Biological role and clinical significance of insulin-like peptide 3

Relationship between semen parameters, serum InhB, and INSL-3 levels, and the degree of varicocele

BACKGROUND

Varicocele is an abnormal expansion of the pampininias venous plexus in the scrotum, resulting in impaired sperm production and reduced sperm quality. The exact pathophysiological mechanism leading to varicocele-related infertility has not been fully elucidated. Although treatable, varicocele may lead to male infertility.

OBJECTIVE

To investigate the relationship between semen parameters, serum InhB and INSL-3 levels, and the degree of varicocele in male patients.

METHODS

Serum InhB and INSL-3 were detected. To evaluate the relationship between semen parameters and serum InhB and INSL-3 levels. To evaluate the value of semen parameters and serum InhB and INSL-3 levels in distinguishing disease severity in patients with varicocele.

RESULTS

Serum INSL-3 in patients with varicocele decreased with the severity of the disease. Serum INSL-3 was positively correlated with total sperm count and frequency of normal sperm morphology. There was a weak correlation between serum InhB and semen volume, concentration, and total sperm. Patients with different disease severity were similar within the groups, with partial overlap or similarity between varicocele Grade I and Grade II, and significant differences between Grade III and Grade I and II. Semen volume, concentration, total sperm, normal sperm morphology, and serum InhB and INSL-3 levels could distinguish the degree of varicocele.

CONCLUSION

Semen parameters and the combination of serum InhB and INSL-3 levels in patients with varicocele are closely related to the severity of the disease. Serum INSL-3 is expected to be a potential biomarker for early clinical intervention.

Distribution of extracellular matrix related proteins in normal and cryptorchid ziwuling black goat testes

The Ziwuling black goat is an indigenously in China, their offspring are frequently affected by congenital cryptorchidism. The extracellular matrix (ECM) contains cytokines and growth factors that regulate the development of the testis, and component changes often result in pathological changes. Cryptorchidism is closely related to structural changes in ECM. In this study, the histochemical staining, immunohistochemical, immunofluorescence and Western blot combined with semi-quantitative analysis was used to describe the distribution of the important ECM components Collagen type IV (Col IV), laminin (LN)and heparan sulfate proteoglycans (HSPG) in the normal and cryptorchid testes of Ziwuling black goats. Results showed that: The histochemical staining showed that the dysplasia of seminiferous tubules and decreased number of Sertoli cells in cryptorchidism, as well as sparse collagen fiber. Meanwhile, the distribution of reticular fibers is relatively rich. Furthermore, the PAS and AB staining in the interstitial vessels and lamina propria of seminiferous tubules is weak. The immunohistochemical and immunofluorescence revealed that Col IV, LN was strongly expressed in Leydig, Sertoli cells of normal testes and moderately positive in the spermatogonia and spermatids, but HSPG was not expressed in the spermatogonia. However, cryptorchidism, the expression of Col IV, LN and HPSG in Leydig, Sertoli cells significantly decreased, as well as the expression of Col IV and LN in capillary endothelial cells, but HSPG was moderately expressed in spermatogonia. Based on these data, the underdevelopment of spermatogenic epithelium, decreased synthesis function of collagen fibers and Leydig cells develop usually in the cryptorchidism were shown to be closely related to the abnormal metabolism of Col IV and LN. The positive expressed of HSPG in the spermatogonia of cryptorchid testes is related to the compensatory development of spermatogonia.

Role of JNK, TGF-β1, Akt, IL-1β and INSL-3 in proanthocyanidin protection against apoptosis in diabetic rat testis

We investigated how proanthocyanidin treatment altered c-Jun N-terminal kinases, transforming growth factor beta 1, serine/threonine-specific protein kinase, interleukin 1 beta and insulin-like 3 expression in the testis of diabetic rats. We used 24 Wistar albino male rats divided into four groups. Group 1 was untreated control. Group 2 was treated with 40 mg/kg streptozotocin (STZ) for 5 days. Group 3 was treated with 40 mg/kg STZ + 250 mg/kg proanthocyanidin once daily for six weeks. Group 4 was treated with 40 mg/kg STZ + 250 mg/kg proanthocyanidin. Superoxide dismutase activity was reduced in groups 3 and 4 compared to group 2. Glutathione peroxidase activity was increased significantly in groups 3 and 4 compared to groups 1 and 2. Catalase activity was decreased in group 4 compared to group 2. We found that proanthocyanidin increased cell proliferation in diabetic testis. Phospho-JNK and TGF-β1 immunostaining was decreased groups 3 and 4 compared to group 2, while p-Akt immunostaining was increased in groups 3 and 4. The number of IL-1β immunostained cells in groups 3 and 4 was decreased compared to group 2. INSL-3 immunostaining was increased significantly in group 3 compared to group 2. Our findings indicate that proanthocyanidin ameliorated diabetes related testicular dysfunction. Proanthocyanidin contributes to a balanced oxidant-antioxidant status, and balanced proliferation and apoptosis activity in the germinal cells.

