The inhibitory effect of vitamin D on myocardial homocysteine levels involves activation of Nrf2-mediated methionine synthase

Vitamin D as a modulator of molecular pathways involved in CVDs: Evidence from preclinical studies

Vitamin D deficiency (VDD) is a widespread global health issue, affecting nearly a billion individuals worldwide, and mounting evidence links it to an increased risk of cardiovascular diseases like hypertension, atherosclerosis, and heart failure. The discovery of vitamin D receptors and metabolizing enzymes in cardiac and vascular cells, coupled with experimental studies, underscores the complex relationship between vitamin D and cardiovascular health. This review aims to synthesize and critically evaluate the preclinical evidence elucidating the role of vitamin D in cardiovascular health. We examined diverse preclinical in vitro (cardiomyocyte cell line) models and in vivo models, including knockout mice, diet-induced deficiency, and disease-specific animal models (hypertension, hypertrophy and myocardial infarction). These studies reveal that vitamin D modulates vascular tone, and prevents fibrosis and hypertrophy through effects on major signal transduction pathways (NF-kB, Nrf2, PI3K/AKT/mTOR, Calcineurin/NFAT, TGF-β/Smad, AMPK) and influences epigenetic mechanisms governing inflammation, oxidative stress, and pathological remodeling. In vitro studies elucidate vitamin D's capacity to promote cardiomyocyte differentiation and inhibit pathological remodeling. In vivo studies further uncovered detrimental cardiac effects of VDD, while supplementation with vitamin D in cardiovascular disease (CVD) models demonstrated its protective effects by decreasing inflammation, attenuating hypertrophy, reduction in plaque formation, and improving cardiac function. Hence, this comprehensive review emphasizes the critical role of vitamin D in cardiovascular health and its potential as a preventive/therapeutic strategy in CVDs. However, further research is needed to translate these findings into clinical applications as there are discrepancies between preclinical and clinical studies.

The impact of homocysteine on patients with diabetic nephropathy: a mendelian randomization study

BACKGROUND/AIMS

Homocysteine (Hcy) has been associated with an increased risk of diabetic nephropathy (DN) in patients, but there is still controversy. This study aims to investigate the causal relationship between plasma Hcy and DN.

METHODS

A Mendelian randomization (MR) study using data from 2 samples was employed to infer causal relationships. The aggregated genetic data associated with Hcy was derived from the largest genome-wide association study (GWAS) to date, involving 44,147 individuals of European ancestry.Data on SNP-diabetic nephropathy, creatinine, and urea nitrogen were obtained from the IEU GWAS database. The analysis method employed a fixed-effect or random-effect inverse variance-weighted approach to estimate effects.Additional analysis methods were used to assess stability and sensitivity. The potential for pleiotropy was evaluated using the MR-Egger intercept test.

RESULTS

Using 12 SNPs as instrumental variables, two-sample MR analysis revealed no evidence of a causal relationship between genetically predicted plasma Hcy levels and diabetic nephropathy, as well as creatinine and blood urea nitrogen levels. This finding is consistent with the results obtained from other testing methods.

CONCLUSIONS

Two-sample Mendelian Randomization analysis found no evidence of a causal relationship between plasma homocysteine levels and diabetic nephropathy, creatinine, or urea.

The improvement of homocysteine-induced myocardial inflammation by vitamin D depends on activation of NFE2L2 mediated MTHFR

OBJECTIVES

Myocardial inflammation underlies a broad spectrum of conditions that cause damage to the myocardium and lead to structural and functional defects. Homocysteine (Hcy) is closely related to the occurrence and development of cardiovascular diseases. We investigated the mechanism underlying the effects of vitamin D as a prophylactic treatment for Hcy-induced cardiac inflammation.

METHODS

The levels of 25(OH)D3 and Hcy were assessed using ELISA kits. Expression levels of the vitamin D receptor (VDR), NFE2 like bZIP transcription factor 2 (NFE2L2), methylenetetrahydrofolate reductase (MTHFR) and inflammatory factors were examined by Western blotting, immunohistochemistry and real time polymerase chain reaction. NFE2L2/MTHFR-knockdown HL-1 cells and NFE2L2+/- mouse were used to test the effects of vitamin D.

RESULTS

We found the levels of Hcy in the serum and myocardial tissue of mice in the Hcy + CCE group were lower than in the Hcy groups, which was opposed to the trend exhibited by the serum 25(OH)D3 level of mice. The mRNA and protein expression levels of the inflammatory factors in cardiac tissues and cardiomyocytes were strongly decreased by the Hcy treatment, compared to the Hcy + CCE/Hcy + 1,25(OH)2D3 groups. Moreover, the results revealed that the level of nuclear NFE2L2 in Hcy + CCE/Hcy + 1,25(OH)2D3 group was increased compared to Hcy group with a reciprocal decrease in the level of cytosolic NFE2L2 in vivo and in vitro. Similarly, the MTHFR mRNA and protein expression in the Hcy + CCE group was higher than the Hcy group. We determined that NFE2L2 promoted the expression of MTHFR. However, based on Hcy treatment, the combination of 1,25(OH)2D3 and MTHFR-/- reversed the decline in IL-6 and TNFα expression caused by 1,25(OH)2D3 alone. Chromatin immunoprecipitation and luciferase reporter assays showed the up-regulation effect of VDR on NFE2L2 and NFE2L2 on MTHFR.

CONCLUSIONS

Our findings indicate that vitamin D/VDR could improve Hcy-induced myocardial inflammation through activation of NFE2L2 mediated MTHFR.