Follistatin and activin A production by the male reproductive tract

Follistatin is a binding protein for the activin and inhibin family of hormones, regulating their biological activity. In the male reproductive tract, the interaction of these factors is likely to be involved in the regulation of the proliferation of several cell types. We have investigated the presence of follistatin and activin A in seminal plasma using specific immunoassays and have localized follistatin and activin/inhibin subunits in the adult human testis, prostate and seminal vesicle to establish their likely sources. High concentrations of immunoreactive follistatin were present in seminal plasma in normal men (mean 97.9 ng/ml; 1.43 ng/ml in peripheral plasma) and were similar in men with oligo/azoospermia and following vasectomy. Follistatin immunoreactivity was localized to both Leydig and Sertoli cells of the testis, and to epithelial cells of the prostate gland and seminal vesicle, which are likely to be the predominant sources of the hormone in seminal plasma. Activin A was also present in seminal plasma in normal men but was undetectable following vasectomy, thus deriving from the testis. Consistent with this finding, the betaA-subunit was immunolocalized in Sertoli and Leydig cells but was not present in seminal vesicle or prostate gland. The functional significance of the high concentrations of follistatin secreted into seminal plasma by the prostate gland and/or seminal vesicle is uncertain, but they may regulate the biological activity of testis-derived activin A and inhibin B.      

A longitudinal study of maternal serum inhibin-A, inhibin-B, activin-A, activin-AB, pro-alphaC and follistatin during pregnancy

Maternal serum concentrations of inhibin-A, inhibin-B, activin-A, activin-AB, pro-alphaC-related inhibin forms, total follistatin, steroids and gonadotrophins were measured longitudinally in six normal singleton pregnancies. Maternal venous blood was collected randomly during a spontaneous follicular phase prior to donor insemination, at 5, 7, 9, 11, 16, 20, 24, 28, 32 and 36 weeks after the first missed menses and in the early puerperium. Steroid and gonadotrophin profiles conformed to previous reports. While at week 5 of gestation inhibin-A, activin-A and follistatin concentrations were similar to those at the follicular phase, all three increased progressively (P < 0.001) to maximal concentrations in week 36: approximately 48-fold (3740 +/- 1349 ng inhibin-A/ml), approximately 22-fold (6109 +/- 1443 ng activin-A/ml) and approximately 10-fold (3563 +/- 418 ng follistatin/ml) higher. Pro- alphaC concentrations reached a maximum in weeks 5 (approximately 5- fold, P < 0.001) and 36 (1027 +/- 174 pg/ml, P < 0.01). Inhibin-B (71 +/- 23 pg/ml prior to pregnancy) was undetectable (<12 pg/ml) between week 5-16 of gestation but increased slightly in the third trimester (26 +/- 7 pg/ml in week 36). Activin-AB was undetectable throughout pregnancy. Post-partum concentrations of inhibin-A (41 +/- 12 ng/ml), inhibin-B (<12 pg/ml), activin-A (950 +/- 149 pg/ml), pro-alphaC (128 +/- 22 pg/ml) and follistatin (990 +/- 79 ng/ml) were substantially lower than at week 36 of gestation. The activin-A:follistatin ratio increased from 0.5 in week 5 to 1.8 in week 36, suggesting that more free activin-A is available in the maternal circulation during late pregnancy.      

Serum concentrations of dimeric inhibins, activin A, gonadotrophins and ovarian steroids during the menstrual cycle in older women

