Roles of thyroid hormones in follicular development in the ovary of neonatal and immature rats

Ferroptosis: First evidence in premature duck ovary induced by polyvinyl chloride microplastics

Ferroptosis is frequently observed in fibrosis and diseases related to iron metabolism disorders in various mammalian organs. However, research regarding the damage mechanism of ferroptosis in the female reproductive system of avian species remains unclear. In this study, Muscovy female ducks were divided into three groups which were given purified water, 1 mg/L polyvinyl chloride microplastics (PVC-MPs) and 10 mg/L PVC-MPs for two months respectively, to investigate the ferroptosis induced by PVC-MPs caused ovarian tissue fibrosis that lead to premature ovarian failure. The results showed that the high accumulation of PVC-MPs in ovarian tissue affected the morphology and functional activity of ovarian granulosa cells (GCs) and subsequently caused the follicular development disorders and down-regulated the immunosignaling of ovarian steroidogenesis proteins 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), CYP11A1 cytochrome (P450-11A1) and CYP17A1 cytochrome (P450-17A1) suggested impaired ovarian function. In addition, PVC-MPs significantly up-regulated positive expression of collagen fibers, significantly increased lipid peroxidation and malondialdehyde (MDA) level, along with encouraged overload of iron contents in the ovarian tissue were the characteristics of ferroptosis. Further, immunohistochemistry results confirmed that immunosignaling of ferroptosis related proteins Acyl-CoA synthetase (ACSL4), Cyclooxygenase 2 (COX2) and ferritin heavy chain 1 (FTH1) were significantly increased, but solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase (GPX4) were decreased by PVC-MPs in the ovarian tissue. In conclusion, our study demonstrates that PVC-MPs induced ferroptosis in the ovarian GCs, leading to follicle development disorders and ovarian tissue fibrosis, and ultimately contributing to various female reproductive disorders through regulating the proteins expression of ferroptosis.

Associations between a normal-range free thyroxine concentration and ovarian reserve in infertile women undergoing treatment via assisted reproductive technology

BACKGROUND

Some recent studies have shown that female subclinical hypothyroidism (SCH) is associated with diminished ovarian reserve (DOR). In this study, we aimed to investigate whether serum-free thyroxine (fT4) concentrations within the reference range are associated with ovarian reserve in women.

METHODS

This cross-sectional study included 4933 infertile women with normal-range fT4 concentrations who received assisted reproductive technology treatment in our clinic. The data of women in different fT4 concentration tertiles (namely 12-15.33, 15.34-18.67, and 18.68-22 pmol/L) were compared with ovarian reserve markers, namely the anti-Müllerian hormone (AMH) concentration, the antral follicle count (AFC), and the number of aspirated oocytes. The primary outcomes were the AMH concentration and the risk of DOR, diagnosed as an AMH concentration < 1.1 ng/mL.

RESULTS

The average ages of women in the low-normal, middle-normal, and high-normal fT4 tertiles were 33.20 (standard deviation [SD]: 5.11), 32.33 (SD: 5.13), and 31.61 (SD: 5.10) years, respectively (p < 0.0001). AMH concentrations (adjusted mean: 3.32 [95% confidence interval {CI}: 3.16 to 3.50] vs. 3.51 [3.40 to 3.62] vs. 3.64 [3.50 to 3.80] ng/mL, p = 0.022) were significantly different between the fT4 concentration tertiles. The risk of DOR was significantly increased in the low-normal (adjusted odds ratio: 1.61 [95% CI: 1.01 to 2.58]) and middle-normal (1.47 [95% CI: 1.00 to 2.16]) tertiles compared with the high-normal tertile. Subgroup analysis showed that AMH concentrations were significantly different among the fT4 concentration tertiles in women aged < 35 years (adjusted mean: 3.94 [95% CI: 3.70 to 4.20] vs. 4.25 [4.11 to 4.39] vs. 4.38 [4.18 to 4.58], p = 0.028), whereas this difference was not significant in women aged ≥ 35 years (p = 0.534). The general additive models using fT4 as a continuous variable indicated that a lower fT4 concentration within the normal range was significantly associated with a lower AMH concentration (p = 0.027), a lower AFC (p = 0.018), a lower number of aspirated oocytes (p = 0.001), and a higher risk of DOR (p = 0.007).

CONCLUSION

Low-normal fT4 concentrations are associated with lower ovarian reserve in infertile women.

Autoimmune thyroid disease and ovarian hypofunction: a review of literature

Thyroid hormones(THs) are essential for the proper functioning of the ovaries, and multiple studies have shown that thyroid abnormalities, especially during adolescence and reproductive age, can lead to lifelong ovarian dysfunction. Autoimmune thyroid disease (AITD), one of the most common organ specific autoimmune diseases, is mainly mediated by cellular autoimmune reactions, and has strong inflammatory infiltration and immune active cells, including chemokines and cytokines, which are important components of ovarian aging. This suggests that autoimmune and inflammatory molecular processes may play a role in the emergence of ovarian dysfunction. The purpose of this review is to summarize recent in vivo and in vitro evidence of a complex relationship between AITD and ovarian dysfunction. AITD is closely related to the decline of ovarian function from the perspective of antibody, cytokine, oxidative stress, and genetic factors. Finally, some of the currently known treatments for AITD and hypo ovarian disease are summarized.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

Mendelian randomization study of thyroid function and anti-Müllerian hormone levels

Objective

Although previous studies have reported an association between thyroid function and anti-Müllerian hormone (AMH) levels, which is considered a reliable marker of ovarian reserve, the causal relationship between them remains uncertain. This study aims to investigate whether thyrotropin (TSH), free thyroxine (fT4), hypo- and hyperthyroidism are causally linked to AMH levels.

Methods

We obtained summary statistics from three sources: the ThyroidOmics Consortium (N = 54,288), HUNT + MGI + ThyroidOmics meta-analysis (N = 119,715), and the most recent AMH genome-wide association meta-analysis (N = 7,049). Two-sample MR analyses were conducted using instrumental variables representing TSH and fT4 levels within the normal range. Additionally, we conducted secondary analyses to explore the effects of hypo- and hyperthyroidism. Subgroup analyses for TSH were also performed.

Results

MR analyses did not show any causality relationship between thyroid function and AMH levels, using normal range TSH, normal range fT4, subclinical hypothyroidism, subclinical hyperthyroidism and overt hypothyroidism as exposure, respectively. In addition, neither full range TSH nor TSH with individuals <50 years old was causally associated with AMH levels. MR sensitivity analyses guaranteed the robustness of all MR results, except for the association between fT4 and AMH in the no-DIO1+DIO2 group.

Conclusion

Our findings suggest that there was no causal association between genetically predicted thyroid function and AMH levels in the European population.

Impact of photoperiod on uterine redox/inflammatory and metabolic status of golden hamster, Mesocricetus auratus

Photoperiod modulates reproductive physiology at multiple levels in seasonally breeding animals. Golden hamsters are long-day breeders that diminish their fertility during the short days. Photoperiod is known to regulate hormonal milieu and uterus is a hormone-sensitive dynamic tissue. However, there is lack of molecular insight regarding the impact of photoperiod on uterine physiology with respect to redox and metabolic status in Mesocricetus auratus. We evaluated the impact of photoperiod on circulatory hormonal parameters (triiodothyronine [T3], thyroxin [T4], estradiol [E2], progesterone [P4], melatonin, and insulin), their receptor expressions and key markers associated with redox (SIRT-1/FOXO-1), inflammatory (NFĸB/COX-2) and metabolic (IR/GLUT4) status in uterus. Adult female golden hamsters were exposed to different photoperiodic regimes, that is, short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. SP drastically decreased peripheral hormone profiles (T3, T4, E2, and P4) and compromised uterine histoarchitecture when compared with LP-exposed hamsters. Further, SP markedly decreased thyroid hormone receptor-α (TRα), insulin receptor, and glucose uptake transporter-4 (GLUT-4) expressions in uterus. We noted enhanced uterine oxidative (increased MDA and decreased SOD/CAT levels), SIRT-1/FOXO-1 expression and inflammatory (NFĸB/COX-2) load in SP condition. Further, elevated levels of circulatory insulin, melatonin, and its receptor (MT-1) expression in uterus was noted under SP condition. Thus, we may suggest that photoperiod might regulate uterine seasonality through modulation of local hormonal and redox/metabolic homeostasis thereby may restrict offspring bearing capacity under short days.

