Role of 17-beta-estradiol and progesterone on glucose homeostasis: effects of food restriction (50%) in pregnant and non pregnant rats

Characterization of Membrane-Associated Progesterone Receptor Component-2 (MAPRC2) from Trichinella spiralis and Its Interaction with Progesterone and Mifepristone

Trichinellosis is a foodborne zoonotic disease caused by Trichinella spp., including Trichinella spiralis. In the present study, T. spiralis membrane-associated progesterone receptor component-2 (Ts-MAPRC2) gene was cloned and characterized using protein sequencing analysis. Furthermore, the expression, purification, immunoblot assay, binding ability with progesterone antibody, and immunofluorescence assay were performed. A direct effect of progesterone (P4) and mifepristone (RU486) on the Ts-MAPRC2 gene was determined using in vitro cell culture that showed different expression levels at all developmental stages (muscle larvae (ML), female adult worm (F-AL), male adult worm (M-AL), and newborn larvae (NBL)). Subsequently, the in vitro phenotypic effects of P4, RU486, and rTs-MAPRC2-Ab on F-AL and ML stages were measured. Later, the in vivo phenotypic effect and relative mRNA expression of mifepristone on the F-AL stage were studied. Our results revealed that the Ts-MAPRC2 gene is critical to maintaining pregnancy in the female adult worm (F-AL) of T. spiralis. The 300 ng/mL of P4 and 100 ng/mL of RU486 showed downregulation of the Ts-MAPRC2 gene in F-AL (p ≤ 0.05). This plays an important role in abortion and possibly decreases the worm burden of T. spiralis in the host. Only 30 ng/mL P4 showed significant upregulation in F-AL (p ≤ 0.05). The current study provides new insights regarding the antihormone (P4 and RU486) drug design and vaccine therapy of recombinant (rTs-MAPRC2) protein as well as their combined effects to control T. spiralis infection.

The role of early life nutrition in programming of reproductive function

Accumulating evidence suggest that the concept of programming can also be applied to reproductive development and function, representing an ever expanding research area. Recently issues such as peri- or even preconceptional nutrition, transgenerational effects and underlying mechanisms have received considerable attention. The present chapter presents the existed evidence and reviews the available data from numerous animal and human studies on the effects of early life nutritional environment on adult reproductive function. Specific outcomes depend on the severity, duration and stage of development when nutritional perturbations are imposed, while sex-specific effects are also manifested. Apart from undernutrition, effects of relative overnutrition as well as the complex interactions between pre- and postnatal nutrition is of high importance, especially in the context of our days obesity epidemic. Mechanisms underlying reproductive programming are yet unclear, but may include a role for epigenetic modifications. Epigenetic modulation of critical genes involved in the control of reproductive function and potential intergenerational effects represent an exciting area of interdisciplinary research toward the development of new nutritional approaches during pre- and postnatal periods to ensure reproductive health in later life.

Changes in rat n-3 and n-6 fatty acid composition during pregnancy are associated with progesterone concentrations and hepatic FADS2 expression

The mechanisms responsible for changes to long-chain polyunsaturated fatty acid (LC PUFA) status during pregnancy have not been fully elucidated. Tissue samples were collected from virgin and pregnant (day 12 and 20) female rats. LC PUFA status, sex hormone concentrations and hepatic mRNA expression of FADS1, FADS2 and elongase were assessed. Day 20 gestation females had higher plasma and liver docosahexaenoic acid and lower arachidonic acid content than virgin females (P<0.05). There was higher FADS2 mRNA expression during pregnancy (P=0.051). Progesterone and oestradiol concentrations positively correlated with hepatic FADS2 mRNA expression (P=0.043, P=0.004). Progesterone concentration positively correlated with hepatic n-6 docosapentaenoic acid content (P=0.006), and inversely correlated with intermediates in LC PUFA synthesis including n-3 docosapentaenoic acid, γ-linolenic acid and 20:2n-6 (P<0.05). Changes in progesterone and oestradiol during pregnancy may promote the synthesis of LC PUFA via increased FADS2 expression.

