Proc. Natl. Acad. Sci. USA Vol. 94, pp. 14930-14935, December 1997
Physiology
Slow and fast dietary proteins differently modulate postprandial protein accretion
ABSTRACT
The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology. WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 µmol·kg1) than with WP (373 ± 56 µmol·kg1). Leucine intake was identical in both meals (380 µmol·kg1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate the postprandial metabolic response, a concept to be applied to wasting situations.
DISCUSSION
The impact on postprandial protein metabolism of the speed of amino acid absorption by the gut has not been estimated previously in humans. Under the conditions of this study, i.e., a single protein meal with no energy added, two dietary proteins have different metabolic fates and uses. After WP ingestion, the plasma appearance of dietary amino acids is fast, high, and transient. This amino acid pattern is associated with an increased protein synthesis and oxidation and no change in protein breakdown. By contrast, the plasma appearance of dietary amino acids after a CAS meal is slower, lower, and prolonged with a different whole body metabolic response: Protein synthesis slightly increases, oxidation is moderately stimulated, but protein breakdown is markedly inhibited. The latter metabolic profile results in a better leucine balance.
Siinahan sita oli, kaseiini imeytyy hitaammin. Osta kallista heraisolaattia ja laita sekaan maitoa ja avot, meni patakka hukkaan. Ei tuosta taida oikein muuta saada irti... (ei toimi enaa aivot tahan aikaan:evil: )
E: Jos joku miettii, etta miksi nain -siihen ei artikkeli osannut vastata. Valiako silla?