Dijincao extract improves non-alcoholic fatty liver disease through miR-106-5p/TLR4 signaling pathway
Non alcoholic steatohepatitis (NASH) is a pathological change in the development of non-alcoholic fatty liver disease (NAFLD), characterized by inflammation mediated by hepatic lipid metabolism disorders, endoplasmic reticulum stress (ER), mitochondrial dysfunction, and fibrosis. It is considered a key link in the development of clinical lesions and is closely related to the development of cirrhosis and liver cancer. The dysregulation of the gut liver axis in NASH progression plays an important role in mediating inflammatory responses. Damage to the intestinal barrier causes metabolic endotoxins to be transported to the liver through the “gut liver axis”, leading to liver inflammation. Among them, miRNA plays an important regulatory role in the occurrence and development of liver inflammation. Non coding microRNAs (miRNAs) are a class of nucleotide sequences that do not encode proteins, but can inhibit gene expression by targeting the 3’UTR of the target gene mRNA. MiRNAs are involved in almost all physiological and pathological processes. miRNAs can activate the MAPK signaling pathway by targeting inflammation related genes, such as miR-106 low expression, mediating oxidative stress damage and inflammatory infiltration in the liver of pregnant hypertensive mice. Through luciferase reporter gene analysis, it was found that miR-106a regulates the target specificity of Th17 transcription factor Ror and activated T cell (Nfat) nuclear factor 5. These results suggest that low expression of miR-106 can mediate the expression of related inflammatory factors and generate inflammatory responses.
Euphorbia humifusa Willd. is a plant of the Euphorbiaceae family and Euphorbiaceae genus. Commonly used for treating bacterial dysentery, gastroenteritis, hemoptysis, rectal bleeding and other diseases. Modern pharmacology has shown that Dijincao contains various active ingredients, such as polyphenols, flavonoids, alkaloids, and triterpenoids, which have anti-inflammatory, antioxidant, lipid-lowering, hypoglycemic, and bacteriostatic effects. Therefore, in this experiment, a short-term high-fat diet (HFD) combined with dextran sulfate sodium (DSS) feeding was used at the animal level to establish a NASH mouse model (HFD+DSS). DSS is a type of animal model that can damage the intestinal barrier in mice and is commonly used to induce colitis. Based on this model, the intervention of Dijincao extract in NASH and its possible mechanisms were studied, providing new ideas for the prevention and treatment of NASH.

 

The high-fat diet induced NAFLD animal model has been widely used, but simple dietary induction takes several months to show obvious liver inflammation phenotype, and the longer modeling period has many limiting factors for drug screening. Adding dextran sulfate sodium (DSS) to a high-fat diet can exacerbate intestinal inflammation in a high-fat diet induced NASH mouse model. Kwon et al. found that mice treated with DSS exhibited decreased expression of intestinal barrier function related proteins and increased plasma LPS levels, indicating intestinal barrier dysfunction induced by DSS. At the same time, these mice also exhibited liver fat accumulation and inflammatory phenotype, promoting the occurrence and development of NASH. The preliminary experiments of the research group also found that feeding mice with HFD and DSS can induce lipid deposition and intestinal barrier damage caused by high-fat diet, which can develop into non-alcoholic steatohepatitis in a short period of time. In summary, this method can fully establish an in vivo model of NASH in a short period of time, which is suitable for drug screening and mechanism research.
There are research reports that in a mouse model of acute lung injury (ALI), the expression of miR-106a in lung tissue of macrophages stimulated by LPS is significantly reduced. MiR-106a can inhibit NF – κ B activation and the production of downstream inflammatory factors by targeting TLR4 expression. High glucose (25mmol/L) can induce an increase in HMGB1 expression and a decrease in miR-106 expression in human umbilical vein endothelial cells (HUVECs), mediating HUVEC apoptosis and the expression of inflammatory factors. In summary, these data collectively indicate that reduced miR-106 expression can activate the inflammatory response signaling pathway. Our research results also demonstrate that in the NASH mouse model, miR-106a expression is low and TLR4 expression is high in liver tissue, thereby mediating the occurrence and development of NASH. After administering the extract of Dijincao, the levels of ALT and TG decreased; The mRNA level of TNF – α in liver tissue decreases, and the degree of pathological damage is reduced. At the same time, it was found that miR-106-5p expression was low in the liver tissue of the model group, while miR-106-5p targeted TLR4 expression was upregulated. Subsequently, it was observed that TNF – α, IL-1 β, and IL-6 downstream of the TLR4 signaling pathway were significantly increased in liver tissue. Drug intervention can lead to an increase in miR-106-5p expression and inhibit the TLR4 signaling pathway.
In summary, the extract of Dijincao can improve non-alcoholic fatty liver disease induced by high-fat and glucan sodium sulfate diets. Its mechanism of action in improving non-alcoholic fatty liver disease may be through regulating the expression of miR-106-5p to inhibit the inflammatory response mediated by the targeted TLR4 signaling pathway, thereby improving inflammatory liver injury and providing experimental evidence for the development of NASH therapeutic drugs.