Rhein ameliorates fatty liver disease through negative energy balance, hepatic lipogenic regulation, and immunomodulation in diet-induced obese mice.

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, and inflammatory disorders. In this study, we tested the effect of rhein, a lipophilic anthraquinone derived from a traditional Chinese herbal medicine Rheum palmatum L., on NAFLD-associated hepatic steatosis, insulin resistance, and the T helper (Th)1/Th2 cytokine imbalance in high-fat diet-induced obese (DIO) mice. We found that oral administration of rhein for 40 days significantly increased energy expenditure, reduced body weight, particularly body fat content, improved insulin resistance, and lowered circulating cholesterol levels in DIO mice without affecting food intake. Rhein treatment also reduced liver triglyceride levels, reversed hepatic steatosis, and normalized alanine aminotransferase (ALT) levels in these mice. Gene analysis and Western blot showed that rhein markedly suppressed the expression of the lipogenic enzyme sterol regulatory element-binding protein-1c (SREBP-1c) and its target genes in the liver. Luciferase reporter assay revealed that rhein suppressed the transcriptional activity of SREBP-1c through its upstream regulator, liver X receptor (LXR). This suggests that rhein exerts its effects by targeting LXR, which is also supported by its inability to reduce body weight in LXR knockout mice. Moreover, multiplex ELISA displayed a downregulated Th1 response after rhein treatment. Rhein shifted the Th1/Th2 responses by inhibiting T-box expressed in T-cells (T-bet) expression and enhancing GATA-binding protein-3 (GATA-3) expression through increased signal transducer and activator of transcription 6 (STAT6) phosphorylation. These data indicate that rhein ameliorated NAFLD and associated disorders through LXR-mediated negative energy balance, metabolic regulatory pathways, and immunomodulatory activities involved in hepatic steatosis. The combined effects of rhein to target hepatic metabolic and immune pathways may be beneficial for complex metabolic diseases such as NAFLD.