ghrelin secretion

Definition

Target type: biologicalprocess

The regulated release of ghrelin from a cell. Ghrelin is a 28 amino acid hunger-stimulating peptide hormone. [GOC:cjm, PMID:14610293, Wikipedia:Ghrelin]

Ghrelin secretion is a complex process that involves a series of steps initiated by the presence of an empty stomach. The primary site of ghrelin production is the stomach, specifically within the enteroendocrine cells known as X/A-like cells located in the gastric mucosa. These cells contain the gene encoding preproghrelin, which is processed into ghrelin through a series of enzymatic cleavages.

The process begins with the recognition of specific signals that indicate an empty stomach, such as the presence of low levels of nutrients in the stomach, distension of the stomach wall, or the absence of food-related stimuli. These signals activate a cascade of intracellular signaling pathways, primarily involving G protein-coupled receptors (GPCRs), which ultimately lead to the expression and release of ghrelin.

One of the key signaling pathways involved in ghrelin secretion is the GHSR (growth hormone secretagogue receptor) pathway. This pathway is activated by specific ligands, including ghrelin itself, leading to downstream signaling events that ultimately promote ghrelin release. Other signaling pathways involved include the NPY (neuropeptide Y) pathway and the orexin pathway, which contribute to the regulation of ghrelin secretion.

Once ghrelin is synthesized and processed within the X/A-like cells, it is packaged into secretory vesicles and transported to the cell membrane. These vesicles fuse with the membrane, releasing ghrelin into the bloodstream. Once in circulation, ghrelin travels to its target organs, including the hypothalamus, where it interacts with the GHSR to exert its various physiological effects.

Ghrelin secretion is tightly regulated by several factors, including nutritional status, circadian rhythms, and stress levels. For instance, fasting or prolonged periods without food consumption significantly increase ghrelin levels, while the presence of food in the stomach suppresses ghrelin secretion. Similarly, ghrelin levels fluctuate throughout the day, with higher levels typically observed in the morning before breakfast. Stressful events can also influence ghrelin secretion, often leading to increased levels.

The regulation of ghrelin secretion is essential for maintaining energy balance and regulating appetite. Ghrelin acts as a powerful hunger hormone, stimulating food intake and promoting energy storage. By increasing appetite, ghrelin ensures that the body receives the necessary nutrients for survival. Its role in energy homeostasis is further highlighted by its ability to stimulate the release of growth hormone, which plays a crucial role in promoting growth and development.'
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Proteins (2)

Compounds (27)