Endothelial relaxation mechanisms and nitrative stress are partly restored by Vitamin D3 therapy in a rat model of polycystic ovary syndrome

Effects of Gender and Vitamin D on Vascular Reactivity of the Carotid Artery on a Testosterone-Induced PCOS Model

The negative cardiovascular effects of polycystic ovary syndrome (PCOS) and vitamin D deficiency (VDD) have been discussed previously; however, the sex differences between PCOS females and males are not yet known. Our aim was to investigate the effect of PCOS and VDD in the carotid artery of male and female Wistar rats. Females were treated with transdermal testosterone (Androgel) for 8 weeks, which caused PCOS. VDD and vitamin D supplementation were accomplished via diet. The carotid arteries' contraction and relaxation were examined using myography. Receptor density was investigated using immunohistochemistry. In PCOS females, angiotensin receptor density, angiotensin II-induced contraction, androgen receptor optical density, and testosterone-induced relaxation increased. The increased contractile response may increase cardiovascular vulnerability in women with PCOS. As an effect of VDD, estrogen receptor density increased in all our groups, which probably compensated for the reduced relaxation caused by VDD. Testosterone-induced relaxation was decreased as a result of VDD in males and non-PCOS females, whereas this reduction was absent in PCOS females. Male sex is associated with increased contraction ability compared with non-PCOS and PCOS females. VDD and Androgel treatment show significant gender differences in their effects on carotid artery reactivity. Both VDD and PCOS result in a dysfunctional vascular response, which can contribute to cardiovascular diseases.

Role of Vitamin D Deficiency in the Pathogenesis of Cardiovascular and Cerebrovascular Diseases

Deficiency in vitamin D (VitD), a lipid-soluble vitamin and steroid hormone, affects approximately 24% to 40% of the population of the Western world. In addition to its well-documented effects on the musculoskeletal system, VitD also contributes importantly to the promotion and preservation of cardiovascular health via modulating the immune and inflammatory functions and regulating cell proliferation and migration, endothelial function, renin expression, and extracellular matrix homeostasis. This brief overview focuses on the cardiovascular and cerebrovascular effects of VitD and the cellular, molecular, and functional changes that occur in the circulatory system in VitD deficiency (VDD). It explores the links among VDD and adverse vascular remodeling, endothelial dysfunction, vascular inflammation, and increased risk for cardiovascular and cerebrovascular diseases. Improved understanding of the complex role of VDD in the pathogenesis of atherosclerotic cardiovascular diseases, stroke, and vascular cognitive impairment is crucial for all cardiologists, dietitians, and geriatricians, as VDD presents an easy target for intervention.

Effect of Vitamin D Status on Vascular Function of the Aorta in a Rat Model of PCOS

Polycystic ovary syndrome (PCOS) is associated with elevated cardiovascular risk. Early vascular dysfunction may lead to the development of cardiovascular disease in PCOS. Vitamin D deficiency (VDD) is a common comorbidity of PCOS that contributes to the pathogenesis of the disease and its complications. Both PCOS and VDD are accompanied by increased oxidative stress that may be involved in the arising vascular dysfunction. We aimed to investigate the role of vitamin D status on aortic function. PCOS was induced by an 8-week-long transdermal testosterone treatment of female rats, and low and adequate vitamin D status was achieved by dietary means. Contraction and relaxation abilities of isolated aortic segments were measured by myograph. Resorcin-fuchsin staining and immunohistochemical labeling of 3-nitrotyrosine were performed. No difference was shown in the norepinephrine-induced contraction of the aortas of different groups, whereas we detected reduced acetylcholine- and insulin-evoked relaxation in VDD groups. A lower level of resorcin-fuchsin staining and elevated 3-nitrotyrosine immunostaining was observed in VDD. In our study, we demonstrated early endothelial dysfunction in VDD PCOS rat model. Vitamin D supplementation could prevent vascular disturbances, while VDD itself damaged endothelium-dependent vasorelaxation and induced nitrative stress.

