Lower Vitamin D Levels, but Not VDR Polymorphisms, Influence Type 2 Diabetes Mellitus in Brazilian Population Independently of Obesity

Association analysis between the VDR gene variants and type 2 diabetes

Background

Type 2 diabetes mellitus (T2DM) is recognized as a complex metabolic which has affected the lives of millions of people around the world. Vitamin D receptor (VDR) gene polymorphisms have been suggested to be a vital contributor to the development of T2DM. However, the association between VDR gene polymorphisms and T2DM remains controversial. We have investigated the association between two VDR gene polymorphisms (rs731236 and rs1544410) and T2DM in an Iranian population.

Methods

A total of 148 T2DM patients and 100 normal controls were recruited in this study. We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis to perform genotyping.

Results

The results of the present research revealed that the frequency of the rs731236 C allele was significantly higher in T2DM patients than in normal controls (p = 0.044). The CC genotype of rs731236 was connected with an increased risk of T2DM (OR = 2.85, 95% CI = 1.06-7.69, p = 0.039). However, no significant difference in the frequency of the rs1544410 C allele between T2DM patients and normal controls was observed (p = 0.918).

Conclusion

Our findings were suggestive of the rs731236 polymorphism of the VDR as a risk factor for developing T2DM in the Iranian population, while rs1544410 polymorphism may not be associated with T2DM susceptibility. Further research is needed to approve these findings in other populations and to clarify the underlying mechanisms involved in such an association.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01323-0.

Bariatric Surgery and Vitamin D: Trends in Older Women and Association with Clinical Features and VDR Gene Polymorphisms

(1) Background: Obesity and its comorbidities can cause burdens and limitations. Bariatric surgery (BS) is indicated as a safe procedure to reduce body mass and improve present comorbidities. However, several complications were reported, such as vitamin D [25(OH)D] deficiency. We evaluated if 25(OH)D serum levels relate to clinical characteristics, symptoms, or habits in women after their BS, and whether the vitamin D receptor (VDR) gene's TaqI and FokI polymorphisms affected 25(OH)D levels and the total body bone mineral density (TBBMD). (2) Methods: This cohort cross-sectional comparative analytical prospective study consisted of 27 women, 61.6 ± 5.0 years, submitted to BS one year prior at a public reference hospital, DF-Brazil. All participants were asked to follow the physical and dietary activity recommendations and received vitamin D3 supplements. Their anthropometric, biochemical, and immunological measurements and blood samples were obtained. (3) Results: 73.3% of participants had low 25(OH)D levels, and their levels correlated positively with TBBMD and negatively with systolic pressure. VDR TaqI did not affect 25(OH)D levels, whereas VDR FokI's allele f presence correlated to a median rise in 25(OH)D levels. Neither polymorphism correlated to TBBMD. (4) Conclusions: 25(OH)D levels were positively correlated with TBBMD, negatively with systolic blood pressure, and were higher in those with the VDR FokI allele f.

Study on the relationship between vitamin D level and macrophage typing in patients with type 2 diabetes mellitus

Objective

Population studies have shown that vitamin D (VitD) deficiency is associated with an increased incidence of type 2 diabetes mellitus (T2DM), VitD deficiency is a potential risk factor for T2DM, and the proportion of M1-type macrophages and M2-type macrophages in T2DM patients is imbalanced. Another study reported that VitD can affect the differentiation of macrophages into M1 and M2 types. However, there is no definitive result about the correlation between plasma VitD levels and macrophage typing in patients with T2DM. Whether VitD affects the progression of T2DM by regulating the polarization type of macrophages and the specific regulatory mechanism is not very clear. Therefore, we carried out the following research.