How to Differentiate General Toxicity-Related Endocrine Effects from Endocrine Disruption: Systematic Review of Carbon Disulfide Data

This review provides an overview of the assessment of the endocrine disrupting (ED) properties of carbon disulfide (CS₂), following the methodology used at the European level to identify endocrine disruptors. Relevant in vitro, in vivo studies and human data are analyzed. The assessment presented here focuses on one endocrine activity, i.e., thyroid disruption, and two main adverse effects, neurotoxicity and cardiotoxicity. The data available on the different ED or non-ED modes of action (MoA), known to trigger these adverse effects, are described and the strength of evidence of the different MoA is weighted. We conclude that the adverse effects could be due to systemic toxicity rather than endocrine-mediated toxicity. This assessment illustrates the scientific and regulatory challenges in differentiating a specific endocrine disruption from an indirect endocrine effect resulting from a non-ED mediated systemic toxicity. This issue of evaluating the ED properties of highly toxic and reactive substances has been insufficiently developed by European guidance so far and needs to be further addressed. Finally, this example also raises questions about the capacity of the technics available in toxicology to address such a complex issue with certainty.

Vitamin D improves oxidative stress and histopathological damage in rat ovaries caused by hyperthyroidism

OBJECTIVE

The aim of this study is to investigate the histopathological and biochemical efficacy of vitamin D on oxidative damage and fibrosis in rat ovaries induced by experimental hyperthyroidism.

METHODS

This study is a comparative, prospective experimental rat study. Sprague-Dawley female rats were divided into four groups. Only distilled water was given to the rats in group 1 for 25 days. In group 2, 100 μg/day L-thyroxine was given to rats for 25 days. In Group 3, 100 μg/day L-thyroxine and 200 IU/day vitamin D were given to rats for 25 days. In group 4, only 200 IU/day vitamin D was administered for 25 days.

RESULTS

This study is the first to demonstrate the protective effect of vitamin D against ovarian damage caused by experimental hyperthyroidism. Hyperthyroidism caused fibrotic degenerative changes in the ovaries and an increase in the fibrillin 1 score. It caused serum follicle-stimulating hormone (FSH) levels to increase and serum E2 levels to decrease. In addition, malondialdehyde (MDA) and total oxidant status (TOS) levels increased in rats with hyperthyroidism. Vitamin D decreased MDA and TOS values and increased total antioxidant status (TAS) values in rats with hyperthyroidism. It also increased TSH values by causing a decrease in TT3 and TT4 values. It decreased fibrosis, follicle degeneration, stromal degeneration, and fibrillin 1 score in ovarian tissue.

CONCLUSION

Vitamin D has positive histopathological and biochemical effects on the oxidative stress and follicle damage caused by hyperthyroidism in ovarian tissue. Human studies with larger case populations should be conducted to evaluate the effects and clinical applications of vitamin D.

The Interplay Between Hyperthyroidism and Ovarian Cytoarchitecture in Albino Rats

Background

Hyperthyroid females often complain of menstrual disturbances and impaired fertility. This study was designed to observe the effect of hyperthyroidism on ovarian folliculogenesis and the hypophyseal-gonadal axis.

Methodology

Adult female Wistar albino rats (n= 12), six to eight weeks of age, and weighing 70-162 g, were divided randomly into control (Group A) and experimental (Group B) groups. Group A received daily intraperitoneal injections of 250 µL normal saline (10 µL 5 µM NaOH dissolved in it) for 14 days. Group B received a daily intraperitoneal injection of levothyroxine (600 µg/kg body weight) to induce hyperthyroidism. Rats were weighed at the start and the end of the experimental period on the day of sacrifice.

Results

Statistical analysis of the data revealed successful induction of hyperthyroidism in Group B as their thyroid-stimulating hormone (TSH) levels decreased significantly. The ovarian size was significantly reduced in the hyperthyroid group (p < 0.029). There was a significant decrease in thickness of the ovarian capsule (p < 0.000), an increase in the number of primordial, primary, and secondary follicles (p < 0.001, 0.000, and 0.001, respectively), and a decrease in size of primary and secondary follicles (p < 0.041 and 0.020) in the hyperthyroid group.

Conclusion

Hyperthyroidism can affect ovarian cytoarchitecture, probably by acting directly on its receptors and thus affects female fertility.

The effects of chronic lead exposure on the ovaries of female juvenile Japanese quails (Coturnix japonica): Developmental delay, histopathological alterations, hormone release disruption and gene expression disorder

Lead (Pb) is well-recognized for its great hazards to human and wildlife health. It has negative influences on multiple organs and systems of birds. Especially, lead exposure caused adverse impacts on bird reproduction. In this study, one week old female Japanese quails were randomly allocated into four groups and each group was respectively fed with 0, 50 ppm, 500 ppm and 1000 ppm Pb in drinking water for 36 days to determine the effects of chronic lead exposure on ovarian development and function. The results showed that Pb did accumulate in the ovary and ovarian development was delayed by high dose lead exposure (500 ppm and 1000 ppm). Moreover, high Pb dosage induced ovarian histopathological damages characterized by granulosa cells disorganization, follicle atresia and interstitial cell degeneration. Meanwhile, the concentration of estradiol (E2) was significantly decreased and mRNA levels of genes involved with ovarian steroidogenesis were significantly down-regulated by high concentration Pb. In addition, Pb exposure caused increasing cell apoptosis and significant changes of the expression of genes involved with cell death in the ovary. High dose Pb exposure also inhibited thyroid hormone release and disrupted ovarian thyroid deiodination apart from causing thyroid histopathological injury such as follicular deformation and atrophy. The study indicated that Pb might cause ovarian malfunction by inducing ovary and thyroid microstructural damages, thyroid hormone and estrogen release inhibition and ovarian steroidogenesis disruption.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) and their effects on the ovary

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are found widespread in drinking water, foods, food packaging materials and other consumer products. Several PFAS have been identified as endocrine-disrupting chemicals based on their ability to interfere with normal reproductive function and hormonal signalling. Experimental models and epidemiologic studies suggest that PFAS exposures target the ovary and represent major risks for women's health.

OBJECTIVE AND RATIONALE

This review summarises human population and toxicological studies on the association between PFAS exposure and ovarian function.

SEARCH METHODS

A comprehensive review was performed by searching PubMed. Search terms included an extensive list of PFAS and health terms ranging from general keywords (e.g. ovarian, reproductive, follicle, oocyte) to specific keywords (including menarche, menstrual cycle, menopause, primary ovarian insufficiency/premature ovarian failure, steroid hormones), based on the authors' knowledge of the topic and key terms.

OUTCOMES

Clinical evidence demonstrates the presence of PFAS in follicular fluid and their ability to pass through the blood-follicle barrier. Although some studies found no evidence associating PFAS exposure with disruption in ovarian function, numerous epidemiologic studies, mostly with cross-sectional study designs, have identified associations of higher PFAS exposure with later menarche, irregular menstrual cycles, longer cycle length, earlier age of menopause and reduced levels of oestrogens and androgens. Adverse effects of PFAS on ovarian folliculogenesis and steroidogenesis have been confirmed in experimental models. Based on laboratory research findings, PFAS could diminish ovarian reserve and reduce endogenous hormone synthesis through activating peroxisome proliferator-activated receptors, disrupting gap junction intercellular communication between oocyte and granulosa cells, inducing thyroid hormone deficiency, antagonising ovarian enzyme activities involved in ovarian steroidogenesis or inhibiting kisspeptin signalling in the hypothalamus.

WIDER IMPLICATIONS

The published literature supports associations between PFAS exposure and adverse reproductive outcomes; however, the evidence remains insufficient to infer a causal relationship between PFAS exposure and ovarian disorders. Thus, more research is warranted. PFAS are of significant concern because these chemicals are ubiquitous and persistent in the environment and in humans. Moreover, susceptible groups, such as foetuses and pregnant women, may be exposed to harmful combinations of chemicals that include PFAS. However, the role environmental exposures play in reproductive disorders has received little attention by the medical community. To better understand the potential risk of PFAS on human ovarian function, additional experimental studies using PFAS doses equivalent to the exposure levels found in the general human population and mixtures of compounds are required. Prospective investigations in human populations are also warranted to ensure the temporality of PFAS exposure and health endpoints and to minimise the possibility of reverse causality.