Triadimefon increases fetal Leydig cell proliferation but inhibits its differentiation of male fetuses after gestational exposure

Triadimefon is a broad-spectrum fungicide widely applied in the agriculture. It is believed to be an endocrine disruptor. Whether triadimefon can inhibit the development of fetal Leydig cells and the underlying mechanisms are unknown. Thirty-two female pregnant Sprague-Dawley rats were randomly assigned into four groups and were dosed via gavage of triadimefon (0, 25, 50, and 100 mg/kg/day) for 9 days from gestational day (GD) 12-20. Triadimefon significantly reduced serum testosterone level in male fetuses at 100 mg/kg. The double immunofluorescence staining of proliferating cell nuclear antigen (PCNA) and cytochrome P450 cholesterol side-chain cleavage (a biomarker for fetal Leydig cells) was used to measure PCNA-labeling in fetal Leydig cells. It markedly increased fetal Leydig cell number primarily via increasing single cell population and elevated the PCNA-labeling of fetal Leydig cells in male fetuses at 100 mg/kg while it induced abnormal aggregation of fetal Leydig cells. The expression levels of fetal Leydig cell genes, Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Insl3 and Nr5a1, were determined to explore its effects on fetal Leydig cell development. We found that triadimefon markedly down-regulated the expression of Leydig cell genes, Hsd17b3, Insl3, and Nr5a1 as low as 25 mg/kg and Scarb1 and Cyp11a1 at 100 mg/kg. It did not affect Sertoli cell number but markedly down-regulated the expression of Sertoli cell gene Amh at 50 and 100 mg/kg. Triadimefon significantly down-regulated the expression of antioxidant genes Sod1, Gpx1, and Cat at 25-100 mg/kg, suggesting that it can induce oxidative stress in fetal testis, and it reduced the phosphorylation of ERK1/2 and AKT2 at 100 mg/kg, indicating that it can inhibit the development of fetal Leydig cells. In conclusion, gestational exposure to triadimefon inhibits the development of fetal Leydig cells in male fetuses by inhibiting its differentiation.

Male Hypogonadism and Disorders of Sex Development

Disorders of Sex Development (DSD) are congenital anomalies in which there is a discordance between chromosomal, genetic, gonadal, and/or internal/external genital sex. In XY individuals, the process of fetal sex differentiation can be disrupted at the stage of gonadal differentiation, resulting in gonadal dysgenesis, a form of early fetal-onset primary hypogonadism characterized by insufficient androgen and anti-Müllerian hormone (AMH) production, which leads to the development of ambiguous or female genitalia. The process of sex differentiation can also be disrupted at the stage of genital differentiation, due to isolated defects in androgen or AMH secretion, but not both. These are forms of fetal-onset hypogonadism with dissociated gonadal dysfunction. In this review, we present a perspective on impaired testicular endocrine function, i.e., fetal-onset male hypogonadism, resulting in incomplete virilization at birth.

Hypogonadism in Pediatric Health: Adult Medicine Concepts Fail

The classical definition of hypogonadism, used in adult medicine, as gonadal failure resulting in deficient steroid and gamete production, and its classification into hypergonadotropic and hypogonadotropic refer to primary gonadal and hypothalamic-pituitary disorders respectively and may lead to under- or misdiagnosis in pediatrics. Indeed, in children with primary gonadal failure, gonadotropin levels may be within the reference range for age. Conversely, since gonadotropins and steroids are normally low during childhood, it may prove impossible to show the existence of a hypogonadotropic state before pubertal age. Anti-Müllerian hormone (AMH) and inhibin B arise as more adequate biomarkers to assess gonadal function and increase the possibility of making an earlier diagnosis of hypogonadism in children, which may positively impact on timely management.

Paediatric and adult-onset male hypogonadism

The hypothalamic-pituitary-gonadal axis is of relevance in many processes related to the development, maturation and ageing of the male. Through this axis, a cascade of coordinated activities is carried out leading to sustained testicular endocrine function, with gonadal testosterone production, as well as exocrine function, with spermatogenesis. Conditions impairing the hypothalamic-pituitary-gonadal axis during paediatric or pubertal life may result in delayed puberty. Late-onset hypogonadism is a clinical condition in the ageing male combining low concentrations of circulating testosterone and specific symptoms associated with impaired hormone production. Testosterone therapy for congenital forms of hypogonadism must be lifelong, whereas testosterone treatment of late-onset hypogonadism remains a matter of debate because of unclear indications for replacement, uncertain efficacy and potential risks. This Primer focuses on a reappraisal of the physiological role of testosterone, with emphasis on the critical interpretation of the hypogonadal conditions throughout the lifespan of the male individual, with the exception of hypogonadal states resulting from congenital disorders of sex development.

