Evaluating the effects of vitamin D metabolism on glycemic parameters and atherosclerosis markers in prediabetic patients
Hulya Parildar1, Mumtaz Takir2, Asli Dogruk Unal2, Ozlem Cigerli1, Oyku Gulmez3, Feyza Dinc4 & Nilgun Demirag Guvener2
Background and aims: Hypovitaminosis D may be associated with metabolic parameters in addition to its well-known calcemic actions. There is increasing evidence that vitamin D metabolism affects the risk of insulin resistance although the underlying molecular mechanism of this association is not clear but on the basis of evidence it is not clear whether or not vitamin D supplementation therapy in vitamin D-deficient prediabetics affects the prevention of type 2 diabetes. Our study is designed as a 1-year prospective interventional study. In this study our specific aims are to evaluate the changes in vitamin D metabolism and their effects on glycemic parameters and atherosclerosis in prediabetic patients. We analysed the data cross-sectionally and assessed the preliminary results.
Materials and methods: Preliminary analysis included 81 prediabetic patients and 67 healthy volunteers as control group attending to the Outpatient Clinics. We supplemented the vitamin D-deficient patients. Descriptive statistics were presented as mean±S.D. and percentages. For statistical comparisons, Pearson Correlation, Fishers exact and Students t-tests were used.
Results: The mean age was 50.2±11.9 years (2479) in prediabetics and 45.1±13.5 (2079) years in the control group. There was a positive correlation between body mass index (BMI) and homeostasis model assessment of insulin resistance (HOMA IR) and HsCRP in the whole group (r=0.2, P<0.01, r=0.1, P=0.05 respectively). Mean HOMA IR and BMI values were statistically higher in the prediabetic group compared to the control group (P=0.001). The rate of vitamin D insufficiency were statistically higher in prediabetics (34/81) than in the control group (15/67) (P=0.05). We found no correlation between vitamin D levels and BMI, HOMA IR, HsCRP, age or sex in both groups. Mean carotis intima media thickness (CIMT) values were not correlated with vitamin D levels but were correlated with age in the whole group before and after supplementation (r=0.5, P<0.01, r=0.6, P<0.01 respectively). As the data were analysed at the 6 months after the supplementation of vitamin D: the HsCRP levels were decreased significantly in the prediabetic group (P=0.05). There was no significant change in the fasting plasma glucose (FBG), insulin and HbA1c levels in the vitamin D supplemented group.
Conclusion: The levels of vitamin D were lower in the prediabetic group than the control group. We found no correlation between vitamin D levels and CIMT and other parameters. The supplementation of Vitamin D did not seem to positively effect FBG, insulin and HbA1c levels except HsCRP levels. As our study continues, the data will accrue and we should be able to reanalyse the data and concentrate on evaluating the supplementation of vitamin D3 in groups at high risk of developing type 2 diabetes.