Protective and toxic effects of vitamin D on vascular calcification: Clinical implications

Relationship between histopathological findings of patients with dermatochalasis and vitamin D deficiency

PURPOSE

To compare the histopathological findings of patients who had been diagnosed with dermatochalasis (DC) and had undergone upper eyelid blepharoplasty (ULB) as well as those of controls (C-Group) according to their serum vitamin D (SVD) levels.

METHODS

The prospective study included 136 upper eyelid skin from 68 patients who underwent surgery for DC and 53 upper eyelid skin from 53 patients who underwent levator surgery with ULB. The DC Group was then divided into 3 subgroups according to the marginal reflex distance (MRD4). The lymphatic vessel (LV) count and diameter of the largest LV (DLLV) were recorded, the stromal collagen bed (SCB) was observed, and its depth was measured, the interfibrillar edema was examined, and the elastic fiber and macrophage counts and recorded, respectively, and then all of these were evaluated. The SVD levels were compared between the DC patients and the C-Group.

RESULTS

In comparison to the C-Group, significant changes were seen in the dilated LV, DLLV, SCB depth, interfibrillar edema, elastic fiber density, and macrophage count in the DC sub-Groups (P < 0.001 for all). While no difference was found between DC sub-Group 1 (MRD4 > 4 mm) and the C-Group (P > 0.05), a significant difference was found between DC sub-Group 2 (MRD4 2-4 mm) and DC sub-Group 3 (MRD4 < 2 mm) for all of the parameters (P < 0.05). A statistically significant difference was also found in the SVD levels between the DC sub-Group 1 and DC sub-Groups 2-3 (P < 0.017, P < 0.001 respectively).

CONCLUSION

According to the results of this study, SVD level was significantly lower in DC group. Moreover, an increased LV count and diameter, decreased elastic fiber count, collagen fiber and stromal edema irregularity, and increased macrophage count were found to be associated with the SVD level.

Vitamin D and ischemic stroke - Association, mechanisms, and therapeutics

Confronting the rising tide of ischemic stroke and its associated mortality and morbidity with ageing, prevention and acute management of ischemic stroke is of paramount importance. Mounting observational studies have established a non-linear association of vitamin D status with cardiovascular diseases, including ischemic stroke. Paradoxically, current clinical trials fail to demonstrate the cardiovascular benefits of vitamin D supplementation. We aim to update recent clinical and experimental findings on the role of vitamin D in the disease course of ischemic stroke, from its onset, progression, recovery, to recurrence, and the established and alternative possible pathophysiological mechanisms. This review justifies the necessities to address stroke etiological subtypes and focus on vitamin D-deficient subjects for investigating the potential of vitamin D supplementation as a preventive and therapeutic approach for ischemic stroke. Well-powered clinical trials are warranted to determine the efficacy, safety, timing, target individuals, optimal dosages, and target 25OHD concentrations of vitamin D supplementation in the prevention and treatment of ischemic stroke.

Changes in choroidal tissue post-supplementation with vitamin D in pediatric patients who are deficient in vitamin D

PURPOSE

To quantitatively assess the choroidal structural parameters of patients in the pediatric age group who were deficient in vitamin D [Vit-D] pre- and post-treatment.

DESIGN

Prospective, case-control study.

METHODS

Choroidal structural parameters, including the choroidal thickness (CT) at five points, total choroidal area (TA), luminal choroidal area (LA), stromal choroidal area (SA), and choroidal vascular index (CVI), in patients in the pediatric age group who were deficient in Vit-D, in Group 1, and those who were not, in Group 2, were compared. The patients were divided into 3 different groups according to how deficient in Vit-D they were. This was re-evaluated after treatment.

RESULTS

Group 1 consisted of 83 patients and group 2 consisted of 85 patients. CT at all five points, and the TA, SA, LA, and CVI, were lower in Group 1. And for all of these, a significant increase was seen post-treatment. While a significant increase was observed in all of the values in the group with the most severe deficiency in Vit-D, significant changes were observed in the TA, LA, SA, and CVI values in the group that was mildly deficient in Vit-D. There was no significant post-treatment value in the CT values (except for the Temporal 1500 CT [P = 0.012]).

CONCLUSION

Decreases in the CT, TA, LA, SA, and CVI were among the structural changes that were seen to occur in the pediatric patient group that was deficient in Vit-D. Moreover, thinning of the choroid and a decrease in the CVI were the most significant in the group with the greatest Vit-D deficiency.

Safety Profile of Vitamin D in Italy: An Analysis of Spontaneous Reports of Adverse Reactions Related to Drugs and Food Supplements

Vitamin D (VitD) is largely used in Italy, often inappropriately; thus, an evaluation of its safety is a crucial issue. This study analyses the adverse reactions (ARs) associated with the use of products containing VitD (VitDps) reported to the Italian National Pharmacovigilance and Phytovigilance networks. From March 2002 to August 2022, a total of 643 and 127 reports concerning 903 and 215 ARs were retrieved from Pharmacovigilance and Phytovigilance networks, respectively. Overall, 332 (29.6%) ARs were classified as serious, and the most described ones were hypercalcaemia, renal failure and tachycardia. Serious AR risk was significantly higher for subjects using more than four concomitant products (OR 2.44 [95% CI 1.30-4.60]) and VitD doses higher than 1000 IU/day (OR 2.70 [95% CI 1.30-5.64]). In Italy, there was a modest decrease in AR reporting, despite the slightly increased use of VitD during the COVID-19 pandemic. To the best of our knowledge, this is the first study describing all VitDps-related ARs observed in the Italian general population. Since underreporting is the main limitation of the safety reporting systems, the necessity to continue ARs monitoring, also using real-world data on VitDps prescription, use and outcome patterns is highlighted.

Insights into Insulin Resistance and Calcification in the Myocardium in Type 2 Diabetes: A Coronary Artery Analysis

Type 2 diabetes (T2D) is responsible for high incidence of cardiovascular (CV) complications leading to heart failure. Coronary artery region-specific metabolic and structural assessment could provide deeper insight into the extent of the disease and help prevent adverse cardiac events. Therefore, in this study, we aimed at investigating such myocardial dynamics for the first time in insulin-sensitive (mIS) and insulin-resistant (mIR) T2D patients. We targeted global and region-specific variations using insulin sensitivity (IS) and coronary artery calcifications (CACs) as CV risk factor in T2D patients. IS was computed using myocardial segmentation approaches at both baseline and after an hyperglycemic-insulinemic clamp (HEC) on [¹⁸F]FDG-PET images using the standardized uptake value (SUV) (ΔSUV = SUV_HEC - SUV_BASELINE) and calcifications using CT Calcium Scoring. Results suggest that some communicating pathways between response to insulin and calcification are present in the myocardium, whilst differences between coronary arteries were only observed in the mIS cohort. Risk indicators were mostly observed for mIR and highly calcified subjects, which supports previously stated findings that exhibit a distinguished exposure depending on the impairment of response to insulin, while projecting added potential complications due to arterial obstruction. Moreover, a pattern relating calcification and T2D phenotypes was observed suggesting the avoidance of insulin treatment in mIS but its endorsement in mIR subjects. The right coronary artery displayed more ΔSUV, whilst plaque was more present in the circumflex. However, differences between phenotypes, and therefore CV risk, were associated to left descending artery (LAD) translating into higher CACs regarding IR, which could explain why insulin treatment was effective for LAD at the expense of higher likelihood of plaque accumulation. Personalized approaches to assess T2D may lead to more efficient treatments and risk-prevention strategies.