Hyperglycaemia, stress oxidant, liver dysfunction and histological changes in diabetic male rat pancreas and liver: protective effect of 17 beta-estradiol

Oxidative stress is thought to play a crucial role in the pathogenesis of chronic diabetic complications. We investigated the protective effects of 17 beta-estradiol (E2) on alloxan-induced stress oxidant, hepatic dysfunction and histological changes in male rats liver and pancreas. Our results showed that 17 beta-estradiol could attenuate the increase of blood glucose in plasma and normalise the hepatic glycogen level. In addition, E2 enhanced superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) (by 207, 52 and 72%, respectively, as compared to diabetic rats), reduced lipid peroxidation in the hepatic tissue (by 54%) and improved the liver dysfunction parameters by the significant decrease of gamma-glytamyl transferase (GGT), phosphatases alkalines (PAL), lactate deshydrogenase (LDH) and aspartate and lactate transaminases (AST and ALT) activities which increased in diabetic rats. Moreover, 17 beta-estradiol treatment in diabetic rats protects against alloxan-induced pancreatic beta-cells and hepatic cells damages.

Metabolic modulators following trauma sepsis: Sex hormones

BACKGROUND

The development of metabolic perturbations following severe trauma/sepsis leading to decreased energy production, hyperglycemia, and lipolysis is often rapid. Gender is increasingly recognized as a major factor in the outcome of patients suffering from trauma/sepsis. Moreover, sex hormones influence energy, glucose, and lipid metabolism. Metabolic modulators, such as peroxisome proliferator-activated receptor-gamma coactivator-1 and peroxisome proliferator-activated receptor-alpha, which are required for mitochondrial energy production and fatty acid oxidation, are regulated by the estrogen receptor-beta and consequently contribute to cardioprotection following trauma hemorrhage. Additionally, sex steroids regulate inflammatory cytokines that cause hypermetabolism/catabolism via acute phase response, leading to increased morbidity and mortality.

MEASUREMENTS

This article examines the following: (1) the evidence for gender differences; (2) energy, glucose, and lipid metabolism and the acute phase protein response; (3) the mechanisms by which gender/sex hormones affect the metabolic modulators; and (4) the tissue-specific effect of sex hormone receptors and the effect of genomic and nongenomic pathways of sex hormones following trauma.

RESULTS AND CONCLUSIONS

The available information indicates that sex steroids not only modulate the immune/cardiovascular responses but also influence various metabolic processes following trauma. Thus, alteration or modulation of the prevailing hormone milieu at the time of injury appears to be a novel therapeutic adjunct for improving outcome after injury.

Imprinted gene expression in the rat embryo-fetal axis is altered in response to periconceptional maternal low protein diet

In our previous study, we have shown that maternal low protein diet (LPD, 9% casein vs 18% casein control) fed exclusively during the rat preimplantation period (0-4.25 day postcoitum) induced low birth weight, altered postnatal growth and hypertension in a gender-specific manner. In this study, we investigated the effect of maternal LPD restricted only to the preimplantation period (switched diet) or provided throughout gestation on fetal growth and imprinted gene expression in blastocyst and fetal stages of development. Male, but not female, blastocysts collected from LPD dams displayed a significant reduction (30%) in H19 mRNA level. A significant reduction in H19 (9.4%) and Igf2 (10.9%) mRNA was also observed in male, but not in female, fetal liver at day 20 postcoitum in response to maternal LPD restricted to the preimplantation period. No effect on the blastocyst expression of Igf2R was observed in relation to maternal diet. The reduction in H19 mRNA expression did not correlate with an observed alteration in DNA methylation at the H19 differentially methylated region in fetal liver. In contrast, maternal LPD throughout 20 days of gestation did not affect male or female H19 and Igf2 imprinted gene expression in fetal liver. Neither LPD nor switched diet treatments affected H19 and Igf2 imprinted gene expression in day 20 placenta. Our findings demonstrate that one contributor to the alteration in postnatal growth induced by periconceptional maternal LPD may derive from a gender-specific programming of imprinted gene expression originating within the preimplantation embryo itself.

Insulin sensitivity in streptozotocin-induced diabetic rats treated with different doses of 17beta-oestradiol or progesterone

