Modulation Of Reproductive Function Research Articles

Alimentary infertility in female cattle: Part ІІІ – the modulation of reproductive function with vitamins and plant derivatives (Overview)

Alimentary infertility in female cattle: Part ІІІ – the modulation of reproductive function with vitamins and plant derivatives (Overview)

The Male Athlete Triad-A Consensus Statement From the Female and Male Athlete Triad Coalition Part 1: Definition and Scientific Basis.

The Male Athlete Triad is a syndrome of 3 interrelated conditions most common in adolescent and young adult male endurance and weight-class athletes and includes the clinically relevant outcomes of (1) energy deficiency/low energy availability (EA) with or without disordered eating/eating disorders, (2) functional hypothalamic hypogonadism, and (3) osteoporosis or low bone mineral density with or without bone stress injury (BSI). The causal role of low EA in the modulation of reproductive function and skeletal health in the male athlete reinforces the notion that skeletal health and reproductive outcomes are the primary clinical concerns. At present, the specific intermediate subclinical outcomes are less clearly defined in male athletes than those in female athletes and are represented as subtle alterations in the hypothalamic-pituitary-gonadal axis and increased risk for BSI. The degree of energy deficiency/low EA associated with such alterations remains unclear. However, available data suggest a more severe energy deficiency/low EA state is needed to affect reproductive and skeletal health in the Male Athlete Triad than in the Female Athlete Triad. Additional research is needed to further clarify and quantify this association. The Female and Male Athlete Triad Coalition Consensus Statements include evidence statements developed after a roundtable of experts held in conjunction with the American College of Sports Medicine 64th Annual Meeting in Denver, Colorado, in 2017 and are in 2 parts-Part I: Definition and Scientific Basis and Part 2: The Male Athlete Triad: Diagnosis, Treatment, and Return-to-Play. In this first article, we discuss the scientific evidence to support the Male Athlete Triad model.

Socio-Ecological Challenges as Modulators of Women's Reproductive Trajectories

Amenorrhea, anovulatory cycles, miscarriages, and other reproductive outcomes are often seen as pathological. Life history theory, in contrast, treats those outcomes as adaptations that helped women optimize the timing of reproductive ventures across our evolutionary history. Women's bodies adjust their reproductive strategies in response to socio-ecological conditions, a process mediated by the hypothalamic-pituitary-adrenal axis (HPAA). Here, we review the links between socio-ecological conditions, HPAA activity, and the pace of women's reproductive transitions such as puberty, age at first birth, interbirth interval, and perimenopause. We also discuss the HPAA's role as a modulator of reproductive function: It not only suppresses it but may also prime women's bodies for future reproductive ventures. We conclude by reviewing challenges and opportunities within our subfield, including the need for transdisciplinary teams to develop longitudinal studies to improve our understanding of women's reproductive trajectories and outcomes from the moment they are conceived.

Nutritional influences on reproduction in mature male sheep and goats

Changes in the nutrition of mature rams and goat bucks lead to profound responses in testicular size and therefore the rate of production of spermatozoa. These effects are largely due to changes in the size of the seminiferous tubules and in the efficiency of spermatogenesis. With the exception of severe undernutrition, the effects on spermatogenic function are not accompanied by similar changes in endocrine function of the testes, as measured by the production of testosterone or inhibin. In rams, moderate changes in nutrition affect gonadotrophin secretion for only a few weeks, whereas testicular growth is affected for several months. In mature male goats during the non-breeding season, nutrition-induced testicular growth does not seem to be associated with a gonadotrophin response. Such observations have led us to develop the hypothesis that nutrition-driven testicular growth is at least partly independent of changes in gonadotrophin secretion. The energetic components of the diet, rather than the protein content, seem to be responsible for affecting gonadotrophin secretion in rams. The volatile fatty acids, and not glucose, are the active factors, although intracerebral insulin may also play a role. Where these substrates act and whether they are also involved in the gonadotrophin-independent pathways requires testing. In conclusion, nutritional signals exert powerful effects on the reproductive system of mature male ruminants, and the responses are partly independent of changes in gonadotrophin secretion. In the gonads, the gametogenic tissue responds rapidly to changes in nutrition, but the endocrine compartments are less affected. Variations in the expression of the nutritional responses among sexes, breeds and species probably reflect variations in the role of this environmental factor as a modulator of reproductive function.

