Theca Cell INSL3 and Steroids Together Orchestrate the Growing Bovine Antral Follicle

Discovery of RXFP2 genetic association in resistant hypertensive men and RXFP2 antagonists for the treatment of resistant hypertension

Hypertension remains a leading cause of cardiovascular and kidney diseases. Failure to control blood pressure with ≥ 3 medications or control requiring ≥ 4 medications is classified as resistant hypertension (rHTN) and new therapies are needed to reduce the resulting increased risk of morbidity and mortality. Here, we report genetic evidence that relaxin family peptide receptor 2 (RXFP2) is associated with rHTN in men, but not in women. This study shows that adrenal gland gene expression of RXFP2 is increased in men with hypertension and the RXFP2 natural ligand, INSL3, increases adrenal steroidogenesis and corticosteroid secretion in human adrenal cells. To address the hypothesis that RXFP2 activation is an important mechanism in rHTN, we discovered and characterized small molecule and monoclonal antibody (mAb) blockers of RXFP2. The novel chemical entities and mAbs show potent, selective inhibition of RXFP2 and reduce aldosterone and cortisol synthesis and release. The RXFP2 mAbs have suitable rat pharmacokinetic profiles to evaluate the role of RXFP2 in the development and maintenance of rHTN. Overall, we identified RXFP2 activity as a potential new mechanism in rHTN and discovered RXFP2 antagonists for the future interrogation of RXFP2 in cardiovascular and renal diseases.

Targeted deletion of NR2F2 and VCAM1 in theca cells impacts ovarian follicular development: insights into polycystic ovary syndrome?†

Defining features of polycystic ovary syndrome (PCOS) include elevated expression of steroidogenic genes, theca cell androgen biosynthesis, and peripheral levels of androgens. In previous studies, we identified vascular cell adhesion molecule 1 (VCAM1) as a selective androgen target gene in specific NR2F2/SF1 (+/+) theca cells. By deleting NR2F2 and VCAM1 selectively in CYP17A1 theca cells in mice, we documented that NR2F2 and VCAM1 impact distinct and sometimes opposing theca cell functions that alter ovarian follicular development in vivo: including major changes in ovarian morphology, steroidogenesis, gene expression profiles, immunolocalization images (NR5A1, CYP11A1, NOTCH1, CYP17A1, INSL3, VCAM1, NR2F2) as well as granulosa cell functions. We propose that theca cells impact follicle integrity by regulating androgen production and action, as well as granulosa cell differentiation/luteinization in response to androgens and gonadotropins that may underlie PCOS.

Age-related changes in circulating INSL3 concentrations and their associations with ovarian conditions in Japanese Black beef cattle

Information on circulating levels of insulin-like peptide 3 (INSL3) in female domesticated animals is limited, as their concentrations are significantly lower than in males. The objectives of the present study were to 1) develop a sandwich time-resolved fluorescence immunoassay (TRFIA) with higher detectability to measure blood INSL3 concentrations in female cattle, 2) determine INSL3 concentrations in female cattle among age groups and reproductive conditions, and 3) explore associations between INSL3 levels and ultrasonographic ovarian measurements. Blood was collected repeatedly from Japanese Black beef female calves (n = 12; 0－8 mo), heifers (n = 10; 10－26 mo), and cows (n = 20; 27－200 mo). Blood was taken from the cows (n = 13) at follicular, post-ovulatory, and luteal phases, and from cows with follicular cysts (n = 12). Ultrasonography of ovaries was conducted in the calves (n = 12) and the cows without ovarian diseases (n = 9). The ovarian area, as well as the number and diameters of antral follicles ≥ 2 mm, were determined in each ovary. The proposed method detected a difference in plasma INSL3 between calves (0.01 ng/mL) and heifers (0.18 ng/mL). However, the conventional assay showed similar levels for calves and heifers (1.82 vs 2.07 ng/mL). Plasma INSL3 and testosterone concentrations increased from calves to heifers (P < 0.0001), but only INSL3 rose from heifers to cows (P < 0.0001). INSL3 and testosterone concentrations did not change across the estrus cycle in cows, and the levels of both hormones in follicular cystic cows did not differ from those in the follicular phase. Ovarian area, maximal and average follicular diameters, and total volume of all follicles per animal were higher in cows than calves (P < 0.001). Plasma INSL3 concentrations correlated positively with the total volumes of all follicles in calves (P < 0.05) and cows (P < 0.05), whereas testosterone concentrations did not correlate with ovarian follicular measurements. In conclusion, plasma INSL3 concentrations measured by the proposed sandwich TRFIA showed a clear increase from female calves to cows in beef cattle. These results suggest that circulating levels of INSL3, but not of testosterone, are associated with the total volume of all antral follicles in both ovaries per animal in female cattle.

