Polimorfismo do receptor de vitamina D e sua relação com o metabolismo ósseo em mulheres pós-menopausa

Abstract

Introduction: Globally, an increase in the elderly population has been observed, mainly in relation to the concentration of women. It is known that postmenopausal osteoporosis is a chronic problem that affects the health of women in this age group. Vitamin D plays an important role in bone metabolism and is mediated by the vitamin D receptor (VDR), which has polymorphisms in the VDR gene, which in turn can alter the biological functions of vitamin D. The main one is the FokI polymorphism, however, studies correlating it with reduced bone mineral density are very controversial and in the case of Brazil, scarce. Objectives: To determine the FokI polymorphism of the vitamin D receptor, its relationship with bone mineral density and serum levels of bone metabolism markers in postmenopausal women. Also, evaluate the sun exposure and the possible relationship with vitamin D levels in this group of women. Materials and methods: Observational cross-sectional study with 178 postmenopausal women who performed bone densitometry at a bone densitometry service. After agreeing to participate in the study, a questionnaire regarding socio-demographic, economic and life habits data was collected and a sample was collected for parathyroid hormone, vitamin D and other biochemical parameters. Above all, the FokI polymorphism of the VDR gene was evaluated by means of the polymerase chain reaction technique, followed by the DNA fragments polymorphism (RFLP) technique. Results: The biochemical parameters evaluated were within normal range, in contrast, the mean vitamin D of 24.85 ± 9.06 ng/mL. The genotypic distribution found for FokI polymorphisms was 54% of the females presented FF phenotype, 35% for Ff and 11% for ff. ff genotype had a reduced femoral bone mineral density when compared to the other genotypes (p = 0.028). In relation to sun exposure, the majority of the individuals reported daily exposure less than 1h per day. From these, most (67%) were exposed during the hours that were not ideal to produce vitamin D. Vitamin D supplementation was shown to be ineffective, since in the groups classified as deficient and insufficient for vitamin D, the proportion between those who use and do not use is similar. Conclusion: The studied population demonstrated levels of vitamin D below the recommended levels, besides a photoexposure profile not adequate to obtain the ideal levels of this substance. It adds to this, the need to conduct an assessment on the form of vitamin D supplementation for this population.