Intratesticular delivery of tumor necrosis factor-alpha and ceramide directly abrogates steroidogenic acute regulatory protein expression and Leydig cell steroidogenesis in adult rats

Gut microbiome-driven regulation of sex hormone homeostasis: a potential neuroendocrine connection

The gut microbiome is known to have a bidirectional relationship with sex hormone homeostasis; however, its role in mediating interactions between the primary regulatory axes of sex hormones and their productions is yet to be fully understood. We utilized both conventionally raised and gnotobiotic mouse models to investigate the regulatory role of the gut microbiome on the hypothalamic-pituitary-gonadal (HPG) axis. Male and female conventionally raised mice underwent surgical modifications as follows: (1) hormonally intact controls; (2) gonadectomized males and females; (3) gonadectomized males and females supplemented with testosterone and estrogen, respectively. Fecal samples from these mice were used to colonize sex-matched, intact, germ-free recipient mice through fecal microbiota transplant (FMT). Serum gonadotropins, gonadal sex hormones, cecal microbiota, and the serum global metabolome were assessed. FMT recipients of gonadectomized-associated microbiota showed lower circulating gonadotropin levels than recipients of intact-associated microbiota, opposite to that of FMT donors. FMT recipients of gonadectomized-associated microbiota also had greater testicular weights compared to recipients of intact-associated microbiota. The gut microbiota composition of recipient mice differed significantly based on the FMT received, with the male microbiota having a more concerted impact in response to changes in the HPG axis. Network analyses showed that multiple metabolically unrelated pathways may be involved in driving differences in serum metabolites due to sex and microbiome received in the recipient mice. In sum, our findings indicate that the gut microbiome responds to the HPG axis and subsequently modulates its feedback mechanisms. A deeper understanding of interactions between the gut microbiota and the neuroendocrine-gonadal system may contribute to the development of therapies for sexually dimorphic diseases.

Simultaneous deletion of ORMDL1 and ORMDL3 proteins disrupts immune cell homeostasis

ORMDL3 is a prominent member of a family of highly conserved endoplasmic reticulum resident proteins, ORMs (ORM1 and ORM2) in yeast, dORMDL in Drosophila and ORMDLs (ORMDL1, ORMDL2, and ORMDL3) in mammals. ORMDL3 mediates feedback inhibition of de novo sphingolipid synthesis. Expression levels of ORMDL3 are associated with the development of inflammatory and autoimmune diseases including asthma, systemic lupus erythematosus, type 1 diabetes mellitus and others. It has been shown that simultaneous deletions of other ORMDL family members could potentiate ORMDL3-induced phenotypes. To understand the complex function of ORMDL proteins in immunity in vivo, we analyzed mice with single or double deletions of Ormdl genes. In contrast to other single and double knockouts, simultaneous deletion of ORMDL1 and ORMDL3 proteins disrupted blood homeostasis and reduced immune cell content in peripheral blood and spleens of mice. The reduced number of splenocytes was not caused by aberrant immune cell homing. A competitive bone marrow transplantation assay showed that the development of Ormdl1-/-/Ormdl3-/- B cells was dependent on lymphocyte intrinsic factors. Highly increased sphingolipid production was observed in the spleens and bone marrow of Ormdl1-/-/Ormdl3-/- mice. Slight, yet significant, increase in some sphingolipid species was also observed in the spleens of Ormdl3-/- mice and in the bone marrow of both, Ormdl1-/- and Ormdl3-/- single knockout mice. Taken together, our results demonstrate that the physiological expression of ORMDL proteins is critical for the proper development and circulation of lymphocytes. We also show cell-type specific roles of individual ORMDL family members in the production of different sphingolipid species.

Role of sphingolipid metabolites in the homeostasis of steroid hormones and the maintenance of testicular functions

With the acceleration of life pace and the increase of work pressure, the problem of male infertility has become a social problem of general concern. Sphingolipids are important regulators of many cellular processes like cell differentiation and apoptosis, which are ubiquitously expressed in all mammalian cells. Various sphingolipid catabolic enzymes can generate multiple sphingolipids like sphingosine-1-phosphate and sphingomyelin. Present studies have already demonstrated the role of steroid hormones in the physiological processes of reproduction and development through hypothalamus-pituitary-gonad axis, while recent researches also found not only sphingolipids can modulate steroid hormone secretion, but also steroid hormones can control sphingolipid metabolites, indicating the role of sphingolipid metabolites in the homeostasis of steroid hormones. Furthermore, sphingolipid metabolites not only contribute to the regulation of gametogenesis, but also mediate damage-induced germ apoptosis, implying the role of sphingolipid metabolites in the maintenance of testicular functions. Together, sphingolipid metabolites are involved in impaired gonadal function and infertility in males, and further understanding of these bioactive sphingolipids will help us develop new therapeutics for male infertility in the future.

Functional metabolite reserves and lipid homeostasis revealed by the MA-10 Leydig cell metabolome

In Leydig cells, intrinsic factors that determine cellular steroidogenic efficiency is of functional interest to decipher and monitor pathophysiology in many contexts. Nevertheless, beyond basic regulation of cholesterol storage and mobilization, systems biology interpretation of the metabolite networks in steroidogenic function is deficient. To reconstruct and describe the different molecular systems regulating steroidogenesis, we profiled the metabolites in resting MA-10 Leydig cells. Our results identified 283-annotated components (82 neutral lipids, 154 membrane lipids, and 47 other metabolites). Neutral lipids were represented by an abundance of triacyglycerols (97.1%), and low levels of cholesterol esters (2.0%). Membrane lipids were represented by an abundance of glycerophospholipids (77.8%), followed by sphingolipids (22.2%). Acylcarnitines, nucleosides, amino acids and their derivatives were the other metabolite classes identified. Among nonlipid metabolites, we recognized substantial reserves of aspartic acid, choline, creatine, betaine, glutamine, homoserine, isoleucine, and pantothenic acid none of which have been previously considered as a requirement in steroidogenic function. Individually limiting use of betaine, choline, or pantothenic acid, during luteinizing hormone-induced steroidogenesis in MA-10 cells resulted in substantial decreases to acute steroidogenic capacity, explained by intermediary metabolite imbalances affecting homeostasis. As such, our dataset represents the current level of baseline characterization and unravels the functional resting state of steroidogenic MA-10 Leydig cells. In identifying metabolite stockpiles and causal mechanisms, these results serve to further comprehend the cellular setup and regulation of steroid biosynthesis.

