Pituitary galaninergic system activity in female rats: the regulatory role of gonadal steroids

The well-recognized sensitivity of the galanin gene in the anterior pituitary gland to estrogen suggests that estrogen receptor activity may influence the galaninergic system through modulation of galanin receptor (GALR) gene expression. Here, we evaluated the following: (i) the effects of estrogen on GALR mRNA expression; (ii) the estrogen receptor subtype that is specifically involved in this activity; and (iii) the effects of progesterone in the absence or presence of estrogen on galanin concentration in anterior pituitary gland. In the first experiment, ovariectomized 4-month-old rats were pre-treated subcutaneously with 17β-estradiol (3 x 20 μg), the ESR1 (ERα) agonist propyl pyrazole triol (PPT) (3 x 5 mg), and the ESR2 (ERβ) agonist diarylpropionitrile (DPN) (3 x 0.5 mg). In the second experiment, 4-month-old ovariectomized females received daily subcutaneous injections of 17β-estradiol (3 x 20 μg), progesterone (2 x 5 mg), or combined estradiol (3 x 20 μg) and progesterone (2 x 5 mg). Anterior pituitaries were excised the day after the final 17β-estradiol injection (experiment I) and 1 hour after receiving the second progesterone dose. Relative GALR1, GALR2, and GALR3 mRNA expression was evaluated using quantitative real-time PCR, and pituitary galanin concentration was determined using a specific radioimmunoassay. The results revealed that estrogen predominantly induced a 5-fold increase in GALR3 gene transcription. To a lesser extent, 17β-estradiol also increased GALR1 mRNA expression, but had no effect on GALR2 mRNA levels. The estrogen-induced increase in GALR3 gene expression occurred exclusively through ESR1 activation. The increase in GALR1 gene expression occurred through activation of both estrogen receptor subtypes, but the ESR2 subtype was predominantly involved. Furthermore, the results revealed that progesterone regulates the activity of the pituitary galaninergic system by facilitating estradiol-induced galanin synthesis in the female rat anterior pituitary gland.

The relationship between neuropeptides and hormones in starvation

OBJECTIVES

Some hormonal disturbances were demonstrated in starvation. Leptin, NPY and galanin play an important role in the control of appetite and in the mechanism of hormone release.

METHODS

In order to evaluate the effect of starvation on the relationship between leptin, neuropeptide Y (NPY) galanin and pituitary and gonadal hormones release, plasma leptin, NPY and galanin as well as serum LH, FSH, prolactin (PRL), estradiol, progesterone levels in non-starved female rats (in diestrus) and after 72 hrs of starvation were measured with RIA methods. Effects of leptin, NPY and galanin administration on pituitary and gonadal hormones were investigated in vivo and in vitro experiments.

RESULTS

Plasma leptin, NPY and galanin as well as serum estradiol and progesterone concentrations were significantly lower in starved rats as compared with non-starved rats. However serum prolactin level was significantly higher in starved rats. Opposite effects after leptin and NPY administration on hormone release in vivo and in vitro experiments were observed in non-starved rats. However, in starved rats we did not find changes in pituitary and gonadal hormones release after leptin, NPY and galanin injection or the hormonal response was blunted.

CONCLUSIONS

1) The disturbances in neuropeptides activity and in hormones release were observed in starvation. 2) Leptin, NPY and galanin have direct and indirect effects on pituitary and gonadal hormones release. 3) In starvation the hormonal response to leptin, NPY and galanin is impaired.

Plasma leptin, neuropeptide Y (NPY) and galanin concentrations in bulimia nervosa and in anorexia nervosa

OBJECTIVES

It has been reported that leptin and neuropeptide Y (NPY) play a role in the control of appetite and in the regulation of hormonal secretion.

METHODS

Plasma leptin, neuropeptide Y (NPY) and galanin concentrations were estimated in 13 women with bulimia nervosa (BN) 19 women with anorexia nervosa (AN) and in 19 healthy women of the control group (CG).

RESULTS

Plasma leptin concentration in BN was significantly higher than that in AN and it was lower as compared with the control group, despite the same BMI (body mass index) in both the groups. Plasma leptin level in AN was significantly lower as compared with the controls. Plasma galanin concentrations in AN and BN did not differ significantly from the control group. Plasma NPY concentration in AN was lower than that in the control group. However, plasma NPY level in BN was significantly higher as compared with AN and with the control group (CG). The observed increase of NPY in BN was independent of BMI because BMI in bulimia nervosa was normal.

CONCLUSIONS

The data may suggest that other factors than body weight changes may be involved in the modulation of leptin and NPY release in BN. The pathological behaviour of patients with bulimia nervosa may result from disturbed NPY release which is the strongest orexigenic factor.

Disturbed release of gastrointestinal peptides in anorexia nervosa and in obesity

AIM

It is commonly accepted that some neuropeptides play an important role in the control of appetite and hormonal secretion. Several gastrointestinal peptides may affect on central control of appetite via vagal and spinal nerves. The aim of this study was to evaluate the release of gastrointestinal peptides in anorexia nervosa and in obesity, because in these diseases the disturbances in the control of appetite and hormonal secretion were found. Material consisted of 30 women with anorexia nervosa aged 16-29 years (mean 22 years) and 23 women with obesity aged 19-33 years (mean 29 years) and 25 lean women of control group.

METHODS

In women with anorexia nervosa as compared with control group we observed a significant increase of plasma vasoactive intestinal peptide (VIP) levels (p < 0.01) and a significant decrease of leptin (p < 0.001), beta-endorphin (p < 0.01), gastrin (p < 0.05), cholecystokinin (CCK; p < 0.05) and somatostatin (S-S; p < 0.01). In obese women we found a significant increase of neuropeptide Y (NPY; p < 0.001), leptin (p < 0.01), galanin (p < 0.001), beta-endorphin (p < 0.001), gastrin (p < 0.01), CCK (p < 0.001) and S-S (p < 0.01) and a significant decrease of VIP concentrations (p < 0.001) as compared with control group.

CONCLUSION

Our results indicate that the release of gastrointestinal peptides is disturbed in obesity and in anorexia nervosa. These findings suggests that dysfunction of brain-gut axis may be also an important factor in the abnormal control of appetite axcept of hypothalamic dysfunction.