Current understanding of the genomic abnormities in premature ovarian failure: chance for early diagnosis and management

Premature ovarian failure (POF) is an insidious cause of female infertility and a devastating condition for women. POF also has a strong familial and heterogeneous genetic background. Management of POF is complicated by the variable etiology and presentation, which are generally characterized by abnormal hormone levels, gene instability and ovarian dysgenesis. To date, abnormal regulation associated with POF has been found in a small number of genes, including autosomal and sex chromosomal genes in folliculogenesis, granulosa cells, and oocytes. Due to the complex genomic contributions, ascertaining the exact causative mechanisms has been challenging in POF, and many pathogenic genomic characteristics have yet to be elucidated. However, emerging research has provided new insights into genomic variation in POF as well as novel etiological factors, pathogenic mechanisms and therapeutic intervention approaches. Meanwhile, scattered studies of transcriptional regulation revealed that ovarian cell function also depends on specific biomarker gene expression, which can influence protein activities, thus causing POF. In this review, we summarized the latest research and issues related to the genomic basis for POF and focused on insights gained from their biological effects and pathogenic mechanisms in POF. The present integrated studies of genomic variants, gene expression and related protein abnormalities were structured to establish the role of etiological genes associated with POF. In addition, we describe the design of some ongoing clinical trials that may suggest safe, feasible and effective approaches to improve the diagnosis and therapy of POF, such as Filgrastim, goserelin, resveratrol, natural plant antitoxin, Kuntai capsule et al. Understanding the candidate genomic characteristics in POF is beneficial for the early diagnosis of POF and provides appropriate methods for prevention and drug treatment. Additional efforts to clarify the POF genetic background are necessary and are beneficial for researchers and clinicians regarding genetic counseling and clinical practice. Taken together, recent genomic explorations have shown great potential to elucidate POF management in women and are stepping from the bench to the bedside.

Expression and Role of INSL3 in the Fetal Testis

Insulin-like peptide 3 (INSL3) is a small peptide hormone of the insulin-relaxin family which is produced and secreted by the fetal Leydig cells in the testes only. It appears to be undetectable in female fetuses. In the human fetus INSL3 synthesis begins immediately following gonadal sex determination at weeks 7 to 8 post coitum and the peptide can be detected in amniotic fluid 1 to 2 weeks later. INSL3 acts through a unique G-protein-coupled receptor, called RelaXin-like Family Peptide receptor 2 (RXFP2), which is expressed by the mesenchymal cells of the gubernacular ligament linking the testes to the inguinal wall. The role of INSL3 in the male fetus is to cause a thickening of the gubernaculum which then retains the testes in the inguinal region, while the remainder of the abdominal organs grow away in an antero-dorsal direction. This represents the first phase of testis descent and is followed later in pregnancy by the second inguino-scrotal phase whereby the testes pass into the scrotum through the inguinal canal. INSL3 acts as a significant biomarker for Leydig cell differentiation in the fetus and may be reduced by maternal exposure to endocrine disrupting chemicals, such as xenoestrogens or phthalates, leading to cryptorchidism. INSL3 may have other roles within the fetus, but as a Leydig cell biomarker its reduction acts also as a surrogate for anti-androgen action.