Immune Cells as Critical Regulators of Steroidogenesis in the Testis and Beyond

Steroidogenesis is an essential biological process for embryonic development, reproduction, and adult health. While specific glandular cells, such as Leydig cells in the testis, are traditionally known to be the principal players in steroid hormone production, there are other cell types that contribute to the process of steroidogenesis. In particular, immune cells are often an important component of the cellular niche that is required for the production of steroid hormones. For several decades, studies have reported that testicular macrophages and Leydig cells are intimately associated and exhibit a dependency on the other cell type for their proper development; however, the mechanisms that underlie the functional relationship between macrophages and Leydig cells are unclear. Beyond the testis, in certain instances immune cells themselves, such as certain types of lymphocytes, are capable of steroid hormone production, thus highlighting the complexity and diversity that underlie steroidogenesis. In this review we will describe how immune cells are critical regulators of steroidogenesis in the testis and in extra-glandular locations, as well as discuss how this area of research offers opportunities to uncover new insights into steroid hormone production.

The role of lipid second messengers in aldosterone synthesis and secretion

Second messengers are small rapidly diffusing molecules or ions that relay signals between receptors and effector proteins to produce a physiological effect. Lipid messengers constitute one of the four major classes of second messengers. The hydrolysis of two main classes of lipids, glycerophospholipids and sphingolipids, generate parallel profiles of lipid second messengers: phosphatidic acid (PA), diacylglycerol (DAG), and lysophosphatidic acid versus ceramide, ceramide-1-phosphate, sphingosine, and sphingosine-1-phosphate, respectively. In this review, we examine the mechanisms by which these lipid second messengers modulate aldosterone production at multiple levels. Aldosterone is a mineralocorticoid hormone responsible for maintaining fluid volume, electrolyte balance, and blood pressure homeostasis. Primary aldosteronism is a frequent endocrine cause of secondary hypertension. A thorough understanding of the signaling events regulating aldosterone biosynthesis may lead to the identification of novel therapeutic targets. The cumulative evidence in this literature emphasizes the critical roles of PA, DAG, and sphingolipid metabolites in aldosterone synthesis and secretion. However, it also highlights the gaps in our knowledge, such as the preference for phospholipase D-generated PA or DAG, as well as the need for further investigation to elucidate the precise mechanisms by which these lipid second messengers regulate optimal aldosterone production.

Growth, puberty, and bone health in children and adolescents with inflammatory bowel disease

BACKGROUND

Endocrine complications such as impaired growth, delayed puberty, and low bone mineral density (BMD) can be associated with inflammatory bowel disease (IBD) in children and adolescents. This study was performed to investigate the frequency, characteristics, and outcomes of endocrine complications of IBD in children and adolescents.

METHODS

This study included 127 patients with IBD diagnosed before 18 years of age [117 with Crohn disease (CD) and 10 with ulcerative colitis (UC)]. Growth profiles, pubertal status, 25-hydroxyvitamin D₃ [25(OH)D₃] levels, and BMD were reviewed retrospectively.

RESULTS

Short stature was observed in 14 of 127 (11.0 %) with a mean height-SDS of -2.31 ± 0.72. During a 2-year follow-up period, height-SDS did not significantly improve, while weight-SDS significantly improved. Among 109 patients who were older than 13 (girls) or 14 (boys) years of age during the study period, 11 patients (10.1 %) showed delayed puberty, which was associated with low weight-SDS. Vitamin D deficiency was documented in 81.7 % (94/115) with the average 25(OH)D₃ level of 14.5 ± 7.0 ng/mL. Lumbar BMD Z-score was below - 2 SDS in 25 of 119 patients (21.0 %). Height-SDS, weight-SDS, and body mass index (BMI)-SDS were lower in patients with osteoporosis than those without osteoporosis. When pediatric CD activity index scores were high (≥ 30), weight-SDS, BMI-SDS, insulin-like growth factor 1 (IGF-1)-SDS, and testosterone levels were significantly decreased.

CONCLUSIONS

Vitamin D deficiency and osteoporosis are common in pediatric IBD patients. As disease severity deteriorates, weight-SDS, IGF-1-SDS, and testosterone levels were decreased. Optimal pubertal development is necessary for bone health.

Elevated CCL2 causes Leydig cell malfunction in metabolic syndrome

Metabolic syndrome (MetS), which is associated with chronic inflammation, predisposes males to hypogonadism and subfertility. The underlying mechanism of these pathologies remains poorly understood. Homozygous leptin-resistant obese db/db mice are characterized by small testes, low testicular testosterone, and a reduced number of Leydig cells. Here we report that IL-1β, CCL2 (also known as MCP-1), and corticosterone concentrations were increased in the testes of db/db mice relative to those in WT controls. Cultured murine and human Leydig cells responded to cytokine stress with increased CCL2 release and apoptotic signals. Chemical inhibition of CCL2 rescued Leydig cell function in vitro and in db/db mice. Consistently, we found that Ccl2-deficient mice fed with a high-energy diet were protected from testicular dysfunction compared with similarly fed WT mice. Finally, a cohort of infertile men with a history of MetS showed that reduction of CCL2 plasma levels could be achieved by weight loss and was clearly associated with recovery from hypogonadism. Taken together, we conclude that CCL2-mediated chronic inflammation is, to a large extent, responsible for the subfertility in MetS by causing damage to Leydig cells.

MCP-1/CCL2 upregulation associates with metabolic syndrome–induced male subfertility in both mice and men.

Oral glucose load and mixed meal feeding lowers testosterone levels in healthy eugonadal men

PURPOSE

Precise evaluation of serum testosterone levels is important in making an accurate diagnosis of androgen deficiency. Recent practice guidelines on male androgen deficiency recommend that testosterone be measured in the morning while fasting. Although there is ample evidence regarding morning measurement of testosterone, studies that evaluated the effect of glucose load or meals were limited by inclusion of hypogonadal or diabetic men, and measurement of testosterone was not performed using mass spectrometry.

METHODS

Sixty men (23-97 years) without pre-diabetes or diabetes who had normal total testosterone (TT) levels underwent either an oral glucose tolerance test (OGTT) or a mixed meal tolerance test (MMTT) after an overnight fast. Serum samples were collected before and at regular intervals for 2 h (OGTT cohort) or 3 h (MMTT cohort). TT was measured by LC-MS/MS. LH and prolactin were also measured.