Can Bioactive Food Substances Contribute to Cystic Fibrosis-Related Cardiovascular Disease Prevention?

Advances in cystic fibrosis (CF) care have significantly improved the quality of life and life expectancy of patients. Nutritional therapy based on a high-calorie, high-fat diet, antibiotics, as well as new therapies focused on CFTR modulators change the natural course of the disease. They do so by improving pulmonary function and growing BMI. However, the increased weight of such patients can lead to unwanted long-term cardiovascular effects. People with CF (pwCF) experience several cardiovascular risk factors. Such factors include a high-fat diet and increased dietary intake, altered lipid metabolism, a decrease in the level of fat-soluble antioxidants, heightened systemic inflammation, therapeutic interventions, and diabetes mellitus. PwCF must pay special attention to food and eating habits in order to maintain a nutritional status that is as close as possible to the proper physiological one. They also have to benefit from appropriate nutritional counseling, which is essential in the evolution and prognosis of the disease. Growing evidence collected in the last years shows that many bioactive food components, such as phytochemicals, polyunsaturated fatty acids, and antioxidants have favorable effects in the management of CF. An important positive effect is cardiovascular prevention. The possibility of preventing/reducing cardiovascular risk in CF patients enhances both quality of life and life expectancy in the long run.

Association between Serum 25-Hydroxyvitamin D and Abdominal Aortic Calcification: A Large Cross-Sectional Study

In the American population, the relationship between the standardized serum 25-hydroxyvitamin D (25(OH)D) concentration and the risk of abdominal aortic calcification (AAC) is unclear. The purpose of our study was to investigate the relationship between serum 25(OH)D concentration and AAC risk. Participants from the National Health and Nutrition Examination Survey (NHANES) between 2013 and 2014 were analyzed cross sectionally. An analysis of the relationship between serum 25(OH)D concentration and incident AAC and severe AAC (SAAC) was based on the restricted cubic spline (RCS) and multivariable logistic regression model. In addition, generalized additive models with smooth functions were used to evaluate the relationship between serum 25(OH)D concentration and the degree of AAC. Finally, a subgroup analysis was conducted. There were a total of 3,040 individuals in our study. The serum 25(OH)D concentration was divided into quartiles (Q1: 9.37-50.5 nmol/L; Q2: 50.6-67.2 nmol/L; Q3: 67.3-85.8 nmol/L; and Q4: 85.9-318.0 nmol/L); the lowest quartile served as the reference group (Q1). After adjusting for known confounding variables, compared with the lowest quartile (Q1) of serum 25(OH)D concentration, the odds ratios with 95% confidence intervals for AAC and SAAC across the quartiles (Q2, Q3, and Q4) were (1.042 (0.812, 1.338), 0.863 (0.668, 1.115), and 1.022 (0.787, 1.327)) and (1.48 (0.87, 2.52), 1.70 (1.01, 2.92), and 2.13 (1.19, 3.86)), respectively. As shown by the RCS plot, the serum 25(OH)D concentration was associated with the risk of AAC/SAAC in a U-shaped pattern (P for nonlinearity <0.05). In addition, the degree of AAC decreased at first and then increased as the serum 25(OH)D concentration increased. In conclusion, a U-shaped relationship existed between serum 25(OH)D concentration and the risk of AAC and SAAC. Consequently, the risk of AAC and SAAC may be mitigated with regular monitoring and vitamin D supplementation.

Associations between diabetic retinopathy and modifiable risk factors: An umbrella review of meta-analyses

AIMS

Several modifiable risk factors have been meta-analysed for diabetic retinopathy (DR), such as physical activity and vitamin D status. To date, these factors have not been systematically aggregated and the credibility of evidence assessed. Therefore, the aim of this umbrella review was to aggregate all modifiable risks of DR and assess the credibility of the evidence.

METHODS

An umbrella review of meta-analyses was undertaken. For each meta-analytic association, random-effects effect size, 95% confidence intervals (CIs), heterogeneity, small-study effects, excess significance bias and 95% prediction intervals were calculated. The credibility of significant evidence (p < 0.05) was graded from I to IV, using pre-defined criteria.

RESULTS

After initial searches, 13 studies were included covering 34 independent outcomes (total participants = 824,372). Positive associations were found between insulin usage and diabetic macular oedema (RR = 4.5; 95% CI 3.1-6.6), and DR risk (RR = 2.3; 95% CI 1.4-3.9) in people with type 2 diabetes. Vitamin D deficiency was associated with DR risk (OR = 2.8; 95% CI 1.1-7.1), as was obesity (RR = 1.34; 95% CI 1.06-1.68) and sedentary behaviour (RR = 1.22; 95%CI 1.03-1.44). Intensive blood pressure targets (RR = 0.8 95%CI 0.8-1.0), and moderate physical activity (RR = 0.69; 95%CI 0.53-0.91) yielded significant protective associations with DR.

CONCLUSIONS

People with type 2 diabetes on insulin have a high risk of macular oedema and DR. Vitamin D deficiency yielded almost three times greater odds of DR, while intensive blood pressure control reduces DR risk by 20% and moderate physical activity by 31%. Healthcare professionals should use this evidence to identify those people most at risk to ensure that proper treatment and healthy lifestyles are recommended.

Vitamin D as therapeutic modulator in cerebrovascular diseases: a mechanistic perspectives

Vitamin D deficiency has been linked to several major chronic diseases, such as cardiovascular and neurodegenerative diseases, diabetes, and cancer, linked to oxidative stress, inflammation, and aging. Vitamin D deficiency appears to be particularly harmful to the cardiovascular system, as it can cause endothelial dysfunctioning and vascular abnormalities through the modulation of various downstream mechanisms. As a result, new research indicates that therapeutic approaches targeting vitamin D inadequacies or its significant downstream effects, such as impaired autophagy, abnormal pro-inflammatory and pro-oxidant reactions, may delay the onset and severity of major cerebrovascular disorders such as stroke and neurologic malformations. Vitamin D modulates the various molecular pathways, i.e., Nitric Oxide, PI3K-Akt Pathway, cAMP pathway, NF-kB Pathway, Sirtuin 1, Nrf2, FOXO, in cerebrovascular disorder. The current review shows evidence for vitamin D's mitigating or slowing the progression of these cerebrovascular disorders, which are significant causes of disability and death worldwide.

The peculiar role of vitamin D in the pathophysiology of cardiovascular and neurodegenerative diseases

Vitamin D is a hormone with both genomic and non-genomic actions. It exerts its activity by binding vitamin D receptor (VDR), which belongs to the superfamily of nuclear receptors and ligand-activated transcription factors. Since VDR has been found in various tissues, it has been estimated that it regulates approximately 3% of the human genome. Several recent studies have shown pleiotropic effects of vitamin D in various processes such as cellular proliferation, differentiation, DNA repair and apoptosis and its involvement in different pathophysiological conditions as inflammation, diabetes mellitus, and anemia. It has been suggested that vitamin D could play an important role in neurodegenerative and cardiovascular disorders. Moderate to strong associations between lower serum vitamin D concentrations and stroke and cardiovascular events have been identified in different analytic approaches, even after controlling for traditional demographic and lifestyle covariates. The mechanisms behind the associations between vitamin D and cerebrovascular and cardiologic profiles have been widely examined both in animal and human studies. Optimization of vitamin D levels in human subjects may improve insulin sensitivity and beta-cell function and lower levels of inflammatory markers. Moreover, it has been demonstrated that altered gene expression of VDR and 1,25D3-membrane-associated rapid response steroid-binding (1,25D3-MARRS) receptor influences the role of vitamin D within neurons and allows them to be more prone to degeneration. This review summarizes the current understanding of the molecular mechanisms underlying vitamin D signaling and the consequences of vitamin D deficiency in neurodegenerative and cardiovascular disorders.