Effects of Vitamin D Deficiency on Proliferation and Autophagy of Ovarian and Liver Tissues in a Rat Model of Polycystic Ovary Syndrome

Aim: We aimed to examine the alterations of the insulin signaling pathway, autophagy, nitrative stress and the effect of vitamin D supplementation in the liver and ovaries of vitamin D deficient hyperandrogenic rats. Methods: Female Wistar rats received eight weeks of transdermal testosterone treatment and lived on a low vitamin D diet (D–T+). Vitamin D supplementation was achieved by oral administration of vitamin D3 (D+T+). Sham-treated (D+T–) and vitamin D deficient animals (D–T–) served as controls. (N = 10–12 per group). Results: D–T+ animals showed decreased LC3 II levels in the liver and increased p-Akt/Akt and p-eNOS/eNOS ratios with decreased insulin receptor staining in the ovaries. Vitamin D supplementation prevented the increase of Akt phosphorylation in the ovaries. Vitamin D deficiency itself also led to decreased LC3 II levels in the liver and decreased insulin receptor staining in the ovaries. D–T+ group showed no increase in nitrotyrosine staining; however, the ovaries of D–T– rats and the liver of D+T+ animals showed increased staining intensity. Conclusion: Vitamin D deficiency itself might lead to disrupted ovarian maturation and autophagy malfunction in the liver. Preventing Akt phosphorylation may contribute to the beneficial effect of vitamin D treatment on ovarian function in hyperandrogenism.

Vitamin D deficiency and androgen excess result eutrophic remodeling and reduced myogenic adaptation in small cerebral arterioles in female rats

Vitamin D (vitD) insufficiency affects 1 billion people worldwide. Androgen excess (AE) occurs in 8% of fertile females. There are few data about the combined effect of vitD deficiency and AE on the early biomechanical changes of cerebral arterioles in fertile-aged female. Forty-six adolescent female Wistar rats (21-28 day-old, weighing 90-110 g) were grouped randomly in four groups: vitD supplemented groups with and without transdermal testosterone (T) treatment, as well as vitD deficient groups also with and without transdermal T (n = 11 or 12, in all cases). After 8 weeks of treatment, anterior cerebral arterioles (in vivo diameter of 90-130 µm) were obtained and cylindrical segments were examined by pressure arteriography. Myogenic tone, tangential stress and incremental elastic moduli were computed and statistically analyzed. Elastic density was studied on resorcin-fuchsin-stained histological section. VitD deficiency with T treatment resulted in significantly lower inner radii and higher wall thickness values with reduced tangential stress and increased elastic fiber density. VitD deficiency reduced myogenic tone at higher intraluminar pressures (>110 mmHg). Our conclusion is that plasma vitD level is an important factor in the control of myogenic tone in cerebral resistance arteries. AE and vitD deficiency acting parallel induce remodeling of their wall.

How to choose the suitable animal model of polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS) is a gynecological metabolic and endocrine disorder with uncertain etiology. To understand the etiology of PCOS or the evaluation of various therapeutic agents, different animal models have been introduced. Considering this fact that is difficult to develop an animal model that mimics all aspects of this syndrome, but, similarity of biological, anatomical, and/or biochemical features of animal model to the human PCOS phenotypes can increase its application. This review paper evaluates the recently researched animal models and introduced the best models for different research purposes in PCOS studies. During January 2013 to January 2017, 162 studies were identified which applied various kinds of animal models of PCOS including rodent, primate, ruminant and fish. Between these models, prenatal and pre-pubertal androgen rat models and then prenatal androgen mouse model have been studied in detail than others. The comparison of main features of these models with women PCOS demonstrates higher similarity of these three models to human conditions. Thereafter, letrozole models can be recommended for the investigation of various aspects of PCOS. Interestingly, similarity of PCOS features of post-pubertal insulin and human chorionic gonadotropin rat models with women PCOS were considerable which can make it as a good choice for future investigations.

Vitamin D deficiency causes inward hypertrophic remodeling and alters vascular reactivity of rat cerebral arterioles

Background and purpose

Vitamin D deficiency (VDD) is a global health problem, which can lead to several pathophysiological consequences including cardiovascular diseases. Its impact on the cerebrovascular system is not well understood. The goal of the present work was to examine the effects of VDD on the morphological, biomechanical and functional properties of cerebral arterioles.

Methods

Four-week-old male Wistar rats (n = 11 per group) were either fed with vitamin D deficient diet or received conventional rat chow with per os vitamin D supplementation. Cardiovascular parameters and hormone levels (testosterone, androstenedione, progesterone and 25-hydroxyvitamin D) were measured during the study. After 8 weeks of treatment anterior cerebral artery segments were prepared and their morphological, biomechanical and functional properties were examined using pressure microangiometry. Resorcin-fuchsin and smooth muscle actin staining were used to detect elastic fiber density and smooth muscle cell counts in the vessel wall, respectively. Sections were immunostained for eNOS and COX-2 as well.

