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Role for hepatic CEACAM1 in regulating fatty acid metabolism along the adipocyte-hepatocyte axis.

ABSTRACT: Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance and mediating suppression of fatty acid synthase activity. Feeding C57BL/6J male mice with a high-fat (HF) diet for 3-4 weeks triggered a >60% decrease in hepatic CEACAM1 levels to subsequently impair insulin clearance and cause systemic insulin resistance and hepatic steatosis. This study aimed at investigating whether lipolysis drives reduction in hepatic CEACAM1 and whether this constitutes a key mechanism leading to diet-induced metabolic abnormalities. Blocking lipolysis with a daily intraperitoneal injection of nicotinic acid in the last two days of a 30-day HF feeding regimen demonstrated that white adipose tissue (WAT)-derived fatty acids repressed hepatic CEACAM1-dependent regulation of insulin and lipid metabolism in 3-month-old male C57BL/6J mice. Adenoviral-mediated CEACAM1 redelivery countered the adverse metabolic effect of the HF diet on insulin resistance, hepatic steatosis, visceral obesity, and energy expenditure. It also reversed the effect of HF diet on inflammation and fibrosis in WAT and liver. This assigns a causative role for lipolysis-driven decrease in hepatic CEACAM1 level and its regulation of insulin and lipid metabolism in sustaining systemic insulin resistance, hepatic steatosis, and other abnormalities associated with excessive energy supply.

SUBMITTER: Russo L

PROVIDER: S-EPMC5321226 | biostudies-other | 2016 Dec

REPOSITORIES: biostudies-other

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Role for hepatic CEACAM1 in regulating fatty acid metabolism along the adipocyte-hepatocyte axis.

Russo Lucia L Ghadieh Hilda E HE Ghanem Simona S SS Al-Share Qusai Y QY Smiley Zachary N ZN Gatto-Weis Cara C Esakov Emily L EL McInerney Marcia F MF Heinrich Garrett G Tong Xin X Yin Lei L Najjar Sonia M SM

Journal of lipid research 20161024 12

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance and mediating suppression of fatty acid synthase activity. Feeding C57BL/6J male mice with a high-fat (HF) diet for 3-4 weeks triggered a >60% decrease in hepatic CEACAM1 levels to subsequently impair insulin clearance and cause systemic insulin resistance and hepatic steatosis. This study aimed at investigating whether lipolysis drives reduction in hepatic CEA ...[more]

PMID: 27777319

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Project description:Melanocortins mediate their biological functions via five different melanocortin receptors (MC1R - MC5R). MC1R is expressed in the skin and leukocytes and is thus involved in the regulation of skin pigmentation and inflammatory responses. MC1R is also present in the liver and white adipose tissue, but its functional role in these tissues is unclear. This study aimed at determining the regulatory role of MC1R in fatty acid metabolism. Recessive yellow (Mc1re/e) mice, a model of global MC1R deficiency, and hepatocyte-specific MC1R deficient mice (Mc1r LKO) were fed a chow or Western diet for 12 weeks. The mouse models were characterized for body weight and composition, adipose tissue mass, adipocyte size, glucose metabolism and lipid metabolism. Furthermore, qPCR and RNA sequencing analyses were used to investigate gene expression profiles in the liver and adipose tissue. HepG2 cells and primary mouse hepatocytes were to study the effects of pharmacological MC1R activation. Chow- and Western diet-fed Mc1re/e showed increased liver weight, white adipose tissue mass and plasma triglyceride (TG) concentration compared to wild type mice. This phenotype occurred without significant changes in food intake, body weight, physical activity or glucose metabolism. Mc1r LKO mice displayed a similar phenotype characterized by larger fat depots, increased adipocyte hypertrophy and enhanced accumulation of TGs in the liver and plasma. In terms of gene expression, markers of de novo lipogenesis, inflammation and apoptosis were upregulated in the liver of Mc1r LKO mice, while enzymes regulating lipolysis were downregulated in white adipose tissue of these mice. In cultured hepatocytes, selective activation of MC1R reduced ChREBP expression, which is a central transcription factor for lipogenesis. Hepatocyte-specific loss of MC1R disturbs fatty acid metabolism in the liver and leads to an obesity phenotype characterized by enhanced adipocyte hypertrophy and TG accumulation in the liver and circulation.

Project description:Aims/introductionHigh glucose increases the accumulation of lipid droplets in hepatocytes, which eventually results in nonalcoholic fatty liver disease in patients with diabetes. However, the specific mechanism or communication between adipocyte and hepatocyte lipid metabolism is still ambiguous.Materials and methodsIn this study, exosomes released from human adipocytes were isolated and identified by their morphology, size, and marker proteins by using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting (WB). Gene expression was detected by qRT-PCR and WB. Lipid accumulation was determined by oil red O staining and analyses of total cholesterol (TC) and triglyceride (TG) content.ResultsOur results showed that co-culture of HepG2 cells with adipocytes under high glucose conditions stimulated lipid deposition and LINC01705 expression in the HepG2 cells. Exosomes extracted from adipocytes cultured under high glucose conditions had higher levels of LINC01705 than exosomes extracted from adipocytes cultured under normal glucose conditions. Moreover, LINC01705 expression was also elevated in exosomes extracted from diabetes patients when compared with exosomes isolated from normal volunteers, and exosomes from patients who had diabetes complicated with fatty liver (DCFL) had the highest levels of LINC01705 expression. Treatment of HepG2 cells with exosomes extracted from high glucose-stimulated adipocytes promoted lipid deposition and LINC01705 expression in HepG2 cells. Further experiments showed that overexpression of LINC01705 promoted HepG2 lipid metabolism, while inhibition of LINC01705 had the opposite effect. Mechanistically, LINC01705 competitively bound to miR-552-3p, and treatment with miR-552-3p inhibitor reversed the effects induced by LINC01705 knockdown. Moreover, miR-552-3p was found to regulate the transcription activity of LXRα and thereby modulate lipid metabolism-related gene expression.ConclusionsWhen taken together, our findings showed that high glucose increased the LINC01705 levels in adipocyte exosomes, and thereby improved HepG2 lipid accumulation via an miR-552-3p/LXR axis.

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Role for hepatic CEACAM1 in regulating fatty acid metabolism along the adipocyte-hepatocyte axis.

Publications

Role for hepatic CEACAM1 in regulating fatty acid metabolism along the adipocyte-hepatocyte axis.

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