Glucose homeostasis in rats treated with 4-vinylcyclohexene diepoxide is not worsened by dexamethasone treatment

Gonadotropin upregulates intraovarian calpains-1 and -2 during ovarian follicular recruitment in the SD rat model

Calpain role has been shown in the cumulus cell-oocyte complexes and, corpus luteum. We investigated the association of calpains-1 and -2 in ovarian folliculogenesis using the Sprague-Dawley (SD) rat model and steroidogenesis in the human granulosa cells (hGCs). We induced PCOS in 42-day-old SD rats by letrozole oral gavage for 21 days. Premature ovarian failure (POF) was induced in 21-day-old SD rats by 4-vinylcyclohexene diepoxide (VCD). Ovulation and ovarian hyperstimulatory (OHS) syndrome were induced by pregnant mare gonadotropin (PMSG) + human chorionic gonadotropin (hCG) treatments in 21 days SD rats, respectively. Steroidogenesis is stimulated in human granulosa cells (hGCs) by forskolin and the response of 17-beta-estradiol (E2) on calpains expression was checked in hGCs. The protein expression by immunoblotting and activity by biochemical assay of calpains-1 and -2 showed an oscillating pattern in the ovarian cycle. PMSG-induced follicular recruitment showed upregulation of calpains-1 and -2, but with no change during ovarian function cessation (POF). Upregulated calpain-2 expression and calpain activity was found in the hCG +PMSG-induced ovulation. Letrozole-induced PCOS showed downregulation of calpain-1, but upregulation of calpain-2. PMSG+hCG-induced OHS led to the upregulation of calpain-1. Letrozole and metformin separately increased the expression level of calpains-1 and -2 in the hGCs during luteinization. In conclusion, the expression levels of calpains -1 and -2 are increased with ovarian follicular recruitment by PMSG and calpain-1 is decreased in the PCOS condition, and letrozole and metformin upregulate the expression of calpains-1 and -2 during luteinization in the hGCs possibly via E2 action.

4-vinylcyclohexene diepoxide induces premature ovarian insufficiency in rats by triggering the autophagy of granule cells through regulating miR-144

This research explored the pathological and molecular mechanisms of 4-vinylcyclohexene diepoxide (VCD)-induced POI model. QRT-PCR was exploited to detect miR-144 expression in the peripheral blood of POI patients. Rat and KGN cells were treated with VCD to construct POI rat or cell model, respectively. After miR-144 agomir or MK-2206 treatment, miR-144 level, follicle damage, autophagy level and expressions of key pathway-related proteins in rats were detected, and cell viability and autophagy in KGN cells were detected. MiR-144 was apparently down-regulated in the peripheral blood of POI patients. Decreased miR-144 was viewed in both the serum and ovary of rats, yet this trend was apparently reversed by miR-144 agomir. The increased concentration of Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH), along with decreased concentration of E2 and AMH, was observed in the serum of model rats, which was conspicuously negated by control agomir or miR-144 agomir. Increased number of autophagosomes, up-regulated PTEN, and inactivated AKT/m-TOR pathway induced by VCD in ovary tissues were strikingly offset by miR-144 agomir. Results of cytotoxicity assay revealed that 2 mM VCD prominently repressed KGN cell viability. In vitro experiments confirmed that miR-144 interfered with the effect of VCD on autophagy in KGN cells through the AKT/mTOR pathway. Taken together, VCD triggers autophagy to induce POI after targeting the AKT pathway by inhibiting miR-144, it suggest that up-regulation the expression of miR-144 may have the potential to treat POI.