Effects of thyroid hormone on ovarian cell apoptosis in the rat

Follicle development is a complicated process regulated by thyroid hormone (TH). TH dysregulation is associated with reproductive disorders; however, the mechanism underlying these relationships remains unclear. Glucose-related protein 78 (GRP78) is a well-characterised endoplasmic reticulum stress protein related to ovarian cell apoptosis. To clarify whether GRP78 is regulated by TH and the involvement of GRP78 in follicle development, we established rat models of hypothyroidism and hyperthyroidism and investigated the effects of TH dysregulation on levels of GRP78, C/EBP homologous protein (CHOP) and cleaved caspase-3. TH dysregulation decreased levels of GRP78 and increased those of CHOP and cleaved caspase-3 in both rat models. However, treatment with equine chorionic gonadotrophin reversed these effects, as well as granulosa cell apoptosis induced by TH dysregulation. Together, these results provide evidence that TH dysregulation alters the GRP78 expression profile, triggering the apoptotic signalling pathway, and suggest that GRP78 is a novel mediator of TH in follicle development.

Thyroid hormones T3 and T4 regulate human luteinized granulosa cells, counteracting apoptosis and promoting cell survival

PURPOSE

Fine and balanced regulation of cell proliferation and apoptosis are key to achieve ovarian follicle development from the primordial to the preovulatory stage and therefore assure female reproductive function. While gonadotropins are the major and most recognized regulators of follicle cell growth and function, other factors, both systemic and local, play equally important roles. This work is aimed at evaluating the effects of thyroid hormones (THs) on human granulosa luteinized (hGL) viability.

METHODS

Human GL cells derived from assisted reproduction treatments were exposed to T3 or T4. Cell viability was evaluated by MTT assay. Apoptosis was evaluated by the TUNEL assay and active caspase-3 staining. StAR, CYP19A1,Caspase-3, P53 and BAX mRNA were evaluated by real-time PCR. LC3-I/-II, AKT and pAKT were evaluated by western blot.

RESULTS

T3 and T4 promoted cell viability in a dose-dependent modality and modulate StAR and CYP19A1 expression. T3 and to a lesser extent T4 mitigated cell death induced by serum starvation by inhibition of caspase-3 activity and expression of P53 and BAX; and attenuate cell death experimentally induced by C2-ceramide. Cell death derived from starvation appeared to be involved in autophagic processes, as the levels of autophagic markers (LC3-II/LC3-I ratio) decreased when starved cells were exposed to T3 and T4. This effect was associated with an increase in pAkt levels.

CONCLUSION

From the present study, THs emerge as potent anti-apoptotic agents in hGL cells. This effect is achieved by inhibiting the apoptosis signalling pathway of BAX and caspase-3, while maintaining active the PI3K/AKT pathway.

Thyroid Hormones and Functional Ovarian Reserve: Systemic vs. Peripheral Dysfunctions

Thyroid hormones (THs) exert pleiotropic effects in different mammalian organs, including gonads. Genetic and non-genetic factors, such as ageing and environmental stressors (e.g., low-iodine intake, exposure to endocrine disruptors, etc.), can alter T4/T3 synthesis by the thyroid. In any case, peripheral T3, controlled by tissue-specific enzymes (deiodinases), receptors and transporters, ensures organ homeostasis. Conflicting reports suggest that both hypothyroidism and hyperthyroidism, assessed by mean of circulating T4, T3 and Thyroid-Stimulating Hormone (TSH), could affect the functionality of the ovarian reserve determining infertility. The relationship between ovarian T3 level and functional ovarian reserve (FOR) is poorly understood despite that the modifications of local T3 metabolism and signalling have been associated with dysfunctions of several organs. Here, we will summarize the current knowledge on the role of TH signalling and its crosstalk with other pathways in controlling the physiological and premature ovarian ageing and, finally, in preserving FOR. We will consider separately the reports describing the effects of circulating and local THs on the ovarian health to elucidate their role in ovarian dysfunctions.

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

The subtle balance of insulin and thyroxine on survival and development of in vitro cultured caprine preantral follicles enclosed in ovarian tissue

Numerous studies have reported the importance of thyroid hormones on the development of later preantral and antral follicles, but their interactions with other hormones and effects in regulating early preantral follicle growth remain unclear. Here we investigated the in vitro effects of thyroxine combined with insulin on caprine preantral follicle survival and development. Sliced ovarian tissues were cultured for 1 or 7 days using 10 ng/mL (low) or 10 μg/mL (high) insulin in the presence of thyroxine at 0, 0.5, 1 or 2 μg/mL. Post-culture, we evaluated the follicular survival and development, assessed the expression of apoptotic-related genes (Bcl2/Bax) and receptors of insulin and thyroid hormones, and quantified the estradiol and reactive oxygen species (ROS) production levels. Follicular survival in low-insulin culture conditions was enhanced by the presence of 0.5 μg/mL thyroxine (P < 0.05) as compared to the thyroxine-free medium but remained similar to non-cultured control in the presence of 2 μg/mL (P > 0.05). Significantly higher ROS production was measured from Day 1 to Day 7 in low-insulin culture media containing 0.5 or 2 μg/mL thyroxine (P < 0.05). When compared to high insulin level, the presence of thyroxine in low insulin culture conditions yielded higher stromal cell density (P < 0.05), increased estradiol production on Day 1, and higher Bcl2/Bax ratio on Day 7. Cultures with high levels of both insulin and thyroxine led to follicles and oocytes with larger diameters (P < 0.05). The RNA transcript levels of insulin and thyroid receptors were reduced in the presence of high insulin cultures when compared to controls (non-cultured). In conclusion, the combination of low concentrations of insulin and thyroxine better maintained follicle survival, while high levels ensured better follicular development.

Exposure of adult mice to perfluorobutanesulfonate impacts ovarian functions through hypothyroxinemia leading to down-regulation of Akt-mTOR signaling

Perfluorobutanesulfonate (PFBS), a short-chain perfluoroalkyl substance, is used in many industrial products. Preliminary evidence suggests that exposure to PFBS may increase the risk of infertility. The aim of this study was to investigate the influence of PFBS on ovarian function. Herein, we show that exposure of adult female mice to PFBS (200 mg/kg/day) (PFBS-mice) caused a decrease in the levels of serum total triiodothyronine and thyroxine, which depended on the activation of peroxisome proliferator-activated receptor α (PPARα). The numbers of secondary, early antral and antral follicles were reduced in PFBS-mice with an increase in the atretic follicles, and these changes were recovered by the replacement of L-thyroxinein or the treatment with PPARα antagonist GW6471. PFBS-induced hypothyroxinemia led to a decrease in the levels of Akt, mTOR and p70S6K phosphorylation in ovarian granular cells and cumulus cells, which suppressed the proliferation of these cells and enhanced autophagic death of granular cells and cumulus cells. The levels of serum estradiol and progesterone were reduced in PFBS-mice with a low expression of the steroidogenic genes Star and P450scc in ovarian tissues, which were sensitive to the replacement of L-thyroxinein or the blockade of PPARα. The results indicate that exposure to PFBS (≥200 mg/kg/day) through reducing thyroid hormones causes down-regulation of Akt-mTOR signaling in granular cells and cumulus cells, leading to the deficits in the development of follicles and the biosynthesis of ovarian hormones.

Effect of melatonin on gonad and thyroid development of offspring of hypothyroid pregnant rats

We investigated the effects of melatonin on rats with induced hypothyroidism during gestation as well as its effect on the development of the gonads of their offspring. Fifteen pregnant rats were divided into three groups: GC, rats without induced hypothyroidism; GH, rats with induced hypothyroidism; GHM, rats with induced hypothyroidism plus melatonin. Hypothyroidism was induced by oral administration of 6-propyl-2-thiouracil and melatonin was applied subcutaneously. Treatments were performed during gestation and lactation. For the matrices, we evaluated the number of pups, body weight gain, ovarian weight, thyroid weight, organosomatic index, thyroid stimulating hormone (TSH) dose and thyroid morphometry. For the pups, weight gain, TSH, weight, morphometry of the gonads and organosomatic index were analyzed, as well as the cell proliferation index. TSH was elevated only in the matrices of GH animals. Melatonin prevented reduction of ovarian and thyroid weight, number of pups, follicular diameter and thyroid epithelial proportion of the matrices with hypothyroidism. The offspring of rats of the GH group exhibited less body weight gain, gonad and thyroid weight, and gonad cell proliferation index compared to the offspring born of rats of the GC and GHM groups. Melatonin prevented the effects of maternal hypothyroidism on the offspring of rats.

