| Objective:To evaluate the effect of vitamin D supplement on the prevention of type 2 diabetes mellitus(T2DM), the impact of vitamin D on T2 DM and gestational diabetes mellitus(GDM) were analysed synthetically. Whether vitamin D supplement can improve the levels of blood sugar, blood lipid metabolism and body fat in T2 DM group was discussed.Methods:1. Meta-analysis of vitamin D and T2DM: A systematic literature search was conducted via Pub Med, MEDLINE, and Cochrane library to identify the eligibility of randomized controlled trials(RCTs) before April 2016. Meta-analysis was applied to estimate the combined weighted mean difference(WMD) and the corresponding 95% confidence interval(95% CI).2. The effects of vitamin D supplement on T2 DM patients: A multi-stage stratified random sampling method was used to select 270 patients aged 30 to 90 from the permanent residents in Lishui area of China, in which there were 78 men(28.89%) and 192 women(71.11%). The intervention group and control group were randomly divided by single blind method. The intervention group was given vitamin D3(capsules, H20113033, approved by the state commodity, trade name "Yue’Er", Shuangjing Pharmacy, Qingdao) at 800 IU/d orally for 6 months, while the control group was the blank control. The serum 25(OH)D levels at 0 and 6 months were measured respectively using chemiluminescence method. The data from population and laboratory were collected, to analyse the relationships between vitamin D and blood sugar, blood lipid metabolism index and obesity.3. Meta-analysis of vitamin D and GDM: A systematic literature search was conducted via Pub Med, MEDLINE, and Cochrane library to identify the eligibility of the studies before August 2015. Meta-analysis was applied to estimate the odds ratio(OR) and the WMD and the related 95% CI followed a predetermined protocol according to the Meta-analysis Of Observational Studies in Epidemiology(MOOSE) guidelines.Results:1. Totally, 14 studies of 19 RCTs were selected. 1278 patients were randomly assigned into the experimental group and control group, 632 of them were in the experimental group and 646 in the control group. Compared with the control group, Hb Alc and HOMA-IR of the experimental group were better, and the difference was statistically significant, but not FPG, HOMA-β and QUICKI.2. The total number of participants in this study was 270, of which half were in the intervention group and half were in the control group. There was no significant difference between the basic characteristics of two groups before intervention. Serum 25(OH)D level after intervention was significantly higher in the intervention group than the control group(29.07±7.45 ng/m L vs. 26.67±9.33 ng/m L, p<0.05). The fasting blood glucose concentration in the intervention group was slightly lower than the control group without significant difference [7.54(6.56, 9.32) mmol/L vs. 7.39(6.24, 9.08) mmol/L, p>0.05].3. In total, 20 studies of 9209 participants were selected for the final analysis according to the inclusion and exclusion criteria. Meta-analysis showed that women with vitamin D deficiency experienced a significantly increased risk to develop GDM(OR=1.53;95% CI, 1.33, 1.75) with a little heterogeneity(I2=16.20%, p=0.252). Two pooled ORs for vitamin D severe deficiency and insufficiency were calculated with the outcomes of 1.59(95% CI, 1.11, 2.27) and 1.39(95% CI, 1.07, 1.82), respectively. A noteworthy decrease of 4.93 nmol/L(95% CI,-6.73,-3.14) in serum 25(OH)D was demonstrated in the participants with GDM, and moderate heterogeneity was observed(I2=61.40%, p=0.001). Subgroup analysis with study design showed that there were obvious heterogeneities in nested case–control studies(I2>52.5%, p<0.07). Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. No sign of publication bias was observed when funnel plots and Begg’s and Egger’s tests were examined.Conclusions:1. Meta-analysis indicated that on the basis of the routine use of hypoglycemic drugs, vitamin D supplementation has a certain positive effect on the treatment of T2 DM and improvement of glucose metabolism.2. The serum 25(OH)D level of T2 DM patients is insufficient in Lishui, which is closely related to gender(man vs. woman), address(city vs. country) and waist circumference(WC). After vitamin D3 supplement, except the vitamin D levels increased in the intervention group, the rest indexes have no obvious change compared with the control group. In the case of the present vitamin D baseline levels, the effect of vitamin D3 supplement remains to be further confirmed.3. The evidence from this meta-analysis indicates a consistent association between vitamin D deficiency and an increased risk of GDM. However, well-designed RCTs are needed to elicit the clear effect of vitamin D supplementation on the prevention of GDM. |
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