Association between remnant lipoprotein cholesterol levels and risk of non-alcoholic fatty liver disease in non-obese populations: a Chinese longitudinal prospective cohort study

OBJECTIVES: The association between remnant lipoprotein cholesterol (RLP-C) levels and the incidence of non-alcoholic fatty liver disease (NAFLD) is unclear, especially in non-obese populations. SETTING: We used data from a health assessment database. The assessment was conducted at the Wenzhou Medical Center from January 2010 to December 2014. The patients were divided into low, middle and high RLP-C groups according to tertiles of RLP-C, and baseline metabolic parameters were compared among the three groups. Kaplan-Meier analysis and Cox proportional hazards regression were used to evaluate the relationship between RLP-C and NAFLD incidence. Additionally, sex-specific associations between RLP-C and NAFLD were examined. PARTICIPANTS: 16 173 non-obese participants from the longitudinal healthcare database. OUTCOME MEASURE: NAFLD was diagnosed using abdominal ultrasonography and clinical history. RESULTS: Participants with higher RLP-C levels tended to have higher blood pressure, liver metabolic index and lipid metabolism index than those with middle or low RLP-C (p<0.001). During the 5-year follow-up period, 2322 (14.4%) participants developed NAFLD. Participants with high and middle RLP-C levels were at a higher risk of developing NAFLD, even after adjusting for age, sex, body mass index and main metabolic parameters (HR 1.6, 95% CI 1.3, 1.9, p<0.001; and HR 1.3, 95% CI 1.1, 1.6, p=0.01, respectively). The effect was consistent in subgroups of different ages, systolic blood pressures and alanine aminotransferase levels, except for sex and direct bilirubin (DBIL). These correlations, beyond traditional cardiometabolic risk factors, were stronger in males than females (HR 1.3 (1.1, 1.6) and HR 1.7 (1.4, 2.0), p for interaction 0.014 for females and males, respectively). CONCLUSIONS: In non-obese populations, higher RLP-C levels indicated a worse cardiovascular metabolic index. RLP-C was associated with the incidence of NAFLD, independent of the traditional risk factors of metabolism. This correlation was more substantial in the male and low DBIL subgroups.