The transition from regular ovarian cyclicity to menopause is associated with a rise in the circulating concentrations of follicle stimulating hormone (FSH), despite the maintenance of serum oestradiol concentrations during the perimenopause. The aim of this study was to compare the pattern of secretion of dimeric inhibins, activin A, gonadotrophins and steroids in regularly cycling women of 40-50 years with normal and raised early follicular phase serum FSH concentrations and young women (25-33 years) during the menstrual cycle. Blood samples were taken prospectively almost daily throughout the menstrual cycle. Women recruited were classified into three groups: (i) older women with normal FSH [(ON-FSH), day 3 FSH <8 mIU/ml, n = 10]; (ii) older women with raised FSH [(R-FSH), day 3 FSH >8 mIU/ml, n = 6] and (iii) young normal FSH (YN-FSH) women, age 25-32 years (n = 6). Cyclic patterns of serum inhibins and activin A were similar in the ON-FSH and YN-FSH groups. The R-FSH group had significantly lower concentrations of inhibin A prior to the luteinizing hormone (LH) surge and in the mid-luteal phase and lower concentrations of inhibin B in the early follicular phase compared with the ON-FSH group. Serum concentrations of activin A, progesterone and oestradiol were similar in all three groups. It is concluded from this study that the rise in early follicular phase serum FSH in older women is associated with a decrease in circulating concentrations of inhibin B in the early follicular phase. However, lower circulating concentrations of inhibin A in the luteal phase of the R-FSH group may also contribute to the rise in early follicular phase FSH concentrations during the menstrual cycle, although further studies with larger numbers are required to confirm this observation.     

The effect of gonadotrophins with differing LH/FSH ratios on the secretion of the various species of inhibin in women receiving IVF

We have measured secretory patterns of inhibin A, B, total alpha inhibin, pro-alphaC inhibin and oestradiol in women following pituitary suppression who were randomised into two groups to receive either urinary gonadotrophin (25:75 IU/ampoule of luteinizing hormone (LH) and follicle stimulating hormone (FSH; Normegon; n = 11) or recombinant (r)FSH (75 IU/ampoule of FSH alone, n = 16). The women were of similar age (approximately 33 years) and length of infertility (approximately 4 years) and had a normal endocrine evaluation. Plasma FSH, LH, oestradiol, inhibin A, B, pro-alphaC and total alpha inhibin were measured by immunoassay prior to and following gonadotrophin stimulation. Immunoactive FSH, LH and oestradiol blood concentrations following pituitary down regulation were similar in the two groups being <2.0, <3.6 IU/l and <82 pmol/l respectively. The units of FSH given (2230 versus 2764 IU; Normegon versus rFSH), duration of treatment (9.1 versus 9.4 days) and number of follicles of > or =14mm on the day of human chorionic gonadotrophin (HCG) administration (17 versus 14) were also similar. Inhibin A or B concentrations rose similarly during Normegon or rFSH administration, peaking at days 9-11. Total alpha and pro-alphaC inhibin concentrations were lower (P < 0.05) in the rFSH group during days 10 and 11 of treatment being 18.9 +/- 15.9 ng/ml (Normegon) and 4.6 +/- 2.8 ng/ml (rFSH) for total alpha inhibin and 8.5 +/- 6.8 ng/ml (Normegon) and 2.8 +/- 1.6 ng/ml (rFSH) for pro-alphaC inhibin on day 10. Overall, higher total alpha inhibin concentrations were associated with more mature follicles and oocytes, greater fertilization rates and better quality embryos. We conclude that inhibin A and B secretion was similar in both groups and is primarily controlled by FSH, whereas total alpha inhibin and pro-alphaC increased preferentially in the Normegon group over the rFSH group, indicating that they are, in part, stimulated by LH.     

Increased superoxide generation and decreased stress protein Hsp90 expression in human umbilical cord vein endothelial cells (HUVECs) from pregnancies complicated by preeclampsia.