It has been reported that in streptozotocin (STZ)-induced diabetes, hyperglycaemia leads to progressive insulin resistance of the peripheral tissues. In this study, we tried to elucidate the effects of hyperglycaemia on insulin sensitivity and insulin signalling in ovariectomized (STZ)-induced diabetic rats. In addition, we attempted to demonstrate the role of 17beta-oestradiol and progesterone on insulin sensitivity, focusing on their effects on key proteins of skeletal muscle, insulin receptor (IR) and glucose transporter-4 (Glut-4). Our results show that hyperglycaemia could modulate insulin signalling, at the IR and Glut-4 level, in different ways depending on exposure time. 17beta-Oestradiol and progesterone have different effects on insulin signalling. 17beta-Oestradiol treatment improves insulin sensitivity, but its action is dependent on the exposure time and its plasma level. During the early period of treatment (days 6-11), this hormone counteracts the effects of hyperglycaemia downstream of the IR, whereas during the later period of treatment (days 11-16), it may counteract the effects of hyperglycaemia by modulating IR relative tyrosine phosphorylation. By contrast, progesterone only improves insulin sensitivity during the early period of treatment (days 6-11), and this effect is not associated with changes in IR and Glut-4 content. Both hormones have a protective role in skeletal muscle against the effects of glucose toxicity, but their effects begin at different stages of treatment. These new findings improve our understanding of insulin resistance in type 1 diabetes mellitus and of the risk/benefit ratio when 17beta-oestradiol and progesterone are used in oral contraceptives or hormone replacement therapy taken by menopausal women with controlled type 1 diabetes mellitus.

Effect of food restriction on the insulin signalling pathway in rat skeletal muscle and adipose tissue

We tried to elucidate the effects of a brief and severe model of food restriction on insulin sensitivity in female rats, focusing on key proteins involved in the insulin signalling pathway in skeletal muscle and adipose tissue after 5, 10 and 15 days of food restriction. Using euglycemic clamp, we detected that food-restricted rats are significantly less sensitive to insulin action than control rats. However, the time of restriction promotes a progressive increase on insulin sensitivity. The analysis of the insulin signalling pathway showed a tissue-specific regulation of several proteins involved in insulin signalling. In skeletal muscle, insulin receptor substrate 1 and Glut4 are up-regulated at the end of the food restriction period, just the opposite of what we found in adipose tissue. In conclusion, a 50% reduction of food intake modulates insulin sensitivity through a tissue-specific regulation of the insulin signalling pathway in the main target tissues for this hormone.

In vitro and in vivo effects of progesterone on Trichinella spiralis newborn larvae

We have previously demonstrated that during pregnancy there exists an increased parasiticide activity against Trichinella spiralis newborn larvae (NBL) in infected rats. In this work we analysed the contribution of peritoneal cells from non-infected pregnant rats to the mortality of the NBL in cytotoxicity assays, and evaluated the role of progesterone in this effector mechanism. Our findings suggest that progesterone can induce activation of effector peritoneal cells to destroy the NBL in a rapid and antibody-independent manner. The administration of progesterone to ovariectomized rats also led to a significant decrease in the parasite load of the animals, thus demonstrating that progesterone induces the increase of the parasiticide activity of the leukocytes involved in the mechanisms of NBL death.

Myogenic reactivity is enhanced in rat radial uterine arteries in a model of maternal undernutrition

OBJECTIVES

The purpose of this study was to determine if maternal undernutrition during pregnancy altered myogenic tone in small radial uterine arteries.

STUDY DESIGN

Myogenic tone of radial uterine arteries was studied from late pregnant rats (day 20) that were fed either ad libitum or globally restricted diet (moderately severe dietary restriction) throughout pregnancy.

RESULTS

Myogenic tone was enhanced in the radial uterine arteries from the diet-restricted compared with the ad libitum group. Nitric oxide synthase inhibition enhanced myogenic tone in the arteries from the ad libitum group only. Prostaglandin H synthase inhibition had no effect on myogenic tone in either group.

CONCLUSION

Diet restriction during pregnancy enhances myogenic tone in the radial uterine arteries partly as a result of impairment of the nitric oxide synthase pathway. Enhanced myogenic tone in turn may reduce uteroplacental blood flow and, thus, contribute to reduced birth weight, and lead to effects of fetal programming in utero that can have long-term consequences into adulthood.

Regulation of insulin receptor substrate-1 in the liver, skeletal muscle and adipose tissue of rats throughout pregnancy

The mechanism responsible for insulin resistance during pregnancy remains unclear. Considerable evidence indicates that insulin receptor substrate-1 could play an important role in insulin sensitivity. It seems possible that the gestational hormonal milieu could affect insulin receptor substrate-1. In the present study, measurements of tyrosine phosphorylation and protein content of insulin receptor substrate-1 and gene expression in the liver, skeletal muscle and adipose tissue in the rat indicated that, during pregnancy, significant changes occurred in these parameters. We found in early gestation that muscle and adipose tissue were highly sensitive to insulin action, because the phosphorylation of insulin receptor substrate-1 is greater than in late gestation. However, in late gestation the tissue most sensitive to insulin action, reflecting insulin receptor substrate-1 phosphorylation, was the liver. Our hypothesis was that these results are connected with the changes in concentrations of estradiol and progesterone observed during pregnancy. It was concluded that the present findings demonstrate that different concentrations of gestational hormones play an important role in insulin sensitivity in this period, and that each tissue responds in the most appropriate manner to guarantee the gestation in its entirety, controlling the phosphorylation of insulin receptor substrate-1 in response to insulin receptor activation.

