Acute prenatal androgen treatment increases birth weights and growth rates in lambs

Sex dimorphism of weight and length at birth: evidence based on disorders of sex development

BACKGROUND

Males have higher weight and length at birth than females.

AIM

To verify the influence of the Y chromosome and the action of intrauterine androgens on weight and length at birth of children with Disorders of Sex Development (DSD).

SUBJECTS AND METHODS

A cross-sectional and retrospective study. Patients with Turner syndrome (TS), complete (XX and XY), mixed (45,X/46,XY) and partial (XY) gonadal dysgenesis (GD), complete (CAIS) and partial (PAIS) androgen insensitivity syndromes and XX and XY congenital adrenal hyperplasia (CAH) were included. Weight and length at birth were evaluated.

RESULTS

Weight and length at birth were lower in TS and mixed GD when compared to XY and XX DSD cases. In turn, patients with increased androgen action (117 cases) had higher weight and length at birth when compared to those with absent (108 cases) and decreased (68 cases) production/action. In birthweight, there was a negative influence of the 45,X/46,XY karyotype and a positive influence of increased androgen and gestational age. In birth length, there was a negative influence of the 45,X and 45,X/46,XY karyotypes and also a positive influence of increased androgen and gestational age.

CONCLUSIONS

The sex dimorphism of weight and length at birth could possibly be influenced by intrauterine androgenic action.

Prenatal Androgenization of Ewes as a Model of Hirsutism in Polycystic Ovary Syndrome

The main clinical feature associated with hyperandrogenism in polycystic ovary syndrome (PCOS) in humans is hirsutism, where hair increases its length, pigmentation, and particularly its diameter. Currently, it is not known whether PCOS animal models also exhibit changes in the hair. Therefore, the aim of this study was to explore the wool characteristics in sheep prenatally androgenized (PA) with testosterone propionate. After 4 and 13 months of life, wool was collected from the top of the shoulder of both females and males (both androgenized and controls). The offspring sheep were followed for up to 19 months of life to evaluate testosterone and androstenedione serum levels by ultra-high-performance liquid chromatography-tandem mass spectrometry, determine insulin and glucose response to intravenous glucose tolerance test, and address estrus cyclicity during the second breeding season. PA male animals showed a reduction in wool fiber diameter at 4 months of age compared with controls (P = 0.02) but not at 13 months, whereas PA females showed increased hair diameter at 13 months (P = 0.002), with no difference at 4 months. No substantial changes in other hair parameters (length, color, and medullation) were identified. In addition, increased levels of serum testosterone were observed in PA female sheep compared with controls at 12 months (P = 0.03). Our results indicate for the first time, to our knowledge, that changes in wool fiber diameter observed in PA ewes replicate, at the translational level, the increase in hair diameter in hirsute women with PCOS.

The Effects of a Single Developmentally Entrained Pulse of Testosterone in Female Neonatal Mice on Reproductive and Metabolic Functions in Adult Life

Early postnatal exposures to sex steroids have been well recognized to modulate predisposition to diseases of adulthood. There is a complex interplay between timing, duration and dose of endocrine exposures through environmental or dietary sources that may alter the sensitivity of target tissues to the exogenous stimuli. In this study, we determined the metabolic and reproductive programming effects of a single developmentally entrained pulse of testosterone (T) given to female mice in early postnatal period. CD-1 female mice pups were injected with either 5 μg of T enanthate (TE) or vehicle (control [CON] group) within 24 hours after birth and followed to adult age. A total of 66% of T-treated mice exhibited irregular cycling, anovulatory phenotype, and significantly higher ovarian weights than vehicle-treated mice. Longitudinal nuclear magnetic resonance measurements revealed that TE group had greater body weight, whole-body lean, and fat mass than the CON group. Adipose tissue cellularity analysis in TE group revealed a trend toward higher size and number than their littermate CONs. The brown adipose tissue of TE mice exhibited white fat infiltration with down-regulation of several markers, including uncoupling protein 1 (UCP-1), cell death-inducing DNA fragmentation factor, α-subunit-like effector A, bone morphogenetic protein 7 as well as brown adipose tissue differentiation-related transcription regulators. T-injected mice were also more insulin resistant than CON mice. These reproductive and metabolic reprogramming effects were not observed in animals exposed to TE at 3 and 6 weeks of age. Collectively, these data suggest that sustained reproductive and metabolic alterations may result in female mice from a transient exposure to T during a narrow postnatal developmental window.

