Association of vitamin D and vitamin D receptor gene polymorphisms with chronic inflammation, insulin resistance and metabolic syndrome components in type 2 diabetic Egyptian patients

Association of vitamin D receptor gene polymorphism (VDR) with vitamin D deficiency, metabolic and inflammatory markers in Egyptian obese women

Vitamin D deficiency might contribute to the pathogenesis of metabolic syndrome and could cause immune disturbance. The aim of this study is to analyze the associations between Vitamin D receptor (VDR) gene polymorphism, serum 25-hydroxy vitamin D, metabolic and inflammatory biomarkers in Egyptian obese women. The study included 201 obese women with vitamin D deficiency and 249 obese matched age healthy controls with sufficient vitamin D levels. Their age ranged between 25 and 35 years. Inflammatory biomarkers (interleukin-6 and C-reactive protein) and serum 25(OH) D were measured by enzyme-linked immunosorbent assay. Insulin resistance (IR) was determined by the homeostasis model assessment of insulin resistance (HOMA-IR).Vitamin D receptor (VDR) gene polymorphisms of FokI, ApaI, and TaqI were studied by PCR using the restriction fragment length polymorphism (RFLP) technique. Obese women with vitamin D deficiency had significant higher values of inflammatory and metabolic parameters compared to controls. Multivariable-logistic regression showed associations between 25(OH) D deficiency and metabolic components when comparing cases with controls. Moreover, cases carrying polymorphic alleles showed significant lower levels of serum 25(OH) D and higher HOMA-IR, blood pressure levels and lipid parameters compared to those with the wild type homozygote in obese cases with vitamin D deficiency. Vitamin D deficiency in Egyptian obese women with vitamin D deficiency is associated with abnormal metabolic components and abnormal inflammatory biomarkers. Moreover, VDR polymorphisms play important role in immune and inflammation status.

The associations between VDR BsmI polymorphisms and risk of vitamin D deficiency, obesity and insulin resistance in adolescents residing in a tropical country

Background

The vitamin D receptor (VDR) gene is expressed abundantly in different tissues; including adipocytes and pancreatic beta cells. The rs1544410 or BsmI single nucleotide polymorphism (SNP) in the intronic region of the VDR gene has been previously associated with vitamin D levels, obesity and insulin resistance.

Aims

This study was aimed to examine the association between BsmI polymorphism and risk of vitamin D deficiency, obesity and insulin resistance in adolescents living in a tropical country.

Methods

Thirteen-year-old adolescents were recruited via multistage sampling from twenty-three randomly selected schools across the city of Kuala Lumpur, Malaysia (n = 941). Anthropometric measurements were obtained. Obesity was defined as body mass index higher than the 95^th percentile of the WHO chart. Levels of fasting serum vitamin D (25-hydroxyvitamin D (25(OH)D)), glucose and insulin were measured. HOMA-IR was calculated as an indicator for insulin resistance. Genotyping was performed using the Sequenom MassARRAY platform (n = 807). The associations between BsmI and vitamin D, anthropometric parameters and HOMA-IR were examined using analysis of covariance and logistic regression.

Result

Those with AA genotype of BsmI had significantly lower levels of 25(OH)D (p = 0.001) compared to other genotypes. No significant differences was found across genotypes for obesity parameters. The AA genotype was associated with higher risk of vitamin D deficiency (p = 0.03) and insulin resistance (p = 0.03) compared to GG. The A allele was significantly associated with increased risk of vitamin D deficiency compared to G allele (adjusted odds ratio (OR) = 1.63 (95% Confidence Interval (CI) 1.03–2.59, p = 0.04). In those with concurrent vitamin D deficiency, having an A allele significantly increased their risk of having insulin resistance compared to G allele (adjusted OR = 2.66 (95% CI 1.36–5.19, p = 0.004).

Conclusion

VDR BsmI polymorphism was significantly associated with vitamin D deficiency and insulin resistance, but not with obesity in this population.

