FGFR4 prevents hyperlipidemia and insulin resistance but underlies high-fat diet induced fatty liver.
OBJECTIVE
Fibroblast growth factor (FGF) family signaling largely controls cellular homeostasis through short-range intercell paracrine communication. Recently FGF15/19, 21, and 23 have been implicated in endocrine control of metabolic homeostasis. The identity and location of the FGF receptor isotypes that mediate these effects are unclear. The objective was to determine the role of FGFR4, an isotype that has been proposed to mediate an ileal FGF15/19 to hepatocyte FGFR4 axis in cholesterol homeostasis, in metabolic homeostasis in vivo.


METHODS
FGFR4(-/-) mice-mice overexpressing constitutively active hepatic FGFR4--and FGFR4(-/-) with constitutively active hepatic FGFR4 restored in the liver were subjected to a normal and a chronic high-fat diet sufficient to result in obesity. Systemic and liver-specific metabolic phenotypes were then characterized.


RESULTS
FGFR4-deficient mice on a normal diet exhibited features of metabolic syndrome that include increased mass of white adipose tissue, hyperlipidemia, glucose intolerance, and insulin resistance, in addition to hypercholesterolemia. Surprisingly, the FGFR4 deficiency alleviated high-fat diet-induced fatty liver in obese mice, which is also a correlate of metabolic syndrome. Restoration of FGFR4, specifically in hepatocytes of FGFR4-deficient mice, decreased plasma lipid levels and restored the high-fat diet-induced fatty liver but failed to restore glucose tolerance and sensitivity to insulin.


CONCLUSIONS
FGFR4 plays essential roles in systemic lipid and glucose homeostasis. FGFR4 activity in hepatocytes that normally serves to prevent systemic hyperlipidemia paradoxically underlies the fatty liver disease associated with chronic high-fat intake and obesity.
Huang
Xinqiang
X
Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, 2121 W. Holcombe Blvd., Houston, TX 77030, USA.
Yang
Chaofeng
C
Luo
Yongde
Y
Jin
Chengliu
C
Wang
Fen
F
McKeehan
Wallace L
WL
D000273:Adipose Tissue / Q000473:pathology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D004041:Dietary Fats / Q000009:adverse effects*; D005234:Fatty Liver / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D006949:Hyperlipidemias / Q000235:genetics / Q000517:prevention & control*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008055:Lipids / Q000502:physiology; D008099:Liver / Q000033:anatomy & histology / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009929:Organ Size; D012333:RNA, Messenger / Q000235:genetics; D051499:Receptor, Fibroblast Growth Factor, Type 4 / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*
D001786:Blood Glucose; D004041:Dietary Fats; D007328:Insulin; D008055:Lipids; D012333:RNA, Messenger; C496371:FGFR4 protein, human; C496372:Fgfr4 protein, mouse; D051499:Receptor, Fibroblast Growth Factor, Type 4; D005947:Glucose