Reduced Vitamin D Receptor on Circulating Endothelial Progenitor Cells: A New Risk Factor of Coronary Artery Diseases

Vitamin D Deficiency, Inflammation, and Diminished Endogenous Regenerative Capacity in Coronary Heart Disease

Background

Vitamin D deficiency (VDD) is associated with coronary heart disease (CHD) and poor outcomes, but supplementation does not improve prognosis. VDD has been implicated in and may promote greater risk through inflammation and impaired progenitor cell function.

Objectives

The authors examined VDD, high-sensitivity C-reactive protein (hsCRP), circulating progenitor cell (CPC) counts, and outcomes in patients with CHD. They hypothesized that the higher risk with VDD is mediated by inflammation and impaired regenerative capacity.

Methods

A total of 5,452 individuals with CHD in the Emory Cardiovascular Biobank had measurement of 25-hydroxyvitamin D, subsets of whom had hsCRP measurements and CPCs estimated as CD34-expressing mononuclear cell counts. Findings were validated in an independent cohort. 25-hydroxyvitamin D <20 ng/mL was considered VDD. Cox and Fine-Gray models determined associations between marker levels and: 1) all-cause mortality; 2) cardiovascular mortality; and 3) major adverse cardiovascular events, a composite of adverse CHD outcomes.

Results

VDD (43.6% of individuals) was associated with higher adjusted cardiovascular mortality (HR: 1.57, 95% CI: 1.09-2.28). There were significant interactions between VDD and hsCRP and CPC counts in predicting cardiovascular mortality. Individuals with both VDD and elevated hsCRP had the greatest risk (HR: 2.82, 95% CI: 2.16-3.67). Only individuals with both VDD and low CPC counts were at high risk (HR: 2.25, 95% CI: 1.46-3.46). These findings were reproduced in the validation cohort.

Conclusions

VDD predicts adverse outcomes in CHD. Those with VDD, inflammation and/or diminished regenerative capacity are at a significantly greater risk of cardiovascular mortality. Whether targeted supplementation in these high-risk groups improves risk warrants further study.

Vitamin D Receptor Expression Limits the Angiogenic and Inflammatory Properties of Retinal Endothelial Cells

The integrity of retinal endothelial cell (EC) is essential for establishing and maintaining the retinal blood barrier to ensure proper vision. Vitamin D is a hormone with known protective roles in EC function. The majority of vitamin D action is mediated through the vitamin D receptor (VDR). VDR is a nuclear receptor whose engagement by vitamin D impacts the expression of many genes with important roles in regulation of angiogenesis and inflammation. Although many studies have investigated vitamin D-VDR action in cardiovascular protection and tumor angiogenesis, its impact on retinal EC function and regulation of ocular angiogenesis and inflammation is exceedingly limited. We previously showed calcitriol, the active form of vitamin D, is a potent inhibitor of retinal neovascularization in vivo and retinal EC capillary morphogenesis in vitro. Here, using retinal EC prepared from wild-type (Vdr+/+) and VDR-deficient (Vdr-/-) mice, we show that retinal EC express VDR and its expression is induced by calcitriol. The lack of VDR expression had a significant impact on endothelial cell-cell and cell-matrix interactions. Vdr-/- retinal EC proliferated at a slower rate and were more adherent and less migratory. They also exhibited increased expression levels of inflammatory markers driven in part by sustained activation of STAT1 and NF-κB pathways and were more sensitive to oxidative challenge. These changes were attributed, in part, to down-regulation of endothelial nitric oxide synthetase, enhanced hepcidin expression, and increased intracellular iron levels. Taken together, our results indicate that VDR expression plays a fundamental role in maintaining the proper angiogenic and inflammatory state of retinal EC.

Effects of Early Intensive Insulin Therapy on Endothelial Progenitor Cells in Patients with Newly Diagnosed Type 2 Diabetes

AIM

This study aimed to investigate the alteration of circulating CD34⁺KDR⁺CD133⁺ endothelial progenitor cells (EPCs) in patients with newly diagnosed type 2 diabetes and the mechanism of the effect of early intensive insulin therapy.

