Decreased expression of orexin 1 receptor in adult mice testes during alloxan-induced diabetes mellitus perturbs testicular steroidogenesis and glucose homeostasis

Knockdown of type 2 orexin receptor in adult mouse testis potentiates testosterone production and germ cell proliferation

Orexins (OXs) are neuropeptides which regulate various physiological processes. OXs exist in two different forms, mainly orexin A (OXA) and orexin B (OXB) and their effects are mediated via OX1R and OX2R. Presence of OXB and OX2R in mouse testis is also reported. However, the role of OXB/OX2R in the male gonad remains unexplored. Herein we investigated the role of OXB/OX2R system in testicular physiology under in vivo and ex vivo conditions. Adult mice were given a single dose of bilateral intratesticular injection of siRNA targeting OX2R and were sacrificed 96 h post-injection. OX2R-knockdown potentiated serum and intratesticular testosterone levels with up-regulation in the expressions of major steroidogenic proteins. Germ cell proliferation also increased in siRNA-treated mice. Results of the ex vivo experiment also supported the findings of the in vivo study. In conclusion, OX2R may regulate testosterone production and thereby control the fine-tuning between steroidogenesis and germ cell dynamics.

Betaine regulates steroidogenesis, endoplasmic reticulum stress response and Nrf2/HO-1 antioxidant pathways in mouse Leydig cells under hyperglycaemia condition

We studied the effects of betaine on steroidogenesis, endoplasmic reticulum stress and Nrf2 antioxidant pathways of mice Leydig cells under hyperglycaemia conditions. Leydig cells were grown in low and high glucose concentrations (5 mM and 30 mM) in the presence of 5 mM of betaine for 24 h. Gene expression was determined using a real-time PCR method. The protein levels were determined by Western blot analysis. The testosterone production was evaluated by the ELISA method. Cellular contents of reduced and oxidised glutathione were measured by colorimetric method. Hyperglycaemia caused impaired steroidogenesis and ERS in Leydig cells associated with the down-regulation of 3β-HSD, StAR, P450scc, LH receptor and increased expression of GRP78, CHOP, ATF6 and IRE1. Betaine could improve cell viability, attenuate the ERS, and restore testosterone production in Leydig cells under hyperglycaemia conditions. Betaine can protect Leydig cells against the adverse effects of hyperglycaemia by regulating steroidogenesis, antioxidants, and ERS.

Localization and expression of Orexin B (OXB) and its type 2 receptor (OX2R) in mouse testis during postnatal development

The orexins (OXs) were first reported in hypothalamus of rat, and they play an important role in diverse physiological actions. The OXs consist of orexin A (OXA) and orexin B (OXB) peptides and their actions are mediated via two G-protein-coupled receptors, orexin 1 receptor (OX1R) and orexin 2 receptor (OX2R), respectively. Presence of OXA and OX1R has been also reported in peripheral organs like reproductive tissues. These findings, therefore, highlight a possible role of OXs and their receptors in male reproductive health. Though, expression and localization of OXB and OX2R in the testis and their role in spermatogenesis are not finally clarified. Herein, we elucidated the localization and the patterns of expression of OXB and OX2R in Parkes mice testes during postnatal development. Results suggest that the precursor prepro-orexin (PPO), OXB and OX2R are expressed at the transcript and protein levels in mouse testis throughout the postnatal development. Immunostaining further showed the localization of OXB and OX2R both in interstitium and tubular compartments of the testis. On 7 day postpartum (7 dpp), only spermatogonia showed immunoreactivity of OXB and OX2R, while at 14, 28, 42 and 90 dpp, immunolocalization of OXB and OX2R were noted in the seminiferous tubules, especially in leptotene, pachytene spermatocytes, round and elongating spermatids, and in Leydig cells and Sertoli cells. The immunoreactivity of OXB and OX2R appeared to be stage-specific in adult mouse testis. The results suggest the expression of OXB and OX2R in mouse testis and their possible regulatory role in spermatogenesis and steroidogenesis.