Evaluation of Retinal Structure in Pediatric Subjects With Vitamin D Deficiency

PURPOSE

To quantitatively evaluate the retinal structural parameters of pediatric patients who were determined to be deficient in vitamin D.

DESIGN

Prospective, cross-sectional study.

METHODS

Retinal structural parameters, including the peripapillary retinal nerve fiber layer (RNFL), central macula, retinal layer, and choroidal thicknesses, central retinal artery equivalent (CRAE), and central retinal vein equivalent (CRVE), in pediatric subjects with vitamin D deficiency (group 1) and those without (group 2) were compared.

RESULTS

Group 1 comprised 70 individuals, while group 2 comprised 80 individuals. The mean peripapillary RNFL (except for the nasal superior sector [P = .037]), central macula, and retinal layer thicknesses were also determined to be similar in both groups (P > .05 for both groups). The mean choroidal thickness was lower in the subfoveal (P = .006) and nasal 3000-µm-diameter areas (P = .004) in group 1. The mean CRAE was determined to be lower (P = .031) and the CRVE was higher in group 1 (P = .005); it was determined that there was a significant correlation between the vitamin D level and both the CRAE (r = 0.447, P < .001) and CRVE (r = -0.320, P = .013).

CONCLUSION

Choroidal thinning, a decrease in the CRAE, and increase in the CRVE were structural changes that occurred in the pediatric subjects who had vitamin D deficiency. The alterations in these parameters became more prominent in pediatric subjects who were determined to have lower vitamin D levels.

Primary and Secondary Prevention of CAD: A Review

Coronary artery disease is the leading cause of death in both men and women, yet adequate control of risk factors can largely reduce the incidence and recurrence of cardiac events. In this review, we discuss various life style and pharmacological measures for both the primary and secondary prevention of coronary artery disease. With a clear understanding of management options, health care providers have an excellent opportunity to educate patients and ameliorate a significant burden of morbidity and mortality.

Vitamin D and Cardiovascular Disease: An Updated Narrative Review

During the last two decades, the potential impact of vitamin D on the risk of cardiovascular disease (CVD) has been rigorously studied. Data regarding the effect of vitamin D on CVD risk are puzzling: observational data indicate an inverse nonlinear association between vitamin D status and CVD events, with the highest CVD risk at severe vitamin D deficiency; however, preclinical data and randomized controlled trials (RCTs) show several beneficial effects of vitamin D on the surrogate parameters of vascular and cardiac function. By contrast, Mendelian randomization studies and large RCTs in the general population and in patients with chronic kidney disease, a high-risk group for CVD events, largely report no significant beneficial effect of vitamin D treatment on CVD events. In patients with rickets and osteomalacia, cardiovascular complications are infrequently reported, except for an increased risk of heart failure. In conclusion, there is no strong evidence for beneficial vitamin D effects on CVD risk, either in the general population or in high-risk groups. Whether some subgroups such as individuals with severe vitamin D deficiency or a combination of low vitamin D status with specific gene variants and/or certain nutrition/lifestyle factors would benefit from vitamin D (metabolite) administration, remains to be studied.

The effect of physical activity on dose-relationship between serum 25-hydroxyvitamin D and cardiovascular health events in older adults

BACKGROUND AND AIMS

Reverse J- or U-shaped associations between serum 25-hydroxyvitamin D (25[OH]D) concentrations and cardiovascular outcomes have been reported, which need clarifications in older adults. Physical activity, correlating with both serum 25[OH]D concentration and cardiovascular health, may have an effect on the dose-relationships.

METHODS AND RESULTS

At baseline, 2790 participants aged 65 years and over, free of vitamin D supplementation use, had assays for serum 25[OH]D concentrations and health related characteristics and measurements, were followed up for cardiovascular events and death by up to 7 and 15 years, respectively. The dose-response associations of serum 25[OH]D concentrations with cardiovascular events and mortality risk were examined using Cox regression models. After adjusting for physical activity and other covariates, serum 25[OH]D concentration was non-linearly associated with cardiovascular mortality risk (U-shaped, P = 0.009). According to the Institute of Medicine categories, the HR(95% CI) of cardiovascular mortality risk separately in deficient (<25 nmol/L), inadequate (25 to < 50 nmol/L) and potentially harmful (≥125 nmol/L) level was 1.67 (0.23, 12.01), 1.66 (1.25, 2.20) and 2.21 (0.30, 16.37), respectively. The risk of 25[OH]D inadequacy for cardiovascular mortality was significantly attenuated by increased physical activity, especially leisure activity (P for trend = 0.008 and 0.021, respectively). No significant finding was observed for incident cardiovascular events.

CONCLUSION

Both lower and higher serum 25[OH]D concentrations were associated with risk of cardiovascular mortality in Chinese community-dwelling older adults. Physical activity may attenuate the cardiovascular mortality risk of vitamin D inadequacy, but its role in individuals with higher 25[OH]D concentrations remains unclear.

Assessment of Subclinical Atherosclerosis in Vitamin D Deficiency

PURPOSE

Patients with vitamin D deficiency (VDD) have potential to have increased cardiovascular morbidity and mortality. In this study, we aimed to discover the findings of early atherosclerosis in patients with VDD by measuring carotid intima-media thickness (CIMT) and epicardial fat thickness (EFT).

MATERIALS AND METHODS

The study population includes 52 patients with VDD (n = 30 [57% female], mean ± SD age 54.28 ± 8.77 years, mean ± SD serum 25-hydroxyvitamin D (25 [OH] D) 11 ± 2.4 ng/mL) and 82 participants for control group (n = 52 [63.4% female], mean ± SD age 56.40 ± 7.90 years, mean ± SD serum (25 [OH] D) 53 ± 4.2 ng/mL) who have no cardiovascular disease. Carotid intima-media thickness was assessed by using ultrasonography, and EFT was measured on the free wall of the right ventricle at end diastole from the parasternal long-axis views by standard transthoracic 2-dimensional echocardiography.

RESULTS

Both CIMT and EFT were significantly higher in patients with VDD compared with controls (0.75 ± 0.16 mm vs 0.68 ± 0.21 mm, P < 0.05, and 0.66 ± 0.15 cm vs 0.56 ± 0.15 cm, P < 0.001).

CONCLUSIONS

Patients with VDD seem to have increased CIMT and EFT, which are predictors of atherosclerotic process. Further studies are needed to confirm these results.

Vitamin D and cardiovascular disease in chronic kidney disease

Chronic kidney disease (CKD) is considered an independent risk factor for cardiovascular disease, with increased cardiovascular morbidity and mortality seen even in the early stages of CKD. Several studies have shown a high prevalence of vitamin D deficiency in individuals with CKD. Low vitamin D levels upregulate the renin-angiotensin-aldosterone system (RAAS), cause endothelial dysfunction, and increase inflammation. Epidemiological studies show an association between vitamin D deficiency and risk factors for cardiovascular disease, but a causal relationship has not been established. The high cardiovascular morbidity and mortality associated with CKD in adults requires therapies to decrease this elevated risk. However, results from several meta-analyses and randomized clinical trials in adults have not shown convincing evidence for the use of vitamin D therapy in improving cardiovascular outcomes. Lack of high-quality evidence from randomized clinical trials in children regarding the effectiveness and long-term safety of vitamin D treatment precludes any recommendations on its use to mitigate the cardiovascular burden of CKD.

