Vitamin D in healthy Tunisian population: Preliminary results.

Background: Vitamin D deficiency is one of the most common medical conditions worldwide. In Tunisia, several studies evaluated Vitamin D status, but this was concerning specific populations (pregnant women, obese or diabetic patients and children with asthma). The only study that evaluated Vitamin D status in a healthy Tunisian population was conducted by Meddeb and associeties in 2002. The update of data available, based on the currently recommended limits, is necessary. This study aimed to estimate the prevalence of hypovitaminosis D in a healthy Tunisian population, and correlate the values with potential risk factors. Methods: It was conducted on 209 Tunisian healthy subjects. Data collected included clinical characteristics and dietary intakes. We measured 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH), glycemia, creatinine, calcium, phosphorus, and alkaline phosphatase concentrations. Hypovitaminosis D was retained for 25(OH)D concentrations <75 nmol/L. Vitamin D deficiency was defined by 25(OH)D concentrations <25 nmol/L. Results: The prevalence of hypovitaminosis D and vitamin D deficiency were respectively 92.3% and 47.6%. The main factors that were significantly associated with low vitamin D levels in our multivariate analysis were veiling, living in rural areas and sunscreen use. However, sex, age, socioeconomic level, phototype, solar exposure score, smoking and bone mass index, were not statistically associated with hypovitaminosis D. The study of relationship between vitamin D status and serum PTH levels showed a significative and negative correlation (P < 0.005). Conclusions: Given the high prevalence of vitamin D, an adapted health policy is essential. A widespread vitamin D supplementation and food fortification seems to be necessary in Tunisia.

FGF 23, PTH and vitamin D status in end stage renal disease patients affected by VDR FokI and BsmI variants.

OBJECTIVES: The aim of this study was to evaluate the association between two VDR SNPs FokI and BsmI and mineral status in ESRD patients. DESIGN AND METHODS: Our case-control study included 100 patients with chronic renal failure in ESRD and 149 healthy subjects. We measured the serum Vitamin D levels and the serum intact PTH level by Electrochemiluminescence Technology (cobas E411 analyzer). We evaluated the serum FGF23 levels by indirect ELISA method. The genotyping of two VDR gene variants FokI and BsmI was carried out by PCR-RFLP technique. RESULTS: In our study, the FokI TT genotype was associated with lower risk of ESRD development (OR = 0.176, Padj = 0.039). The difference in PTH and FGF23 levels between cases and controls was statistically significant. The expression of FokI CT genotype in subjects with diabetic nephropathy was associated with a negative correlation between VD and PTH levels (r = -0.620, P = 0.032) and a positive correlation between VD and FGF23 levels (r = 0.967, P = 0.012). A significant differences in VD levels between patients and controls was observed in the presence of FokI TT (P = 0.044) and CT (P = 0.036) genotypes. The expression of FGF23 serum level was significantly elevated in patients than in controls in the presence of the FokI CC and BsmI AG genotypes. CONCLUSIONS: In conclusion, our study shows the existence of an association between VDR FokI, BsmI polymorphisms and mineral status in ESRD patients. The presence of VDR variants affect the protein expression of VD, phosphorus, FGF23 and PTH.