Correlation of insulin resistance with serum apelin, fetuin-A and vitamin D concentrations in patients with gestational diabets

OBJECTIVE: Insulin resistance plays a central role in the pathophysiology of GDM. The effects of apelin, fetuin-A and 25(OH)D were investigated on the development of insulin resistance in patients with gestational diabetes. METHOD: Our study was designed as a case-control cross-sectional research and carried out between 1st September 2012 and 31th March 2013. The research groups included 38 pregnant women with gestational diabetes (GDM), 41 healthy pregnant women and 39 non-pregnant healthy women with similar demographic characteristics. IADPSG screening and diagnosis of gestational diabetes was made according to the criteria of the study. The demographic data of the study group, anthropometric measurements, clothing habits, medical and reproductive histories were recorded. After a period of at least eight hours of overnight fasting, blood samples were obtained to study the determined parameters. Insulin sensitivity was calculated according to QUICKI (Quantitative insulin sensitivity check index), insulin resistance was calculated according to HOMA-IR (Homeostasis model assessment) and pancreatic insulin secretion was calculated according to HOMA-ß (Homeostasis Model Assessment-beta). FINDINGS: In our study 38 pregnant women with GDM and 41 healthy pregnant women without GDM and 39 healthy non-pregnant women as control groups were included. HOMA insulin resistance index was higher in women with GDM group, and the difference was statistically significant (GDM: 2.01 ± 1.62, healthy pregnant women: 1.56 ± 1.75, healthy non-pregnant women: 1.03 ± 0.54, p = 0.024). Average serum apelin levels were lower in women with GDM, and the difference was statistically significant (GDM: 1.99 ± 1.36 µg/ml, healthy pregnant women: 2.95 ± 1.36 µg/ml, healthy non-pregnant women: 2.62 ± 1.67 µg/ml, p = 0.017). The mean serum fetuin-A levels were not statistically different between the groups. (GDM: 85.7 ± 27.4 µg/ml, healthy pregnant women: 85.4 ± 32 µg/ml, healthy non-pregnant women: 94.1 ± 26 µg/ml, p = 0.314 ). The mean serum 25-OH vitamin D levels were not statistically different between the groups (GDM: 19.1 ± 9.08 ng/ml, healthy pregnant women: 21.5 ± 10.7 ng/ml, non-pregnant healthy women: 20.6 ± 8.4 ng/ml, p = 0.531). A strong negative correlation observed was between HOMA insulin resistance index and serum apelin levels in women with GDM (r = -0.616, p = <0.001). One unit increase in the level of serum apelin induced % 40 decrease in the risk of developing GDM (RR = 0.604, p = 0.04). In each of the three group, there was no association between insulin resistance and serum fetuin-A and 25-OH vitamin D levels. RESULTS: Although apelin had been declared to be no effect on the development of GDM in earlier studies, our results showed that it may have an important preventive effect. Inadequate production of apelin during pregnancy may be a factor that facilitates the development of insulin resistance and hence gestational diabetes. In conclusion apelin can be an important molecule for the management of insulin resistance and this hypothesis should be examine in well designed controlled studies. Whether it may be an early diagnostic or at least an alarming marker of GDM, prospective studies planned in pregnant women beginning at the first trimester and continuing afterwards can give valuable results. Keywords: Gestational diabetes mellitus, apelin, fetuin-A, 25-OH vitamin D