A Bayesian network analysis on comparative efficacy of treatment strategies for dialysis patients with secondary hyperparathyroidism

For dialysis patients with end-stage kidney disease and secondary hyperparathyroidism (SHPT), there are three therapeutic treatment options: Cinacalcet, paricalcitol and cinacalcet plus low-dose vitamin D analogues. However, their comparative efficacy remains unclear at present. Thus, in the current study, a Bayesian network analysis was conducted to evaluate the relative efficacy and safety of these three therapeutic regimens. A comprehensive literature database query was performed. The primary outcome was the treatment effect on serum parathyroid hormone (PTH) levels. Secondary outcomes included the occurrence of nausea and hypocalcaemia. A total of 20 randomized clinical trials, including 5,390 dialysis patients, were entered into the analysis. Paricalcitol, cinacalcet plus vitamin D analogue and cinacalcet were significantly more efficacious in controlling PTH levels compared with conventional therapy (which comprises calcium-based phosphate binders, non-calcium-based phosphate binders and vitamin D analogues) [odds ratio (OR)=3.99, 2.91 and 2.47, respectively] and placebo (OR=20.32, 14.89 and 12.56, respectively). Paricalcitol was identified as the most efficacious of the three treatments. According to a ranking analysis, patients treated with cinacalcet had a higher possibility of frequently developing nausea and hypocalcaemia compared with patients treated with cinacalcet plus low-dose active vitamin D analogues. All three therapeutic treatment options were efficacious for the treatment of dialysis patients with SHPT in controlling PTH levels. Paricalcitol had the highest possibility of being the most optimal one. Thus, paricalcitol therapy may be the most optimal regimen in controlling PTH levels, but this should be confirmed by further study.

Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact

It is widely known that vitamin D receptors have been found in neurons and glial cells, and their highest expression is in the hippocampus, hypothalamus, thalamus and subcortical grey nuclei, and substantia nigra. Vitamin D helps the regulation of neurotrophin, neural differentiation, and maturation, through the control operation of growing factors synthesis (i.e., neural growth factor [NGF] and glial cell line-derived growth factor (GDNF), the trafficking of the septohippocampal pathway, and the control of the synthesis process of different neuromodulators (such as acetylcholine [Ach], dopamine [DA], and gamma-aminobutyric [GABA]). Based on these assumptions, we have written this review to summarize the potential role of vitamin D in neurological pathologies. This work could be titanic and the results might have been very fuzzy and even incoherent had we not conjectured to taper our first intentions and devoted our interests towards three mainstreams, demyelinating pathologies, vascular syndromes, and neurodegeneration. As a result of the lack of useful therapeutic options, apart from the disease-modifying strategies, the role of different risk factors should be investigated in neurology, as their correction may lead to the improvement of the cerebral conditions. We have explored the relationships between the gene-environmental influence and long-term vitamin D deficiency, as a risk factor for the development of different types of neurological disorders, along with the role and the rationale of therapeutic trials with vitamin D implementation.

25-hydroxyvitamin D Levels was not Associated with Blood Pressure and Arterial Stiffness in Patients with Chronic Kidney Disease

Background

We investigated the effect of vitamin D deficiency on cardiovascular risk profiles in an Asian population with chronic kidney disease (CKD).

Methods

A total of 210 participants (62 non-dialysis CKD patients and 148 hemodialysis [HD] patients) were enrolled between December 2009 and February 2010. Vitamin D deficiency was determined using the serum 25-hydroxyvitamin D [25(OH)D] concentration. Blood pressure and arterial stiffness were measured. Subjects were divided into groups according to 25(OH)D concentration based on a cut-off of 13.5 ng/mL in non-dialysis CKD patients and 11.3 ng/mL in HD patients.

Results

The mean age was 61.7±12.3 years in non-dialysis CKD patients and 57.0±12.7 years in HD patients. In the non-dialysis CKD group, mean estimated glomerular filtration rate (eGFR) was 29.7±15.4 mL/min/1.73 m². Mean 25(OH)D concentration was 13.6±7.8 ng/mL in non-dialysis CKD patients and 11.3±6.7 ng/mL in HD patients. More than half of the subjects had vitamin D deficiency (67.6% in non-dialysis CKD patients and 80.4% in HD patients). There were no significant differences in systolic blood pressure, pulse pressure, and arterial stiffness between higher and lower 25(OH)D groups among non-dialysis CKD and HD patients. Multivariate analysis revealed that female sex (odds ratio [OR]: 5.890; 95% confidence interval [CI]: 2.597–13.387; p<0.001) and presence of diabetes (OR: 2.434; 95% CI: 1.103–5.370; p=0.028) were significantly associated with lower serum 25(OH)D levels in HD patients.

Conclusion

The prevalence of vitamin D deficiency was high in both nondialysis CKD patients and HD patients. Serum 25(OH)D concentration was not a significant factor associated with blood pressure and arterial stiffness among non-dialysis CKD and HD patients.

Vitamin D and cardiovascular diseases: Causality

Vitamin D regulates blood pressure, cardiac functions, and endothelial and smooth muscle cell functions, thus, playing an important role in cardiovascular health. Observational studies report associations between vitamin D deficiency with hypertension and cardiovascular-related deaths. Peer-reviewed papers were examined in several research databases as per the guidelines of the Preferred Reporting Items for Systematic Reviews, using key words that address the relationship between vitamin D and cardiovascular disease. Correlations and interpretations were made considering the risks-benefits, broader evidence, and implications. This review analyzed current knowledge regarding the effects of vitamin D on the cardiovascular system. 1,25(OH)₂D and related epigenetic modifications subdue cellular inflammation, improve overall endothelial functions, reduce age-related systolic hypertension and vascular rigidity, and attenuate the actions of the renin-angiotensin-aldosterone system. Most observational and ecological studies support 25(OH)vitamin D having protective effects on the cardiovascular system. However, the association of vitamin D deficiency with cardiovascular diseases is based primarily on observational and ecological studies and thus, is a matter of controversy. Adequately powered, randomized controlled clinical trial data are not available to confirm these associations. Thus, to test the hypothesis that correction of vitamin D deficiency protects the cardiovascular system, well-designed, statistically powered, longer-term clinical trials are needed in persons with vitamin D deficiency. Nevertheless, the available data support that adequate vitamin D supplementation and/or sensible sunlight exposure to achieve optimal vitamin D status are important in the prevention of cardiovascular disease and other chronic diseases.

Newly Developed Rat Model of Chronic Kidney Disease-Mineral Bone Disorder

Aim: Chronic kidney disease–mineral bone disorder (CKD–MBD) is associated with all-cause and cardiovascular morbidity and mortality in patients with CKD. Thus, elucidating its pathophysiological mechanisms is essential for improving the prognosis. We evaluated characteristics of CKD–MBD in a newly developed CKD rat model.

Methods: We used male Sprague–Dawley (SD) rats and spontaneously diabetic Torii (SDT) rats, which are used as models for nonobese type 2 diabetes. CKD was induced by 5/6 nephrectomy (Nx). At 10 weeks, the rats were classified into six groups and administered with a vehicle or a low- or high-dose paricalcitol thrice a week. At 20 weeks, the rats were sacrificed; blood and urinary biochemical analyses and histological analysis of the aorta were performed.

