非酒精性脂肪肝分子发病机制的研究进展

Effects of Liucha extract on liver lipid metabolism in rats with nonalcoholic fatty liver disease

AIM: To investigate the effect of Liucha extract on liver lipid metabolism in rats with nonalcoholic fatty liver disease.

METHODS: A rat model of nonalcoholic fatty liver disease was established by feeding rats a high-fat diet for 6 wk. The model rats were divided randomly into four groups: model group and low-, medium- and high-dosage treatment groups. The treatment groups were intragastrically given different doses of Liucha extract for 8 wk. A normal control group was also run. All rats were killed at week 8. Liver function parameters (ALT, AST) and the contents of fat (CHOL, TG) in liver homogenate were examined. Hepatic morphological changes were observed under a light microscope. The expression of PPARα and ACO mRNAs and PPARα protein was measured by RT-PCR and Western blot, respectively.

RESULTS: Compared with the model group, liver function was improved in the treatment groups. The levels of ALT and AST were significant lower in the low- and medium-dosage treatment groups than in the model group (29.83 mmol/L ± 2.78 mmol/L and 25.78 mmol/L ± 2.63 mmol/L vs 31.90 mmol/L ± 2.52 mmol/L; 110.53 mmol/L ± 12.33 mmol/L and 100.45 mmol/L ± 12.57 mmol/L vs 128.61 mmol/L ± 16.01 mmol/L; all P < 0.05 or 0.01). The contents of CHOL and TG in liver homogenate were significantly lower in the medium-dosage treatment group than in the model group (0.30 mmol/L ± 0.02 mmol/L vs 0.47 mmol/L ± 0.04 mmol/L, 0.75 mmol/L ± 0.06 mmol/L vs 0.85 mmol/L ± 0.04 mmol/L, both P < 0.01 or 0.05). Hepatic morphological changes were improved in the treatment groups, particularly prominent in the medium-dosage treatment group. Compared with the model group, the expression of PPARα and ACO mRNAs was up-regulated in the medium- and high-dosage treatment groups (both P < 0.01). In addition, Liucha extract up-regulated the expression of PPARα protein in a dosage-dependent manner.

CONCLUSION: Liucha extract could up-regulate the mRNA expression of PPARα and ACO, enhance the synthesis of PPARα protein, promote liver lipid oxidation, and improve liver function in rats with nonalcoholic fatty liver disease.

Significance of serum levels of tumor necrosis factor-alpha and interleukin-6 in patients with nonalcoholic fatty liver disease

AIM: To evaluate the significance of serum levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS: Fifty-seven NAFLD patients, including 21 patients with simple steatosis, 29 patients with nonalcoholic steatohepatitis (NASH) and 7 patients with cirrhosis, and 22 healthy control subjects were included in this study. Serum TNF-α and IL-6 levels were determined by enzyme-linked immunosorbent assay (ELISA). Body weight index, blood pressure, serum glucose, serum insulin and serum lipids were also measured to assess insulin resistance and metabolic syndrome complicated with NAFLD. The differences in serum levels of TNF-α and IL-6 between various groups were compared. The association of serum TNF-α and IL-6 levels with homeostasis model assessment of insulin resistance (HOMA-IR) and the risk of metabolic syndrome was analyzed.

RESULTS: The levels of serum TNF-α and IL-6 significantly increased in patients with simple steatosis, NASH and cirrhosis compared with normal subjects (all P < 0.05). The levels of serum TNF-α and IL-6 were significantly higher in NASH patients than in patients with simple steatosis or cirrhosis (both P < 0.05). A significant positive correlation was found between serum TNF-α and IL-6 levels and HOMA-IR (r = 608, 0.709, both P = 0.000). In NAFLD patients complicated with metabolic syndrome, serum TNF-α and IL-6 levels were significantly elevated compared with NAFLD patients without evidence of metabolic syndrome (P < 0.05). A significant correlation was also observed between serum TNF-α and IL-6 levels and the risk of metabolic syndrome (r = 0.409 and 0.552; P = 0.002 and 0.000, respectively).

CONCLUSION: Increased TNF-α and IL-6 production not only plays an important role in the development and progression of NAFLD but also contributes to the development of metabolic syndrome in NAFLD patients by inducing insulin resistance.

Research progress in liver targeted fatty acid bile acid conjugates

Fatty acid bile acid conjugates (FABACs) are synthetic lipid molecules designed to solubilize biliary cholesterol. FABACs were shown to delay, reduce, or prevent cholesterol crystallization in vitro and ex vivo in model bile solutions and in human bile. FABACs have also been shown to prevent the formation of cholesterol gallstones and to dissolve preexisting gallstones in experimental animal models. In addition to the beneficial effect on gallstone disease, FABACs have been demonstrated to be able to prevent diet-induced fatty liver, reduce atherosclerosis in C57Bl6 mice and increase faecal bile salt and neutral sterol secretion.