Vitamin D insufficiency is associated with impaired vascular endothelial and smooth muscle function and hypertension in young rats

What is more damaging to vascular endothelial function: Diabetes, age, high BMI, or all of the above?

BACKGROUND

It is well established that there is a reduction in the skin blood flow (SBF) in response to heat with age and diabetes. While it is known that high BMI creates a stress on the cardiovascular system and increases the risk of all cause of morbidity and mortality, little is known of the effect of high BMI on SBF response to heat. Since diabetes is associated with age and a higher BMI, the interrelationship between age, BMI and SBF needs to be investigated to better understand the contribution diabetes alone has to endothelial impairment.

MATERIAL AND METHODS

This study examined the SBF to heat in young and old people with low and high BMI and people with diabetes with high BMI to determine the contribution these variables have on SBF. Subjects were ten young and older people with BMI <20 and ten young and older people with BMI >20 and ten subjects with diabetes with BMI >20. The SBF response, above the quadriceps, was determined during a 6 minutes exposure to heat at 44°C.

RESULTS

Even in young people, SBF after the stress of heat exposure was reduced in subjects with a high BMI. The effect of BMI was greatest in young people and lowest in older people and people with diabetes; in people with diabetes, BMI was a more significant variable than diabetes in causing impairment of blood flow to heat. BMI, for example, was responsible for 49% of the reduction in blood flow after stress heat exposure (R=-0.7) while ageing only accounted for 16% of the blood flow reduction (R=-0.397).

CONCLUSIONS

These results would suggest the importance of keeping BMI low not only in people with diabetes to minimize further circulatory vascular damage, but also in young people to diminish long term circulatory vascular compromise.

Roles of vitamin D in amyotrophic lateral sclerosis: possible genetic and cellular signaling mechanisms

Evidence suggests that there are aberrations in the vitamin D-endocrine system in subjects with amyotrophic lateral sclerosis (ALS). Here, we review the relationship between vitamin D and ALS. Vitamin D deficiency was reported in patients with ALS. Dietary vitamin D₃ supplementation improves functional capacity in the G93A transgenic mouse model of ALS. Genetic studies have provided an opportunity to identify the proteins that link vitamin D to ALS pathology, including major histocompatibility complex (MHC) class II molecules, toll-like receptors, poly(ADP-ribose) polymerase-1, heme oxygenase-1, and calcium-binding proteins, as well as the reduced form of nicotinamide adenine dinucleotide phosphate. Vitamin D also exerts its effect on ALS through cell-signaling mechanisms, including glutamate, matrix metalloproteinases, mitogen-activated protein kinase pathways, the Wnt/β-catenin signaling pathway, prostaglandins, reactive oxygen species, and nitric oxide synthase.

In conclusion, vitamin D may have a role in ALS. Further investigation of vitamin D in ALS patients is needed.

Vitamin D, arterial hypertension & cerebrovascular disease

Vitamin D is mainly derived from endogenous ultraviolet-B induced vitamin D synthesis in the skin, and the current high prevalence of vitamin D deficiency can, therefore, largely be attributed to lifestyle related low sunlight exposure. Regulation of bone and mineral metabolism is a classic vitamin D effect, but the identification of the vitamin D receptor (VDR) in almost all human cells suggests a role for vitamin D also in extra-skeletal diseases. Experimental studies demonstrated several antihypertensive and vascular protective effects of vitamin D, such as suppression of the renin angiotensin aldosterone system, beneficial modulation of classic cardiovascular risk factors, and anti-atherosclerotic properties including improvements of endothelial function. Additional neuroprotective actions of vitamin D have also been reported. In line with this, epidemiological studies have largely shown that vitamin D deficiency is an independent risk factor for arterial hypertension and strokes. Data from randomized controlled trials (RCTs) are, however, limited and less promising, with currently no confirmation that vitamin D reduces stroke incidence. Whereas some RCTs suggest that vitamin D supplementation might modestly reduce blood pressure, this has not been consistently observed in all studies. It is, therefore, premature to recommend vitamin D supplementation for the prevention and treatment of arterial hypertension and stroke. Nevertheless, the fact that patients with arterial hypertension and cerebrovascular disease are at a relatively high risk of vitamin D deficiency, and therewith associated musculoskeletal diseases can serve as a rationale for the evaluation, prevention and treatment of vitamin D deficiency in these 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.

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).

