Human placenta and fetal membranes contain peptide YY1-36 and peptide YY3-36

The relationship between gut and adipose hormones, and reproduction

BACKGROUND

Reproductive function is tightly regulated by nutritional status. Indeed, it has been well described that undernutrition or obesity can lead to subfertility or infertility in humans. The common regulatory pathways which control energy homeostasis and reproductive function have, to date, been poorly understood due to limited studies or inconclusive data. However, gut hormones and adipose tissue hormones have recently emerged as potential regulators of both energy homeostasis and reproductive function.

METHODS

A PubMed search was performed using keywords related to gut and adipose hormones and associated with keywords related to reproduction.

RESULTS

Currently available evidence that gut (ghrelin, obestatin, insulin, peptide YY, glucagon-like peptide-1, glucose-dependent insulinotropic peptide, oxyntomodulin, cholecystokinin) and adipose hormones (leptin, adiponectin, resistin, omentin, chemerin) interact with the reproductive axis is presented. The extent, site and direction of their effects on the reproductive axis are variable and also vary depending on species, sex and pubertal stage.

CONCLUSIONS

Gut and adipose hormones interact with the reproductive axis as well as with each other. While leptin and insulin have stimulatory effects and ghrelin has inhibitory effects on hypothalamic GnRH secretion, there is increasing evidence for their roles in other sites of the reproductive axis as well as evidence for the roles of other gut and adipose hormones in the complex interplay between nutrition and reproduction. As our understanding improves, so will our ability to identify and design novel therapeutic options for reproductive disorders and accompanying metabolic disorders.

Peptide YY (PYY) gene polymorphisms in the 3'-untranslated and proximal promoter regions regulate cellular gene expression and PYY secretion and metabolic syndrome traits in vivo

RATIONALE

Obesity is a heritable trait that contributes to hypertension and subsequent cardiorenal disease risk; thus, the investigation of genetic variation that predisposes individuals to obesity is an important goal. Circulating peptide YY (PYY) is known for its appetite and energy expenditure-regulating properties; linkage and association studies have suggested that PYY genetic variation contributes to susceptibility for obesity, rendering PYY an attractive candidate for study of disease risk.

DESIGN

To explore whether common genetic variation at the human PYY locus influences plasma PYY or metabolic traits, we systematically resequenced the gene for polymorphism discovery and then genotyped common single-nucleotide polymorphisms across the locus in an extensively phenotyped twin sample to determine associations. Finally, we experimentally validated the marker-on-trait associations using PYY 3'-untranslated region (UTR)/reporter and promoter/reporter analyses in neuroendocrine cells.

RESULTS

Four common genetic variants were discovered across the locus, and three were typed in phenotyped twins. Plasma PYY was highly heritable (P < 0.0001), and genetic pleiotropy was noted between plasma PYY and body mass index (BMI) (P = 0.03). A PYY haplotype extending from the proximal promoter (A-23G, rs2070592) to the 3'-UTR (C+1134A, rs162431) predicted not only plasma PYY (P = 0.009) but also other metabolic syndrome traits. Functional studies with transfected luciferase reporters confirmed regulatory roles in altering gene expression for both 3'-UTR C+1134A (P < 0.001) and promoter A-23G (P = 0.0016).

CONCLUSIONS

Functional genetic variation at the PYY locus influences multiple heritable metabolic syndrome traits, likely conferring susceptibility to obesity and subsequent cardiorenal disease.

Food-intake-regulating-neuropeptides are expressed and regulated through pregnancy and following food restriction in rat placenta

BACKGROUND

Neuropeptide Y (NPY), agouti related peptide (AgRP), cocaine and amphetamine-regulated transcript (CART) and melanocortins, the products of the proopiomelanocortin (POMC), are hypothalamic peptides involved in feeding regulation and energy homeostasis. Recent evidence has demonstrated their expression in rat and human placenta.

METHODS

In the current study, we have investigated the expression of those neuropeptides in the rat placenta by real-time PCR using a model of maternal food restriction.

RESULTS

Our results showed that placental-derived neuropeptides were regulated through pregnancy and following food restriction.

CONCLUSION

These data could indicate that placental-derived neuropeptides represent a local regulatory circuit that may fine-tune control of energy balance during pregnancy.

