Vitamin D in Type 2 Diabetes: Genetic Susceptibility and the Response to Supplementation

Multiple Reaction Monitoring-Mass Spectrometric Immunoassay Analysis of Parathyroid Hormone Fragments with Vitamin D Deficiency in Patients with Diabetes Mellitus

Current immunoassay techniques for analyzing clinically relevant parathyroid hormone (PTH) circulating fragments cannot distinguish microheterogeneity among structurally similar molecular species. This hinders the identification of molecular species and the capture of target analyte information. Since structural modifications are important in disease pathways, mass spectrometry can detect, identify, and quantify heterogeneous ligands captured by antibodies. We aimed to create a sensitive and selective multiple reaction monitoring-mass spectrometric immunoassay analysis (MRM-MSIA)-based method for detecting and quantifying PTH fragments or proteoforms for clinical research. Our study established MRM transitions using triple-quadrupole tandem mass spectrometry for the signature peptides of five PTH fragments. This method was validated according to FDA guidelines, employing the mass spectrometric immunoassay (MSIA) protocol to bolster detection selectivity and sensitivity. This validated approach was applied by analyzing samples from type 2 diabetes mellitus (T2DM) patients with and without vitamin D deficiency. We found serum PTH fragments associated with vitamin D deficiency in patients with and without T2DM. We developed and validated the MRM-MSIA technique specifically designed for the detection and quantification (amino acid (aa38-44), (aa45-51), and (aa65-75)) of these fragments associated with vitamin D deficiency and T2DM. This study is the first to accurately quantify plasma PTH fragments using MRM-MSIA, demonstrating its potential for clinical diagnostics.

The Impact of Vitamin D Deficiency and Insufficiency on the Outcome of Type 2 Diabetes Mellitus Patients: A Systematic Review

Vitamin D deficiency and insufficiency are public health concerns that have contributed to multiple negative health outcomes. Recent studies have revealed that vitamin D deficiency and insufficiency influence glycaemic control and the development of diabetes complications. The goal of this systematic review is to summarise the latest evidence on the impact of vitamin D deficiency and insufficiency on the outcome of Type 2 Diabetes Mellitus (T2DM) patients. In this PRISMA-guided systematic review, articles were sourced from three databases, namely, PubMed, Scopus, and Web of Science. The review only included literature published from 2012 until 2022, and 33 eligible studies met the inclusion criteria for this review. The included articles were critically appraised using the Mixed Method Appraisal Tool (MMAT). According to our findings, vitamin D deficiency or insufficiency is associated with mental health status, macrovascular and microvascular complications of T2DM, metabolic syndrome, increased risk of obesity, increased blood pressure, dyslipidaemia, glycaemic control, nerve-related disease, musculoskeletal-related complications, and reduced quality of life. Due to the diverse implications of vitamin D deficiency and insufficiency, screening for vitamin D levels in T2DM patients may be beneficial.

Association of CYP2R1 and CYP27B1 genes with the risk of obesity and vitamin D metabolism in Saudi women

BACKGROUND

Epigenome, genetic variants, and other environmental factors involved in gene regulation are highly inter-dependent in several chronic diseases, including obesity, cardiovascular disease, and diabetes. The present study aimed at testing the associations and the mechanism involved in silencing of CYP2R1 gene in normal and obese Saudi women patients. Height, weight, BMI, 25-hydroxy vitamin D, parathyroid hormone, glycemic status, and lipid profile (TG, LDL, HDL, and TC) of CYP2R1 were measured in 100 women (31 normal and 69 obese patients).

RESULTS

Our result shows that hypermethylation in site 2 of the CYP2R1 gene with body weight (p < 0.004), BMI (p < 0.002), waist circumference (p < 0.002), total-LDL (p < 0.027), total cholesterol (p < 0.022), and vitamin D (VD) (close to borderline significance p < 0.06) and site 4 of CYP2R1 with LDL (p < 0.041) in the four tested sites among normal and obese women was significantly associated. Moreover, we tested five different CpG sites in the CYP27B1 gene where site 5 correlated significantly with VD levels.

CONCLUSION

Our present study clearly indicates that hypermethylation of specific sites in the CYP2R1 and CYP27B1 genes might regulate gene expression with special reference to the risk of obesity and vitamin D metabolism.

Lack of association between CYP27B1 gene polymorphism and type 2 diabetes mellitus in Iranian patients

Purpose

Type 2 diabetes mellitus (T2DM) is a global health problem with multiple etiological factors. Previous studies indicated that 1- alpha, 25-dihydroxyvitamin D3, a molecule that is produced by CYP27B1, could protect insulin-secreted cells from destruction by immune cells. The aim of the study was to investigate the CYP27B1 promoter gene polymorphism in T2DM.

Methods

Two hundred subjects including 100 T2DM and 100 healthy individuals were recruited in the study. ARMS-PCR technique was used to identify rs10877012 genotypes in the 5' region of CYP27B1.

Results

The frequency of CC, CA, and AA genotype was 61/50, 31/39, and 8/11, respectively in T2DM patients compared to healthy subjects. There was no significant difference between both groups in regarding to genotype and allele distribution (P > 0.05). CA (RR = 1.535, 95% CI = 0.841- 2.802) and AA (1.677, 95% CI = 0.627-4.490) genotypes had no association with increased risk of T2DM. In addition, CA + AA versus CC showed no increased risk for T2DM (RR = 0.639, 95% CI = 0.365-1.121).

Conclusion

We found no association between rs10877012 polymorphism and T2DM. There was no increased risk of this polymorphism in T2DM. Further studies with large groups are suggested in other populations to better understand the relation of CYP27B1 gene variation, especially its ethnicity-dependent relation with T2DM.

rs7041 and rs4588 Polymorphisms in Vitamin D Binding Protein Gene (VDBP) and the Risk of Diseases

The purpose of the study was to investigate the role of vitamin D binding protein (VDBP, DBP) and its polymorphism in the vitamin D pathway and human health. This narrative review shows the latest literature on the most popular diseases that have previously been linked to VDBP. Vitamin D plays a crucial role in human metabolism, controlling phosphorus and calcium homeostasis. Vitamin D binding protein bonds vitamin D and its metabolites and transports them to target tissues. The most common polymorphisms in the VDBP gene are rs4588 and rs7041, which are located in exon 11 in domain III of the VDBP gene. rs4588 and rs7041 may be correlated with differences not only in vitamin D status in serum but also with vitamin D metabolites. This review supports the role of single nucleotide polymorphisms (SNPs) in the VDBP gene and presents the latest data showing correlations between VDBP variants with important human diseases such as obesity, diabetes mellitus, tuberculosis, chronic obstructive pulmonary disease, and others. In this review, we aim to systematize the knowledge regarding the occurrence of diseases and their relationship with vitamin D deficiencies, which may be caused by polymorphisms in the VDBP gene. Further research is required on the possible influence of SNPs, modifications in the structure of the binding protein, and their influence on the organism. It is also important to mention that most studies do not have a specific time of year to measure accurate vitamin D metabolite levels, which can be misleading in conclusions due to the seasonal nature of vitamin D.