Autism Studies and Related Medical Conditions, January 2009 - TACA

Abstract:Intraluminal and brush-border digestion of proteins results in a mixture of
amino acids and small peptides. Thirteen brush-border peptidases have been described.
Despite all of these enzymes, some peptides escape digestion and are absorbed intact.
The assimilated products of protein digestion can follow multiple paths: absorption into
the blood as amino acids or small peptides, metabolism within the enterocyte,
incorporation into proteins of the enterocyte, and incorporation into proteins to be
secreted into plasma. Unlike other tissues, the intestinal mucosa is not very responsive
to metabolic regulation as regards amino acid uptake or regulation of protein synthesis.
Most effects after dietary manipulation or drug or hormonal stimulation are modes
(two-to fivefold increases). This constitutive metabolism of amino acids in the intestinal
mucosa is consistent with its essential role in absorption. The mucosa also is a major
contributor to apolipoproteins, which are probably the quantitatively most important
proteins secreted from the intestine. Alterations in apoprotein secretion have been
noted after fat feeding, and are both transcriptionally and translationally regulated.
Although the fractional renewal rate of protein in the intestine is the highest of any
tissue in the body, the quantitative importance of alterations in protein synthesis or
secretion to the fate of intracellular amino acids is not known.
Svedberg, J.et al: Demonstration of beta-casomorphin immunoreactive materials in in
vitro digests of bovine milk and in small intestine contents after bovine milk ingestion in
adult humans. Peptides 1985 / 6 / pag.825-830.
Abstract: Healthy young volunteers ingested one liter of cows' milk; then the contents
of the small intestine were aspirated through an intestinal tube at various times and
assayed for the presence of bovine beta-casomorphin immunoreactive materials.
Considerable amounts of beta-casomorphin-7, but no beta-casomorphin-5 and only
small amounts of beta-casomorphin-4 or -6 immunoreactive materials were found.
Chromatographical characterization showed that most of the beta-casomorphin-7
immunoreactive material was not identical with beta-casomorphin-7, whereas the major
part of the beta-casomorphin-4 or -6 immunoreactive materials might be identical with
their corresponding beta-casomorphins. Analogous results were obtained for in vitro
digestion of bovine milk which had been designed as a rough imitation of the
gastrointestinal digestion process. A regulatory influence of beta-casomorphins as "food
hormones" on intestinal functions is suggested.
Saelid G, et. al.: Peptide-Containing Fractions in Depression. Biol Psychiatry 1985, 20:
245-256.
Abstract: A mixture of peptides and glycoproteins has been found in benzoic acidprecipitable
material from urines of psychomotorically agitated and retarded
endogenous depressive patients. This complex mixture of compounds is fractionated on
a Sephadex G-25 gel, from which the different peaks are further separated on Biogel
P2. The G-25 elution profiles ultraviolet absorbance, 280 nm) from depressive patients
deviated from the normal pattern. The increase in hydrolyzable ninhydrin-colorable
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