C-Peptide: A Mediator of the Association Between Serum Uric Acid to Creatinine Ratio and Non-Alcoholic Fatty Liver Disease in a Chinese Population With Normal Serum Uric Acid Levels
Chifa Ma, Yiwen Liu, Shuli He, Jingbo Zeng, Pingping Li, Chunxiao Ma, Fan Ping, Huabing Zhang, Lingling Xu, Wei Li, Yuxiu Li
Abstract
Background The data on the relationship between normal-ranged serum uric acid (SUA), β-cell function, and non-alcoholic fatty liver disease (NAFLD) are complicated and insufficient. Moreover, uric acid is excreted by kidney, and SUA levels may be affected by renal function. Thus, we introduced a renal function-normalized index [serum uric acid to creatinine ratio (SUA/Cr)] into the study and explored the association between SUA/Cr, C‐peptide and NAFLD in a Chinese population with normal SUA levels by a cross-sectional analysis. Materials and Methods A total of 282 individuals with normal SUA levels and different glucose tolerance status from a diabetes project were included in the study (mean age = 53.7± 10.5 years; women = 64.50%). NAFLD was diagnosed by abdominal ultrasonography (NAFLD, n=86; without NAFLD, n=196). Trapezoid formula was used to calculate area under the curve of C‐peptide (AUC CP ) from 4 points (including 0, 30,60, and 120min) during 2-h oral glucose tolerance test. Spearman correlation analysis was used to explore the correlation between SUA/Cr, AUC CP and NAFLD risk factors. Multiple logistic regression analysis was used to explore the association between SUA/Cr or AUC CP and NAFLD. Mediation analysis was used to explore whether AUC CP mediated the association between SUA/Cr and NAFLD. Results Individuals with NAFLD had significantly higher SUA/Cr and AUC CP than those without NAFLD(P<0.05). Spearman correlation analysis showed that both SUA/Cr and AUC CP were significantly associated with many NAFLD risk factors, and SUA/Cr was positively correlated with AUC CP (P<0.05). Multiple logistic regression analysis indicated that SUA/Cr and AUC CP were positively associated with NAFLD incidence (P<0.05). Medication analysis indicated that SUA/Cr had a significant direct effect on NAFLD (β =0.5854, 95% CI: 0.3232–0.8966), and AUC CP partly mediated the indirect effect of SUA/Cr on NAFLD incidence (β =0.1311, 95% CI: 0.0168–0.4663). Conclusions SUA/Cr was positively associated with NAFLD incidence, and AUC CP partly mediated the association in a Chinese population with normal SUA levels. Thus, we should pay more attention to high-normal SUA and C-peptide levels due to their predictive power in NAFLD incidence.