OBJECTIVE: Endothelial dysfunction is associated with increased oxidative stress in the vascular system in women with preeclampsia (PE), a hypertensive disorder occurring during human pregnancy. However, due to the nature of the disease, direct evidence of increased endothelial oxidative stress in the maternal vascular system at an in vivo situation is still lacking. We previously reported that primary cultured endothelial cells (ECs) from umbilical cords (HUVECs) from pregnancies complicated by PE exhibit phenotypic changes compared to those from normal pregnancies such as reduced eNOs expression associated with disorganized endothelial junction protein distribution and increased endothelial permeability. In this study, we sought to determine whether increased oxidative stress was also present in primary cultured HUVECs from women with PE. METHODS: HUVECs were isolated from normal and PE pregnancies and EC oxidative stress was examined by superoxide generation using positive nuclear dihydroethidium (DHE) staining as an indicator. Since Hsp90 is believed to have protective effects on endothelial function, we also determined mRNA and protein expression for Hsp90. Using Hsp90 inhibitor geldanamycin (GA), we further determined the potential role of Hsp90 in superoxide generation, eNOs expression, and prostacyclin production of altered EC function associated with PE pregnancies. RESULTS: We found that primary cultured ECs from PE pregnancies showed an increase in DHE positive cells, p < 0.01. Hsp90 protein expression was significantly decreased in ECs from PE compared with that from normal pregnancies, p < 0.05. Inhibition of Hsp90 by GA resulted in an increase in superoxide generation and a decrease in eNOs protein expression. Decreased prostacyclin production was also found in ECs treated with GA. CONCLUSION: These in vitro HUVEC data suggest that increased endothelial oxidative stress may also occur in the fetal compartment during preeclampsia.     

Nocturnal secretory dynamics of inhibin B and testosterone in pre- and peripubertal boys

To investigate the secretory dynamics of testosterone and inhibin B, we collected samples every 20 min from 2000 h to 0800 h in 20 boys. Boys in group 1 (n = 5) were aged less than 8 yr, group 2 (n = 5) were aged more than 8 yr but 1.5 yr or more before pubertal onset, group 3 (n = 5) were studied 1.0 yr or less before pubertal onset, and group 4 (n = 5) were in early puberty. Testosterone increased after midnight in peripubertal boys, coinciding with the onset of LH pulsatility, and showed a pulsatile pattern in 6 of 10 of these boys. Cross-correlation analysis indicated significant temporal coupling between LH and testosterone. Inhibin B was higher in groups 3 and 4, compared with groups 1 and 2 (P < 0.01) and showed a downward trend overnight with no evidence of pulsatility and no evidence of short-term interactions with LH, FSH, or testosterone. Inhibin B and LH nocturnal means were both inversely correlated with time before pubertal onset (r(s) > or = -0.85, P < 0.01). Only LH nocturnal mean and amplitude, respectively, contributed independently to prediction of testosterone and inhibin B nocturnal means, explaining 71 and 65% of their variability. We conclude that both testosterone and inhibin B are related to nocturnal LH release in peripubertal boys but over different time scales.     

Increased Risk for Group B Streptococcus Sepsis in Young Infants Exposed to HIV,Soweto, South Africa, 2004–2008

Although group B Streptococcus (GBS) is a leading cause of severe invasive disease in young infants worldwide, epidemiologic data and knowledge about risk factors for the disease are lacking from low- to middle-income countries. To determine the epidemiology of invasive GBS disease among young infants in a setting with high maternal HIV infection, we conducted hospital-based surveillance during 2004–2008 in Soweto, South Africa. Overall GBS incidence was 2.72 cases/1,000 live births (1.50 and 1.22, respectively, among infants with early-onset disease [EOD] and late-onset [LOD] disease). Risk for EOD and LOD was higher for HIV-exposed than HIV-unexposed infants. GBS serotypes Ia and III accounted for 84.0% of cases, and 16.9% of infected infants died. We estimate that use of trivalent GBS vaccine (serotypes Ia, Ib, and III) could prevent 2,105 invasive GBS cases and 278 deaths annually among infants in South Africa; therefore, vaccination of all pregnant women in this country should be explored.     

