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We have generated the transgenic mouse line LTCFDN in which dominant negative TCF7L2 (TCF7L2DN) is specifically expressed in the liver during adulthood. Male but not female LTCFDN mice showed elevated hepatic and plasma triglyceride (TG) levels, indicating the existence of estrogen-β-cat/TCF signaling cascade that regulates hepatic lipid homeostasis. We show here that hepatic fibroblast growth factor 21 (FGF21) expression was reduced in male but not in female LTCFDN mice. The reduction was not associated with altered hepatic expression of peroxisome proliferator-activated receptor α (PPARα). In mouse primary hepatocytes (MPH), Wnt-3a treatment increased FGF21 expression in the presence of PPARα inhibitor. Results from our luciferase-reporter assay and chromatin immunoprecipitation suggest that evolutionarily conserved TCF binding motifs (TCFBs) on Fgf21 promoter mediate Wnt-3a-induced Fgf21 transactivation. Female mice showed reduced hepatic FGF21 production and circulating FGF21 level following ovariectomy (OVX), associated with reduced hepatic TCF expression and β-catenin S675 phosphorylation. Finally, in MPH, estradiol (E2) treatment enhanced FGF21 expression, as well as binding of TCF7L2 and ribonucleic acid (RNA) polymerase II to the Fgf21 promoter; and the enhancement can be attenuated by the G-protein-coupled estrogen receptor 1 (GPER) antagonist G15. Our observations hence indicate that hepatic FGF21 is among the effectors of the newly recognized E2-β-cat/TCF signaling cascade.NEW & NOTEWORTHY FGF21 is mainly produced in the liver. Therapeutic effect of FGF21 analogues has been demonstrated in clinical trials on reducing hyperlipidemia. We show here that Fgf21 transcription is positively regulated by Wnt pathway effector β-cat/TCF. Importantly, hepatic β-cat/TCF activity can be regulated by the female hormone estradiol, involving GPER. The investigation enriched our understanding on hepatic FGF21 hormone production, and expanded our view on metabolic functions of the Wnt pathway in the liver.

BACKGROUND: Dietary polyphenols including anthocyanins target multiple organs. OBJECTIVE: We aimed to assess the involvement of glucagon-like peptide 1 (GLP-1), leptin, insulin and fibroblast growth factor 21 (FGF21) in mediating metabolic beneficial effects of purified anthocyanin cyanidin-3-glucoside (Cy3G). METHODS: Intestinal proglucagon gene (Gcg; encoding GLP-1) and liver Fgf21 expression were assessed in 6-wk-old male C57BL-6J mice fed a low-fat-diet (LFD; 10% of energy from fat), alone or with 1.6 mg Cy3G/L in drinking water for 3 wk [experiment (Exp.) 1; n = 5/group]. Similar mice were fed the LFD or a high-fat diet (HFD; 60% energy from fat) with or without Cy3G for 20 wk. Half of the mice administered Cy3G also received 4 broad-spectrum antibiotics (ABs) in drinking water between weeks 11 and 14, for a total of 6 groups (n = 8/group). Metabolic tolerance tests were conducted between weeks 2 and 16. Relevant hormone gene expression and plasma hormone concentrations were assessed mainly at the end of 20 wk (Exp. 2). RESULTS: In Exp. 1, Cy3G administration increased ileal but not colonic Gcg level by 2-fold (P 3-fold, P

The metabolic hormone FGF-21 is mainly produced and released from the liver in response to nutritional stresses such as starvation, alcohol or ketogenic diet consumption. Body weight lowering and insulin signaling sensitization effects of FGF-21 and its analogues have been demonstrated in animal models or in human subjects. We show here that hepatic FGF-21 mRNA and FGF-21 protein levels were reduced in male LTCFDN, a transgenic mouse line in which canonical Wnt signaling cascade is functionally attenuated due to the expression of dominant negative transcription factor TCF7L2 in the liver, and the reduction is not associated with reduced expression of PPARα, a key transactivator of FGF-21. Furthermore, starvation-induced plasma FGF-21 elevation was also attenuated in male LTCFDN mice. Utilizing mouse primary hepatocytes, we found that FGF-21 mRNA and FGF-21 protein expression can be increased by Wnt-3a or LiCl treatment. Two evolutionarily conserved TCF binding motifs (TCFB) were then located within the mouse FGF-21 gene promoter. Luciferase and ChIP results suggest that one of them is responsible for β-cat/TCF mediated activation on FGF-21 transcription.It has been shown recently that in mouse brain tanycytes, FGF-21 secretion can be induced by palmitate treatment. We found that in mouse primary hepatocytes, palmitate but not oleate treatment increased expression of the Wnt target gene Ccnd1, which encodes cyclin D1. Our observations hence suggest that Wnt signaling cascade is involved in hepatic FGF-21 production and secretion, and the positive regulation is likely independent of fibrate/PPARα-mediated induction. Investigations on this novel hepatic signaling axis will strengthen our knowledge on the physiologically significant hormone FGF-21, leading to novel therapeutic avenues in treating impaired metabolism. Disclosure Y. Badakhshi: None. W. Shao: None. L. Tian: None. T. Jin: None. Funding Canadian Institutes of Health Research (PJT159735)

β-cat/TCF, formed by β-cat and a TCF family member, serves as the effector of the developmental canonical Wnt signaling cascade. β-cat/TCFs can also function as effectors of metabolic hormones or growth factors during adulthood. We have demonstrated recently that liver-specific expression of dominant-negative TCF7L2 (TCF7L2DN) led to impaired glucose disposal in both male and female mice. Increased hepatic lipogenesis, however, was observed in male but not in female mice. Our further investigations on such LTCFDN transgenic mouse model revealed the role of estradiol (E2) in stimulating β-cat/TCF activity. E2 reconstitution in WT mice with ovariectomy (OVX) restored the resistance of female mice to HFD induced body weight gain, insulin intolerance and elevation of hepatic lipogenic gene expression. Such beneficial effects of E2 reconstitution, however, were absent in LTCFDN female mice. To identify downstream metabolic effector/s of Wnt signaling in regulating hepatic lipogenesis, we assessed metabolic hormone expression in LTCFDN and WT littermates. Curiously, hepatic but not adipose tissue FGF-21 level was reduced in male LTCFDN mice. We then directly assessed the effect of E2 on hepatic FGF-21 expression. In WT mice on LFD diet, OVX leads to reduced hepatic FGF-21 mRNA and protein levels, associated with reduced circulating FGF-21 hormone level. These reduction was associated with reduced hepatic β-cat S675 phosphorylation, TCF7 and TCF7L2 expression. In WT mice on HFD, OVX also reduced hepatic FGF-21 mRNA and circulating FGF-21 hormone levels. Such reduction was also restored with E2 reconstitution. Our study hence identified that FGF-21 is likely among the downstream effectors of E2-Wnt signaling cascade in hepatic lipid homeostasis. Disclosure W. Shao: None. Y. Badakhshi: None. T. Jin: None. Funding Canadian Institutes of Health Research (PJT159735)