Association Between Remnant Cholesterol and Nonalcoholic Fatty Liver Disease: A Systemic Review and Meta-Analysis

Lipid disorders are related to the risk of nonalcoholic fatty liver disease (NAFLD). Remnant cholesterol (RC), a nonclassical and once-neglected risk factor for NAFLD, has recently received new attention. In this study, we assessed the relationship between the RC levels and NAFLD risk. We searched across PubMed, Web of Science, Embase, Cochrane Library, and China National Knowledge Infrastructure, with no restrictions on publication languages. Retrospective cohort studies and cross-sectional studies were enrolled from the inception of the databases until August 6, 2023. A random-effect model was applied to construct the mean difference, and a 95% confidence interval was applied to assess the relationship between the RC levels and NAFLD risk. We used two methods to estimate RC levels: Calculated-1 subtracts low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol from total cholesterol; Calculated-2 uses the Friedewald formula for LDL-C when triglycerides are <4.0 mmol/L, otherwise directly measured. A total of 265 published studies were selected through preliminary retrieval. Of these, six studies met the inclusion requirements and were enrolled in the meta-analysis. The RC level in the NAFLD group was significantly higher than that in the non-NAFLD group (mean difference: 0.18, 95% confidence interval: 0.10-0.26, P < 0.00001). We conducted subgroup analyses of computational methods and geographic regions. Notably, in the subgroup analysis of Calculation Method 2, the NAFLD group had significantly higher RC levels than the non-NAFLD group. On the other hand, in Calculation Method 1, the difference between the two groups was insignificant. In both the Asian and non-Asian populations, the RC levels were significantly higher in the NAFLD group than in the non-NAFLD group. The association of RC with an increased NAFLD risk was not dependent on the triglyceride. This meta-analysis suggests that elevated RC levels are associated with an increased risk of NAFLD. In addition to the conventional risk factors for fatty liver, clinicians should be concerned about the RC levels in the clinic.