Insulin-Like Peptide 3 (INSL3) Serum Concentration During Human Male Fetal Life

Context: Insulin-like peptide 3 (INSL3), a protein hormone produced by Leydig cells, may play a crucial role in testicular descent as male INSL3 knockout mice have bilateral cryptorchidism. Previous studies have measured human fetal INSL3 levels in amniotic fluid only. Objective: To measure INSL3 serum levels and mRNA in fetal umbilical cord blood and fetal testes, respectively. Design: INSL3 concentrations were assayed on 50 μl of serum from male human fetal umbilical cord blood by a non-commercial highly sensitive and specific radioimmunoassay. For secondary confirmation, quantitative real-time PCR was used to measure INSL3 relative mRNA expression in 7 age-matched human fetal testes. Setting: UT Southwestern Medical Center, Dallas, TX and Medical University of South Carolina, Charleston, SC. Patients or other Participants: Twelve human male umbilical cord blood samples and 7 human male testes were obtained from fetuses 14-21 weeks gestation. Male sex was verified by leukocyte genomic DNA SRY PCR. Interventions: None. Main Outcome Measures: Human male fetal INSL3 cord blood serum concentrations and testicular relative mRNA expression. Results: INSL3 serum concentrations during human male gestational weeks 15-20 were 2-4 times higher than published prepubertal male levels and were 5-100 times higher than previous reports of INSL3 concentrations obtained from amniotic fluid. Testicular fetal INSL3 mRNA relative expression was low from weeks 14-16, rose significantly weeks 17 and 18, and returned to low levels at week 21. Conclusions: These findings further support the role of INSL3 in human testicular descent and could prove relevant in uncovering the pathophysiology of cryptorchidism.

Development and validation of a mass spectrometry-based assay for quantification of insulin-like factor 3 in human serum

Background:

The circulating level of the peptide hormone insulin-like factor 3 (INSL3) is a promising diagnostic marker reflecting Leydig cell function in the male. Few commercial immunoassays of varying quality exist. Therefore, we decided to develop and validate a precise method for quantification of INSL3 by mass spectrometry.

Methods:

We developed an assay in which the INSL3 A-chain is released from the INSL3 A-B heterodimer by chemical reduction and alkylation. The alkylated INSL3 A-chain is quantitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as substitute for serum INSL3. The method was compared to a validated and sensitive in-house serum INSL3 immunoassay using 97 serum samples from 12 healthy boys during pubertal transition. Adult levels were determined based on sera from 72 adult healthy males aged 18–40 years.

Results:

An LC-MS/MS assay with limit of detection and limit of quantification (LOQ) of 0.06 and 0.15 ng/mL, respectively, and intra-assay CVs <9% in the relevant ranges was obtained. The LC-MS/MS compared well with the in-house immunoassay (Deming regression slope: 1.28; Pearson correlation: R=0.86). INSL3 concentrations increased with pubertal maturation in healthy boys. INSL3 concentrations were above the LOQ in all samples from the adult men. The mean (±2 SD range)for serum INSL3 concentrations in the adult men was 2.2 (0.5–3.9) ng/mL.

Conclusions:

We have developed a robust and sensitive method suitable for quantitation of serum INSL3 in a clinical setting using LC-MS/MS instrumentation available in modern clinical laboratories. The method paves the way for future studies into the clinical role of serum INSL3 measurements.

Evaluation of the correlation between insulin like factor 3, polycystic ovary syndrome, and ovarian maldescent

The aim of this study was to investigate a proposed correlation between the incidentally discovered undescended ovaries and their confirmed diagnosis as a polycystic ovary disease (PCOD) for all cases included, and to evaluate the role of estimated insulin like factor 3 (INSL3) circulating level in the pathogenesis of both abnormal findings. The study group (A) comprised 35 women whose ovaries had been incidentally found to be undescended during the routine laparoscopy for infertility causes, and all had been diagnosed as PCOD. The control category included two subgroups; subgroup (B) included 35 women group, diagnosed as PCOD but with normally allocated ovaries in the true pelvis, and subgroup (C) included 35 healthy women with regular menses and no signs of hyperandrogenism. Correlations between the level of INSL3 and other PCOD relevant biochemical tests: [e.g. BMI, waist-to-hip ratio (WHR), LH, FSH, androstendione (A), total and free testosterone (T & Ft), DHEA-S, and SHBG] had been also investigated. INSL3 levels were significantly higher in PCOD groups (A) and (B) compared to the healthy fertile control subgroup (C) (80.5 ± 29.4, 65.11 ± 15.6, and 41.11 ± 10.2 pg/mL, respectively), and was highest in group (A). Moreover, we identified a strong correlation between INSL3 and androstenedione (r = 0.42, p = 0.0012), and free (r = 0.42, p = .0123) and total testosterone (r = 0.41, p = .004) in the PCOD (A) and (B) subgroup compared to the levels in subgroup (C). LH was significantly higher in all PCOD women in groups (A&B) (12. 3 ± 3.4, and 11.2 ± 1.4 mIU/L, respectively) compared to those in group (A) (5.7 ± 2.5 mIU/L), with a fair correlation with INSL3. However, there was no statistically significant correlation between INSL3 and FSH, DHEA-S, glucose, basal insulin concentration or HOMA-IR in all PCOD women. The strong positive correlation between INSL3, and high ovarian androgens levels in all PCOD women, which appeared clearly in undescended polycystic ovaries could support the proposed syndrome hypothesis between those abnormal findings.

