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Hepatic CPT1A facilitates liver-adipose cross-talk via induction of FGF21

ABSTRACT: Hepatosteatosis, defined as excessive intrahepatic lipid accumulation, represents the first step in the development of NAFLD. However, the molecular events directly caused by hepatic lipid build-up, in terms of its impact on liver biology and other peripheral organs, remain unclear. Carnitine palmitoyltransferase 1A (CPT1A) is the rate limiting enzyme for long chain fatty acid beta-oxidation in the liver. Here we utilise hepatocyte-specific Cpt1a knockout (LKO) mice to investigate the physiological consequences of abolishing hepatic long chain fatty acid metabolism to NAFLD and systemic metabolic homeostasis. We show that LKO mice displayed more severe hepatosteatosis but were otherwise protected against diet-induced weight gain, insulin resistance, hepatic ER stress and damage in response to high fat diets. Furthermore, increased energy expenditure accompanied by enhanced adipose tissue browning was observed in LKO mice. Mechanistically, hepatic CPT1A deficiency actives the peroxisome proliferator activator alpha (PPARα)- fibroblast growth factor 21 (FGF21) axis and the elevation of FGF21 contributes to the improved liver pathology and adipose browning in HFD-treated LKO mice. Thus, our study demonstrates that liver with deficient CPT1A expression adopts a healthy steatotic status that protects against HFD-evoked liver damage and potentiates adipose browning in an FGF21-dependent manner. Inhibition of hepatic CPT1A may serve as a viable strategy for the treatment of obesity and NAFLD.

ORGANISM(S): Mus musculus

PROVIDER: GSE183650 | GEO | 2022/09/10

REPOSITORIES: GEO

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Project description:High Fructose Corn Syrup (HFCS), a sweetener rich in glucose and fructose, is nowadays widely used in beverages and processed foods, and its consumption has been correlated to the emergence and progression of Non-Alcoholic Fatty Liver Disease (NAFLD). Nevertheless, the exact molecular mechanisms by which HFCS impacts hepatic metabolism are still unclear, especially in the context of obesity. In contrast, the vast majority of current studies in the field focus either on the detrimental role of fructose on NAFLD or compare the additive impact of fructose versus glucose in this process. Besides, studies elaborating on the role of fructose in NAFLD utilize molecular fructose, rather than HFCS, thus lacking simulation of human NAFLD in a more realistic way. Herein, by engaging combined omic approaches, we sought to characterize the additive impact of HFCS on NAFLD during obesity and recognize candidate pathways and molecules which could mediate the exaggeration of steatosis under these conditions. To achieve this goal, C57BL/6 male mice were fed a normal-fat (ND), a high-fat (HFD) or a HFD supplemented with HFCS (HFD-HFCS) and upon examination of their metabolic and NAFLD phenotype, proteomic and lipidomic analyses were conducted and utilized separately or in an integrated mode to identify HFCS-related molecular alterations of the hepatic metabolic landscape. Although HFD and HFD-HFCS mice displayed comparable obesity, HFD-HFCS mice showed greater aggravation of hepatic steatosis. Importantly, the HFD-HFCS hepatic proteome was characterized by an upregulation of the enzymes implicated in de novo lipogenesis (DNL), while palmitic-acid containing diglycerides were significantly increased in the HFD-HFCS hepatic lipidome, as compared to the HFD group. Integrated omic analysis further suggested that TCA cycle overstimulation, is likely contributing towards the intensification of steatosis in the HFD-HFCS dietary theme. Overall, our results imply that HFCS may significantly contribute to NAFLD aggravation during obesity, with its fructose-rich properties being the main suspect.

Project description:Objective: Nonalcoholic fatty liver disease (NAFLD) is linked to obesity and diabetes, suggesting an important role of adipose tissue in the pathogenesis of NAFLD. Here we aim to investigate the interaction between adipose tissue and liver in NAFLD, and identify potential early plasma markers that predict NASH. Research Design and Methods: C57Bl/6 mice were chronically fed a high fat diet to induce NAFLD and compared with mice fed low fat diet. Extensive histological and phenotypical analyses coupled with a time-course study of plasma proteins using multiplex assay was performed. Results: Mice exhibited pronounced heterogeneity in liver histological scoring, leading to classification into 4 subgroups: LF-low (LFL) responders displaying normal liver morphology, LF-high (LFH) responders showing benign hepatic steatosis, HF-low (HFL) responders displaying pre-NASH with macrovesicular lipid droplets, and HF-high (HFH) responders exhibiting overt NASH characterized by ballooning of hepatocytes, presence of Mallory bodies, and activated inflammatory cells. Compared to HFL responders, HFH mice gained weight more rapidly and exhibited adipose tissue dysfunction characterized by decreased final fat mass, enhanced macrophage infiltration and inflammation, and adipose tissue remodelling. Plasma haptoglobin, IL-1β, TIMP-1, adiponectin and leptin were significantly changed in HFH mice. Multivariate analysis indicated that in addition to leptin, plasma CRP, haptoglobin, eotaxin and MIP-1α early in the intervention were positively associated with liver triglycerides. Intermediate prognostic markers of liver triglycerides included IL-18, IL-1β, MIP-1γ and MIP-2, whereas insulin, TIMP-1, GCP-2 and MPO emerged as late markers. Conclusions: Our data support the existence of a tight relationship between adipose tissue dysfunction and NASH pathogenesis and point to several novel potential predictive biomarkers for NASH. Keywords: Expression profiling by array Male wildtype C57Bl/6 mice were fed LFD or HFD for 21 weeks. Mice were divided into 4 groups based on liver histology.

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Hepatic CPT1A facilitates liver-adipose cross-talk via induction of FGF21

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