Mechanism of the effect of glycosyltransferase GLT8D2 on fatty liver

Yutao Zhan, Fei Zhao, Ping Xie, Leping Zhong, Dongnian Li, Qujing Gai, Li Li, Hongshan Wei, Lingqiang Zhang, Wei An, Yutao Zhan, Fei Zhao, Ping Xie, Leping Zhong, Dongnian Li, Qujing Gai, Li Li, Hongshan Wei, Lingqiang Zhang, Wei An

Abstract

Background: Recent studies have shown that some glycosyltransferases are involved in the development of nonalcoholic fatty liver disease (NAFLD). The objective of this study was to explore the effect and mechanism of glycosyltransferase GLT8D2 on fatty liver.

Methods: Rat model of NAFLD was established by induction with high-fat-diet. The GLT8D2 expression in rat liver was examined using immunohistochemistry. Oil Red O staining and triglyceride assay were used to measure the effect of abnormal GLT8D2 expression on lipid accumulation in HepG2 cells. The expression levels of lipid metabolism-related key molecules, namely sterol regulatory element-binding protein-1c (SREBP-1c), stearoyl-coA desaturase (SCD), carnitine palmitoyltransferase-1 (CPT1) and microsomal triglyceride transfer protein (MTP), in HepG2 cells with abnormal GLT8D2 expression were determined by western blot analyses.

Results: The expression of GLT8D2 was higher in the liver of rats with NAFLD than in the control rats, and GLT8D2 was mainly located around lipid droplets in hepatocytes. GLT8D2 expression increased in steatosis HepG2 cells compared with that in normal HepG2 cells. GLT8D2 positively regulated lipid droplet accumulation and triglyceride content in HepG2 cells. Upregulation or knockdown of GLT8D2 had no effect on the expressions of SREBP-1c, SCD or CPT-1 proteins in HepG2 cells. However, GLT8D2 expression negatively regulated the expression of MTP protein in HepG2 cells.

Conclusion: GLT8D2 participated in NAFLD pathogenesis possibly by negatively regulating MTP expression. Specific inhibition of GLT8D2 via an antagonistic strategy could provide a potential candidate approach for treatment of NAFLD.

Figures

Figure 1
Figure 1
Successful inducement of rat NAFLD models. Specimens of rat liver were stained with HE (×200). (A) No obvious hepatocyte steatosis was found in control rat liver. (B) hepatocyte steatosis was obvious in NAFLD model rat liver.
Figure 2
Figure 2
The expression of GLT8D2 in rat livers. GLT8D2 expression in rat livers was detected by immunohistochemistry (×400). (A) GLT8D2 expression was scattered in control rat liver. (B) GLT8D2 expression increased in NAFLD rat liver. GLT8D2 expression surrounded mainly the lipid droplets. Rat NAFLD model was induced by Lieber-DeCarli liquid diet for 7 weeks.
Figure 3
Figure 3
The effect of OA on GLT8D2 expression in HepG2 cells. HepG2 cells were treated with 0, 100 and 200 μM OA for 72 h, and then collected for western blot analysis. The GLT8D2 expression in HepG2 cells increased with the increase of OA concentration.
Figure 4
Figure 4
The effect of GLT8D2 abnormality on intracellular lipid droplet in HepG2 cells. Intracellular lipid droplet was tested by staining with Oil Red O. Enhanced GLT8D2 for 72 h increased lipid droplet accumulation in HepG2 cells with or without OA, especially in HepG2 cells with OA. Inhibitory GLT8D2 for 72 decreased lipid accumulation in HepG2 cells with OA. (A) HepG2 cells. (B) HepG2 cells with GLT8D2 transfection. (C) HepG2 cells GLT8D2 RNA interference. (D) HepG2 cells with OA. (E) HepG2 cells with OA and GLT8D2 transfection. (F) HepG2 cells with OA and GLT8D2 RNA interference.
Figure 5
Figure 5
The effect of GLT8D2 abnormality on triglyceride content in HepG2 cells. (A) Enhanced GLT8D2 increased triglyceride content in HepG2 cells with or without OA. (B) Inhibitory GLT8D2 decreased triglyceride content in HepG2 cells with OA. Data are expressed as means ± SD (n = 6); *p < 0.05 compared with cells with normal GLT8D2, respectively.
Figure 6
Figure 6
The effect of GLT8D2 abnormality on the expressions of lipid synthesis and metabolism-related molecules (SREBP-1c, SCD, MTP and CPT-1). (A) Enhanced GLT8D2 decreased MTP expression in HepG2 cells with or without OA. Enhanced GLT8D2 has not obvious affect on the SREBP-1c, SCD and CPT-1 expressions in HepG2 cells with or without OA. (B) Inhibitory GLT8D2 increased MTP expression in HepG2 cells with or without OA. Inhibitory GLT8D2 has not obvious affect on the SREBP-1c, SCD and CPT-1 expressions in HepG2 cells with or without OA. Data are expressed as mean ± SD (n = 6); *p < 0.05 compared with cells with normal GLT8D2, respectively. White square without GLT8D2 and without OA. Light gray square with GLT8D2 and without OA. Dark gray square without GLT8D2 and with OA. Black square with GLT8D2 and with OA.

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