Evaluation of association studies and a systematic review and meta-analysis of VDR polymorphisms in type 2 diabetes mellitus risk

Delving the vitamin D receptor variation and expression profiles in the context of type 2 diabetes among families

BACKGROUND

Vitamin D is essential for insulin secretion and sensitivity. Consequently, its inadequacy is linked to higher insulin resistance and Type 2 Diabetes (T2D). The Vitamin D receptor (VDR) gene is one potential candidate for T2D, and multiple polymorphisms in VDR have been examined in various populations, but no conclusive answers have been provided.

OBJECTIVES

This study was designed to evaluate the susceptibility of VDR gene polymorphism and its expression in diabetic families in Pakistan.

METHODOLOGY

In this family-based study, twenty diabetic families with a positive family history of T2D and at least three T2D patients were recruited from outpatient clinics and public hospitals. The current study comprised 143 individuals with 55 affected and 88 unaffected individuals. Blood samples of the selected families were collected. DNA was extracted from the collected samples and the PCR-RFLP method was followed to identify the genotyping and RT-qPCR for expression. Phenotypic and genotypic pedigrees of the families were developed by the progeny online tool. The association values of SNPs were determined by TDT and DFAM analysis implemented on Plink software.

RESULTS

The results explained a significant familial aggregation among phenotypic characters including Age, Gender, BMI (body mass index), age of disease diagnosis, disease duration, and blood pressure in the probands, affected FDRs (First Degree Relatives) and affected SDRs (Second Degree Relatives). A significant association of rs731236 C/T (OR = 1.522), rs2228570 C/T (OR = 1.327) with p < 0.05. Whereas, for rs1544410 G/A (OR = 0.9706) and rs7975232 T/G (OR = 0.7368) no considerable association evidence was seen (p > 0.05) in families. The mRNA expression of VDR increased threefold (p = 0.0204) in patients compared to controls. Variation-based expression analysis exhibited that the rs2228570 genotype influences the expression.

CONCLUSION

A linkage was found among the FDRs with probands. Variation in the gene VDR at loci rs731236 and rs2228570 was associated with familial T2D. However further research is required to explore more genetic factors that could influence T2D risks in families.

Level of biochemical parameters in patients with type 2 diabetes mellitus depending on the genotype of the FokI polymorphism in the vitamin D3 receptor (VDR gene)

OBJECTIVES

Diabetes mellitus type 2 (T2DM) is a multifactorial and polygenic disorder characterised by chronic hyperglycaemia accompanied by impaired lipid, carbohydrate, and protein metabolism. The disease is associated with several genetic polymorphisms, including the FokI polymorphism in the vitamin D receptor (VDR) gene.

METHODS

We conducted a study of 327 probands (191 T2DM patients, 136 controls), with a mean age 65.06 (SD ± 10.88) years of patients with T2DM and 58.89 (SD ± 6.59) years in the healthy probands. We investigated the association between FokI polymorphism and biochemical parameters in T2DM patients in the Slovak population. Anthropometric measurements, biochemical, and genetic analysis were statistically evaluated by Statistica ver.13 software using t-tests.

RESULTS

Biochemical analysis confirmed significantly higher mean values of total cholesterol (TC), triglyceride (TG), glucose (GLU), and uric acid (UA) (p < 0.001) in T2DM probands and statistically significantly lower values of high-density lipoprotein (HDL), cholesterol and vitamin D (p < 0.001). Allele frequencies and genotype distributions of the FokI (rs2228570) polymorphism were not significantly different between T2DM patients and controls (p = 0.909). Patients with T2DM and TT genotype had the highest glucose level of 11.39 (SD ± 2.32) uU/ml (p < 0.001).

CONCLUSION

Our study did not provide evidence for an association of the investigated FokI polymorphism of the VDR gene with T2DM in the Slovak population. Further research is needed to evaluate the impact of single nucleotide polymorphisms (SNPs) in the VDR gene, focusing on related genetic analyses in a larger T2DM cohort.

Impact of vitamin D receptor polymorphisms in selected metabolic disorders

PURPOSE OF REVIEW

Vitamin D (vitD) can regulate metabolic pathways in adipose tissue and pancreatic β cells by interacting with its vitamin D receptor (VDR). The aim of this study was to review original publications published in the last months and verify the relationship between genetic variants in the VDR gene and type 2 diabetes (T2D), metabolic syndrome (MetS), overweight, and obesity.

RECENT FINDINGS

The recent studies concern genetic variants located in the coding and noncoding regions of the VDR gene. Some of the described genetic variants may affect VDR expression or posttranslational processing altered functionality or vitD binding capacity of VDR. Nevertheless, the data collected in recent months on the assessment of the relationship between VDR genetic variants and the risk of T2D, MetS, overweight, and obesity still do not give a clear answer to whether they have a direct impact on these metabolic disorders.

SUMMARY

Analysis of the potential association between VDR genetic variants and parameters such as glycemia, body mass index, body fat, and lipid levels improves the current understanding of the pathogenesis of T2D, MetS, overweight, and obesity. A thorough understanding of this relationship may provide important information for individuals with pathogenic variants and enable the implementation of appropriate prevention against the development of these disorders.