Effect of variation in ovine WFIKKN2 on growth traits appears to be gender-dependent

WFIKKN2 may play a role in the regulation of muscle growth and development, but to date there have been no reports on the effect of variation in WFIKKN2 on growth and carcass traits in livestock. In this study, the effect of variation in ovine WFIKKN2 was investigated in 800 New Zealand Romney lambs (395 male and 405 female), with five previously described variants (A to E) being identified. Variation in ovine WFIKKN2 was not found to affect various growth traits in the female lambs, but the presence of variant B was associated (P < 0.05) with decreased birth weight, tailing weight, weaning weight and pre-weaning growth rate; and increased post-weaning growth rate in male lambs. In male lambs, the presence of variant B was associated (P < 0.05) with an increased shoulder yield and proportion shoulder yield. No associations with growth or carcass traits were detected for the presence (or absence) of the other variants. These results suggest that variation in ovine WFIKKN2 may have a differential effect on growth in male and female lambs, and hence that the gene may be expressed in, or act in, a gender-specific fashion.

Fetal programming of sexual development and reproductive function

The recent growth of interest in developmental programming of physiological systems has generally focused on the cardiovascular system (especially hypertension) and predisposition to metabolic dysfunction (mainly obesity and diabetes). However, it is now clear that the full range of altered offspring phenotypes includes impaired reproductive function. In rats, sheep and nonhuman primates, reproductive capacity is altered by challenges experienced during critical periods of development. This review will examine available experimental evidence across commonly studied experimental species for developmental programming of female and male reproductive function throughout an individual's life-course. It is necessary to consider events that occur during fetal development, early neonatal life and prior to and during puberty, during active reproductive life and aging as reproductive performance declines.

Ex-premature infant boys with hypospadias are similar in size to age-matched, ex-premature infant boys without hypospadias

OBJECTIVE

Studies have postulated that hypospadias, prematurity, and low birth weight are linked by defects in androgen signaling. To determine whether premature, hypospadiac boys are small and remain so, we compared their size at birth and at hypospadias repair to premature boys who underwent post-neonatal circumcision.

METHODS

We identified premature boys admitted to Texas Children's Hospital who underwent either hypospadias repair or circumcision after 4 months of age. Age, weight, and height at birth and surgery were recorded.

RESULTS

Fifty-four boys had hypospadias and 34 did not. For hypospadiac boys, the mean birth weight and age, height, and weight at surgery were lower than for boys without hypospadias. More importantly, length-for-age and weight-for-age percentiles were also lower for hypospadiac boys. When subset analysis was performed on boys younger than 2 years at surgery, however, there were no significant differences in height or weight between hypospadiac and non-hypospadiac boys.

CONCLUSION

Our series suggests that premature, hypospadiac boys are born smaller than age-matched, non-hypospadiac controls. However, there were no age-corrected size differences between hypospadiac and non-hypospadiac boys at surgery. This implies that hypospadiac boys exhibit post-neonatal 'rebound' growth. Global growth deficits, if any, do not persist in hypospadiac boys.

Postnatal testosterone exposure results in insulin resistance, enlarged mesenteric adipocytes, and an atherogenic lipid profile in adult female rats: comparisons with estradiol and dihydrotestosterone

