Peptide YY

A satiety hormone.

It is a 36 amino acid peptide synthesized by L-cells in the G.I. tract.

The first two amino acids are cleaved off by DPPIV to produce PYY 3-36

PYY3-36 reduces caloric intake.

Obese humans have low circulating levels of PYY.

Dietary fibers from fruits, vegetables, and whole grains, consumed, increase the speed of transit of intestinal chyme into the ileum, to raise PYY and induce satiety. 

Peptide YY is related to the pancreatic peptide family: 18 of its 36 amino acids located in the same positions as pancreatic peptide.

There are two major forms of peptide YY are PYY1-36 and PYY3-36.

The most common form of circulating PYY immunoreactivity is PYY3-36, which binds to the Y2 receptor (Y2R) of the Y family of receptors.

PYY is found in L cells in the mucosa of gastrointestinal tract, especially in ileum and colon. 

A small amount of PYY, about 1-10%, is found in the esophagus, stomach, duodenum and jejunum.

PYY concentration in the circulation increases postprandially and decreases by fasting.

PYY is also produced by a population of neurons in the brainstem, specifically localized to the gigantocellular reticular nucleus of the medulla oblongata.

PYY exerts its action through NPY receptors; it inhibits gastric motility and increases water and electrolyte absorption in the colon.

PYY may also suppress pancreatic secretion. 

PYY works by slowing gastric emptying, and increases efficiency of digestion and nutrient absorption after a meal. 

Leptin also reduces appetite in response to feeding, but obese people develop a resistance to leptin. 

Obese people secrete less PYY than non-obese people.

The caloric intake during a buffet lunch offered two hours after the infusion of PYY was decreased by 30% in obese subjects and 31% in lean subjects.

The consumption of protein boosts PYY levels, so some benefit is seen in reducing hunger and promoting weight loss: partially explain the weight-loss experienced with high-protein diets, noting also the high thermic effect of protein.

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