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Deamination of amino acids: a source of muscle ammonia production during exercise
Topic 20-GLUTAMINE
AND ANALOGUES
P.86 Deamination of amino acids: a source of muscle ammonia production during exercise. G. van Hall, B. Saltin*. G. van der Vusse, K. Soderlund*, W.
Introduction: Total parenteral nutrition (TPN) in combination with gut starvation is reported to result in deterioration of the mucosal architecture and function. A deterioration of the mucosa may result in an impaired intestinal integrity, increasing the risk of bacteraemia and endotoxaemia. The observed changes during TPN are frequently ascribed to the lack of glutamine in commercially available TPN. Beneficial effects of glutamine enrichment of TPN on gut mucosa architecture and function have been shown in experimental animal research. The effect of glutamine on intestinal architecture and permeability was therefore studied in man. Patients and Methods: Twenty patients admitted for TPN were randomly allocated to an experimental group receiving glutamine enriched TPN (GLN) and a group receiving standard TPN (CONT). Patients received isonitrogenous, isocaloric and isovoluminous TPN solutions for a period of two weeks. Intestinal permeability and duodenal histology were studied before and after two weeks of TPN. A duodenoscopy was performed and biopsies from the second part of the duodenum were taken. A solution containing 10 grams of lactulose (Lc) and 0.5 grams of mannitol (Mn) was directly administered into the duodenal bulb at the end of the duodenoscopy. Urine was collected over a period of six hours after administration of the lactulose-mannitol solution. Lc and Mn were measured using gas-liquid chromatography. The ratio of Lc and Mn in urine was used to assess intestinal permeability. Results: In the CONT group a significant increase in the Lc/Mn ratio in urine was observed (delta = 0.15&0.07), whereas in the GLN group permeability was unaltered (delta = 0.01 iO.03) after two weeks of TPN. In addition, a small decrease in villusheight was found in the CONT group (day 0: 476&l 1 pm; last day: 438&l 4 pm), whereas villusheight in the GLN group was unaltered (day 0: 459&l 3 pm; last day: 458 + 21 pm). Conclusion: These findings suggest a beneficial effect of GLN addition to TPN on gut mucosal architecture and integrity.
H. M. Saris, A. J. M. Wagenmakers University of Limburg, The Netherlands; lKaroiinska Institute, Sweden Stable isotope methods have shown that the human body synthesizes between 80 and 180 gram of glutamine per day. A major part of the glutamine production occurs in skeletal muscle. Part of it is derived from net protein breakdown, part should also be derived from synthesis of new glutamine. The last step in glutamine synthesis is the glutamine synthetase reaction (glutamate+ATP+ammonia > glutamine+ADP+Pi). However, it is not clear which reactions in muscle may generate ammonia at rates that can account for such high glutamine synthesis rates. Theoretically uptake of ammonia from the circulation and two endogenous processes may provide ammonia: 1. the AMP deaminase reaction (AMP > IMP+ammonia) and 2. deamination of amino acids (via the purine nucleotide cycle or via glutamate dehydrogenase). The contribution of the latter source so far has been assumed to be negligible. Exercise leads to a substantial ammonia release and therefore is used here to examine whether more ammonia is produced by leg muscles than can be accounted for by breakdown of adenine nucleotides to IMP and ammonia. Methods: Seven male subjects exercised the knee extensor muscles of one leg at 60% of maximal workload for 90 min. Blood flow was measured by thermodilution. Femoral arterial and venous blood samples were drawn for measurement of ammonia (0, 10,30,60 and 90 min) and muscle biopsies were taken (0 and 90 min) for measurement of the concentration of ammonia, total adenine nucleotides (TAN) and IMP. Results: At rest ammonia was taken up by the leg at a rate of 1.36&l .14 pmol/min. During exercise ammonia was released. The ammonia release increased gradually from 45.7 k 13.0 (after 10 min) to 94.2* 35.8 pmol/min (after 90 min). Total ammonia release during 90 min of exercise was 8.2+ 1.7 mmol. The concentration (in pmol per g dry mass) of TAN and IMP were similar in the resting muscle and after exercise, whereas the concentration of ammonia increased. Rest Exerase
90 min
TAN 29.4k3.5 29.6 k 2.4
IMP 0.31 kO.28 0.48 + 0.45
P.88 The effect of a dietary protein source rich in glutamine on plasma and muscle concentrations of glutamine in.rats. 0. E. Rooyackers, A. J. M. Wagenmakers, W. H. M. Saris,
ammonia 0.42+0.08 0.93+0.34
Conclusions: The total dry mass involved in knee extensor exercise is 750 g or less. Therefore, total ammonia production during exercise is 11 pmol per g dry mass or more. This implies that ammonia production exceeds the breakdown of adenine nucleotides to IMP. Therefore, deamination of amino acids in muscle also should be considered as a potential source of ammonia production during exercise and as a process that may generate ammonia required for synthesis of glutamine via the glutamine synthase reaction.