Obstructive Sleep Apnea, Circadian Clock Disruption, and Metabolic Consequences

Obstructive sleep apnea (OSA) is a chronic disorder characterized by recurrent episodes of apnea and hypopnea during sleep. It is associated with various cardiovascular and metabolic complications, including type 2 diabetes mellitus (T2DM) and obesity. Many pathways can be responsible for T2DM development in OSA patients, e.g., those related to HIF-1 and SIRT1 expression. Moreover, epigenetic mechanisms, such as miRNA181a or miRNA199, are postulated to play a pivotal role in this link. It has been proven that OSA increases the occurrence of circadian clock disruption, which is also a risk factor for metabolic disease development. Circadian clock disruption impairs the metabolism of glucose, lipids, and the secretion of bile acids. Therefore, OSA-induced circadian clock disruption may be a potential, complex, underlying pathway involved in developing and exacerbating metabolic diseases among OSA patients. The current paper summarizes the available information pertaining to the relationship between OSA and circadian clock disruption in the context of potential mechanisms leading to metabolic disorders.

Sub-chronic restraint stress exposure in adult rats: An insight into possible inhibitory mechanism on testicular function in relation to germ cell dynamics

Psychological stress is now widely recognized as one of the major risk factors for male fertility. Its impact on the dynamics of testicular germ cells, however, has yet to be fully investigated. Therefore, we used the rat restraint stress (RS) model as a psychological stressor to assess the impact of psychological stress on testicular germ cell dynamics. Adult male SD rats were exposed to sub-chronic RS for 1.5 and 3 h per day for 30 days. The quality of cauda epididymis spermatozoa was adversely affected by RS exposure, and the frequency of spermatozoa with tail abnormalities was higher than that of spermatozoa with head abnormalities. RS exposure adversely affected testicular daily sperm production by disturbing the meiotic and post meiotic germ cell kinetics in the testis. The histomorphology of the testis was altered by loosening and vacuolization in the seminiferous epithelium, germ cell exfoliation and the presence of giant cells. Seminiferous tubules of stage I-VI and VII-VIII were severely affected in rats exposed to RS for 3 h. By interfering with steroidogenic enzymes, RS exposure disrupts testosterone biosynthesis. The testicular oxidative balance was also disturbed by RS exposure, which disrupted the levels/activities of lipid peroxidation, Nrf-2, superoxide dismutase and catalase. There was also an increase in caspase-3 activity and a decrease in the Bax-Bcl2 ratio. In conclusion, our findings suggest that psychological stressors like RS impair testicular functions in rats by disrupting germ cell dynamics, downregulating testicular androgenesis and increasing oxidative stress and apoptosis.

Investigating the therapeutic options for diabetes-associated male infertility as illustrated in animal experimental models

Diabetes is a rising global health concern and an increasingly common cause of male infertility. Although the definitive pathophysiological mechanisms underpinning the association between diabetes and infertility is unclear, there are several animal studies showing diabetes to be a detrimental factor on reproductive health through apoptosis, oxidative stress and impairment of steroidogenesis. Furthermore, as reflected in animal models, antidiabetic strategies and relevant treatments are beneficial in the management of infertile men with diabetes as the recovery of euglycemic status affects positively the spermatogenesis. However, the available data are still evolving and specific conclusion in human populations are not possible yet. In this review, we are discussing the current literature concerning the association of diabetes and male infertility, focusing on the therapeutic approach as illustrated in animals' models.