Pharmacological reactivity of resistance vessels in a rat PCOS model - vascular effects of parallel vitamin D₃ treatment

The aim of this study was to clarify the effects of dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS) on pharmacological reactivity of a resistance vessel in a rat model and the possible modulatory role of 1,25-(OH)₂-cholecalciferol (vitamin D₃). The PCOS model was induced in adolescent female Wistar rats by a 10-week DHT treatment. Norepinephrine induced contractility and acetylcholine relaxation were tested in arterioles by pressure arteriography in control as well as DHT- and DHT plus vitamin D₃-treated (DHT+D3) animals. Decreased vasoconstriction and dilatation were detected after DHT treatment. Concomitant vitamin D₃ treatment increased the contractile response and resulted in more relaxed vessels. Endothelial dilation tested with acetylcholine was lower after DHT treatment, this effect was not depend on vitamin D₃ supplementation. In conclusion, hyperandrogenic state resulted in reduced endothelium- and smooth muscle-dependent vasorelaxation and constriction with a complete loss of nitric oxide (NO)-dependent relaxation compared with controls. These alterations caused by chronic DHT treatment were partially reversed by concomitant vitamin D₃ administration.

Arteriolar biomechanics in a rat polycystic ovary syndrome model - effects of parallel vitamin D3 treatment

To clarify the effects of dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS) on arteriolar biomechanics in a rat model and the possible modulatory role of vitamin D3.

METHODS AND RESULTS

The PCOS model was induced in female Wistar rats by ten-weeks DHT treatment. Arteriolar biomechanics was tested in arterioles by pressure arteriography in control as well as DHT- and DHT with vitamin D3-treated animals in contracted and passive conditions. Increased wall stress and distensibility as well as increased vascular lumen were detected after DHT treatment. Concomitant vitamin D3 treatment lowered the mechanical load of the arterioles and restored the vascular diameter.

CONCLUSION

The hyperandrogenic state resulted in more rigid, less flexible arteriolar walls with increased vascular lumen compared with controls. DHT treatment caused eutrophic remodelling of gracilis arteriole. These prehypertensive alterations caused by chronic DHT treatment were mostly reversed by concomitant vitamin D3 administration.

Vitamin D, metabolic dyslipidemia, and metabolic syndrome in rheumatoid arthritis

PURPOSE

Vitamin D deficiency is a potential risk factor for cardiometabolic disease. We investigated the associations between vitamin D and dyslipidemia and the metabolic syndrome in patients with rheumatoid arthritis, a group at high risk for cardiovascular disease.

METHODS

Serum 25(OH)vitamin D and lipoprotein levels were measured at baseline in a random sample of 499 participants, ages 18-85 years, enrolled in a randomized trial of golimumab (GOlimumab Before Employing methotrexate as the First-line Option in the treatment of Rheumatoid arthritis of Early onset or GO-BEFORE Trial). Participants had rheumatoid arthritis with active disease, and were naïve to methotrexate and biologic therapies. Multivariable linear regression was performed to assess associations between vitamin D levels and lipoprotein fractions. Multivariable logistic regression was performed to determine the odds of hyperlipidemia and the metabolic syndrome in participants with vitamin D deficiency (<20 ng/mL).

RESULTS

In multivariable linear regression, vitamin D levels (per 10 ng/mL) were associated inversely with low-density lipoprotein (β: -0.029 [-0.049, -0.0091], P=.004) and triglyceride (β: -0.094 [-0.15, -0.039] P=.001) levels, adjusted for demographic, cardiovascular, and disease-specific variables. Vitamin D and high-density lipoprotein levels were not associated in univariate or multivariate analyses. Vitamin D deficiency was associated independently with an increased odds of hyperlipidemia (odds ratio 1.72; 95% confidence interval, 1.10-2.45; P=.014) and metabolic syndrome (odds ratio 3.45; 95% confidence interval, 1.75-6.80; P <.001) in adjusted models.

CONCLUSIONS

In conclusion, vitamin D deficiency was associated with the metabolic syndrome and dyslipidemia in rheumatoid arthritis, suggesting a potential role in cardiovascular disease risk. Large-scale, prospective studies are needed to determine if vitamin D supplementation improves lipoprotein levels and reduces cardiovascular risk in rheumatoid arthritis.

Does vitamin D deficiency contribute to erectile dysfunction?

