Liver function enzymes are important markers of the severity of many liver diseases, especially aspartate aminotransferase (AST) and alanine aminotransferase (ALT)(13). The study by Helene Gellert-Kristensen et al. found that the concentration of ALT has an important correlation with the risk of fatty liver, cirrhosis and HCC(14). And ALT is an independent related factor of metabolic syndrome, obesity, diabetes and other diseases(15, 16). Alcohol intake is an important factor leading to fatty liver and one of the important reasons leading to elevated ALT. Moderate alcohol consumption does not cause a significant increase in ALT, but long-term alcohol intake can cause an increase in ALT and liver changes(17–19). NAFLD is closely related to ALT activity and is a common cause of unexplained ALT elevation(20, 21). Unexplained elevated ALT should consider the possibility of NAFLD(16). This is also consistent with our experimental results, ALT is one of the most important factors related to fatty liver.
Studies by Muhammad et al. have shown that creatinine is significantly elevated in patients with fatty liver, which is obviously correlated with fatty liver(22). Creatinine is an important indicator of model for end-stage liver disease (MELD) score, which measures liver function and predicts survival in patients with liver disease(23–26).
NAFLD is closely linked with hepatic insulin resistance(27, 28). It is the liver manifestation of metabolic syndrome, and increased glucose is one of the important manifestations(29). Insulin resistance is a key pathogenic factor of metabolic syndrome and the most common risk factor for NAFLD(30–32). In patients with insulin resistance, insulin cannot inhibit liver glucose production, but it continues to stimulate adipogenesis, leading to hyperglycemia, hyperlipidemia, liver steatosis and type 2 diabetes(33, 34). However, in our study, insulin content was not an important correlation factor of fatty liver. This may be because the level of insulin does not directly reflect the liver insulin resistance like glucose(35, 36).
Researches showed that platelet count is related to NALFD and liver cirrhosis(37–39), and can reflect the degree of liver injury(40). Studies have also shown that platelet count is closely related to insulin resistance, and its severity and complications(41, 42). This may have the following reasons: (1) the influence of portal hypertension; (2) splenic sequestration of platelets; (3) liver damage may also cause TPO release defects and reduce platelet production in the bone marrow(43–45).
There are also some shortcomings in this study, for example, the included population is from the NHANES database, and the model still needs prospective research verification. Whether there are other indicators that can improve the accuracy of the model also needs to be explored in the future, but at present, the model can predict the occurrence of fatty liver with satisfactory accuracy by using blood biochemical indicators.