Dose-dependent effects of perinatal hypothyroidism on postnatal testicular development in rat offspring

Photoperiod-driven testicular DNA methylation in gonadotropin and sex steroid receptor promoters in Siberian hamsters

Seasonal cycles in breeding, often orchestrated by annual changes in photoperiod, are common in nature. Here, we studied how change in photoperiod affects DNA methylation in the testes of a highly seasonal breeder: the Siberian hamster (Phodopus sungorus). We hypothesized that DNA methylation in promoter regions associated with key reproductive genes such as follicle-stimulating hormone receptor in the testes is linked to breeding and non-breeding states. Using Oxford Nanopore sequencing, we identified more than 10 million (10,151,742) differentially methylated cytosine-guanine (CpG) sites in the genome between breeding long photoperiod and non-breeding short photoperiod conditions. ShinyGo enrichment analyses identified biological pathways consisting of reproductive system, hormone-mediated signalling and gonad development. We found that short photoperiod induced DNA methylation in the promoter regions for androgen receptor (Ar), estrogen receptors (Esr1, Esr2), kisspeptin1 receptor (kiss1r) and follicle-stimulating hormone receptor (Fshr). Long photoperiods were observed to have higher DNA methylation in promoters for basic helix-loop-helix ARNT-like 1 (Bmal1), progesterone receptor (Pgr) and thyroid-stimulating hormone receptor (Tshr). Our findings provide insights into the epigenetic mechanisms underlying seasonal adaptations in timing reproduction in Siberian hamsters and could be informative for understanding male fertility and reproductive disorders in mammals.

Roles of thyroid and leptin hormones and their crosstalk in male reproductive functions: an updated review

PURPOSE

This review aims to provide updated information regarding the role of thyroid and leptin hormones and their crosstalk in affecting the male reproductive function in hypothyroid and obesity conditions.

METHOD

A wide literature search was made using online search engines on published articles using keywords including thyroid hormone, hypothyroidism, leptin hormone, hyperleptinemia, obesity, the relationship between thyroid and leptin hormones and male reproduction, and hypothyroidism, obesity, and male reproduction.

RESULTS

All information pertaining thyroid and leptin hormone effects on male reproduction, hypothyroidism, hyperleptinemia, and obesity effect on male fertility as well as the related molecular mechanisms are obtained.

CONCLUSION

Thyroid and leptin hormones individually play a significant role in male reproduction. Alterations of these hormones' levels could adversely affect the male reproductive functions. PI3K/AKT signaling was found to be the major signaling pathway involved in mediating the effect of both hormones on male reproduction. Impaired crosstalk between the two hormones may occur in hypothyroidism with obesity which would contribute towards male reproductive dysfunction.

Perinatal exposure to environmental chemicals that disrupt thyroid function can perturb testis development

Thyroid hormones (THs) are essential for normal growth and development. Their role in skeletal and brain development is well established, with congenital hypothyroidism causing stunted growth and severe intellectual disability. THs are also important for the development of other tissues and organs, including the testis. Developmental hypothyroidism can manifest as smaller testes in early postnatal life that later develop into macroorchidism in adulthood due to increased proliferation of Sertoli cells. Effects of hypothyroidism on the testes can be modelled in rodents by exposing developing animals to TH-suppressing pharmaceuticals such as propylthiouracil (PTU) and methimazole (MMI). These drugs act by inhibiting the thyroperoxidase (TPO) enzyme in the thyroid gland, inhibiting the synthesis of THs. It is possible that environmental chemicals that inhibit TPO activity can also cause TH-mediated effects on the developing testis, but the extent to which this occurs is not known. Herein, we characterized the effects of perinatal exposure to the herbicide amitrole together with the antithyroid drug MMI. Pregnant Sprague-Dawley rats were exposed by oral gavage to two doses of amitrole (25 or 50 mg/kg body weight/day) or MMI (8 or 16 mg/kg body weight/day) from gestational day 7 until birth. After birth, pup exposure was continued by dosing lactating dams from day of delivery until pup day 16. Both chemicals caused a significant reduction in TH levels on day 16. This perinatal hypothyroidism disrupted both germ and Sertoli cell development, resulting in smaller testes and reduced seminiferous tubule diameter in 16-day old pups. Notably, fetal male blood progesterone levels were increased after exposure to both amitrole and MMI, whereas the amitrole-exposed animals also displayed increased estradiol levels. Our study raises concerns that exposure to environmental chemicals that happen to disrupt TH production may disrupt TH-dependent testis development, with adverse consequences to human reproductive health.