RESULTS

TT decreased after a glucose load (mean drop at nadir = 100 ng/dL) and after a mixed meal (drop at nadir = 123 ng/dL). Approximately 11% of men undergoing OGTT and 56% undergoing MMTT experienced a transient decrease in TT below 300 ng/dL, the lower normal limit. Testosterone started declining 20 min into the tests, with average maximum decline at 60 min. Most men still had TT lower than baseline at 120 min. This effect was independent of changes in LH or prolactin.

CONCLUSION

A glucose load or a mixed meal transiently, but significantly, lowers TT levels in healthy, non-diabetic eugonadal men. These findings support the recommendations that measurement of serum testosterone to diagnose androgen deficiency should be performed while fasting.

The in vitro modulation of steroidogenesis by inflammatory cytokines and insulin in TM3 Leydig cells

BACKGROUND

Cytokines and hormones, including insulin, are known to modulate the hypothalamic-pituitary-testes axis and steroidogenesis, both centrally and peripherally. In the context of chronic inflammation and hyperinsulinaemia mediating male hypogonadism associated with obesity, metabolic syndrome and type 2 diabetes mellitus, these mechanisms are poorly understood and the impact of cytokines and insulin on Leydig cell steroidogenesis has not been fully elicited. This study aimed to further investigate the in vitro impact of TNFα, IL1ß, IL6, IL8 and insulin on Leydig cell function and steroidogenesis.

METHODS

hCG-stimulated TM3 Leydig cells were exposed to various concentrations of TNFα, IL1ß, IL6, IL8 (100 ng/ml, 10 ng/ml, 1 ng/ml and 0.1 ng/ml) and insulin (10 ng/ml, 1 ng/ml, 0.1 ng/ml and 0.01 ng/ml) in optimal cell culture conditions over 48 h. Cell viability (XTT) and testosterone and progesterone concentrations (ELISA) were assessed using standardised laboratory techniques.

RESULTS

TNFα significantly decreased cell viability and progesterone and testosterone concentrations in a dose-dependent relationship. IL1ß and IL6 had a subtle but significant negative effect on cell viability and testosterone concentrations, with a marked significant decrease in progesterone concentration at all concentrations investigated. IL8 showed an increase in cell viability, with no significant effect on testosterone concentrations alongside a significant decrease in progesterone concentrations. Insulin significantly increased cell viability and testosterone concentrations in a dose dependent relationship, but interestingly significantly decreased progesterone concentrations.

CONCLUSIONS

The inflammatory cytokines TNFα, IL1β and IL6 cause a dose dependent decline in steroidogenesis in TM3 Leydig cells. These results suggest that chronic inflammation may downregulate steroidogenesis in males via direct modulation of Leydig cell function. However, IL8 may stimulate TM3 Leydig cell growth. Insulin is associated with a dose-dependent increase in testosterone synthesis, with a significant decline in progesterone synthesis. With the phenomenon of insulin resistance, the literature is unclear on the potential role of hyperinsulinaemia in steroidogenesis. Further studies are warranted in order to fully elicit the molecular mechanisms and interactions of these molecules on male steroidogenesis.

Nano-sized titanium dioxide toxicity in rat prostate and testis: Possible ameliorative effect of morin

This study investigated the effect of short-term oral exposure to nano-sized titanium dioxide (nTiO2) on Wistar rat prostate and testis, and the associating reproductive-related alterations. The study also evaluated the potential ameliorative effect of the natural flavonoid, morin, on nTiO2-induced aberrations. Intragastric administration of nTiO2 (50mg/kg/day for 1, 2 and 3weeks) increased testicular gamma-glutamyltransferase (γ-GT) activity and decreased testicular steroidogenic acute regulatory protein (StAR) and c-kit gene expression, serum testosterone level and sperm count. nTiO2-treated rats also exhibited prostatic and testicular altered glutathione levels, elevated TNF-α levels, up-regulated Fas, Bax and caspase-3 gene expression, down-regulated Bcl-2 gene expression and enhanced prostatic lipid peroxidation. Sperm malformation and elevated testicular acid phosphatase (ACP) activity and malondialdehyde level, serum prostatic acid phosphatase activity, prostate specific antigen (PSA), gonadotrophin and estradiol levels occurred after the 2 and 3week regimens. Morin (30mg/kg/day administered intragastrically for 5weeks) mitigated nTiO2-induced prostatic and testicular injury as evidenced by lowering serum PSA level, testicular γ-GT and ACP activities and TNF-α level, along with hampering both intrinsic and extrinsic apoptotic pathways. Moreover, morin alleviated prostatic lipid peroxidation, raised prostatic glutathione level, and relieved testicular reductive stress. Additionally, morin increased testicular StAR and c-kit mRNA expression, raised the sperm count, reduced sperm deformities and modified the altered hormone profile. Histopathological evaluation supported the biochemical findings. In conclusion, morin could ameliorate nTiO2-induced prostatic and testicular injury and the corresponding reproductive-related aberrations via redox regulatory, anti-inflammatory and anti-apoptotic mechanisms, promoting steroidogenesis and spermatogenesis, and improving sperm count and morphology.

Cytokines in Endocrine Dysfunction of Plasma Cell Disorders

Monoclonal gammopathies (MG) are classically associated with lytic bone lesions, hypercalcemia, anemia, and renal insufficiency. However, in some cases, symptoms of endocrine dysfunction are more prominent than these classical signs and misdiagnosis can thus be possible. This concerns especially the situation where the presence of M-protein is limited and the serum protein electrophoresis (sPEP) appears normal. To understand the origin of the endocrine symptoms associated with MG, we overview here the current knowledge on the complexity of interactions between cytokines and the endocrine system in MG and discuss the perspectives for both the diagnosis and treatments for this class of diseases. We also illustrate the role of major cytokines and growth factors such as IL-6, IL-1β, TNF-α, and VEGF in the endocrine system, as these tumor-relevant signaling molecules not only help the clonal expansion and invasion of the tumor cells but also influence cellular metabolism through autocrine, paracrine, and endocrine mechanisms. We further discuss the broader impact of these tumor environment-derived molecules and proinflammatory state on systemic hormone signaling. The diagnostic challenges and clinical work-up are illustrated from the point of view of an endocrinologist.