Pyroglutamylated RFamide peptide (QRFP): Role in early testicular development in relation to Sertoli cell maturation in prepubertal mice

QRFP, an orexigenic neuropeptide, binds to its cognate receptor GPR103 and regulates various biological functions. We have recently shown that QRFP and its receptor are present in mice testes and that their expression is high during early postnatal period. The present study aimed to investigate the effect of sustained high level of QRFP on Sertoli cells proliferation and differentiation and to relate these events with germ cell differentiation and lumen formation in the seminiferous tubules in mice testes during prepubertal period. QRFP was injected intraperitoneally to male mice from postnatal day 5 to 16. Morphometric analysis and various markers related to Sertoli cell maturation (WT1, p27kip1, AMH, AR and CYP19A1) and germ cell proliferation and differentiation (PCNA, GDNF and c-Kit) were evaluated. QRFP administration caused an early lumen formation in the seminiferous tubules in testis of treated mice. Further, there was a significant increase in p27kip1 expression and a marked decrease in AMH expression in QRFP-treated mice compared to controls. However, no appreciable change was noted in AR expression in treated mice. QRFP treatment also caused an increase in c-Kit expression in treated mice compared to controls, suggesting an accelerated spermatogonial differentiation in testis of QRFP-treated mice. Taken together, the present results suggest that the prolonged high level of QRFP increases Sertoli cell maturation, which, in turn, plays a contributory role in increasing the pace of germ cell differentiation and formation of lumen in the seminiferous tubules.

An overview of the orexinergic system in different animal species

Orexin (hypocretin), is a neuropeptide produced by a subset of neurons in the lateral hypothalamus. From the lateral hypothalamus, the orexin-containing neurons project their fibres extensively to other brain structures, and the spinal cord constituting the central orexinergic system. Generally, the term ''orexinergic system'' usually refers to the orexin peptides and their receptors, as well as to the orexin neurons and their projections to different parts of the central nervous system. The extensive networks of orexin axonal fibres and their terminals allow these neuropeptidergic neurons to exert great influence on their target regions. The hypothalamic neurons containing the orexin neuropeptides have been implicated in diverse functions, especially related to the control of a variety of homeostatic functions including feeding behaviour, arousal, wakefulness stability and energy expenditure. The broad range of functions regulated by the orexinergic system has led to its description as ''physiological integrator''. In the last two decades, the orexinergic system has been a topic of great interest to the scientific community with many reports in the public domain. From the documentations, variations exist in the neuroanatomical profile of the orexinergic neuron soma, fibres and their receptors from animal to animal. Hence, this review highlights the distinct variabilities in the morphophysiological aspects of the orexinergic system in the vertebrate animals, mammals and non-mammals, its presence in other brain-related structures, including its involvement in ageing and neurodegenerative diseases. The presence of the neuropeptide in the cerebrospinal fluid and peripheral tissues, as well as its alteration in different animal models and conditions are also reviewed.

Umbelliferone ameliorates oxidative stress and testicular injury, improves steroidogenesis and upregulates peroxisome proliferator-activated receptor gamma in type 2 diabetic rats

OBJECTIVES

Diabetes mellitus (DM) is a chronic disease associated with serious complications, including male infertility. Umbelliferone (UMB) is a coumarin with promising antioxidant, anti-inflammatory and other beneficial effects. This study investigated the ameliorative effect of UMB against testicular injury, oxidative stress and altered steroidogenesis in rats with type 2 DM.

METHODS

Rats received a high fat diet for 4 weeks followed by a single injection of streptozotocin. Diabetic rats were treated with UMB or pioglitazone (PIO) for 6 weeks and samples were collected for analysis.

KEY FINDINGS

Diabetic rats exhibited hyperglycemia, insulin resistance and dyslipidemia associated with increased serum pro-inflammatory cytokines, and decreased gonadotropins and testosterone. UMB significantly ameliorated metabolic alterations, decreased pro-inflammatory cytokines, and increased gonadotropins and testosterone levels. UMB prevented testicular injury, suppressed lipid peroxidation and nitric oxide and increased antioxidants in diabetic rats. In addition, UMB upregulated testicular gonadotropins receptors, steroidogenesis markers (steroidogenic acute regulatory protein, cytochrome P450 family 17 subfamily A member 1 [CYP17A1], 3β-hydroxysteroid dehydrogenase [3ß-HSD] and 17ß-hydroxysteroid dehydrogenase [17ß-HSD]), and peroxisome proliferator-activated receptor gamma (PPARγ) expression.

