Long non-coding RNA GAS5 contributes to the progression of nonalcoholic fatty liver disease by targeting the microRNA-29a-3p/NOTCH2 axis

Abstract

Long non-coding RNAs (lncRNAs) have been widely recognized as critical players in the development of nonalcoholic fatty liver disease (NAFLD), one of the most prevalent liver diseases globally. In this study, we established a HFD-induced NAFLD mouse model and explored the role of lncRNA GAS5 in NAFLD progression and its possible underlying mechanisms. We showed that NAFLD activity score was elevated in the HFD mice. GAS5 knockdown attenuated HFD-induced hepatic steatosis and lipid accumulation and reduced NAFLD activity score in HFD mice. In addition, GAS5 knockdown reduced serum triglyceride cholesterol levels and inhibited alanine aminotransferase and aspartate aminotransferase activities in HFD mice. Moreover, GAS5 overexpression enhanced NOTCH2 levels in liver cells and promoted NAFLD progression by sponging miR-29a-3p in vivo. Furthermore, miR-29a-3p inhibited NAFLD progression by targeting NOTCH2 in vivo. Overall, our results indicated that GAS5 acts as a sponge of miR-29a-3p to increase NOTCH2 expression and facilitate NAFLD progression by targeting the miR-29a-3p/NOTCH2 axis and demonstrated a new GAS5-mediated mechanism underlying NAFLD development, suggesting that GAS5 could be a potential therapeutic target of NAFLD.Abbreviations: Alanine aminotransferase: ALT; Aspartate aminotransferase: AST; Enzyme linked immunosorbent assay: ELISA; Hepatocellular carcinoma: HCC; High-fat diet: HFD; Long non-coding RNA: Lnc RNA; Long non-coding RNA GAS5: GAS5; MicroRNAs: MiRNAs; Nonalcoholic fatty liver disease: NAFLD; Quantitative reverse transcription PCRs: RT-qPCRs; siRNA negative control: si-NC; Total cholesterol: TC; Triglyceride: TG.

Keywords: NAFLD; NOTCH2; lncRNA GAS5; miR-29a-3p; progression.

Figure 1.

GAS5, miR-29a-3p, and NOTCH2 expression levels are changed in the NAFLD mouse model. (a-h) NAFLD mouse model was established (n = 5). (a) Hepatic TG levels were assessed by ELISA. (b) Oil Red O staining of liver tissues. (c) NAFLD activity score. (d) Serum TC and TG levels were analyzed by ELISA. (e) Serum AST and ALT levels were tested by ELISA. (f) GAS5 expression was determined by qPCR. (g) MiR-29a-3p expression was examined by qPCR. (h) NOTCH2 expression was measured by qPCR. (i) NOTCH2 expression was analyzed by Western blot. Data are presented as mean ± SD. * P < 0.05, ** P < 0.01.

Figure 2.

GAS5 promotes NAFLD progression in vivo. (a-f) NAFLD mouse model was established. (a) GAS5 expression in mouse liver tissues was determined by qPCR assays. (b) Hepatic steatosis was measured by H&E staining. (c) Oil Red O staining of mouse liver tissues. (d) NAFLD activity score was quantified. (e) Serum TC and TG levels were analyzed by ELISA. (f) Serum AST and ALT levels were tested by ELISA. Data are presented as mean ± SD. * P < 0.05, ** P < 0.01.

Figure 3.

GAS5 enhances NOTCH2 expression by sponging miR-29a-3p. (a) Interactions of miR-29a-3p with GAS5 and NOTCH2 were predicted by bioinformatic analyses using ENCORI (http://starbase.sysu.edu.cn/index.php) and Targetscan (http://www.targetscan.org/vert_72/). (b and c) LO2 cells were treated with control mimic or miR-29a-3p mimic. (b) MiR-29a-3p expression was examined by qPCR. (c) Luciferase activities were determined. (d) Interaction between GAS5 and miR-29a-3p was analyzed by RNA pull-down assays. (e) NOTCH2 expression in liver tissues was measured by qPCR. (f and g) GAS5 shRNA or corresponding control shRNA were transfected in LO2 cells. (f) miR-29a-3p expression was tested by qPCR. (g) NOTCH2 expression was measured by qPCR. Data are presented as mean ± SD. * P < 0.05, ** P < 0.01.

Figure 4.

GAS5 promotes NAFLD progression by targeting miR-29a-3p in vivo. (a-f) NAFLD mouse model was established. (a) Hepatic steatosis was measured by H&E staining. (b) Oil Red O staining of liver tissues. (c) NAFLD activity score was quantified. (d) Serum TC and TG levels were analyzed by ELISA. (e) Serum AST and ALT levels were tested by ELISA. Data are presented as mean ± SD. * P < 0.05, ** P < 0.01.

Figure 5.

MiR-29a-3p inhibits NAFLD progression by targeting NOTCH2 in vivo. (a-f) NAFLD mouse model was established. HFD mice were injected with miR-29a-3p inhibitor or co-injected with miR-29a-3p inhibitor and NOTCH2 shRNA. (a) H&E staining of hepatic steatosis. (b) Oil Red O staining of liver tissues. (c) NAFLD activity score was quantified. (d) Serum TC and TG levels were analyzed by ELISA. (e) Serum AST and ALT levels were tested by ELISA. (f) Notch2 expression was examined using Western blot. Data are presented as mean ± SD. * P < 0.05, ** P < 0.01.