High-Dose versus Low-Dose Vitamin D Supplementation and Arterial Stiffness among Individuals with Prehypertension and Vitamin D Deficiency

Can we reverse arterial stiffness by intervening on CKD-MBD biomarkers?

The increased cardiovascular risk of chronic kidney disease may in part be the consequence of arterial stiffness, a typical feature of kidney failure. Deranged homeostasis of minerals and hormones involved (CKD-MBD), are also strongly associated with this increased risk. It is well established that CKD-MBD is a main driver of vascular calcification, which in turn worsens arterial stiffness. However, there are other contributors to arterial stiffness in CKD than calcification. An overlooked possibility is that CKD-MBD may have detrimental effects on this potentially better modifiable component of arterial stiffness. In this review, the individual contributions of short-term changes in calcium, phosphate, PTH, vitamin D, magnesium, and FGF23 to arterial stiffness, in most studies assessed as pulse wave velocity, is summarized. Indeed, there is evidence from both observational studies and interventional trials that higher calcium concentrations can worsen arterial stiffness. This, however, has not been shown for phosphate, and it seems unlikely that, apart from being a contributor to vascular calcification and having effects on the microcirculation, phosphate has no acute effect on large artery stiffness. Several interventional studies, both by infusing PTH and by abrupt lowering PTH by calcimimetics or surgery, virtually ruled out direct effects on large artery stiffness. A well-designed trial using both active and nutritional vitamin D as intervention found a beneficial effect for the latter. Unfortunately, the study had a baseline imbalance and other studies did not support its finding. Both magnesium and FGF23 do not seem do modify central arterial stiffness.

Effects of Vitamin D Supplementation on Cardiovascular and Glycemic Biomarkers

Background Experimental and observational studies have suggested a link between vitamin D and cardiovascular and metabolic disease, but this has not been confirmed in randomized controlled trials. We sought to determine whether vitamin D supplementation reduces biomarkers of insulin resistance, inflammation, neurohormonal activation, and lipids. Methods and Results This was a prespecified, secondary analysis of the DAYLIGHT (Vitamin D Therapy in Individuals at High Risk of Hypertension) randomized controlled trial. We measured circulating homeostatic model assessment of insulin resistance, hs-CRP (high-sensitivity C-reactive protein), N-terminal pro-B-type natriuretic peptide, renin, aldosterone, and lipids at baseline and at 6 months in 289 individuals with low vitamin D status (25-hydroxyvitamin-D [25-OH-D] ≤25 ng/mL) receiving low-dose (400 IU/d) versus high-dose (4000 IU/d) vitamin D3 for 6 months. A meta-analysis of randomized controlled trials reporting biomarker changes after vitamin D supplementation was then performed. Levels of 25-OH-D increased in the high-dose relative to the low-dose vitamin D group (+15.5 versus +4.6 ng/mL, P<0.001). Changes in biomarkers of glycemia, inflammation, and neurohormonal activation did not differ by dose. Lipids did not differ between groups, other than triglycerides, which increased in the high-dose compared with the low-dose group (+11.3 versus -6.2 mg/dL, P<0.001). The meta-analysis showed potential modest decreases in homeostatic model assessment of insulin resistance and hs-CRP, but no changes in low-density lipoprotein, after vitamin D supplementation compared with control groups. Conclusions In the DAYLIGHT randomized controlled trial, high-dose vitamin D supplementation did not improve biomarkers of glycemia, inflammation, neurohormonal activation, or lipids. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01240512.

Role of Changes in State of Bound Water and Tissue Stiffness in Development of Age-Related Diseases

An essential effect of environmental stiffness on biological processes in cells at present is generally accepted. An increase in arterial stiffness with advanced age has been reported in many publications. The aim of the present review is to summarize current information about possible chemical reactions and physical processes that lead to tissue stiffening and result in age-related diseases in order to find methods that can prevent or retard time-dependent tissue stiffening. The analysis of published data shows that bound water acts as a plasticizer of biological tissues, a decrease in bound water content results in an increase in biological tissue stiffness, and increased tissue stiffness leads to NF-kB activation and triggered actin polymerization-NF-kB activation is associated with age-related diseases. It can be suggested that changes in bound water content through changing tissue stiffness can affect cellular processes and the development of pathologies related to aging. Both age-related diseases and COVID-19 may be associated with tight-junction disruption and increased tissue stiffness and permeability.

