Estrogen replacement therapy increases plasma ghrelin levels

Circulating ghrelin levels in girls with central precocious puberty are reduced during treatment with LHRH analog

Decreased levels of ghrelin have been measured in growing children during puberty. No data are available for girls with central precocious puberty (CPP).

AIMS

To explore ghrelin changes before, during, and after GnRH analog treatment in girls with CPP.

SUBJECTS AND METHODS

A sample of 20 Caucasian girls (8.08 +/- 0.65 years of age) with CPP was recruited. Height and weight, bone age, LH, FSH, 17beta estradiol (E(2)), and ghrelin were measured before starting treatment with GnRH analog, 18 months after therapy began and again 6 months after therapy discontinuation.

RESULTS

LH and E(2) serum levels decreased significantly during treatment (2.45 +/- 2.03 vs 0.67 +/- 0.49 UI/l, P < 0.01 and 28.17 +/- 9.7 vs 15 pmol/l, P < 0.01 respectively), returning to baseline levels after the discontinuation of therapy (4.75 +/- 1.66 UI/l and 29.23 +/- 6.99 pmol/l respectively). LH peaked following LHRH stimulation significantly (P < 0.01) decreased during treatment (24.45 +/- 14.17 vs 1.3 +/- 0.18 UI/l) and then increased after therapy discontinuation (12.58 +/- 6.09, P < 0.01). Ghrelin decreased significantly (P < 0.05) during treatment (1849 +/- 322 vs 1207 +/- 637 pg/ml), and increased, though not significantly (P = 0.09) after therapy withdrawal (1567 +/- 629 pg/ml).

CONCLUSIONS

Contrary to what is expected in physiologic puberty, where ghrelin is progressively reduced, the prepubertal hormone milieau induced by GnRHa treatment in patients suffering from central precocious puberty (CPP) did not promote an increase in ghrelin circulating levels. Therefore, in CPP, ghrelin secretion seems to be independent from pubertal development per se. Concomitant estrogen suppression during treatment may play a potential role in the regulation of ghrelin secretion in these girls.

Estradiol potentiates ghrelin-stimulated pulsatile growth hormone secretion in postmenopausal women

CONTEXT

Ghrelin and an estrogen-rich milieu individually amplify pulsatile GH secretion by increasing the amount of hormone released per burst. However, how these distinct agonists interact in controlling pulsatile GH output is not known.

OBJECTIVE

The objective of the study was to test the hypothesis that elevated estradiol (E(2)) concentrations potentiate hypothalamo-pituitary responses to a near-physiological ghrelin stimulus.

DESIGN

This was a double-blind, placebo-controlled, prospectively randomized, parallel-cohort study.

SETTING

The study was conducted at an academic medical center.

SUBJECTS

Twenty-one postmenopausal women participated in the study.

INTERVENTIONS

Eleven subjects received placebo (Pl) and 10 others E(2) transdermally in escalating doses over 3 wk to mimic late follicular-phase E(2) concentrations. Saline or a submaximally stimulatory amount of ghrelin (0.3 microg/kg) was infused iv on separate randomly ordered mornings fasting after 17-21 d of Pl or E(2) administration.

OUTCOMES

Outcomes included serum concentrations of E(2), ghrelin, GH, IGF-I, IGF binding protein (IGFBP)-1 and IGFBP-3, and the estimated mass and waveform of stimulated GH secretory bursts.

RESULTS

Administration of E(2) yielded late follicular-phase E(2) concentrations. Compared with Pl, E(2) did not alter ghrelin concentrations but reduced IGF-I and IGFBP-3 and elevated IGFBP-1 concentrations. Compared with saline, ghrelin infusion amplified pulsatile GH secretion by 7.1-fold (P < 0.01). The effect of E(2) alone was 2.0-fold placebo and that of combined ghrelin/E(2) 10.4-fold (P < 0.01). Ghrelin and E(2) accelerated initial GH release individually but nonadditively by more than 2-fold (P < 0.01).

CONCLUSIONS

Estrogen augments ghrelin's near-physiological stimulation of pulsatile GH secretion and mimics ghrelin's acceleration of initial GH release. Thus, we hypothesize that estrogen and a GH secretagogue act via independent as well as convergent mechanisms.

Soy isoflavones increase preprandial peptide YY (PYY), but have no effect on ghrelin and body weight in healthy postmenopausal women

Background

Soy isoflavones show structural and functional similarities to estradiol. Available data indicate that estradiol and estradiol-like components may interact with gut "satiety hormones" such as peptide YY (PYY) and ghrelin, and thus influence body weight. In a randomized, double-blind, placebo-controlled, cross-over trial with 34 healthy postmenopausal women (59 ± 6 years, BMI: 24.7 ± 2.8 kg/m²), isoflavone-enriched cereal bars (50 mg isoflavones/day; genistein to daidzein ratio 2:1) or non-isoflavone-enriched control bars were consumed for 8 weeks (wash-out period: 8-weeks). Seventeen of the subjects were classified as equol producers. Plasma concentrations of ghrelin and PYY, as well as energy intake and body weight were measured at baseline and after four and eight weeks of each intervention arm.