Insulin-like peptide 3 in domestic animals with normal and abnormal reproductive functions, in comparison to rodents and humans

Background

Insulin-like peptide 3 (INSL3) is a circulating hormone secreted from only testis and ovaries in mammals. Findings on INSL3 have been gathered from subjects with normal and abnormal reproductive statuses, especially rodents and humans. However, little to no review articles focusing on INSL3 in domestic animals exist.

Methods

The author reviewed the past and recent literature regarding the structure, expression, roles of INSL3 in the reproductive organs, and its circulation under normal and aberrant reproductive conditions in domestic animals in comparison with rodents and humans.

Main findings

As with humans and rodents, blood INSL3 concentrations rise around puberty in normal male domestic animals and are associated with testicular size. INSL3 levels are acutely upregulated by luteinizing hormone (LH), and the increase is smaller than that of testosterone in male ruminants, whereas the acute regulation of INSL3 by LH does not occur in human men. Dogs with cryptorchidism and bulls with abnormal semen have lowered INSL3 levels.

Conclusion

The findings regarding INSL3 secretions in male domestic animals with normal and aberrant reproductive functions illustrate similar or dissimilar points to humans and rodents. Data on blood INSL3 levels in normal and abnormal female domestic species are still limited and require further investigation.

Effects of colostrum management on transfer of passive immunity and the potential role of colostral bioactive components on neonatal calf development and metabolism

Neonatal dairy and beef calves are required to ingest adequate volumes of high-quality colostrum during their first hours of life to acquire transfer of passive immunity (TPI). As such, immunoglobulin G (IgG) has largely been the focus of colostrum research over recent decades. Yet, little is known about the additional bioactive compounds in colostrum that potentially influence newborn calf development and metabolism. The purpose of this narrative review is to synthesize research regarding the effects of colostrum management practices on TPI, as well as to address the potential role of additional colostral bioactive molecules, including oligosaccharides, fatty acids, insulin, and insulin-like growth factor-I, in promoting calf development and metabolism. Due to the importance of IgG in ensuring calf immunity and health, we review past research describing the process of colostrogenesis and dam factors influencing the concentrations of IgG in an effort to maximize TPI. We also address the transfer of additional bioactive compounds in colostrum and prepartum management and dam factors that influence their concentrations. Finally, we highlight key areas of future research for the scientific community to pursue to ultimately improve the health and welfare of neonatal dairy calves.

Comparative transcriptomic analysis of ovaries from high and low egg-laying Lingyun black-bone chickens

Egg‐laying rate is mainly determined by ovarian function and regulated by the hypothalamic‐pituitary‐gonadal axis; however, the mechanism by which the ovary regulates the egg‐laying rate is still poorly understood. The purpose of this study was to compare the differences in the transcriptomes of the ovary of Lingyun black‐bone chickens with relatively high and low egg‐laying rates and screen candidate genes related to the egg‐laying rate. RNA‐sequencing (RNA‐Seq) was conducted to explore the chicken transcriptome from the ovarian tissue of six Lingyun black‐bone chickens with high (group G, n = 3) and low (group D, n = 3) egg‐laying rates. The results showed that 235 differentially expressed genes (DEGs) were identified between the chickens with high and low egg‐laying rates; among them, 209 DEGs were up‐regulated and 26 DEGs were down‐regulated. Gene Ontology analysis showed that the up‐regulated 209 DEGs were enriched in 50 GO terms and the down‐regulated 26 DEGs were enriched in 40 GO terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that up‐regulated DEGs were significantly enriched in 25 pathways and down‐regulated DEGs were significantly enriched in three pathways. Among the pathways, we found the longevity regulating pathway‐multiple species pathway, Estrogen signalling pathway and PPAR signalling pathway may have an essential function in regulating the egg‐laying rate. The results highlighted DEGs in the ovarian tissues of relatively high and low laying Lingyun black‐bone chicken and identified essential candidate genes related to the egg‐laying rate, thereby providing a theoretical basis for improving the egg‐laying rate of Lingyun black‐bone chicken.

