Arteriolar insulin resistance 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.

Estradiol Valerate Affects Hematological and Hemorheological Parameters in Rats

Polycystic ovary syndrome (PCOS) is one of the most common endocrinological diseases in women. Although the risk of cardiovascular diseases is high in PCOS, the number of scientific publications describing hemorheological changes is not significant. We aimed to perform a comprehensive hematological and micro-rheological study on experimentally induced PCOS in rats.Wistar rats were divided into control (n = 9) and PCOS groups (n = 9), in which animals received single-dose estradiol valerate. Measurements were carried out before treatment and monthly for four months. Bodyweight, blood glucose concentration, hematological parameters, red blood cell (RBC) deformability, and aggregation were measured. A histological examination of the ovary was performed at the end of the experiment. The blood glucose level and the bodyweight were significantly elevated vs. base in the PCOS group. A significant decrease was seen in RBC count, hemoglobin, and hematocrit. The maximal elongation index showed a significant increase. PCOS also resulted in a significant increase in RBC aggregation index parameters. The histological and hormone examinations confirmed developed PCOS. The administration of estradiol valerate caused significant changes during the examined period in hematological and hemorheological parameters. Our results draw attention to the possible usefulness of micro-rheological investigations in further studies on PCOS.

Influence of Vitamin D on the Vasoactive Effect of Estradiol in a Rat Model of Polycystic Ovary Syndrome

We examined the vasoactive effect of estradiol in a rat model of early PCOS and the influence of vitamin D deficiency (VDD). We created a model of chronic hyperandrogenism and VDD in adolescent female Wistar rats (N = 46) with four experimental groups: vitamin D supplemented (T-D+), VDD (T-D-), hyperandrogenic and vitamin D supplemented (T+D+), and hyperandrogenic and VDD (T+D-). T+ groups received an 8-week-long transdermal Androgel treatment, D-animals were on vitamin D-reduced diet and D+ rats were supplemented orally with vitamin D3. Estrogen-induced vasorelaxation of thoracic aorta segments were measured with a wire myograph system with or without the inhibition of endothelial nitric oxide synthase (eNOS) or cyclooxygenase-2 (COX-2). The distribution of estrogen receptor (ER), eNOS and COX-2 in the aortic wall was assessed by immunohistochemistry. VDD aortas showed significantly lower estradiol-induced relaxation independently of androgenic status that was further decreased by COX-2 inhibition. COX-2 inhibition failed to alter vessel function in D+ rats. Inhibition of eNOS abolished the estradiol-induced relaxation in all groups. Changes in vascular function in VDD were accompanied by significantly decreased ER and eNOS staining. Short-term chronic hyperandrogenism failed to, but VDD induced vascular dysfunction, compromised estrogen-dependent vasodilatation and changes in ER and eNOS immunostaining.

Histomorphometric and immunohistochemical changes in interstitial cells and ovarian follicles of rats with polycystic ovaries treated with clomiphene citrate

OBJECTIVE

To evaluate the histomorphometric and immunohistochemical changes in interstitial cells and ovarian follicles of rats treated with clomiphene citrate during and after induction of permanent estrus.

METHODS

Twenty four adult-female rats with regular estrous cycle were equally divided into three groups: (1) GCtrl-at estrous phase. (2) GPCOS-at permanent-estrous phase. (3) GCC-PCOS rats, which remained exposed to 60 days of continuous illumination and treated with Clomiphene Citrate. After that, the animals were euthanized, and the ovaries were removed and processed for paraffin embedding. Sections were stained with H.E. for histomorphometry or subjected to immunohistochemistry for Ki-67 and cleaved caspase-3 detections.

RESULTS

The GPCOS showed lack of corpus luteum and several ovarian cysts, as well as interstitial-like cells. The presence of corpus luteum and a significant increase in primary and antral follicles were observed in GCC, which also showed a decrease in the number of ovarian cysts and in the area occupied by interstitial-like cells, as well as a decrease in nuclear volume of interstitial cells. The percentage of cell proliferation was significantly higher in granulosa cells of the GCC. On the other hand, the percentage of apoptosis was significantly higher in the granulosa cells of GPCOS than the GCC.

CONCLUSION

The ovaries of rats treated with clomiphene citrate showed a decrease in the number of cysts, an increase in the number of ovarian follicles, the presence of corpus luteum along with a decrease in the nuclear volume in the area occupied by interstitial cells.

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.

Melatonin may prevent or reverse polycystic ovary syndrome in rats

OBJECTIVE

To evaluate the ovarian effects of melatonin (Mel) in a rat model of polycystic-ovary-syndrome (PCOS) before and after permanent estrus induction.