METHODS

In this study, 36 patients with newly diagnosed type 2 diabetes and 22 control subjects matched by age and gender were enrolled. All of the patients with diabetes received intensive insulin therapy. The number of EPCs was assessed by flow cytometry based on the expression of CD34, CD133, and kinase insert domain-containing receptor (KDR).

RESULTS

Levels of circulating CD34⁺KDR⁺CD133⁺ EPCs were higher in patients with diabetes compared to control subjects and significantly decreased after intensive insulin therapy. Levels of vascular endothelial growth factor (VEGF), a major contributor to EPC mobilization, were significantly higher in patients with diabetes compared to control subjects, and dramatically decreased after insulin therapy. Importantly, VEGF levels correlated with number of EPCs. Moreover, compared with control subjects, pro-inflammatory cytokines and oxidative stress were significantly higher in patients with diabetes and markedly decreased after intensive insulin therapy.

CONCLUSIONS

These results showed that type 2 diabetes is associated with an increase of circulating CD34⁺KDR⁺CD133⁺ EPCs at the onset of diabetes, indicating increased compensatory mobilization. Additionally, early intensive insulin therapy exerts a preserving effect on EPC level partly through improving inflammation status and oxidative stress, thereby implying a putative long-term beneficial effect on vascular integrity via suspending excessive EPC exhaustion.

CLINICAL TRIAL NUMBER

NCT03710811.

Beneficial Role of Vitamin D on Endothelial Progenitor Cells (EPCs) in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death in the world. Endothelial progenitor cells (EPCs) are currently being explored in the context of CVD risk. EPCs are bone marrow derived progenitor cells involved in postnatal endothelial repair and neovascularization. A large body of evidence from clinical, animal, and in vitro studies have shown that EPC numbers in circulation and their functionality reflect endogenous vascular regenerative capacity. Traditionally vitamin D is known to be beneficial for bone health and calcium metabolism and in the last two decades, its role in influencing CVD and cancer risk has generated significant interest. Observational studies have shown that low vitamin D levels are associated with an adverse cardiovascular risk profile. Still, Mendelian randomization studies and randomized control trials (RCTs) have not shown significant effects of vitamin D on cardiovascular events. The criticism regarding the RCTs on vitamin D and CVD is that they were not designed to investigate cardiovascular outcomes in vitamin D-deficient individuals. Overall, the association between vitamin D and CVD remains inconclusive. Recent clinical and experimental studies have demonstrated the beneficial role of vitamin D in increasing the circulatory level of EPC as well as their functionality. In this review we present evidence supporting the beneficial role of vitamin D in CVD through its modulation of EPC homeostasis.

The Role of Vitamin D in Modulating Mesenchymal Stem Cells and Endothelial Progenitor Cells for Vascular Calcification

Vascular calcification, which involves the deposition of calcifying particles within the arterial wall, is mediated by atherosclerosis, vascular smooth muscle cell osteoblastic changes, adventitial mesenchymal stem cell osteoblastic differentiation, and insufficiency of the calcification inhibitors. Recent observations implied a role for mesenchymal stem cells and endothelial progenitor cells in vascular calcification. Mesenchymal stem cells reside in the bone marrow and the adventitial layer of arteries. Endothelial progenitor cells that originate from the bone marrow are an important mechanism for repairing injured endothelial cells. Mesenchymal stem cells may differentiate osteogenically by inflammation or by specific stimuli, which can activate calcification. However, the bioactive substances secreted from mesenchymal stem cells have been shown to mitigate vascular calcification by suppressing inflammation, bone morphogenetic protein 2, and the Wingless-INT signal. Vitamin D deficiency may contribute to vascular calcification. Vitamin D supplement has been used to modulate the osteoblastic differentiation of mesenchymal stem cells and to lessen vascular injury by stimulating adhesion and migration of endothelial progenitor cells. This narrative review clarifies the role of mesenchymal stem cells and the possible role of vitamin D in the mechanisms of vascular calcification.

