all the N losses and BW didn't change, something else had to in order to have all that extra N being retained. Speculated that cellular water was the one that declined with an in total N retention by the body. But they said that physiological adjustment periods to dietary changes may take longer than assumed (more than 50 days) b/c N retention of 1.6g/d can’t go on forever. May take a lot longer to adapt to high protein diet before you go into N equilibrium b/c you cant keep cellular water w/o affecting cell fxn.
SFLORES_4/7/2014 67 Important point: if you change N intake, it may take longer than 50d to show adaptation to show a change to dietary protein intake versus 1-2 weeks which was what was previously thought These results have been repeated in other studies that show consistent + N balance even in college aged people on high protein diets done up to 4 wks WHAT IS IN N RESERVE? -Is this protein actually retained by the body? It can’t be, b/c protein retained in an aqueous matrix and extra weight would be evidenced by changes in BW, but you don't. oReproduced studies in animals with a persistent + N retention show that the extra N is probably a reserve of non-protein N that can in the body with high protein diets but not show up as full BW changes or changes in lean body mass: amount of enzymes to metabolize extra protein Temporary ofFAA pool Hormones Peptides Glutathione levels N RESERVE CONSISTS OF PEPTIDES SUCH AS CARNOSINE AND ANSERINE -There are lots of these kinds of peptides in the body that all play a role in metabolism. It’s thought that this N reserve is made up of these peptides b/c they do , they are easily mobilized, you can syn more of it and they’re in non-protein form oThought that these peptides account for N reserve on a prot-free diet So we don’t want to talk about it as a protein reserve b/c we don't have a protein reserve, but its ok to call it a N reserve b/c its in non-protein form -Peptides such as carnosine and anserine may during high protein diets oi.e.-Carnosine is a peptide (made up of -Ala and His; look up structure of -alanyl His) found abundantly in muscle tissue and brain This may account for the reason why it takes a long time to show deficiency on a His-free diet. B/c you may just be metabolizing excess carnosine to free up the His to use for more important body functions oAnother peptide called Anserine (Ala + 1 methyl-His); not found in humans Methyl-His: His goes is post-translationally methylated in the 1 or 3 position (in actin myosin its 3MH) In normal Q of SM protein, 3MH is released & not reutilized. So its found in the urine and can be used as a crude measure of SM catab -Functions of carnosine include: -Antioxidant (has powerful in vitroantioxidant activity) -Regulate osmotic pressure -Complexes with lipid peroxidation products to detoxify them -Intracellular signaling-May athletic performance
SFLORES_4/7/2014 68 oAlso been shown that if you take β-Ala (which is not a normal component of food) you can carnosine w/o having to give His along with it.
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