Alisol B regulates AMPK/mTOR/SREBPs via directly targeting VDAC1 to alleviate hyperlipidemia.

BACKGROUND: The occurrence of hyperlipidemia is significantly influenced by lipid synthesis, which is regulated by sterol regulatory element binding proteins (SREBPs), thus the development of drugs that inhibit lipid synthesis has become a popular treatment strategy for hyperlipidemia. Alisol B (ALB), a triterpenoid compound extracted from Alisma, has been reported to ameliorate no-nalcoholic steatohepatitis (NASH) and slow obesity. However, the effect of ALB on hyperlipidemia and mechanism are unclear. PURPOSE: To examine the therapeutic impact of ALB on hyperlipidemia whether it inhibits SREBPs to reduce lipid synthesis. STUDY DESIGN: HepG2, HL7702 cells, and C57BL/6J mice were used to explore the effect of ALB on hyperlipidemia and the molecular mechanism in vivo and in vitro. METHODS: Hyperlipidemia models were established using western diet (WD)-fed mice in vivo and oleic acid (OA)-induced hepatocytes in vitro. Western blot, real-time PCR and other biological methods verified that ALB regulated AMPK/mTOR/SREBPs to inhibit lipid synthesis. Cellular thermal shift assay (CETSA), molecular dynamics (MD), and ultrafiltration-LC/MS analysis were used to evaluate the binding of ALB to voltage-dependent anion channel protein-1 (VDAC1). RESULTS: ALB decreased TC, TG, LDL-c, and increased HDL-c in blood, thereby ameliorating liver damage. Gene set enrichment analysis (GSEA) indicated that ALB inhibited the biosynthesis of cholesterol and fatty acids. Consistently, ALB inhibited the protein expression of n-SREBPs and downstream genes. Mechanistically, the impact of ALB on SREBPs was dependent on the regulation of AMPK/mTOR, thereby impeding the transportation of SREBPs from endoplasmic reticulum (ER) to golgi apparatus (GA). Further investigations indicated that the activation of AMPK by ALB was independent on classical upstream CAMKK2 and LKB1. Instead, ALB resulted in a decrease in ATP levels and an increase in the ratios of ADP/ATP and AMP/ATP. CETSA, MD, and ultrafiltration-LC/MS analysis indicated that ALB interacted with VDAC1. Molecular docking revealed that ALB directly bound to VDAC1 by forming hydrogen bonds at the amino acid sites S196 and H184 in the ATP-binding region. Importantly, the thermal stabilization of ALB on VDAC1 was compromised when VDAC1 was mutated at S196 and H184, suggesting that these amino acids played a crucial role in the interaction. CONCLUSION: Our findings reveal that VDAC1 serves as the target of ALB, leading to the inhibition of lipid synthesis, presents potential target and candidate drugs for hyperlipidemia.

[Zexie Decoction regulates Akt/TFEB signaling pathway to promote lipophagy in hepatocytes].

Taking lipophagy as the breakthrough point, we explored the mechanism of Zexie Decoction(ZXD) in improving lipid metabolism in the hepatocyte model induced by palmitic acid(PA) and in the animal model induced by high-fat diet(HFD) on the basis of protein kinase B(Akt)/transcription factor EB(TFEB) signaling pathway. Co-localization was carried out for the microtubule-associated protein light chain 3(LC3) plasmid labeled with green fluorescent protein(GFP) and lipid droplets(LDs), and immunofluorescence co-localization for liver LC3 of HFD mice and perilipin 2(PLIN2). The results showed that ZXD up-regulated the expression of LC3, reduced lipid accumulation in hepatocytes, and increased the co-localization of LC3 and LDs, thereby activating lipo-phagy. Western blot results confirmed that ZXD increased autophagy-related protein LC3Ⅱ/LC3Ⅰ transformation ratio and lysosome-associated membrane protein 2(LAMP2) in vivo and in vitro and promoted the degradation of sequestosome-1(SQSTM1/p62)(P<0.05). The results above jointly explained that ZXD regulated lipophagy. Furthermore, ZXD activated TFEB expression(P<0.05) and reversed the PA-and HFD-induced decrease of TFEB nuclear localization in hepatocytes(P<0.05). Meanwhile, ZXD activated liver TFEB to up-regulate the expression of the targets Lamp2, Lc3 B, Bcl2, and Atg5(P<0.05). Additionally, ZXD down-regulated the protein level of p-Akt upstream of TFEB in vivo and in vitro. In conclusion, ZXD may promote lipophagy by regulating the Akt/TFEB pathway.

Dehydroabietic acid improves nonalcoholic fatty liver disease through activating the Keap1/Nrf2-ARE signaling pathway to reduce ferroptosis.

The accumulation of iron-dependent lipid peroxides is one of the important causes of NAFLD. The purpose of this study is to explore the effect of dehydroabietic acid (DA) on ferroptosis in nonalcoholic fatty liver disease (NAFLD) mice and its possible mechanisms. DA improved NAFLD and reduced triglycerides (TG), total cholesterol (TC), and lipid peroxidation level and inhibited ferroptosis in the liver of HFD-induced mice. DA binds with Keap1 to form 3 stable hydrogen bonds at VAL512 and LEU557 and increased nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elemen (ARE) luciferase activity. DA promoted the expression downstream of Nrf2 such as heme oxygenase-1 (HO-1), glutathione (GSH) and its peroxidase 4 (GPX4), so as to eliminate the accumulation of reactive oxygen species (ROS) and reduce lipid peroxides malondialdehyde (MDA) in the liver. DA inhibited ferroptosis and increased the expression of key genes such as ferroptosis suppressor protein 1 (FSP1) in vitro and vivo. In all, DA may bind with Keap1, activate Nrf2-ARE, induce its target gene expression, inhibit ROS accumulation and lipid peroxidation, and reduce HFD-induced NAFLD.