Objective  To explore alleviating effect and mechanism of natto combined with red yeast rice on alcoholic liver injury (ALD) in rats.

  Methods  Totally 48 male Wistar rats were randomly divided into four groups: a control group with normal saline; a model group gavaged with a liquor containing 56% alcohol at an increment dosage of 6, 8, and 10 ml/kg·bw·d continuously for 3 weeks and at a dosage of 11 ml/kg·bw·d for 7 weeks; a natto plus red yeast rice group gavaged with nattokinase at dosage of 595.59 FU/kg·bw·d and lovastatin at dosage of 4.46 mg/kg·bw·d one hour before the liquor treatment the same as the model group; and a diammonium glycyrrhizinate group gavaged with diammonium glycyrrhizinate at dosage of 200 mg/kg·bw·d one hour before the liquor treatment the same as the model. Structure of liver and small intestine tissue were observed with hematoxylin and eosin (HE) stain and transmission electron microscopy. Serum alanine aminotransferase (ALT) , aspartate aminotransferase (AST), glutamyl transpeptidase (GGT), and alkaline phosphatase (ALP) were detected with automatic biochemistry analyzer; serum endotoxin was determined with enzyme-linked immunosorbent assay (ELISA); protein expressions of cluster of differentiation-14 (CD14), Toll-like receptor 4 (TLR4) and tumor necrosis factor α (TNF-α) in liver tissues were detected with Western blot.

  Results  Compared with those of the control group, obvious pathological changes in liver and small intestine tissues of the model group were observed and the pathological changes were significantly alleviated in the natto plus red yeast rice group and diammonium glycyrrhizinate group in comparison with those of the model group. Compared with those of the control group, the serum ALT (60.50 ± 15.40 U/L), AST (152.00 ± 33.11 U/L) , GGT (4.18 ± 0.75 U/L) and ALP (157.30 ± 46.64 U/L) of the model group increased significantly (P < 0.05 for all); while, compared with those of the model group, the AST (130.16 ± 27.66 U/L), GGT (3.00 ± 1.09 U/L) and ALP (137.00 ± 24.77 U/L) of the natto plus red yeast rice group decreased significantly (all P < 0.05). Compared with those of the control group, serum endotoxin and expressions of CD14, TLR4 and TNF-α in liver tissues of the model group increased significantly (all P < 0.05); whereas, serum endotoxin and expressions of CD14, TLR4 and TNF-α in liver tissues of the natto plus red yeast rice group decreased significantly in comparison with those of the model group and the diammonium glycyrrhizinate group.

  Conclusion  Natto combined with red yeast rice could alleviate alcoholic liver injury by down-regulating serum endotoxin, expressions of CD14 and TLR4 protein in liver tissue and inhibiting the release of downstream TNF-α in rats.