Green tea extract inhibits early oncogenic responses in mice with nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis (NASH) increases hepatocellular carcinoma (HCC) risk. We hypothesized that the hepatoprotective anti-inflammatory benefits of catechin-rich green tea extract (GTE) would protect against HCC progression by inhibiting NASH-associated liver injury and pro-oncogenic responses. We used an HCC model in high-fat (HF)-fed mice that mimics early oncogenic events during NASH without inducing tumorigenesis and premature mortality. Male C57BL/6J mice (4-weeks old) were fed a HF diet containing GTE at 0% or 2%. Mice were administered saline or diethylnitrosamine (DEN; 60 mg kg-1, i.p.) at 5-weeks and 7-weeks of age. NASH, inflammation, fibrosis, and oncogenic responses were assessed at 25-weeks of age. Saline-treated mice showed prominent histopathological signs of steatosis and hepatocellular ballooning. Although DEN did not impact adiposity, steatosis, ballooning and hepatic lipid accumulation, these parameters were attenuated by GTE regardless of DEN. Hepatic lipid peroxidation and fibrosis that were increased by DEN were attenuated by GTE. Hepatic TLR4, MCP1 and TNFα mRNA levels were unaffected by DEN, whereas iNOS was increased by DEN. These transcripts were lowered by GTE. GTE attenuated the frequency of PCNA+ hepatocytes and mRNA expression of cyclin D1, MIB1 and Ki-67 that were otherwise increased by DEN. GTE increase APAF1 mRNA that was otherwise lowered by DEN. Relative to saline-treated mice, DEN increased mRNA levels of oncostatin M, gp130, c-Fos, c-Myc and survivin; each was lowered by GTE in DEN-treated mice. These findings indicate that GTE may protect against hepatic oncogenesis by limiting early steps in the carcinogenic cascade related to NASH-associated HCC.

Green tea extract protects against hepatic NFκB activation along the gut-liver axis in diet-induced obese mice with nonalcoholic steatohepatitis by reducing endotoxin and TLR4/MyD88 signaling.

Green tea extract (GTE) reduces NFκB-mediated inflammation during nonalcoholic steatohepatitis (NASH). We hypothesized that its anti-inflammatory activities would be mediated in a Toll-like receptor 4 (TLR4)-dependent manner. Wild-type (WT) and loss-of-function TLR4-mutant (TLR4m) mice were fed a high-fat diet containing GTE at 0 or 2% for 8 weeks before assessing NASH, NFκB-mediated inflammation, TLR4 and its adaptor proteins MyD88 and TRIF, circulating endotoxin, and intestinal tight junction protein mRNA expression. TLR4m mice had lower (P<.05) body mass compared with WT mice but similar adiposity, whereas body mass and adiposity were lowered by GTE regardless of genotype. Liver steatosis, serum alanine aminotransferase, and hepatic lipid peroxidation were also lowered by GTE in WT mice, and were similarly lowered in TLR4m mice regardless of GTE. Phosphorylation of the NFκB p65 subunit and pro-inflammatory genes (TNFα, iNOS, MCP-1, MPO) were lowered by GTE in WT mice, and did not differ from the lowered levels in TLR4m mice regardless of GTE. TLR4m mice had lower TLR4 mRNA, which was also lowered by GTE in both genotypes. TRIF expression was unaffected by genotype and GTE, whereas MyD88 was lower in mice fed GTE regardless of genotype. Serum endotoxin was similarly lowered by GTE regardless of genotype. Tight junction protein mRNA levels were unaffected by genotype. However, GTE similarly increased claudin-1 mRNA in the duodenum and jejunum and mRNA levels of occludin and zonula occluden-1 in the jejunum and ileum. Thus, GTE protects against inflammation during NASH, likely by limiting gut-derived endotoxin translocation and TLR4/MyD88/NFκB activation.

Green tea extract treatment reduces NFκB activation in mice with diet-induced nonalcoholic steatohepatitis by lowering TNFR1 and TLR4 expression and ligand availability.

NFκB-mediated inflammation contributes to liver injury during nonalcoholic steatohepatitis (NASH). We hypothesized that antiinflammatory activities of green tea extract (GTE) during NASH would lower tumor necrosis factor receptor-1 (TNFR1)- and Toll-like receptor-4 (TLR4)-mediated NFκB activation. Male C57BL6/J mice (6 weeks old) were fed a low-fat (LF) or high-fat (HF) diet for 12 weeks to induce NASH. They were then randomized to continue on these diets supplemented with 0 or 2% GTE (n=10/group) for an additional 8 weeks prior to evaluating NASH, NFκB inflammation and TNFR1 and TLR4 receptor complexes and their respective ligands, TNFα and endotoxin. HF feeding increased (P<.05) serum alanine aminotransferase (ALT) activity and histological evidence of NASH compared with LF controls. HF-mediated increases in NFκB p65 phosphorylation were also accompanied by increased serum TNFα and endotoxin concentrations, mRNA expression of hepatic TNFR1 and TLR4 and MyD88 protein levels. GTE in LF mice had no effect (P>.05) on liver histology or inflammatory responses. However, GTE in HF mice decreased biochemical and histological parameters of NASH and lowered hepatic p65 phosphorylation in association with decreased serum TNFα, mRNA expression of TNFR1 and TLR4 and MyD88 protein. GTE in HF-fed mice also lowered serum endotoxin and up-regulated mRNA expression of duodenal occludin and zonula occluden-1 and ileal occludin and claudin-1 that were otherwise lowered in expression by HF feeding. These data suggest that dietary GTE treatment reduces hepatic inflammation in NASH by decreasing proinflammatory signaling through TNFR1 and TLR4 that otherwise increases NFκB activation and liver injury.