Thyroid disorders and male sexual dysfunction

Though early research suggested that thyroid hormones were not involved with the testes, male spermatogenesis, or erectile function, investigations on this topic over the past few decades have increased and shed new light. A literature review of studies conducted between 1963 and 2022 regarding male sexual dysfunction (SD) and thyroid disorders was performed to define the diagnostic consideration, pathophysiology, and management of SD secondary to thyroid dysregulation. This article provides evidence and interpretation of prior clinical and preclinical studies and contextualizes these studies for clinical practice. Clinical manifestations of SDs included erectile and ejaculatory dysfunction, impaired spermatogenesis, and disruption of the hypothalamic-pituitary-gonadal axis. Our aim of this communication was to perform a literature review detailing the impact of thyroid disorders on male SD. We hope to provide a framework for practicing urologists, endocrinologists, or general practitioners when evaluating patients with concurrent thyroid and male SD. It is important to recognize that thyroid disorders can be an important part of the pathophysiology of male SD in patients. Future research studies are needed to further elucidate the mechanisms involved.

Antioxidant effects of α-lipoic acid against epididymal oxidative damage in adult offspring rats exposed to maternal hypothyroidism stress

It is well known that the epididymis promotes post-testicular sperm maturation events. However, its malfunction during congenital hypothyroidism is relatively less understood as compared to the testis. The present study evaluated the probable effect of α-lipoic acid on epididymal oxidative stress parameters in rats exposed to antithyroid drug, carbimazole during fetal period. Time-mated pregnant rats in unexposed and carbimazole (1.35 mg/Kg body weight exposed were allowed to deliver pups and weaned. At postnatal day 100, the F1 male pups were assessed for epididymal endpoints. Among the epididymal regions, significant elevation of lipid peroxidation levels, superoxide anion, and hydrogen peroxide contents with a concomitant reduction in the activity levels of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and reduced glutathione levels were observed in cauda epididymis of carbimazole exposed rats over controls. Significant elevation in sperm DNA fragmentation (comet assay), accelerated cauda epididymal sperm transit time and reduction in epididymal sialic acid content was observed in carbimazole exposed rats. RT-qPCR studies revealed that embryonic exposure to carbimazole resulted in down regulation of androgen receptor, nuclear factor eryrthoid 2 like 2, 5α-reducatse 1 mRNA levels, while up regulation of caspase 3 mRNA was observed in epididymal regions of rats. In addition, fetal exposure to carbimazole resulted in disorganization of cauda epididymal architecture in rats. Conversely, supplementation of α-lipoic acid (70 mg/Kg bodyweight) during PND 3 to 14 restored epididymal functions in carbimazole exposed rats and the ameliorative effects of lipoic acid could be attributed to its antioxidant and steroidogenic effects.

Transcriptomic profiling identified altered expression of genes associated with testicular functions in adult F1 rats exposed to carbimazole during fetal period