Vitamin D receptor gene FokI variant in diabetic foot ulcer and its relation with oxidative stress

PURPOSE

The patient's suffering and financial costs affiliated with Diabetic Foot Ulcer (DFU), as one of the most important complications of diabetes, are highly undesirable and this highlights the importance of preventive medicine about this disorder. Furthermore hyperglycemia causes generation of free radicals which leads to oxidative stress (OS). Hence, this study aims to examine the association between vitamin D receptor (VDR) gene FokI polymorphism and DFU in Iranian population and also its correlation with OS biomarkers.

MATERIALS AND METHODS

In a case-control study, a total of 212 patients with type 2 diabetes with and without diabetic foot ulcer were included. Genotyping was conducted by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. Samples were analyzed for thiobarbituric reactive substances (TBARS) and ferric reducing ability of plasma (FRAP) as markers of OS.

RESULTS

The results indicated a significant difference in genotype frequencies of VDR gene FokI polymorphism in patients with diabetic foot ulcer in comparison to those without diabetic foot ulcer (TT+TC vs. CC p=0.04; OR=1.76; 95% CI=1.02-3.05). Moreover, the patients carrying the T allele had a significantly higher level of TBARS (p=0.01).

CONCLUSIONS

We found a significant association between FokI functional variant of VDR gene and diabetic foot ulcer in an Iranian population. Increased levels of TBARS in patients carrying the T allele of FokI polymorphism indicate an association between this variant and OS in patients with diabetes.

Vitamin D Receptor Gene Polymorphisms Are Associated with Abdominal Visceral Adipose Tissue Volume and Serum Adipokine Concentrations but Not with Body Mass Index or Waist Circumference in African Americans: The Jackson Heart Study

BACKGROUND

The biological actions of vitamin D are mediated through the vitamin D receptor (VDR). Single-nucleotide polymorphisms (SNPs) in the VDR gene have been previously associated with adiposity traits. However, to our knowledge, few studies have included direct measures of adiposity and adipokine concentrations.

OBJECTIVE

We examined the association of tagging SNPs in the VDR gene with multiple adiposity measures, including waist circumference (WC), body mass index (BMI), body fat percentage, subcutaneous and visceral adipose tissue (VAT) volume, and serum adipokine (adiponectin and leptin) concentrations in adult African Americans (AAs).

METHODS

Data from 3020 participants (61.9% women; mean age, 54.6 y) from the Jackson Heart Study were used for this analysis. Forty-five tag SNPs were chosen with the use of genotype data from the International HapMap project. We used linear regression to test the associations of imputed VDR SNPs with each of the traits, adjusted for age, sex, educational status, physical activity, smoking, alcohol intake, serum vitamin D concentration, European ancestry, and multiple testing.

RESULTS

The G allele of the SNP rs4328262 remained associated with increased VAT volume after multiple testing correction (β = 45.7; P < 0.001). The A allele of another SNP (rs11574070) was nominally associated with body fat percentage (β = 0.96; P = 0.002). None of the VDR SNPs analyzed showed any link with WC or BMI. The A allele of rs2228570 (β = 0.08; P = 0.001) for men and the T allele of rs2853563 (β = 0.04; P < 0.001) for women remained positively associated with serum adiponectin concentrations after multiple testing correction.

CONCLUSION

Although we did not find any association for anthropometric measures, we did observe associations of VDR variants with serum adipokines and with the more metabolically active fat, VAT. Therefore, our findings demonstrate a possible role of VDR variants in regulating adipose tissue activity and adiposity among AAs.

Lack of association between FokI polymorphism in vitamin D receptor gene (VDR) & type 2 diabetes mellitus in the Tunisian population

BACKGROUND & OBJECTIVES

The impact of several environmental and genetic factors on diabetes is well documented. Though the association between the vitamin D receptor (VDR) gene polymorphisms and type 2 diabetes mellitus (T2DM) has been analyzed in different ethnic groups, the results have been inconsistent. The aim of this study was to evaluate the possible association between VDR FokI polymorphism and genetic susceptibility to T2DM in Tunisian population.