PKC-βII is downregulated in the premature ovarian failure SD rat model

We investigated the role of protein kinase c (PKC) -α and -β during the ovarian follicular dynamics using estrous cycle, gonadotropin-induced ovulation, and antral follicle culture, 4-vinylcyclohexene diepoxide (VCD)-induced premature ovarian failure (POF) in the SD rat models. We found the higher activity of PKC during the proestrus stage along with expression of PKC-α during the estrus and metestrus stages of the estrous cycle while PKC-β expression was increased during the diestrus, proestrus, and estrus stages. In response to pregnant mare gonadotropin (PMSG)-induced follicular recruitment and ovulation, the phosphorylated (Thr-642) PKC-β was increased. PKC activity inhibition by hispidin during the proestrus stage resulted in decreased antral follicles and corpus luteum. Treatment with hispidin resulted in the downregulation of granulosa cell (GC) biomarker, follicle stimulating hormone receptor (FSHR) expression in the cultured pre-antral follicle. During the forskolin-induced luteinization of human granulosa cells, the expression level of PKC-α and β (I and II) was decreased. In the POF condition, the activity of total PKC and the expression levels of PKC-α and β (I and II) were increased. Immunostaining depicted ubiquitous expression of PKC-α in the ovary during the estrous cycle and POF conditions. Taken together, we conclude the association of PKC-α and -β (I and II) during ovarian follicular dynamics where the expression level of PKC-α is increased, but the expression level of PKC-β (I and II) is suppressed in the POF condition in the SD rat model.

A remarkable rodent: Regeneration and reproduction in spiny mice (Acomys)

Although certain organisms are chosen and employed to better understand a specific problem in biology (so-called model organisms), sometimes an animal model reveals its' biomedical importance by happenstance. In many ways, the advent of spiny mice (Acomys) as an emerging model to study regeneration and menstruation stands as a case study in scientific pseudoserendipity (Diaz de Chumaceiro, 1995). As we recount in this chapter, the discovery of these phenotypes, while not entirely accidental, was nonetheless unexpected. In addition to recounting how we uncovered these unusual mammalian traits, we outline recent work by our groups and others that has begun to outline the cellular and genetic mechanisms underlying bonafide mammalian tissue regeneration and a human-like mode of reproduction in spiny mice.

Maternal vitamin D administration attenuates metabolic disturbances induced by prenatal exposure to dexamethasone in a sex-dependent manner

PURPOSE

The overexposure to synthetic glucocorticoids (GC) during pregnancy can predispose to metabolic diseases during adulthood. Vitamin D is not only crucial for fetal development, but also exerts direct effects on the GC sensitivity and down-regulates GC receptors. Given the vitamin D effects on glucocorticoid-related parameters, we aimed to investigate a possible protective role of maternal vitamin D administration on the glucose homeostasis of rats exposed to dexamethasone in utero.

METHODS

Pregnant rats received dexamethasone (0.1 mg/kg, Dex) daily between the 14th and 19th days of pregnancy. A subgroup of dexamethasone-treated dams received oral administration of vitamin D (500UI, DexVD) during the whole gestation. The corresponding control groups of dams were included (CTL and VD groups, respectively). Male and female offspring were evaluated at 3, 6 and 12 months of age.

RESULTS

Prenatal exposure to dexamethasone caused metabolic disruption in an age and sex-dependent manner being the older male offspring more susceptible to insulin resistance, fatty liver and beta-cell mass expansion than females. Furthermore, we demonstrated that prenatal GC led to glucose intolerance in male and female offspring in an age-dependent manner. Maternal vitamin D administration did not influence glucose intolerance but attenuated the insulin resistance, liver lipid accumulation and prevented the beta-cell mass expansion caused by prenatal dexamethasone in the male offspring.

CONCLUSION

Maternal vitamin D administration mitigates metabolic disturbances that occur later in life in male rats exposed to GC in utero. Moreover, our data suggest vitamin D as an important nutritional supplement for pregnant overexposed to GC during gestation.

