BACKGROUND:In recent years,with the improvement of living standards,non-alcoholic fatty liver disease has a gradually increasing trend.miRNA-122 is one of the most abundant microRNAs in the liver,which plays an important role in maintaining the environmental stability and differentiation of the liver.Exercise training is a non-drug treatment for non-alcoholic fatty liver disease,which may improve liver lipid metabolism by regulating the expression of miRNA-122. OBJECTIVE:To review the effects of miRNA-122 on the pathological factors related to non-alcoholic fatty liver disease as well as the effects of exercise on the expression of miRNA-122 and the occurrence and development of nonalcoholic fatty liver disease. METHODS:The first author searched the databases of CNKI,WanFang,VIP,PubMed,Geenmedical,EBSCO,Medline,Web of Science,and Elsevier using"non-alcoholic fatty liver disease,microRNA,microRNA-122,lipid metabolism,inflammatory response,insulin resistance,exercise,physical exercise,exercise training"as the English and Chinese search terms for all relevant literature published before June 5,2022.All included documents were screened,summarized,and analyzed.Finally,68 documents were included for review. RESULTS AND CONCLUSION:Compared with the healthy control group,the expression of circulating miRNA-122 is increased in patients with non-alcoholic fatty liver disease.The level of miRNA-122 may show different expression levels at different stages of non-alcoholic fatty liver disease.miRNA-122 can regulate the expression of downstream-related proteins,influence lipid metabolism,inflammatory response,insulin resistance and other pathogenic factors in non-alcoholic fatty liver disease by targeting base complementary pairing sites on mRNA or directly acting as physiological ligands of some RNA receptors.Different exercise modes can improve non-alcoholic fatty liver disease.Therefore,patients with non-alcoholic fatty liver disease need to complete at least 120 minutes of moderate-intensity exercise every week to have a positive effect.For patients who can tolerate various exercises,priority should be given to the combination of aerobic and resistance exercises 4-5 times a week.The exercise intensity should be 50%-70%of the maximum heart rate and the exercise should last for>3 months.For patients with poor tolerance,resistance exercise may be more feasible than aerobic exercise.In addition,patients with non-alcoholic fatty liver disease can also choose proper exercise modes according to their own disease conditions(such as liver enzymes and lipid levels).Exercise can be used as a feasible strategy to prevent non-alcoholic fatty liver disease,reduce liver steatosis,and alleviate liver inflammatory response and insulin resistance.Exercise training can regulate the expression of miRNA-122,but in patients with non-alcoholic fatty liver disease,the effect of exercise on miRNA-122 and its related signal pathways remains to be studied.