Q has been measured under stress conditions and disorders using labeled AAs but can be hard to determine. Use this method to try and get a handle on Q and figure out what’s going with C and S rates but under some disorders you get results that cannot be interpreted oGreat disturbance of hormones under those conditions make skew results b/c some of those catabolic hormones don't affect all organs equally i.e.- Cortisol leads to loss of protein from SM and an of protein content/AAs in the liver oAging is another example: papers show that protein S rates of muscle during aging; protein S not as robust compared to a younger person of same size With the elderly lots of papers show a in muscle protein S (muscle ~45% of body) so you have to assume that C rate would also have to if S rate But if Sand C stays the same, over time the body would have a in muscle mass and thus weight loss would occur oN balance changes depending upon whether the S rate or but you also have to know what the C rate is. The difference in S and C rates = N balance But remember, you could be in N balance and you don’t know if this is due to a change in protein S rate or due to an in C rate. Or it could be due to constant C rate but S rate. Either way you end up with negative N balance §If in a report someone says protein S rate in the elderly is not as good as the young you have to also assume that the C rate has to . Otherwise they would just be losing weight every day (due to constant C and S)and never stabilize. 18. Q IS A BALANCE OF S AND C -Important point: if S or C changes it can be short term (e.g.- if measuring in someone who just had a serious injury and is trying to recover) oClinicians want to know what happens to protein S and C under these types of injuries; which is being affected the most. Then they can decide the best method of treatment e.g.-if C but the S rate doesn’t, you’re going to be in N balance and lose weight. Then pharmaceutical companies will try and address how to C It’s been measuredin pregnancy, athletic performance, children and even in space -Can have temporary large changes/ differences in C and S but this can’t go on for long periods of time because it’s not compatible with keeping protein mass of the body. Or you die. o30% loss of body protein begins dramatically risk of death and this is an indicator that we don’t store excess protein oWhen in negative NRG balance and protein intake is compromised, you’ll begin losing protein mass. Quite a bit of muscle will be lost b/c the body will go into survival mode and the AAs not reutilized for protein S are going to be used for S of survival proteins -§ If there is a change in C and there’s no major stress or injury assoc’d with the change, then you have to assume that S must change in a direction to keep you from dying (and vice versa)
SFLORES_2/27/2014 14 19. EFFECT OF USING DIFFERENT LABELED-AAs -Compared 9 different 15N-labeled AAs, gave it to himself either orally or IV. In separate studies
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