The Effect of Vitamin Supplementation on Subclinical Atherosclerosis in Patients without Manifest Cardiovascular Diseases: Never-ending Hope or Underestimated Effect?

Micronutrients, especially vitamins, play an important role in the evolution of cardiovascular diseases (CVD). It has been speculated that additional intake of vitamins may reduce the CVD burden by acting on the inflammatory and oxidative response starting from early stages of atherosclerosis, when the vascular impairment might still be reversible or, at least, slowed down. The current review assesses the role of major vitamins on subclinical atherosclerosis process and the potential clinical implications in patients without CVD. We have comprehensively examined the literature data for the major vitamins: A, B group, C, D, and E, respectively. Most data are based on vitamin E, D and C supplementation, while vitamins A and B have been scarcely examined for the subclinical atherosclerosis action. Though the fundamental premise was optimistic, the up-to-date trials with vitamin supplementation revealed divergent results on subclinical atherosclerosis improvement, both in healthy subjects and patients with CVD, while the long-term effect seems minimal. Thus, there are no conclusive data on the prevention and progression of atherosclerosis based on vitamin supplementation. However, given their enormous potential, future trials are certainly needed for a more tailored CVD prevention focusing on early stages as subclinical atherosclerosis.

Links between High-Sensitivity C-Reactive Protein and Pulse Wave Analysis in Middle-Aged Patients with Hypertension and High Normal Blood Pressure

Arterial stiffness and arterial age provide valuable prognostic cardiovascular information. The present study aimed at assessing the levels of vitamin D, high-sensitivity C-reactive protein (hsCRP), low-density lipoprotein cholesterol (LDL), and oxidized LDL (oxLDL) in a group of middle-aged hypertensive patients and their relationship with pulse wave velocity (PWV), central blood pressure, and early arterial aging (EAA), respectively. A total of 56 patients, aged 48 ± 6 years, 57% males, with hypertension and high normal blood pressure (HNBP), were investigated using a Mobile-O-Graph, to assess central and peripheral blood pressure, PWV, and arterial age. Additionally, hsCRP, LDL, oxLDL, and 25-hydroxy vitamin D3 were assessed. PWV, 25-hydroxy vitamin D3, hsCRP, oxLDL, and LDL levels were 7.26 ± 0.69 m/s, 25.99 ± 11.17 microg/l, 0.48 ± 0.44 mg/dl, 261.37 ± 421 ng/ml, and 145.73 ± 39.53 mg/dl, respectively. Significant correlations were obtained between oxLDL and pulse pressure amplification (rS = -0.347, p = 0.028) and between hsCRP and LDL levels with PWV and EAA, respectively. ROC curve analysis revealed that hsCRP is a sensitive and specific predictor of EAA and increased PWV values. Concluding, vitamin D deficiency and increased hsCRP and LDL values are very common, and high oxidized LDL is related to pulse pressure amplification in patients with elevated blood pressure. Vitamin D level and high-sensitivity C-reactive protein and LDL provide valuable information in middle-aged hypertensive and HNBP patients related to arterial stiffness and early arterial aging, but only hsCRP is a sensitive predictor of EAA and PWV.