Subclinical Hypothyroidism Is Associated with Lower Ovarian Reserve in Women Aged 35 Years or Older

Background: Overt thyroid diseases have been identified as risk factors for female infertility. However, it remains largely unclear whether subclinical hypothyroidism (SCH), a very common thyroid disorder, is associated with female infertility. This study aimed to investigate the potential association between SCH and the ovarian reserve in women seeking infertility treatment. Methods: This retrospective study included 2568 women with normal thyroid function (n = 2279) or SCH (n = 289) who visited our clinic for infertility treatment. Ovarian reserve markers, including follicle-stimulating hormone (FSH) concentrations on days 2-4, the antral follicle count (AFC), and anti-Müllerian hormone (AMH) concentration, were compared between euthyroid women and those with SCH. Multiple linear and Poisson regression analyses were used to estimate the associations of SCH with ovarian reserve markers. These analyses were repeated separately in women aged <35 (n = 1349) and ≥35 years (n = 1219). Results: In the total study population, women with SCH had significantly lower AMH concentrations (median: 2.05 vs. 2.51 ng/mL, p = 0.015) and AFCs (median: 10.0 vs. 11.0, p = 0.013), compared with euthyroid women. In linear and Poisson regression analyses, SCH was significantly associated with a higher basal FSH concentration (mean difference = 1.13 mIU/mL [95% confidence interval (CI) 0.97 to 1.29 mIU/mL], p < 0.001), lower AMH concentration (mean difference = -0.27 ng/mL [CI -0.43 to -0.12 ng/mL], p = 0.001), and lower AFC (mean difference = -0.7 [CI -1.3 to -0.2], p = 0.005). In women aged ≥35 years, SCH was significantly associated with FSH (mean difference = 1.74 mIU/mL, p < 0.001) and AMH concentrations (mean difference = -0.40 mg/mL, p < 0.001) and AFC (mean difference = -0.8, p < 0.001). In women <35 years old, SCH was significantly associated with a higher FSH concentration (mean difference = 0.30 mIU/mL, p < 0.001), but not with AMH or AFC concentrations (p = 0.84 and 0.06, respectively). Thyroperoxidase antibody (TPOAb) positivity was not associated with measures of ovarian reserve. Conclusions: The data suggest that SCH is associated with decreased ovarian reserve during later reproductive age. TPOAb positivity was not associated with ovarian reserve. Future research is necessary to investigate the underlying molecular mechanisms regulating the diminished ovarian reserve in women with SCH and to evaluate whether levothyroxine supplementation may improve the ovarian function of women with SCH.

Serum and follicular fluid thyroid hormone levels and assisted reproductive technology outcomes

OBJECTIVE

The objective ofthis study was to assess the association between thyroid hormone (TH) levels in follicular fluid (FF) and serum and to determine whether THs impact assisted reproductive technology (ART) outcomes.

METHODS

This study enrolled 299 women undergoing ART. Blood samples were drawn on the day of human chorionic gonadotrophin (HCG) administrationand analysed for thyroid-stimulating hormone (TSH), thyroxine(T4), triiodothyronine(T3),free T4 (fT4),free T3(fT3), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) levels. FF was obtained on the oocyte pick up (OPU) day and analysed forTSH, T4, T3, fT4, fT3, TPOAb, TgAb and estradiol levels.

RESULTS

(1) There were significant positive correlations between serum and FF TH and thyroid autoantibody levels. Statistically significant differences were discovered in serum and FF levels of TSH (p ≤ 0.001), T4 (p ≤ 0.001), T3 (p ≤ 0.001), TPOAbs (p ≤ 0.001) and TGAbs (p = 0.021). (2) Serum T4 levels [121.9(104.8,140.8) vs 114.1(98.6,130.6) nmol/l, p = 0.026], serum fT4 levels[(19.0(17.7,21.8) vs 18.6(17.0,20.1) pmol/l, p = 0.026], serum T4/T3 ratios [62.5 (55.7, 66.2) vs 59.4 (53.4, 64.9), p = 0.029], FF fT4 levels [19.0(17.5,21.3) vs 18.1(16.8,19.9) pmol/l, p = 0.009] and FF T4/T3 ratios [52.6 (46.4, 57.3) vs 50.0 (43.7, 53.1), p = 0.004] were significantly higher in the successful pregnancy group than the implantation failure group. (3) Spearman's rank correlation analysis revealed positive associations of both the FF T4/T3 ratio and serum TSH levels with the numbers of retrieved oocytes (total or MII) and embryos (fertilized, cleavage, and good quality).

CONCLUSIONS

TH levels in FF are strongly correlated with those in serum on the HCG day, and THs on the HCG day may affect ART outcomes.

Differential expression and immunoreactivity of thyroid hormone transporters MCT8 and OATP1C1 in rat ovary

Thyroid hormones (THs) regulate several physiological processes in female mammals, many of which are related to reproduction such as steroidogenesis in the ovary, oocyte and granulosa cells maturation, follicular development and differentiation, and ovulation. THs actions require the presence of THs transporters to facilitate their cellular uptake and efflux. MCT8 and OATP1C1 are the principal THs transporters. The aim of the present study was to determine the gene expression and cellular localization of MCT8 and OATP1C1 in the rat ovary during the diestrus-II cycle phase. Ovaries of virgin adult rats were histologically processed. Reverse Transcription-PCR and immunohistochemistry analyses for MCT8 and OATP1C1 were done. MCT8 gene expression level was significantly higher (P ≤ 0.01) than that of OATP1C1 in the rat ovary. MCT8 and OATP1C1 were found in all types of ovarian cells but with different immunoreactivity. MCT8 showed stronger immunoreactivity in tertiary and Graafian follicles, corpus luteum and blood vessels, whereas OATP1C1's immunoreactivity was stronger in stroma cells, tunica albuginea, and blood vessels. Our results provide evidence that THs and their transporters are both necessary for ovarian function and that any alteration in these transporters could interfere with reproductive processes such as ovulation and steroidogenesis, compromising fertility.

Roles of different n-3/n-6 PUFA ratios in ovarian cell development and steroidogenesis in PCOS rats

Polycystic ovary syndrome (PCOS) is a complex and common endocrine disorder characterized by hyperandrogenism, which is accompanied by follicle growth arrest at the small antral stage, minimal granulosa cell proliferation, and chronic anovulation. Polyunsaturated fatty acids (PUFAs) are necessary for the body's metabolism, growth and development. Although PUFAs play an important role in the regulation of female reproduction, their role in ovarian development in PCOS is still unclear. The present study was conducted to investigate the effects of different ratios of n-3/n-6 PUFAs (omega-3/omega-6) on ovary development in PCOS rats. Serum levels of reproductive hormones and enzymes related to steroidogenesis were assessed. The results indicated that PUFAs (n-3/n-6: 1/15) significantly increased ovarian weight and improved the ovarian structure although they had no significant effect on body weight in PCOS rats. Meanwhile, apoptosis was attenuated accompanied by increased cell proliferation by PUFAs (n-3/n-6: 1/15). Moreover, serum levels of hormones (FSH and E₂) were also significantly increased by PUFAs (n-3/n-6: 1/15) accompanied by decreased T levels. To investigate whether PUFAs regulate the expression of enzymes related to hormone synthesis, western blotting was used to determine the protein levels of CYP51, CYP19, StAR and 3β-HSD. The results showed that PUFAs significantly increased the protein levels of all of these enzymes. These results indicate that PUFAs enhance the reproductive performance of PCOS by increasing the expression of steroidogenesis enzymes, which are related to hormone secretion and ovarian functions. These findings provide evidence that a balanced n-3/n-6 PUFA ratio is beneficial for PCOS reproduction.