Methods

We first used flow cytometry to detect the proportions of M1 and M2 macrophages in peripheral blood of T2DM patients with different VitD levels. Furthermore, we used ELISA to detect the inflammatory factors affecting macrophage differentiation in patients’ plasma, including IL-6 secreted by M1-type macrophages and TGF-β secreted by M2-type macrophages. Mononuclear cells were separated from human peripheral blood with immunomagnetic beads, cultured in vitro, and treated with different concentrations of VitD, and the ratio of differentiation into M1 and M2 macrophages was detected by flow cytometry.

Results

With the increase of serum 25(OH)D levels in patients with T2DM, the proportion of M1 and M2 macrophages in peripheral blood decreased, that is, the polarized phenotype of macrophages was more inclined to M2 type, while plasma IL-6 gradually decreased, and TGF-β gradually increased. In addition, VitD can promote the differentiation of CD14-positive monocytes cultured in vitro into M2 macrophages.

Conclusions

When the level of VitD in T2DM patients is low, there are more M1-type macrophages in peripheral blood, and when the level of VitD is increased, M2-type macrophages are increased. Changes in related inflammatory factors were also consistent. In vitro culture of monocytes further confirmed that VitD can promote the differentiation of macrophages to M2 type in T2DM patients.

The Relationship of 25(OH)D3 with Diabetes Mellitus and the Mediation Effect of Lipid Profile in Chinese Rural Population of Henan Province

Background and Objectives: Studies suggest that vitamin D is involved in the development of type 2 diabetes mellitus (T2DM) and influences serum lipids levels, while lipid disorders are also closely related to T2DM. This study attempts to explore the complex relationship of serum 25(OH)D3, serum lipids, and T2DM among Chinese population. Materials and Methods: A cross-sectional study was carried out among 2326 subjects. The chi-square (χ2) test was applied to compare the prevalence of T2DM or dyslipidemia between two serum 25(OH)D3 levels. Linear regression was applied to analyze the correlation between serum lipids and 25(OH)D3 contents. Univariate and logistic analysis were used to explore the relationship between two lipid levels and T2DM. Mediation analysis was used to explore whether serum lipids mediate the relationship between two serum 25(OH)D3 levels and T2DM. Results: Compared to subjects with 25(OH)D3 ≥ 30 ng/mL, subjects with 25(OH)D3 < 30 ng/mL were higher in the prevalence of T2DM. The occurrences of high TG and low HDL-C were significantly higher in vitamin D deficiency and insufficiency than those in vitamin D sufficiency. Serum 25(OH)D3 content showed a reverse correlation with TC, TG, and LDL-C, but positive correlation with HDL-C. The odds ratios (ORs) (95% confidence intervals, 95%CI) of T2DM by comparing TG ≥ 2.26 mmol/L vs. TG < 2.26 mmol/L and HDL-C < 1.04 mmol/L vs. HDL-C ≥ 1.04 mmol/L in all participants were 2.48 (1.94-3.18) and 1.37 (1.07-1.75), respectively. Serum TG or HDL-C level partially mediated the relationship between two 25(OH)D3 level and T2DM. Conclusions: Serum 25(OH)D3 < 30 ng/mL seems to be associated with T2DM or dyslipidemia (high TG and low HDL-C) in our study, but there is still no proof of a cause-effect relationship. Moreover, serum TG or HDL-C level partially mediated the relationship between 25(OH)D3 levels and T2DM.

Effect of Vitamin D Supplementation on Glycemic Control in Prediabetes: A Meta-Analysis