Role of 17beta-estradiol administration on insulin sensitivity in the rat: implications for the insulin receptor

The role of 17beta-estradiol in the early steps of insulin action is only partially known, although its effect on glucose homeostasis has been reported. In this paper, we attempt to prove the influence of 17beta-estradiol on the insulin receptor of ovariectomized rats treated with different hormonal doses. Our results show that high doses of estradiol impair insulin sensitivity while low doses improve it. We think that these results are the consequence of changes at a molecular level, because high doses of estradiol produced lower expression of the insulin receptor gene, lower content of this receptor in target tissues, and lower phosphorylation of insulin receptor in these tissues. However, low doses of estradiol seem to produce just the opposite. The possible existence of consensus response elements in the insulin receptor gene promoter to estradiol could be controlling the expression of this gene, this control being dose and timing dependent. Moreover, we cannot discard a possible effect of estradiol on the activity of protein tyrosine phosphatases, and therefore, on the activity of the insulin receptor. These new findings improve knowledge about the possible risk for insulin resistance in women taking oral contraceptives or receiving hormonal replacement therapy around the menopause, but could also open the door towards the possible utilization of 17beta-estradiol in some diabetes cases.

Vasodilation to vascular endothelial growth factor in the uterine artery of the pregnant rat is blunted by low dietary protein intake

Pregnancy is associated with a substantial increase in uterine artery blood flow, which may in part result from dilation in response to vascular endothelial growth factor (VEGF). Uterine blood flow is reported to be reduced in globally diet-restricted pregnant rats. Both global and protein dietary restriction in pregnancy produce programmed effects in offspring. In this study we hypothesized that protein restriction in pregnancy impairs maternal uterine artery responses to VEGF. Vascular responses to VEGF were determined in isolated uterine arteries of pregnant (18 or 19 d of gestation) Wistar rats fed a diet containing either 18% or 9% casein throughout pregnancy. For comparison, responses to phenylephrine, potassium chloride, and acetylcholine were determined. In addition, the response of the mesenteric artery to VEGF was studied in the same animals. A significant reduction of the maximal relaxation to VEGF (p = 0.041) and in the overall response (p = 0.004) to VEGF was found in uterine arteries of the 9% compared with the 18% group, but responses to all other agonists were similar. The VEGF response was reduced by cyclooxygenase inhibition (indomethacin) in both groups. In the 18%, but not the 9%, group it was further reduced by nitric oxide synthase inhibition (Nomega-nitro-L-arginine methyl ester). VEGF was shown to dilate the mesenteric artery but this effect was not significantly altered by the low-protein diet. These results show an attenuated uterine artery vasodilator response to VEGF produced by a low-protein diet in pregnancy, partly because of a reduction of the nitric oxide component of VEGF-mediated relaxation.

Effect of treatment with different doses of 17-beta-estradiol on the insulin receptor

The mechanism for the development of insulin resistance in normal pregnancy is complex and is associated with serum levels of sex hormones. However, the influence of these hormones on the early steps of insulin action has not been extensively studied, although the potentially beneficial effect of estradiol on glucose homeostasis has been reported. In this paper, we attempted to determine the effect of 17-beta-estradiol on the insulin receptor of ovariectomized rats treated with different doses of hormones. Our results showed a tissue-dependent response to estradiol. We found that low doses of estradiol increased the amount of insulin receptors in liver and muscle on days 6 and 11 of treatment but not in adipose tissue, and after 16 days only the muscle responsed in this way. On the other hand, high doses of estradiol significantly decreased the amount of insulin receptors, at least in muscle and adipose tissue. We believe that the low concentrations of 17-beta-estradiol (similar to early pregnancy) could be responsible for the increase in insulin sensitivity by increasing the amount of insulin receptors in peripheral tissues. When the hormone levels were high (similar to late pregnancy) the amount of insulin receptors decreased in peripheral tissues, and insulin sensitivity is diminished just as in late pregnancy. The specific molecular mechanism for this action is as yet unknown.