Erectile dysfunction (ED) is a multifactorial disease, and its causes can be neurogenic, psychogenic, hormonal and vascular. ED is often an important indicator of cardiovascular disease (CVD) and a powerful early marker for asymptomatic CVD. Erection is a vascular event, and ED is often a vascular disease caused by endothelial damage and subsequent inhibition of vasodilation. We show here that risk factors associated with a higher CVD risk also associate with a higher ED risk. Such factors include diabetes mellitus, hypertension, arterial calcification and Inflammation in the vascular endothelium. Vitamin D deficiency is one of several dynamics that associates with increased CVD risk, but to our knowledge, it has not been studied as a possible contributor to ED. Here we examine research linking ED and CVD and discuss how vitamin D influences CVD and its classic risk factors-factors that also associate to increased ED risk. We also summarize research indicating that vitamin D associates with reduced risk of several nonvascular contributing factors for ED. We conclude that VDD contributes to ED. This hypothesis should be tested through observational and intervention studies.

Vitamin D deficiency is associated with silent coronary artery disease in cardiovascularly asymptomatic African Americans with HIV infection

BACKGROUND

Growing evidence suggests that vitamin D deficiency Is associated with clinical coronary artery disease (CAD). The relationship between vitamin D deficiency and subclinical CAD in HIV-infected individuals is not well-characterized.

METHODS

Computed tomographic (CT) coronary angiography was performed using contrast-enhanced 64-slice multidetector CT imaging, and vitamin D levels and the presence of traditional and novel risk factor for CAD were obtained in 674 HIV-infected African American (AA) participants aged 25-54 years in Baltimore, MD, without symptoms/clinical evidence of CAD.

RESULTS

The prevalence of vitamin D deficiency (25-hydroxy vitamin D <10 ng/mL) was 20.0% (95% confidence interval [CI], 16.9-23.1). Significant (≥50%) coronary stenosis was present in 64 (9.5%) of 674 participants. Multiple logistic regression analysis revealed that male gender (adjusted odds ratio [OR], 2.19; 95% CI, 1.17-4.10), diastolic BP ≥85 mmHg (adjusted OR: 1.94, 95% CI: 1.02 -3.68), low-density lipoprotein cholesterol ≥100 mg/dL (adjusted OR, 1.95; 95% CI, 1.13-3.36), cocaine use for ≥15 years (adjusted OR, 1.77; 95% CI, 1.01-3.10), use of antiretroviral therapies for ≥6 months (adjusted OR, 2.26; 95% CI, 1.17-4.36), year of enrollment after 2005 (adjusted ORs for 2006-2007, 2008-2009, and 2010 were 0.32 [95% CI, 0.13-0.76], 0.26 [95% CI, 0.12-0.56], and 0.32 (95% CI, 0.15-0.65], respectively), and vitamin D deficiency (adjusted OR, 2.28; 95% CI, 1.23-4.21) were independently associated with significant coronary stenosis.

CONCLUSIONS

Both vitamin D deficiency and silent CAD are prevalent in HIV-infected AAs. In addition to management of traditional CAD risk factors and substance abuse, vitamin D deficiency should be evaluated in HIV-infected AAs. These data support the conduct of a prospective trial of vitamin D in this high-risk patient population.

Cardiorenal syndrome and vitamin D receptor activation in chronic kidney disease

Cardiorenal syndrome (CRS) refers to a constellation of conditions whereby heart and kidney diseases are pathophysiologically connected. For clinical purposes, it would be more appropriate to emphasize the pathophysiological pathways to classify CRS into: (1) hemodynamic, (2) atherosclerotic, (3) uremic, (4) neurohumoral, (5) anemic–hematologic, (6) inflammatory–oxidative, (7) vitamin D receptor (VDR) and/or FGF23-, and (8) multifactorial CRS. In recent years, there have been a preponderance data indicating that vitamin D and VDR play an important role in the combination of renal and cardiac diseases. This review focuses on some important findings about VDR activation and its role in CRS, which exists frequently in chronic kidney disease patients and is a main cause of morbidity and mortality. Pathophysiological pathways related to suboptimal or defective VDR activation may play a role in causing or aggravating CRS. VDR activation using newer agents including vitamin D mimetics (such as paricalcitol and maxacalcitol) are promising agents, which may be related to their selectivity in activating VDR by means of attracting different post-D-complex cofactors. Some, but not all, studies have confirmed the survival advantages of D-mimetics as compared to non-selective VDR activators. Higher doses of D-mimetic per unit of parathyroid hormone (paricalcitol to parathyroid hormone ratio) is associated with greater survival, and the survival advantages of African American dialysis patients could be explained by higher doses of paricalcitol (>10 μg/week). More studies are needed to verify these data and to explore additional avenues for CRS management via modulating VDR pathway.