Peptide YY (3-36) represents a high percentage of total PYY immunoreactivity in preterm and full-term infants and correlates independently with markers of adiposity and serum ghrelin concentrations

The gut hormone peptide YY 3-36 [PYY (3-36)] has been suggested to posses anorexigenic actions in animals and human adults. However, its circulating concentrations and function have not been studied in neonates. Serum concentrations of PYY (3-36) were determined by RIA (RIA) in 62 healthy preterm infants [mean(SD) gestational age, 32.0(2.1) weeks; postnatal age, 40.9(14.8 d)] and 15 healthy fullterm infants of comparable postnatal age and gender. The correlations between PYY (3-36) levels and anthropometric characteristics, food intake, growth rates and circulating concentrations of total PYY, ghrelin, leptin, insulin and adiponectin were examined. Mean (SD) PYY (3-36) concentrations were higher in preterm [543.7(157.6) ng/L) than full term infants [350.9(114.1) ng/L; p < 0.001) and accounted for 48% and 42% of total PYY basal plasma immunoreactivity in preterm and full term infants, respectively. In multiple regression analysis, PYY (3-36) concentrations correlated negatively with the infants' BMI and positively with serum ghrelin concentrations, but not with caloric intake, weight gain or concentrations of any other hormone studied. In conclusion, PYY (3-36) represents almost half of total PYY immunoreactivity in neonates. It's correlations with ghrelin and BMI suggest a role of this peptide in the regulation of energy homeostasis; however, its specific functions and physiologic significance in neonates remain to be elucidated.

Stimulatory effect of PYY-(3-36) on gonadotropin secretion is potentiated in fasted rats

Development and normal function of the reproductive axis requires a precise degree of body energy stores. Polypeptide YY-(3-36) [PYY-(3-36)] is a gastrointestinal secreted molecule recently shown to be involved in the control of food intake with agonistic activity on neuropeptide Y (NPY) receptor subtypes Y2 and Y5. Notably, PYY-(3-36) has been recently demonstrated as putative regulator of gonadotropin secretion in the rat. However, the "reproductive" facet of this factor remains to be fully elucidated. In this context, we report herein our analyses of the influence of the nutritional status on the effects of PYY-(3-36) upon GnRH and gonadotropin secretion. The major findings of our study are 1) the stimulatory effect of central administration of PYY-(3-36) on LH secretion was significantly enhanced after fasting and blocked by a GnRH antagonist; 2) besides central effects, PYY-(3-36) elicited LH and FSH secretion directly at the pituitary level, a response that is also augmented by fasting; 3) PYY-(3-36) inhibited GnRH secretion by hypothalamic fragments from male rats fed ad libitum, whereas a significant stimulatory effect was observed after fasting; and 4) the increase in the gonadotropin responsiveness to PYY-(3-36) in fasting was not associated with changes in the expression of Y2 and Y5 receptor genes at hypothalamus and/or pituitary. In conclusion, our study extends our previous observations suggesting a relevant, mostly stimulatory, role of PYY-(3-36) in the control of gonadotropin secretion. Strikingly, such an effect was significantly enhanced by fasting. Considering the proposed decrease in PYY-(3-36) levels after fasting, the possibility that reduced PYY-(3-36) secretion might contribute to defective function of the gonadotropic axis after food deprivation merits further investigation.

Interactions of the hormones leptin, ghrelin, adiponectin, resistin, and PYY3-36 with the reproductive system

OBJECTIVE

To summarize the effects of novel hormones (leptin, ghrelin, adiponectin, resistin, and PYY3-36) secreted from adipose tissue and the gastrointestinal tract that have been discovered to exert different effects on several reproductive functions, such as the hypothalamic-pituitary-gonadal axis, embryo development, implantation physiology, and clinically relevant conditions.

DESIGN

A MEDLINE computer search was performed to identify relevant articles.

RESULT(S)

Leptin and ghrelin exert important roles on body weight regulation, eating behavior, and reproduction, acting on the central nervous system and target reproductive organs. As a marker of adequate nutritional stores, these hormones may act on the central nervous system to initiate the complex process of puberty and maintain normal reproductive function. In addition, leptin and ghrelin and their receptors are involved in reproductive events such as gonadal function, embryo development, and embryo-endometrial interaction.

CONCLUSION(S)

Leptin and ghrelin and other adipose tissue-secreted hormones have significant effects on reproduction. Acting through the brain, these hormones may serve as links between adipose tissue and the reproductive system to supply and regulate energy needs for normal reproduction and pregnancy. Future studies are needed to further clarify the role of these hormones in reproductive events and other related gynecological conditions.

Structure and receptor binding of PYY analogs

Differences in the structure of PYY and two important analogs, PYY [3-36] and [Pro34]PYY, are evaluated. Y-receptor subtype ligand binding data are used in conjunction with structural data to develop a model for receptor subtype selective agonists. For PYY it is proposed that potent binding to Y1, Y4 and Y5 receptors requires the juxtaposition of the two termini while Y2 binding only requires the C-terminal helix. Further experiments that delineate between primary and tertiary structure contributions for receptor binding and activation are required to support the hypothesis that tertiary structure is stable enough to influence the expression of PYY's bioactivity.