Thyroid hormones and female reproduction

Thyroid hormones are vital for the proper functioning of the female reproductive system, since they modulate the metabolism and development of ovarian, uterine, and placental tissues. Therefore, hypo- and hyperthyroidism may result in subfertility or infertility in both women and animals. Other well-documented sequelae of maternal thyroid dysfunctions include menstrual/estral irregularity, anovulation, abortion, preterm delivery, preeclampsia, intrauterine growth restriction, postpartum thyroiditis, and mental retardation in children. Several studies have been carried out involving prospective and retrospective studies of women with thyroid dysfunction, as well as in vivo and in vitro assays of hypo- and hyperthyroidism using experimental animal models and/or ovarian, uterine, and placental cell culture. These studies have sought to elucidate the mechanisms by which thyroid hormones influence reproduction to better understand the physiology of the reproductive system and to provide better therapeutic tools for reproductive dysfunctions that originate from thyroid dysfunctions. Therefore, this review aims to summarize and update the available information related to the role of thyroid hormones in the morphophysiology of the ovary, uterus, and placenta in women and animals and the effects of hypo- and hyperthyroidism on the female reproductive system.

Regulation by 3,5,3'-tri-iodothyronine and FSH of cytochrome P450 family 19 (CYP19) expression in mouse granulosa cells

Cytochrome P450 family 19 (CYP19) plays an important role in follicular development, which is regulated by FSH. Although 3,5,3'-tri-iodothyronine (T3) combines with FSH to induce preantral follicle growth and granulosa cell development, the mechanism involved remains unclear. The aim of the present study was to determine the cellular and molecular mechanisms by which thyroid hormone (TH) and FSH regulate CYP19 expression and sterol biosynthesis during preantral follicle growth. Mice were injected subcutaneously (s.c.) with eCG (Equine chorionic gonadotropin). The results showed that eCG increased CYP19 expression in ovarian cells. CYP19 expression in granulosa cells was increased after FSH treatment, and this response was enhanced by T3. Knockdown of CYP19 significantly decreased granulosa cell viability and hormone-stimulated proliferation. In addition, CYP19 knockdown also blocked T3- and FSH-induced oestradiol (E2) synthesis in granulosa cells. Furthermore, activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway was required for T3 and FSH regulation of CYP19 expression. In conclusion, the results of the present study indicate that CYP19 is important for T3- and FSH-induced granulosa cell development in the early stages. CYP19 could be a downstream effector of the PI3K/Akt pathway in regulating TH and FSH during follicular development and sterol biosynthesis. The findings suggest that CYP19 is a novel mediator of T3- and FSH-induced follicular development.

Effect of hypothyroidism on CYP51 and FSHR expression in rat ovary

Although thyroid hormone (TH) plays important roles in regulating ovarian development, the mechanism are still unclear. Cytochrome P450 lanosterol 14α-demethylase (CYP51) is a key enzyme in sterols and steroids biosynthesis that involved in folliculogenesis and oocyte maturation, which is regulated by follicle stimulating hormone (FSH). However, the effect of TH on CYP51 expression in ovarian cells is unclear. The objective of this study was to determine the effects of TH on CYP51 in rat ovary. Hypothyroidism rats were induced by 6-propyl-2-thiouracil (PTU), genes expressions in ovary were analyzed by Western blot or qRT-PCR. The data showed that CYP51 was significantly decreased in hypothyroidism, which was accompanied by the down-regulation of mRNA level. Meanwhile, similar tendency was also showed in FSHR expression in hypothyroidism. To evaluate the effect of the gonadotropin on CYP51 and FSHR expression in ovarian cells in vivo, hypo rats were injected subcutaneously with equine chorionic gonadotropin (eCG) respectively. The results showed that eCG reversed CYP51 and FSHR expression in hypo group. Moreover, FSH-induced CYP51 expression was meditated by FSHR. In addition, serum concentration of FSH and E₂ were also decreased in hypothyroidism, and E₂ was up-regulated by eCG treatment. These results indicate that hypothyroidism changes CYP51 and FSHR expression in ovary, which are regulated by gonadotropin. Moreover, genes changes in ovary are at least partially attributed to steroids biosynthesis.

Bisphenol A attenuates thyroxine-induced apoptosis in ovarian granulosa cells of pigs

Bisphenol A (BPA) is a chemical of high production volume that is used widely in many industries and is known as a xenooestrogen and anti-thyroid hormone endocrine disrupter. There is little information regarding the effects of BPA in the presence of thyroid hormone on porcine granulosa cell development. Thus, the primary granulosa cells were treated with thyroxine (T4, 10 nM), BPA (10 µM) or T4 plus BPA; we subsequently evaluated the effects of T4 or BPA on 17β-estradiol synthesis, cellular proliferation and apoptosis. Our data showed that BPA significantly increased the accumulation of 17β-estradiol and promoted granulosa cell proliferation, whereas T4 significantly decreased 17β-estradiol and had no effect on cellular proliferation. In addition, it was noteworthy that T4 treatment induced apoptosis in porcine granulosa cells and BPA co-incubation attenuated T4-induced apoptosis as shown from flow cytometric assay analysis. We hypothesized that BPA attenuates T4-induced apoptosis by regulating 17β-estradiol accumulation and oestrogen receptor-mediated signalling pathways. In conclusion, our results demonstrated that T4 affected 17β-estradiol accumulation and induced cellular apoptosis, but did not affect granulosa cell proliferation. Exposure to BPA increased 17β-estradiol accumulation, promoted granulosa cell proliferation and attenuated T4-induced apoptosis in porcine granulosa cells in vitro.

Thyroid hormones act as mitogenic and pro survival factors in rat ovarian follicles

PURPOSE

Thyroid disorders are clinically associated with impaired fertility in women, and these abnormalities can be improved by restoring the euthyroid state. The exact mechanisms of thyroid effect on female fertility are not well known; however, it is conceivable that thyroid hormones (THs) might act on ovarian physiology via receptors in granulosa cells. This work is aimed at evaluating the effects of THs on non-tumoral granulosa cells and follicles.

METHODS

Freshly isolated rat ovarian follicles and granulosa cells were exposed to T3 or T4 (THs). Cell growth and viability were evaluated by cell counting and the MTT assay, respectively, follicle growth was evaluated by volume measurements. Apoptosis was evaluated by the TUNEL assay and active Caspase 3 staining. rGROV cells were exposed to T3, and apoptosis was induced by serum deprivation. Bcl2, Bcl-2-associated X protein (BAX), Akt and pAkt expression were evaluated by western blot.

RESULTS

T3 induced a 40% increase in follicle volume (after 7 days). This increase was presumably due to the observed decrease (33%) in the apoptotic rate of the granulosa cell population. Both T3 and T4 caused a dose-dependent increase in rat granulosa cell number and viability. In addition, THs decreased the cell apoptotic rate in a dose-dependent manner. In both conditions, T3 appeared to be more efficient. In rGROV cells, 100 nM T3 induced cell growth and, in the absence of growth factors, reduced cell apoptosis by 40%, downregulating Caspase 3 and BAX. This effect was associated with an increase in pAkt levels. The involvement of the PI3 K pathway was confirmed by the ability of the PI3 K specific inhibitor (LY-294,002) to abolish T3 pro-survival action.

CONCLUSIONS

THs influence cell survival of ovarian granulosa cells. This effect likely contributes to the TH-induced follicle volume increase.

Oxidative stress modulates the expression of apoptosis-associated microRNAs in bovine granulosa cells in vitro

Despite its essential role in ovulation, oxidative stress (OS) has been found to be cytotoxic to cells, while microRNAs (miRNAs) are known as a major regulator of genes involved in cellular defense against cytotoxicity. However, a functional link between OS and miRNA expression changes in granulosa cells (GCs) remains to be investigated. Here, we investigate the OS modulation of apoptosis-associated miRNAs and their biological relevance in bovine GCs. Following the evaluation of cell viability, accumulation of reactive oxygen species (ROS), cytotoxicity and mitochondrial activity, we used a ready-to-use miRNA PCR array to identify differentially regulated miRNAs. The results showed that exposure to 150 μM H₂O₂ for 4 h creates remarkable signs of OS in GCs characterized by more than 50% loss of cell viability, higher nuclear factor erythroid 2-related factor 2 (NRF2) nuclear translocation, significantly (p < 0.05) higher abundance of antioxidant genes, significantly (p < 0.001) higher accumulation of ROS, lower mitochondrial activity and a higher (p < 0.001) number of apoptotic nuclei compared to that of the control group. miRNA expression analysis revealed that a total of 69 miRNAs were differentially regulated in which 47 and 22 miRNAs were up- and downregulated, respectively, in stressed GCs. By applying the 2-fold and p < 0.05 criteria, we found 16 miRNAs were upregulated and 10 miRNAs were downregulated. Target prediction revealed that up- and downregulated miRNAs potentially targeted a total of 6210 and 3575 genes, respectively. Pathway analysis showed that upregulated miRNAs are targeting the genes involved mostly in cell survival, intracellular communication and homeostasis, cellular migration and growth control and disease pathways. Our results showed that OS modulates the expression of apoptosis-associated miRNAs that might have effects on cellular or molecular damages.