Negative Association Between Sclerostin and INSL3 in Isolated Human Osteocytes and in Klinefelter Syndrome: New Hints for Testis-Bone Crosstalk

CONTEXT

The regulation of bone mass by the testis is a well-recognized mechanism, but the role of Leydig-specific marker insulin-like 3 peptide (INSL3) on the most abundant bone cell population, osteocytes, is unknown. In this study, we aimed to investigate the relationship between INSL3 and sclerostin, an osteocyte-specific protein that negatively regulates bone formation.

DESIGN

Serum sclerostin and INSL3 levels were evaluated in Klinefelter syndrome (KS) and healthy controls. In vitro effect of INSL3 on sclerostin production was evaluated in human cultured osteocytes.

PATIENTS

A total of 103 KS patients and 60 age- and sex-matched controls were recruited.

MAIN OUTCOME MEASURES

Serum sclerostin and INSL3 levels were assessed by enzyme-linked immunosorbent assay. Osteocytes were isolated by fluorescence-assisted cell sorting. Sclerostin expression was evaluated by western blot, immunofluorescence, and reverse transcription polymerase chain reaction. Measurement of bone mineral density was done by dual-energy X-ray absorptiometry at lumbar spine (L1-L4) and femoral neck.

RESULTS

Sclerostin levels were significantly increased in KS subjects, and negatively correlated with INSL3 levels in both cohorts and with bone mineral density in the KS group. Stimulation of cultured osteocytes with INSL3 at 10-7 M significantly decreased both sclerostin messenger RNA and protein expression.

CONCLUSIONS

We report a negative association between the testicular hormone INSL3 and the osteocytic negative regulator of bone formation, sclerostin. We further explored this association in vitro and showed that INSL3 was able to reduce sclerostin expression. These results add further knowledge on the emerging role of sclerostin as a therapeutic target for osteoporosis treatment.

Anti-Müllerian Hormone and Testicular Function in Prepubertal Boys With Cryptorchidism

INTRODUCTION

The functional capacity of the testes in prepubertal boys with cryptorchidism before treatment has received very little attention. The assessment of testicular function at diagnosis could be helpful in the understanding of the pathophysiology of cryptorchidism and in the evaluation of the effect of treatment. Anti-Müllerian hormone is a well-accepted Sertoli cell biomarker to evaluate testicular function during childhood without the need for stimulation tests.

OBJECTIVE

The aim of the study was to assess testicular function in prepubertal children with cryptorchidism before orchiopexy, by determining serum anti-Müllerian hormone (AMH). We also evaluated serum gonadotropins and testosterone and looked for associations between testicular function and the clinical characteristics of cryptorchidism.

MATERIALS AND METHODS

We performed a retrospective, cross-sectional, analytical study at a tertiary pediatric public hospital. All clinical charts of patients admitted at the outpatient clinic, and recorded in our database with the diagnosis of cryptorchidism, were eligible. The main outcome measure of the study was the serum concentration of AMH. Secondary outcome measures were serum LH, FSH, and testosterone. For comparison, serum hormone levels from a normal population of 179 apparently normal prepubertal boys were used.

RESULTS

Out of 1,557 patients eligible in our database, 186 with bilateral and 124 with unilateral cryptorchidism were selected using a randomization software. Median AMH standard deviation score was below 0 in both the bilaterally and the unilaterally cryptorchid groups, indicating that testicular function was overall decreased in patients with cryptorchidism. Serum AMH was significantly lower in boys with bilateral cryptorchidism as compared with controls and unilaterally cryptorchid patients between 6 months and 1.9 years and between 2 and 8.9 years of age. Serum AMH below the normal range reflected testicular dysfunction in 9.5-36.5% of patients according to the age group in bilaterally cryptorchid boys and 6.3-16.7% in unilaterally cryptorchid boys. FSH was elevated in 8.1% and LH in 9.1% of boys with bilateral cryptorchidism, most of whom were anorchid. In patients with present testes, gonadotropins were only mildly elevated in less than 5% of the cases. Basal testosterone was mildly decreased in patients younger than 6 months old, and uninformative during childhood.

