Objective: Nonalcoholic fatty liver disease (NAFLD) is considered by some to be the hepatic manifestation of the metabolic syndrome (MS). However, others believe NAFLD is a distinct entity that actually initiates MS. Whichever is true, a definite linkage exists between both is generally accepted based upon the frequency of common occurrence and realization that insulin resistance (IR) is and realization that. The objective is to better understand the relationship between NAFLD and MS. Specifically, is there any concrete evidence that development of NAFLD precedes MS or vice versa? Another goal was to better comprehend capabilities of circulating aminotransferases (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]) and their ratio used commonly for diagnosis of NAFLD.
Methods: Data from 288 participants with fasting blood glucose (FBG) levels below the diabetic level (<125 mg/dL) and AST and ALT values in the normal range (<40 U/L) were examined. Correlations between ALT and AST and their ratio as independent variables with a variety of metabolic parameter were evaluated and compared.
Results: Like FBG, many significant positive correlations among glucose-insulin indices, body composition, blood pressure, dyslipidemias, and inflammation were discovered using ALT, and less so with AST, as the independent variable. In some cases, even stronger correlations in a negative direction with IR and MS were found with the ratio AST/ALT. Corroboration occurred when values in the lowest and highest quartiles of ALT and AST/ALT readings showed appropriate statistically significant differences.
Conclusions: The findings here suggest that both NAFLD and the MS very early in development have a common inciting mechanism(s)-most likely IR. Accordingly, the early concurrent temporal results are consistent with the concept that NAFLD is a hepatic manifestation of the IR associated with the MS. They do not exclude the possibility that once some liver functional adjustments take place, several aspects of the MS are bolstered further, perhaps via intensified heightening of IR.
Keywords: Nonalcoholic fatty liver disease; alanine aminotransferase; aspartate aminotransferase; fasting blood glucose level; insulin resistance; metabolic syndrome.