METHODS

A total of 439 unrelated patients with T2DM and 302 healthy controls were included in the study. Genomic DNA was extracted from blood and genotyped for the single nucleotide polymorphism (SNP) of FokI (T/C: (rs2228570) by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The genotype distribution and the relative allelic frequencies for the FokI polymorphism were not significantly different between T2DM and controls: in T2DM patients the frequencies of the CC, CT, and TT genotypes were 52.6, 41.0, and 6.1 per cent, respectively, and in controls the genotype frequencies were 55.6, 38.7, and 5.6 per cent, respectively. In our study, the TT genotype of the FokI polymorphism was not associated with T2DM (OR =1.19, 95% CI 0.63 - 2.25, P=0.577).

INTERPRETATION & CONCLUSIONS

Our study showed no significant association of the FokI polymorphism in the vitamin D receptor gene with type 2 diabetes mellitus in Tunisian population.

The Role of Vitamin D in Diabetes and Cardiovascular Disease: An Updated Review of the Literature

The dietary reference values for Vitamin D were set primarily considering its role in bone health, but with the discovery of Vitamin D receptors throughout body tissues, new links with other health conditions are now studied, such as for diabetes and cardiovascular diseases (CVD). This paper shall analyze and examine all new research studies carried out, especially in 2013–2015 regarding diabetes mellitus (DM) and cardiovascular diseases (CVD). Vast research has been carried out to establish strong relationship between Vitamin D serum levels, supplementation, diabetes, and CVD. However, the results from researches identified in this paper are disputable. Benefits of Vitamin D adequate levels were recognized from gestational period until later in disease development such as diabetes and/or CVD, but since not all studies are in agreement further investigation is suggested. Researches conducting large randomized controlled trials, exploring range of supplement doses, with variable baseline serum Vitamin D levels, and inclusion of array of associated parameters, are still required to conduct large-scale analysis and draw conclusion as a risk factor. Until then it is possible to conclude that maintenance of serum Vitamin D levels holds advantageous aspects in diabetic and cardiovascular conditions, and people should strive to attain them.

The relationship between vitamin D status, physical activity and insulin resistance in overweight and obese subjects

Type 2 diabetes mellitus (T2DM) incidence has been increasing worldwide along with the rise of obesity and sedantery lifestyle. Decreased physical activity (PA) and obesity have also been associated with the low vitamin D levels. We aimed to determine the association between PA, vitamin D status and insulin resistance in overweight and obese subjects. A total of 294 (186 female, 108 male) overweight or obese subjects were included in this cross-sectional study. 25-hydroxy vitamin D (25(OH)D), insulin, fasting plasma glucose (FPG) and HbA1c levels were measured in blood samples. Body mass index (BMI), HOMA-index and total score of International Physical Activity Questionnaire-long form (IPAQ) were calculated. Insulin resistant subjects were compared with the non-resistant group. The mean age of the participants was 45 ± 12.25 and 41.39 ± 10.32; 25(OH)D levels were 8.91 ± 4.30 and 17.62 ± 10.47 ng/dL; BMIs were 31.29 ± 4.48 and 28.2 ± 3.16 kg/m², IPAQ total scores were 548.71 ± 382.81 and 998 ± 486.21 in the insulin resistant and nonresistant subjects, respectively. There was a statistically significant difference in terms of 25(OH)D, FPG, insulin levels, IPAQ total score and BMI between the two groups (p = 0.001, p = 0.001, p = 0.001, p = 0.001, p = 0.001).Significantly low 25(OH)D levels, high BMI and low PA in insulin resistant subjects confirm the importance of active lifestyle and the maintenance of normal vitamin D levels in overweight and obese subjects in prevention of T2DM.

THE ROLE OF VITAMIN D IN THE PATHOGENESIS OF CHRONIC NON-COMMUNICABLE DISEASES

This review shows the role of vitamin D in the regulation of not only the level of calcium, but also in the pathogenesis of chronic systemic inflammation, disruption of insulin sensitivity of tissues. The sufficient levels of vitamin D in the blood can lead to reduced risk of developing type 2 diabetes, obesity, autoimmune destruction of pancreatic β-cells, certain cardiometa-bolic risk factors, and therefore cardiovascular disease. Perhaps preparations of vitamin D in the near future may become additional and necessary nutritional substances for correction of insulin resistance, cardiovascular disease, chronic inflammation and prevention of disorders of glucose metabolism.