and P. B. Soeterst Departments of Human Biology and tGeneral Surgery, University of Limburg, Maastricht, The Netherlands Characteristic changes in muscle and plasma pattern of amino acids occur immediately after surgery or during critical illness. During recovery the pattern returns to normal except for a prolonged decrease in concentrations of glutamine in muscle (up to 30 days after elective surgery). Glutamine (Gin) supplementations have been suggested to reduce net protein catabolism and improve gut function following surgery and during illness. Diets rich in Gln, therefore, could be beneficial for patients. Here we investigate the effect of a diet rich in Gln on the plasma and muscle Gln pools in rats. Methods: Male Lewis rats were fed a normal diet or one of two diets with a protein source rich in Gln, but low in essential amino acids. Gln contents were estimated to be 8% of the protein source in the control diet, and 16% or 20% in the enriched diets. The Gln rich protein source was mixed
P.87 Glutamine dipeptide prevents increased intestinal permeability after two weeks of TPN. R. R. W. J. van der HulstTi, B. K. van Kreelt, M. F. von Meyenfeldtn: R. J. Brummer5,N. E. P. DeutzTT,P. B. Soetersv Departments of SurgeryE Clinical Chemistryt, and Gastroenterologyl, University Hospital of Limburg, Maastricht, The Netherlands 62
AND ANALOGUES
P.86 Deamination of amino acids: a source of muscle ammonia production during exercise. G. van Hall, B. Saltin*. G. van der Vusse, K. Soderlund*, W.
Introduction: Total parenteral nutrition (TPN) in combination with gut starvation is reported to result in deterioration of the mucosal architecture and function. A deterioration of the mucosa may result in an impaired intestinal integrity, increasing the risk of bacteraemia and endotoxaemia. The observed changes during TPN are frequently ascribed to the lack of glutamine in commercially available TPN. Beneficial effects of glutamine enrichment of TPN on gut mucosa architecture and function have been shown in experimental animal research. The effect of glutamine on intestinal architecture and permeability was therefore studied in man. Patients and Methods: Twenty patients admitted for TPN were randomly allocated to an experimental group receiving glutamine enriched TPN (GLN) and a group receiving standard TPN (CONT). Patients received isonitrogenous, isocaloric and isovoluminous TPN solutions for a period of two weeks. Intestinal permeability and duodenal histology were studied before and after two weeks of TPN. A duodenoscopy was performed and biopsies from the second part of the duodenum were taken. A solution containing 10 grams of lactulose (Lc) and 0.5 grams of mannitol (Mn) was directly administered into the duodenal bulb at the end of the duodenoscopy. Urine was collected over a period of six hours after administration of the lactulose-mannitol solution. Lc and Mn were measured using gas-liquid chromatography. The ratio of Lc and Mn in urine was used to assess intestinal permeability. Results: In the CONT group a significant increase in the Lc/Mn ratio in urine was observed (delta = 0.15&0.07), whereas in the GLN group permeability was unaltered (delta = 0.01 iO.03) after two weeks of TPN. In addition, a small decrease in villusheight was found in the CONT group (day 0: 476&l 1 pm; last day: 438&l 4 pm), whereas villusheight in the GLN group was unaltered (day 0: 459&l 3 pm; last day: 458 + 21 pm). Conclusion: These findings suggest a beneficial effect of GLN addition to TPN on gut mucosal architecture and integrity.
