o Ditri peptides in portal circulation go to liver where there are membrane

O ditri peptides in portal circulation go to liver

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o Di/tri-peptides in portal circulation go to liver where there are membrane-bound di/tri- peptidases on hepatocytes that begin hydrolyzing di/tri-peptides to FAAs AA’s need to be free in order to be incorporated into protein. Excess di/tri-peptides that aren’t hydrolyzed, come out of the liver via the hepatic vein and pass through to muscles and kidney. Brush border di/tri-peptidases on those cell membranes eventually hydrolyze the floating di/tri-peptides to FAAs as needed for protein synthesis or catabolized by liver if not needed MINOR HORMONES INVOLVED IN PROTEIN DIGESTION - There are many other hormones involved in digestion (i.e.- epidermal growth factor; GIP; somatostatin; peptide YY) released by various parts of the GI tract o Don’t play as big a role as secretin and CCK but pharmaceutical industries are interested b/c there may be a therapeutic effect for administering these hormones in excess e.g EGF: secreted from salivary glands has major effects on health maintenance of the GI tract Slows down HCl secretion: can reduce risk of acid-induced lesions Stimulates enterocyte turnover which may be beneficial for those who undergo damage to intestinal tract BIOACTIVE PEPTIDES - Bioactive peptides formed during the digestive procedure in the stomach and intestines are currently a hot topic in research o Studied released of bioactive peptides from the feeding of milk protein in humans using a double-lumen tube down the esophagus into the jejunum [ AJCN 97:1314, 2013 ] Double-lumen tube: a tube within a tube of slightly different lengths that goes down the esophagus pass the sphincter; used to take samples during digestion and absorption This pushes milk protein through the inner tube, pass the sphincter and they can suck back out through the other tube and analyze what’s in that digested sample to ( i.e.- measure size of peptides) o “Clear evidence is shown of the presence of bioact ive peptides in the jejunum of healthy humans who ingested casein.”
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1/23/2014 13 o Other investigators have isolated bioactive peptides and fed them to people. Some are small enough to get across without further hydrolysis into portal circulation. o Casomorphins are a particular peptide that result from partial hydrolysis of casein protein in the GI tract with morphine-like opiate activity in the brain (high in cheese) Certain sizes of those peptides get absorbed in small amounts and bind to opiate receptors in the brain and can have sedation effects o Some peptides derived from soy digestion affect immune system by stimulating the release of TNF- α and improved phagocytosis DAMAGED ENTEROCYTES - It’s very NRG intensive to recycle & resynthesize new enterocytes & it uses up a lot of N and AAs o But the reason this mechanism evolved was to protect the GI tract against toxins and pathogens (vs. constantly repairing it) - How can you monitor recovery during therapy? How can you detect the severity of the effect on GI tract? Most conclusive way is with a biopsy, but this is invasive and expensive CIT o
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  • Spring '14
  • Knutson,MitchellD
  • Trp

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