Retrospective Analysis of Cardiovascular Disease Risk Parameters in Participants of a Preventive Health and Wellness Program

Lifestyle, dietary, and nutritional choices are important influencing parameters of cardiovascular disease (CVD) risk, the number one cause of morbidity and mortality globally. Our aims were to i) characterize CVD risk parameters using data from 7939 participants enrolled in a preventive health and wellness program between March 2010 and January 2017; and ii) evaluate intervention effects in 3,020 participants who returned for follow-up. Blood measurements (nutrient markers), CVD risk parameters (abdominal obesity, hypertension, hyperglycemia, hypertriglyceridemia, low high-density lipoprotein (HDL), insulin resistance, and inflammation), glycemic status (HbA1c), and insulin resistance (HOMA-IR) were assessed. Framingham and Reynold's risk scores were also calculated. After approximately one year of treatment (n = 3 020), mean arachidonic acid:eicosapentaenoic acid (AA:EPA) ratio, homocysteine, and HbA_lc concentrations were significantly reduced; other risk parameters did not improve but mean values remained within reference ranges. Excluding participants taking related medications, 38.8%, 37.2%, 38.0%, 42.5%, and 59.7% of those with hyperglycemia, hypertriglyceridemia, low HDL, insulin resistance, or prediabetes, respectively, at baseline no longer had the condition at follow-up. In contrast, of individuals within the reference range at baseline, new cases at follow-up were found for 10.1%, 12.2%, 6.3%, 8.2%, and 7.6% (as above, respectively). Regression models revealed a significant association between serum 25-hydroxyvitamin D concentrations ≥100 nmol/L and reductions in many CVD risk parameters after adjustment for confounding variables. These findings suggest that a preventive approach to health and wellness focused on nutrients, optimal serum 25-hydroxyvitamin D concentrations, and lifestyle changes has the potential to reduce the risk of CVD.

Associations of 25-Hydroxyvitamin D With the Blood Pressure Response to Maximal Exercise Among Healthy Adults

Insufficient 25-hydroxyvitamin D [25(OH)D] levels are associated with high resting blood pressure (BP). However, the relationship between 25(OH)D and the peak systolic BP (SBP) response to exercise, a predictor of future hypertension, has yet to be investigated. We sought to examine the relationship among serum 25(OH)D and the peak SBP response to a graded exercise stress test (GEST) among a large sample (n = 417) of healthy men (49%) and women (51%) over a broad age range (20-76 years; mean age: 44.1 ± 0.8 years). We hypothesized that individuals with clinically insufficient 25(OH)D would have a greater peak SBP response to a GEST compared to individuals with sufficient 25(OH)D levels. Fasting serum 25(OH)D, anthropometrics, resting BP, and peak exercise SBP were obtained at the baseline visit of a larger clinical trial (STOMP; NCT01140308). Mean 25(OH)D levels were 36.1 ± 0.7 ng/ml, with ∼35% of individuals classified as insufficient (<30 ng/ml). Average resting BP was 119 ± 13 mmHg/75 ± 10 mmHg, with 52.3% considered to have normal BP, while 25.2% had elevated BP and 22.5% had established hypertension. The peak SBP response to a GEST was similar between individuals with sufficient (48 ± 19 mmHg) versus insufficient (48 ± 18 mmHg) 25(OH)D (p = 1.000). One unexpected finding emerged such that individuals with sufficient 25(OH)D had higher resting SBP (120 ± 14 mmHg vs. 117 ± 13 mmHg; p = .020) than individuals with insufficient 25(OH)D. In contrast to our hypothesis, 25(OH)D levels were not associated with the peak SBP response to a GEST. Baseline 25(OH)D levels were positively correlated with resting SBP; however, the magnitude of this effect is likely not clinically meaningful.

Improvements in peripheral vascular function with vitamin D treatment in deficient adolescents with type 1 diabetes

BACKGROUND

Vitamin D (VitD) deficiency is prevalent in adolescents with type 1 diabetes (T1D) and is associated with diabetes-related vascular complications in adulthood. The objective of this clinical trial was to assess VitD treatment on endothelial function (EF) and markers of renal inflammation, in this patient group.

METHODS

Adolescents with T1D with suboptimal levels of VitD (<37.5 nmol/L) were treated for 12 to 24 weeks with a VitD analog (VitD₃ ) at doses of 1000 or 2000 IU daily. The primary end-point assessed the change in reactive hyperemia index (lnRHI), a measure of EF. Secondary end-points included changes in blood pressure, lipid profile, HbA1c and albumin creatinine ratio (ACR). Urinary cytokine/chemokine inflammatory profile was also assessed in a subset of subjects posttreatment.