Results: At 20 weeks, hemoglobin A1c (HbA1c) levels, blood pressure, and renal function were not significantly different among the six groups. Serum calcium and phosphate levels tended to be higher in SDT-Nx rats than in SD-Nx rats. The urinary excretion of calcium and phosphate was significantly greater in SDT-Nx rats than in SD-Nx rats. After administering paricalcitol, serum parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) levels were significantly higher in SDT-Nx rats than in SD-Nx rats. The degree of aortic calcification was significantly more severe and the aortic calcium content was significantly greater in SDT-Nx rats than in SD-Nx rats.

Conclusions: We suggest that our new CKD rat model using SDT rats represents a useful CKD–MBD model, and this model was greatly influenced by paricalcitol administration. Further studies are needed to clarify the detailed mechanisms underlying this model.

Effect of vitamin D on isoprenaline-induced myocardial infarction in rats: possible role of peroxisome proliferator-activated receptor-γ

Infarct-like lesion induced by isoprenaline is a well-known model to study myocardial infarction (MI). Vitamin D has been shown to have anti-inflammatory and antioxidant effects. Recent studies highlighted cross talk between vitamin D and peroxisome proliferator-activated receptor gamma (PPAR-γ). The present study was designed to investigate the effect of pretreatment with vitamin D on the isoprenaline-induced infarct-like lesion in rats and the role of PPAR-γ as a novel mechanism in vitamin-D-mediated cardioprotective effect. Markers chosen to assess cardiac damage included serum level of creatine kinase (CK), lactate dehydrogenase (LDH), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). Cardiac contents of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH) were also assessed. Furthermore, ECG monitoring and measurement of injury extension were carried out. Isoprenaline increased the level of cardiac enzymes, as well as inflammatory and oxidative stress biomarkers. In addition, it produced ST-segment elevation. Pretreatment with vitamin D significantly improved previous parameters. The prior treatment with bisphenol A diglycidyl ether (BADGE), a PPAR-γ antagonist, significantly attenuated the protective effect of vitamin D. In conclusion, vitamin D can be demonstrated as a promising cardioprotective agent in MI and PPAR-γ significantly contributes toward vitamin-D-mediated protection.

The Association between Vitamin D Deficiency and Diabetic Retinopathy in Type 2 Diabetes: A Meta-Analysis of Observational Studies

Emerging evidence from in vivo and in vitro studies have shown that vitamin D may play an important role in the development of diabetic retinopathy (DR), but individually published studies showed inconclusive results. The aim of this study was to quantitatively summarize the association between vitamin D and the risk of diabetic retinopathy. We conducted a systematic literature search of Pubmed, Medline, and EMBASE updated in September 2016 with the following keywords: "vitamin D" or "cholecalciferol" or "25-hydroxyvitamin D" or "25(OH)D" in combination with "diabetic retinopathy" or "DR". Fifteen observational studies involving 17,664 subjects were included. In this meta-analysis, type 2 diabetes patients with vitamin D deficiency (serum 25(OH)D levels <20 ng/mL) experienced a significantly increased risk of DR (odds ratio (OR) = 2.03, 95% confidence intervals (CI): 1.07, 3.86), and an obvious decrease of 1.7 ng/mL (95% CI: -2.72, -0.66) in serum vitamin D was demonstrated in the patients with diabetic retinopathy. Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. In conclusion, the evidence from this meta-analysis indicates an association between vitamin D deficiency and an increased risk of diabetic retinopathy in type 2 diabetes patients.

Comparison of the effects of novel vitamin D receptor analog VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder in an experimental model of chronic kidney disease

When using vitamin D, the most important clinical problems are hypercalcemia, hyperphosphatemia, and vascular calcification. VS-105 is a novel vitamin D receptor (VDR) analog. In the present study, we compared the effects of VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder (CKD-MBD) in a CKD rat model. We used male Sprague-Dawley (SD) rats and performed 5/6 nephrectomy at 8-9 weeks. At 10 weeks, the rats were classified into five groups and administered vehicle, low-dose paricalcitol (LP, 0.1μg/kg), high-dose paricalcitol (HP, 0.3μg/kg), low-dose VS-105 (LV, 0.2μg/kg), and high-dose VS-105 (HV, 0.6 μg/kg) three times a week for 10 weeks. There were no significant differences in blood pressure or renal function among the five groups. Alhough serum calcium levels were comparable between the LP and LV groups, they were higher in the HP group than in the HV group. Serum phosphate levels were higher in the paricalcitol-treated groups than in the VS-105-treated groups and paticularly higher in the HP group than in the other groups. The urinary excretion of phosphate was greater in the VS-105-treated groups than in the paricalcitol-treated groups. Serum parathyroid hormone (PTH) levels decreased and serum fibroblast growth factor-23 (FGF23) levels were elevated after administering paricalcitol and VS-105; however, serum FGF23 levels were remarkably elevated in the paricalcitol-treated groups. Further biochemical analyses revealed that the calcium content of the aorta was higher in the paricalcitol-treated groups than in the VS-105-treated group. VDR and Klotho expression in the kidney was significantly higher in the VS-105-treated groups than in the paricalcitol-treated groups although both agents increased these expressions. Our data suggest that VS-105 had a lesser effect on CKD-MBD than paricalcitol except in the case of serum PTH levels. The mechanism appears to be associated with the difference in VDR and Klotho expression.

Relationship between serum 25-hydroxyvitamin D levels and the SYNTAX score in patients with acute coronary syndrome

OBJECTIVE

The extent of severity and complexity of coronary artery disease (CAD) in patients presenting with ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) and possible correlations between serum 25-hydroxyvitamin D (25(OH)D) have not yet been adequately studied. We evaluated the relationship between 25(OH)D levels and the burden of CAD as assessed by the SYNTAX score (SXscore) in patients with acute coronary syndrome (ACS) including STEMI and NSTEMI.

METHODS

After exclusion, a total of 113 patients who were admitted to our hospital due to ACS and who were referred for undergoing coronary angiography were prospectively included. Their mean age was 63.3±18.5 years, and 80.5% of them were men. In total, 44.2% of the patients had NSTEMI and the remaining had STEMI. Blood samples were drawn at admission to evaluate serum 25(OH)D levels. CAD severity was assessed using the SXscore. Patients were classified as having low (SXscore ≤22) or high (SXscore >22) SXscores. Pearson's and Spearman's correlation coefficients were used to examine the relationship between serum 25(OH)D levels and the SXscore.

RESULTS

25(OH)D levels were significantly lower in the group with a high SXscore than in the group with a low SXscore (21.0±8.0 vs. 16.7±6.8, p=0.005). Correlation analysis showed a significant correlation between 25(OH)D levels and the SXscore. Multiple linear regression (MLR) analysis was used to determine the significance of the relationship between the SXscore and 25(OH)D, parathyroid hormone, and C-reactive protein levels and eGFR. MLR analysis revealed that only 25(OH)D levels (coefficient beta, -0.217, p=0.029) was significantly associated with the severity of CAD.

CONCLUSION

The present study showed that serum 25(OH)D levels were significantly lower in patients with STEMI/NSTEMI and that low serum 25(OH)D levels were significantly correlated with CAD severity and extent.

