BsmI gene polymorphism of vitamin D receptor in obese Egyptian male medical students and its relationship with vitamin D deficiency

Abstract

Background Vitamin D regulates cell proliferation and differentiation and exhibits immunoregulatory, antiangiogenic, and antioxidant characteristics. Vitamin D deficiency and vitamin D receptor (VDR) gene polymorphisms have been associated with an increased risk of metabolic syndrome components such as abdominal obesity, with both vitamin D deficiency and VDR gene polymorphisms contributing to its development. Obesity, metabolic disorders, and bone mass defects are associated with VDR alleles. The importance of VDR in the etiology of obesity has been related to the existence of the VDR polymorphisms FokI, BsmI, ApaI, and TaqI. VDR expression in adipocytes affects energy metabolism and aids in obesity development. Objective The aim of this study was to examine a possible association between BsmI (B, b allele) polymorphism in the VDR gene and vitamin D status in obese Egyptian male medical students. Patients and methods This study was based on a comprehensive experiment known as “Nutritional Assessment of Medical Educational Students (NAMES)” that was completed in 2018 with 700 healthy participants (men and women). In total, out of the 700 participants 30 healthy men were enrolled in this study who matched our inclusion criteria. They attended Ain Shams University Hospital in Cairo between April 2019 and November 2020. This study was conducted at the Clinical Pathology Department of Ain Shams University Hospital, which is a part of the Faculty of Medicine. Participants were divided into two groups: Group I consisted of 12 obese men with nondeficient vitamin D levels (> 20 ng/dl), and Group II consisted of 18 obese men with deficient vitamin D levels (20 ng/dl). Peripheral blood samples were collected into EDTA tubes from all groups, and DNA was extracted and purified using spin purification for PCR (QIA amp DNA Mini Kit). A commercial real-time polymerase chain reaction (PCR) kit with predesigned TaqMan probes was used to analyze the single nucleotide polymorphism (SNP) (BsmI) rs 1544410 in the VDR gene. Results No statistically significant relationship was observed between vitamin D levels and all InBody bioelectrical impedance characteristics, as well as BsmI gene polymorphism and all InBody bioelectrical impedance parameters (P > 0.05). Regarding Bb and BB genotypes, no statistically significant difference was observed between Groups I and II. The prevalence of BB genotype was higher in vitamin-D-deficient individuals, and Bb genotype was more common among obese participants than BB genotype, which showed a higher prevalence of the “b” gene; however, these were not significant. Iron profile (iron level, ferritin level, TIBC, and transferrin saturation) and BsmI gene polymorphism showed no statistically significant relationship (P > 0.05). Glycated hemoglobin (HbA1c) level and BsmI gene polymorphism showed a statistically significant relationship (P = 0.002), with a higher mean value among Bb genotype carriers than among BB genotype carriers. Eosinophil count showed a statistically significant difference between BB and Bb genotype carriers (P = 0.045), with a higher mean value among Bb genotype carriers than among BB genotype carriers. Bsml gene polymorphism showed no statistically significant relationship with any other complete blood count parameters (P > 0.05.) Conclusion There was no significant relationship between VDR gene polymorphism (BsmI) and body mass index (BMI) nor between the different InBody bioelectrical impedance parameters. We noticed the prevalence of BB genotype among vitamin-D-deficient obese students and the frequency of the “b” allele among obese candidates according to the findings of our study. There was also no significant relationship between BsmI gene polymorphism and vitamin D levels. However, BsmI gene polymorphism and HbA1c levels and eosinophil count showed a relationship, which requires further investigation.

The Association of Vitamin D Receptor Gene Polymorphisms with Vitamin D, Total IgE, and Blood Eosinophils in Patients with Atopy

“…Chinese scientists have revealed that VDRs contribute to maintaining eosinophil homeostasis by regulating the gene transcription of eosinophil mediators [46]. Furthermore, a publication on VDR SNPs in obese Egyptian men reported findings indicating a statistically significant association between the VDR polymorphism rs1544410 and eosinophil counts, although no significant association was observed with vitamin D levels [47]. In contrast, we found no significant association between rs1544410 and eosinophils; however, indicators such as body mass index were not analyzed in our study.…”

Relationship Between Vitamin D Receptor Gene BsmI Polymorphism and Fibromyalgia Syndrome

“…Other authors found no association between the VDR gene BsmI polymorphism in postmenopausal women with osteoporosis [ 28 ] and obese Egyptian male-medical students [ 29 ]. A case-control study in the Kashmiri population has reported a significant association of VDR gene BsmI polymorphism with temporomandibular joint disorders [ 30 ].…”

Impact of vitamin D receptor polymorphisms in selected metabolic disorders

“…Perhaps, rs7975232 polymorphism may predict an increased risk of obesity and could help identify new strategies to treat this metabolic disorder. The study conducted by Khattab et al showed no significant relationship between rs1544410 and BMI or bioelectrical impedance parameters [26].…”

“…Other rs1544410 polymorphism (C>A,G,T) is located in intron 8 near the 3′ end. Due to its location, its strong linkage disequilibrium with a polyadenosine microsatellite repeat in the 3′UTR and may affect the VDR translational activity [26,27]. A study by Liu et al indicates that it may be associated with a reduced risk of T2D in Asians [12 ▪▪ ].…”