Plasma proline and leucine kinetics: response to 4 wk with proline-free diets in young adults.
The effects of removing proline from the diet on plasma leucine and proline kinetics were investigated. After a 1-wk control period, during which young adult men received a diet containing a complete L-amino acid mixture, seven subjects were given for 4 wk a diet devoid of proline (group 1); six received a diet devoid of proline, arginine, aspartate, glutamate, and serine (group 2); and seven continued with the complete diet (group 3). At the end of the control and 4-wk periods subjects were given a continuous, (3-h fast, 5-h fed) intravenous infusion of L-[1-13C]leucine and L-[5,5-2H]proline. Plasma proline was reduced significantly, especially during the fed state, in groups 1 and 2 after the 4-wk diet periods. Small but statistically significant (P < 0.05) reductions occurred in nonoxidative leucine disappearance and leucine appearance during the fasted state in group 2. Proline fluxes decreased by approximately 50% in fasted and fed states in groups 1 and 2. Mean de novo proline synthesis during the fasted state declined markedly (P < 0.05) after 4 wk in groups 1 and 2.
School of Science, Massachusetts Institute of Technology, Cambridge 02142-1308.
T
T
Hiramatsu
J
J
Cortiella
J S
JS
Marchini
T E
TE
Chapman
V R
VR
Young
D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage*; D002208:Caproates / Q000097:blood; D004044:Dietary Proteins / Q000008:administration & dosage*; D006801:Humans; D007262:Infusions, Intravenous; D007651:Keto Acids / Q000097:blood; D007930:Leucine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D011392:Proline / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D016037:Single-Blind Method
D000596:Amino Acids; D002208:Caproates; D004044:Dietary Proteins; D007651:Keto Acids; C013082:alpha-ketoisocaproic acid; D011392:Proline; D007930:Leucine