BACKGROUND: Gestational diabetes mellitus as a common pregnancy complication carries metabolic risks for both the mother and infant. We and others have shown that ribonuclease L (RNase-L, an innate immunity regulator) regulates adipogenesis and insulin sensitivity of skeletal muscle. We further showed that its serum level was reduced in human subjects with impaired fasting glucose and metabolic syndrome. In this study we investigated its levels in gestational diabetes mellitus. METHODS: A total of 82 pregnant women who have received a one-step 75g oral glucose tolerance test (OGTT) for Gestational diabetes mellitus diagnosis were enrolled in this study, and their serum RNase-L levels during pregnancy were examined. Serum RNase-L levels were compared between women who did and did not develop Gestational diabetes mellitus. The risk for Gestational diabetes mellitus with the change of serum RNase-L concentration was estimated using a binary logistic regression model adjusting for age and body mass index. RESULTS: During pregnancy, serum RNase-L levels tended to descend with gestational age (P-for-trend = 0.008). The mean of serum RNase-L in the 1st, 2nd, and 3rd trimesters of pregnancy were respectively lower in the Gestational diabetes mellitus group compared with the controls (1st trimester: 17.1 ± 8.4vs.19.3 ± 7.2 μg/ml, P=0.328
2nd: 14.7 ± 5.9vs.18.6 ± 6.8 μg/ml, P=0.017
3rd: 13.6 ± 2.8vs.16.0 ± 3.5 μg/ml, P=0.005). CONCLUSION: This is the first study on how innate immune factor affect the pregnant women in developing GDM. The serum RNase-L levels were found to be negatively associated with GDM risk during pregnancy. This observation linked GDM with innate immunity and RNA metabolism in its pathophysiology.