H. M. Saris, A. J. M. Wagenmakers University of Limburg, The Netherlands; lKaroiinska Institute, Sweden Stable isotope methods have shown that the human body synthesizes between 80 and 180 gram of glutamine per day. A major part of the glutamine production occurs in skeletal muscle. Part of it is derived from net protein breakdown, part should also be derived from synthesis of new glutamine. The last step in glutamine synthesis is the glutamine synthetase reaction (glutamate+ATP+ammonia > glutamine+ADP+Pi). However, it is not clear which reactions in muscle may generate ammonia at rates that can account for such high glutamine synthesis rates. Theoretically uptake of ammonia from the circulation and two endogenous processes may provide ammonia: 1. the AMP deaminase reaction (AMP > IMP+ammonia) and 2. deamination of amino acids (via the purine nucleotide cycle or via glutamate dehydrogenase). The contribution of the latter source so far has been assumed to be negligible. Exercise leads to a substantial ammonia release and therefore is used here to examine whether more ammonia is produced by leg muscles than can be accounted for by breakdown of adenine nucleotides to IMP and ammonia. Methods: Seven male subjects exercised the knee extensor muscles of one leg at 60% of maximal workload for 90 min. Blood flow was measured by thermodilution. Femoral arterial and venous blood samples were drawn for measurement of ammonia (0, 10,30,60 and 90 min) and muscle biopsies were taken (0 and 90 min) for measurement of the concentration of ammonia, total adenine nucleotides (TAN) and IMP. Results: At rest ammonia was taken up by the leg at a rate of 1.36&l .14 pmol/min. During exercise ammonia was released. The ammonia release increased gradually from 45.7 k 13.0 (after 10 min) to 94.2* 35.8 pmol/min (after 90 min). Total ammonia release during 90 min of exercise was 8.2+ 1.7 mmol. The concentration (in pmol per g dry mass) of TAN and IMP were similar in the resting muscle and after exercise, whereas the concentration of ammonia increased. Rest Exerase
90 min
TAN 29.4k3.5 29.6 k 2.4
IMP 0.31 kO.28 0.48 + 0.45
P.88 The effect of a dietary protein source rich in glutamine on plasma and muscle concentrations of glutamine in.rats. 0. E. Rooyackers, A. J. M. Wagenmakers, W. H. M. Saris,
ammonia 0.42+0.08 0.93+0.34
Conclusions: The total dry mass involved in knee extensor exercise is 750 g or less. Therefore, total ammonia production during exercise is 11 pmol per g dry mass or more. This implies that ammonia production exceeds the breakdown of adenine nucleotides to IMP. Therefore, deamination of amino acids in muscle also should be considered as a potential source of ammonia production during exercise and as a process that may generate ammonia required for synthesis of glutamine via the glutamine synthase reaction.
and P. B. Soeterst Departments of Human Biology and tGeneral Surgery, University of Limburg, Maastricht, The Netherlands Characteristic changes in muscle and plasma pattern of amino acids occur immediately after surgery or during critical illness. During recovery the pattern returns to normal except for a prolonged decrease in concentrations of glutamine in muscle (up to 30 days after elective surgery). Glutamine (Gin) supplementations have been suggested to reduce net protein catabolism and improve gut function following surgery and during illness. Diets rich in Gln, therefore, could be beneficial for patients. Here we investigate the effect of a diet rich in Gln on the plasma and muscle Gln pools in rats. Methods: Male Lewis rats were fed a normal diet or one of two diets with a protein source rich in Gln, but low in essential amino acids. Gln contents were estimated to be 8% of the protein source in the control diet, and 16% or 20% in the enriched diets. The Gln rich protein source was mixed
P.87 Glutamine dipeptide prevents increased intestinal permeability after two weeks of TPN. R. R. W. J. van der HulstTi, B. K. van Kreelt, M. F. von Meyenfeldtn: R. J. Brummer5,N. E. P. DeutzTT,P. B. Soetersv Departments of SurgeryE Clinical Chemistryt, and Gastroenterologyl, University Hospital of Limburg, Maastricht, The Netherlands 62