The Biphasic Effect of Vitamin D on the Musculoskeletal and Cardiovascular System

This narrative review summarizes beneficial and harmful vitamin D effects on the musculoskeletal and cardiovascular system. Special attention is paid to the dose-response relationship of vitamin D with clinical outcomes. In infants and adults, the risk of musculoskeletal diseases is highest at circulating 25-hydroxyvitamin D (25OHD) concentrations below 25 nmol/L and is low if 40-60 nmol/L are achieved. However, evidence is also accumulating that in elderly people the risk of falls and fractures increases again at circulating 25OHD levels > 100 nmol/L. Cohort studies report a progressive increase in cardiovascular disease (CVD) events at 25OHD levels < 50 nmol/L. Nevertheless, meta-analyses of randomized controlled trials suggest only small beneficial effects of vitamin D supplements on surrogate parameters of CVD risk and no reduction in CVD events. Evidence is accumulating for adverse vitamin D effects on CVD outcomes at 25OHD levels > 100 nmol/L, but the threshold may be influenced by the level of physical activity. In conclusion, dose-response relationships indicate deleterious effects on the musculoskeletal system and probably on the cardiovascular system at circulating 25OHD levels < 40-60 nmol/L and >100 nmol/L. Future studies should focus on populations with 25OHD levels < 40 nmol/L and should avoid vitamin D doses achieving 25OHD levels > 100 nmol/L.

Association between serum 25-hydroxyvitamin D levels and carotid atherosclerosis in chronic kidney disease patients

Background

Epidemiological studies have shown an inverse relationship between vitamin D levels and cardiovascular diseases. However, this does not infer a causal relationship between the two. Chronic kidney disease (CKD) patients have a high prevalence of vitamin D deficiency and carotid atherosclerosis. Therefore, in this study we have aimed to determine the association between serum 25-hydroxyvitamin D levels and carotid atherosclerosis in the CKD population.

Methods

100 CKD stage 3–4 patients were included in the study. Direct chemiluminesent immunoassay was used to determine the level of serum 25-hydroxyvitamin D. All subjects underwent a carotid ultrasound to measure common carotid artery intima-media thickness (CCA-IMT) and to assess the presence of carotid plaques or significant stenosis (≥50 %). Vitamin D deficiency was defined as serum 25-hydroxyvitamin D < 25 nmol/L. Abnormal CCA-IMT was defined as CCA-IMT ≥ 0.8 mm. Plaque was defined as a focal structure that encroaches into the arterial lumen of ≥ 0.5 mm or 50 % of the surrounding IMT value. Significant stenosis was defined as peak-systolic velocities ≥ 125 cm/s and end-diastolic velocities ≥ 40 cm/s.

Results

The vitamin D deficiency and non-deficiency groups did not differ significantly in terms of abnormal CCA-IMT (P = 0.443), carotid plaque (P = 0.349), and carotid stenosis (P = 0.554). No significant correlation between serum 25-hydroxyvitamin D levels and CCA-IMT (P = 0.693) was found. On a backward multiple linear regression model, serum 25-hydroxyvitamin D levels was not associated with CCA-IMT, abnormal CCA-IMT, or plaque presence.

Conclusions

No important association between serum 25-hydroxyvitamin levels and carotid atherosclerosis was found in CKD patients.

Serum 25-hydroxyvitamin D as a predictor of hospitalization-free survival in predialysis and dialysis patients with chronic kidney disease: a single-center prospective observational analysis

Background

Vitamin D has pleiotropic effects important for the proper functioning of multiple organ systems. We investigated whether serum 25-hydroxyvitamin D [25(OH)D] levels influenced hospitalization-free survival in patients with chronic kidney disease (CKD).

Methods

In this prospective study, serum levels of 25(OH)D were measured in 210 patients with CKD in the winter of 2009. Data regarding hospitalizations were collected over the subsequent 3 years.

Results

Vitamin D deficiency, as defined by a serum 25(OH)D level below 15 ng/mL, was observed in 76.7% of the patients. The mean 25(OH)D serum level was 13.6 ± 7.8 ng/mL in predialysis patients (n = 62) and 11.3 ± 6.7 ng/mL in dialysis patients (n = 148). During the follow-up, 107 patients (28 predialysis and 79 dialysis) were hospitalized because of infectious (33.6%) or cardiovascular diseases (23.4%). Predialysis and dialysis groups were divided into 2 subgroups based on the median 25(OH)D serum level. Kaplan–Meier analysis revealed that the risk of hospitalization was significantly lower in both predialysis and dialysis patients with above-median serum 25(OH)D levels (log-rank test; P = 0.043 and 0.002, respectively). Multivariate Cox proportional hazards models also demonstrated that the risk of hospitalization was significantly lower for patients with higher serum 25(OH)D levels in both the predialysis (hazard ratio, 0.963; 95% confidence interval, 0.93–0.99) and dialysis groups (hazard ratio, 0.955; 95% confidence interval, 0.91–0.99).

Conclusion

A lower serum 25(OH)D level predicted poorer hospitalization-free survival in both predialysis and dialysis CKD patients.

Vitamin D and the skin: Focus on a complex relationship: A review

The "sunshine" vitamin is a hot topic that attracted ample attention over the past decades, specially that a considerable proportion of the worldwide population are deficient in this essential nutrient. Vitamin D was primarily acknowledged for its importance in bone formation, however; increasing evidence point to its interference with the proper function of nearly every tissue in our bodies including brain, heart, muscles, immune system and skin. Thereby its deficiency has been incriminated in a long panel of diseases including cancers, autoimmune diseases, cardiovascular and neurological disorders. Its involvement in the pathogenesis of different dermatological diseases is no exception and has been the subject of much research over the recent years. In the current review, we will throw light on this highly disputed vitamin that is creating a significant concern from a dermatological perspective. Furthermore, the consequences of its deficiency on the skin will be in focus.

Is there any correlation between vitamin D insufficiency and diabetic retinopathy?

AIM

To determine a relation between vitamin D level, which is an inhibitor of angiogenesis, and diabetic retinopathy and its risk factors.

METHODS

In a clinic-based cross sectional study two hundred and thirty-five type 2 diabetic patients older than 20y were selected. Patients were classified according to ophthalmologic examination as following: no diabetic retinopathy (NDR) (n=153), non-proliferative diabetic retinopathy (NPDR) (n=64) and proliferative diabetic retinopathy (PDR) (n=18). Study subjects were tested for fasting blood glucose, glycated hemoglobin A1C (HbA1C), lipid profile, microalbuminuria, HsCRP, IGF1, insulin (in patients without history of insulin taking) and 25 hydroxy vitamin D [25 (OH) D] levels. Vitamin D insufficiency was defined according to 25 (OH) D level less than 30 ng/mL. The relationship between diabetic retinopathy and serum 25 (OH) D insufficiency was evaluated.

RESULTS

The prevalence of diabetic retinopathy was 34.8% in our patients. Long duration of diabetes, hypertension, poor glycemic control, diabetic nephropathy, hyperinsulinemia and insulin resistance were risk factors for diabetic retinopathy but 25 (OH) D level was not significant different between NDR, NPDR and PDR groups. Correlation between 25 (OH) D level and other known risk factors of diabetic retinopathy was not significant.

CONCLUSION

This study did not find any association between diabetic retinopathy and its severity and vitamin D insufficiency. Vitamin D insufficiency is not related to risk factors of diabetic retinopathy.

Is vitamin d deficiency a new risk factor for cardiovascular disease?

The role of vitamin D in the regulation of bone metabolism has been well established. However, in recent years, many studies have demonstrated that its role extends far beyond bone health. Growing evidence has shown a strong association between vitamin D deficiency and hypertension, metabolic syndrome, diabetes mellitus and atherosclerosis. The mechanisms by which vitamin D exerts its cardiovascular protective effects are still not completely understood, but there is evidence that it participates in the regulation of renin-angiotensin system and the mechanisms of insulin sensitivity and activity of inflammatory cytokines, besides its direct cardiovascular actions. In this review, several studies linking vitamin D deficiency with cardiometabolic risk as well as small randomized trials that have evaluated the cardiovascular effects of its supplementation are presented. However, large randomized placebo-controlled studies are still needed before we can definitively establish the role of vitamin D supplementation in the prevention and control of cardiovascular disease.

