Circulating osteopontin and its association with liver fat content in non-obese women with polycystic ovary syndrome: a case control study

BACKGROUND Osteopontin (OPN) plays an important role in inflammatory processes and insulin resistance. Polycystic ovary syndrome (PCOS) is a reproductive metabolic disease associated with insulin resistance and metabolic abnormalities, including high levels of liver fat content (LFC). The objective of this study was to explore whether circulating OPN independently contributes to elevated LFC in non-obese PCOS patients. METHODS This study included 61 non-obese PCOS patients and 56 age-matched healthy women from Shanghai, China. After an overnight fast, all participants underwent anthropometric measurements, oral glucose tolerance tests, lipid profile and sex hormone measurements. Quantitative measurement of LFC by ultrasonography was performed. OPN concentrations were measured using ELISA. An independent samples t-test and the Mann-Whitney U test were performed to compare variables between the two groups; one-way ANOVA and Kruskal-Wallis test were performed to compare four subgroups of patients. Correlations were determined by Spearman's correlation tests. Stepwise multiple linear regression analyses were performed to assess for independent contributors. A receiver operating characteristic curve with the maximum Youden index was calculated for the optimal cut-off value. RESULTS In non-obese PCOS women, circulating OPN levels were increased in the subgroups with a higher body mass index (BMI) and free androgen index (FAI), and the LFC levels were increased in the elevated OPN subgroups. Moreover, increased OPN was associated with increased FAI and LFC in PCOS women, and the association between OPN and LFC was independent of triglyceride, HOMA-IR and FAI after adjusting for PCOS status in all participants. OPN combined with FAI and hsCRP may better predict NAFLD than WHR in this study cohort. However, there was no significant difference in circulating OPN levels between non-obese PCOS and normal control women. CONCLUSIONS Increased OPN levels may be related to FAI and elevated LFC in non-obese women with PCOS.