Background: Non-alcoholic fatty liver disease (NAFLD) has become a major cause of chronic liver disease. The Chinese herbal medicine (CHM) Dachaihu decoction (DCHD) has been proved to treat NAFLD with good efficacy in previous studies. Based on the TCM principle of formula formation, we divided DCHD into soothing liver part, invigorating spleen part, and dredging intestine part. Marshall officially proposed the concept of "intestinal-hepatic axis", which systematically explains the interactions between the intestine and liver. We hypothesized that the effect of CHM on NAFLD is achieved by regulating the liver and intestine. Thus, we aimed to investigate the possible effect of a CHM formula on NAFLD in a rat model.
Aim: To investigate the effects of a CHM formula (a decoction of Chinese thorowax root, scutellaria root, and white peony root) on NAFLD and its regulatory effect on the "intestinal-liver" axis.
Methods: Sixty rats were randomly divided into control, model, pioglitazone hydrochloride (PH), and CHM (a decoction of Chinese thorowax root, scutellaria root, and white peony root) groups. An NAFLD rat model was established using a high-fat high-fructose diet for 16 wk. From the 13th week, rats were administered with PH or a decoction of Chinese thorowax, scutellaria, and white peony root (CHM group) for 4 wk. Rats in the control group and model group were administered with an equal volume of distilled water. At the end of the study, blood was collected via the abdominal aorta. Liver tissues were harvested and any morphological changes were observed by hematoxylin-eosin (HE) staining, Oil red O staining, and Masson staining. In addition, blood lipids, liver function markers, and triglyceride (TG) in liver tissues were analyzed. The levels of transforming growth factor-β1 (TGF-β1), tumor necrosis factor-α (TNF-α), Toll-like receptor-4 (TLR4), and nuclear factor-kappa B (NF-кB) in liver tissues and secreted immunoglobulin A (sIgA) in intestinal tissues were analyzed by ELISA, and protein and mRNA expression of occludin and zonula occludens-1 (ZO-1) in the intestine were measured using Western blot and reverse transcription-quantitative polymerase chain reaction, respectively. The endotoxin level in plasma was detected by endpoint chromogenic assay.
Results: Compared to the normal control group, the liver coefficient, serum TG, total cholesterol (TC), low density lipoprotein (LDL), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), blood glucose, plasma endotoxin, and the levels of TG, TNF-α, TGF-β, NF-kB, and TLR4 in liver tissues increased significantly in the model group, while serum high density lipoprotein (HDL), intestinal sIgA, and protein and mRNA expression of occludin and ZO-1 decreased significantly in the model group (P < 0.01). PH and CHM attenuated the elevated liver coefficient, serum TG, TC, LDL, AST, and ALT, blood glucose, plasma endotoxin, and the levels of TG, TNF-α, TGF-β, NF-kB, and TLR4 in liver tissues and increased serum HDL levels compared to the model group (P < 0.01). Intestinal sIgA and the protein and mRNA expression of intestinal occludin and ZO-1 were significantly increased in the PH group compared to the model and CHM groups (P < 0.01).
Conclusion: The decoction of Chinese thorowax root, scutellaria root, and white peony root is beneficial in regulating lipid metabolism and liver function, which indicates that it has a good effect on the liver. To a certain extent, this CHM formula can affect both the liver and intestine, while its effect on the liver is superior to that on the intestine.
Keywords: Chinese herbal medicine; Intestinal-hepatic axis; Liver function; Non-alcoholic fatty liver disease.