The central goal of this study was to investigate the alterations in transcriptome of testis in F1 generation adult rats exposed to carbimazole prenatally. At post-natal day 100, the testis of rats delivered to carbimazole exposed (time-mated pregnant rats orally administered with carbimazole from gestation day 9 to 21) and control (untreated pregnant rats) groups were subjected to transcriptomic analysis using NGS platform. A total of 187 differentially expressed (up regulated: 49 genes; down regulated: 138) genes were identified in carbimazole exposed rats over controls and the major processes associated with these altered testicular transcripts were examined. Functional clustering analysis suggest that the involvement of identified DEGs were linked to intrinsic and extrinsic apoptotic pathways, mitochondrial solute carriers slc25a members, nuclear receptors/zinc family members, steroidogenic pathway and cholesterol synthesis, and growth factors and protein kinases and thus represent potential mediators of the developmental toxic effects of carbimazole in F1 generation rats. Based on the findings, it can be concluded that prenatal exposure to carbimazole prominently affects expression of multiple transcripts implicating key regulatory events associated with testicular functions, spermatogenesis and steroidogenesis in rats at their adulthood. These results support our earlier findings and hypothesis. This background information obtained at the testicular transcriptome during gestational hypothyroidism might be helpful for future studies and experiments to gain additional in-depth analysis and to develop strategies to protect F1 generation male reproductive health. SIGNIFICANCE: The rationale for the paper described thyroid gland changes in the off springs. Antithyroid drugs are widely used to control thyroid disorders and used to control thyroid hormone levels during surgeries. Carbimazole is one of the antithyroid drugs and is a parent molecule of methimazole. Both the drugs can able to cross placenta. During fetal period, the development of thyroid gland is not completely formed and hence, the fetus entirely depends on the maternal thyroid hormones. Therefore, it is conceivable that the disturbances at the level of maternal thyroid hormones could interfere with the development of vital organs such as testis and glands including thyroid gland (Kala et al., 2012). To address this notion, the present study was designed and executed.

The Induction of Hypothyroidism During Gestation Decreases Outer Hair Cell Motility in Rat Offspring

Introduction Perinatal hypothyroidism has a negative repercussion on the development and maturation of auditory system function. However, its long-term effect on auditory function remains unsettled.

Objective To evaluate the effect of prenatal hypothyroidism on the auditory function of adult offspring in rats.

Methods Pregnant Wistar rats were given the antithyroid drug methimazole (0.02% -1-methylimidazole-2-thiol– MMI) in drinking water, ad libitum, from gestational day (GD) 9 to postnatal day 15 (PND15). Anesthetized offspring from MMI-treated dams (OMTD) and control rats were evaluated by tympanometry, distortion product otoacoustic emission (DPOAE), and auditory brainstem response (ABR) at PNDs 30, 60, 90, and 120.

Results Our data demonstrated no middle ear dysfunction, with the OMTD compliance lower than that of the control group. The DPOAE revealed the absence of outer hair cells function, and the ABR showed normal integrity of neural auditory pathways up to brainstem level in the central nervous system. Furthermore, in the OMTD group, hearing loss was characterized by a higher electrophysiological threshold.

Conclusion Our data suggest that perinatal hypothyroidism leads to irreversible damage to cochlear function in offspring.

Multi Species Analyses Reveal Testicular T3 Metabolism and Signalling as a Target of Environmental Pesticides

Thyroid hormones (THs) regulate many biological processes in vertebrates, including reproduction. Testicular somatic and germ cells are equipped with the arrays of enzymes (deiodinases), transporters, and receptors necessary to locally maintain the optimal level of THs and their signalling, needed for their functions and spermatogenesis. Pesticides, as chlorpyrifos (CPF) and ethylene thiourea (ETU), impair the function of thyroid and testis, affecting male fertility. However, their ability to disarrange testicular T3 (t-T3) metabolism and signalling is poorly considered. Here, a multi-species analysis involving zebrafish and mouse suggests the damage of t-T3 metabolism and signalling as a mechanism of gonadic toxicity of low-doses CPF and ETU. Indeed, the developmental exposure to both compounds reduces Dio2 transcript in both models, as well as in ex-vivo cultures of murine seminiferous tubules, and it is linked to alteration of steroidogenesis and germ cell differentiation. A major impact on spermatogonia was confirmed molecularly by the expression of their markers and morphologically evidenced in zebrafish. The results reveal that in the adopted models, exposure to both pesticides alters the t-T3 metabolism and signalling, affecting the reproductive capability. Our data, together with previous reports suggest zebrafish as an evaluable model in assessing the action of compounds impairing locally T3 signalling.

