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.

Evaluation of oxidative/nitrative stress and uterine artery pulsatility index in early pregnancy

Introduction

Increased oxidative/nitrative stress is characteristic not only in pathologic, but also in healthy pregnancy. High uterine artery pulsatility index (UtAPI) at the end of the first trimester is associated with altered placentation and elevated risk for adverse pregnancy outcomes. We aimed to examine the relationship of systemic oxidative/nitrative stress and uterine artery pulsatility index in the first trimester and their correlation to pregnancy outcomes.

Material and methods

Healthy pregnant women were recruited at 12-13th gestational week ultrasound examination; UtAPI was determined by color Doppler ultrasound. Patients were divided into high (UtAPI ≥ 2.3) (n = 30) and low (n = 31) resistance groups, and pregnancies were followed until labor. Systemic oxidative/nitrative stress was estimated by measuring total peroxide level, total antioxidant capacity and nitrotyrosine level.

Results

Plasma total peroxide level was significantly lower (2,510 ± 39 µM vs. 2,285 ± 59 µM), total antioxidant capacity was higher (781 ± 16 mM CRE vs. 822 ± 13 mM CRE) in the high UtAPI group, which were accompanied by lower birth weight (3,317 ± 64 vs. 3,517 ± 77 g, P < 0.05). Plasma total peroxide level showed a negative correlation (by Pearson) to UtAPI (P < 0.01) and positive correlation to birth weight (P < 0.05).

Conclusions

According to our results, lower systemic oxidative stress showed correlation with high UtAPI measured between the 12-13th weeks of gestation. We also found significant differences in the birth weight of healthy newborns; therefore it is worth examining this relationship in pathological pregnancies.

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.

Nitrative stress and poly(ADP-ribose) polymerase activation in healthy and gestational diabetic pregnancies

AIMS/HYPOTHESIS

Increased oxidative-nitrosative stress, poly(ADP-ribose) polymerase (PARP) activation and subsequent cellular damage play important roles in the complications of both diabetes mellitus and pregnancy. Our aim was to investigate nitrative stress and PARP activity levels during normal and gestational diabetic (GDM) pregnancy in both maternal and fetal tissues.

METHODS

Blood samples were collected during pregnancy (weeks 16-29 and 36-40), and placental and umbilical cord tissues were harvested after delivery from healthy volunteers and GDM patients subjected to a carbohydrate-restricted diet or insulin treatment. Immunohistochemical staining was performed on leucocytes and tissue sections using anti-nitrotyrosine (NT), anti-poly(ADP-ribose) (PAR) and anti-apoptosis inducing factor antibodies.

RESULTS

In healthy pregnancies the intensity of NT and PAR staining of leucocytes correlated positively with gestational week (R (2) = 0.43, p < 0.01 and R (2) = 0.49, p < 0.001, respectively). In patients on a carbohydrate-restricted diet PAR staining was already strong in weeks 16-29 (p < 0.001 vs control) and did not increase further. In weeks 16-29 there was a correlation between PAR staining and the 2 h value of the oral glucose tolerance test (R (2) = 0.49, p < 0.001). Patients with the highest level of leucocyte PARP activity later required insulin therapy, which decreased the intensity of NT and PAR staining. Placental and umbilical cord tissues also had a higher level of nitrative stress markers in GDM pregnancies, but the highest level of PARP activity was observed after insulin therapy.

CONCLUSIONS/INTERPRETATION

Continuous elevation of tyrosine nitration and PARP activation may be considered physiological during pregnancy. However, the high level of PARP activity in early pregnancy may signal the subsequent development of severe GDM.

Rapid 'glycaemic swings' induce nitrosative stress, activate poly(ADP-ribose) polymerase and impair endothelial function in a rat model of diabetes mellitus

AIM/HYPOTHESIS

Postpandrial hyperglycaemia is a significant risk factor for the development of macrovascular diseases. There is no clear agreement in the field whether these alterations result from hyperglycaemic episodes or from exaggerated alterations ('glycaemic swings') in blood glucose. We compared the effect of stable high glucose with a model of poorly maintained insulin-controlled diabetes (on average lower glucose, but with large glycaemic swings) on the development of endothelial dysfunction in rats.

METHODS

Intermediate- or long-acting insulin was used to reduce mean blood glucose levels. One group of animals had stable low glucose levels, while animals in the other group exhibited rapid changes ('swings') in their blood glucose concentration. Acetylcholine-induced endothelium-dependent vascular relaxation of the thoracic aorta was measured. Immunohistochemistry, western blot analysis and flow cytometry were used to determine nitrotyrosine formation and poly(ADP-ribose) accumulation in the aorta, in circulating leucocytes and in bone marrow cells.