Adipocyte accumulation in corpus cavernosum: First clinical evidence and pathophysiological implications in erectile dysfunction

OBJECTIVES

Animal models have shown that erectile dysfunction is associated with adipocyte accumulation under tunica albugínea, which could be involved in venous leakage and loss of penile rigidity. In the current sudy, we compared the histology of the penile sub-albuginean region of drug-refractory erectile dysfunction patients undergoing penile prosthesis implantation with potent patients with Peyronie's disease undergoing curvature correction procedures.

MATERIALS AND METHODS

Seventeen refractory erectile dysfunction patients and fourteen potent patients with Peyronie's disease were recruited. Sub-albuginean tissue samples were taken in each surgery. An expert uropathologist analysed each section. A bivariate analysis was performed. Multivariate logistic regression was used to calculate adjusted odds ratios; P value<.05 was considered significant.

RESULTS

Eleven patients (11/17) in the case group presented cavernous fat cell accumulation, while only one patient (1/14) in the control group presented this finding (P<.05). Adjusted odds ratio for erectile dysfunction was 40.72; 95% CI 2.28-727.29 (P=.012).

CONCLUSIONS

Different studies have shown that androgen disruption could be involved in penile structural changes, leading to trabecular smooth muscle apoptosis and trans or de-differentiation into adipocytes. This is the first prospective study in humans to report an association between erectile dysfunction and sub-albuginean adipocyte accumulation. Venous leakage secondary to this phenomenon could be a factor in the pathophysiology of erectile dysfunction, especially in patients that do not respond to medical therapy.

Prepubertal onset of obesity negatively impacts on testicular steroidogenesis in rats

Obesity is a global health problem and impacts negatively on levels of testosterone and quality of sperm production. At present little is known about mechanisms that attenuate testicular function in obese males. Our study characterized testicular steroidogenesis and explored levels of relevant paracrine and hormonal factors in rats with short- and long-term obesity. We have found that obesity state increased serum levels of estradiol and leptin in both groups of obese rats and inhibited the expression of StAR and Cyp11a1 associated with low levels of intratesticular testosterone in rats with long-term obesity. Further, long-term obesity reduced the number of Leydig cells, increased the testicular levels of the proinflammatory adipocytokine TNFα and the number of testicular macrophages. All together, our data indicate that long-term obesity may cause chronic inflammation in the testis and negatively impacts on Leydig cell steroidogenesis.

Proinflammatory Cytokine Infusion Attenuates LH's Feedforward on Testosterone Secretion: Modulation by Age

CONTEXT

In the experimental animal, inflammatory signals quench LH's feedforward drive of testosterone (T) secretion and appear to impair GnRH-LH output. The degree to which such suppressive effects operate in the human is not known.

OBJECTIVE

To test the hypothesis that IL-2 impairs LH's feedforward drive on T and T's feedback inhibition of LH secretion in healthy men.

SETTING

Mayo Center for Translational Science Activities.

PATIENTS OR OTHER PARTICIPANTS

A total of 35 healthy men, 17 young and 18 older.

INTERVENTIONS

Randomized prospective double-blind saline-controlled study of IL-2 infusion in 2 doses with concurrent 10-minute blood sampling for 24 hours.

MAIN OUTCOME MEASURES

Deconvolution analysis of LH and T secretion.

RESULTS

After saline injection, older compared with young men exhibited reduced LH feedforward drive on T secretion (P < .001), and decreased T feedback inhibition of LH secretion (P < .01). After IL-2 injection, LH's feedforward onto T secretion declined markedly especially in young subjects (P < .001). Concomitantly, IL-2 potentiated T's proportional feedback on LH secretion especially in older volunteers.

CONCLUSION

This investigation confirms combined feedforward and feedback deficits in older relative to young men given saline and demonstrates 1) joint mechanisms by which IL-2 enforces biochemical hypogonadism, viz, combined feedforward block and feedback amplification; and 2) unequal absolute inhibition of T and LH secretion by IL-2 in young and older men. These outcomes establish that the male gonadal axis is susceptible to dual-site suppression by a prototypic inflammatory mediator. Thus, we postulate that selected ILs might also enforce male hypogonadism in chronic systemic inflammation.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

A prospective longitudinal study of growth and pubertal progress in adolescents with inflammatory bowel disease

BACKGROUND

Puberty and growth may be affected in inflammatory bowel disease (IBD) but the extent is unclear.

METHODS

We performed a prospective study over 12 months in 63 adolescents (Crohn's disease, CD, n = 45; ulcerative colitis/IBD unclassified, UC, n = 18) with a median age of 13.4 years (range 10-16.6). Assessment included anthropometry, biochemical markers of growth and puberty and an assessment of quality of life by IMPACT-III.

RESULTS

Compared to the normal population, boys with CD were shorter, with a median height SDS (HtSDS) of -0.13 (-2.52 to 1.58; p < 0.05). In addition, the study cohort had a lower median IGF-1 SDS of -0.29 (-4.53 to 2.96; p = 0.008) and a higher median IGFBP3 SDS of 0.45 (-3.15 to 2.55; p = 0.002). Over the study period, the median Ht velocity (HV) was 5 cm/year (0.2-8.7) and the change in HtSDS was 0.06 (-0.48 to 0.57). The median difference between the chronological and bone age was 0.3 years (-2.5 to 3.0) and pubertal examination was not delayed. In the whole group, the erythrocyte sedimentation rate (ESR) showed an inverse association with HV (r = -0.29; p = 0.025) and IGF-1:IGFBP3 (r = -0.34; p = 0.016). The score in the body image domain, IMPACT-III, was inversely associated with HtSDS (r = -0.31; p = 0.03).

CONCLUSION

Despite no evidence of pubertal delay, adolescents with IBD display growth retardation which may be associated with raised ESR, adverse quality of life measures and an abnormality of IGF-1 bioavailability.