RESULTS

Two hundred and seventy-one subjects were screened for VitD status and 31 VitD deficient subjects with a mean age of 15.7 ± 1.4 years were enrolled and completed the study. Mean 25-OH-VitD levels significantly increased (33.0 ± 12.8 vs 67.0 ± 23.2 nmol/L, P < .01) with a significant improvement in EF following VitD supplementation (lnRHI 0.58 ± 0.20 vs 0.68 ± 0.21, P = .03). VitD supplementation did not significantly impact systolic blood pressure/diastolic blood pressure (SBP/DBP), lipids, HbA1c and ACR and no adverse effects were seen. Several urinary inflammatory cytokines/chemokines: MCP-3 (P < .01), epidermal growth factor (EGF) (P < .01) tumor necrosis factor β (TNFβ) (P = .01), interleukin-10 (IL-10) (P = .01), also significantly decreased post-VitD-treatment.

CONCLUSIONS

Treatment with VitD was associated with an improvement in EF and reduced expression of urinary inflammatory markers in adolescents with T1D. This data is suggestive of an additional benefit of VitD supplementation on early markers of microvascular complications.

Effect of Monthly, High-Dose, Long-Term Vitamin D Supplementation on Central Blood Pressure Parameters: A Randomized Controlled Trial Substudy

BACKGROUND

The effects of monthly, high-dose, long-term (≥1-year) vitamin D supplementation on central blood pressure (BP) parameters are unknown.

METHODS AND RESULTS

A total of 517 adults (58% male, aged 50-84 years) were recruited into a double-blinded, placebo-controlled trial substudy and randomized to receive, for 1.1 years (median; range: 0.9-1.5 years), either (1) vitamin D3 200 000 IU (initial dose) followed 1 month later by monthly 100 000-IU doses (n=256) or (2) placebo monthly (n=261). At baseline (n=517) and follow-up (n=380), suprasystolic oscillometry was undertaken, yielding aortic BP waveforms and hemodynamic parameters. Mean deseasonalized 25-hydroxyvitamin D increased from 66 nmol/L (SD: 24) at baseline to 122 nmol/L (SD: 42) at follow-up in the vitamin D group, with no change in the placebo group. Despite small, nonsignificant changes in hemodynamic parameters in the total sample (primary outcome), we observed consistently favorable changes among the 150 participants with vitamin D deficiency (<50 nmol/L) at baseline. In this subgroup, mean changes in the vitamin D group (n=71) versus placebo group (n=79) were -5.3 mm Hg (95% confidence interval [CI], -11.8 to 1.3) for brachial systolic BP (P=0.11), -2.8 mm Hg (95% CI, -6.2 to 0.7) for brachial diastolic BP (P=0.12), -7.5 mm Hg (95% CI, -14.4 to -0.6) for aortic systolic BP (P=0.03), -5.7 mm Hg (95% CI, -10.8 to -0.6) for augmentation index (P=0.03), -0.3 m/s (95% CI, -0.6 to -0.1) for pulse wave velocity (P=0.02), -8.6 mm Hg (95% CI, -15.4 to -1.9) for peak reservoir pressure (P=0.01), and -3.6 mm Hg (95% CI, -6.3 to -0.8) for backward pressure amplitude (P=0.01).

CONCLUSIONS

Monthly, high-dose, 1-year vitamin D supplementation lowered central BP parameters among adults with vitamin D deficiency but not in the total sample.

CLINICAL TRIAL REGISTRATION

URL: http://www.anzctr.org.au. Unique identifier: ACTRN12611000402943.

Effect of Vitamin D Supplementation on Vascular Functions and Oxidative Stress in Type 2 Diabetic Patients with Vitamin D Deficiency

BACKGROUND

Vitamin D levels are reported to have an inverse liaison with the risk of cardiovascular diseases. Hence, we aimed to evaluate the effect of Vitamin D supplementation on changes in vascular functions and oxidative stress in type 2 diabetic patients with Vitamin D deficiency.