CONCLUSION

Prepubertal boys with cryptorchidism, especially those with bilaterally undescended gonads, have decreased AMH production. Although serum AMH may fall within the normal range, there is a considerable prevalence of testicular dysfunction during childhood in this frequent condition.

The 1.78-kb insertion in the 3'-untranslated region of RXFP2 does not segregate with horn status in sheep breeds with variable horn status

BACKGROUND

The mode of inheritance of horn status in sheep is far more complex than a superficial analysis might suggest. Observations, which were mostly based on crossbreeding experiments, indicated that the allele that results in horns is dominant in males and recessive in females, and some authors even speculated about the involvement of more than two alleles. However, all recent genome-wide association analyses point towards a very strong effect of a single autosomal locus on ovine chromosome 10, which was narrowed down to a putatively causal insertion polymorphism in the 3'-untranslated region of the relaxin/insulin-like family peptide receptor 2 gene (RXFP2). The main objective of this study was to test this insertion polymorphism as the causal mutation in diverse sheep breeds, including breeds with a variable and/or sex-dependent horn status.

RESULTS

After re-sequencing a region of about 246 kb that covered the RFXP2 gene and its flanking regions for 24 sheep from six completely horned and six completely polled breeds, we identified the same insertion polymorphism that was previously published as segregating with horn status in these breeds. Multiplex PCR genotyping of 489 sheep from 34 breeds and some crosses between sheep breeds showed a nearly perfect segregation of the insertion polymorphism with horn status in sheep breeds of Central and Western European origin. In these breeds and their crossings, heterozygous males were horned and heterozygous females were polled. However, this segregation pattern was not, or at least not completely, reproducible in breeds with sex-dependent and/or variable horn status, especially in sheep that originated from even more southern European regions and from Africa. In such breeds, we observed almost all possible combinations of genotype, sex and horn status phenotype.

CONCLUSIONS

The 1.78-kb insertion polymorphism in the 3'-untranslated region of RXFP2 and SNPs in the 3'-UTR, exon 14 and intron 11 of this gene that we analyzed in this study cannot be considered as the only cause of polledness in sheep and are not useful as a universal marker to define the genetic horn status in sheep.

Diethylstilbestrol Regulates the Expression of LGR8 in Mouse Gubernaculum Testis Cells

BACKGROUND Hormonal effects on the gubernaculum can affect testicular descent. Diethylstilbestrol (DES) is a nonsteroidal synthetic estrogen that disrupts the outgrowth of gubernaculums, leading to testis maldescent. However, the underlying mechanisms remain elusive. MATERIAL AND METHODS The gubernaculum were removed from 3-day-old mice and cultured. The subcultured cells were randomly divided into a normal control group and experimental groups. The DES groups were administered 10 μg/ml, 1 μg/ml, 0.1 μg/ml, 0.01 μg/ml of diethylstilbestrol dissolved in dimethyl sulfoxide (DMSO) respectively. The cell morphology was observed under an inverted microscope, and leucine-rich repeat-containing G protein-coupled receptor 8 (LGR8) was localized by immunofluorescence. The expressions of LGR8 gene and protein in gubernaculum cells were quantified by RT-PCR and Flow Cytometer respectively. RESULTS DES treatment converted cells from a normal fibroblast-like morphology into a more refractile, spindle-shaped morphology or irregular elliptical shapes along with cytoplasmic shrinkage. LGR8 was expressed in the cytoplasmic membrane, DES dose-dependently downregulated LGR8 expression at low doses (≤1.0 μg/ml), but upregulated LGR8 at high doses (10 μg/ml) at both the mRNA and protein levels. CONCLUSIONS These results suggest that DES causes testicular maldescent by altering the LGR8 pathway in mouse gubernaculum testis cells.

Hormone Inhibition During Mini-Puberty and Testicular Function in Male Rats

BACKGROUND

The mini-pubertal period of almost six hours in neonatal male rats is thought to be an important stage in sexual development.

OBJECTIVES

The aim of this study was to investigate the effect of hormone inhibition during mini-puberty on testicular function in male rats.

MATERIALS AND METHODS

We measured serum testosterone (T), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in male rats at different time points after birth by enzyme linked immunosorbent assay (ELISA) and established a "no mini-puberty" model by ether inhalation. The mRNA expression levels of testicular androgen receptor (AR), insulin-like growth factor 3 (INSL3), anti-Mullerian hormone (AMH), and ghrelin were determined by real-time polymerase chain reaction (PCR) assays on postnatal days 45 and 75. Testicular tissue biopsies were stained with hematoxylin and eosin (H & E) and the structure, number and maturity of testis cells (including spermatogenic, Sertoli, and Leydig cells) were observed under microscopy at the same time.

RESULTS

Serum T and LH levels peaked at two hours after birth, while FSH peaked at hour 0, and bilateral testicular weight peaked at four hours after birth. The rats that underwent ether inhalation five minutes after birth had markedly reduced serum hormone levels. The mini-puberty model group revealed visible morphologic alterations in the tests on postnatal day 45. Then, on postnatal day 75, the mRNA expression level of AMH significantly decreased (P < 0.05) in the same group.