Determinants of testosterone levels in human male obesity

Testosterone (T) levels are decreased in obese men, but the underlying causes are incompletely understood. Our objective was to explore the relation between low (free) T levels and male obesity, by evaluating metabolic parameters, subcutaneous adipose tissue (SAT) aromatase expression, and parameters of the hypothalamic-pituitary-gonadal axis. We recruited 57 morbidly obese men [33 had type 2 diabetes (DM2)] and 25 normal-weight men undergoing abdominal surgery. Fourteen obese men also attended a follow-up, 2 years after gastric bypass surgery (GBS). Circulating T levels were quantified by LC-MS/MS, whereas free T levels were measured using serum equilibrium dialysis and sex hormone-binding globulin, luteinizing hormone, and follicle-stimulating hormone by immunoassay. SAT biopsies were used to determine adipocyte cell size and aromatase expression by real-time PCR. Total and free T levels were decreased in obese males versus controls, with a further decrease in obese men with DM2 versus obese men without DM2. There were no differences in aromatase expression among the study groups, and sex steroids did not correlate with aromatase expression. Pearson analysis revealed an inverse association between (free) T and SAT cell size, triglycerides, and HOMA-IR. Multivariate analysis confirmed the inverse association between (free) T and SAT cell size (β = -0.321, P = 0.037 and β = -0.441, P = 0.011, respectively), independent of age, triglycerides, HOMA-IR, obesity, or diabetes. T levels were normalized 2 years after GBS. These data suggest that SAT cell size rather than SAT aromatase expression or parameters of the hypothalamic-pituitary-gonadal axis is related to low T in male obesity, which points to adipose cell size-related metabolic changes as a major trigger in decreased T levels.

Nigerian bonny-light crude oil induces alteration in testicular stress response proteins and caspase-3 dependent apoptosis in albino wistar rats

In the past few decades, there has been much concern about the adverse health effects of environmental contaminants in general and Crude Oil in particular around the Niger Delta region of Nigeria where all the crude Oil exploration is taking place. Studies have shown the repro-toxic effects of Bonny-light crude oil (BLCO). However, the insight into the mechanisms of gonadal toxicity induced by BLCO is not well known. In this study, we sought to elucidate the mechanism(s) underpinning the gonadal effects within hours of exposure to BLCO. Experimental rats were divided into five groups of four each. Animals were orally administered with a single dose of BLCO (800 mg/kg body weight) and killed at 0, 6, 12, 24, and 72 h post-treatment. The levels and time-course of induction of stress response proteins and apoptosis-related proteins like cytochorome C, caspase 3 and procaspase 9, Fas-FasL, NF-kB and TNF-α were determined to assess sequential induction of apoptosis in the rat testis. DNA damage was assessed by TUNEL assay. Administration of BLCO resulted in a significant increase in the levels of stress response proteins and apoptotis- related proteins as early as 6 h following exposure. Time-dependent elevations in the levels of the proteins were observed. The DNA damage was measured and showed time-dependent increase in the TUNEL positive cells of testicular cells. The study demonstrates induction of testicular apoptosis in adult rats following exposure to a single dose of BLCO.

Pathway based analysis of genes and interactions influencing porcine testis samples from boars with divergent androstenone content in back fat

One of the primary factors contributing to boar taint is the level of androstenone in porcine adipose tissues. A majority of the studies performed to identify candidate biomarkers for the synthesis of androstenone in testis tissues follow a reductionist approach, identifying and studying the effect of biomarkers individually. Although these studies provide detailed information on individual biomarkers, a global picture of changes in metabolic pathways that lead to the difference in androstenone synthesis is still missing. The aim of this work was to identify major pathways and interactions influencing steroid hormone synthesis and androstenone biosynthesis using an integrative approach to provide a bird's eye view of the factors causing difference in steroidogenesis and androstenone biosynthesis. For this purpose, we followed an analysis procedure merging together gene expression data from boars with divergent levels of androstenone and pathway mapping and interaction network retrieved from KEGG database. The interaction networks were weighted with Pearson correlation coefficients calculated from gene expression data and significant interactions and enriched pathways were identified based on these networks. The results show that 1,023 interactions were significant for high and low androstenone animals and that a total of 92 pathways were enriched for significant interactions. Although published articles show that a number of these enriched pathways were activated as a result of downstream signaling of steroid hormones, we speculate that the significant interactions in pathways such as glutathione metabolism, sphingolipid metabolism, fatty acid metabolism and significant interactions in cAMP-PKA/PKC signaling might be the key factors determining the difference in steroidogenesis and androstenone biosynthesis between boars with divergent androstenone levels in our study. The results and assumptions presented in this study are from an in-silico analysis done at the gene expression level and further laboratory experiments at genomic, proteomic or metabolomic level are necessary to validate these findings.

Endocrine therapy for growth retardation in paediatric inflammatory bowel disease

Inflammatory bowel disease, particularly Crohn's disease (CD), can potentially cause growth failure during childhood as well as a reduction in final adult height. The underlying mechanism is multifactorial and includes poor nutrition, chronic inflammation, and the prolonged use of steroids. Despite major advances in the treatment of CD, current cohorts of children continue to display a deficit in linear growth and may qualify for growth-promoting hormonal therapy. However, currently there is limited evidence to support the use of endocrine therapy directed primarily at improving growth. This review is aimed at summarising the current evidence for growth impairment in inflammatory bowel disease and discusses the rationale for using growth promoting therapy.

Acid ceramidase (ASAH1) is a global regulator of steroidogenic capacity and adrenocortical gene expression

In H295R human adrenocortical cells, ACTH rapidly activates ceramide (Cer) and sphingosine (SPH) turnover with a concomitant increase in SPH-1-phosphate secretion. These bioactive lipids modulate adrenocortical steroidogenesis, primarily by acting as second messengers in the protein kinase A/cAMP-dependent pathway. Acid ceramidase (ASAH1) directly regulates the intracellular balance of Cer, SPH, and SPH-1-phosphate by catalyzing the hydrolysis of Cer into SPH. ACTH/cAMP signaling stimulates ASAH1 transcription and activity, supporting a role for this enzyme in glucocorticoid production. Here, the role of ASAH1 in regulating steroidogenic capacity was examined using a tetracycline-inducible ASAH1 short hairpin RNA H295R human adrenocortical stable cell line. We show that ASAH1 suppression increases the transcription of multiple steroidogenic genes, including Cytochrome P450 monooxygenase (CYP)17A1, CYP11B1/2, CYP21A2, steroidogenic acute regulatory protein, hormone-sensitive lipase, 18-kDa translocator protein, and the melanocortin-2 receptor. Induced gene expression positively correlated with enhanced histone H3 acetylation at target promoters. Repression of ASAH1 expression also induced the expression of members of the nuclear receptor nuclear receptor subfamily 4 (NR4A) family while concomitantly suppressing the expression of dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1. ASAH1 knockdown altered the expression of genes involved in sphingolipid metabolism and changed the cellular amounts of distinct sphingolipid species. Finally, ASAH1 silencing increased basal and cAMP-dependent cortisol and dehydroepiandrosterone secretion, establishing ASAH1 as a pivotal regulator of steroidogenic capacity in the human adrenal cortex.