Effects of omega-3 polyunsaturated fatty acids on steroidogenesis and cellular development in PCOS rats

Polycystic ovary syndrome (PCOS) is a common endocrine disorder, which is characterized by hyperandrogenism.

Association of Thyroid Function and Autoimmunity with Ovarian Reserve in Women Seeking Infertility Care

BACKGROUND

While overt thyroid disease is a well known risk factor for infertility, the potential consequences of mild thyroid dysfunction or thyroid autoimmunity remain unknown. Experimental studies suggest a considerable role for thyroid hormone in the physiological mechanisms of ovarian reserve, but translation of such findings to human studies remains rare. A potential role for thyroid function in female reproduction could be especially relevant when the cause of infertility remains unknown, such as in women with diminished ovarian reserve (DOR) or unexplained infertility. The aims of this study were to investigate the association of thyroid function and autoimmunity with markers of ovarian reserve day 3 follicle-stimulating hormone (FSH) concentrations and antral follicle count (AFC), and to investigate whether thyroid function or autoimmunity may have different effects in women with DOR or unexplained infertility.

METHODS

Thyrotropin, free thyroxine, thyroxine, free triiodothyronine (fT3), triiodothyronine, thyroid peroxidase antibodies (TPOAbs), and thyroglobulin antibodies (TgAbs), as well as AFC and the day 3 FSH concentration, were measured among women seeking fertility treatment at the Massachusetts General Hospital Fertility Center. Multiple linear or mixed regression models were used to study the association of thyroid function or autoimmunity with AFC or day 3 FSH.

RESULTS

In the total study population (436 women, 530 AFC measurements), there was no association of thyroid function or TPOAb positivity with AFC. However, TgAb positivity was associated with a higher AFC (mean difference = 3.4 [95% confidence interval (CI) 1.8-5.1], p < 0.001). In women with DOR or unexplained infertility, lower fT3 and TPOAb positivity were associated with a lower AFC (fT3: continuous nonlinear association, p = 0.009; TPOAb positivity: -2.3 follicles [confidence interval -3.8 to -0.5], p = 0.01), while TgAb positivity was not associated with AFC. Neither thyroid function nor thyroid antibody positivity was associated with the day 3 FSH concentration.

CONCLUSIONS

This study found that lower fT3 and TPOAb positivity are associated with a lower AFC in women with DOR or unexplained infertility. Future studies are required to replicate these findings and further elucidate the role of TgAbs and underlying mechanisms through which thyroid function and autoimmunity is associated with ovarian reserve.

Applications for non-invasive thyroid hormone measurements in mammalian ecology, growth, and maintenance

Thyroid hormones (THs) play a pivotal role in the regulation of metabolic activity throughout all life stages. Cross-talk with other hormone systems permits THs to coordinate metabolic changes as well as modifications in growth and maintenance in response to changing environmental conditions. The scope of this review is to explain the relevant basics of TH endocrinology, highlight pertinent topics that have been investigated so far, and offer guidance on measuring THs in non-invasively collected matrices. The first part of the review provides an overview of TH biochemistry, which is necessary to understand and interpret the findings of existing studies and to apply non-invasive TH monitoring. The second part focuses on the role of THs in mammalian ecology, and the third part highlights the role of THs in growth and maintenance. The fourth part deals with the advantages and difficulties of measuring THs in non-invasively collected samples. This review concludes with a summary that considers future directions in the study of THs.

Sexual function and depressive symptoms in young women with hypothyroidism receiving levothyroxine/liothyronine combination therapy: a pilot study

Objective Even mild hypothyroidism in pre-menopausal women is accompanied by impaired sexual functioning. The study was aimed at comparing the effect of levothyroxine, administered alone or in combination with liothyronine, on sexual function and depressive symptoms in pre-menopausal women treated because of hypothyroidism. Methods This quasi-randomized, single-blind study included 39 young women receiving levothyroxine treatment who, despite thyrotropin and thyroid hormone levels within normal limits, still experienced clinical symptoms of hypothyroidism. These patients were divided into two groups: group A (n = 20) continued levothyroxine treatment, while group B (n = 19) received levothyroxine/liothyronine combination therapy. At the beginning of the study, and 6 months later, all participants of the study filled in questionnaires evaluating female sexual functioning (Female Sexual Function Index; FSFI) and the presence and severity of depressive symptoms (Beck Depression Inventory-Second Edition; BDI-II). Results The study was completed by 37 women. Baseline sexual functioning and depressive symptoms did not differ between the study groups. Neither the total FSFI score nor the domain scores changed throughout the study in women who continued levothyroxine treatment. Compared to levothyroxine administered alone, levothyroxine/liothyronine combination therapy increased scores for two domains: sexual desire and arousal, tended to increase the total FSFI score, as well as tended to decrease the overall BDI-II score. The effect of the combination therapy on sexual function correlated with a treatment-induced increase in serum levels of free triiodothyronine and testosterone. Conclusions The obtained results suggest that levothyroxine administered together with liothyronine is superior to levothyroxine administered alone in affecting female sexual functioning.

Mitigation of stress from gastric mucosal injuries by mulberry extract may occur via nitric oxide synthase signaling in mice

Acute gastric mucosal injuries are serious clinical problems worldwide and are principally found with different types of stresses in animals. A constant challenge is to find original plant products that can combat stress. In the present study, we examined the effects of big-leaf mulberry extracts on stomach injury, and the activity of nitric oxide synthases (NOS) and total antioxidant activity (TAO) in the gastric mucosae of mice during water immersion and restraint stress (WIRS). Our data showed that WIRS-exposed mice produced several injuries and showed an enhanced iNOS, reduced eNOS activity, and decreased TAO activity in the stomach, whereas pretreatment with big-leaf mulberry extracts increased TAO activitiy. The data from our immunohistochemical study indicated that both iNOS and eNOS were expressed in parietal cells and blood vessels, while nNOS was only weakly expressed in parietal cells. In conclusion, our findings suggested that big-leaf mulberry mitigated WIRS-induced stomach injuries, and NOS signaling may play important roles in the mouse stomach during the recovery process.

Contemporaneous effects of diabetes mellitus and hypothyroidism on spermatogenesis and immunolocalization of Claudin-11 inside the seminiferous tubules of mice

Background

Diabetes and hypothyroidism produce adverse effects on body weight and sexual maturity by inhibiting body growth and metabolism. The occurrence of diabetes is always accompanied with thyroid dysfunction. Thus, it is important to take hypo- or hyper-thyroidism into consideration when exploring the adverse effects caused by diabetes. Previous reports have found hypothyroidism inhibits testicular growth by delaying Sertoli cell differentiation and proliferation. Hence, by establishing a mouse model of diabetes combined with hypothyroidism, we provided evidence that poly glandular autoimmune syndrome affected testicular development and spermatogenesis.

Results

we mimicked polyglandular deficiency syndrome in both immature and prepubertal mice by induction of diabetes and hypothyroidism, which caused decreases in serum concentrations of testosterone and insulin like growth factor 1 (IGF-1). Such reduction of growth factor resulted in inhibition of testicular and epididymal development. Moreover, expressions of Claudin-11 were observed between Sertoli cells and disrupted in the testes of syndrome group mice. We also found reduced sperm count and motility in prepubertal mice.

Conclusions

This mimicry of the diabetes and thyroid dysfunction, will be helpful to better understand the reasons for male infertility in diabetic-cum-hypothyroid patients.

