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Objective: Recent years, accumulating researches suggested that vitaminD receptor exists in several kinds of cells and tissues, including immune cells,pancreas, skin, and gastrointestinal tract. Therefore, except for regulatingcalcium phosphorus metabolism, vitamin D plays a role in many systems likeimmune system, endocrine system, etc. This project aimed to investigate thelevel of serum25(OH)D3in individuals with different glucose tolerance fromShijiazhuang area Hebei province and explore the relationship between25(OH)D3and islet β cell function.Methods:1Subjects: A total of131subjects who received75g oral glucose-tolerance-test (73male, average54.58±1.27years,58female, average56.40±1.26years) were recruited from March2013to November2013at TheThird hospital of Hebei medical university. Subjects with type1diabetes orspecific type of diabetes, acute complications of diabetes like diabeticketoacidosis and hyperglycemic hyperosmolar status, or tumor, immunesystem disease, connective tissue disease, or thyroid and parathyroid glandsfunctional defection, or osteoporosis and metabolic disease, or taking drugslike antiepileptic drug and glucocorticoids, or treated with vitamin D or itsmetabolites and calcium supplement for3months, or has a history of sunexposure for a week, or coffee and tea drinkers were excluded. They weredivided into3groups according to the World Health Organization (WHO)1999diagnostic criteria for diabetes, including normal glucose tolerance(NGT) group (n=36), impaired glucose regulation (IGR) group (n=45), andtype2diabetes (T2DM) group (n=50). This study was approved by theinstitutional review board of Hebei Medical University. Written informedconsent was obtained from all subjects. 2Methods: Human body parameters including height, weight, waistcircumference, hip circumference, systolic blood pressure (SBP), and diastolicblood pressure (DBP) were measured by the same researcher. Body massindex (BMI) and waist-hip ratio (WHR) were calculated. Biochemicalparameters and serum25(OH)D3were measured as follows: venous bloodsamples were collected from all subjects who had been fasting over8hovernight. And the triglyceride (TG), total cholesterol (TC), high-densitylipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol(LDL-C) were measured by automatic biochemistry analyzer(OLYMPUSAU-2700, Japan). Blood glucose was detected by glucose oxidasemethod. Fasting insulin (FINS) was detected by radioimmanoassay (RIA).Serum25(OH)D3was assayed by enzyme-linked immunosorbent assay(ELISA) on MK3microplate reader. The intra and inter-assay coefficients ofvariation (CV) were <9%and <15%, respectively. The indexes used forcalculations were as follows: AUCINS(mIU·L-1·h)(Area under thecurve)=1/4S0+1/2S30+3/4S60+S120+1/2S180, HOMA-IR (Homeostasis modelassessment-insulin resis-tance)=FPG(mmol/L)×FINS(mIU/L)/22.5,HOMA-β (Homeostasis model assessment of islet β cell)=20×FINS(mIU/L)/[FPG(mmol/L)－3.5], ΔINS30/ΔG30(early-phase insulin secretion)=(INS30－FINS)(mIU/L)/(PG30－FPG)(mmol/L).3Satistical analysis: Data wereanalyzed by SPSS13.0. Normal distribution data were expressed asmeans±SD. Non-normal distribution data were expressed as median (1~3quantile). Comparison between groups: Measurement data which were normaldistribution and homogeneity were compared by one-way analysis of variance(ANOVA). LSD-t test was used between groups. Measurement data that werenon-normal distribution used Kruskal-Wallis test, while Bonferroni methodwas used between groups. The Pearson correlation analysis and Spearmanrank correlation analysis were used for analysis between25(OH)D3and otherparameters. Multiple stepwise regression analysis for multivariate analysis.Bonferroni method considered P<0.017to be statistically significant. The restcomparison considered P<0.05to be statistically significant. Results:1The levels of serum25(OH)D3were significantly lower in T2DMgroup than those in IGR group and NGT group(P<0.05). Compared with NGTgroup, fasting serum25(OH)D3levels were significantly decreased in IGRgroup(P<0.05).2Serum25(OH)D3level was positively correlated with FINS, AUCINS,HOMA-β and ΔINS30/ΔG30(r=0.296，r=0.524，r=0.541，r=0.693, all P<0.05),whereas it was negatively correlated with BMI, WC, HC, WHC, FPG and2hPG (r=-0.304，r=-0.273，r=-0.246，r=-0.175，r=-0.494，r=-0.600，all P<0.05).There was no correlation between25(OH)D3and AGE, WHR, SBP, DBP, TC,TG, LDL-C, HDL-C, LP(a), HOMA-IR (all P>0.05). Multiple regressionanalysis showed that2hPG, ΔINS30/ΔG30were influential factors of serum25(OH)D3levels. Y=24.651+0.204×ΔINS30/ΔG30-0.178×2hPG.Conclusions:The level of25(OH)D3is associated with obesity, blood glucose andinsulin secretion. Measurement of serum25(OH)D3concentrations might be apredictor in type2diabetes and prediabetes.
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