CONCLUSIONS

UMB prevents testicular injury by preventing metabolic alterations, suppressing oxidative damage and inflammation, and boosting antioxidant defenses in diabetic rats. UMB enhanced pituitary-gonadal axis and steroidogenesis and upregulated testicular PPARγ in diabetic rats. Thus, UMB may represent a protective agent against testicular injury and sexual dysfunction associated with chronic hyperglycemia.

Metformin mitigates impaired testicular lactate transport/utilisation and improves sexual behaviour in streptozotocin-induced diabetic rats

CONTEXT

Lactate is the preferred energy substrate for developing testicular germ cells. Diabetes is associated with impaired testicular lactate transport/utilisation, and poor sexual behaviour.

OBJECTIVE

To examine the effects of metformin on parameters involved in testicular lactate production, transport/utilisation, and sexual behaviour in diabetic state.

METHODS

Male Sprague-Dawley rats were assigned into normal control (NC), diabetic control (DC), and metformin-treated diabetic group (n = 6/group). Metformin (300 mg/kg b.w./day) was administrated orally for 4 weeks.

RESULTS

Intra-testicular glucose and lactate levels, and lactate dehydrogenase (LDH) activity increased, while the mRNA transcript levels of genes responsible for testicular glucose and lactate transport/utilisation (glucose transporter 3, monocarboxylate transporter 4 (MCT4), MCT2, and LDH type C) decreased in DC group. Furthermore, penile nitric oxide increased, while cyclic guanosine monophosphate decreased, with impaired sexual behaviour in DC group. Treatment with metformin improved these parameters.

CONCLUSIONS

Metformin increases testicular lactate transport/utilisation and improves sexual behaviour in diabetic state.

Role of pyroglutamylated RFamide peptide43 in germ cell dynamics in mice testes in relation to energy metabolism

QRFP is a neuropeptide that regulates glucose homeostasis and increases insulin sensitivity in tissues. We have previously shown that QRFP and its receptor (GPR103) are predominantly expressed in germ cells and Sertoli cells, respectively, in mice testes. In the present study, we report that QRFP caused an increase in PCNA and a decrease in p27Kip1 expressions in the testis under both in vivo and ex vivo conditions. Besides, via an in vivo study, cell cycle analysis by FACS showed an increase in 2C cells and a decrease in 1C cells. QRFP also induced expression of GDNF and phosphorylation of Akt and ERK-1/2. Together these results suggest that QRFP has a proliferative effect on germ cells in mice testes, since it caused a proportional increase in the mitotic activity and the number of spermatogonial cells. Further, observations of increased expressions of STAT-3 and Neurog3 in treated mice suggest that QRFP treatment regulates priming of undifferentiated spermatogonia to undergo differentiation, while a decrease in c-Kit expression indicate that spermatogonia at this time point are in an undifferentiated state. In addition, QRFP administration also caused an increase in intratesticular levels of glucose and lactate, and in LDH activity accompanied by increased expressions of GLUT-3 and LDH-C in the testis. Also, the phosphorylation of IR-β and expressions of p-Akt and p-mTOR were increased under ex vivo conditions in testicular tissue. In conclusion, our findings suggest that QRFP treatment caused proliferation of germ cells independently from the hypothalamic-pituitary axis via regulation of testicular energy metabolism.

The role of diosgenin in diabetes and diabetic complications

Diabetes mellitus is a chronic and common metabolic disease that seriously endangers human health. Hyperglycemia and long-term metabolic disorders in diabetes will cause damage to the whole body tissues and organs, resulting in serious complications. Nowadays, drugs for treating diabetes on the market has strong side effects, new treatments thus are urgently needed. Natural therapy of natural ingredients is a promising avenue, this is because natural ingredients are safer and they also show strong activity in the treatment of diabetes. Diosgenin is such a very biologically active natural steroidal sapogenin. The research of diosgenin in the treatment of diabetes and its complications has been widely reported. This article reviews the effects of diosgenin through multiple targets and multiple pathways in diabetes and its complications which including diabetic nephropathy, diabetic liver disease, diabetic neuropathy, diabetic vascular disease, diabetic cardiomyopathy, diabetic reproductive dysfunction, and diabetic eye disease.

