Serum Apelin Level in Normal and Gestational Diabetic Rats: Effect of Treatment with Vitamin D

Abstract
Background: Apelin peptide was identified in a wide variety of tissues including adipose tissue and it was linked to glucose homeostasis in obesity and diabetes. Apelin and its receptors were also identified in the placenta, and play a role in fluid and glucose transport. Vitamin D affects glucose metabolism and its deficiency was linked to gestational diabetes.
Aim of the Study: To estimate serum apelin level in normal and gestational diabetic rats and to study the effect of Vitamin D administration on serum apelin level in relation to some metabolic parameters in gestational diabetes.
Material and Methods: Healthy adult female albino rats were divided into the following groups, Group I (n=8): Virgin control rats; Group II (n=16): Normal pregnant control group (NP) subdivided into Group IIa (n=8) sacrificed on day 11 and Group IIb (n=8) sacrificed on day 19 of gestation; Group III (n=22): Gestational Diabetic group (GDM), rats were subdivided into Group IIIa (n=11) sacrificed on day 11 and Group IIIb (n=11) sacrificed on day 19; Group IV (n=11): Gestational diabetic Vitamin D3 treated group (GDM + vit D3), gestational diabetic rats received vitamin D3 (50IU/kg/ day) intra-peritoneal from day 10 till sacrificed on day 19. The following parameters were measured in all groups: BMI, blood glucose, serum insulin, lipid profile, C Reactive Protein (CRP), Tumor Necrosis Factor a (TNFa) and HOMA-IR was calculated.
Results: A significant increase in serum apelin level was found on day 11, while a significant decrease was found on day 19 of normal gestation relative to non-pregnant level. In GDM groups, apelin level significantly decreased in Group IIIa compared to Group IIa and in Group IIIb compared to Group II b. Vitamin D3 induced a significant increase in apelin level in Group IV compared to Group IIIb. Serum apelin level correlated negatively with blood glucose, HOMA-IR, TC, LDL and TNFa in Group III and IV.
Conclusion: Gestational diabetes induced significant decrease in serum apelin level in pregnant rats compared to normal pregnant gestational age matched control. Vitamin D3 supplementation in gestational diabetic rats induced significant increase in apelin level in association with a decrease in insulin resistance.