Postnatal events contribute to features of the metabolic syndrome in adulthood. In this study, postnatally administered testosterone reduced insulin sensitivity and increased the mesenteric fat depot, the size of mesenteric adipocytes, serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides, and the atherogenic index in adult female rats. To assess the involvement of estrogen and androgen receptors in these programming effects, we compared testosterone-exposed rats to rats exposed to estradiol or dihydrotestosterone (DHT). Estradiol-treated rats had lower insulin sensitivity than testosterone-treated rats and, like those rats, had enlarged mesenteric adipocytes and increased triglyceride levels. DHT also reduced insulin sensitivity but did not mimic the other metabolic effects of testosterone. All treated rats were probably anovulatory, but only those treated with testosterone had reduced testosterone levels. This study confirms our previous finding that postnatal administration of testosterone reduces insulin sensitivity in adult female rats and shows that this effect is accompanied by unfavorable changes in mesenteric fat tissue and in serum lipid levels. The findings in the estradiol and DHT groups suggest that estrogen receptors exert stronger metabolic programming effects than androgen receptors. Thus, insults such as sex hormone exposure in early life may have long-lasting effects, thereby creating a predisposition to disturbances in insulin sensitivity, adipose tissue, and lipid profile in adulthood.

In utero exposure to benzophenone-2 causes hypospadias through an estrogen receptor dependent mechanism

PURPOSE

Additives such as benzophenone-2 are commonly used in cosmetic products and food container plastics to filter out ultraviolet light. In pregnant women exposure may result in transplacental transfer of benzophenone-2 to fetuses. Benzophenone-2 is estrogenic in vitro and in the rat uterotropic assay. Estradiol causes hypospadias in mice and estrogen-like compounds are also postulated to cause hypospadias. We determined whether hypospadias would develop in male mice exposed to benzophenone-2 in utero and whether this outcome depended on estrogen receptor pathways.

MATERIALS AND METHODS

Timed pregnant C57BL/6 mice were administered benzophenone-2 (6.25 mg) or control vehicle by oral gavage from gestational days 12 through 17 and they were sacrificed on day 18. Fetuses were weighed and sexed, anogenital distance was measured and genital tubercles were harvested for paraffin sections or quantitative reverse transcriptase-polymerase chain reaction analysis of genes purportedly involved in genital tubercle development.

RESULTS

Eight of 57 benzophenone-2 treated male fetuses (14%) whose genital tubercles were examined histologically had hypospadias (p = 0.0064). Co-administration of benzophenone-2 with the estrogen receptor antagonist EM-800 resulted in normal genital tubercles, ie no hypospadias, in 26 of 26 mice. Likewise no EM-800 or control treated male genital tubercles showed hypospadias. Benzophenone-2 treated male mice had no changes in body mass adjusted anogenital distance relative to controls. Reverse transcriptase-polymerase chain reaction revealed that genital tubercles of benzophenone-2 treated male mice expressed higher levels of estrogen receptor-beta relative to male controls (p = 0.04).

CONCLUSIONS

These findings suggest that benzophenone-2 may cause hypospadias via signaling through the estrogen receptor. Further study of human benzophenone-2 exposure and its effects is needed to support this hypothesis.

Prenatal testosterone excess programs reproductive and metabolic dysfunction in the female

Findings discussed in this review stress the importance of normal estrogen and androgen signaling at appropriate developmental time points in maintaining normal phenotypic expression, reproductive and metabolic function and document how inappropriate steroid signaling, at inopportune times can have undesirable outcomes. For example, inappropriate testosterone exposure during fetal life alters the developmental trajectory of the female culminating in a suite of disorders, which include intrauterine growth-retardation and postnatal catch up growth, phenotypic masculinization, reproductive neuroendocrine and ovarian disruptions leading to progressive loss of cyclicity and metabolic disruptions manifested as hyperinsulinemia.

Cellular and hormonal disruption of fetal testis development in sheep reared on pasture treated with sewage sludge