Spontaneous endogenous pulsatile release of kisspeptin is temporally coupled with luteinizing hormone in healthy women

To evaluate the presence of a spontaneous pulsatile release of kisspeptin and whether it is temporally coupled to LH pulses. Experimental study. Academic medical center. Thirty young healthy eumenorrheic women aged 20-37years were included in the study group. All subjects were white women admitted to the Department of Gynecological Endocrinology, Poznan University of Medical Sciences, Poznan, Poland. Kisspeptin, FSH, LH, E2, PRL, and insulin were evaluated in all subjects at baseline. All women underwent a pulsatility study measuring LH and kisspeptin plasma concentrations to assess the spontaneous episodic secretion of both hormones, sampling every 10minutes for 2hours from 9:00 to 11:00 a.m. for a total of 12 blood samples. Detection and specific concordance (SC) algorithms were used to detect pulses and their concordance. A significant endogenous secretory pattern was demonstrated for both LH and kisspeptin over the 2-hour duration of the study (2.4 ± 0.1 peaks/2h). The computation of the SC index showed for the first time that kisspeptin and LH are cosecreted and temporally coupled at time "0," and their peaks occur at the same point in time. The present study provides evidence supporting the hypothesis that kisspeptin is highly relevant in the regulation and modulation of reproductive functions in humans.

The involvement of gonadotropin inhibitory hormone and kisspeptin in the metabolic regulation of reproduction.

Recently, kisspeptin (KP) and gonadotropin inhibitory hormone (GnIH), two counteracting neuropeptides, have been acknowledged as significant regulators of reproductive function. KP stimulates reproduction while GnIH inhibits it. These two neuropeptides seem to be pivotal for the modulation of reproductive activity in response to internal and external cues. It is well-documented that the current metabolic status of the body is closely linked to its reproductive output. However, how reproductive function is regulated by the body's energy status is less clear. Recent studies have suggested an active participation of hypothalamic KP and GnIH in the modulation of reproductive function according to available metabolic cues. Expression of KISS1, the KP encoding gene, is decreased while expression of RFRP (NPVF), the gene encoding GnIH, is increased in metabolic deficiency conditions. The lower levels of KP, as suggested by a decrease in KISS1 gene mRNA expression, during metabolic deficiency can be corrected by administration of exogenous KP, which leads to an increase in reproductive hormone levels. Likewise, administration of RF9, a GnIH receptor antagonist, can reverse the inhibitory effect of fasting on testosterone in monkeys. Together, it is likely that the integrated function of both these hypothalamic neuropeptides works as a reproductive output regulator in response to a change in metabolic status. In this review, we have summarized literature from nonprimate and primate studies that demonstrate the involvement of KP and GnIH in the metabolic regulation of reproduction.

The expression of leptin receptor in the ovary of the queen: Leptin receptor expression in queen ovary

Leptin is a Ob gene product secreted mainly by adipose tissue. Several reports showed leptin production by other tissue including the ovary. The action of leptin is mediated upon binding to its receptor widely expressed in reproductive tissues in different species. In fact, there are growing evidences that leptin plays an important role in the modulation of reproductive functions. Therefore, the aim of this study was to evaluate in the queen, the expression of leptin receptor during the functional ovarian cycle and pregnancy. We found that the ovaries of the queen express leptin receptor in all the examined phases. The highest leptin receptor expression was found in the luteal phase (pseudopregnancy, pregnancy) compared to other phases of the cycle (anestrus, proestrus, estrus). The variations in the expression of leptin receptor suggest a likely implication of leptin in the modulation of ovarian activity, in the examined species.

