Plasma proline and leucine kinetics: response to 4 wk with proline-free diets in young adults

• Published in: The American journal of clinical nutrition Vol. 60; no. 2; pp. 207 - 215
• Main Authors: Hiramatsu, T, Cortiella, J, Marchini, JS, Chapman, TE, Young, VR
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.08.1994; American Society for Clinical Nutrition; American Society for Clinical Nutrition, Inc
• Subjects: Adult; Amino acids; Amino Acids - administration & dosage; Biological and medical sciences; Caproates - blood; diet; Dietary Proteins - administration & dosage; flux; Fundamental and applied biological sciences. Psychology; Humans; Infusions, Intravenous; Keto Acids - blood; Kinetics; leucine; Leucine - administration & dosage; Leucine - blood; Leucine - pharmacokinetics; leucine balance; Male; Medical research; Metabolisms and neurohumoral controls; Nitrogen metabolism. Proteins. Glycoproteins. Nucleic acids. Collagen; Nutrition; plasma concentration; Proline; Proline - administration & dosage; Proline - blood; Proline - pharmacokinetics; Single-Blind Method; synthesis; Vertebrates: anatomy and physiology, studies on body, several organs or systems; young men; leucine; synthesis; leucine balance; Proline; flux; young men; diet; kinetics; plasma concentration; Human; Aminoacid; Exploration; Kinetics; Leucine; Metabolism
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/60.2.207

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 ≈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.