Effects of theaflavin-3, 3'-digallate on high-fat diet-induced liver injury in mice and its mechanism

Abstract

Objective To investigate the protective effects of dietary intervention with theaflavin-3, 3'-digallate (TFDG) on liver injury induced by high-fat diet (HFD) in mice and its underlying mechanism. Methods Forty C57BL/6 mice were randomly and equally divided into normal control (NC), model control (MC) and TFDG administration (TF5 and TF10) groups. The mice of the NC group were fed with normal diet, and those of the other 3 groups were given HFD. Then the TF5 and TF10 groups were intragastrically given 5 mg/kg and 10 mg/kg TFDG respectively, while the NC and MC groups were treated with normal saline. After 12 weeks of intervention, the liver index, serum ALT and AST levels were detected, and the pathological changes of liver tissues were observed in the mice. The contents of inflammatory factors and the expression levels of related proteins in liver tissue were determined by ELISA and Western blotting respectively, and the mRNA level of miR-233 was measured by qRT-PCR. Results HFD significantly increased the liver index as well as serum ALT and AST levels, while these changes were effectively reversed by TFDG administration (P < 0.05). Pathological observation displayed that TFDG intervention reduced the formation of lipid droplets in liver tissue, and lipid content detection also suggested that TFDG remarkably declined the levels of triglyceride (TG) and total cholesterol (TC) in liver tissue (P < 0.05). ELISA indicated that the levels of IL-1β, IL-6 and TNF-α were elevated notably in the liver of HFD-fed mice, and Western blotting confirmed higher protein levels of NLRP3, caspase-1 and IL-1β, whereas TFDG inhibited the inflammatory response of liver (P < 0.05) and the activation of NLRP3/IL-1β pathway (P < 0.05). In addition, TFDG intervention greatly up-regulated the expression of miR-223 in the hepatocytes under high-fat condition. After oligonucleotide inhibitor blocked the effect of TFDG on miR-223 expression, its inhibitory effect on inflammatory response was weakened as well (P < 0.05). Conclusion TFDG can effectively alleviate liver injury and inflammatory response induced by HFD, which may be through up-regulation of miR-223 to inhibiting NLRP3 pathway.

Keywords

• theaflavin
• non-alcoholic fatty liver disease
• inflammatory response
• microrna