GLP-1 analogue improves hepatic lipid accumulation by inducing autophagy via AMPK/mTOR pathway.
The incidence of nonalcoholic fatty liver disease (NAFLD) keeps rising year by year, and NAFLD is rapidly becoming the most common liver disease worldwide. Clinical studies have found that glucagon-like peptide-1 (GLP-1) analogue, liraglutide (LRG), cannot only reduce glucose levels, but also improve hepatic lipase, especially in patients also with type 2 diabetes mellitus (T2DM). In addition, enhancing autophagy decreases lipid accumulation in hepatocytes. The aim of the present study is to explore the effect of LRG on hepatocyte steatosis and the possible role of autophagy. We set up an obesity mouse model with a high-fat diet (HFD) and induced hepatocyte steatosis with free fatty acids (FFA) in human L-O2 cells. LRG and two inhibitors of autophagy, Chloroquine (CQ) and bafilomycin A1 (Baf), were added into each group, respectively. The lipid profiles and morphological modifications of each group were tested. Immunohistochemistry, immunofluorescence staining and transmission electron microscopy (TEM) were used to measure autophagy in this study. The autophagy protein expression of SQSTM1 (P62), and LC3B, along with the signaling pathway proteins of mTOR, phosphorylated mTOR (p-mTOR), AMPK, phosphorylated AMPK (p-AMPK) and Beclin1, were evaluated by western blot. Our results showed that LRG improved hepatocyte steatosis by inducing autophagy, and the AMPK/mTOR pathway is involved. These findings suggest an important mechanism for the positive effects of LRG on hepatic steatosis, and provide new evidence for clinical use of LRG in NAFLD.
He Q
，Sha S
，Sun L
，Zhang J
，Dong M
... -
《-》
Betulinic acid alleviates non-alcoholic fatty liver by inhibiting SREBP1 activity via the AMPK-mTOR-SREBP signaling pathway.
Non-alcoholic fatty liver disease (NAFLD) is emerging as the most common liver disease in industrialized countries. The discovery of food components that can ameliorate NAFLD is therefore of interest. Betulinic acid (BA) is a triterpenoid with many pharmacological activities, but the effect of BA on fatty liver is as yet unknown. To explore the possible anti-fatty liver effects and their underlying mechanisms, we used insulin-resistant HepG2 cells, primary rat hepatocytes and liver tissue from ICR mice fed a high-fat diet (HFD). Oil Red O staining revealed that BA significantly suppressed excessive triglyceride accumulation in HepG2 cells and in the livers of mice fed a HFD. Ca(+2)-calmodulin dependent protein kinase kinase (CAMKK) and AMP-activated protein kinase (AMPK) were both activated by BA treatment. In contrast, the protein levels of sterol regulatory element-binding protein 1 (SREBP1), mammalian target of rapamycin (mTOR) and S6 kinase (S6K) were all reduced when hepatocytes were treated with BA for up to 24h. We found that BA activates AMPK via phosphorylation, suppresses SREBP1 mRNA expression, nuclear translocation and repressed SREBP1 target gene expression in HepG2 cells and primary hepatocytes, leading to reduced lipogenesis and lipid accumulation. These effects were completely abolished in the presence of STO-609 (a CAMKK inhibitor) or compound C (an AMPK inhibitor), indicating that the BA-induced reduction in hepatic steatosis was mediated via the CAMKK-AMPK-SREBP1 signaling pathway. Taken together, our results suggest that BA effectively ameliorates intracellular lipid accumulation in liver cells and thus is a potential therapeutic agent for the prevention of fatty liver disease.
Quan HY
，Kim DY
，Kim SJ
，Jo HK
，Kim GW
，Chung SH
... -
《-》
Kangtaizhi Granule Alleviated Nonalcoholic Fatty Liver Disease in High-Fat Diet-Fed Rats and HepG2 Cells via AMPK/mTOR Signaling Pathway.
Kangtaizhi granule (KTZG) is a Chinese medicine compound prescription and has been proven to be effective in nonalcoholic fatty liver disease (NAFLD) treatment clinically. However, the underlying mechanisms under this efficacy are rather elusive. In the present study, network pharmacology and HPLC analysis were performed to identify the chemicals of KTZG and related target pathways for NAFLD treatment. Network pharmacology screened 42 compounds and 79 related targets related to NAFLD; HPLC analysis also confirmed six compounds in KTZG. Further experiments were also performed. In an in vivo study, SD rats were randomly divided into five groups: control (rats fed with normal diet), NAFLD (rats fed with high-fat diet), and KTZG 0.75, 1.5, and 3 groups (NAFLD rats treated with KTZG 0.75, 1.5, and 3 g/kg, respectively). Serum lipids were biochemically determined; hepatic steatosis and lipid accumulation were evaluated with HE and oil red O staining. In an in vitro study, HepG2 cells were incubated with 1 mM FFA to induce lipid accumulation with or without KTZG treatment. MTT assay, intracellular TG level, oil red O staining, and glucose uptake in cells were detected. Western blotting and immunohistochemical and immunofluorescence staining were also performed to determine the expression of lipid-related genes PPAR-γ, SREBP-1, p-AKT, FAS, and SIRT1 and genes in the AMPK/mTOR signaling pathway. In high-fat diet-fed rats, KTZG treatment significantly improved liver organ index and serum lipid contents of TG, TC, LDL-C, HDL-C, ALT, and AST significantly; HE and oil red O staining also showed that KTZG alleviated hepatic steatosis and liver lipid accumulation. In FFA-treated HepG2 cells, KTZG treatment decreased the intracellular TG levels, lipid accumulation, and attenuated glucose uptake significantly. More importantly, lipid-related genes PPAR-γ, SREBP-1, p-AKT, FAS, and SIRT1 expressions were ameliorated with KTZG treatment in high-fat diet-fed rats and FFA-induced HepG2 cells. The p-AMPK and p-mTOR expressions in the AMPK/mTOR signaling pathway were also modified with KTZG treatment in high-fat diet-fed rats and HepG2 cells. These results indicated that KTZG effectively ameliorated lipid accumulation and hepatic steatosis to prevent NAFLD in high-fat diet-fed rats and FFA-induced HepG2 cells, and this effect was associated with the AMPK/mTOR signaling pathway. Our results suggested that KTZG might be a potential therapeutic agent for the prevention of NAFLD.
Zhang J
，Du H
，Shen M
，Zhao Z
，Ye X
... -
《-》
ResearchGate
(全网免费下载)
钛学术
(全网免费下载)