Malaysian propolis and metformin mitigate subfertility in streptozotocin-induced diabetic male rats by targeting steroidogenesis, testicular lactate transport, spermatogenesis and mating behaviour

BACKGROUND

Diabetes mellitus is one of the risk factors for male subfertility/infertility. Malaysian propolis is reported to decrease hyperglycaemia in diabetic state.

OBJECTIVES

The present study investigated the protective effect of Malaysian propolis on diabetes-induced subfertility/infertility. Additionally, its combined beneficial effects with metformin were investigated.

MATERIALS AND METHODS

Forty adult male Sprague Dawley rats were randomly assigned into five groups, namely normal control, diabetic control, diabetic + Malaysian propolis (300 mg/k.g. b.w.), diabetic + metformin (300 mg/kg b.w.) and diabetic + Malaysian propolis + metformin. Diabetes was induced using a single intraperitoneal injection of streptozotocin (60 mg/kg b.w.) and treatment lasted for 4 weeks. During the 4th week, mating behavioural experiments were performed using sexually receptive female rats. Thereafter, fertility parameters were assessed in the female rats.

RESULTS

Malaysian propolis increased serum and intratesticular free testosterone levels, up-regulated the mRNA levels of AR and luteinizing hormone receptor, up-regulated the mRNA and protein levels of StAR, CYP11A1, CYP17A1, 3β-HSD and 17β-HSD in the testes of diabetic rats. Furthermore, Malaysian propolis up-regulated testicular MCT2, MCT4 and lactate dehydrogenase type C mRNA levels, in addition to improving sperm parameters (count, motility, viability and normal morphology) and decreasing sperm nDNA fragmentation in diabetic rats. Malaysian propolis improved mating behaviour by increasing penile guanosine monophosphate levels. Malaysian propolis also improved fertility outcome as seen with decreases in pre- and post-implantation losses, increases in gravid uterine weight, litter size per dam and foetal weight. Malaysian propolis's effects were comparable to metformin. However, their combination yielded better results relative to the monotherapeutic interventions.

CONCLUSION

Malaysian propolis improves fertility potential in diabetic state by targeting steroidogenesis, testicular lactate metabolism, spermatogenesis and mating behaviour, with better effects when co-administered with metformin. Therefore, Malaysian propolis shows a promising complementary effect with metformin in mitigating Diabetes mellitus-induced subfertility/infertility.

Ameliorative effect of combined low dose of Pioglitazone and omega-3 on spermatogenesis and steroidogenesis in diabetic rats

BACKGROUND

Chronic hyperglycemia is linked to either subfertility or infertility among diabetic males. Pioglitazone is one of the thiazolidinediones (TZDs) drugs that are selective peroxisome proliferator-activated receptor (PPAR-γ agonists used for treating type 2 diabetes mellitus (T2DM).

AIM

This study aims to explore the possible effect of low Pioglitazone dose and omega (ω-3) on rat male reproductive function. Furthermore, we evaluated the add-on effect of combined use of low Pioglitazone dose of and ω-3 on reproductive functions in adult male T2DM rats.

METHODS

Fifty adult male rats were included and subdivided into control and four test subgroups. T2DM was induced in test groups and subdivided into non-treated T2DM, ω-3 treated, 0.6 mg/kg Pioglitazone treated, and combined treated group (orally by gavage). Following 16 weeks, final body weight, testicular weight, fasting plasma glucose, and serum testosterone levels were measured. Semen analysis, testicular testosterone, malondialdehyde (MDA) concentrations, superoxide dismutase (SOD) activity, immunohistochemistry staining for apoptosis marker B-cell lymphoma protein 2 (Bcl-2), proliferation marker as proliferating cell nuclear antigen (PCNA), estrogen receptor α (ERα), androgen receptor (AR) were determined. Caspase-3, nuclear factor-kappa B (NF-kB), glucose transporter 3 (GLUT3), 17β-hydroxysteroid dehydrogenases (17β-HSD) PPARγ, and PPARα genes expression were analyzed by real-time polymerase chain reaction (RT-PCR).

