Variability in genes regulating vitamin D metabolism is associated with vitamin D levels in type 2 diabetes

Association Among Vitamin D Receptor Gene Polymorphisms, Metabolic Control, and Inflammatory Markers in Type 2 Diabetes: A Systematic Review and Meta-Analysis

CONTEXT

Single-nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) contribute to inadequate metabolic profiles in individuals with type 2 diabetes mellitus (T2DM).

OBJECTIVE

We sought to elucidate the relationship among SNPs in the VDR and markers for glycemic control, lipid profile, and inflammation in individuals with T2DM.

DATA SOURCES

We performed a systematic search in the MEDLINE (via PubMed), EMBASE, and SCOPUS databases in July 2021 and updated the search in October 2023.

DATA EXTRACTION

6 observational studies were selected from the databases, and 1 study was included after checking the reference list. Two authors independently completed the selection and data extraction of studies and population characteristics, the prevalence of SNPs in the VDR, genotyping methods, and laboratory findings, and performed summary statistics of the results.

DATA ANALYSIS

The meta-analyses were performed on 5 studies including 1198 adults with T2DM. The duration of the diabetes diagnosis ranged from 5.0 to 14.7 years. A random-effects model was used to pool the results using a 2-tailed (P < .05). Effect sizes were reported as standardized mean differences (SMDs) and 95% confidence intervals (CIs). Four SNPs in the VDR were identified (Fokl, BsmI, Taql, and Apal) by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The Fokl SNP was identified in 5 studies and associated with a higher percentage of glycated hemoglobin (HbA1c%) (SMD,  0.41 [95% CI, 0.15-0.67]). The Bsml in 4 studies was associated with higher triacylglycerol (SMD, 0.21 [95% CI, 0.03-0.38]). The Taql SNP was identified in 2 studies and did not show any associations, and the Apal SNP was identified in only 1 study and was not analysed in the meta-analysis.

CONCLUSIONS

Although the studies identified 4 SNPs in the VDR, the results of the meta-analysis allowed us to infer only the association of the SNPs Fokl and Bsml with increased %HbA1c and triacylglycerol levels, respectively, in individuals with T2DM.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42021268152.

Exploring the interplay between DHCR7, vitamin D deficiency, and type 2 diabetes mellitus (T2DM): a systematic review

Type 2 diabetes mellitus (T2DM) is a growing global health concern. The pathogenesis of T2DM is multifactorial and intricate, involving a complex interplay of genetic predisposition, environmental factors, and molecular interactions. Vitamin D (circulating 25-hydroxyvitamin D concentration) regulates factors crucial for T2DM, including insulin secretion, sensitivity, and inflammation. Thus, vitamin D deficiency has been linked to poor health outcomes in T2DM patients. The cholesterol-synthesizing enzyme 7-dehydrocholesterol reductase (DHCR7) represents a critical regulatory switch between cholesterol and vitamin D3 synthesis. Recent findings suggest that the enzyme DHCR7 may indicate T2DM glycolipid metabolic disorder and is associated with deficient circulating vitamin D (circulating 25-hydroxyvitamin D concentration) status. In this PRISMA-guided systematic review, articles were sourced from two databases, namely, PubMed and Cochrane Library, to evaluate the impact of vitamin D deficiency in patients with T2DM and to explore the emerging role of DHCR7 in T2DM pathogenesis. Our findings strongly indicate a positive correlation between deficient vitamin D status and poor health outcomes in T2DM patients. Finally, this systematic review presents a novel perspective on T2DM development, focusing on the interplay between T2DM-associated hyperglycemia, expression of DHCR7, and abrogation of vitamin D synthesis.