SUBJECTS AND METHODS

One hundred and three patients with type 2 diabetes attending endocrinology outpatients department in a tertiary care hospital were screened for Vitamin D deficiency. Patients with serum 25-hydroxy Vitamin D levels <20 ng/ml were considered as deficient and were administered 60,000 IU of oral Vitamin D₃ weekly for 8 weeks. In these patients, parameters of vascular functions (carotid-femoral pulse wave velocity, brachial-ankle pulse wave velocity, and arterial stiffness index) and oxidative stress (serum malondialdehyde levels and total antioxidant status) were measured at baseline and after 8 weeks of oral Vitamin D supplementation.

RESULTS

Among 103 patients with type 2 diabetes, 75 (72.82%) were found to have Vitamin D deficiency. Amidst these patients, carotid-femoral pulse wave velocity (991.6 ± 161.82 vs. 899.29 ± 151.86, P < 0.001), right brachial-ankle pulse wave velocity (1446.16 ± 204.33 vs. 1350.8 ± 178.39, P < 0.001), and left brachial-ankle pulse wave velocity (1493.81 ± 219.65 vs. 1367.61 ± 220.64, P < 0.001) showed a significant reduction following Vitamin D supplementation. Further, these patients were found to have significant fall in serum malondialdehyde levels with rise in total antioxidant status ensuing Vitamin D supplementation.

CONCLUSION

The present study shows that oral Vitamin D supplementation of 60,000 IU/week for 8 weeks significantly improves vascular functions and reduces oxidative stress in type 2 diabetic patients with Vitamin D deficiency.

Crosstalk between Vitamins A, B12, D, K, C, and E Status and Arterial Stiffness

Arterial stiffness is associated with cardiovascular risk, morbidity, and mortality. The present paper reviews the main vitamins related to arterial stiffness and enabling destiffening, their mechanisms of action, providing a brief description of the latest studies in the area, and their implications for primary cardiovascular prevention, clinical practice, and therapy. Despite inconsistent evidence for destiffening induced by vitamin supplementation in several randomized clinical trials, positive results were obtained in specific populations. The main mechanisms are related to antiatherogenic effects, improvement of endothelial function (vitamins A, C, D, and E) and metabolic profile (vitamins A, B12, C, D, and K), inhibition of the renin-angiotensin-aldosterone system (vitamin D), anti-inflammatory (vitamins A, D, E, and K) and antioxidant effects (vitamins A, C, and E), decrease of homocysteine level (vitamin B12), and reversing calcification of arteries (vitamin K). Vitamins A, B12, C, D, E, and K status is important in evaluating cardiovascular risk, and vitamin supplementation may be an effective, individualized, and inexpensive destiffening therapy.

Effectiveness of Vitamin D Supplementation for Cardiovascular Health Outcomes

There is a plausible physiological theory, supported by many observational studies, that vitamin D supplementation should be effective for improving cardiovascular end points, such as blood pressure (BP), large artery stiffness, atherosclerosis, endothelial function and clinical events. However, results from randomised controlled trials (RCTs) have been inconsistent. In this review, we evaluated the evidence regarding the effectiveness of vitamin D supplementation for cardiovascular surrogate and hard clinical end points. RCTs were assessed in terms of sample size, duration of supplementation, baseline vitamin D level inclusion criteria (i.e., absence of vitamin D deficiency), dosage of vitamin D and population under investigation. Forty-five RCTs were identified. Eight RCTs with BP and 6 RCTs with large artery stiffness as the end points were found to comply with guidelines for the optimal design of clinical trials evaluating nutrient effects. Only 2 of the RCTs with an optimal design were effective in decreasing BP with vitamin D supplementation, although these were of moderate sample size (<150) and very short duration (8 weeks for both), whilst no RCT was effective in reducing large artery stiffness. Similar results were observed for atherosclerotic and endothelial function markers as end points. Only 1 RCT reported cardiovascular events as an end point and found neither increased nor decreased incident cardiovascular events over 7 years of follow-up. In conclusion, results from published RCTs indicate that vitamin D supplementation is ineffective in improving cardiovascular health among various patient populations, including in the presence or absence of vitamin D deficiency.