The purpose of this study was to evaluate whether experimental exposure of pregnant sheep to a mixture of environmental chemicals added to pasture as sewage sludge (n = 9 treated animals) exerted effects on fetal testis development or function; application of sewage sludge was undertaken so as to maximize exposure of the ewes to its contents. Control ewes (n = 9) were reared on pasture treated with an equivalent amount of inorganic nitrogenous fertilizer. Treatment had no effect on body weight of ewes, but it reduced body weight by 12-15% in male (n = 12) and female (n = 8) fetuses on gestation day 110. In treated male fetuses (n = 11), testis weight was significantly reduced (32%), as were the numbers of Sertoli cells (34% reduction), Leydig cells (37% reduction), and gonocytes (44% reduction), compared with control fetuses (n = 8). Fetal blood levels of testosterone and inhibin A were also reduced (36% and 38%, respectively) in treated compared with control fetuses, whereas blood levels of luteinizing hormone and follicle-stimulating hormone were unchanged. Based on immunoexpression of anti-Müllerian hormone, cytochrome P450 side chain cleavage enzyme, and Leydig cell cytoplasmic volume, we conclude that the hormone changes in treated male fetuses probably result from the reduction in somatic cell numbers. This reduction could result from fetal growth restriction in male fetuses and/or from the lowered testosterone action; reduced immunoexpression of alpha-smooth muscle actin in peritubular cells and of androgen receptor in testes of treated animals supports the latter possibility. These findings indicate that exposure of the developing male sheep fetus to real-world mixtures of environmental chemicals can result in major attenuation of testicular development and hormonal function, which may have consequences in adulthood.

Postnatal developmental consequences of altered insulin sensitivity in female sheep treated prenatally with testosterone

Prenatally testosterone (T)-treated female sheep exhibit ovarian and endocrinological features that resemble those of women with polycystic ovarian syndrome (PCOS), which include luteinizing hormone excess, polyfollicular ovaries, functional hyperandrogenism, and anovulation. In this study, we determined the developmental impact of prenatal T treatment on insulin sensitivity indexes (ISI), a variable that is affected in a majority of PCOS women. Pregnant ewes were treated with 60 mg testosterone propionate intramuscularly in cottonseed oil two times a week or vehicle [control (C)] from days 30 to 90 of gestation. T-females weighed less than C-females or males (P < 0.05) at birth and at 5 wk of age. T-females had an increased anogenital ratio. An intravenous glucose tolerance test followed by an insulin tolerance test conducted after an overnight fast at 5, 20, and 30 wk of age (n = 7-8/group) revealed that ISI were higher at 5 than 30 wk of age in C-females, reflective of a developing insulin resistance associated with puberty. T-females had higher basal insulin levels, higher fasting insulin-to-glucose ratio, and higher incremental area under the insulin curve to the glucose challenge. The ISI of T-females was similar to that of males. No differences in ISI were evident between groups at 20 and 30 wk of age. Mean basal plasma glucose concentrations and glucose disappearance and uptake did not differ between groups at any age. Our findings suggest that prenatal T treatment leads to offspring with reduced birth weight and impaired insulin sensitivity in early postnatal life.

Timing of prenatal androgen exposure: anatomical and endocrine effects on juvenile male and female rhesus monkeys

Prenatal androgen shapes genital differentiation. In humans, genital anatomy determines sex of rearing and subsequent behavioral development. Rhesus monkey genital anatomy and neuroendocrine function are sexually differentiated, and behavioral development occurs in a complex social environment. We investigated prenatal hormonal influences on sexual differentiation by suppressing or increasing androgens in male and female rhesus monkeys. Pregnant multiparous female rhesus monkeys received 35-40 days of testosterone enanthate (TE) treatment, androgen antagonist (flutamide, FL) treatment, or vehicle starting on gestation day (GD) 35 or 40 (early) or GD 110 or 115 (late). Exogenous androgen increased neonatal LH secretion in females when given early and altered female genital differentiation when administered either early or late. TE treatment, early or late in gestation, had no measurable effects on male genital differentiation or neuroendocrine function. Early FL treatment, however, radically altered male genital differentiation, producing in two cases males with a urethral opening separate from the glans. In females, early FL treatment produced detectable alterations in genitalia consistent with a reduced exposure to prenatal androgen, suggesting that female rhesus monkeys are naturally exposed prenatally to meaningful levels of T. Late FL treatment reduced male penis size and increased neonatal T secretion, but had no effect in females. This is the first study to block endogenous prenatal testosterone in rhesus monkeys, thereby altering sexual differentiation. These findings illustrate the complexity of prenatal influences on anatomical and neuroendocrine development. The relationship between the anatomical changes reported here and sex differences in behavior is currently under investigation.