Hypothyroidism induced by postnatal PTU (6-n-propyl-2-thiouracil) treatment decreases Sertoli cell number and spermatogenic efficiency in sexually mature pigs

Studies with 6-n-propyl-2-thiouracil (PTU) in laboratory rodents have shown that transient neonatal hypothyroidism leads to increased Sertoli cell (SC) number, testis size and sperm production. However, scarce and inconclusive data are available for farm animals. In the present study, Piau pigs received PTU in a gel capsule containing 8 mg/kg of body weight for 14 weeks starting from the first week of age, whereas control animals received only the vehicle. Blood samples were collected during the experimental period for hormonal evaluation in the serum. The animals were orchiectomized at adulthood and had their testes used for histomorphometric analysis. Indicating that the PTU concentration used was effective in promoting hypothyroidism, PTU-treated pigs showed a 30% lower body weight and reduced thyroxine levels (p < 0.05) during the treatment period. At adulthood, the body weight was similar in both groups but, surprisingly, PTU-treated pigs showed 30% lower testis weight (p < 0.05). In general, treated pigs presented increased follicle-stimulating hormone levels, whereas testosterone levels tended to be lower from 9 to 23 weeks of age. No significant differences were observed for estradiol, Leydig cell volume and number, tubular diameter, SC number per gram of testis, SC efficiency and meiotic index. However, seminiferous tubule occupancy, total tubular length, SC number per testis, and daily sperm production per testis and per gram of testis (DSP/g/T) were significantly lower (p < 0.05) in PTU-treated pigs. Therefore, in contrast to laboratory rodents, our results showed that SC proliferation and DSP/g/T (spermatogenic efficiency) in Piau pigs is diminished by postnatal PTU treatment.

Effects of maternal hypothyroidism in the gastrointestinal system of male young offspring from Wistar rats

Alterations in the maternal environment may impact on the fetal development. The objective of this study was to investigate the gastrointestinal consequences of maternal hypothyroidism for the male offspring from Wistar rats. The pregnant rats were divided into three groups: control (C - received water), experimental 1 [E1 - received methimazole (MMI) solution] during gestation and lactation, and experimental 2 (E2 - received MMI solution) during gestation. Maternal parameters evaluated: free T3 and T4, bodyweight variation, and water/food intake. Offspring parameters evaluated: litter size, number of male/female, free T3 and T4, stomach area, gastric ulcer susceptibility, small intestine length and weight, small intestine and distal colon motility, the stomach and intestinal weight-body weight ratio (SW/BW-IW/BW), and the accumulation of intestinal fluid. Maternal T3 and T4 from E1 were decreased when compared to the other groups. There were no differences for maternal water/food intake and weight gain, litter size, and number of males and females. Regarding to offspring, free T3, SW/BW, IW/BW, and intestinal fluid accumulation were not different between the groups, but T4 was decreased in E1. However, 30-day-old pups from E1 and E2 were smaller with lower stomach and small intestine. Even more, E1 presented a lower ulcer index when compared to the C, while E2 had a higher distal colon transit. It can be concluded that maternal hypothyroidism impaired the total body development, as well as gastric and intestinal development, besides interfering with the susceptibility to the ulcer and intestinal transit of male offspring from Wistar rats.

3, 3', 5-Triiodo-L-thyronine affects polarity proteins of bovine Sertoli cells via WT1/non-canonical Wnt signaling pathway

To determine the role of 3, 3', 5-triiodo-L thyroxine (T3) in the differentiation of Sertoli cells (SCs) and the factors influencing maturity via the Wilms' tumor 1 (WT1)/non-canonical Wnt signaling pathway, high purity SCs were isolated from newborn calves' testes and cultured in vitro. The SCs were stimulated with T3, and co-treated with short interference (si) RNA to knockdown endogenous WT1 and non-canonical Wnt signalling inhibitor Wnt-c59. Our results suggested that the addition of different concentrations (0, 25, 50, and 100 nM) of T3 in the culture medium changed the expression of KRT-18 (SCs immature marker) and accelerated the differentiation of SCs. T3 (100 nM) treatment induced up-regulated expression of WT1 over time (p < 0.05), while the expression of polarity proteins (Par3, Par6b, and E-cadherin) and Wnt4 were affected to varying degrees (p < 0.05). SCs were treated simultaneously with T3 + Wnt-c59 and T3 + WT1 siRNA, and the results showed that T3 could affect the expression of polarity proteins via WT1/non-canonical Wnt signaling pathway. These data put together indicate that T3 plays a dependent role in the induction of bovine SCs differentiation via WT1/non-canonical Wnt signaling pathway in vitro. This study proposes for the first time that WT1 is a major target for T3.

