicamycin-induced endoplasmic reticulum stress, as demonstrated by using a neutralizing antibody against FGF21. Interestingly, increased Fgf21 expression in mice fed a HFD or hepatocytes exposed to palmitate was accompanied by reduced PPARβ/δ and activation of the HRI-eIF2α-ATF4 pathway. Moreover, pharmacological activation of HRI increased Fgf21 expression and reduced lipid-induced hepatic steatosis and glucose intolerance and these effects were not observed in Fgf21-null mice. Overall, these findings suggest that HRI is a potential target for regulating hepatic FGF21 levels.
© 2016 American Diabetes Association. This is the author created version of a work that has been peer reviewed and accepted for publication by Diabetes, American Diabetes Association. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.2337/db16-0155].