Hepatic Slug epigenetically promotes liver lipogenesis, fatty liver disease, and type 2 diabetes
Yan Liu, Haiyan Lin, Lin Jiang, Qingsen Shang, Lei Yin, Jiandie D. Lin, Wen-Shu Wu, Liangyou Rui
Yan Liu, Haiyan Lin, Lin Jiang, Qingsen Shang, Lei Yin, Jiandie D. Lin, Wen-Shu Wu, Liangyou Rui
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Research Article Hepatology Metabolism

Hepatic Slug epigenetically promotes liver lipogenesis, fatty liver disease, and type 2 diabetes

Abstract

De novo lipogenesis is tightly regulated by insulin and nutritional signals to maintain metabolic homeostasis. Excessive lipogenesis induces lipotoxicity, leading to nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Genetic lipogenic programs have been extensively investigated, but epigenetic regulation of lipogenesis is poorly understood. Here, we identified Slug as an important epigenetic regulator of lipogenesis. Hepatic Slug levels were markedly upregulated in mice by either feeding or insulin treatment. In primary hepatocytes, insulin stimulation increased Slug expression, stability, and interactions with epigenetic enzyme lysine-specific demethylase-1 (Lsd1). Slug bound to the fatty acid synthase (Fasn) promoter where Slug-associated Lsd1 catalyzed H3K9 demethylation, thereby stimulating Fasn expression and lipogenesis. Ablation of Slug blunted insulin-stimulated lipogenesis. Conversely, overexpression of Slug, but not a Lsd1 binding-defective Slug mutant, stimulated Fasn expression and lipogenesis. Lsd1 inhibitor treatment also blocked Slug-stimulated lipogenesis. Remarkably, hepatocyte-specific deletion of Slug inhibited the hepatic lipogenic program and protected against obesity-associated NAFLD, insulin resistance, and glucose intolerance in mice. Conversely, liver-restricted overexpression of Slug, but not the Lsd1 binding-defective Slug mutant, had the opposite effects. These results unveil an insulin/Slug/Lsd1/H3K9 demethylation lipogenic pathway that promotes NAFLD and type 2 diabetes.

Authors

Yan Liu, Haiyan Lin, Lin Jiang, Qingsen Shang, Lei Yin, Jiandie D. Lin, Wen-Shu Wu, Liangyou Rui

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Figure 1

Hepatic Slug is upregulated by insulin and is elevated in NAFLD.

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Hepatic Slug is upregulated by insulin and is elevated in NAFLD. (A) C57...
(A) C57BL/6J males were overnight-fasted and then fed again for 3 hours. Liver nuclear extracts were immunoblotted with the indicated antibodies. (B) C57BL/6J males were fasted overnight and treated with insulin (1 U/kg body weight for 4 hours). Liver nuclear extracts were immunoblotted with indicated antibodies. Slug levels were normalized to lamin A/C levels (n = 3 per group). (C) Liver Slug mRNA abundance (normalized to 36B4 levels; n = 3 per group). (D) Primary hepatocytes were pretreated with wortmannin (100 nM) or MK2066 (100 nM) for 0.5 hours before insulin stimulation (100 nM for 2 hours). Nuclear extracts and cell extracts were immunoblotted with the indicated antibodies. (E and F) Primary hepatocytes were transduced with Slug adenoviral vectors, treated with insulin in the presence or absence of cycloheximide. Nuclear Slug levels were normalized to lamin A/C (n = 3 per group). (G) Primary hepatocytes were transduced with Slug adenoviral vectors for 12 hours, and then stimulated with insulin (100 nM for 1 hour) in the presence or absence of MG132 (5 μM). Cell extracts were immunoprecipitated with antibody against Slug and immunoblotted with the indicated antibodies. (H) Liver Slug mRNA levels (normalized to 36B4 levels). Chow: HFD (n = 5, for 10 weeks); ob/ob (n = 5, 14 weeks of age). (I) Liver nuclear extracts were prepared from WT and ob/ob mice at 14 weeks of age or from WT mice fed a chow diet or HFD for 10 weeks, and immunoblotted with antibodies against Slug and lamin A/C. (J) Liver SLUG mRNA levels in NASH patients (n = 11) and normal subjects (Con) (n = 10) (normalized to GAPDH). Proteins were resolved in parallel gels. Data are presented as mean ± SEM. *P < 0.05, 2-tailed Student’s t test (B, C, and J) or 1-way ANOVA/Sidak posttest (H).