CONCLUSIONS

The inhibition of mini-puberty period in male rats was demonstrated to have an effect on their testicular function to some extent.

Novel markers of gonadectomy-induced adrenocortical neoplasia in the mouse and ferret

Gonadectomy (GDX) induces sex steroid-producing adrenocortical tumors in certain mouse strains and in the domestic ferret. Transcriptome analysis and DNA methylation mapping were used to identify novel genetic and epigenetic markers of GDX-induced adrenocortical neoplasia in female DBA/2J mice. Markers were validated using a combination of laser capture microdissection, quantitative RT-PCR, in situ hybridization, and immunohistochemistry. Microarray expression profiling of whole adrenal mRNA from ovariectomized vs. intact mice demonstrated selective upregulation of gonadal-like genes including Spinlw1 and Insl3 in GDX-induced adrenocortical tumors of the mouse. A complementary candidate gene approach identified Foxl2 as another gonadal-like marker expressed in GDX-induced neoplasms of the mouse and ferret. That both "male-specific" (Spinlw1) and "female-specific" (Foxl2) markers were identified is noteworthy and implies that the neoplasms exhibit mixed characteristics of male and female gonadal somatic cells. Genome-wide methylation analysis showed that two genes with hypomethylated promoters, Igfbp6 and Foxs1, are upregulated in GDX-induced adrenocortical neoplasms. These new genetic and epigenetic markers may prove useful for studies of steroidogenic cell development and for diagnostic testing.

Phthalate esters affect maturation and function of primate testis tissue ectopically grafted in mice

Di-n-Butyl (DBP) and Di-(2-EthylHexyl) (DEHP) phthalates can leach from daily-use products resulting in environmental exposure. In male rodents, phthalate exposure results in reproductive effects. To evaluate effects on the immature primate testis, testis fragments from 6-month-old rhesus macaques were grafted subcutaneously to immune-deficient mice, which were exposed to 0, 10, or 500 mg/kg of DBP or DEHP for 14 weeks or 28 weeks (DBP only). DBP exposure reduced the expression of key steroidogenic genes, indicating that Leydig cell function was compromised. Exposure to 500 mg/kg impaired tubule formation and germ cell differentiation and reduced numbers of spermatogonia. Exposure to 10 mg/kg did not affect development, but reduced Sertoli cell number and resulted in increased expression of inhibin B. Exposure to DEHP for 14 week also affected steroidogenic genes expression. Therefore, long-term exposure to phthalate esters affected development and function of the primate testis in a time and dosage dependent manner.

Porphyromonas gingivalis lipopolysaccharide upregulates insulin secretion from pancreatic β cell line MIN6

BACKGROUND

A close association between periodontitis and diabetes has been demonstrated in human cross-sectional studies, but an exact relationship between periodontitis and prediabetes has not been established. Previous studies using animal model systems consistently have shown that hyperinsulinemia occurs in animals with periodontitis compared to animals with healthy periodontium (while maintaining normoglycemia). Because bacterial lipopolysaccharide (LPS) plays an important role in the pathogenesis of periodontitis, we hypothesized that LPS may stimulate insulin secretion through a direct effect on β cell function. To test this hypothesis, pancreatic β cell line MIN6 cells were used to determine the effect of Porphyromonas gingivalis (Pg) LPS on insulin secretion. Furthermore, expression of genes altered by Pg LPS in innate immunity and insulin-signaling pathways was determined.

METHODS

MIN6 cells were grown in medium with glucose concentration of normoglycemia (5.5 mM). Pg LPS was added to each well at final concentrations of 50, 200, and 500 ng/mL. Insulin secretion was measured using enzyme-linked immunosorbent assay. Gene expression levels altered by Pg LPS were determined by polymerase chain reaction (PCR) array for mouse innate and adaptive immunity response and mouse insulin-signaling pathways, and results were confirmed for specific genes of interest by quantitative PCR.

RESULTS

Pg LPS stimulated insulin secretion in the normoglycemic condition by ≈1.5- to 3.0-fold depending on the concentration of LPS. Pg LPS treatment altered the expression of several genes involved in innate and adaptive immune response and insulin-signaling pathway. Pg LPS upregulated the expression of the immune response-related genes cluster of differentiation 8a (Cd8a), Cd14, and intercellular adhesion molecule-1 (Icam1) by about two-fold. LPS also increased the expression of two insulin signaling-related genes, glucose-6-phosphatase catalytic subunit (G6pc) and insulin-like 3 (Insl3), by three- to four-fold.

CONCLUSIONS

We have demonstrated for the first time that Pg LPS stimulates insulin secretion by pancreatic β cell line MIN cells. Pg LPS may have significant implications on the development of β cell compensation and insulin resistance in prediabetes in individuals with periodontitis.