Thyroid hormone action in the developing testis: intergenerational epigenetics

Male fertility involves the successful transmission of the genetic code to the next generation. It requires appropriately timed cellular processes during testis development, adequate support of spermatogenesis by hormonal cues from the reproductive axis and cellular cross-talk between germ and somatic cells. In addition to being the vessel of the father’s genome, increasing evidence shows that the mature sperm carries valuable epigenetic information – the epigenome – that, after fecundation, influences the development of the next generation, affecting biological traits and disease susceptibility. The epigenome of the germ line is susceptible to environmental factors, including exogenous chemicals and diet, but it is also affected by endogenous molecules and pathophysiological conditions. Factors affecting testis development and the epigenetic information of the germ line are critical for fertility and of relevance to the non-genetic but heritable component in the etiology of complex conditions. Thyroid hormones are one of those factors and their action, when untimely, produces profound effects on the developing testis, affecting spermatogenesis, steroidogenesis, testis size, reproductive hormones and fertility. Altered thyroid hormone states can also change the epigenetic information of the male germ line, with phenotypic consequences for future generations. In the context of past literature concerning the consequences of altered thyroid hormone action for testis development, here we review recent findings about the pathophysiological roles of the principal determinants of testicular thyroid hormone action. We also discuss limited work on the effects of thyroid hormone on the male germ line epigenome and the implications for the intergenerational transmission of phenotypes via epigenetic mechanisms.

Spermatogonial Type 3 Deiodinase Regulates Thyroid Hormone Target Genes in Developing Testicular Somatic Cells

Premature overexposure to thyroid hormone causes profound effects on testis growth, spermatogenesis, and male fertility. We used genetic mouse models of type 3 deiodinase (DIO3) deficiency to determine the genetic programs affected by premature thyroid hormone action and to define the role of DIO3 in regulating thyroid hormone economy in testicular cells. Gene expression profiling in the neonatal testis of DIO3-deficient mice identified 5699 differentially expressed genes. Upregulated and downregulated genes were, respectively, involved according to DAVID analysis with cell differentiation and proliferation. They included anti-Müllerian hormone and genes involved in the formation of the blood-testis barrier, which are specific to Sertoli cells (SCs). They also included steroidogenic genes, which are specific to Leydig cells. Comparison with published data sets of genes enriched in SCs and spermatogonia, and responsive to retinoic acid (RA), identified a subset of genes that were regulated similarly by RA and thyroid hormone. This subset of genes showed an expression bias, as they were downregulated when enriched in spermatogonia and upregulated when enriched in SCs. Furthermore, using a genetic approach, we found that DIO3 is not expressed in SCs, but spermatogonia-specific inactivation of DIO3 led to impaired testis growth, reduced SC number, decreased cell proliferation and, especially during neonatal development, altered gene expression specific to somatic cells. These findings indicate that spermatogonial DIO3 protects testicular cells from untimely thyroid hormone signaling and demonstrate a mechanism of cross-talk between somatic and germ cells in the neonatal testis that involves the regulation of thyroid hormone availability and action.

Phthalate-Induced Fetal Leydig Cell Dysfunction Mediates Male Reproductive Tract Anomalies

Male fetal Leydig cells in the testis secrete androgen and insulin-like 3, determining the sexual differentiation. The abnormal development of fetal Leydig cells could lead to the reduction of androgen and insulin-like 3, thus causing the male reproductive tract anomalies in male neonates, including cryptorchidism and hypospadias. Environmental pollutants, such as phthalic acid esters (phthalates), can perturb the development and differentiated function of Leydig cells, thereby contributing to the reproductive toxicity in the male. Here, we review the epidemiological studies in humans and experimental investigations in rodents of various phthalates. Most of phthalates disturb the expression of various genes encoded for steroidogenesis-related proteins and insulin-like 3 in fetal Leydig cells and the dose-additive effects are exerted after exposure in a mixture.