Clinical research results of vitamin D supplementation in the improvement of prediabetes remain controversial. Accordingly, a literature search was conducted of PubMed, Embase (Ovid), and Web of Science prior to 9 November 2021. Randomized controlled studies reported that the following indicators were included: body mass index (BMI), fasting blood glucose (FBG), 2 h oral glucose tolerance test plasma glucose (2h-PG), hemoglobin A1c (HbA1c), insulin resistance by homeostasis model assessment (HOMA-IR), homeostasis model assessment of β-cell function (HOMA-B), and fasting insulin (FINS). Twenty-nine articles (N = 3792) were included in the present meta-analysis. Intriguingly, vitamin D supplementation resulted in a vast improvement in FBG (standardized mean difference (SMD) = -0.38; 95%CI: -0.59, -0.16), HbA1c (SMD = -0.14; 95%CI: -0.22, -0.06) and FINS (SMD = 0.18; 95%CI: -0.26, -0.09), but not in other outcomes. However, preferred changes were observed in subgroups, as follows: Asia (SMD_2h-PG = -0.25, 95%CI: -0.45, -0.04), study duration ≥1 year (SMD_HOMA-IR = -0.44, 95%CI: -0.81, -0.06) (SMD_HOMA-B = 0.34, 95%CI: 0.01, 0.66), baseline 25(OH)D < 50 nmol/L (SMD_2h-PG = -0.23, 95%CI: -0.39, -0.06), and baseline 25(OH)D ≥ 50 nmol/L (SMD_HOMA-IR = -0.50, 95%CI: -0.96, -0.03). In conclusion, oral supplementation of vitamin D has shown better effects in improving FBG, HbA1c, and FINS compared with controls among prediabetics; long-term vitamin D supplementation could have additional effects in participants with vitamin D deficiency for 2h-PG, HOMA-IR, and HOMA-B.

Cardiometabolic risk factors and hypovitaminosis D in adolescents with overweight from a sunny region in northeast Brazil: A cross-sectional study

BACKGROUND

obesity can influence vitamin D levels, which in turn might be associated with cardiometabolic risk factors.

OBJECTIVES

this study assessed the association between 25-hydroxyvitamin D [25(OH)D] levels and cardiometabolic risk factors in adolescents with overweight living in a region of northeastern Brazil.

MATERIAL AND METHODS

a cross-sectional study was carried out by non-probabilistic sampling in adolescents diagnosed with overweight or obesity. The subjects were divided according to their 25(OH)D status into two groups: sufficient vitamin D and hypovitaminosis D. Biodemographic, lifestyle, cardiometabolic, and biochemical factors were evaluated. A logistic regression model was applied to determine the predictors of hypovitaminosis D.

RESULTS

we found a high frequency of hypovitaminosis D (45.6 %) in adolescents. Weekly sun exposure was negatively associated with hypovitaminosis D (OR = 0.96; 95 % CI: 0.92-0.99), while significant positive associations were observed between hypovitaminosis D and blood pressure above the 95th percentile (OR = 4.00; 95 % CI: 1.19-13.37), body weight (OR = 1.04; 95 % CI: 1.01-1.07), and fasting insulin (OR = 1.13; 95 % CI: 1.05-1.22).

CONCLUSION

hypovitaminosis D showed a high prevalence in adolescents with overweight living in a sunny region of northeastern Brazil, and cardiometabolic risk factors such as systemic arterial hypertension, high body weight, and hyperinsulinemia are predictors of hypovitaminosis D.

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

ABSTRACT

Numerous original studies and 4 published meta-analyses have reported the association between the Vitamin D receptor (VDR) BsmI, FokI, ApaI, and TaqI polymorphisms and type 2 diabetes mellitus (T2DM) risk. However, the results were inconsistent. Therefore, an updated meta-analysis was performed to further explore these issues.To further explore the association between the VDR BsmI, FokI, ApaI, and TaqI polymorphisms and T2DM risk.PubMed, EMBASE, Scopus, and Wanfang databases were searched. The following search strategy were used: (VDR OR vitamin D receptor) AND (polymorphism OR variant OR mutation) AND (diabetes OR mellitus OR diabetes mellitus). Pooled crude odds ratios with 95% confidence intervals were applied to evaluate the strength of association in 5 genetic models. Statistical heterogeneity, the test of publication bias, and sensitivity analysis were carried out using the STATA software (Version 12.0). To evaluate the credibility of statistically significant associations, we applied the false-positive report probabilities (FPRP) and Bayesian false discovery probability (BFDP) test.Overall, the VDR BsmI polymorphism was associated with a significantly decreased T2DM risk in Asians; the VDR FokI polymorphism was associated with a significantly decreased T2DM risk in Asians, African countries, and Asian countries; the VDR ApaI polymorphism was associated with a significantly decreased T2DM risk in Caucasians and North American countries.On the VDR ApaI polymorphism, a significantly increased T2DM risk was found in a mixed population. However, when we further performed a sensitivity analysis, FPRP, and BFDP test, less-credible positive results were identified (all FPRP > 0.2 and BFDP > 0.8) in any significant association.In summary, this study strongly indicates that all significant associations were less credible positive results, rather than from true associations.

