Central effects of ghrelin on the adrenal cortex: a morphological and hormonal study

Abstract

Abstract. Ghrelin, a growth hormone secretagogue that exerts an important role in appetite and weight regulation, participates in the activation of the hypothalamo-pituitary-adrenal (HPA) axis. Male Wistar rats (5/group) received daily for 5 days, via an ICV (intracerebroventricular) cannula, 5 µl phosphate buffered saline with or without 1 µg of rat ghrelin. Two hours after the last injection, blood and adrenal glands were collected from decapitated rats for blood hormone analyses and histologic and morphometric processing. Ghrelin treatment resulted in increased (p < 0.05) body weight (13%), absolute whole adrenal gland weight (18%) and whole adrenal gland volume (20%). The absolute volumes of the entire adrenal cortex, ZG, ZF, and ZR also increased (p < 0.05) after ghrelin by 20%, 21%, 21% and 11%, respectively. Ghrelin-treated rats had elevated (p < 0.05) blood concentrations of ACTH, aldosterone and corticosterone (68%, 32% and 67%, respectively). The data clearly provide both morphological and hormonal status that ghrelin acts centrally to exert a global stimulatory effect on the adrenal cortex. Clarifying of the ghrelin precise role in the multiple networks affecting the stress hormone release, besides its well known energy and metabolic disbalance effects, remains a very important research goal.

Age-dependent modulation of central ghrelin effects on food intake and lipid metabolism in rats

“…Finally, while confirming the previously described HPA axisstimulating capacity of ghrelin (Milosevic et al, 2010;Mozid et al, 2003;Wren et al, 2002), our data for the first time reveal its increase with aging. As the well known stimulatory effects of cortisol/ corticosterone on blood triglycerides/cholesterol, lipolysis and adipogeneseis (van Raalte et al, 2009) have all been mirrored by ghrelin, it seems that the higher responsiveness of older animals to ghrelin in the present study could be at least in part mediated via HPA axis activation.…”

“…Importantly, the influence of age on the ability of ghrelin to modulate body weight and lipid metabolism has not been extensively investigated. In addition, although ghrelin is known to inhibit secretion of anorexigenic hormones insulin and leptin (Dezaki et al, 2008;Konturek et al, 2004) and stimulate the activity of hypothalamic-pituitaryadrenal (HPA) axis (Milosevic et al, 2010;Mozid et al, 2003;Wren et al, 2002), the age dependence of these effects has not been explored so far.…”

Aldosterone changes after consumption of a sodium-bicarbonated mineral water in humans. A four-way randomized controlled trial

“…This study demonstrates that aldosterone levels decreased with the four treatments. The meal effect can be explained, at least partially, by two factors, the digestive signals as it is known that several hormones decrease after eating, including ghrelin and aldosterone [14] and the 276 mg sodium provided by the standard meal, as aldosterone decreases after sodium intake [8].…”

The closed-loop pathways of signaling molecules

“…Retinoic acid signaling markedly stimulates natriuretic peptide receptor-A gene expression [24]. Moreover, it was found that ANP level decreases significantly after treatment with ghrelin in a rat model [25]; ghrelin elevates aldosterone [26]; and applying ghrelin supplementation to normal lungs increased retinoic acid receptor α/γ expression [27].…”