Purpose: Oxidative stress plays an important role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). TRPM2 ion channel functions as a molecular sensor for oxidative stress. The aim of this study was to examine the protective effects of Salidroside, a powerful antioxidative plant, on TRPM2 in an established in vitro model of NAFLD. Methods: NAFLD model was established by palmitic acid (PA) in hepatic L02 cell lines and was added to the media at a final concentration of 400 mu M. Cells were used as normal group, PA group and PA receiving varied concentrations of Salidroside (75 mu g/mL, 150 mu g/ mL, 300 mu g/mL). After treating 24 hrs, MTT assay was used to detect cell viability, and ALT level was measured using an appropriate kit assay. Intracellular lipid accumulation was observed by Oil red O staining. Cytosolic Ca2+ concentrations were evaluated by flow cytometer with Fluo-3/AM. Quantitative RT-PCR was used to measure the mRNA expression of TRPM2, IL-1 beta and IL-6, and the protein expressions of TRPM2, p-CaMKII and autophagy (LC3B, p62) were determined using Western blot. Results: Treatment with Salidroside effectively restored liver injury and alleviated lipid droplet deposition in a dose-dependent manner, which was associated with inhibition of TRPM2/Ca2+/CaMKII pathway. Additionally, autophagic clearance was enhanced by intervention with Salidroside in a dose-dependent manner. Further investigation indicated that Salidroside down-regulated the mRNA expression of IL-1 beta and IL-6-pro-inflammatory cytokines. Conclusion: These results suggest that Salidroside could alleviate inflammatory injury and steatosis via autophagy activation mediated by downregulation of the TRPM2/Ca2+/CaMKII pathway. Targeting the TRPM2 ion channel is a novel treatment strategy for oxidative stress-induced liver in NAFLD.

Genipin is the major active component of Gardeniae fructus and has been shown to ameliorate diabetes and insulin resistance in rat models. In this study, we first investigated the effect of genipin on obesity and the related lipid metabolism mechanisms in diet-induced obese rats. Our results showed that genipin reduced body weight, food intake, and visceral fat mass; ameliorated dyslipidemia, glucose intolerance, insulin intolerance, adipocyte hypertrophy, and hepatic steatosis; and reduced serum tumor necrosis factor- level in diet-induced obese rats. Quantitative real-time reverse-transcription polymerase chain reaction results further illustrated that genipin promoted lipolysis and -oxidation of fatty acid by upregulating gene expressions of hormone-sensitive lipase and adipose triglyceride lipase in white adipose tissue (WAT) and peroxisome proliferator-activated receptor- and carnitine palmitoyltransferase 1 in hepatic tissue. Moreover, genipin promoted browning of WAT by upregulating the mRNA and protein levels of uncoupling protein 1 and PRD1-BF1-RIZ1 homologous domain containing 16 in WAT. Additionally, genipin inhibited gene expressions of activin receptor-like kinase 7, tumor necrosis factor-, and interlukin-6 in WAT. These results indicated that genipin had a potential therapeutic role in obesity, in which regulation of lipid mobilization and browning of WAT were involved.

Nonalcoholic steatohepatitis (NASH) is characterized by fat accumulation in the hepatocyte, inflammation, liver cell injury, and varying degrees of fibrosis, and can lead to oxidative stress in liver. Here, we investigated whether Salidroside, a natural phenolic antioxidant product, can protect rat from liver injury during NASH.

Liver steatosis is characterized by lipid dysregulation and fat accumulation in the liver and can lead to oxidative stress in liver. Since proanthocyanidins are present in plant-based foods and have powerful antioxidant properties, we investigated whether proanthocyanidins can prevent oxidative stress and subsequent liver injury. Carbon tetrachloride (CCl4) treatment can cause steatosis in rats that models both alcoholic and non-alcoholic fatty liver disease in humans. We pre-treated rats by oral administration of proanthocyanidins extracted from grape seeds 7 days prior to intragastrically administering CCl4. Proanthocyanidin treatment continued for an additional 2 weeks, after which time liver and serum were harvested, and mediators of liver injury, oxidative stress, and histological features were evaluated. CCl4-treated rats exhibited significant increases in the following parameters as compared to non-treated rats: fat droplets in the liver, liver injury (ALT, AST), and DNA damage (8-OHdG). Additionally, CCl4 treatment decreased antioxidant enzymes SOD, GSH, GPX, and CAT in the liver due to their rapid depletion after battling against oxidative stress. Compared to CCl4-treated rats, treatment with proanthocyanidins effectively suppressed lipid accumulation, liver injury, DNA damage, as well as restored antioxidant enzyme levels. Further investigation revealed that proanthocyanidins treatment also inhibited expression of CYP2E1 in liver, which prevented the initial step of generating free radicals from CCl4. The data presented here show that treatment with orally administered proanthocyanidins prevented liver injury in the CCl4-induced steatosis model, likely through exerting antioxidant actions to suppress oxidative stress and inhibiting the free radical-generating CYP2E1 enzyme.