Introduction
Peptide YY is referred to as PYY. Its structure is highly homologous with pancreatic polypeptide (PP) and neuropeptide Y (NPY), so it is considered to belong to the pancreatic polypeptide family. PYY was first isolated from porcine jejunal mucosa by Tatemoto in 1981. It is a peptide with amidated carboxyl terminus and it is a straight chain polypeptide. In 1993, Taylor confirmed that its molecular structure was formed by condensation of 36 amino acids. The amino acid and carboxy terminal amino acid residues of the peptide are tyrosines and are therefore named tyramidin. In the circulatory system, PYY exists in two forms, PYY 1-36 and PYY 3-36.
Pharmacologic action
Regulation of PYY 3-36 has an effect on feeding behavior. After feeding, high levels of PYY 3-36 act on Y2 receptors in the arcuate nucleus, reducing the concentrations of γ-aminobutyric acid (GABA), neuropeptide Y (NPY), and agouti gene-related protein (AgRP) and stimulating Y1 and Y5 receptors. Peripheral injection of PYY 3-36 stimulated nearly 20% of neurons in the arcuate nucleus to produce alpha-melanocyte-stimulating hormone(α-MSH), a precursor of α-MSH, opioid-melanotrophic cells. A peptide produced by procorticosterone (POMC) that causes anorexia, increases stimulation of alpha-melanocyte-stimulating hormone receptor and inhibits feeding through dipolar neurons. PYY 3-36 does inhibit NPY release and/or neuronal activity via presynaptic Y2 receptors, as well as inhibit the electrical activity of NPY nerve endings and the activation of adjacent POMC neurons.
Function
PYY 3-36 plays an important role in the physiological regulation of digestive tract. Peripheral and central parts involve different receptors. PYY 3-36 has been listed as an effective way to treat obesity. The limitation of its clinical use is its short half-life. PYY 3-36 also has other regulatory functions, and its receptor distribution characteristics interact with other gastrointestinal hormones.
Pharmacokinetics and metabolism
After eating, PYY 3-36 is released into the bloodstream. After ingestion for 15 minutes, the concentration of PYY 3-36 began to increase, and it reached its maximum after 90 minutes, the concentration of PYY 3-36 in the blood was still increasing at 6 hours after the meal. The study found that the concentration of PYY 3-36 began to rise before food reached the colon's L cells, suggesting that the release of PYY 3-36 is regulated by nerves and other hormones. At the same time, it was found that the level of PYY 3-36 in the blood reached the lowest level in the morning after fasting, and began to increase after breakfast. After lunch, the value of the level of PYY 3-36 increased further and reached its maximum finally.
References:
1. Tatemoto, K., & Mutt, V. (1980). Isolation of two novel candidate hormones using a chemical method for finding naturally occurring polypeptides. Nature, 285 (5764), 417.
2. Xue-xin, L. (2012). Peptide Hormones Scattered by L Cells. Heilongjiang Medical Journal, 12, 019.