Hypogonadism and metabolic syndrome

BACKGROUND

The relationship between metabolic syndrome (MetS), male hypogonadism and their possible interaction in cardiovascular (CV) risk stratification are not completely understood.

AIM

We reviewed relationships between testosterone (T) and MetS emphasizing their possible interaction in the pathogenesis of CV diseases.

MATERIALS AND METHODS

A systematic search of published evidence was performed using Medline (1969 to January 2011).

RESULTS

Cross-sectional data have shown that subjects with MetS have lower levels of total T (TT) (about 3 nmol/l), as hypogonadism is more evident in subjects with than in those without erectile dysfunction (ED) than in those without. Longitudinal evidence shows that low T is allocated with a higher risk of subsequent development of MetS, although the reverse condition is also possible. Which are the factors in MetS responsible for the low T is not completely clarified. In clinical studies, increased waist circumference is the major determinant of MetS-associated hypogonadism. Our experiments in rabbits do not support the idea that visceral fat is the main determinant of MetS-associated male hypogonadism. Only few randomized clinical trials have evaluated the impact of T replacement therapy (TRT) in patients with MetS. Available evidence suggests that TRT decreases visceral fat accumulation and ameliorates insulin sensitivity, whereas androgen deprivation increases abdominal adiposity.

CONCLUSIONS

The clinical significance of the MetS-associated hypogonadism needs further clarifications. In particular, it has not been completely clarified if low T might be considered a cause or a consequence of MetS. The benefit of TRT in term of the reduction of CV risk needs to be confirmed in larger and longer studies.

Ceramide-mediated insulin resistance and impairment of cognitive-motor functions

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) are associated with cognitive impairment, brain insulin resistance, and neurodegeneration. Recent studies linked these effects to increased pro-ceramide gene expression in liver and increased ceramide levels in serum. Since ceramides are neurotoxic and cause insulin resistance, we directly examined the role of ceramides as mediators of impaired signaling and central nervous system function using an in vivo model. Long Evans rat pups were administered C2Cer:N-acetylsphinganine or its inactive dihydroceramide analog (C2DCer) by i.p. injection. Rats were subjected to rotarod and Morris water maze tests of motor and cognitive function, and livers and brains were examined for histopathology and integrity of insulin/IGF signaling. C2Cer treatment caused hyperglycemia, hyperlipidemia, and mild steatohepatitis, reduced brain lipid content, and increased ceramide levels in liver, brain, and serum. Quantitative RT-PCR analysis revealed significant alterations in expression of several genes needed for insulin and IGF-I signaling, and multiplex ELISAs demonstrated inhibition of signaling through the insulin or IGF-1 receptors, IRS-1, and Akt in both liver and brain. Ultimately, the toxic ceramides generated in peripheral sources such as liver or adipose tissue caused sustained impairments in neuro-cognitive function and insulin/IGF signaling needed for neuronal survival, plasticity, and myelin maintenance in the brain. These findings support our hypothesis that a liver/peripheral tissue-brain axis of neurodegeneration, effectuated by increased toxic lipid/ceramide production and transport across the blood-brain barrier, could mediate cognitive impairment in T2DM and NASH.

The interplay between bioactive sphingolipids and steroid hormones

Steroid hormones regulate various physiological processes including development, reproduction, and metabolism. These regulatory molecules are synthesized from cholesterol in endocrine organs - such as the adrenal glands and gonads - via a multi-step enzymatic process that is catalyzed by the cytochrome P450 superfamily of monooxygenases and hydroxysteroid dehydrogenases. Steroidogenesis is induced by trophic peptide hormones primarily via the activation of a cAMP/protein kinase A (PKA)-dependent pathway. However, other signaling molecules, including cytokines and growth factors, control the steroid hormone biosynthetic pathway. More recently, sphingolipids, including ceramide, sphingosine-1-phosphate, and sphingosine, have been found to modulate steroid hormone secretion at multiple levels. In this review, we provide a brief overview of the mechanisms by which sphingolipids regulate steroidogenesis. In addition, we discuss how steroid hormones control sphingolipid metabolism. Finally, we outline evidence supporting the emerging role of bioactive sphingolipids in various nuclear processes and discuss a role for nuclear sphingolipid metabolism in the control of gene transcription.

Cytokines and junction restructuring events during spermatogenesis in the testis: an emerging concept of regulation

During spermatogenesis in mammalian testes, junction restructuring takes place at the Sertoli-Sertoli and Sertoli-germ cell interface, which is coupled with germ cell development, such as cell cycle progression, and translocation of the germ cell within the seminiferous epithelium. In the rat testis, restructuring of the blood-testis barrier (BTB) formed between Sertoli cells near the basement membrane and disruption of the apical ectoplasmic specialization (apical ES) between Sertoli cells and fully developed spermatids (spermatozoa) at the luminal edge of the seminiferous epithelium occur concurrently at stage VIII of the seminiferous epithelial cycle of spermatogenesis. These two processes are essential for the translocation of primary spermatocytes from the basal to the apical compartment to prepare for meiosis, and the release of spermatozoa into the lumen of the seminiferous epithelium at spermiation, respectively. Cytokines, such as TNFalpha and TGFbeta3, are present at high levels in the microenvironment of the epithelium at this stage of the epithelial cycle. Since these cytokines were shown to disrupt the BTB integrity and germ cell adhesion, it was proposed that some cytokines released from germ cells, particularly primary spermatocytes, and Sertoli cells, would induce restructuring of the BTB and apical ES at stage VIII of the seminiferous epithelial cycle. In this review, the intricate role of cytokines and testosterone to regulate the transit of primary spermatocytes at the BTB and spermiation will be discussed. Possible regulators that mediate cytokine-induced junction restructuring, including gap junction and extracellular matrix, and the role of testosterone on junction dynamics in the testis will also be discussed.