Desphospho-uncarboxylated matrix Gla-protein is associated with mortality risk in patients with chronic stable vascular disease

BACKGROUND

Vitamin K is the essential co-factor for activation of matrix Gla-protein (MGP), the natural inhibitor of tissue calcification. Biologically inactive, desphospho-uncarboxylated MGP (dp-ucMGP) is a marker of vascular vitamin K status and is described to predict mortality in patients with heart failure and aortic stenosis. We hypothesized that increased dp-ucMGP might be associated with mortality risk in clinically stable patients with chronic vascular disease.

MATERIALS AND METHODS

We examined 799 patients (mean age 65.1 ± 9.3 years) who suffered from myocardial infarction, coronary revascularization or first ischemic stroke (pooled Czech samples of EUROASPIRE III and EUROASPIRE-stroke surveys), and followed them in a prospective cohort study. To estimate the 5-year all-cause and cardiovascular mortality we ascertained vital status and declared cause of death. Circulating dp-ucMGP and desphospho-carboxylated MGP (dp-cMGP) were measured by ELISA methods (IDS and VitaK).

RESULTS

During a median follow-up of 2050 days (5.6 years) 159 patients died. In the fully adjusted multivariate Cox proportional hazard model, the patients in the highest quartile of dp-ucMGP (≥ 977 pmol/L) had higher risk of all-cause and cardiovascular 5-year mortality [HRR 1.89 (95% CI, 1.32-2.72) and 1.88 (95% CI, 1.22-2.90)], respectively. Corresponding HRR for dp-cMGP were 1.76 (95% CI, 1.18-2.61) and 1.79 (95% CI, 1.12-2.57).

CONCLUSIONS

In patients with overt vascular disease, circulating dp-ucMGP and dp-cMGP were independently associated with the risk of all-cause and cardiovascular mortality. Since published results are conflicting regarding the dp-cMGP, we propose only circulating dp-ucMGP as a potential biomarker for assessment of additive cardiovascular risk.

Dietary vitamin D inadequacy accelerates calcification and osteoblast-like cell formation in the vascular system of LDL receptor knockout and wild-type mice

Vitamin D insufficiency is highly associated with cardiovascular morbidity and mortality. We have demonstrated enhanced vascular calcification in LDL receptor knockout (LDLR(-/-)) mice fed a diet low in vitamin D. This study aimed to investigate the impact of a diet low in vitamin D on vascular calcification in wild-type (WT) mice lacking atherosclerotic plaques and the effects of a persistent and discontinuous vitamin D insufficiency on atherosclerotic plaque composition in LDLR(-/-) mice. The study was performed with 4-wk-old male WT and LDLR(-/-) mice that were fed a normal calcium/phosphate Western diet (210 g/kg fat, 1.5 g/kg cholesterol) containing either adequate (+D; 1000 IU/kg) or low (-D; 50 IU/kg) amounts of vitamin D-3 for 16 wk. Four groups of LDLR(-/-) mice received 1 of the 2 diets for additional 16 wk (total 32 wk) and were compared with mice fed the diets for only 16 wk. WT and LDLR(-/-) mice that were fed the -D diet for 16 wk tended to develop more calcified spots in the aortic valve than mice fed the +D diet (+50% and +56%, respectively; P < 0.10). In LDLR(-/-) mice, the extent of calcification increased from week 16 to week 32 and was higher in the -D than in the +D group (P < 0.05). The calcification, owing to the -D diet, was accompanied by highly expressed osteoblast differentiation factors, indicating a transdifferentiation of vascular cells to osteoblast-like cells. Feeding the +D diet subsequent to the -D diet reduced the vascular calcification (P < 0.05). LDLR(-/-) mice fed the -D diet for 32 wk had higher plaque lipid depositions (+48%, P < 0.05) and a higher expression of cluster of differentiation 68 (+31%, P < 0.05) and tumor necrosis factor α (+134%, P < 0.001) than the +D group. Collectively, the findings imply low vitamin D status as a causal factor for vascular calcification and atherosclerosis.

Vitamin D Metabolites; Protective versus Toxic Properties: Molecular and Cellular Perspectives

Vitamin D plays an essential role in bone metabolism. The discovery that the vitamin D receptor (VDR), a member of the nuclear receptor superfamily, is expressed in most tissues led researchers to investigate other biological actions of vitamin D. These effects were found to include anti-inflammatory effects and anti-atherogenesis, decreased renin activity and biosynthesis, induction of cell differentiation, inhibition of cell growth, and immunomodulation. In spite of the plethora of evidence on the protective effects of vitamin D, the reports on its intoxication still are considerably few. Therefore, in this review we aim to summarize the molecular and cellular bases of the protect-ive and toxic vitamin D actions that are mediated mostly by VDR. This review will also shed light on vitamin D metabolites other than the active metabolite calcitriol and particularly 25-hydroxy vitamin D (25(OH)D), putting emphasis on its magnifying role in vitamin D intoxication. One of the important themes we discuss is defining serum levels of beneficial or toxic effects of other exogenous vitamin D administration and its impact on 25(OH)D serum levels in animals and human subjects.

Association between vitamin D receptor activator and the risk of infection-related hospitalizations among incident hemodialysis patients: a nested case-control study

BACKGROUND

Patients suffering from chronic kidney disease are at greater risk of developing infection than the normal population, and infections are the second cause of mortality after cardiovascular complications in this population. Some reports suggest that the intake of active vitamin D might be beneficial to prevent infections. Therefore, we aimed to determine if the oral intake of vitamin D receptor activator (VDRA) is associated with a lower risk of infection-related hospitalization (IRH) among incident chronic hemodialysis patients.

METHODS

We conducted a nested case-control study in a cohort of 4933 patients initiating chronic hemodialysis between 1 January 2001 and 31 December 2007 in Quebec, Canada, using administrative databases. We identified cases of hospital admission indicating an infection as main diagnosis on the hospital's discharge sheet. Up to 10 controls were randomly selected for each case. Association between oral VDRA use and risk of IRH was estimated using conditional logistic regression.

RESULTS

We identified 1136 cases of IRH and 10396 controls during the study period. The intake of VDRA was not associated with the risk of being hospitalized due to an infection (odds ratio [OR], 1.07; 95% confidence interval [CI], 0.95-1.20). Using the prior 6-month cumulative dose of VDRA, we also found that a cumulative VDRA dose of less than 45 mcg (OR, 1.05; 95%CI, 0.92-1.19) or greater than 45 mcg (OR, 1.15; 95%CI, 0.96-1.36) was not associated with the IRH risk.

CONCLUSIONS

The oral intake of VDRA was not associated with the risk of IRH in incident hemodialysis patients.

The pleiotropic effect of vitamin d

The novel roles of vitamin D were discovered and valued in this century. In addition to the maintenance of calcium and phosphorus balance, vitamin D regulates the function of the kidneys, heart, and immune system. Moreover, its anti-inflammatory, antiapoptotic, and antifibrotic roles have gained considerable attention. Vitamin D is also important for the maintenance of homeostasis by regulation of hormone secretion, cell proliferation, and differentiation. This paper will review these pleiotropic functions of vitamin D.

