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Phospholipase D1 deficiency in mice causes nonalcoholic fatty liver disease via an autophagy defect.

ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of triglycerides (TG) as lipid droplets in the liver. Although lipid-metabolizing enzymes are considered important in NAFLD, the involvement of phospholipase D1 (PLD1) has not yet been studied. Here, we show that the genetic ablation of PLD1 in mice induces NAFLD due to an autophagy defect. PLD1 expression was decreased in high-fat diet-induced NAFLD. Subsequently, PLD1 deficiency led to an increase in hepatic TGs and liver weight. Autophagic flux was blocked in Pld1^-/- hepatocytes, with decreased β-oxidation rate, reduced oxidation-related gene expression, and swollen mitochondria. The dynamics of autophagy was restored by treatment with the PLD product, phosphatidic acid (PA) or adenoviral PLD1 expression in Pld1^-/- hepatocytes, confirming that lysosomal PA produced by PLD1 regulates autophagy. Notably, PLD1 expression in Pld1^-/- liver significantly reduced hepatic lipid accumulation, compared with Pld1^-/- liver. Thus, PLD1 plays an important role in hepatic steatosis via the regulation of autophagy.

SUBMITTER: Hur JH

PROVIDER: S-EPMC5156943 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Phospholipase D1 deficiency in mice causes nonalcoholic fatty liver disease via an autophagy defect.

Hur Jang Ho JH Park Shi-Young SY Dall'Armi Claudia C Lee Jae Sung JS Di Paolo Gilbert G Lee Hui-Young HY Yoon Mee-Sup MS Min Do Sik DS Choi Cheol Soo CS

Scientific reports 20161215

Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of triglycerides (TG) as lipid droplets in the liver. Although lipid-metabolizing enzymes are considered important in NAFLD, the involvement of phospholipase D1 (PLD1) has not yet been studied. Here, we show that the genetic ablation of PLD1 in mice induces NAFLD due to an autophagy defect. PLD1 expression was decreased in high-fat diet-induced NAFLD. Subsequently, PLD1 deficiency led to an increase in hepatic TGs and ...[more]

PMID: 27976696

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Project description:Background & aimsPhospholipase D1 (PLD1), a phosphatidylcholine-hydrolysing enzyme, is involved in cellular lipid metabolism. However, its involvement in hepatocyte lipid metabolism and consequently non-alcoholic fatty liver disease (NAFLD) has not been explicitly explored.MethodsNAFLD was induced in hepatocyte-specific Pld1 knockout (Pld1(H)-KO) and littermate Pld1 flox/flox (Pld1-Flox) control mice feeding a high-fat diet (HFD) for 20 wk. Changes of the lipid composition in the liver were compared. Alpha mouse liver 12 (AML12) cells and mouse primary hepatocytes were incubated with oleic acid or sodium palmitate in vitro to explore the role of PLD1 in the development of hepatic steatosis. Hepatic PLD1 expression was evaluated in liver biopsy samples in patients with NAFLD.ResultsPLD1 expression levels were increased in the hepatocytes of patients with NAFLD and HFD-fed mice. Compared with Pld1-Flox mice, Pld1(H)-KO mice exhibited decreased plasma glucose and lipid levels as well as lipid accumulation in liver tissues after HFD feeding. Transcriptomic analysis showed that hepatocyte-specific deficiency of PLD1 decreased Cd36 expression in steatosis liver tissues, which was confirmed at the protein and gene levels. In vitro, specific inhibition of PLD1 with VU0155069 or VU0359595 decreased CD36 expression and lipid accumulation in oleic acid- or sodium palmitate-treated AML12 cells or primary hepatocytes. Inhibition of hepatocyte PLD1 significantly altered lipid composition, especially phosphatidic acid and lysophosphatidic acid levels in liver tissues with hepatic steatosis. Furthermore, phosphatidic acid, the downstream product of PLD1, increased the expression levels of CD36 in AML12 cells, which was reversed by a PPARγ antagonist.ConclusionsHepatocyte-specific Pld1 deficiency ameliorates lipid accumulation and NAFLD development by inhibiting the PPARγ/CD36 pathway. PLD1 may be a new target for the treatment of NAFLD.Impact and implicationsThe involvement of PLD1 in hepatocyte lipid metabolism and NAFLD has not been explicitly explored. In this study, we found that the inhibition of hepatocyte PLD1 exerted potent protective effects against HFD-induced NAFLD, which were attributable to a reduction in PPARγ/CD36 pathway-mediated lipid accumulation in hepatocytes. Targeting hepatocyte PLD1 may be a new target for the treatment of NAFLD.

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Phospholipase D1 deficiency in mice causes nonalcoholic fatty liver disease via an autophagy defect.

Publications

Phospholipase D1 deficiency in mice causes nonalcoholic fatty liver disease via an autophagy defect.

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