Association between circulating micronutrient pattern, glycemic control, and insulin resistance in type 2 diabetes mellitus

The circulating micronutrient pattern in type 2 diabetes mellitus (T2DM) may impact glycemic control and insulin resistance; however, there is a scarcity of studies that have evaluated the circulating micronutrient pattern in the T2DM population. Therefore, our objective was to identify circulating micronutrient pattern and their association with markers of glycemic control and insulin resistance in individuals with T2DM. We developed a cross-sectional observational study involving adults with T2DM in Sergipe, Brazil. We assessed plasma levels of magnesium, zinc, calcium, potassium, and serum 25-hydroxyvitamin D. Additionally, also measured fasting glucose levels, the percentage of glycated hemoglobin (%HbA1c), and calculated the homeostatic model assessment for insulin resistance (HOMA-IR). Patterns of body reserve were established using principal component analysis and categorized into quartiles. Binary logistic regression models were employed. We evaluated 114 individuals (63.7% women), with a median age and body mass index of 49 years and 29.6 kg/m², respectively. Two circulating micronutrient patterns were identified, explaining 62.5% of the variance: Pattern 1 (positive contributions from magnesium, zinc, calcium, and potassium) and Pattern 2 (positive contributions from 25-hydroxyvitamin D and zinc, with a negative contribution from potassium). Lowest quartile for Pattern 1 and Pattern 2 exhibiting a 4.32-fold (p = 0.019) and 3.97-fold (p = 0.038) higher likelihood of increasing HOMA-IR and %HbA1c values, respectively, compared to the larger quartiles. However, no associations were found between these patterns and fasting glucose values. Lowest quartile for both patterns of micronutrients was associated with inadequate metabolic control in individuals with T2DM.

Effect of Cytochrome P450 Family 2 Subfamily R Member 1 Variants on the Predisposition of Coronary Heart Disease in the Chinese Han Population

Propose: Cytochrome P450 family 2 subfamily R member 1 (CYP2R1) variations can affect the activity of 25-hydroxylase, resulting in the deficiency of 25(OH)D, which leads to an increased incidence and mortality of coronary heart disease (CHD). The purpose is to assess the influence of CYP2R1 variants on CHD risk among the Chinese Han population.

Methods: A total of 508 CHD patients and 510 healthy controls were enrolled. The MassARRAY platform completed genotyping of CYP2R1 variants. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated using logistic regression analysis.

Results: Rs6486205 (OR = 1.25, 95% CI: 1.05–1.50, p = 0.014), rs10741657 (OR = 1.29, 95% CI: 1.08–1.54, p = 0.005), and rs2060793 (OR = 1.27, 95% CI: 1.06–1.51, p = 0.009) were associated with the increased susceptibility to CHD in the whole subjects. Interestingly, the relationships between these variants and CHD risk were observed in the subjects with age >60 years, males or non-smoker. Additionally, the haplotypes A_rs10741657A_rs2060793 and G_rs10741657G_rs2060793 had the higher risk of CHD, and the combination (rs6486205 and rs10741657) was the best multi-locus model.

Conclusion: Our study suggested the contribution of CYP2R1 polymorphisms to the increased CHD predisposition in the Chinese Han population. Furthermore, the risk association was related to confounding factors for CHD, including age, sex, and smoking. These findings might help to strengthen the understanding of the CYP2R1 gene in the occurrence of CHD.

Vitamin D pathway-related gene polymorphisms and their association with metabolic diseases: A literature review

PURPOSE

Given that the relationship between vitamin D status and metabolic diseases such as obesity and type 2 diabetes (T2D) remains unclear, this review will focus on the genetic associations, which are less prone to confounding, between vitamin D-related single nucleotide polymorphisms (SNPs) and metabolic diseases.

METHODS

A literature search of relevant articles was performed on PubMed up to December 2019. Those articles that had examined the association of vitamin D-related SNPs with obesity and/or T2D were included. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data. In total, 73 articles were included in this review.

RESULTS

There is a lack of research focusing on the association of vitamin D synthesis-related genes with obesity and T2D; however, the limited available research, although inconsistent, is suggestive of a protective effect on T2D risk. While there are several studies that investigated the vitamin D metabolism-related SNPs, the research focusing on vitamin D activation, catabolism and transport genes is limited. Studies on CYP27B1, CYP24A1 and GC genes demonstrated a lack of association with obesity and T2D in Europeans; however, significant associations with T2D were found in South Asians. VDR gene SNPs have been extensively researched; in particular, the focus has been mainly on BsmI (rs1544410), TaqI (rs731236), ApaI (rs7975232) and FokI (rs2228570) SNPs. Even though the association between VDR SNPs and metabolic diseases remain inconsistent, some positive associations showing potential effects on obesity and T2D in specific ethnic groups were identified.