The role of the leptin in reproduction

Since its discovery in 1994, leptin has appeared to be a pleiotrophic hormone, governing energy homeostasis and affecting many tissues in the body. Numerous pieces of evidence have accumulated showing that leptin potentially plays an important role in the control of the reproductive function. This review presents the major concepts for the role of leptin in the modulation of reproductive function. As a marker of the nutritional status, leptin affects the hypothalamo-pituitary-gonadal axis, regulating gonadotrophin-releasing hormone and luteinising hormone secretion, and appears to be a permissive factor in the onset of the puberty. This protein and its receptor have been found in the reproductive tissues, indicating that this system could be also implicated in several processes such as embryo development, implantation and pregnancy. Moreover, disorders of the leptin system have been related to some reproductive pathologies such as pre-eclampsia and polycystic ovary syndrome. However, controversy surrounds several aspects of the action of leptin in reproduction that require a deeper investigation of this system. Results to date suggest that this system could be implicated in important reproductive processes such as embryonic development and implantation. Moreover, understanding the role of leptin might be useful for new treatments in reproductive pathologies.

Seasonal variation and opioidergic regulation of growth hormone release in cyclic, ovariectomized, and pregnant pony mares.

Modulation of reproductive functions is one of the multiple effects of growth hormone (GH). To investigate effects of reproductive functions on GH release in the horse, plasma GH concentrations in ovary-intact (n = 7) and ovariectomized (n = 8) mares during the anovulatory and breeding seasons and in pregnant mares (n = 6) at various stages of gestation were determined. To analyze an opioidergic regulation of GH release, repeated blood samples were taken over 3 h, and mares were injected with the opioid antagonist naloxone (0.5 mg/kg i.v.) or saline. GH was determined by RIA with an antiserum raised against porcine GH and equine GH as standard. In ovariectomized and ovary-intact, cyclic mares, GH concentrations were low and not different between the two groups in November and December. GH concentrations increased significantly (P < 0.05) in cyclic mares during May and June but were not affected by stage of the cycle and were low in ovariectomized mares. In pregnant mares, plasma GH concentrations remained high throughout pregnancy and did not decrease during winter but increased significantly (P < 0.05) postpartum. Naloxone induced a significant GH release in ovary-intact mares; this response was most pronounced (P < 0.05) during the breeding season. Naloxone did not affect GH in ovariectomized mares. During pregnancy, naloxone induced a significant release of GH around Day 280 (P < 0.05) but not at other times of pregnancy. In conclusion, GH release is influenced by season. The seasonal changes depend on ovarian factors, are absent in ovariectomized mares, and can be modulated by pregnancy. GH release is regulated at least in part by opioidergic pathways.

High levels of serum allopregnanolone in women with premature ovarian failure

The endocrine characteristics of patients with premature ovarian failure (POF) have not been fully elucidated. The aim of the present study was to evaluate whether steroidogenic activity in women with POF is different with respect to fertile and postmenopausal subjects.In particular, circulating levels of allopregnanolone, a neuroactive steroid involved in modulation of reproductive function in rats, have been evaluated and correlated with serum levels of Δ4 precursor (dehydroepiandrosterone sulfate (DHEAS)), A5 intermediates (androstenedione, 17-hydroxyprogesterone (17-OHP), progesterone) and final products (estradiol and testosterone) of androgens. Levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and sex hormone binding globulin (SHBG) were also determined. In all cases specific radioimmunological assays were used. Women with POF showed statistically significantly lower concentrations of 17-OHP, androstenedione and testosterone when compared to fertile controls, while no differences were found between women with POF and postmenopausal women. Serum DHEAS levels were similar in POF patients and in fertile controls and higher with respect to postmenopausal women. Serum allopregnanolone levels were significantly higher in women with POF than in postmenopausal and infertile women. A significant inverse correlation between allopregnanolone levels and menopausal age in patients with POF was observed while no significant correlation was found between allopregnanolone and progesterone, androstenedione, 17-OHP and testosterone levels. In conclusion, allopregnanolone is scarcely influenced by the reduction of ovarian and adrenal activity observed in POF.