Association of Vitamin D Receptor Gene Polymorphisms with Cardiometabolic Phenotypes in Hispanics: A Life Course Approach

The vitamin D receptor (VDR) is vital for maintaining calcium and phosphate balance and regulating bone metabolism. Recent research has suggested that VDR also plays an essential role in metabolic diseases. Previous studies on non-Hispanic whites have shown that VDR single nucleotide polymorphisms (SNP) are associated with cardiometabolic phenotypes. However, the association between VDR SNPs and cardiometabolic traits in Hispanics remains unclear. This study investigated the association between VDR SNPs and cardiometabolic phenotypic data in self-reported Hispanics (n = 1610) from the Arizona Insulin Resistance registry and Sangre Por Salud Biobank. The study population was predominantly female (66.4%) with a mean age of 40 ± 14 years (n = 121 <18 years) and an average body mass index (BMI) of 29.8 ± 6.3 kg/m2. We performed a genotyping association analysis of VDR SNPs (Taq1-rs731236, Fok1-rs2228570 and Apa1-rs7975232) with cardiometabolic traits using linear regression models. The results showed that Taq1 and Apa1 were strongly associated with systolic blood pressure (SBP) in children (<18 years), while Fok1 was associated with measures of adiposity, including fat mass, waist circumference, and BMI. In age-stratified adult (≥18 years) models, Taq1 was strongly associated with hemoglobin A1c, while Apa1 was associated with BMI and fasting glucose. Fok1 had no significant associations in the adult models. In conclusion, the VDR SNPs were associated with several cardiometabolic phenotypes in this Hispanic sample, but the type and strength of the associations varied by age group.

Clinical and genetic aspects of menopausal hormone therapy - a modern paradigm. What changed COVID-19 pandemic?

In the modern paradigm of public health protection, much attention is paid to the health of women in peri- and postmenopause, and a personalized approach prevails. It is generally recognized that the pathogenetic therapy of menopausal disorders is hormone therapy. But the COVID-19 pandemic has made its own adjustments to the routine strategy of choosing menopausal hormone therapy (MHT). The purpose of this review was to analyze studies on the dependence of the effectiveness of MHT on clinical and genetic aspects in the context of the ongoing COVID-19 pandemic. The review highlights the main risks of MHT for thromboembolic diseases and coagulation complications characteristic of COVID-19, discusses genetic predispositions that aggravate the course of the post-COVID period, as well as the effectiveness of estrogens in protecting the vascular endothelium and increasing the number of CD4+ T cells, providing an adequate immune response when infected with SARS-CoV-2. Numerous studies show that the complications characteristic of the severe course of COVID-19 are multifactorial in nature and cannot be unambiguously explained only by genetic predisposition. However, with the development of personalized medicine, special attention should be paid to the study of genetic aspects that can equally contribute to the occurrence of menopausal disorders in healthy women and aggravate the course of the post-pregnancy period. The data presented allow us to conclude that in the context of the ongoing COVID-19 pandemic at the population level, MHT can bring significant benefits to women during menopause due to the beneficial effect of estrogens on vascular walls. Additional study of the relationship between the course of the postcovid period in MHT users and polymorphisms of candidate genes that determine the risks of thrombotic complications and metabolic consequences is required.

Exploring the relationship between vitamin D and leptin hormones in type 2 diabetes mellitus patients from Kuwait

BACKGROUND

Type 2 diabetes mellitus (T2DM) and obesity are prevalent in Kuwait. Vitamin D (VD) deficiency and leptin resistance are risk factors for both disorders. A correlation between the two risk factors has been suggested albeit inconsistently reported. Our objective was to determine the effect and association of VD and leptin levels and their related common variants with T2DM.

METHODS

This case-control study included 203 Kuwaiti T2DM patients and 162 healthy Kuwaiti controls. Leptin and VD levels were measured using enzyme linked immunosorbent assays. Genotyping of LEP rs7799039, LEPR rs1137101, VDR rs2228570 and rs731236 was performed using Taqman genotyping assays.

RESULTS

Leptin levels were higher in T2DM patients than controls, but vitamin D levels did not differ. No correlation was found between the levels of the two hormones. VDR rs731236G associated with T2DM risk (Odds ratio 1.66, p=0.0008). VDR haplotype analysis revealed GG/AA, GA/AA or GG/AG to associate with T2DM risk (p=0.01) and increased risk of diabetic neuropathy (p=0.002). VDR rs2228570GG associated with leptin levels in T2DM (p=0.01). Effect of LEP rs7799039 on leptin (p=0.01) and VD levels (p=0.02) was only evident in healthy controls.

CONCLUSIONS

VDR rs731236G is associated with T2DM risk in Kuwait, and a VDR haplotype of a less active, low expressing VDR is associated with T2DM and diabetic neuropathy risk. Common variants in leptin and VD related genes appear to mediate the suggested positive correlation of both hormones however their influence is disrupted in T2DM.

Metabolic impact of the VDR rs1544410 in diabetic retinopathy

Aims

To investigate the association between BsmI and DM2 in patients with and without DR and to correlate with clinical parameters in a population in northeastern Brazil.

Methods

Cross-sectional case-control study in which data were collected from 285 individuals, including 128 patients with DM2 and 157 with DR. Clinical, biochemical and anthropometric parameters were analyzed, in addition to the single nucleotide polymorphism (SNP) BsmI of the VDR gene (rs1544410), genotyped by PCR-RFLP.

Results

In the DR group we found a greater number of patients using insulin therapy (p = 0.000) and with longer duration of DM2 (p = 0.000), in addition to higher serum creatinine values (p = 0.001). Higher fasting glucose levels and higher frequency of insulinoterapy were independently observed in patients with DR and b allele carriers, when compared to BB.

Conclusion

The association of the bb/Bb genotypes (rs1544410) of the VDR gene with increased blood glucose levels and insulinoterapy may represent worse glicemic control in rs1544410 b allele carriers in DR Latin American individuals.