RESULTS

Steady normalisation of blood glucose levels (a model of well-controlled diabetes) protected against the development of endothelial dysfunction, poly(ADP-ribose) polymerase (PARP) activation and nitrotyrosine production. However, impairment of endothelium-dependent relaxation was found in the animals undergoing glycaemic swings, even though the fructosamine levels in these animals were lower than in the untreated diabetic rats. This was associated with elevated PARP activation in the aorta and in bone marrow cells that was similar to or even more pronounced than that seen in the untreated diabetic animals.

CONCLUSIONS/INTERPRETATION

Large glycaemic swings exert deleterious cardiovascular effects in diabetes mellitus, in part via enhanced activation of the PARP pathway.

Targeted inactivation of the plastid ndhB gene in tobacco results in an enhanced sensitivity of photosynthesis to moderate stomatal closure

The ndh genes encoding for the subunits of NAD(P)H dehydrogenase complex represent the largest family of plastid genes without a clearly defined function. Tobacco (Nicotiana tabacum) plastid transformants were produced in which the ndhB gene was inactivated by replacing it with a mutant version possessing translational stops in the coding region. Western-blot analysis indicated that no functional NAD(P)H dehydrogenase complex can be assembled in the plastid transformants. Chlorophyll fluorescence measurements showed that dark reduction of the plastoquinone pool by stromal reductants was impaired in ndhB-inactivated plants. Both the phenotype and photosynthetic performance of the plastid transformants was completely normal under favorable conditions. However, an enhanced growth retardation of ndhB-inactivated plants was revealed under humidity stress conditions causing a moderate decline in photosynthesis via stomatal closure. This distinctive phenotype was mimicked under normal humidity by spraying plants with abscisic acid. Measurements of CO(2) fixation demonstrated an enhanced decline in photosynthesis in the mutant plants under humidity stress, which could be restored to wild-type levels by elevating the external CO(2) concentration. These results suggest that the plastid NAD(P)H:plastoquinone oxidoreductase in tobacco performs a significant physiological role by facilitating photosynthesis at moderate CO(2) limitation.

Homeologous plastid DNA transformation in tobacco is mediated by multiple recombination events

Efficient plastid transformation has been achieved in Nicotiana tabacum using cloned plastid DNA of Solanum nigrum carrying mutations conferring spectinomycin and streptomycin resistance. The use of the incompletely homologous (homeologous) Solanum plastid DNA as donor resulted in a Nicotiana plastid transformation frequency comparable with that of other experiments where completely homologous plastid DNA was introduced. Physical mapping and nucleotide sequence analysis of the targeted plastid DNA region in the transformants demonstrated efficient site-specific integration of the 7.8-kb Solanum plastid DNA and the exclusion of the vector DNA. The integration of the cloned Solanum plastid DNA into the Nicotiana plastid genome involved multiple recombination events as revealed by the presence of discontinuous tracts of Solanum-specific sequences that were interspersed between Nicotiana-specific markers. Marked position effects resulted in very frequent cointegration of the nonselected peripheral donor markers located adjacent to the vector DNA. Data presented here on the efficiency and features of homeologous plastid DNA recombination are consistent with the existence of an active RecA-mediated, but a diminished mismatch, recombination/repair system in higher-plant plastids.

[Antioxidant effect of vitamin E in experimental hyperlipidemia]

The effect of Vitamin E treatment was studied in experimental hyperlipidaemia. The male Wistar rats got control diet and parallel fat rich diet contained 2% cholesterol, 0.5% cholic acid and 20% sunflower oil added into LATI food during 9 days. The treated hyperlipidemic animals got vitamin E for 9 days in daily 8.56 mg/b.w.kg dose mixed in food. The effect of antioxidant treatment on changes of lipid peroxidation, content of diene conjugates, thiobarbituric acid reactive products and natural scavenger capacity of rat liver homogenates and microsome fractions were measured by spectrophotometric and luminometric methods. Fatty acid composition of lipid fraction of samples was determined by capillary gas chromatography. Vitamin E in hyperlipidemia increased the natural scavenger capacity of liver and decreased the level of thiobarbituric acid reactive products and dien conjugates. There was no change in fatty acid composition of samples on effect of vitamin E antioxidant treatment.