The ovarian follicle of ruminants: the path from conceptus to adult

This review resulted from an international workshop and presents a consensus view of critical advances over the past decade in our understanding of follicle function in ruminants. The major concepts covered include: (1) the value of major genes; (2) the dynamics of fetal ovarian development and its sensitivity to nutritional and environmental influences; (3) the concept of an ovarian follicle reserve, aligned with the rise of anti-Müllerian hormone as a controller of ovarian processes; (4) renewed recognition of the diverse and important roles of theca cells; (5) the importance of follicular fluid as a microenvironment that determines oocyte quality; (6) the 'adipokinome' as a key concept linking metabolic inputs with follicle development; and (7) the contribution of follicle development to the success of conception. These concepts are important because, in sheep and cattle, ovulation rate is tightly regulated and, as the primary determinant of litter size, it is a major component of reproductive efficiency and therefore productivity. Nowadays, reproductive efficiency is also a target for improving the 'methane efficiency' of livestock enterprises, increasing the need to understand the processes of ovarian development and folliculogenesis, while avoiding detrimental trade-offs as greater performance is sought.

Physiology and evolution of the INSL3/RXFP2 hormone/receptor system in higher vertebrates

Although the insulin-like peptide hormone INSL3 and its cognate receptor RXFP2 (relaxin-family peptide receptor 2) have existed throughout chordate evolution, their physiological diversification appears to be linked closely with mammalian emergence and radiation. In contrast, they have been lost in birds and reptiles. Both hormone and receptor are expressed from autosomal genes which have maintained their synteny across vertebrate evolution. Whereas the INSL3 gene comprises only two exons closely linked to the JAK3 gene, RXFP2 is normally encoded by 18 exons. Both genes, however, are subject to alternative splicing to yield a variety of possibly inactive or antagonistic molecules. In mammals, the INSL3-RXFP2 dyad has maintained a probably primitive association with gametogenesis, seen also in fish, whereby INSL3 promotes the survival, growth and differentiation of male germ cells in the testis and follicle development in the ovary. In addition, however, the INSL3/RXFP2 system has adopted a typical 'neohormone' profile, essential for the promotion of internal fertilisation and viviparity; fetal INSL3 is essential for the first phase of testicular descent into a scrotum, and also appears to be associated with male phenotype, in particular horn and skeletal growth. Circulating INSL3 is produced exclusively by the mature testicular Leydig cells in male mammals and acts as a potent biomarker for testis development during fetal and pubertal development as well as in ageing. As such it can be used also to monitor seasonally breeding animals as well as to investigate environmental or lifestyle conditions affecting development. Nevertheless, most information about INSL3 and RXFP2 comes from a very limited selection of species; it will be especially useful to gain further information from a more diverse range of animals, especially those whose evolution has led them to express unusual reproductive phenotypes.

Diverse functions of insulin-like 3 peptide

Insulin-like 3 peptide (INSL3) is a member of the insulin-like peptide superfamily and is the only known physiological ligand of relaxin family peptide receptor 2 (RXFP2), a G protein-coupled receptor (GPCR). In mammals, INSL3 is primarily produced both in testicular Leydig cells and in ovarian theca cells, but circulating levels of the hormone are much higher in males than in females. The INSL3/RXFP2 system has an essential role in the development of the gubernaculum for the initial transabdominal descent of the testis and in maintaining proper reproductive health in men. Although its function in female physiology has been less well-characterized, it was reported that INSL3 deletion affects antral follicle development during the follicular phase of the menstrual cycle and uterus function. Since the discovery of its role in the reproductive system, the study of INSL3/RXFP2 has expanded to others organs, such as skeletal muscle, bone, kidney, thyroid, brain, and eye. This review aims to summarize the various advances in understanding the physiological function of this ligand-receptor pair since its first discovery and elucidate its future therapeutic potential in the management of various diseases.