Epigenetic repression of AT2 receptor is involved in β cell dysfunction and glucose intolerance of adult female offspring rats exposed to dexamethasone prenatally

Prenatal exposure to dexamethasone (PDE) impairs pancreatic β cell development and glucose homeostasis in offspring especially females. To explore the underlying intrauterine programming mechanism, pregnant Wistar rats were subcutaneously administered with dexamethasone (0, 0.2 and 0.8 mg/kg·d) from gestational days (GD) 9 to 20. Female offspring were collected on GD20 (fetus) and in postnatal week 28 (adult), respectively. PDE reduced the serum insulin levels, β cell mass, and pancreatic insulin expressions in fetuses and adults, causing glucose intolerance after maturity. The persistent suppression of pancreatic angiotensin II receptor type 2 (AT2R) expression before and after birth could be observed in the PDE females, which is accompanied with decreased histone 3 lysine 14 acetylation (H3K14ac) and H3K27ac levels in AT2R promoter. PDE increased the gene expressions of glucocorticoid receptor (GR) and histone deacetylase 2 (HDAC2) in fetal pancreas. Furthermore, dexamethasone inhibited insulin biosynthesis while activated GR and HDAC2 expression in the rat INS-1 cells. The AT2R expression was repressed by dexamethasone in vitro but only H3K27ac levels in AT2R promoter were lowered. Dexamethasone enhanced the interaction between GR and HDAC2 proteins as well as the binding of GR/HDAC2 complex to AT2R promoter. Moreover, overexpression of AT2R could restore the suppressed insulin biosynthesis induced by dexamethasone in vitro, and both GR antagonist and histone deacetylase abolished the decreased H3K27ac level and gene expression of AT2R. In conclusion, continuous epigenetic repression of AT2R before and after birth may be involved in β cell dysfunction and glucose intolerance of the PDE adult female offspring.

Endocrine profile of the VCD-induced perimenopausal model rat

During the transition to menopause, women experience a variety of physical and psychological symptoms that are directly or indirectly linked to changes in hormone secretion. Establishing animal models with intact ovaries is essential for understanding these interactions and finding new therapeutic targets. In this study, we assessed the endocrine profile, as well as the estrous cycle, in the 4-vinylcyclohexene diepoxide (VCD)-induced follicular depletion rat model in 10-day intervals over 1 month to accurately establish the best period for studies of the transition period. Twenty-eight-day-old female rats were injected daily with VCD or oil s.c. for 15 days and euthanized in the diestrus phase approximately 70, 80, 90 and 100 days after the onset of treatment. The percentage of rats showing irregular cycles and the plasma level of FSH increased only in the 100-day VCD group. Plasma anti-Müllerian hormone (AMH) and progesterone were lower in all VCD groups compared to control groups, while estradiol remained unchanged or higher. As in control groups, dihydrotestosterone (DHT) progressively decreased in the 70-90-day VCD groups; however, it was followed by a sharp increase only in the 100-day VCD group. No changes were found in plasma corticosterone, prolactin, thyroid hormones or luteinizing hormone. Based on the estrous cycle and endocrine profile, we conclude that 1) the time window from 70 to 100 days is suitable to study a perimenopause-like state in this model, and 2) regular cycles with low progesterone and AMH and normal FSH can be used as markers of the early/mid-transition period, whereas irregular cycles associated with higher FSH and DHT can be used as markers of the late transition period to estropause.

Pancreastatin inhibitor, PSTi8 ameliorates metabolic health by modulating AKT/GSK-3β and PKCλ/ζ/SREBP1c pathways in high fat diet induced insulin resistance in peri-/post-menopausal rats