Electronic supplementary material

The online version of this article (10.1186/s12861-018-0174-4) contains supplementary material, which is available to authorized users.

cGMP/PKG-I Pathway-Mediated GLUT1/4 Regulation by NO in Female Rat Granulosa Cells

Nitric oxide (NO) is a multifunctional gaseous molecule that plays important roles in mammalian reproductive functions, including follicular growth and development. Although our previous study showed that NO mediated 3,5,3'-triiodothyronine and follicle-stimulating hormone-induced granulosa cell development via upregulation of glucose transporter protein (GLUT)1 and GLUT4 in granulosa cells, little is known about the precise mechanisms regulating ovarian development via glucose. The objective of the present study was to determine the cellular and molecular mechanism by which NO regulates GLUT expression and glucose uptake in granulosa cells. Our results indicated that NO increased GLUT1/GLUT4 expression and translocation in cells, as well as glucose uptake. These changes were accompanied by upregulation of cyclic guanosine monophosphate (cGMP) level and cGMP-dependent protein kinase (PKG)-I protein content. The results of small interfering RNA (siRNA) analysis showed that knockdown of PKG-I significantly attenuated gene expression, translocation, and glucose uptake. Moreover, the PKG-I inhibitor also blocked the above processes. Furthermore, NO induced cyclic adenosine monophosphate response element binding factor (CREB) phosphorylation, and CREB siRNA attenuated NO-induced GLUT expression, translocation, and glucose uptake in granulosa cells. These findings suggest that NO increases cellular glucose uptake via GLUT upregulation and translocation, which are mediated through the activation of the cGMP/PKG pathway. Meanwhile, the activated CREB is also involved in the regulation. These findings indicate that NO has an important influence on the glucose uptake of granulosa cells.

In Utero and Postnatal Propylthiouracil-Induced Mild Hypothyroidism Impairs Maternal Behavior in Mice

Thyroid hormones (THs) play crucial roles in general and brain development. Even if the hypothyroidism is mild, it may alter brain function, resulting in irreversible behavioral alterations. Although various behavioral analyses have been conducted, the effects of propylthiouracil (PTU) treatment during in utero and postnatal periods on maternal behavior have not yet been studied. The present study examined in mice whether THs insufficiency during development induce behavioral changes. Pregnant C57BL/6j mice were divided into three groups, and each group was administered different dosages of PTU (0, 5, or 50 ppm) in drinking water during in utero and postnatal periods (from gestational day 14 to postnatal day 21). First, locomotor activity and cognitive function were assessed in the offspring at 10 weeks. Next, female offspring were mated with normal mice and they and their offspring were used to assess several aspects of maternal behavior (identifying first pup, returning all pups to nest, time spent nursing, and licking pups). As expected, locomotor and cognitive functions in these mice were disrupted in a PTU dose-dependent manner. On postpartum day 2, dams who had been exposed 50 ppm PTU during in utero and postnatal periods displayed a significantly longer time identifying the first pup and returning all three pups back to the nest, less time nursing, and decreased licking behavior. The decrease in maternal behavior was significantly correlated with a decrease in cognition. These results indicate that insufficiency of THs during in utero and postnatal periods impairs maternal behavior, which may be partly induced by impaired cognitive function.

Thyroid hormones alter estrous cyclicity and antioxidative status in the ovaries of rats

To expand our understanding of the roles of thyroid hormones on female reproduction, we induced hypo- and hyper-T rat models to investigate the roles of thyroid hormones on estrous cyclicity, as well as the antioxidative status in the ovaries of rats. In the current study, our data show that hypothyroidism (hypo-T) and hyperthyroidism (hyper-T) led to significantly reduced body weights and ovarain weights and delayed vaginal opening day. For hyper-T, thyroxine (T4), tri-iodothyronine (T3), progesterone (P4) and follicle-stimulating hormone (FSH) were significantly increased, while estradiol (E2) and luteinizing hormone (LH) were significantly decreased. For hypo-T rats, serum levels of total T4 and T3, E2, P4, FSH and LH were significantly increased, while concentrations of E2 and LH were significantly decreased. For ovary morphology, the numbers of secondary and antral follicles were significantly decreased with more atretic antral follicles and less corpora lutea in both hyper- and hypo-T groups. Both hyper-T and hypo-T treatment significantly decreased the expressions of thyroid hormone receptor α1 in the ovary. Hypo-T significantly reduced nitric oxide (NO), total NO synthase (tNOS), inducible NOS and constitutive NOS activities, but hyper-T increased them. For antioxidative parameters, hypo-T and hyper-T treatment significantly increased malondialdehyde (MDA) contents. The activities of both glutathione peroxidase (GSH-Px) and catalase (CAT) significantly decreased in the hypo-T group but increased in the hyper-T group. Total superoxide dismutase (T-SOD) activity was significantly increased in the hyper-T group. In summary, thyroid hormones alter estrous cyclicity and antioxidative status in the ovary of the rat may act through the NOS signaling pathway.

Role of CYP51 in the Regulation of T3 and FSH-Induced Steroidogenesis in Female Mice

Cytochrome P450 lanosterol 14α-demethylase (CYP51) is a key enzyme in sterol and steroid biosynthesis that is involved in folliculogenesis and oocyte maturation, which is regulated by follicle-stimulating hormone (FSH), as a key reproductive hormone during follicular development. Thyroid hormone (TH) is also important for normal reproductive function. Although 3,5,3'-triiodothyronine (T3) enhances FSH-induced preantral follicle growth, whether and how TH combines with FSH to regulate CYP51 expression during the preantral to early antral transition stage is unclear. The objective of this study was to determine the cellular and molecular mechanisms by which T3 and FSH regulate CYP51 expression and steroid biosynthesis during preantral follicle growth. Our results indicated that CYP51 expression was upregulated in granulosa cells by FSH, and this response was enhanced by T3. Moreover, knockdown CYP51 decreased cell viability. Meanwhile, gene knockdown also blocked T3 and FSH-induced estradiol (E2) and progesterone (P4) synthesis. These changes were accompanied by upregulation of phospho-GATA-4 content. Results of small interfering RNA analysis showed that knockdown of GATA-4 significantly diminished CYP51 gene expression as well as E2/P4 levels. Furthermore, thyroid hormone receptor β was necessary to the activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), which was required for the regulation of CYP51 expression; activated GATA-4 was also involved these processes. Our data demonstrate that T3 and FSH cotreatment potentiates cellular development and steroid biosynthesis via CYP51 upregulation, which is mediated through the activation of the PI3K/Akt pathway. Meanwhile, activated GATA-4 is also involved in this regulatory system. These findings suggest that CYP51 is a mediator of T3 and FSH-induced follicular development.

Effects of concomitant diabetes mellitus and hyperthyroidism on testicular and epididymal histoarchitecture and steroidogenesis in male animals

This study evaluated the effects of comorbid disorders of diabetes and hyperthyroidism in the adult male mice. In total, 32 ICR strain mice were equally distributed into four groups: control (C), diabetic (D), diabetic-plus-hyperthyroid (DH), and hyperthyroid (H). Mice allocated for diabetes received a single intraperitoneal injection of streptozotocin (STZ) at 200 mg/kg body weight. At the onset of diabetes, one group of mice was concomitantly injected levothyroxine (LT4; 0.3 mg/kg body weight) and the other set of animals received the same treatment independently on a daily basis. The body weight, as well as the testicular and epididymal weights, was reduced markedly in D and DH mice. Higher trends of blood glucose levels were seen in the DH group, in comparison to euthyroid diabetic mice. Thyroid hormones could exert a transient effect on blood glucose homeostasis by altering the serum blood glucose level in diabetic patients. Histomorphometric analysis showed increased luminal sizes of seminiferous tubules, along with decreased epithelial height and atrophic changes in germinal stem cells in the testis of DH and H mice. Caput epididymis of DH mice showed extensive compaction of principal cells, loss of stereocilia, lipid vacuolization, and inflammatory infiltrations; however, damaged tubular integrity, packed clear cells, exfoliated cells, and round spermatids were profoundly noticed in the cauda epididymis. Hyperthyroidism elevated the serum testosterone levels in H and DH mice and produced critical damages to the histoarchitecture of the epididymis. Collectively, this experiment endeavored to mimic the polyglandular autoimmune syndrome, which will be helpful to better understand the reasons for male infertility in diabetic-cum-hyperthyroid patients.

