Vitamin D and Parathyroid Hormone Relationships with Urinary Nitric Oxide Metabolites and Plasma Isoprostanes in African-Americans

Abstract

Background: Vitamin D deficiency and secondary rises in parathyroid hormone (PTH) are highly prevalent in obese African-Americans. Endothelial dysfunction related to oxidative stress is more common in African-Americans compared to whites. Currently, the association of vitamin D (25-hydroxyvitamin D, 25-OH D) and PTH to nitric oxide metabolites (NOx) – nitrate and nitrite – and oxidative stress in African-Americans is unknown. Objective: A cross-sectional design was utilized to determine the association of 25-OH D and PTH with urinary NOx (UNOx) (n = 101) and plasma isoprostanes (n = 125), an oxidative stress marker, in overweight (body mass index of 25–39.9), normotensive African-Americans aged ≥35 years. Measurements: Multivariable linear regression analysis adjusted for age, sex, body mass index, and season was used to determine the relationship of 25-OH D and PTH to UNOx and isoprostanes. General linear models, adjusted for the same covariates, contrasted UNOx across three mutually exclusive vitamin D/PTH groups: (1) normal 25-OH D (51–249 nmol/l) and normal PTH (≤65 pg/ml); (2) low 25-OH D and normal PTH, and (3) low 25-OH D and high PTH. Results: 25-OH D was directly associated with UNOx before (p = 0.02) and after (p = 0.03) adjustment for PTH levels. A borderline significant association was observed between PTH and isoprostanes (p = 0.08). UNOx was 424, 290, and 270 µmol/8 h, respectively, across vitamin D/PTH groups 1–3 (p = 0.08). Conclusion: 25-OH D was directly associated with NO availability and PTH was positively, though borderline, associated with isoprostanes in overweight, normotensive adult African-Americans.

Heart valve disease: The role of calcidiol deficiency, elevated parathyroid hormone levels and oxidative stress in mitral and aortic valve insufficiency

“…In addition, calcitriol modulates endothelial and nitric oxide functions in the heart valves. 35 Oxidative stress is also associated with CVD. In this study, serum TOS and OSI, which reflect the redox balance between oxidation and antioxidation, demonstrated differences between HVD patients and control participants.…”

Relationship of vitamin D with cardiovascular disease risk factors in adults and adolescents and possible impact on its metabolism from the use of lipid-lowering medication

“…VitD may also exert protective effects on endothelial cell's dysfunction, which are inflammatory processes that precede atherosclerosis, through stimulation of nitric oxide (NO) production and may counteract superoxide anion generation, possibly by controlling at the level of phospho-active extracellular signal-regulated kinases [116]. VitD and PTH potentially influence NO bioavailability as depicted in Figure 12 [117]. In the setting of VitD deficiency, increased PTH activates 1,25(OH)2VitD production in the kidneys, increasing intracellular calcium which, in turn, promotes ROS production [118].…”

“…were obtained in a study in type 2 diabetic patients with hypovitaminosis D [134]. Another cross-sectional study though did not support an association of 25(OH)VitD levels with plasma isoprostanes in African-Americans probably due to the relatively modest sample size [117]. Of note, data from interventional studies are lacking.…”