Follicle-stimulating hormone-inhibin B interactions during the follicular phase of the primate menstrual cycle revealed by gonadotropin-releasing hormone antagonist and antiestrogen treatment

The aim was to determine the pattern of inhibin A and inhibin B secretion during the ovulatory cycle of the macaque and to explore the effects of manipulating follicular phase FSH on inhibin B secretion by: 1) blocking the early follicular phase rise in FSH with GnRH antagonist treatment; 2) administering FSH in GnRH antagonist-treated animals; and 3) preventing the midfollicular phase decline in FSH by a specific antiestrogen. Treatment with GnRH antagonist, starting on day 25 of the cycle, abolished the early follicular phase rise in FSH and the associated increase in inhibin B. The same treatment, followed by exogenous FSH, restored the secretion of inhibin B. Treatment with antiestrogen, commencing during the midfollicular phase, induced a supraphysiological rise in FSH, followed by a marked stimulation of inhibin B and estradiol secretion. Despite continued antiestrogen treatment, FSH secretion declined before peak values of inhibin B and estradiol were attained, implying a potential endocrine role for inhibin B, in addition to estradiol, in the negative feedback regulation of FSH. These results show that follicular phase FSH is the major stimulus for inhibin B secretion.     

Amniotic fluid concentrations of dimeric inhibins, activin A and follistatin in pregnancy

OBJECTIVE: The feto-placental unit is the major source of circulating concentrations of inhibin A and activin A in human pregnancy. The aim of this study was to measure the amniotic fluid concentrations of inhibin A, inhibin B, activin A and follistatin in pregnancies bearing male and female fetuses. DESIGN AND METHOD: Amniotic fluid samples collected by amniocentesis were stored at -20 degrees C. Dimeric inhibins, 'total' activin A and 'total' follistatin were measured using specific two-site enzyme immunoassays. Samples were assayed blindly and the information on fetal sex was obtained from the cytogenetics laboratory. RESULTS: Data show that amniotic fluid concentrations of inhibin A, inhibin B and activin A gradually increase with gestation whilst concentrations of follistatin are similar between weeks 15 and 20 of pregnancy. Mean amniotic fluid levels of inhibin A and inhibin B at 16 and 17 weeks gestation and mean activin A levels at 15 and 16 weeks gestation are considerably lower in pregnancies with male (n=24) compared with female (n=28) fetuses. Levels of follistatin are not different in the male and female fetal pregnancies at any studied gestation. CONCLUSIONS: The results indicate that amniotic fluid contains high concentrations of inhibins (A and B), activin A and follistatin in early pregnancy suggesting that these hormones are produced by the fetal membranes and may be involved in the development of the fetus.     

Detection of dimeric inhibin throughout the human menstrual cycle by two-site enzyme immunoassay

OBJECTIVE We have developed and validated a two-site immunoassay for the measurement of dimeric inhibin in plasma and subsequently measured dimeric inhibin levels in plasma through the normal female menstrual cycle. DESIGN Recombinant inhibin added to plasma samples was quantitatively recovered in both follicular and luteal phase, and serial dilutions of samples were tested for parallelism to similar dilutions of recombinant 32kDa inhibin. Daily samples were assayed from four women through a menstrual cycle. PATIENTS (a) Four groups of six women who (i) were in the follicular phase of a normal menstrual cycle, (ii) were in the luteal phase of a normal menstrual cycle, (iii) were post-menopausal and (iV) who had received hMG to induce superovulation. (b) Four healthy female volunteers aged 25–33. RESULTS Post-menopausal women had less than 2ng/l of inhibin whereas six women treated with hMG had dimeric inhibin concentrations up to 1125ng/l. During the early follicular phase, at the time of onset of menstruation, extremely low levels of dimeric inhibin were found (3-4ng/l (CI 2.2-5.0)) while in the late follicular phase, there was a marked increase in dimeric inhibin concentration. The concentration of dimeric inhibin was maximal (65.6 ng/l (CI 53.1-81,1)) in the mid-luteal phase. The overall pattern of dimeric inhibin concentration during the menstrual cycle was similar to that observed with previous inhibin assays although the magnitude of change was considerably greater. CONCLUSION The human ovary, In particular the corpus luteum, secretes significant amounts of dimeric and therefore biologically active inhibin.