Neuroendocrinology of nutritional infertility

Wade, George N.; Jones, Juli E.

doi:10.1152/ajpregu.00475.2004

Cited by 229 publications

(176 citation statements)

References 267 publications

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“…Some studies pointed out that the higher the negative energy balance, the higher the probability of reproductive alterations (23)(24)(25), and our results agreed with this statement. When food is scarce, animals adjust their energetic priorities.…”

Section: Discussionsupporting

confidence: 91%

Effect of Food Restriction and Intense Physical Training on Estrous Cyclicity and Plasma Leptin Concentrations in Rats

Santos

Silva

Bacurau

et al. 2011

J Nutr Sci Vitaminol

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SummaryIntense physical training and dietary energy restriction have been associated with consequences such as nutritional amenorrhea. We investigated the effects of intense physical training, food restriction or the combination of both strategies on estrous cyclicity in female rats, and the relationship between leptin ad these effects. Twenty-seven female Wistar rats were distributed into four groups: SF: sedentary, fed ad libitum; SR: sedentary subjected to 50% food restriction (based on the food intake of their fed counterparts); TF: trained (physical training on a motor treadmill with a gradual increase in speed and time), fed ad libitum; TR: trained with 50% food restriction. We analysed estrous cyclicity, plasma leptin and estradiol as well as chemical composition of the carcass, body weight variation, and weight of ovaries and perirenal adipose tissue. Data demonstrate that physical training alone was not responsible for significant modifications in either carcass chemical composition or reproductive function. Food restriction reduced leptin levels in all animals and interrupted the estrous cyclicity in some animals, but only the combination of food restriction and physical training was capable of interrupting the estrous cyclicity in all animals. Leptin was not directly related to estrous cyclicity. From our findings, it may be concluded that there is an additive or synergistic effect of energy intake restriction and energy expenditure by intense physical training on estrous cyclicity. Leptin appears to be one among others factors related to estrous cycle, but it probably acts indirectly. Key Words energy intake, body composition, estrous cycle, leptin, physical exercise Some female athletes are constantly under pressure to achieve and/or to maintain low body weight, leading to potentially harmful patterns of restricted dieting and over exercising. Some of the health consequences of long-term energy restriction include poor nutritional status and risk of exercise-induced amenorrhea ( 1 , 2 ). In humans, this condition is characterized by the absence of menstruation for 90 d or more.Based on epidemiological data, Frisch ( 3 ) reported that, in women and girls, body fat content and ovulatory cyclicity were positively associated. However, one or more main signals that centrally indicates the availability of energy is still unknown ( 4 ). Since physical activity may reduce leptin mRNA expression ( 5 , 6 ) and athletes that train intensively, under restricted calorie intake, present a higher percentage of amenorrhea than sedentary women ( 7 ), it may be speculated that leptin is involved in the transduction of the energy availability signals.Studies on the effects of exercise, reproductive function and leptin response have been hindered by the inability to disassociate the effects of exercise itself from other confusing factors. These factors could be related to energy intake below the requirements or different hormones involved ( 8 , 9 ). It is not clear whether the reproductive functions are interrupted due...

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Section: Discussionsupporting

confidence: 91%

Effect of Food Restriction and Intense Physical Training on Estrous Cyclicity and Plasma Leptin Concentrations in Rats

Santos

Silva

Bacurau

et al. 2011

J Nutr Sci Vitaminol

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“…These neurochemical modulators allow the GnRH system to monitor the internal and external environments and adjust reproductive function according to current conditions. For example, during nutritional deficits, GnRH secretion is inhibited and reproduction is curtailed (32). Likewise, acute and chronic stress can have marked effects on GnRH secretion and reproductive function (33,34).…”

Section: Discussionmentioning

confidence: 99%

Identification and characterization of a gonadotropin-inhibitory system in the brains of mammals