The INSL3 gene is a direct target for the orphan nuclear receptor, COUP-TFII, in Leydig cells

Insulin-like 3 (INSL3), a hormone produced by Leydig cells, regulates testicular descent during foetal life and bone metabolism in adults. Despite its importance, little is known about the molecular mechanisms controlling INSL3 expression. Reduced Insl3 mRNA levels were reported in the testis of mice deficient for chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), an orphan nuclear receptor known to play critical roles in cell differentiation and lineage determination in several tissues. Although COUP-TFII-deficient mice had Leydig cell dysfunction and impaired fertility, it remained unknown whether Insl3 expression was directly regulated by COUP-TFII. In this study, we observed a significant decrease in Insl3 mRNA levels in MA-10 Leydig cells depleted of COUP-TFII. Furthermore, a -1087 bp mouse Insl3 promoter was activated fourfold by COUP-TFII in MA-10 Leydig cells. Using 5' progressive deletions, the COUP-TFII-responsive element was located between -186 and -79 bp, a region containing previously uncharacterised direct repeat 0-like (DR0-like) and DR3 elements. The recruitment and direct binding of COUP-TFII to the DR0-like element were confirmed by chromatin immunoprecipitation and DNA precipitation assay respectively. Mutation of the DR0-like element, which prevented COUP-TFII binding, significantly decreased COUP-TFII-mediated activation of the -1087 bp Insl3 reporter in CV-1 fibroblast cells but not in MA-10 Leydig cells. Finally, we found that COUP-TFII cooperates with the nuclear receptor steroidogenic factor 1 (SF1) to further enhance Insl3 promoter activity. Our results identify Insl3 as a target for COUP-TFII in Leydig cells and revealed that COUP-TFII acts through protein-protein interactions with other DNA-bound transcription factors, including SF1, to activate Insl3 transcription in these cells.

Spermatogenesis and cryptorchidism

Cryptorchidism represents the most common endocrine disease in boys, with infertility more frequently observed in bilateral forms. It is also known that undescended testes, if untreated, lead to an increased risk of testicular tumors, usually seminomas, arising from mutant germ cells. In normal testes, germ cell development is an active process starting in the first months of life when the neonatal gonocytes transform into adult dark (AD) spermatogonia. These cells are now thought to be the stem cells useful to support spermatogenesis. Several researches suggest that AD spermatogonia form between 3 and 9 months of age. Not all the neonatal gonocytes transform into AD spermatogonia; indeed, the residual gonocytes undergo involution by apoptosis. In the undescended testes, these transformations are inhibited leading to a deficient pool of stem cells for post pubertal spermatogenesis. Early surgical intervention in infancy may allow the normal development of stem cells for spermatogenesis. Moreover, it is very interesting to note that intra-tubular carcinoma in situ in the second and third decades have enzymatic markers similar to neonatal gonocytes suggesting that these cells fail transformation into AD spermatogonia and likely generate testicular cancer (TC) in cryptorchid men. Orchidopexy between 6 and 12 months of age is recommended to maximize the future fertility potential and decrease the TC risk in adulthood.

Spreading the clinical window for diagnosing fetal-onset hypogonadism in boys

In early fetal development, the testis secretes - independent of pituitary gonadotropins - androgens and anti-Müllerian hormone (AMH) that are essential for male sex differentiation. In the second half of fetal life, the hypothalamic-pituitary axis gains control of testicular hormone secretion. Follicle-stimulating hormone (FSH) controls Sertoli cell proliferation, responsible for testis volume increase and AMH and inhibin B secretion, whereas luteinizing hormone (LH) regulates Leydig cell androgen and INSL3 secretion, involved in the growth and trophism of male external genitalia and in testis descent. This differential regulation of testicular function between early and late fetal periods underlies the distinct clinical presentations of fetal-onset hypogonadism in the newborn male: primary hypogonadism results in ambiguous or female genitalia when early fetal-onset, whereas it becomes clinically undistinguishable from central hypogonadism when established later in fetal life. The assessment of the hypothalamic-pituitary-gonadal axis in male has classically relied on the measurement of gonadotropin and testosterone levels in serum. These hormone levels normally decline 3-6 months after birth, thus constraining the clinical evaluation window for diagnosing male hypogonadism. The advent of new markers of gonadal function has spread this clinical window beyond the first 6 months of life. In this review, we discuss the advantages and limitations of old and new markers used for the functional assessment of the hypothalamic-pituitary-testicular axis in boys suspected of fetal-onset hypogonadism.

