Can First Trimester Vitamin D Levels Predict Gestational Diabetes?

BackgroundIn recent years, a large number of domestic and international studies have shownthat there is a relationship between vitamin D concentrations and glucose metabolism.Vitamin D play an important role by combining vitamin D receptor (VDR) in the cellmembrane or nucleus. It has been found that VDR exists in many tissues and organsof the human body, some studies detected specific receptors for vitamin D inpancreatic β cells, suggesting a role for1,25-(OH)2D in the regulation of insulinsecretion. Vitamin D may directly or indirectly regulate β cell function andsecretion by binding its circulating active form,1,25-(OH)2D, to a β cellvitamin D receptor.while VDR are also detected on the peripheral insulin action targetorgans and tissues, such as liver, skeletal muscle and adipose cells, This suggests thatvitamin D also has an effect on the insulin sensitivity. So researchers believe thatvitamin D may be involved in glucose metabolism by regulating insulin secretion andinsulin sensitivity. But recently research shows that there is no relationship betweenvitamin D and insulin secretion, insulin sensitivity.Not so, relationship between vitamin D and gestational diabetes mellitus (GDM)is also one of the hot research topic.ObjectiveTo explore if early pregnancy vitamin D levels can predict gestational diabetes,to provide a theoretical basis for the early prediction of GDM, and analyze therelationship between early pregnancy serum vitamin D levels and insulin secretionand insulin sensitivity.Subjects and MethodsThe study was performed at the Second Affiliated Hospital of Guangzhou Medical University. Seven hundred and ten4-11weeks pregnant women were included in ourstudy, and collected blood samples to test serum25(OH)D and fasting insulin(FIns)when they were diagnosed with early pregnancy, finally219pregnant womenscreened GDM by75g oral glucose tolerance test (OGTT) at24-28weeks gestation.Our study use the diagnostic criteria of GDM that ADA recommended in2011:women underwent a standard75g OGTT between24-28weeks gestation.Diagnosticvalue as follows:0hours,1hours,2hours blood glucose values were5.1mmol/L,10mmol/L and8.5mmol/L.Any blood glucose value reaches or exceeds the critical value,the women diagnosed with GDM. We used HOMA-β and HOMA-IR to assess isletbeta cell function and insulin sensitivity,HOMA-β=[20×FINS(mU/L)]／[FPG(mmol/L)-3.5]，HOMA-IR=[FPG(mmol/L)×FINS(mU/L)]／22.5.Results（1） Seven hundred and ten pregnant women entered the study, duringfollow-up.One hundred and sixty three of them underwent GDM screening, twentycases were diagnosed as GDM(GDM group), the incidence of GDM was12.3%;Fiftysix cases suffered from abortion (abortion group); One hundred and forty threepregnant women the results of OGTT test were normal (control group).No differencewas found in age，gestational weeks and BMI between three groups（P＞0.05）.（2）In the total sample,25(OH)D concentration was28.3±9.4ng/mL. Deficientstatus (<30ng/mL) was present in62.6%of subjects.The25(OH)D concentration inGDM group and control group were29.7±10.4ng/mL and28.0±9.3ng/mLrespectively.No difference was found in25(OH)D concentration between twogroups(P=0.469).Then the25(OH)D concentration of one hundred and sixty threecases were divided into four bit block,using upper quartile group (8.6～20.7ng/mL)and lower quartile group (33.9～58.7ng/mL), No difference was found in theincidence of GDM and the incidence of the adverse pregnancy outcome (P>0.05).（3）Due to limited samples and consumed to analyze different indexes, and alsoconsidering the difference between batches detection reagent, finally128cases ofFIns samples were tested.for analyzing the relationship between early pregnancy serum vitamin D levels and insulin secretion and insulin sensitivity. Simple linearcorrelation analysis showed that there was no relationship between the25(OH) D andFPG, FIns, Ln(HOMA-β) and Ln(HOMA-IR), P>0.05.Taking HOMA-IR<1.586ascut-off point, we compared with the25(OH)D concentration of HOMA-IR1group(HOMA-IR<1.586) and group HOMA-IR2(HOMA-IR≥1.586), there is no significantdifference was found(27.8±7.6vs28.1±10.0,P=0.880).Conclusions1. Pregnant women with vitamin D insufficiency is a common phenomenon inGuangzhou city.2. First trimester serum25(OH) D levels can not predict the occurrence ofGDM.3. There is no relationship between first trimester serum25(OH) D levels andinsulin secretion and insulin sensitivity...