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Feeding activates FGF15-SHP-TFEB-mediated lipophagy in the gut

ABSTRACT: Lysosome-mediated macroautophagy, including lipophagy, is activated under nutrient deprivation but is repressed after feeding. We show that feeding unexpectedly activates intestinal lipophagy in a manner dependent on both the orphan nuclear receptor, small heterodimer partner (SHP/NR0B2), and the late fed-state gut hormone, fibroblast growth factor-15/19 (FGF15/19). Postprandial intestinal triglycerides (TGs) and apolipoprotein-B48 (ApoB48), the TG-rich chylomicron marker, were elevated in SHP-knockout and FGF15-knockout mice. Genomic analyses in mouse intestine revealed that SHP partners with the key lysosomal activator, transcription factor-EB (TFEB), upregulating autophagy/lipolysis network genes after feeding. In HT29 intestinal cells, FGF19 treatment activated lipophagy in a manner dependent on both SHP and TFEB, reducing TG and ApoB48 levels. Mechanistically, feeding-induced FGF15/19 signaling increases nuclear localization of TFEB and SHP via PKCβ/ζ-mediated phosphorylation, leading to transcriptional induction of Ulk1 and Atgl. Collectively, these results demonstrate that after feeding, FGF15/19-activated SHP and TFEB paradoxically activate gut lipophagy, limiting postprandial TG levels. As excess lipids cause dyslipidemia and obesity, the FGF15/19-SHP-TFEB axis that reduces intestinal TGs via lipophagic activation provides promising therapeutic targets for obesity-associated metabolic disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE197549 | GEO | 2022/04/22

REPOSITORIES: GEO

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Project description:Background and Aims: Inflammasome-mediated caspase-1 activity regulates the maturation and release of the pro-inflammatory cytokines interleukin (IL)-1M-CM-^_ and IL-18. Recently, we showed that caspase-1 deficiency strongly reduces high fat diet-induced adiposity although the mechanism is still unclear. We now aimed to elucidate the mechanism by which caspase-1 deficiency reduces modulates resistance to high fat diet-feeding fat accumulation in adipose tissue by focusing on the role of caspase-1 in the regulation of triglyceride (TG)-rich lipoprotein metabolism. Methods: Caspase-1 deficient and wild-type mice (both C57Bl/6 background) were used to determine postprandial TG kinetics, intestinal TG absorption, VLDL-TG production as well as TG clearance, all of which strongly contribute to the supply of TG for storage in adipose tissue. Micro-array and qPCR analysis were used to unravel intestinal and hepatic metabolic pathways involved. Results: Caspase-1 deficiency reduced the postprandial response to an oral lipid load, while tissue specific clearance of TG-rich lipoproteins was not changed. Indeed, an oral olive oil gavage containing [3H]TG revealed that caspase-1 deficiency significantly decreased intestinal chylomicron-TG production and reduced the uptake of [3H]TG-derived FA by liver, muscle, and adipose tissue. Similarly, caspase-1 deficiency reduced the hepatic VLDL-TG production without reducing VLDL-apoB production, despite an elevated hepatic TG content. Pathway analysis revealed that caspase-1 deficiency reduces intestinal and hepatic expression of genes involved in lipogenesis. Conclusions: Absence of caspase-1 reduces assembly and secretion of TG-rich lipoproteins, thereby reducing the availability of TG-derived FA for uptake by peripheral organs including adipose tissue. We anticipate that caspase-1 represents a novel link between innate immunity and lipid metabolism. Keywords: Expression profiling by array Wild-type (WT) and Casp1-null mice were maintained at lab chow. Animals, aged between 14 and 16 weeks (n=3 per genotype), were killed and liver and intestinal segments were removed. Livers were isolated from mice that were fasted over night, whereas intesines were removed from mice 2 hrs after they received an oral lipid load.Total RNA was isolated and subjected to gene expression profiling.

Project description:Bariatric surgeries such as the Vertical Sleeve Gastrectomy (VSG) are invasive but provide the most effective long-term metabolic improvements in individuals with obesity and/or Type 2 diabetes. These powerful effects of manipulating the gastrointestinal tract point to an important role of gastrointestinal signals in regulating both energy balance and metabolism. To that end, we have used mouse models of VSG to identify key gut signals that mediate these beneficial effects. Previous data from our rodent model of VSG led us to hypothesize a potential role for the hormone Fibroblast-Growth Factor15/19 (mouse/human ortholog) which pharmacologically can regulate many aspects of energy homeostasis and glucose handling. FGF15 is expressed in ileal enterocytes of the small intestine and is released postprandially. Like many other gut hormones, postprandial plasma concentrations of the human ortholog FGF19 and ileal FGF15 expression in mice increase after VSG. We generated intestinal-specific FGF15 knock out (VilCreERT2; Fgf15f/f) mice and controls, which were maintained on 60% high-fat diet. VSG resulted in increased plasma bile acid levels. However, intestinal-specific FGF15 knock out mice had considerably higher levels of circulating total and hydrophobic bile acids after VSG. Unlike what we had predicted, intestinal-specific FGF15 knock out mice lost more weight after VSG as a result of increased lean tissue loss compared to control mice. Further, the loss of bone mineral density and bone marrow adipose tissue observed after VSG in control mice was even greater in intestinal-specific FGF15 knock out mice, perhaps secondary to anemia and elevated erythropoietin/FGF23. Finally the effect of VSG to improve glucose tolerance and to reduce hepatic cholesterol was also absent in intestinal-specific FGF15 knock out mice. These data point to an important role for intestinal FGF15 to protect the organism from deleterious effects of bile acid toxicity after VSG.

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Feeding activates FGF15-SHP-TFEB-mediated lipophagy in the gut

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