METHODS

Thirty-two adult-female rats with regular estrous cycle were equally divided into four groups: 1) GCtrl - at estrous phase. 2) GPCOS - at permanent-estrous phase. 3) GMel1 - treated for 60 days with Mel (0.4 mg/Kg) during permanent estrus induction and 4) GMel2 - rats with PCOS and treated for 60 days with Mel. After that, the animals were euthanized, and the ovaries were removed and processed for paraffin embedding. Sections were stained with H.E. for histomorphometry or subjected to immunohistochemistry for Ki-67 and cleaved caspase-3 (Casp-3) detections.

RESULTS

The GPCOS showed lack of corpus luteum and several ovarian cysts, as well as interstitial-like cells. The presence of corpus luteum and a significant increase in primary and antral follicles were observed in Mel-treated groups, which also showed a decrease in the number of ovarian cysts and in the area occupied by interstitial-like cells. These results were more evident in GMel1. The percentage of Ki-67-positive cells was significantly higher in the Mel-treated groups, mainly in the GMel2, as compared to GPCOS. On the other hand, the percentage of Casp-3-positive cells was significantly lower in granulosa cells of GMel1, whereas it was significantly higher in the interstitial-like cells of GMel2, in comparison to GPCOS.

CONCLUSION

Melatonin administration prevents the permanent estrus state in the PCOS rat model. This effect is more efficient when melatonin is administered before permanent estrus induction.

Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.

Liraglutide improves hypertension and metabolic perturbation in a rat model of polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, with a prevalence of 5–8%. Type 2 diabetes and cardiovascular disease (CVD) are its long-term complications. Targeted therapies addressing both these complications together are lacking. Glucagon like peptide-1 (GLP-1) agonists that are used to treat type 2 diabetes mellitus have beneficial effects on the cardiovascular system. Hence we hypothesized that a GLP-1 agonist would improve both cardiovascular and metabolic outcomes in PCOS. To test this hypothesis, we used an established rat model of PCOS. Prepubertal female Sprague Dawley rats were sham-implanted or implanted s.c. with dihydrotestosterone (DHT) pellets (90 day release; 83μg/day). At 12 wks of age, sham implanted rats received saline injections and the DHT treated animals were administered either saline or liraglutide (0.2mg/kg s.c twice daily) for 4 weeks. Subgroups of rats were implanted with telemeters between 12-13 weeks of age to monitor blood pressure. DHT implanted rats had irregular estrus cycles and were significantly heavier than the control females at 12 weeks (mean± SEM 251.9±3.4 vs 216.8±3.4 respectively; p<0.05) and 4 weeks of treatment with liraglutide in DHT treated rats significantly decreased body weight (mean± SEM 294.75 ±3.2 in DHT+ saline vs 276.25±2.7 in DHT+ liraglutide group respectively; p<0.01). Liraglutide treatment in the DHT implanted rats significantly improved glucose excursion during oral glucose tolerance test (area under the curve: DHT+ saline 28674±310 vs 24990± 420 in DHT +liraglutide p <0.01). DHT rats were hypertensive and liraglutide treatment significantly improved mean arterial pressure. These results suggest that GLP-1 treatment could improve DHT–induced metabolic and blood pressure deficits associated with PCOS.

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.

Immunohistochemical evaluation of proliferation, apoptosis and steroidogenic enzymes in the ovary of rats with polycystic ovary

Objective: to evaluate the immunohistochemical expression of proliferative, apoptotic and steroidogenic enzyme markers in the ovaries of rats with polycystic ovary syndrome (PCOS). Methods: twenty rats were divided into two groups: GCtrl - estrous phase, and PCOS - with polycystic ovaries. The GCtrl animals were subjected to a lighting period from 7 am to 7 pm, while the animals with PCOS group remained with continuous lighting for 60 days. Subsequently, the animals were anesthetized, the ovaries were removed and fixed in 10% formaldehyde, prior to paraffin embedding. Sections were stained using H.E. or subjected to immunohistochemical methods for the detection of Ki-67, cleaved caspase-3, CYP11A1, CYP17A1 and CYP19A1. The results were analyzed using Student's t-test (p < 0,05). Results: morphological results showed evidence of interstitial cells originating from the inner theca cells of degenerating ovarian cysts in PCOS. Immunoexpression of Ki-67 was higher in the granulosa cells in GCtrl, and the theca interna cells in PCOS, while cleaved caspase-3 was higher in granulosa cells of ovarian cysts from PCOS and in the theca interna cells of GCtrl. Immunoreactivity of CYP11A1 in the theca interna, granulosa and interstitial cells was similar between the two groups, while CYP17A1 and CYP19A1 were higher in the granulosa and interstitial cells in the PCOS group. Conclusion: the results indicate that the interstitial cells are derived from the theca interna and that enzymatic changes occur in the theca interna and interstitial cells in ovaries of rats with PCOS, responsible for the high levels of androgens and estradiol.