Kriegsfeld

Mei

Bentley

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

493

642

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Successful reproduction requires maintenance of the reproductive axis within fine operating limits through negative feedback actions of sex steroids. Despite the importance of this homeostatic process, our understanding of the neural loci, pathways, and neurochemicals responsible remain incomplete. Here, we reveal a neuropeptidergic pathway that directly links gonadal steroid actions to regulation of the reproductive system. An RFamide (Arg-Phe-NH 2) peptide that inhibits gonadotropin release from quail pituitary was recently identified and named gonadotropin-inhibitory hormone (GnIH). Birds are known to have specialized adaptations associated with gonadotropin-releasing hormone (GnRH) regulation to optimize reproduction (e.g., encephalic photoreceptors), and the existence of a hypothalamic peptide inhibiting gonadotropins may or may not be another such specialization. To determine whether GnIH serves as a signaling pathway for sex steroid regulation of the reproductive axis, we used immunohistochemistry and in situ hybridization to characterize the distribution and functional role of this peptide in hamsters, rats, and mice. GnIH-immunoreactive (GnIH-ir) cell bodies are clustered in the mediobasal hypothalamus with pronounced projections and terminals throughout the CNS. In vivo GnIH administration rapidly inhibits luteinizing hormone secretion. Additionally, GnIH-ir neurons form close appositions with GnRH cells, suggesting a direct means of GnRH modulation. Finally, GnIH-ir cells express estrogen receptor-␣ and exhibit robust immediate early gene expression after gonadal hormone stimulation. Taken together, the distribution of GnIH efferents to neural sites regulating reproductive behavior and neuroendocrine secretions, expression of steroid receptors in GnIH-ir nuclei, and GnIH inhibition of luteinizing hormone secretion indicate the discovery of a system regulating the mammalian reproductive axis.luteinizing ͉ mating ͉ reproduction T he final common pathway in the neural regulation of reproduction is the gonadotropin-releasing hormone (GnRH) neuronal system. Neurons that synthesize and secrete GnRH occupy a midventral continuum from the diagonal band of Broca to the mediobasal hypothalamus (1). GnRH neurons regulating gonadotropin secretion project to the median eminence to control synthesis and secretion of the pituitary gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) (2-4).In both males and females, gonadal steroids act through negative feedback to maintain the reproductive axis within the favorable operating limits necessary for fertility and successful mating. Negative feedback control of the GnRH system could be accomplished by sex hormones acting on either cognate receptors expressed in GnRH neurons or on gonadal-steroid-responsive systems upstream of GnRH. Although early evidence before this millennium suggested only the latter (5-11), more recent evidence suggests that both of these mechanisms act in concert to regulate precisely the reproductive axis in females (12-1...

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“…The effects of negative energy balance on reproduction are primarily at the hypothalamo-pituitary level of reproductive control [8] and are characterised by hypoglycaemia, hypoinsulinaemia, suppressed plasma IGF-I and elevated plasma GH, changes that are associated with the inhibition of GnRH pulsatility, anovulation and anoestrus in the female. There is little evidence to suggest that negative energy balance has any direct ovarian effects in the ewe that are independent of its effects on the hypothalamo-pituitary axis [9,10].…”

Section: What Is the Relationship Between Nutrition And Reproduction?mentioning

confidence: 99%

“…Positive energy balance is also associated with alterations in the hepatic metabolism of steroids [13,14] that can lead to disturbances in negative feedback between the ovary and the hypothalamo-pituitary system and theoretically, to increased folliculogenesis. There is little evidence to suggest that positive energy balance has a specific stimulatory action on the hypothalamo-pituitary axis [8]. It is worth noting that because of the strong negative feedback interrelationship between the hypothalamo-pituitary axis and the ovary, the task of identifying the anatomical sites in the reproductive axis that are influenced by nutrition is proving to be exceedingly difficult.…”

Section: What Is the Relationship Between Nutrition And Reproduction?mentioning

confidence: 99%

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

Scaramuzzi¹,

Campbell²,

Downing³

et al. 2006

Reprod. Nutr. Dev.

315

223

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-This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition stimulates folliculogenesis and ovulation rate. In addition the paper reviews recent findings on the effects of increased levels of nutrition on the blood concentrations of reproductive and metabolic hormones in the ewe and some of the intraovarian changes that take place in response to nutritional stimulation. Finally, in the paper, we propose a model of the physiological mechanism for the nutritional stimulation of folliculogenesis and we review how closely the model fits recent published and unpublished evidence examining the mechanism of flushing. Nutritional stimulation alters the blood concentrations of some metabolic hormones. By using short-term models of nutritional flushing, we have shown that as the blood concentrations of insulin and leptin increase that of growth hormone decreases while that of IGF-I appears unaffected by the nutritional flushing. Nutritional flushing also alters the blood concentrations of some reproductive hormones. Again, using the same model, we have shown that there is a transient increase in FSH and a decrease in oestradiol concentrations in the blood. The changes in oestradiol are particularly evident in the follicular phase of the oestrous cycle. In the ovary, the effect of nutrition is to stimulate folliculogenesis. These changes are associated with intra-follicular alterations in the insulin-glucose, IGF and leptin metabolic systems. The stimulation of these intra-follicular systems leads to a suppression in follicular oestradiol production. The consequence of these direct actions on the follicle is a reduced negative feedback to the hypothalamic-pituitary system and increased FSH secretion that leads to a stimulation of folliculogenesis.insulin / leptin / IGF-I / glucose / FSH / oestradiol

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Neuroendocrinology of nutritional infertility

Cited by 229 publications

References 267 publications

Effect of Food Restriction and Intense Physical Training on Estrous Cyclicity and Plasma Leptin Concentrations in Rats

Effect of Food Restriction and Intense Physical Training on Estrous Cyclicity and Plasma Leptin Concentrations in Rats

Identification and characterization of a gonadotropin-inhibitory system in the brains of mammals

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

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