RESULTS

Our findings revealed that treatment with low dose of Pioglitazone or ω-3 significantly lowered fasting plasma glucose and MDA levels, ameliorated diabetes effects on histological damage, improved antioxidant activity (SOD), significantly improved anti-apoptosis BCL-2 and proliferation (PCNA), remarkably elevated ERα, AR, 17β-HSD PPARγ, and PPARα expression with significant reduction in caspase-3, NF-kB genes expression and improved semen quality as well. Combined use of low dose of and ω-3 has better effects on all measured parameters.

CONCLUSION

Small Pioglitazone dose and ω-3 possess beneficial effects on spermatogenic and steroidogenic functions in adult diabetic rat; while combined use of both has an add-on effect.

Exploring the role of orexin B-sirtuin 1-HIF-1α in diabetes-mellitus induced vascular endothelial dysfunction and associated myocardial injury in rats

AIM

The present study explored the role and possible interrelationship between orexin B-sirtuin 1-HIF-1α signaling pathways in diabetes-mellitus induced vascular dysfunction and enhancement in myocardial injury.

MATERIAL AND METHODS

Streptozotocin (60 mg/kg) was employed to induce diabetes mellitus in male Wistar albino rats, which were kept for eight weeks. The vascular function was noted by assessing acetylcholine-induced relaxation in norepinephrine precontracted mesenteric arteries. The hearts were subjected to ischemia-reperfusion injury on the Langendorff apparatus. Myocardial injury was assessed by noting the release of CK-MB, cardiac troponin and measuring myocardial infarction. The levels of orexin B, sirtuin 1 and HIF-1α were measured. YNT-185 (orexin B type 2 receptor agonist), STR2104 (sirtuin 1 agonist) and EX527 (sirtuin 1 antagonist) were employed as pharmacological tools.

RESULTS

Diabetes led to significant development of vascular dysfunction and enhanced ischemia-reperfusion injury in isolated hearts. There was a significant decrease in the levels of orexin B, sirtuin 1 and HIF-1α in diabetic animals. Treatment with YNT-185 and/or STR2104 significantly attenuated the diabetes-induced increase in myocardial injury and vascular dysfunction. Co-administration of EX527 abolished the effects of YNT-185 suggesting orexin B-mediated effects may be through activation of sirtuin 1. Moreover, YNT-185-induced increase in the expression of sirtuin 1 and HIF-1α was also abolished in the presence of EX527.

CONCLUSION

Diabetes-induced significant decline in orexin B levels in the plasma along with a decrease in the expression of sirtuin 1 and HIF-1α in the heart following ischemia-reperfusion injury may possibly contribute in exacerbating the myocardial injury and vascular dysfunction.

Down-regulation of steroidogenesis-related genes and its accompanying fertility decline in streptozotocin-induced diabetic male rats: ameliorative effect of metformin

BACKGROUND

Metformin has long been used for glycemic control in diabetic state. Recently, other benefits of metformin beyond blood glucose regulation have emerged.

OBJECTIVES

To investigate the effect of metformin on the expression of testicular steroidogenesis-related genes, spermatogenesis, and fertility of male diabetic rats.

MATERIALS AND METHODS

Eighteen adult male Sprague Dawley rats were divided into three groups, namely normal control (NC), diabetic control (DC), and metformin-treated (300 mg/kg body weight/day) diabetic rats (D+Met). Diabetes was induced using a single intraperitoneal injection of streptozotocin (60 mg/kg b.w.), followed by oral treatment with metformin for four weeks.