Effects of vitamin D3 derivative--calcitriol on pharmacological reactivity of aortic rings in a rodent PCOS model

BACKGROUND

The aim of this study was to examine the effects of the hyperandrogenic state in dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS), the vascular responses to different vasoactive agents, and the modulatory role of vitamin D3.

METHODS

APCOS model was induced by DHT application in 20 female Wistar rats. Ten of the DHT treated rats simultaneously received calcitriol treatment. After 10 weeks, myographs were used to test the reactivity of isolated thoracic aortic rings to norepinephrine and acetylcholine. Thereafter, the vascular rings were incubated with the NO-synthase blocker (nitro-L-arginine methyl ester) or the cyclooxygenase inhibitor (indomethacin) for 20 min, and the effects of norepinephrine and acetylcholine were re-evaluated.

RESULTS

Norepinephrine-induced vasoconstriction was enhanced after DHT treatment, but this effect was attenuated by calcitriol administration. Vasorelaxation of DHT-treated thoracic aortic rings was impaired, but this could be partly reversed by calcitriol application. Impaired NO-dependent vasorelaxation in DHT-treated animals was mostly reversed by concomitant calcitriol administration, but this effect was diminished by prostanoid-dependent vasoconstriction.

CONCLUSIONS

These studies show that the enhanced sensitivity to vasoconstrictors and impaired NO-dependent vasorelaxation in hyperandrogenic PCOS rats could be partially reversed by calcitriol treatment.

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

AIMS

In polycystic ovary syndrome (PCOS), metabolic and cardiovascular dysfunction is related to hyperandrogenic status and insulin resistance, however, Vitamin D3 has a beneficial effect partly due to its anti-oxidant capacity. Nitrative stress is a major factor in the development of cardiovascular dysfunction and insulin resistance in various diseases. Our aim was to determine the effects of vitamin D3 in a rat model of PCOS, particularly the pathogenic role of nitrative stress.

MAIN METHODS

Female Wistar rats weighing 100-140g were administered vehicle (C), dihydrotestosterone (DHT) or dihydrotestosterone plus vitamin D3 (DHT+D) (n=10 per group). On the 10th week, acetylcholine (Ach) induced relaxation ability of the isolated thoracic aorta rings was determined. In order to examine the possible role of endothelial nitric oxide synthase (eNOS) and cyclooxygenase-2 (COX-2) pathways in the impaired endothelial function, immunohistochemical labeling of aortas with anti-eNOS and anti-COX-2 antibodies was performed. Leukocyte smears, aorta and ovary tissue sections were also immunostained with anti-nitrotyrosine antibody to determine nitrative stress.

KEY FINDINGS

Relaxation ability of aorta was reduced in group DHT, and vitamin D3 partly restored Ach induced relaxation. eNOS labeling was significantly lower in DHT rats compared to the other two groups, however COX-2 staining showed an increment. Nitrative stress showed a significant increase in response to dihydrotestosterone, while vitamin D3 treatment, in case of the ovaries, was able to reverse this effect.

SIGNIFICANCE

Nitrative stress may play a role in the pathogenesis of PCOS and in the development of the therapeutic effect of vitamin D3.

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.

Altered insulin-induced relaxation of aortic rings in a dihydrotestosterone-induced rodent model of polycystic ovary syndrome

OBJECTIVE

To clarify the effects of dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS) on the insulin-dependent vasodilatation of the thoracic aorta and the role of vitamin D in a rat model.

DESIGN

Controlled experimental animal study.

SETTING

Laboratory.

ANIMAL(S)

Thirty adolescent female Wistar rats.

INTERVENTION(S)

The PCOS model was induced by 10 weeks of DHT treatment (83 μg/d). One-half of the DHT-treated animals also received vitamin D (120 ng/kg/wk).

MAIN OUTCOME MEASURE(S)

The aortic rings of the control, DHT, and DHT plus vitamin D-treated animals were isolated. The insulin-dependent vasodilation of the isolated aortic rings was compared in Krebs-Ringer solution and under blockade of nitric oxide (NO) synthase or cyclooxygenase.

RESULT(S)

The insulin-dependent vasorelaxation decreased in both DHT-treated groups independently from the vitamin D treatment; NO-dependent and -independent relaxations were both impaired. In response to prostanoid, vasoconstriction was increased after DHT treatment. The NO-independent relaxation was partially improved by vitamin D treatment, which was neutralized by increased prostanoid-dependent vasoconstriction.

CONCLUSION(S)

Previously, we found that vitamin D treatment prevented systemic insulin resistance; however, in this study, we did not detect any influence on the vascular insulin resistance of the aorta that was induced by DHT treatment. Consequently, controlling insulin resistance with vitamin D alone did not resolve the aortic endothelial dysfunction caused by the hyperandrogenic state.