Vitamin D Receptor gene polymorphisms and susceptibility to type 2 diabetes: evidence from a meta-regression and meta-analysis based on 47 studies

BACKGROUND

Evidence from various studies suggest that vitamin D receptor (VDR) gene polymorphisms are associated with type 2 diabetes (T2D); However, these results have been disputable. Here we conducted a meta-analysis to comprehensively evaluate the effect of VDR gene polymorphisms and susceptibility to T2D.

METHODS

All relevant studies reporting the association between VDR gene polymorphisms and susceptibility to T2D published up to August 2020 were identified by comprehensive systematic database search in web of science, Scopus, and Medline. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to measure strength of association. The methodological quality of each study was assessed according to the Newcastle-Ottawa Scale. Subgroup and meta-regression analysis were also performed.

RESULTS

A total of 47 case-control studies were included in this meta-analysis. The overall population results revealed a significant association between FokI, and BsmI (heterozygote model) polymorphisms and T2D in the overall analysis. However, no association was found with the TaqI and ApaI polymorphisms. Moreover, the pooled results of subgroup analysis by ethnicity suggested significant association between FokI, TaqI, and BsmI polymorphisms and T2D in some subgroups. Meta-regression analyses indicated that none of the publication year, ethnicity, and genotyping method were the source of heterogenicity in all four polymorphisms.

CONCLUSIONS

This meta-analysis suggested a significant association between VDR gene FokI, and BsmI (heterozygote model) polymorphisms and T2D susceptibility in overall population and ethnic-specific analysis.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40200-020-00704-z.

Diminished 25-OH vitamin D3 levels and vitamin D receptor variants are associated with susceptibility to type 2 diabetes with coronary artery diseases

Background

Role of plasma vitamin D and genetic variants of its receptor (VDR) in susceptibility to different diseases has been documented. Various studies in different populations have been highlighted strong associations with diabetes and cardiovascular diseases. Vitamin D deficiency has been linked with the development of type 2 diabetes (T2D) and the onset of coronary artery diseases (CAD). However, the role of vitamin D in predisposition to CAD in patients with T2D is ill‐defined.

Materials and Methods

We enrolled 674 Chinese T2D patients, and based on clinical phenotype, patients were further categorized into patients with (n = 138) or without coronary artery disease (n = 536). Five hundred twenty‐one healthy subjects from similar geographical areas, free from diabetic or coronary disorders, were enrolled as controls. Serum levels of 25‐OH vitamin D were quantified by ELISA. Common VDR (FokI, TaqI, BsmI, and ApaI) polymorphisms were genotyped by polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP).

Results

Patients with T2D displayed lower levels of 25‐OH vitamin D compared with healthy controls. Furthermore, T2D patients with CAD clinical phenotype had the lowest levels of vitamin D. Prevalence of FokI and TaqI mutants was significantly higher in diabetic patients when compared to controls. Interestingly, Tt genotype was more frequent in the artery disease group in comparison with T2D patients without heart involvement. Combined analysis of VDR polymorphisms and serum levels of vitamin D revealed a significant role in predisposition to T2D with or without CAD.

Conclusions

Lower vitamin D levels and variants of VDR polymorphisms (FokI and TaqI) are associated with susceptibility to T2D and clinical manifestation.