GHRL - Ghrelin | Elisa - Clia - Antibody - Protein

Background:

Ghrelin is a peptide hormone primarily produced by the enteroendocrine cells of the gastrointestinal tract,and plays a significant role in regulating hunger and appetite. Ghrelin activates cells in the anterior pituitary gland and hypothalamic arcuate nucleus, including neuropeptide Y neurons that initiate appetite. Ghrelin has been also implicated in the release of growth hormone from the pituitary gland, which plays a crucial role in growth, metabolism, and body composition. Ghrelin influences energy balance by increasing food intake and reducing energy expenditure. It can also promote the storage of fat. Ghrelin levels can rise during stressful situations, and it may play a role in response to stress.

Protein Structure:

Ghrelin is a 28-amino acid peptide, derived from the preproghrelin precursor. Its active form is acylated, with an octanoyl group attached to the serine at the third position, which is essential for its biological activity. This acylation is carried out by the enzyme ghrelin O-acyltransferase (GOAT). There is also an unacylated form of ghrelin, which has different biological functions.

Classification and Subtypes:

Ghrelin belongs to a family of growth hormone secretagogues (GHS), which stimulate the secretion of growth hormone (GH) from the pituitary gland. There are two primary forms of ghrelin:

• Acylated Ghrelin: The active form that binds to the growth hormone secretagogue receptor (GHS-R1a) and stimulates appetite and GH release.
• Unacylated Ghrelin: This form does not bind to GHS-R1a but has other roles, such as promoting cell proliferation and inhibiting apoptosis.

Function and Biological Significance:

• Regulation of Appetite: Ghrelin stimulates hunger by acting on the hypothalamus, the brain's appetite control center. It increases food intake and promotes fat storage.
• Growth Hormone Release: Ghrelin stimulates the secretion of GH from the anterior pituitary gland, contributing to growth and metabolism.
• Energy Homeostasis: Ghrelin plays a role in energy balance by influencing food intake, energy expenditure, and fat deposition.
• Gastrointestinal Motility: Ghrelin promotes gastrointestinal motility and gastric emptying, facilitating digestion.
• Cardiovascular Effects: Ghrelin has cardioprotective effects, including improving cardiac output and preventing ischemic injury.

Interactions:

• GHS-R1a: Ghrelin binds to the GHS-R1a receptor in the hypothalamus and pituitary gland to exert its effects on appetite and GH release.
• Neuropeptide Y (NPY) and Agouti-Related Peptide (AgRP): Ghrelin stimulates the release of these neuropeptides, which promote feeding behavior.
• Leptin: Ghrelin and leptin have opposing effects on appetite; leptin decreases hunger, while ghrelin increases it.

Clinical Issues:

• Obesity: Elevated ghrelin levels are often observed in conditions of fasting and weight loss, while lower levels are seen in obesity. Manipulating ghrelin signaling is being explored as a potential treatment for obesity.
• Cachexia and Anorexia: Ghrelin has therapeutic potential in treating cachexia (muscle wasting) and anorexia (loss of appetite) due to its appetite-stimulating properties.
• Growth Hormone Deficiency: Ghrelin or ghrelin mimetics can be used to treat GH deficiency by stimulating GH release.
• Gastrointestinal Disorders: Ghrelin agonists are being investigated for their ability to improve gastrointestinal motility in disorders such as gastroparesis.

Summary:

Ghrelin, the "hunger hormone," plays a crucial role in regulating appetite, energy balance, and growth hormone secretion. Its actions are mediated through the GHS-R1a receptor and involve interactions with various neuropeptides and hormones. Ghrelin's involvement in numerous physiological processes and its potential therapeutic applications in conditions like obesity, cachexia, and gastrointestinal disorders make it a significant focus of medical research. Understanding ghrelin's mechanisms and functions continues to be essential for developing treatments for metabolic and growth-related diseases.