Results

VDD markedly increased the wall thickness, the wall-to-lumen ratio and the wall cross-sectional area of arterioles as well as the number of smooth muscle cells in the tunica media. As a consequence, tangential wall stress was significantly lower in the VDD group. In addition, VDD increased the myogenic as well as the uridine 5’-triphosphate-induced tone and impaired bradykinin-induced relaxation. Decreased eNOS and increased COX-2 expression were also observed in the endothelium of VDD animals.

Conclusions

VDD causes inward hypertrophic remodeling due to vascular smooth muscle cell proliferation and enhances the vessel tone probably because of increased vasoconstrictor prostanoid levels in young adult rats. In addition, the decreased eNOS expression results in endothelial dysfunction. These morphological and functional alterations can potentially compromise the cerebral circulation and lead to cerebrovascular disorders in VDD.

Inhibition of endoplasmic reticulum stress and oxidative stress by vitamin D in endothelial cells

Endoplasmic reticulum (ER) stress and oxidative stress promote endothelial dysfunction and atherosclerosis. Since vitamin D has been shown in several studies to lower the risk of cardiovascular disease, we examined the effects of vitamin D on ER stress and oxidative stress in endothelial cells. ER stress was measured using the placental secreted alkaline phosphatase assay and oxidative stress was measured by hydroethidine fluorescence. Expression of ER stress markers, including glucose-regulated protein 78, c-jun N-terminal kinase 1 phosphorylation, and eukaryotic initiation factor 2α phosphorylation, as well as X-box binding protein-1 splicing were measured in tunicamycin (TM)-treated human umbilical endothelial cells (HUVEC) treated with 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃) and other vitamin D analogs. When TM and 1,25-(OH)₂D₃ were added simultaneously, 1,25-(OH)₂D₃ prevented ER stress. However, the effect was much stronger when cells were pre-treated with 1,25-(OH)₂D₃ for 24-h. However, ER stress was not inhibited by 25-OH vitamin D₃ (25-OHD₃) or the vitamin D analog EB1089. Both ZK191784 and the vitamin D metabolite 24,25-dihydroxyvitamin D₃ were as effective as 1,25-(OH)₂D₃ in preventing ER stress. Similar effects were observed dextrose-induced stress. All of the compounds tested, except for 25-OHD₃, inhibited dextrose-induced (27.5mM) oxidative stress and ER stress. Although TM with and without 1,25-(OH)₂D₃ had no effect on VDR expression, inhibition of VDR expression via siRNA prevented 1,25-(OH)₂D₃, ZK191784, EB1089, and 24,25-dihydroxyvitamin D₃ from inhibiting dextrose-mediated SO generation. Furthermore, each vitamin D analog, with the exception of 25-OHD₃, prevented dextrose-induced toxicity. These results suggest that vitamin D has a protective effect on vascular endothelial cells.

Lower-limb veins are thicker and vascular reactivity is decreased in a rat PCOS model: concomitant vitamin D3 treatment partially prevents these changes

Polycystic ovary syndrome (PCOS) causes vascular damage to arteries; however, there are no data for its effect on veins. Our aim was to clarify the effects of dihydrotestosterone (DHT)-induced PCOS both on venous biomechanics and on pharmacological reactivity in a rat model and to test the possible modulatory role of vitamin D3 (vitD). PCOS was induced in female Wistar rats by DHT treatment (83 μg/day, subcutaneous pellet). After 10 wk, the venous biomechanics, norepinephrine (NE)-induced contractility, and acetylcholine-induced relaxation were tested in saphenous veins from control animals and from animals treated with DHT or DHT with vitD using pressure angiography. Additionally, the expression levels of endothelial nitric oxide synthase (eNOS) and cyclooxygenase (COX-2) were measured using immunohistochemistry. Increased diameter, wall thickness, and distensibility as well as decreased vasoconstriction were detected after the DHT treatment. Concomitant vitD treatment lowered the mechanical load on the veins, reduced distensibility, and resulted in vessels that were more relaxed. Although there was no difference in the endothelial dilation tested using acetylcholine (ACh), the blocking effect of N(G)-nitro-l-arginine methyl ester (l-NAME) was lower and was accompanied by lower COX-2 expression in the endothelium after the DHT treatment. Supplementation with vitD prevented these alterations. eNOS expression did not differ among the three groups. We conclude that the hyperandrogenic state resulted in thicker vein walls. These veins showed early remodeling and altered vasorelaxant mechanisms similar to those of varicose veins. Alterations caused by the chronic DHT treatment were prevented partially by concomitant vitD administration.