AMPK-Regulated Autophagy Contributes to Ursolic Acid Supplementation-Alleviated Hepatic Steatosis and Liver Injury in Chronic Alcohol-Fed Mice.

Alcoholic liver disease (ALD) is a chronic liver disease caused by long-term heavy consumption of alcohol. The pathogenesis of ALD is complex, and there is no effective clinical treatment at present. Ursolic acid (UA), a general triterpenoid with multiple biological roles, is widely distributed in plants. This study aims to explore the therapeutic effect and potential mechanisms of UA that protect against liver injury and hepatic steatosis in an ALD mouse model. In this study, we analyzed the lipid accumulation and the effect of UA treatment in a mouse model of ALD; AML12 and HepG2 cells were used to study the biological effect and potential mechanisms of UA on ethanol-induced hepatotoxicity. The morphologic and histological detections showed that UA significantly reduced alcohol-induced liver injury and hepatic steatosis. In addition, UA dramatically ameliorated alcohol-induced metabolic disorders, oxidative stress, and inflammation. Furthermore, UA treatment activated autophagy via the AMPK-ACC pathway to protect hepatocytes from lipotoxicity. Thus, these findings demonstrate that UA treatment alleviates alcoholic-induced liver injury by activating autophagy through the AMPK-ACC pathway. Therefore, UA may represent a promising candidate for the treatment of ALD.

Activation of the AMPK-SIRT1 pathway contributes to protective effects of Salvianolic acid A against lipotoxicity in hepatocytes and NAFLD in mice.

Background: Salvianolic acid A (Sal A), a natural polyphenol compound extracted from Radix Salvia miltiorrhiza (known as Danshen in China), possesses a variety of potential pharmacological activities. The aim of this study is to determine mechanisms of hepatoprotective effects of Sal A against lipotoxicity both in cultured hepatocytes and in a mouse model of fatty liver disease. Methods: High-fat and high-carbohydrate diet (HFCD)-fed C57BL/6J mice were employed to establish hepatic lipotoxicity in a mouse model. Two doses of Sal A were administered every other day via intraperitoneal injection (20 and 40 mg/kg BW, respectively). After a 10-week intervention, liver injury was detected by immunohistochemical and biochemical analyses. For in vitro studies, we used HepG2, a human hepatoma cell line, and exposed them to palmitic acid to induce lipotoxicity. The protective effects of Sal A on palmitic acid-induced lipotoxicity were examined in Sal A-pretreated HepG2 cells. Results: Sal A treatments attenuated body weight gain, liver injury, and hepatic steatosis in mice exposed to HFCD. Sal A pretreatments ameliorated palmitic acid-induced cell death but did not reverse effects of HFCD- or palmitate-induced activations of JNK, ERK1/2, and PKA. Induction of p38 phosphorylation was significantly reversed by Sal A in HFCD-fed mice but not in palmitate-treated HepG2 cells. However, Sal A rescued hepatic AMP-activated protein kinase (AMPK) suppression and sirtuin 1 (SIRT1) downregulation by both HFCD feeding in mice and exposure to palmitate in HepG2 cells. Sal A dose-dependently up-regulated p-AMPK and SIRT1 protein levels. Importantly, siRNA silencing of either AMPK or SIRT1 gene expression abolished the protective effects of Sal A on lipotoxicity. Moreover, while AMPK silencing blocked Sal A-induced SIRT1, silencing of SIRT1 had no effect on Sal A-triggered AMPK activation, suggesting SIRT1 upregulation by Sal A is mediated by AMPK activation. Conclusion: Our data uncover a novel mechanism for hepatoprotective effects of Sal A against lipotoxicity both in livers from HFCD-fed mice and palmitic acid-treated hepatocytes.

RNA Sequencing Reveals a Comprehensive Circular RNA Expression Profile in a Mouse Model of Alcoholic Liver Disease.

BACKGROUND AND AIMS: Alcoholic liver disease (ALD) is the most common liver disease and a severe mortality burden in the world. However, ALD is rarely detected at its early stages. Thus, exploration of an early event for ALD may help the prognosis and further therapy of ALD. Several circRNAs were proven as novel molecular biomarkers for the progression of chronic nonalcoholic fatty liver disease. Whether circRNAs are involved explicitly in ALD remains unknown. METHODS: The expression profile of circRNAs in an ALD mouse model was depicted by circRNA sequencing. The dysregulated circRNAs were verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bioinformatics and circRNA/microRNA (miRNA) crosstalk analyses were applied to predict the potential functions of circRNAs. Finally, the miRNA expression was confirmed by miRNA sequencing. RESULTS: Compared with the control group, 6 members of circRNAs were up-regulated, and 4 were down-regulated in the ALD model. GO enrichment analyses revealed these circRNAs were predominantly enriched in the endoplasmic reticulum, arachidonic acid metabolism, and cytochrome P450 metabolism pathway. Among these circRNAs, the differential expression of 5 circRNAs was validated and consistent with qRT-PCR, and only the up-regulated mou_circ_1657 is included in the circBase. Further, the crosstalk analysis of circRNA-miRNA revealed 7 miRNAs were targeted by mou_circ_1657, of which miR-19-5b was the only miRNA that was down-regulated in the ALD mice according to the miRNA sequencing data, suggesting it needs further attention in ALD. CONCLUSIONS: This study demonstrates that a cluster of circRNAs is aberrantly expressed in the livers of ALD mice. mou_circ_1657/miR-19-5b may play a critical role in the development of ALD. Our study provides new insight into the future investigation and therapy on ALD.