The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Roh, Sang Gun; Clarke, Iain J.; Xu, Ru Wei; Goding, James W.; Loneragan, Kylie; Chen, Chen

doi:10.1159/000054385

Cited by 51 publications

(36 citation statements)

References 17 publications

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“…Data from this laboratory (Roh et al 1998) show a negative effect of leptin on GHRH-stimulated GH secretion from somatotrophs in primary cultures and a large percentage (69%) of somatotrophs possess the leptin receptor (Iqbal et al 2000). It is possible that higher levels of leptin in ad lib animals act in a negative manner to regulate GH secretion at the level of the pituitary gland, leading to lower circulating levels of GH in this condition.…”

Section: Figurementioning

confidence: 92%

Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight

Henry

Goding

Tilbrook³

et al. 2001

Journal of Endocrinology

146

114

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Leptin can act as a satiety factor and exert neuroendocrine effects, but most studies have been performed in fasted animals. We aimed to determine the effect of chronic under-nutrition on the response to a 3-day intracerebroventricular infusion of leptin with regard to food intake and the secretion of pituitary hormones. Ovariectomised ewes (n=6) had a mean ( ...) bodyweight of 56 0·8 kg on a diet available ad libitum (ad lib) or 33·4 1 kg on a restricted diet. The differential bodyweight was achieved by dietary means over a period of 6 months prior to the commencement of the study. Leptin (4 µg/h) or vehicle (artificial cerebrospinal fluid (aCSF)) was infused into the third cerebral ventricle for 3 days. Blood samples were taken prior to commencement and on day 3 of infusion for the assay of plasma hormone levels. The experiment was repeated one week later in a crossover design. Food intake and metabolic status were monitored daily. The luteinising hormone (LH) pulse amplitude was lower (P<0·05) but plasma growth hormone (GH) levels were higher (P<0·05) in the food-restricted animals. Plasma levels of glucose, lactate, insulin, urea and triglycerides were similar in the two groups but nonesterified fatty acid levels were higher (P<0·01) in the animals on an ad lib diet. Leptin reduced (P<0·05) food intake only in the animals fed an ad lib diet. Leptin increased (P<0·05) the secretion of LH in the foodrestricted group only and increased (P<0·05) GH irrespective of bodyweight. In conclusion, leptin does not alter food intake in animals on a restricted diet but can increase the secretion of LH in the same animals. The treatment of leptin was not sufficient to reduce plasma GH levels in the food-restricted animals, suggesting that other factors or mechanisms must be involved in the regulation of this axis.

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Section: Figurementioning

confidence: 92%

Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight

Henry

Goding

Tilbrook³

et al. 2001

Journal of Endocrinology

146

114

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“…Leptin inhibits somatostatin gene expression and secretion in hypothalamic neurons (249). The leptin receptor is also expressed at the level of the pituitary gland, where leptin has been shown to speci®cally stimulate basal GH release (250,251). Moreover, the long form of the leptin receptor seems to be upregulated by growth hormone-releasing hormone (GHRH), as was shown in the pituitary gland of hGHRH transgenic mice (252).…”

Section: Leptin and The Gh Axismentioning

confidence: 96%

“…Central infusion of leptin to rats stimulates basal GH secretion (248,251,253,254). Administration of leptin antiserum to normal fed rats led to a decrease in spontaneous GH secretion (255).…”

Section: Leptin and The Gh Axismentioning

confidence: 99%

Human leptin: from an adipocyte hormone to an endocrine mediator

2000

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Leptin is a mainly adipocyte-secreted protein that was discovered 5 years ago. Most of the research following this discovery focused on the role of leptin in body weight regulation, aiming to illuminate the pathophysiology of human obesity. However, more and more data are emerging that leptin is not only important in the regulation of food intake and energy balance, but that it also has a function as a metabolic and neuroendocrine hormone. It is now clear that it is especially involved in glucose metabolism, as well as in normal sexual maturation and reproduction. Besides this, interactions with the hypothalamic±pituitary±adrenal, thyroid and GH axes and even with haematopoiesis and the immune system have also been described. It has been shown that leptin secretion by the adipocyte is partly regulated by other hormones, such as insulin, cortisol, and sex steroids, mainly testosterone. Also, other hormones like thyroid hormone and GH are possibly involved in leptin synthesis. Leptin itself exerts effects on different endocrine axes, mainly on the hypothalamic±pituitary±gonadal axis and on insulin metabolism, but also on the hypothalamic±pituitary±adrenal, thyroid and GH axes.Leptin may thus be considered a new endocrine mediator, besides its obvious role in body weight regulation.

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“…Expression of leptin receptor mRNA has been demonstrated in the anterior pituitary gland and hypothalamus by RT-PCR (Zamorano et al 1997), and leptin appears to have an important role in the control of growth hormone (GH) release (Roh et al 1998, Iqbal et al 2000.…”

Section: Introductionmentioning

confidence: 99%

Effects of leptin on basal and GHRH-stimulated GH secretion from the bovine adenohypophysis are dependent upon nutritional status

Zieba¹,

Amstalden²,

Morton³

et al. 2003

Journal of Endocrinology

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We have shown recently that leptin modulates at least two aspects of anterior pituitary LH release in ruminants: basal and GnRH-mediated release. To test the hypothesis that leptin directly affects basal and GHRH-mediated GH secretion from the adenohypophysis, we examined the effects of various doses of recombinant ovine leptin (oleptin) on perifused adenohypophyseal (AP) explants and compared responses of tissues from control and fasted cows. Ten mature, ovariectomized and estradiol-implanted cows were assigned to one of two dietary groups: (1) normal-fed (n=5) and (2) fasted for 72 h (n=5). At the end of the fasting period, cows were euthanized and pituitaries were collected. Adenohypophyseal explants were perifused for a total of 6·5 h, including a 2-h treatment at 2·5 h with Krebs-Ringer bicarbonate buffer containing 0, 5, 10, 50, or 100 ng/ml oleptin, and a challenge with GHRH at 4·5 h. All doses of oleptin greater than 5 ng/ml decreased (P,0·01) basal GH secretion compared with controls in tissues collected from normal-fed cows. In contrast, GH release from AP explants from fasted cows treated with the lowest dose of oleptin was 28% (P,0·002) higher than control explants, but larger doses had no effect. Leptin caused an inversely related, dose-dependent increase in GHRH-mediated GH release in tissues from normal-fed cows. Marked increases (P,0·01-P,0·001) in GH release were observed for the 5 and 10 ng/ml oleptin, with lesser (P,0·08) and no effects observed at the 50 and 100 ng/ml doses respectively. In fasted cows, oleptin had no stimulatory effect on GHRH-induced GH release. Results show that leptin can act directly at the anterior pituitary level to modulate GH release, and this effect is dependent upon nutritional history.

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The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Cited by 51 publications

References 17 publications

Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight

Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight

Human leptin: from an adipocyte hormone to an endocrine mediator

Effects of leptin on basal and GHRH-stimulated GH secretion from the bovine adenohypophysis are dependent upon nutritional status

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