CONCLUSIONS

Overall, this literature review suggests that ethnic-specific genetic associations are involved. Further research utilizing large studies is necessary to better understand these ethnic-specific genetic associations between vitamin D deficiency and metabolic diseases.

Clinical features of vitamin D deficiency in children: A retrospective analysis

Vitamin D is very important for children's health. Previous studies have shown that vitamin D deficiency leads to a series of diseases in adults. However, pediatricians are mostly aware of rickets caused by vitamin D deficiency in children and poorly aware of other symptoms. This study aimed to retrospectively analyze the different clinical features of vitamin D deficiency to enhance identification by pediatricians, thus minimizing misdiagnosis. In this study, we retrospectively analyzed the clinical features of vitamin D deficiency in 268 children aged 0-14 years from June 2016 to May 2018 in the Third Affiliated Hospital of Zhengzhou University. Serum 25-hydroxy vitamin D [25(OH)D] levels were determined using the chemiluminescence method. Of the 268 cases, 101 cases showed movement disorder (37.7%) and 167 nervous system abnormalities (62.3%). Among all cases, 6 were misdiagnosed as febrile seizures (2.23%), 5 as epilepsy (1.86%), 2 as Tourette syndrome (0.74%), and 2 as developmental retardation (0.74%). There were significant differences in patients with clinical characteristics of movement disorder and nervous system abnormalities partly between Pre-and post-vitamin D treatment. This analysis revealed that vitamin D deficiency occurs not only in children but also in adolescents, with diverse clinical features. Therefore, pediatricians should pay more attention to clinical different signs and symptoms, and future studies should be conducted to confirm the mechanisms of these processes.

Prevalence of vitamin D deficiency in women from southern Brazil and association with vitamin D-binding protein levels and GC-DBP gene polymorphisms

Vitamin D deficiency is highly prevalent worldwide, and vitamin D-binding protein (DBP) a major regulator of serum vitamin D levels. The rs4588 and rs7041 polymorphisms of the GC gene constitute the genetic basis of the three major isoforms of circulating DBP (GC1s, GC1f, and GC2), while the rs2282679 variant is located in an important regulatory region of the GC gene. The aim of this study was to assess the prevalence of 25-hydroxyvitamin D [25(OH)D] deficiency and to ascertain whether it is associated with DBP levels and with GC gene variants. Biorepository samples of 443 women aged 20 to 72 years, with no evidence of clinical disease, were analyzed. Circulating levels of 25(OH)D were considered sufficient if ≥20 ng/mL and deficient if <20 ng/mL. Genotype analysis was performed by RT-PCR. Mean age was 53.4±9.4 years; mean BMI was 27.8±5.8 kg/m2. The overall sample had mean 25(OH)D levels of 22.8±8.3 ng/mL; 39.7% of participants had deficient circulating 25(OH)D levels. Higher prevalence ratios (PR) of 25(OH)D deficiency were found for the CC genotype of rs2282679 (PR 1.74; 95%CI 1.30 to 2.24; p<0.001), GC2 isoform (PR 1.66; 95%CI 1.17 to 2.38; p = 0.005), time since menopause (PR 1.02; 95%CI 1.003 to 1.03, p = 0.016), and HOMA-IR (PR 1.02; 95%CI 1.01 to 1.03, p = 0.004). DBP levels (per 30 μg/mL increase in DBP) were associated with lower PR for 25(OH)D deficiency (PR 0.89; 95%CI 0.80;0.99; p = 0.027). Except for HOMA-IR, these prevalence ratios remained significant after adjustment for age and BMI. In conclusion, the rs2282679 polymorphism and the GC2 isoform of DBP were associated with lower serum DBP levels and with susceptibility to 25(OH)D deficiency in Brazilian women with no evidence of clinical disease.