Definition of ghrelin

Ghrelin is a polypeptide containing 28 amino acids stimulated by starvation, which is produced predominantly by P / D1 cells lining the bottom of the human stomach and epsilon cells of the pancreas. The GHRL gene encodes an appetite-regulating hormone (also called growth hormone secretagogue, motilin-related peptide) that splits into starvation and obesity inhibin. Ghrelin receptors are expressed in a variety of tissues, including pituitary, stomach, intestine, pancreas, thymus, gonad, thyroid, heart. The diversity of the position of the ghrelin receptor indicates that the ghrelin has a variety of biological functions.

The discovery of ghrelin

Growth hormone is an important hormone scientists have long been discovered in 1996, scientists found a growth hormone secretagogue receptor 1A, in 1999, Japanese scientists Masayasu Kojima first reported growth hormone secretagogue receptor 1A endogenous ligand is Ghrelin prime, since then, the hormone debut, and quickly by the field of biomedical scholars sought after. Ghrelin Ghrelin Ghrelin Ghrelin Ghrelin Growth Hormone ReleaseInducing = Ghrelin. Ghrelin is the first identified ghrelin hormone or appetite-enhancing hormone.

Ghrelin is 28 amino acids of the gastrointestinal peptide hormones, the earliest gastric mucosa P / D1 cells and pancreatic islet? Cells secrete ghrelin. Further study found that in the small intestine, colon, lung, gonad, adrenal cortex, placenta, kidney and brain can also produce and secretion of this material. Ghrelin and obostatin are common precursors of the 117-amino-acid starvation / obesity inhibitory propeptide, which in different cases are referred to as appetite-regulating hormones, growth hormone-releasing peptides, or motilin-related peptides, respectively , A starvation / obesity inhibitory propeptide encoded by the GHRL gene. Ghrelin and the former motilin protein homologous, belonging to the motilin family members. Starvation propeptide can be cut into starvation hormone and C ghrelin hormone, C hungry hormone can continue to cut into obesity inhibin.

Ghrelin is present in an inactive and active form, and the third amino acid residue, serine octanoyl esterification, is active. Starvation Serine Octanoyl Esterification is catalyzed by the stomach and pancreas ghrelin O-acetyltransferase (GOAT). Only the active type of ghrelin hormone can activate the ghrelin hormone receptor, the receptor belongs to the G protein-coupled receptor, known as the growth hormone secretagogue receptor. Glandular receptors are mainly distributed in the hypothalamus, pituitary and vagus nerve cells and gastrointestinal vagus nerve endings, in many tissues are expressed, including the hypothalamus, pituitary, stomach, small intestine, pancreas, thymus, gonad, thyroid and heart. The presence of expression of ghrelin in many tissues and its receptors suggests that this hormone has a wide range of functions.

Ghrelin in the blood in the hungry state (before meals) increased, decreased postprandial. The most basic function of ghrelin is to promote appetite to increase body fat, the role of parts in the hypothalamus (feeding center). High concentrations of leptin can induce satiety, ghrelin and adipocyte secretion of leptin have antagonistic effect. Some weight-loss drugs and methods is to try to reduce the patient's blood ghrelin, increase patient satiety, reduce appetite. Ghrelin has a neurotrophic effect, especially on the hippocampal neurons, cognitive changes in the environment to adapt to and learning is very important, through Akt and other protein kinase pathway activation of eNOS. Ghrelin is also involved in the activities of the reward center. The function of the starvation hormone is still a hotspot in biomedical research. At present, it mainly focuses on its classical energy balance regulation, stimulating growth hormone secretion, central nervous system protection, depression and other stress diseases. As the research progresses, Related drugs may become some metabolic diseases and neurological diseases, the ideal drug and means.

The role of ghrelin

Ghrelin levels increased before meals and decreased after meals. It is produced by the adipose tissue as the body of leptin, high levels of leptin will lead to a sense of satiety. In some obesity treatment process,

Ghrelin levels will be lowered before they rise, resulting in satiety.

Ghrelin is a potential stimulator of pituitary growth hormone secretion. The ghrelin receptor is a G protein-coupled receptor, also known as the growth hormone secretagogue receptor. Ghrelin binds to the growth hormone secretagogue receptor alpha, which is highly distributed in the hypothalamus, the pituitary gland, and the vagus nerve cell body, the vagus nerve endings.

Ghrelin plays an important role in neurotrophic activity, especially in the hippocampus, which is essential for cognitive and learning processes after environmental change. In a pathway that relies on multiple kinases, including Akt kinases, ghrelin is known to activate endothelial nitric oxide synthase isoforms.

The Mechanism of action of Ghrelin

Ghrelin is the first and only discovered a cycle of ghrelin hormones, or called the appetite-enhancing hormone. Mainly produced by the large intestine, can also be in the lung, islet cell gland, adrenal cortex, placenta, kidney and brain secretion. The diversity of the secretory position of the starvation hormone once again points out that ghrelin has a wide variety of biological functions. Ghrelin and artificial starvation (growth hormone secretagogue) increase food intake, leading to increased fat mass. It activates the nucleus of the arc (containing neurons that promote appetite neuropeptide Y). The neuronal response to starvation is also sensitive to leptin and insulin. Starvation also activates the midbrain-like dopaminergic cholinergic reward mechanism, which can convey the pleasure and reinforcement of natural rewards, such as food, and, of course, addictive drugs such as alcohol. In fact, from the wine, the pleasure of food to get the central ghrelin signal. Ghrelin by affecting the mechanical sensitivity of gastric vagus nerve, reducing their swelling sensitivity, resulting in more food, and thus play a sense of satiety with a secondary appetite regulation effect.

Ghrelin disease

The level of plasma ghrelin is lower in the obese than in the lean population, indicating that ghrelin does not lead to obesity. In addition to obesity due to Prader-Willi syndrome, this patient is more likely to eat because of high levels of ghrelin. Ghrelin on the anorexia nervosa has a therapeutic effect.

Ghrelin on the thin people from midnight to dawn will continue to increase, pointing out that fat people endocrine system there are some minor problems. A shorter sleep duration can lead to obesity, but also increase appetite through hormonal regulation. Lack of sleep produces too much ghrelin, stimulates appetite, and suppresses appetite reduction in leptin secretion.

Ghrelin in some cancer patients in vivo high, including cachexia.

Gonadotropin increases dopamine concentration in the substantia nigra through its receptor, and dopamine cell degeneration in the substantia nigra can lead to Parkinson's disease. Therefore, starvation may be used to slow down the occurrence of Perkins.