Testicular function and bone metabolism--beyond testosterone

Findings in the past few years have advanced understanding of the crosstalk between testis and bone and could contribute to defining an improved clinical approach to the biochemical diagnosis and therapeutic management of hypogonadism and male osteoporosis. This Review focuses on the Leydig cells of the testis. Other than being responsible for steroidogenesis and production of testosterone, the function of these cells is fundamental to bone health in at least two other ways: Leydig cells produce insulin-like 3 (INSL3), which has a role in osteoblast function, and they contribute to 25-hydroxylation of vitamin D. Impairment of testicular function leads to low levels of testosterone, INSL3 and 25-hydroxyvitamin D and consequently to an increased risk of osteopenia and osteoporosis.

The prepubertal testis: biomarkers and functions

PURPOSE OF REVIEW

Biomarkers of prepubertal testicular function have become widely available only in recent years. The aim of this review is to update the knowledge on key biomarkers used to assess hypogonadism in boys.

RECENT FINDINGS

Sertoli cells are the most representative cells of the prepubertal testis. Anti-Müllerian hormone and inhibin B are essential biomarkers of Sertoli cell function. Also, INSL3 arises as an additional marker of Leydig cell dysfunction.

SUMMARY

The widespread use of these biomarkers has enhanced our knowledge on the pathophysiology and diagnosis of prepubertal male hypogonadism. Beyond their well known germ-cell toxicity, oncologic treatments may also affect Sertoli cell function. Pathophysiology is not the same in all aneuploidies leading to infertility: while hypogonadism is not evident until mid-puberty in Klinefelter syndrome, it is established in early infancy in Down syndrome. In Noonan syndrome, the occurrence of primary hypogonadism depends on the existence of cryptorchidism, and Prader-Willi syndrome may present with either primary or combined forms of hypogonadism. Prepubertal testicular markers have also provided insights into the effects of environmental disruptors on gonadal function from early life, and helped dissipate concerns about testicular function in boys born preterm or small for gestational age or conceived by assisted reproductive technique procedures.

Ovarian expression of insulin-like peptide 3 (INSL3) and its receptor (RXFP2) during development of bovine antral follicles and corpora lutea and measurement of circulating INSL3 levels during synchronized estrous cycles

Insulin-like peptide 3 (INSL3), a major product of testicular Leydig cells, is also expressed by the ovary, but its functional role remains poorly understood. Here, we quantified expression of INSL3 and its receptor RXFP2 in theca interna cell (TIC) and granulosa cell compartments of developing bovine antral follicles and in corpora lutea (CL). INSL3 and RXFP2 mRNA levels were much higher in TIC than granulosa cell and increased progressively during follicle maturation with INSL3 peaking in large (11-18 mm) estrogen-active follicles and RXFP2 peaking in 9- to 10-mm follicles before declining in larger (11-18 mm) follicles. Expression of both INSL3 and RXFP2 in CL was much lower than in TIC. In situ hybridization and immunohistochemistry confirmed abundant expression of INSL3 mRNA and protein in TIC. These observations indicate follicular TIC rather than CL as the primary site of both INSL3 production and action, implying a predominantly autocrine/paracrine role in TIC. To corroborate the above findings, we showed that in vitro exposure of TIC to a luteinizing concentration of LH greatly attenuated expression of both INSL3 and its receptor while increasing progesterone secretion and expression of STAR and CYP11A1. Moreover, in vivo, a significant cyclic variation in plasma INSL3 was observed during synchronized estrous cycles. INSL3 and estradiol-17β followed a similar pattern, both increasing after luteolysis, before falling sharply after the LH surge. Thus, theca-derived INSL3, likely from the dominant preovulatory follicle, is detectable in peripheral blood of cattle, and expression is down-regulated during luteinization induced by the preovulatory LH surge. Collectively, these findings underscore the likely role of INSL3 as an important intrafollicular modulator of TIC function/steroidogenesis, while raising doubts about its potential contribution to CL function.

Epigenetic: a molecular link between testicular cancer and environmental exposures

In the last decades, studies in rodents have highlighted links between in utero and/or neonatal exposures to molecules that alter endocrine functions and the development of genital tract abnormalities, such as cryptorchidism, hypospadias, and impaired spermatogenesis. Most of these molecules, called endocrine disrupters exert estrogenic and/or antiandrogenic activities. These data led to the hypothesis of the testicular dysgenesis syndrome which postulates that these disorders are one clinical entity and are linked by epidemiological and pathophysiological relations. Furthermore, infertility has been stated as a risk factor for testicular cancer (TC). The incidence of TC has been increasing over the past decade. Most of testicular germ cell cancers develop through a pre-invasive carcinoma in situ from fetal germ cells (primordial germ cell or gonocyte). During their development, fetal germ cells undergo epigenetic modifications. Interestingly, several lines of evidence have shown that gene regulation through epigenetic mechanisms (DNA and histone modifications) plays an important role in normal development as well as in various diseases, including TC. Here we will review chromatin modifications which can affect testicular physiology leading to the development of TC; and highlight potential molecular pathways involved in these alterations in the context of environmental exposures.