Q has been measured under stress conditions and disorders using labeled AAs but

Q has been measured under stress conditions and

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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 o Great 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 o Aging 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 S and C stays the same, over time the body would have a in muscle mass and thus weight loss would occur o N 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) o Clinicians 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 measured in 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. o 30% loss of body protein begins dramatically risk of death and this is an indicator that we don’t store excess protein o When 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)
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SFLORES_2/27/2014 14 19. EFFECT OF USING DIFFERENT LABELED-AAs - Compared 9 different 15 N-labeled AAs, gave it to himself either orally or IV. In separate studies
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  • Spring '14
  • Knutson,MitchellD
  • NRG

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