The cAMP-responsive element binding protein (CREB) regulates the expression of acid ceramidase (ASAH1) in H295R human adrenocortical cells

Acid ceramidase (encoded by ASAH1) is a lipid hydrolase that catalyzes the conversion of ceramide (cer) into sphingosine (SPH) and a free fatty acid. Adrenocortical steroidogenesis is regulated by the trophic peptide hormone adrenocorticotropin (ACTH), which induces the expression of steroidogenic genes in the human adrenal cortex primarily via a cAMP/protein kinase A (PKA)-dependent pathway. ACTH also stimulates sphingolipid metabolism in H295R adrenocortical cells leading to changes in steroidogenic gene expression. Based on our previous data identifying SPH as an antagonist for the nuclear receptor steroidogenic factor 1 (SF-1) and the role of ACTH-stimulated changes in sphingolipid metabolism on steroidogenic gene transcription, the aim of the current study was to determine the role of ACTH signaling in regulating the expression of the ASAH1 gene in H295R cells. We show that activation of the ACTH signaling pathway induces ASAH1 gene expression by stimulating the binding of the cAMP-responsive element binding protein (CREB) to multiple regions of the ASAH1 promoter. CREB binding promotes the recruitment of the coactivators CREB binding protein (CBP) and p300 to the CREB-responsive regions of the promoter. Consistent with transcriptional activation, we show that cAMP signaling increases the trimethylation of Lys 4 on histone H3 (H3K4) along the ASAH1 promoter. Finally, RNA interference (RNAi) experiments demonstrate that CREB is indispensable for cAMP-induced ASAH1 transcription. These data identify the ACTH/cAMP signaling pathway and CREB as transcriptional regulators of the ASAH1 gene in the human adrenal cortex.

Inflammatory networks in the control of spermatogenesis : chronic inflammation in an immunologically privileged tissue?

Spermatogenesis is a complex, organized process involving intimate interactions between the developing germ cells and supporting Sertoli cells. The process is also highly regulated. Studies suggest that regulation in the seminiferous epithelium involves molecules normally associated with either immune or inflammatory processes; in particular, interleukin 1a (IL1a), IL6, tumor necrosis factor (TNFa), activin A and nitric oxide (NO). While there is considerable evidence that these inflammatory mediators have effects on spermatogonial and spermatocyte development as well as critical supportive functions of the Sertoli cells, which are undoubtedly of considerable importance during testicular inflammation, there remains some skepticism regarding the significance of these molecules with respect to normal testicular function. Nonetheless, it is evident that expression of these regulators varies across the cycle of the seminiferous epithelium in a consistent manner, with major changes in production coinciding with key events within the cycle. This review summarizes the evidence supporting the hypothesis that inflammatory cytokines play a role in normal testicular spermatogenesis, as well as in the etiology of inflammation induced sub-fertility. The balance of data leads to the striking conclusion that the cycle of the seminiferous epithelium resembles a chronic inflammatory event. This appears to be a somewhat paradoxical assertion, since the testis is an immunologically privileged tissue based on its well-established ability to support grafts with minimal rejection responses. However, it may be argued that local immunoregulatory mechanisms, which confer protection from immunity on both transplanted tissues and the developing spermatogenic cells, are equally necessary to prevent local inflammation responses associated with the spermatogenic process from activating the adaptive immune response.

TNF alpha-mediated disruption of spermatogenesis in response to Sertoli cell injury in rodents is partially regulated by MMP2

Mono-(2-ethylhexyl) phthalate (MEHP)-induced Sertoli cell injury in peripubertal rodents results in the stimulation of germ cell apoptosis through an interaction of FAS/FASL between these two cell types. During this peripubertal period, an early spike in the incidence of germ cell apoptosis occurs during the first wave of spermatogenesis and is essential for the development of functional spermatogenesis in adults. Our previous observations revealed that soluble tumor necrosis factor alpha (sTNFA) released by germ cells after MEHP exposure consequently resulted in a robust induction of FASL by Sertoli cells. Metalloproteinases (MPs) are essential for processing the TNFA precursor to its soluble form and its ability to bind to TNFRSF1A. The activity of MPs is regulated by the tissue inhibitors of MPs (TIMPs) family. Herein we report that TIMP2 is predominately expressed in Sertoli cells and that protein levels decrease in a time-dependent manner after MEHP exposure. The secretion of matrix MP 2 (MMP2) in primary rat Sertoli cell-germ cell cocultures is induced after MEHP exposure, and its activity increases in a time-dependent manner. The addition of SB-3CT, a specific gelatinase inhibitor, decreases the activity of MMP2 and significantly reduces MEHP-enhanced sTNFA production in primary cocultures. In vivo challenges with SB-3CT decrease sTNFA and reduce MEHP-induced testicular germ cell apoptosis. In primary cocultures, MEHP exposure causes a 9.46-fold increase in sTNFA, while the addition of recombinant MMP2 protein results in a 5.4-fold increase in sTNFA, suggesting that MEHP-induced MMP2 is in part responsible for the activation of TNFA in the testis. Taken together, these observations indicate the distinct role of specific MPs in response to toxicant-induced Sertoli cell injury, providing further insights into the mechanism by which Sertoli cells control the sensitivity of germ cells to undergo apoptosis.

Endocrine dysfunction in leprosy

Leprosy is still an endemic disease, especially in Third World countries, and, because of migration, it still persists in Europe and the United States. The disease affects the peripheral nerves, skin, and multiple internal organs, making its clinical recognition difficult. In particular, the endocrine manifestations caused by leprosy have been underestimated, even by specialists. The endocrine changes present in leprosy include hypogonadism, sterility, and osteoporosis. In addition, the spectral immune nature of leprosy offers an attractive model to investigate the pathogenetic correlation between the patterns of inflammation in the poles of its spectrum and the hormonal disarrangements observed in this disease. It is important that those involved in leprosy management be aware of the potential endocrine changes and their treatment to address the disease in all of its aspects. In this article, we review the findings on endocrine dysfunction in leprosy, including a survey of the literature and of our own work.

Multiple roles for sphingolipids in steroid hormone biosynthesis

Steroid hormones are essential regulators of a vast number of physiological processes. The biosynthesis of these chemical messengers occurs in specialized steroidogenic tissues via a multi-step process that is catalyzed by members of the cytochrome P450 superfamily of monooxygenases and hydroxysteroid dehydrogenases. Though numerous signaling mediators, including cytokines and growth factors control steroidogenesis, trophic peptide hormones are the primary regulators of steroid hormone production. These peptide hormones activate a cAMP/cAMP-dependent kinase (PKA) signaling pathway, however, studies have shown that crosstalk between multiple signal transduction pathways and signaling molecules modulates optimal steroidogenic capacity. Sphingolipids such as ceramide, sphingosine, sphingosine-1-phosphate, sphingomyelin, and gangliosides have been shown to control the steroid hormone biosynthetic pathway at multiple levels, including regulating steroidogenic gene expression and activity as well as acting as second messengers in signaling cascades. In this review, we provide an overview of recent studies that have investigated the role of sphingolipids in adrenal, gonadal, and neural steroidogenesis.