Nitric Oxide-Mediated Regulation of GLUT by T3 and Follicle-Stimulating Hormone in Rat Granulosa Cells

Thyroid hormones are important for normal reproductive function. Although 3,5,3'-triiodothyronine (T3) enhances follicle-stimulating hormone (FSH)-induced preantral follicle growth and granulosa cells development in vitro, little is known about the molecular mechanisms regulating ovarian development via glucose. In this study, we investigated whether and how T3 combines with FSH to regulate glucose transporter protein (GLUT) expression and glucose uptake in granulosa cells. In this study, we present evidence that T3 and FSH cotreatment significantly increased GLUT-1/GLUT-4 expression, and translocation in cells, as well as glucose uptake. These changes were accompanied by upregulation of nitric oxide (NO) synthase (NOS)3 expression, total NOS and NOS3 activity, and NO content in granulosa cells. Furthermore, we found that activation of the mammalian target of rapamycin (mTOR) and phosphoinositide 3-kinase (PI3K)/Akt pathway is required for the regulation of GLUT expression, translocation, and glucose uptake by hormones. We also found that l-arginine upregulated GLUT-1/GLUT-4 expression and translocation, which were related to increased glucose uptake; however, these responses were significantly blocked by N(G)-nitro-l-arginine methylester. In addition, inhibiting NO production attenuated T3- and FSH-induced GLUT expression, translocation, and glucose uptake in granulosa cells. Our data demonstrate that T3 and FSH cotreatment potentiates cellular glucose uptake via GLUT upregulation and translocation, which are mediated through the activation of the mTOR/PI3K/Akt pathway. Meanwhile, NOS3/NO are also involved in this regulatory system. These findings suggest that GLUT is a mediator of T3- and FSH-induced follicular development.

Distribution of thyroid hormone and thyrotropin receptors in reproductive tissues of adult female rabbits

PURPOSE

Thyroid dysfunctions are related to anovulation, miscarriages, and infertility in women and laboratory animals. Mechanisms associated with these effects are unknown, although indirect or direct actions of thyroid hormones and thyrotropin could be assumed. The present study aimed to identify the distribution of thyroid hormones (TRs) and thyrotropin (TSHR) receptors in reproductive organs of female rabbits.

MATERIAL AND METHODS

Ovary of virgin and pregnant rabbits, as well as the oviduct, uterus, and vagina of virgin rabbits were excised, histologically processed, and cut. Slices from these organs were used for immunohistochemical studies for TRα1-2, TRß1, and TSHR.

RESULTS

The presence of TRs and TSHR was found in the primordial, primary, secondary, tertiary, and Graafian follicles of virgin rabbits, as well as in the corpora lutea, corpora albicans, and wall of hemorrhagic cysts of pregnant rabbits. Oviductal regions (fimbria-infundibulum, ampulla, isthmus, and utero-tubal junction), uterus (endometrium and myometrium), and vagina (abdominal, pelvic, and perineal portions) of virgin rabbits showed anti-TRs and anti-TSHR immunoreactivity. Additionally, the distal urethra, paravaginal ganglia, levator ani and iliococcygeus muscles, dorsal nerve and body of the clitoris, perigenital skin, and prostate had TRs and TSHR.

CONCLUSIONS

The wide presence of TRs and TSHR in female reproductive organs suggests varied effects of thyroid hormones and thyrotropin in reproduction.

Exposure of Pregnant Mice to Perfluorobutanesulfonate Causes Hypothyroxinemia and Developmental Abnormalities in Female Offspring

Perfluorobutanesulfonate (PFBS) is widely used in many industrial products. We evaluated the influence of prenatal PFBS exposure on perinatal growth and development, pubertal onset, and reproductive and thyroid endocrine system in female mice. Here, we show that when PFBS (200 and 500 mg/kg/day) was orally administered to pregnant mice (PFBS-dams) on days 1-20 of gestation; their female offspring (PFBS-offspring) exhibited decreased perinatal body weight and delayed eye opening compared with control offspring. Vaginal opening and first estrus were also significantly delayed in PFBS-offspring, and diestrus was prolonged. Ovarian and uterine size, as well as follicle and corpus luteum numbers, were reduced in adult PFBS-offspring. Furthermore, pubertal and adult PFBS-offspring exhibited decreases in serum estrogen (E2) and progesterone (P4) levels with the elevation of luteinizing hormone levels. Notably, decreases in serum total thyroxine (T4) and 3,3', 5-triiodothyronine (T3) levels were observed in fetal, pubertal, and adult PFBS-offspring in conjunction with slight increases in thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone levels. In addition, PFBS-dams exhibited significant decreases in total T4 and T3 levels and free T4 levels and increases in TSH levels, but no changes in E2 and P4 levels. These results indicate that prenatal PFBS exposure (≥200 mg/kg/day) causes permanent hypothyroxinemia accompanied by deficits in perinatal growth, pubertal onset, and reproductive organ development in female mice.

Consequences of hyperthyroidism in male and female fertility: pathophysiology and current management

Thyroid hormone acts on the oocytes, sperm and embryo during fertilization, implantation and placentation. Both hypothyroidism and hyperthyroidism may influence fertility. However, evidence of the association of hyperthyroidism with infertility is scarce and sometimes conflicting. Thyroid hormone influences human reproduction via a variety of mechanisms at both the central and the peripheral level. Infertility may occur in hyperthyroid men and women, but it is usually reversible upon restoration of euthyroidism. This review aims to summarize the available data on the association of hyperthyroidism and infertility in both men and women and to provide practical suggestions for the management of these patients.

Dietary-Induced Chronic Hypothyroidism Negatively Affects Rat Follicular Development and Ovulation Rate and Is Associated with Oxidative Stress

The long-term effects of chronic hypothyroidism on ovarian follicular development in adulthood are not well known. Using a rat model of chronic diet-induced hypothyroidism initiated in the fetal period, we investigated the effects of prolonged reduced plasma thyroid hormone concentrations on the ovarian follicular reserve and ovulation rate in prepubertal (12-day-old) and adult (64-day-old and 120-day-old) rats. Besides, antioxidant gene expression, mitochondrial density and the occurrence of oxidative stress were analyzed. Our results show that continuous hypothyroidism results in lower preantral and antral follicle numbers in adulthood, accompanied by a higher percentage of atretic follicles, when compared to euthyroid age-matched controls. Not surprisingly, ovulation rate was lower in the hypothyroid rats. At the age of 120 days, the mRNA and protein content of superoxide dismutase 1 (SOD1) were significantly increased while catalase (CAT) mRNA and protein content was significantly decreased, suggesting a disturbed antioxidant defense capacity of ovarian cells in the hypothyroid animals. This was supported by a significant reduction in the expression of peroxiredoxin 3 ( ITALIC! Prdx3), thioredoxin reductase 1 ( ITALIC! Txnrd1), and uncoupling protein 2 ( ITALIC! Ucp2) and a downward trend in glutathione peroxidase 3 ( ITALIC! Gpx3) and glutathione S-transferase mu 2 ( ITALIC! Gstm2) expression. These changes in gene expression were likely responsible for the increased immunostaining of the oxidative stress marker 4-hydroxynonenal. Together these results suggest that chronic hypothyroidism initiated in the fetal/neonatal period results in a decreased ovulation rate associated with a disturbance of the antioxidant defense system in the ovary.

Effects of thyroid hormones on the antioxidative status in the uterus of young adult rats

Thyroid hormones and oxidative stress play significant roles in the normal functioning of the female reproductive system. Nitric oxide (NO), a free radical synthesized by nitric oxide synthases (NOS), participates in the regulation of thyroid function and is also a good biomarker for assessment of the oxidative stress status. Therefore, the purpose of this study was to investigate effects of thyroid hormones on uterine antioxidative status in young adult rats. Thirty immature female Sprague-Dawley rats were randomly divided into three groups: control, hypothyroid (hypo-T) and hyperthyroid (hyper-T). The results showed the body weights decreased significantly in both the hypo-T and hyper-T groups and that uterine weights were decreased significantly in the hypo-T group. The serum concentrations of total triiodothyronine (T3) and thyroxine (T4), as well as estradiol (E2), were significantly decreased in the hypo-T group, but increased in the hyper-T group. The progesterone (P4) concentrations in the hypo- and hyperthyroid rats markedly decreased. Immunohistochemistry results provided evidence that thyroid hormone nuclear receptor α/β (TRα/β) and three NOS isoforms were located in different cell types of rat uteri. The NO content and total NOS and inducible NOS (iNOS) activities were markedly diminished in the hypo-T group but increased in the hyper-T group. Moreover, the activities of both glutathione peroxidase (GSH-Px) and catalase (CAT) exhibited significant decreases and increases in the hypo-T and hyper-T groups, respectively. The malondialdehyde (MDA) contents in both the hypo-T and hyper-T groups showed a significant increase. Total superoxide dismutase (T-SOD) activity in the hypo- and hyper-T rats markedly decreased. In conclusion, these results indicated that thyroid hormones have an important influence on the modulation of uterine antioxidative status.