Low dose of flurochloridone affected reproductive system of male rats but not fertility and early embryonic development

BACKGROUND

Fluorochloridone (FLC) is a widely used herbicide, and its target organs are testes and epididymides. The Globally Harmonized System of Classification and Labelling of Chemicals classified FLC as Level 2-possibly cause fertility or fetal damage (no relevant data support). The maximum residue levels of FLC in processed crops have been reviewed in the latest European Food Safety Authority (EFSA) report in 2018. However, the toxic effect of FLC on fertility and early embryonic development is limited, and the health risk assessment of FLC needs further consideration. This study investigated the potential effects of FLC on fertility and early embryonic development in rats.

METHODS

One hundred rats of each sex were divided into four groups including three FLC-treated groups at doses of 2 mg/kg, 5 mg/kg and 15 mg/kg, and a vehicle control group (0.5% (w/v) sodium carboxymethyl cellulose). Male and female rats were dosed for 9 and 2 consecutive weeks, intragastrically, prior to cohabitation and lasted throughout the mating period for males and continued until Gestation Day 7 (GD7) for females. Parameters such as weights and coefficients of reproductive organs, epididymal sperm number and motility, indexes of copulation, fecundity and fertility indexes, mating period, estrous cycle, corporalutea number, implantations, live, dead and resorbed fetuses, preimplantation loss rate, and postimplantation loss rate were observed in this study.

RESULTS

Obvious toxicity of male reproductive system was found at the dose of 15 mg/kg including decreases in testicular and epididymal weight, also in sperm motility rate. Whereas the increase in sperm abnormality rate was observed. However, no significant effects of FLC were found on lutea count, implantations count, fetuses count and weight, live fetuses count (rate), dead fetuses count (rate), resorbed fetuses count (rate), placentas weight, fetuses gender, preimplantation loss (rate) and postimplantation loss (rate). Furthermore, FLC had no adverse effects on fertility and early embryonic development in rats.

CONCLUSION

The no-observable-adverse-effect level (NOAEL) of FLC on fertility and early embryonic development in rats was considered to be 5 mg/kg/day.

Thyroid Hormone Deiodination and Action in the Gonads

Alterations in thyroid hormone (TH) status during developmental or adult age are associated with abnormal gonadal development and function in human and animal models. In the developing testis, aberrant levels of TH action lead to disruptions in cell proliferation and differentiation, ultimately influencing testicular size, spermatogenesis, steroidogenesis and male fertility. Recent work is increasingly identifying the systems and signaling pathways in gonadal cells that are affected by TH, as well as delineating the major factors that determine TH signaling in gonadal tissue. The TH receptor alpha, the monocarboxylate transporter 8 and the type 3 deiodinase appear to be major contributors to the timely regulation of TH action in the developing testis.

EDC IMPACT: Reduced sperm counts in rats exposed to human relevant mixtures of endocrine disrupters

Human semen quality is declining in many parts of the world, but the causes are ill defined. In rodents, impaired sperm production can be seen with early life exposure to certain endocrine-disrupting chemicals, but the effects of combined exposures are not properly investigated. In this study, we examined the effects of early exposure to the painkiller paracetamol and mixtures of human relevant endocrine-disrupting chemicals in rats. One mixture contained four estrogenic compounds; another contained eight anti-androgenic environmental chemicals and a third mixture contained estrogens, anti-androgens and paracetamol. All exposures were administered by oral gavage to time-mated Wistar dams rats (n = 16-20) throughout gestation and lactation. In the postnatal period, testicular histology was affected by the total mixture, and at the end of weaning, male testis weights were significantly increased by paracetamol and the high doses of the total and the anti-androgenic mixture, compared to controls. In all dose groups, epididymal sperm counts were reduced several months after end of exposure, i.e. at 10 months of age. Interestingly, the same pattern of effects was seen for paracetamol as for mixtures with diverse modes of action. Reduced sperm count was seen at a dose level reflecting human therapeutic exposure to paracetamol. Environmental chemical mixtures affected sperm count at the lowest mixture dose indicating an insufficient margin of safety for the most exposed humans. This causes concern for exposure of pregnant women to paracetamol as well as environmental endocrine disrupters.