Transcriptional regulation of FasL expression and participation of sTNF-alpha in response to sertoli cell injury

The Fas/FasL signaling pathway has previously been demonstrated to be critical for triggering germ cell apoptosis in response to mono-(2-ethylhexyl)phthalate (MEHP)-induced Sertoli cell injury. Although Sertoli cells ubiquitously express the FasL protein, MEHP-induced germ cell apoptosis appears to tightly correlate with increased levels of Sertoli cell FasL. Here we characterize the transcriptional regulation of the murine FasL gene in Sertoli cells after MEHP exposure. A serial deletion strategy for 1.5 kb of the 5'-upstream activating sequence of the FasL promoter was used to determine transcriptional activity in response to MEHP. Luciferase activity of the FasL promoter in the rat Sertoli cell line ASC-17D revealed that two regions, -500 to -324 and -1250 to -1000, were necessary to drive the inducible transcription of FasL. Sequence analysis of these two regions revealed two cis-regulatory elements, NF-kappaB and Sp-1. By site-directed mutagenesis, electrophoretic mobility shift and chromatin immunoprecipitation assays, it was confirmed that MEHP-induced FasL expression is enhanced through the transcriptional regulation of both NF-kappaB and Sp-1. Experiments performed both in vitro and in vivo revealed that MEHP exposure results in an increased production of sTNF-alpha and that sTNF-alpha-mediated NF-kappaB activation causes robust increases in FasL levels in both the ASC-17D Sertoli cell line and in primary rat Sertoli cell/germ cell co-cultures. In the seminiferous epithelium, Sertoli cells express TNFR1, whereas germ cells produce TNF-alpha. Therefore, sTNF-alpha released by germ cells after MEHP-induced Sertoli cell injury acts upon Sertoli cell TNFR1 and activates NF-kappaB and Sp-1 that consequently causes a robust induction of FasL expression. These novel findings point to a potential "feed-forward" signaling mechanism by which germ cells prompt Sertoli cells to trigger their apoptotic elimination.

Pituitary-gonadal hormones and interleukin patterns in leprosy

The functional status of pituitary-gonadal hormones and their relationship to the pattern of inflammatory cytokines in the lepromatous (LL/BL) and tuberculoid (TT/BT) poles of leprosy were investigated. Gonadotropins [luteinizing hormone (LH) and follicle-stimulating hormone (FSH)], interleukin (IL)-1beta, IL-6, tumour necrosis factor (TNF)-alpha and C-reactive protein (CRP) concentrations and erythrocyte sedimentation rate (ESR) were significantly higher in LL/BL leprosy patients than in controls and were not different from controls in TT/BT patients. LH and FSH were positively correlated with IL-1beta, IL-6 and TNF-alpha, and CRP concentrations and ESR. Testosterone plasma levels were significantly decreased in LL/BL patients and not different in TT/BT patients compared with controls. In addition, testosterone levels were inversely correlated with IL-6 and TNF-alpha. Prolactin plasma levels of both LL/BL and TT/BT patients were not different when compared with those of controls. There was a significant positive correlation between IL-6 and TNF-alpha plasma levels and ESR and CRP concentrations. IL-1beta was positively correlated with ESR but not with CRP. The significant correlations between gonadotropins and testosterone and cytokines in leprosy patients suggest that cytokines may have a direct influence at testicular level and may be of pathogenetic significance in leprosy and in other inflammatory states involving reproductive dysfunction.

Cytokines and junction restructuring during spermatogenesis—a lesson to learn from the testis

In the mammalian testis, preleptotene and leptotene spermatocytes residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) at late stage VIII through early stage IX of the epithelial cycle during spermatogenesis, entering the adluminal compartment for further development. However, until recently the regulatory mechanisms that regulate BTB dynamics remained largely unknown. We provide a critical review regarding the significance of cytokines in regulating the 'opening' and 'closing' of the BTB. We also discuss how cytokines may be working in concert with adaptors that selectively govern the downstream signaling pathways. This process, in turn, regulates the dynamics of either Sertoli-Sertoli tight junction (TJ), Sertoli-germ cell adherens junction (AJ), or both junction types in the epithelium, thereby permitting TJ opening without compromising AJs, and vice versa. We also discuss how adaptors alter their protein-protein association with the integral membrane proteins at the cell-cell interface via changes in their phosphorylation status, thereby altering adhesion function at AJ. These findings illustrate that the testis is a novel in vivo model to study the biology of junction restructuring. Furthermore, a molecular model is presented regarding how cytokines selectively regulate TJ/AJ restructuring in the epithelium during spermatogenesis.

Ghrelin inhibits the proliferative activity of immature Leydig cells in vivo and regulates stem cell factor messenger ribonucleic acid expression in rat testis

Ghrelin has emerged as putative regulator of an array of endocrine and nonendocrine functions, including cell proliferation. Recently, we provided evidence for the expression of ghrelin in mature, but not in undifferentiated, Leydig cells of rat and human testis. Yet testicular actions of ghrelin, other than modulation of testosterone secretion, remain unexplored. In the present study we evaluated the effects of ghrelin on proliferation of Leydig cell precursors during puberty and after selective elimination of mature Leydig cells by treatment with ethylene dimethane sulfonate. In these settings, intratesticular injection of ghrelin significantly decreased the proliferative activity of differentiating immature Leydig cells, estimated by 5-bromodeoxyuridine labeling. This response was selective and associated, in ethylene dimethane sulfonate-treated animals, with a decrease in the mRNA levels of stem cell factor (SCF), i.e. a key signal in spermatogenesis and a putative regulator of Leydig cell development. Thus, the effects of ghrelin on SCF gene expression were evaluated. In adult rats, ghrelin induced a significant decrease in SCF mRNA levels in vivo. Such an inhibitory action was also detected in vitro using cultures of staged seminiferous tubules. The inhibitory effect of ghrelin in vivo was dependent on proper FSH input, because it was detected in hypophysectomized rats only after FSH replacement. Overall, it is proposed that acquisition of ghrelin expression by Leydig cell precursors during differentiation may operate as a self-regulatory signal for the inhibition of the proliferative activity of this cell type through direct or indirect (i.e. SCF-mediated) mechanisms. In addition, we present novel evidence for the ability of ghrelin to modulate the expression of the SCF gene, which may have implications for the mode of action of this molecule in the testis as well as in other physiological systems.