Increase in the prevalence of insulin resistance (IR) in peri-/post-menopause women is mainly due to hormone deficiency and lifestyle. PSTi8 (PEGKGEQEHSQQKEEEEEMAV-amide) is a pancreastatin inhibitor peptide which showed potent antidiabetic activity in genetic and lifestyle induced type 2 diabetic mice. In the present work, we have investigated the antidiabetic activity of PSTi8 in rat models of peri-/post-menopausal IR. 4-vinylcyclohexenediepoxide treated and ovariectomized rats were fed with high fat diet for 12 weeks to develop the peri-/post-menopausal IR. PSTi8 peptide was administered after the development of peri-/post-menopausal IR rats. PSTi8 (1 mg/kg, i.p) improved the glucose homeostasis which is characterized by elevated glycogenesis, enhanced glycolysis and reduced gluconeogenesis. PSTi8 suppressed palmitate- and PST- induced IR in HepG2 cells. PSTi8 treatment enhanced energy expenditure in peri-/post-menopausal IR rats. PSTi8 treatment increased insulin sensitivity in peri-/post-menopausal IR rats, may be mediated by modulating IRS1-2-phosphatidylinositol-3-kinase-AKT-GSK3β and IRS1-2-phosphatidylinositol-3-kinase-PKCλ/ζ-SREBP1c signaling pathways in the liver. PSTi8 can act as a potential therapeutic peptide for the treatment of peri-/post-menopausal IR.

Influence of the physical exercise on decrease in the gastric emptying and alter appetite and food behavior in rats dexamethasone-treatment

The chronic use of Dexamethasone (Dex) induced hyperglycemia and insulin resistance. On the other hand, physical exercise attenuates the symptoms induced by Dex in many physiological systems. However, the effect of the exercise on the changes in gastric motility induced by dexamethasone remains unknown. We hypothesized that low-intensity aerobic exercise modulates the metabolic effects induced by Dex-treatment by modifying the gastrointestinal function and feeding behavior in rats. Male rats were distributed into the following groups: Control (Ctrl), Dex (1.0 mg/kg, i.p.), Exercise (Ctrl + Exercise 5%) and (Dex1.0 + Exercise 5%). The exercise protocol was swimming for 5 consecutive days. We assessed the murinometric and nutritional indices, food intake, blood glucose by (ipGTT) and the gastric emptying rate of a liquid test meal were assessed in all rats. We observed a significant decrease (p < .05) in the gastric emptying in Dex1.0 group in relation to Ctrl group. The exercise prevented decrease in the gastric emptying (p < .05) in Dex1.0 + EX5% group when compared with Dex1.0 groups. The Dex1.0 group induced a significantly increase (p < .05) in glycaemia vs Ctrl group. The hyperglycemia was improving (p < .05) in the Dex1.0 + Ex5% compared with Dex1.0 groups. We observed a positive correlation (p < .05, and r = 0.7065) between gastric retention vs glycaemia in the Dex1.0 groups. The Dex1.0 reduced (p < .05) the body weight and altered body composition, promoting hypophagia. IL-6 increased (p < .05) at gastric fundus in Ex5% compared with Ctrl groups. In conclusion, the use of Dex1.0 decreases gastric emptying, promotes hyperglycemia and modifies feeding behavior. The low-intensity exercise prevents hyperglycemia, thus improving gastric dysmotility without improving the anthropometric parameters.

Dexamethasone Administration During Late Gestation Has No Major Impact on Lipid Metabolism, but Reduces Newborn Survival Rate in Wistar Rats