Results

Body weight increased in both treatment periods (isoflavone: 0.40 ± 0.94 kg, P < 0.001; placebo: 0.66 ± 0.87 kg, P = 0.018), with no significant difference between treatments. No significant differences in energy intake were observed (P = 0.634). PYY significantly increased during isoflavone treatment (51 ± 2 pmol/L vs. 55 ± 2 pmol/L), but not during placebo (52 ± 3 pmol/L vs. 50 ± 2 pmol/L), (P = 0.010 for treatment differences, independent of equol production). Baseline plasma ghrelin was significantly lower in equol producers (110 ± 16 pmol/L) than in equol non-producers (162 ± 17 pmol/L; P = 0.025).

Conclusion

Soy isoflavone supplementation for eight weeks did not significantly reduce energy intake or body weight, even though plasma PYY increased during isoflavone treatment. Ghrelin remained unaffected by isoflavone treatment. A larger and more rigorous appetite experiment might detect smaller differences in energy intake after isoflavone consumption. However, the results of the present study do not indicate that increased PYY has a major role in the regulation of body weight, at least in healthy postmenopausal women.

Estrogen and ghrelin decrease cytoplasmic expression of p27kip1, a cellular marker of ageing, in the striated anal sphincter and levator muscle of ovariectomized rats

A study was carried out to investigate the effect of estrogen and/or ghrelin on the cellular marker of ageing, p27kip1, in pelvic floor muscles of ovariectomized rats. Virgin Wistar rats (13 months old) underwent ovariectomy followed (1 month) by 42 daily intraperitoneal 17-beta estradiol (10 microg/kg), ghrelin (2 microg/kg), both hormones, or placebo vehicle (n=6x4 groups). Six more age-matched animals underwent sham surgery without ovariectomy. Cytoplasmic expression of p27kip1 in the striated urethral and anal sphincters and levator muscle was measured by Western blot analysis in all animals (n=30). p27kip1 signal intensity significantly increased postovariectomy in all muscles compared to sham animals. In the anal sphincter and levator, signal intensity decreased to sham levels with ghrelin or estrogen and decreased further after estrogen or ghrelin and estrogen/ghrelin administration. Urethral sphincter signal intensity decreased without reaching sham levels after drug administration. Estrogen and/or ghrelin replacement reverses the ovariectomy-induced exacerbation of biochemical cellular ageing in the anal sphincter and levator muscle of middle-aged rats.

Plasma ghrelin concentrations are positively associated with carotid artery atherosclerosis in males

BACKGROUND

Ghrelin, a peptide hormone from stomach, stimulates food intake and decreases fat utilization. Ghrelin binds to growth hormone secretagogue receptor (GHSR). GHSR density has been shown to be upregulated in atherosclerotic lesions, but the relationship between ghrelin concentration and atherosclerosis has not yet been studied. We, therefore, characterized the association between ghrelin concentration and carotid artery intima-media thickness (IMT) in a population-based cohort of 1024 middle-aged (40-60 years) men and women.

METHODS

Intima-media thickness and the number of atherosclerotic plaques were determined ultrasonographically. Fasting plasma ghrelin concentrations were analysed using RIA-kit (PhoenixPeptide).

RESULTS

There was a positive association between mean IMT and ghrelin concentration in the analysis of males before and after adjustments for the traditional risk factors of atherosclerosis [age, systolic blood pressure, LDL cholesterol, body mass index (BMI), and smoking (ancova, P = 0.004 and P = 0.007, respectively)]. However, no such association was found in females (P = 0.985 and P = 0.915). There was no correlation between ghrelin and CRP concentrations or ghrelin and smoking.

CONCLUSION

Ghrelin concentrations and carotid artery atherosclerosis are positively associated in males even after adjustment for the commonly recognized risk factors of atherosclerosis. Experimental and prospective studies are warranted to elucidate the role of ghrelin in atherosclerosis.

Ghrelin is expressed in trigeminal neurons of female mice in phase with the estrous cycle

Several disorders mediated by the trigeminal nerve including migraine and temporomandibular disorder (TMD) are more common in women than in men, and painful attacks are often linked to the menstrual cycle. Estrogen receptors in trigeminal neurons may be involved in regulating neuronal function, causing changes in sensitivity that contribute to these attacks. In a previous study, we demonstrated that expression of specific neuropeptides including galanin and neuropeptide Y in trigeminal ganglia of female rodents varies with the estrous cycle. In this study, we examined expression of the orexigenic peptide ghrelin in trigeminal ganglia of cycling female mice. RT-PCR studies demonstrated that ghrelin mRNA is upregulated by over 5-fold at the high estrogen stages of the cycle, proestrus and early estrus over the levels expressed at the low estrogen stage of the cycle, diestrus. Double-labeling immunohistochemical studies and cell size measurements were conducted to identify the phenotype of neurons in trigeminal ganglia containing ghrelin. Ghrelin was present in trigeminal neurons containing peripherin, a marker of neurons with unmyelinated axons, in trigeminal neurons binding IB4, a marker of nonpeptidergic nociceptors, in trigeminal neurons containing neurofilament H, a marker of neurons with myelinated axons, and in trigeminal neurons containing the neuropeptide calcitonin gene-related peptide (CGRP). Ghrelin-positive neurons averaged 25.6 microm in diameter, but included neurons in all the size ranges except the smallest peripherin-positive neurons. Thus, nearly all of the major populations of trigeminal neurons including peptidergic and nonpeptidergic nociceptors contain ghrelin. These studies suggest that ghrelin, a multifunctional peptide, may contribute to the mechanism linking orofacial pain syndromes in females, including temporomandibular disorder and migraine, to cyclical hormonal changes.