RESULTS

Diabetes decreased serum and intratesticular testosterone levels and increased serum but not intratesticular levels of luteinizing hormone. Sperm count, motility, viability, and normal morphology were decreased, while sperm nuclear DNA fragmentation was increased in DC group, relative to NC group. Testicular mRNA levels of androgen receptor, luteinizing hormone receptor, cytochrome P450 enzyme (CYP11A1), steroidogenic acute regulatory (StAR) protein, 3β-hydroxysteroid dehydrogenase (HSD), and 17β-HSD, as well as the level of StAR protein and activities of CYP11A1, 3β-HSD, and 17β-HSD, were decreased in DC group. Similarly, decreased activities of epididymal antioxidant enzymes and increased lipid peroxidation were observed in DC group. Consequently, decreased litter size, fetal weight, mating and fertility indices, and increased pre- and post-implantation losses were recorded in DC group. Following intervention with metformin, we observed increases in serum and intratesticular testosterone levels, Leydig cell count, improved sperm parameters, and decreased sperm nuclear DNA fragmentation. Furthermore, mRNA levels and activities of steroidogenesis-related enzymes were increased, with improved fertility outcome.

DISCUSSION AND CONCLUSION

Diabetes mellitus is associated with dysregulation of steroidogenesis, abnormal spermatogenesis, and fertility decline. Controlling hyperglycemia is therefore crucial in preserving male reproductive function. Metformin not only regulates blood glucose level, but also preserves male fertility in diabetic state.

Glucose and glutamine handling in the Sertoli cells of transgenic rats overexpressing regucalcin: plasticity towards lactate production

Sertoli cells (SCs) possess the unparalleled ability to provide the germ line with growth factors and nutrients. Although SCs can oxidize amino acids, e.g., glutamine, they mostly metabolize glucose, producing high amounts of lactate, the germ cells preferential substrate. Regucalcin (RGN) is a calcium-binding protein that has been indicated as a regulator of cell metabolism. In this study, we investigated glucose and glutamine handling in the SCs of transgenic rats overexpressing RGN (Tg-RGN) comparatively with wild-type (Wt) littermates. Primary SCs isolated from adult Tg-RGN animals and maintained in culture for 24 hours, produced and exported more lactate, despite consuming less glucose. These observations were underpinned by increased expression of alanine transaminase, and augmented glutamine consumption, suggesting that alternative routes are contributing to the enhanced lactate production in the SCs of Tg-RGN rats. Moreover, lactate seems to be used by germ cells, with diminished apoptosis being detected in the seminiferous tubules of Tg-RGN animals cultured ex vivo. The obtained results showed a distinct metabolism in the SCs of Wt and Tg-RGN rats widening the roles assigned to RGN in spermatogenesis. These findings also highlighted the plasticity of SCs metabolism, a feature that would be exploited in the context of male infertility.

The hypothalamic neuropeptide orexin A- a possible regulator in glucose homeostasis and germ cell kinetics in adult mice testes

Orexin A (OXA), a hypothalamic neuropeptide, regulates food intake, sleep-wake cycle and energy balance by binding to its receptor (OX1R). Apart from brain, OXA and OX1R are also present in peripheral organs including reproductive tissues. Mammalian reproduction depends on uptake and proper utilization of glucose in the testes. This study, therefore, examined role of OXA/OX1R system in regulation of glucose homeostasis in adult mouse testis under in vivo and ex vivo conditions. Binding of OXA to OX1R was blocked using an OX1R antagonist, SB-334867. Mice were given a single bilateral intratesticular injection of the antagonist at doses of 4 and 12μg/mouse and sacrificed 24 h post-injection. In order to understand the direct role of OXA in testes of adult mice, an ex vivo experiment was performed where binding of OXA to OX1R in the testis was blocked by using the same OX1R antagonist. The antagonist treatment affected testicular glucose and lactate concentration with concomitant down-regulation in the expression of glucose transporters 3 and 8. A decreased activity in lactate dehydrogenase enzyme and imbalance between germ cell survival and proliferation were also noted in testes in treated mice. The results of ex vivo study supported the results obtained from in vivo study. The findings thus suggest involvement of OXA/OX1R system in regulation of testicular glucose homeostasis and germ cell kinetics in adult mice.