Vitamin D, Cellular Senescence and Chronic Kidney Diseases: What Is Missing in the Equation?

Neurotoxicity of manganese via ferroptosis induced by redox imbalance and iron overload

Manganese (Mn) is an essential trace element for maintaining bodily functions. Excessive exposure to Mn can pose serious health risks to humans and animals, particularly to the nervous system. While Mn has been implicated as a neurotoxin, the exact mechanism of its toxicity remains unclear. Ferroptosis is a form of programmed cell death that results from iron-dependent lipid peroxidation. It plays a role in various physiological and pathological cellular processes and may be closely related to Mn-induced neurotoxicity. However, the mechanism of ferroptosis in Mn-induced neurotoxicity has not been thoroughly investigated. Therefore, this study aims to investigate the role and mechanism of ferroptosis in Mn-induced neurotoxicity. Using bioinformatics, we identified significant changes in genes associated with ferroptosis in Mn-exposed animal and cellular models. We then evaluated the role of ferroptosis in Mn-induced neurotoxicity at both the animal and cellular levels. Our findings suggest that Mn exposure causes weight loss and nervous system damage in mice. In vitro and in vivo experiments have shown that exposure to Mn increases malondialdehyde, reactive oxygen species, and ferrous iron, while decreasing glutathione and adenosine triphosphate. These findings suggest that Mn exposure leads to a significant increase in lipid peroxidation and disrupts iron metabolism, resulting in oxidative stress injury and ferroptosis. Furthermore, we assessed the expression levels of proteins and mRNAs related to ferroptosis, confirming its significant involvement in Mn-induced neurotoxicity.

Associations of serum 25-hydroxyvitamin D and vitamin D receptor polymorphisms with risks of cardiovascular disease and mortality among patients with chronic kidney disease: a prospective study

BACKGROUND

Evidence regarding the relationships of serum 25-hydroxyvitamin D [25(OH)D] with cardiovascular diseases (CVD) and mortality among patients with chronic kidney disease (CKD) is limited and inconsistent.

OBJECTIVES

This study aimed to investigate the associations between serum 25(OH)D and CVD incidence and mortality among patients with CKD.

METHODS

This prospective study included 21,507 participants with CKD and free of CVD in the UK Biobank. Incidences of total and subtypes of CVD and mortality were ascertained via electronic health records. Cox proportional hazard regression models were used to estimate the hazard ratios (HRs) and 95% confidential intervals (CIs) for CVD incidence and mortality.

RESULTS

The median serum 25(OH)D concentration was 44.0 nmol/L (interquartile range: 30.1, 60.6 nmol/L). After multivariable adjustment, compared with CKD patients with serum 25(OH)D concentrations of <25 nmol/L, those with serum 25(OH)D ≥75 nmol/L had HRs (95% CIs) of 0.80 (0.71, 0.90) for total CVD incidence, 0.82 (0.69, 0.97) for ischemic heart disease, 0.56 (0.41, 0.77) for stroke, 0.64 (0.46, 0.88) for myocardial infarction, 0.62 (0.49, 0.80) for heart failure, 0.60 (0.43, 0.85) for CVD mortality, and 0.62 (0.52, 0.74) for all-cause mortality. In addition, these associations were not modified by vitamin D receptor polymorphisms, with no significant interaction detected.

CONCLUSIONS

Higher serum 25(OH)D concentrations were significantly associated with lower risks of total and subtypes of CVD incidence and mortality among individuals with CKD. These findings highlight the importance of maintaining adequate vitamin D status in the prevention of CVD and mortality in patients with CKD.

From the Sun to the Cell: Examining Obesity through the Lens of Vitamin D and Inflammation

Obesity affects more than one billion people worldwide and often leads to cardiometabolic chronic comorbidities. It induces senescence-related alterations in adipose tissue, and senescence is closely linked to obesity. Fully elucidating the pathways through which vitamin D exerts anti-inflammatory effects may improve our understanding of local adipose tissue inflammation and the pathogenesis of metabolic disorders. In this narrative review, we compiled and analyzed the literature from diverse academic sources, focusing on recent developments to provide a comprehensive overview of the effect of vitamin D on inflammation associated with obesity and senescence. The article reveals that the activation of the NF-κB (nuclear factor kappa B subunit 1) and NLRP3 inflammasome (nucleotide-binding domain, leucine-rich-containing, pyrin domain-containing-3) pathways through the toll-like receptors, which increases oxidative stress and cytokine release, is a common mechanism underlying inflammation associated with obesity and senescence, and it discusses the potential beneficial effect of vitamin D in alleviating the development of subclinical inflammation. Investigating the main target cells and pathways of vitamin D action in adipose tissue could help uncover complex mechanisms of obesity and cellular senescence. This review summarizes significant findings related to opportunities for improving metabolic health.

Vitamin D Improves Cognitive Impairment and Alleviates Ferroptosis via the Nrf2 Signaling Pathway in Aging Mice

Ferroptosis is an iron-dependent mode of cell death associated with the occurrence and development of age-related neurodegenerative diseases. Currently, there are no effective drugs available to prevent or treat these aging-related neurodegenerative diseases. Vitamin D (VD) is an antioxidant and immunomodulator, but its relationship with ferroptosis in aging-related neurodegenerative diseases has not been extensively studied. In this study, we aimed to investigate the role of VD in learning and memory in aging mice. To examine whether VD protects aging hippocampal neurons, we used physiologically active 1,25(OH)2D3. We established aging models in vivo (C57BL/6 mice) and in vitro (HT22 cells) using D-galactose (D-gal). The results demonstrated that VD could improve learning and memory in mice aged via the use of D-gal, and it reduced damage to hippocampal neurons. VD could regulate ferroptosis-related proteins (increasing GPX4 expression and decreasing ACSL4 and ALOX15 protein expression levels), increasing GSH levels, reducing MDA and intracellular and mitochondrial ROS levels, as well as total iron and Fe2+ levels, and improving mitochondrial morphology, thereby alleviating ferroptosis in aging hippocampal neurons. Additionally, VD activated the VDR/Nrf2/HO-1 signaling pathway, thereby inhibiting ferroptosis. Notably, when the VDR was knocked down, VD lost its ability to activate Nrf2. Consequently, inhibiting Nrf2 decreased the protective effect of VD against ferroptosis in aged hippocampal neurons. In summary, VD activates the Nrf2/HO-1 signaling pathway through the VDR, effectively preventing ferroptosis induced by aging in hippocampal neurons.