Evidence for a role for the neurosteroid allopregnanolone in the modulation of reproductive function in female rats

The present study investigated the effect of allopregnanolone (5 alpha-pregnan-3 alpha-ol-20-one) or of passive immunoneutralization of brain allopregnanolone, the most potent steroid produced by neurons, on ovulation rate and sexual behavior in female rats. Allopregnanolone was injected intracerebroventricularly in rats on diestrus and proestrus and tests were done on estrus. The intracerebroventricular injection of allopregnanolone significantly decreased the number of oocytes collected on estrus (p < 0.01). To support a physiological involvement, antiserum to allopregnanolone was injected centrally to block the activity of the endogenous neurosteroid. When administered on diestrus and proestrus or only on proestrus, the antiserum was shown to be correlated with a significant increase (p < 0.01) in oocytes retrieved on estrus. In female rats treated with antiserum to allopregnanolone, the lordosis intensity was augmented significantly as compared to controls. Finally, the possible changes of medial basal hypothalamus concentration of allopregnanolone throughout the estrous cycle and at the time of ovulation were investigated. Hypothalamic extracts were eluted on high-pressure liquid chromatography and allopregnanolone concentration was measured by radioimmunoassay. Brain cortex was used as control tissue. Hypothalamic allopregnanolone concentration on proestrus morning and afternoon was found to be significantly lower than in the remaining phases of the estrous cycle (p < 0.01), while no significant changes were observed in brain cortex concentration of allopregnanolone. The present results suggest that hypothalamic allopregnanolone may be involved in the mechanism of ovulation, affecting hormonal and behavioral events.

Effects of clomiphene citrate and leuprolide acetate on luteal-phase hyperprolactinemia during ovarian stimulation with menopausal gonadotropins

Hyperprolactinemia, a known modulator of reproductive function, occurs commonly in women undergoing ovarian stimulation with human menopausal gonadotropins (hMG). Clomiphene citrate (CC) and gonadotropin releasing hormone analogues (GnRHa), when administered during the luteal phase, attenuate the hyperprolactinemic response to hMG. We asked whether follicular-phase administration of CC and GnRHa, as employed clinically in women undergoing ovarian stimulation for in vitro fertilization or gamete intrafallopian transfer, would alter the incidence and severity of hMG-induced luteal-phase hyperprolactinemia. Seventy-five percent of all patients had at least one luteal prolactin level greater than 25 ng/ml, and 40% had mean luteal-phase prolactin levels greater than 25 ng/ml. The incidence of hyperprolactinemia was similar in pregnant and nonpregnant cycles. The incidence of hyperprolactinemia was similar for both the GnRH agonist-treated group and those given clomiphene citrate. The increase in mean luteal prolactin levels over the follicular-phase baseline level was significantly greater in the CC-treated group (P = 0.03). This was due to the significant suppression of follicular-phase baseline prolactin levels in patients receiving CC. We conclude that neither CC nor GnRHa administration in the follicular phase prevents luteal-phase hyperprolactinemia in women undergoing ovarian stimulation with hMG.

Serotonin binding sites during proestrus and following estradiol treatment

The binding of 3H-5-HT to hypothalamic, hippocampal and striatal membranes from female rats was examined. During the day of proestrus, there was a significant increase in binding from morning to evening. The increase reflected changes in both K d and B max. Effects of estradiol were examined in ovariectomized rats, and changes in 3H-5-HT binding resulted from an increase in the K d after estradiol treatment. These in vivo effects of estradiol were not seen when tissue was incubated in vitro with estradiol. However, the compound, polyvinylpyrrolidone, used in the in vitro incubation significantly increased the K d for binding to 3H-5-HT and estradiol attenuated the increase. The potential significance of these changes to serotonin's modulation of reproductive function is discussed.

Estrogen receptors in the male.

Estrogens in the male are secreted by the testes and derived extragonadally from the aromatization of certain androgens. In some brain regions critical for the control of gonadotropin secretion and behavior, androgens may be aromatized to estrogens within the cells that are regulated. Estrogen may have other physiological roles on the testes to control testosterone secretion and on accessory sex glands to promote both fibromuscular growth and secretion. High doses of estrogen given for treatment of prostatic cancer or modulation of reproductive function not only reduce testosterone secretion but also interact with the liver, changing the secretion of various plasma proteins and causing several undesirable side effects. The hypothalamus, pituitary, testes, accessory sex glands, and liver all contain an apparently identical protein, the estrogen receptor, which may mediate the actions of estrogen.