High prevalence of vertebral fractures assessed by quantitative morphometry in hemodialysis patients, strongly associated with vascular calcifications

Few studies have provided information on the prevalence of vertebral fractures (VFs) and their risk factors in hemodialysis patients. A multicenter, cross-sectional, observational study was carried out to assess the prevalence of VFs and vascular calcifications (VCs) in 387 hemodialysis patients (mean age 64.2 ± 14.1 years, 63 % males) and in a control group of 51 osteoporotic subjects. Biochemical tests included 25(OH) vitamin D, bone Gla protein (total and undercarboxylated), and total matrix Gla protein. Vertebral quantitative morphometry was carried out centrally for the detection of VF, defined as reduction by ≥20 % of one of the vertebral body dimensions. In the same radiograph, aortic and iliac VC scores were calculated. Prevalence of VF was 55.3 % in hemodialysis patients and 51.0 % in the control group. Multivariate analysis disclosed that male gender (59.8 vs. 47.6 %, p = 0.02; OR = 1.78, 95 % CI 1.15-2.75) and age (mean ± SD 66.7 ± 13.1 vs. 61.0 ± 14.7 years, p < 0.001; OR = 1.03, 95 % CI 1.01-1.05) were significantly associated with VF. The prevalence of aortic VC was significantly higher in hemodialysis patients than in controls (80.6 vs. 68.4 %, p = 0.001). The factors with the strongest association with VC, apart from atrial fibrillation, were serum 25(OH)vitamin D levels below 29 ng/mL for aortic VC (OR = 1.85, 95 % CI 1.04-3.29) and VF both for aortic (OR = 1.77, 95 % CI 1.00-3.14) and iliac (OR = 1.96, 95 % CI 1.27-3.04) VC. In conclusion, the prevalence of VF, especially in males, and VC, in both genders, is high in hemodialysis patients. VF is associated with VC. Vitamin D deficiency is also associated with VC. Further longitudinal studies are warranted to investigate fractures in renal patients.

The association of 25(OH)D with blood pressure, pulse pressure and carotid-radial pulse wave velocity in African women

High susceptibility of the African population to develop cardiovascular disease obliges us to investigate possible contributing risk factors. Our aim was to determine whether low 25(OH)D status is associated with increased blood pressure and carotid-radial pulse wave velocity in black South African women. We studied 291 urban women (mean age: 57.56±9.00 yrs.). 25(OH)D status was determined by serum 25(OH)D levels. Women were stratified into sufficient (>30 ng/ml), and insufficient/deficient (<30 ng/ml) groups. Cardiovascular variables were compared between groups. Women with low 25(OH)D levels had significantly higher SBP (150.8±27.1 vs. 137.6±21.0), DBP (94.7±14.5 vs. 89.3±12.3) and PP (53.15(50.7;55.7) vs. 46.3(29.4;84.6)) compared to women with sufficient levels. No significant difference was observed with regards to c-rPWV. ANCOVA analyses still revealed significant differences between the two groups with regards to SBP, DBP as well as PP. Partial correlations revealed significant inverse association between SBP and 25(OH)D (p = .04;r = −.12). Women with low 25(OH)D levels were ∼2 times more likely to have high SBP (95% CI: 3.23;1.05). To conclude, women with deficient/insufficient 25(OH)D had significantly higher SBP compared to women with a sufficient 25(OH) status.

Vitamin D status and coronary flow reserve measured by positron emission tomography: a co-twin control study

CONTEXT

Vitamin D insufficiency is associated with increased cardiovascular events in the general population. Additionally, low serum 25-hydroxyvitamin D [25(OH)D] is associated with endothelial dysfunction and arterial stiffness. However, little is known about the association between serum 25(OH)D level and myocardial blood flow.

OBJECTIVE

Our objective was to examine the association between serum 25(OH)D levels and coronary flow reserve (CFR) measured by (13)N-positron emission tomography in asymptomatic middle-aged male twins.

DESIGN

The Emory Twin Study is a cross-sectional study of soldiers from the Vietnam Era Registry.

SETTING

The study was conducted at the General Clinical Research Center, Emory University, Atlanta, GA.

PARTICIPANTS

A total of 368 middle-aged male twins were enrolled for the study. Serum 25(OH)D levels were measured in all subjects and classified as vitamin D insufficiency [25(OH)D <30 ng/ml] or sufficiency [25(OH)D ≥30 ng/ml]. Positron emission tomography with [(13)N]ammonia was used to evaluate myocardial blood flow at rest and after adenosine stress. CFR was measured as the ratio of maximum to rest myocardial blood flow.

MAIN OUTCOME MEASURE

Primary outcome was CFR measurement.

RESULTS

Mean overall serum 25(OH)D concentration was 37.0 ± 21.4 ng/ml; 167 twins (45%) were vitamin D insufficient. CFR was significantly lower in subjects with vitamin D insufficiency compared with subjects with vitamin D sufficiency (2.41 vs. 2.64; P = 0.007), even after adjustment for traditional cardiovascular risk factors, serum PTH, calcium, and phosphorus levels, and season. An abnormal CFR (CFR <2) was more prevalent in subjects with vitamin D insufficiency than with vitamin D sufficiency (31 vs. 20%; P = 0.03). In addition, in vitamin D status-discordant twin pairs, CFR was significantly lower in the vitamin D-insufficient twin than in the vitamin D-sufficient co-twin (2.35 vs. 2.58; P = 0.037).

CONCLUSION

Vitamin D insufficiency is associated with lower CFR in men. This association may help explain some of the increased cardiovascular risk reported in individuals with vitamin D insufficiency.

Protective cardiovascular and renal actions of vitamin D and estrogen

Both basic science and clinical studies support the concept that vitamin D deficiency is involved in the pathogenesis of cardiovascular and renal diseases through its association with diabetes, obesity, and hypertension. Understanding the underlying mechanisms may provide a rationale for advocating adequate intake of vitamin D and calcium in all populations, thereby preventing many chronic diseases. This review explores the effect of vitamin D deficiency in the development of cardiovascular and renal diseases, and the role of vitamin D supplementation on cardiovascular outcomes. In addition, it highlights the importance of vitamin D intake for the prevention of adverse long-term health consequences, and in ways to facilitate the management of cardiovascular disease. This is particularly true for African American and postmenopausal women, who are at added risk for cardiovascular disease. We suggest that the negative cardiovascular effects of low vitamin D in postmenopausal women could be improved by a combined treatment of vitamin D and sex steroids acting through endothelium-dependent and/or -independent mechanisms, resulting in the generation of nitric oxide and calcitonin gene-related peptide (CGRP).

Vitamin d and cardiovascular disease

OPINION STATEMENT

Vitamin D has received widespread attention for its potential role in preventing cardiovascular disease (CVD) and type 2 diabetes mellitus. Several epidemiological studies have suggested that individuals with low blood levels of vitamin D have increased risks of heart disease, stroke, hypertension, and diabetes. Yet, the revised 2011 Institute of Medicine report for intake of calcium and vitamin D, which was guided by skeletal health alone, concluded that the evidence that vitamin D prevents CVD, diabetes, or other cardiometabolic outcomes was inconsistent and inconclusive and did not meet criteria for establishing a cause and effect relationship [1•, 2]. This finding was consistent with an earlier systematic review conducted by the Agency for Healthcare Research and Quality (AHRQ) in 2009 [3•]. Ongoing clinical trials seek to address the effects of vitamin D supplementation on CVD and other nonskeletal outcomes.