Association of vitamin D status with coronary artery disease in postmenopausal women

The relationship between coronary artery disease (CAD) and low serum 25-hydroxyvitamin D (25(OH)D) levels has emerged. Postmenopausal (PM) women are at increased risk of CAD and vitamin D (VitD) deficiency.To investigate the relationship between CAD and VitD levels in PM women.This case-control study included 93 consecutive female patients aged 50 to 79 years old undergoing coronary angiography for evaluation of CAD and 119 age-matched controls. Serum 25(OH)D concentrations were classed as adequate (serum 25(OH)D: ≥20 ng/mL); insufficient (serum 25(OH)D: 10 to <20 ng/mL); and deficient (serum 25(OH)D: <10 ng/mL). Major cardiovascular risk factors were also explored.CAD occurred in 67/127 (52.8%) patients with VitD deficiency; 21/66 (31.8%) patients that were VitD insufficient; and in 5/19 (26.3%) patients with adequate VitD levels. Multivariate regression analysis suggested that a deficiency of VitD increased CAD (odds ratio = 2.891; 95% confidence interval = 1.459-7.139, P < .001).VitD deficiency should be evaluated in PM women as a possible cause of CAD.

Vitamin D protects against diabetic nephropathy: Evidence-based effectiveness and mechanism

Vitamin D has been suggested to harbor multiple biological activities, among them the potential of vitamin D in the protection of diabetic nephropathy (DN) has attracted special attention. Both animal studies and clinical trials have documented an inverse correlation between low vitamin D levels and DN risk, and supplementation with vitamin D or its active derivatives has been demonstrated to improve endothelial cell injury, reduce proteinuria, attenuate renal fibrosis, and resultantly retard DN progression. Vitamin D exerts its pharmacological effects primarily via vitamin D receptor, whose activation inhibits the renin-angiotensin system, a key culprit for DN under hyperglycemia. The anti-DN benefit of vitamin D can be enhanced when administrated in combination with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. Mechanistic studies reveal that pathways relevant to inflammation participate in the pathogenesis of DN, however, consumption of vitamin D-related products negatively regulates inflammatory response at multiple levels, indicated by inhibiting macrophage infiltration, nuclear factor-kappa B (NF-κB) activation, and production of such inflammatory mediators as transforming growth factor-β(TGF-β), monocyte chemoattractant protein 1(MCP-1), and regulated upon activation normal T cell expressed and secreted protein(RANTES). The robust anti-inflammatory property of vitamin D-related products allows them with a promising renoprotective therapeutic option for DN. This review summarizes new advances in our understanding of vitamin D-related products in the DN management.

Endothelial Progenitor Cells: New Targets for Therapeutics for Inflammatory Conditions With High Cardiovascular Risk

Over the past decade, we have witnessed an exponential growth of interest into the role of endothelial progenitor cells (EPCs) in cardiovascular disease. While the major thinking revolves around EPC angiogenic repair properties, we have used a hypothesis-driven approach to discover disease-related defects in their characteristics and based on these findings, have identified opportunities for functional enhancement, which offer an exciting avenue for translation into clinical intervention. In this review, we focus on two groups; circulating myeloid angiogenic cells (MACs) and late outgrowth endothelial colony forming cells (ECFCs), and will discuss the unique properties and defects of each population, as new insights have been gained into the potential function of each sub-type using current techniques and multiomic technology. We will discuss their role in inflammatory disorders and alterations in mitochondrial function. In addition, we share key insights into the glycocalyx, and propose this network of membrane-bound proteoglycans and glycoproteins, covering the endothelium warrants further investigation in order to clarify its significance in ECFC regulation of vascularization and angiogenesis and ultimately for potential translational therapeutic aspects.