Neonatal hypothyroidism does not increase Sertoli cell proliferation in iNOS−/− mice

Sertoli cell (SC) proliferation in mice occurs until two weeks after birth and is mainly regulated by FSH and thyroid hormones. Previous studies have shown that transient neonatal hypothyroidism in laboratory rodents is able to extend SC mitotic activity, leading ultimately to higher testis size and daily sperm production (DSP) in adult animals. Moreover, we have shown that due to higher SC proliferation and lower germ cell apoptosis, iNOS deficiency in mice also results in higher testis size and DSP. Although the cell size was smaller, the Leydig cells (LCs) number per testis also significantly increased in iNOS−/−mice. Our aims in the present study were to investigate if the combination of neonatal hypothyroidism and iNOS deficiency promotes additive effects in SC number, testis size and DSP. Hypothyroidism was induced in wild-type (WT) and iNOS−/−mice using 6-propyl-2-thiouracil (PTU) through the mother’s drinking water from 0 to 20 days of age, and were sacrificed at adulthood. Our results showed that, in contrast to the WT mice in which testis size, DSP and SC numbers increased significantly by 20, 40 and 70% respectively, after PTU treatment, no additive effects were observed for these parameters in treated iNOS−/−mice, as well as for LC. No alterations were observed in spermatogenesis in any group evaluated. Although we still do not have an explanation for these intriguing findings, we are currently investigating whether thyroid hormones influence iNOS levels and/or counterbalance physiological effects of iNOS deficiency in testis function and spermatogenesis.

α-lipoic acid inhibits oxidative stress in testis and attenuates testicular toxicity in rats exposed to carbimazole during embryonic period

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The intrauterine exposure of carbiamzole (CBZ) on male fertility is not well defined.

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CBZ exposure in utero results in spermatotoxic effects and impaired steroidogenesis in offspring rats at their adulthood.

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Gestational exposure to CBZ augmented testicular oxidative damage in offspring rats.

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α-lipoic acid supplementation with its antioxidant properties ameliorated diminished male reproductive health in rats exposed to CBZ prenatally.

The aim of this study was to evaluate the probable protective effect of α-lipoic acid against testicular toxicity in rats exposed to carbimazole during the embryonic period. Time-mated pregnant rats were exposed to carbimazole from the embryonic days 9–21. After completion of the gestation period, all the rats were allowed to deliver pups and weaned. At postnatal day 100, F1 male pups were assessed for the selected reproductive endpoints. Gestational exposure to carbimazole decreased the reproductive organ indices, testicular daily sperm count, epididymal sperm variables viz., sperm count, viable sperm, motile sperm and HOS-tail coiled sperms. Significant decrease in the activity levels of 3β- and 17β-hydroxysteroid dehydrogenases and expression of StAR mRNA levels with a significant increase in the total cholesterol levels were observed in the testis of experimental rats over the controls. These events were also accompanied by a significant reduction in the serum testosterone levels in CBZ exposed rats, indicating reduced steroidogenesis. In addition, the deterioration of the testicular architecture and reduced fertility ability were noticed in the carbimazole exposed rats. Significant reduction in the activity levels of superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and reduced glutathione content with a significant increase in the levels of lipid peroxidation were observed in the testis of carbimazole exposed rats over the controls. Conversely, supplementation of α-lipoic acid (70 mg/Kg bodyweight) ameliorated the male reproductive health in rats exposed to carbimazole during the embryonic period as evidenced by enhanced reproductive organ weights, selected sperm variables, testicular steroidogenesis, and testicular enzymatic and non-enzymatic antioxidants. To conclude, diminished testicular antioxidant balance associated with reduced spermatogenesis and steroidogenesis might be responsible for the suppressed reproduction in rats exposed to the carbimazole transplacentally. On the other hand, α-lipoic acid through its antioxidant and steroidogenic properties mitigated testicular toxicity which eventually restored the male reproductive health of carbimazole-exposed rats.