A rise in plasma triacylglycerol levels is a common physiological occurrence during late gestation and excess of glucocorticoids (GCs) has been shown to impair lipid metabolism. Based on those observations, we investigated whether the administration of dexamethasone during the late gestational period could exacerbate this pregnancy associated hypertriacylglycerolemia in rats. For this, female Wistar rats were treated with dexamethasone (0.2 mg/kg of body mass in the drinking water on days 14-19 of pregnancy; DP group) or equivalent days in the virgin rats (DV group). Untreated pregnant rats (control pregnant group) and age-matched virgin rats (control virgin group) were used as controls. Functional, biochemical, and molecular analyses were carried out after treatment with GC and in the control groups. Euthanasia was performed on day 20 of pregnancy. The metabolic parameters of the mothers (dams) at the time of weaning and 6 months later, as well as newborn survival, were evaluated. We observed that neither dexamethasone nor pregnancy affected blood glucose or glucose tolerance. Hypertriacylglycerolemia associated with lipid intolerance or reduced hepatic triacylglycerol clearance was observed during the late gestational period. GC treatment caused a further increase in basal plasma triacylglycerol levels, but did not have a significant effect on lipid tolerance and hepatic triacylglycerol clearance in pregnant rats. GC, but not pregnancy, caused few significant changes in mRNA expression of proteins involved in lipid metabolism. Dexamethasone during pregnancy had no impact on lipid metabolism later in the dams' life; however, it led to intra-uterine growth restriction and reduced pup survival rate. In conclusion, GC exposure during the late gestational period in rats has no major impact on maternal lipid homeostasis, soon after parturition at weaning, or later in the dams' life, but GC exposure is deleterious to the newborn when high doses are administered at late gestation. These data highlight the importance of performing an individualized and rigorous control of a GC treatment during late pregnancy considering its harmful impact on the fetuses' health.

Influence of the fish oil in the gut microbiota of wistar rats (Rattus norvegicus) treated with dexamethasone and amoxicillin

The widespread use of antibiotics and anti-inflammatory has been more and more prominent. In spite of the proven pharmacological potential, its collateral effects are still being described. The fish oil is made of acids fatty polyunsaturated, as the omega 3. The aim of this paper is to check if there would be interference of this fish oil in the gut microbiota of rats when treated with dexamethasone and amoxicillin, joining with the parameter lipids and glycemic. This study was done with 42 Wistar rats, divided into 6 groups with 7 animals each: naive (CTL), amoxicillin (AMOX), dexamethasone (DEX), fish oil (OLP), associated amoxicillin and fish oil (AMOX + OLP) association dexamethasone and fish oil (DEX + OLP). The results show that the fish oil influenced in the concentration of blood glucose in the animals, keeping stable levels even after a pool of glucose. Differently, the fish oil increased the levels of LDL in the animals. The amoxicillin changed the mass of liver and spleen, changed the levels of triglyceride and changed the gut microbiota. The dexamethasone influenced the lipids parameters and mass of the spleen as well as it slightly increased the amount of cholesterol LDL. It is possible to conclude that fish oil increases the levels of LDL in the tested model and the dose tested, but is able to maintain glucose levels even after a pool of the same, and can be a preventive model with hyperglycemia.

Cardiovascular Autonomic Responses in the VCD Rat Model of Menopause: Effects of Short- and Long-Term Ovarian Failure

After menopause, hypertension elevates the risk of cardiac diseases, one of the major causes of women's morbidity. The gradual depletion of ovarian follicles in rats, induced by 4-vinylcyclohexene diepoxide (VCD), is a model for studying the physiology of menopause. 4-Vinylcyclohexene diepoxide treatment leads to early ovarian failure (OF) and a hormonal profile comparable to menopause in humans. We have hypothesized that OF can compromise the balance between sympathetic and parasympathetic tones of the cardiovascular system, shifting toward dominance of the former. We aimed to study the autonomic modulation of heart and blood vessels and the cardiovascular reflexes in rats presenting short-term (80 days) or long-term (180 days) OF induced by VCD. Twenty-eight-day-old Wistar rats were submitted to VCD treatment (160 mg/kg, intraperitoneally) or vehicle (control) for 15 consecutive days and experiments were conducted at 80 or 180 days after the onset of treatment. Long-term OF led to an increase in the sympathetic activity to blood vessels and an impairment in the baroreflex control of the heart, evoked by physiological changes in arterial pressure. Despite that, long-term OF did not cause hypertension during the 180 days of exposure. Short-term OF did not cause any deleterious effect on the cardiovascular parameters analyzed. These data indicate that long-term OF does not disrupt the maintenance of arterial pressure homeostasis in rats but worsens the autonomic cardiovascular control. In turn, this can lead to cardiovascular complications, especially when associated with the aging process seen during human menopause.