Measurement of keto-acids is important in various clinical situations. The aim of the present wor... more Measurement of keto-acids is important in various clinical situations. The aim of the present work was to develop a rapid HPLC method for the determination of keto-acids in human serum and to assess the concentrations of these acids in young adults and institutionalized elderly adults. This method was applied to the determination of blood keto-acid concentrations of young adults and institutionalized elderly people, divided into age groups Four keto-acids (alpha-ketoisocaproate, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, and pyruvate) were derivatized with o-phenylenediamine to give fluorescent derivatives. After the sample preparation step (75 min to prepare 20 samples), the derivatives were separated chromatographically on a reversed-phase column using a binary gradient. The fluorometric detection of the four keto-acids was rapid, <12 min. The method is repeatable and reproducible: the CVs were <6% and <11%, respectively, for each of the keto-acids. We found n...
To investigate appropriate mode and daily dose of enteral ornithine alpha-ketoglutarate (OKG) adm... more To investigate appropriate mode and daily dose of enteral ornithine alpha-ketoglutarate (OKG) administration, 54 burn patients (total burn surface area: 20-50%) were included in a randomized controlled trial and assigned to receive either a supplement of OKG (10, 20 or 30 g/d) as bolus or continuous infusion, or a continuous infusion of an isonitrogenous amount of a soy protein mixture (Protil-1: 10, 20 or 30 g/d) in addition to their enteral diet. The influence of these treatments on clinical outcome and biological indices was evaluated. OKG administration significantly improved nitrogen balance and reduced 3-methylhistidine and hydroxyproline urinary elimination. This was associated with a gradual rise in plasma glutamine over time. Given as a bolus, OKG significantly improved wound healing, assessed both clinically [day of last graft: (mean +/- SEM) OKG bolus 23.7 +/- 2.1 d versus Protil-1, 39.9 +/- 9.9 d; P < 0.05] and by hydroxyproline excretion, and biological markers of ni...
ABSTRACT Increase in life expendancy and global aging of the population have led to increased int... more ABSTRACT Increase in life expendancy and global aging of the population have led to increased interest in the aging process. A better understanding of aging-related modifications of meta-bolism is needed. For example, aging is an independent risk factor in critically ill patients. Allowing for illnesses whose frequency increases with age (obesity, NIDDM, cardiovascular disease), this may result from impaired metabolic response to hormones. This review present the current literature data concerning the evolution of the responsiveness to anabolic (insulin) and catabolic hormones (glucagon, glucocorticoids, catecholamines and thyroid hormones) with aging. Although some studies indicate a decrease in the responsiveness to various hormones, these modifications are moderate and their consequences are difficult to ascertain given the influence of confounding factors such as abnormal energy metabolism linked to dietary habits and life-style.
Enhancement of depressed plasma concentrations of glutamine and arginine is associated with bette... more Enhancement of depressed plasma concentrations of glutamine and arginine is associated with better clinical outcome. Supplementation of glutamine might be a way to provide the patient with glutamine, and also arginine, because glutamine provides the kidney with citrulline, from which the kidney produces arginine when plasma levels of arginine are low. The aim of the present study was to investigate the parenteral and enteral response of the administered dipeptide Ala-Gln, glutamine, citrulline and arginine. Therefore, seven patients received 20 g Ala-Gln, administered over 4 h, parenterally or enterally, on two separate occasions. Arterial blood samples were taken before and during the administration of Ala-Gln. ANOVA and a paired t test were used to test differences (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05). Ala-Gln was undetectable with enteral administration, whereas Ala-Gln remained stable at a plasma concentration of 268 micromol/l throughout parenteral infusion and rapidly decreased towards zero after infusion was stopped. The highest level of glutamine was observed with parenteral infusion of the dipeptide, although enteral infusion also significantly increased plasma levels of glutamine. The highest plasma response of citrulline was observed with the enteral administration of the dipeptide, although parenteral administration also increased plasma levels of citrulline. Plasma arginine increased significantly with parenteral infusion, but not with enteral administration of Ala-Gln. In conclusion, administrations of Ala-Gln, parenteral or enteral, resulted in an increased plasma glutamine response, as compared with baseline. Interestingly, in spite of the high availability of citrulline with enteral administration of the dipeptide, only parenteral infusion of Ala-Gln increased plasma arginine concentration.
Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via ant... more Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via anti-oxidative defences. The aim of this study was to evaluate the protective effect of these AAs on warm ischaemia-reperfusion (I/R) injury in the isolated perfused rat liver. Livers from fasted male Sprague-Dawley rats were isolated and perfused without (control group) or with (AP group) a mixture of regulatory AAs (glutamine, histidine, leucine, methionine, proline, phenylalanine, tryptophan and alanine). After 45 min of perfusion, warm ischaemia was induced for 45 min by clamping the portal vein catheter; thereafter, reperfusion was performed for 30 min. TNF-alpha production was significantly lower in the AP group during reperfusion ( 39+/-7 versus AP: 16+/-2 pg min-1 g-1, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), and lactate dehydrogenase (LDH) release decreased significantly during the last 15 min of reperfusion ( 0.13+/-0.03 versus AP: 0.04+/-0.02 IU min-1 g-1, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), despite similar levels of oxidative stress. The addition of regulatory AAs was not associated with variations in portal flow, bile flow, hepatic glucose or urea metabolism. However, significant changes in intrahepatic glutamine ( 1.4+/-0.2 versus AP: 2.6+/-0.5 micromol g-1, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) together with higher glutamate release in the AP group ( 10.2+/-5.4 versus AP: 42.6+/-10.9 nmol min-1 g-1, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) indicated modifications in nitrogen metabolism. Taken together, the lower TNF-alpha production, suggesting decreased inflammatory response, the decrease in LDH release in the AP group, demonstrating a better preservation of liver viability, and the increase in hepatic glutamine indicate that AAs play an important role in the liver&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s response to I/R.
We previously demonstrated that ornithine alpha-ketoglutarate (OKG), known for its anabolic prope... more We previously demonstrated that ornithine alpha-ketoglutarate (OKG), known for its anabolic properties, induces insulin secretion in vitro. The present study was undertaken to further characterize this effect in vivo and investigate a possible interaction with glucose both in vivo and in vitro. Male Wistar rats received an intravenous bolus of OKG (25 mg/kg) and/or glucose (0.8 g/kg) or saline, and their plasma insulin and glucose levels were monitored for 30 minutes. OKG alone increased plasma insulin to a similar extent to glucose. In combination with glucose, OKG significantly increased glucose-induced insulin secretion in vivo and in vitro, and led to a significant increase in glucose utilization in vivo. The absence of significant variations in plasma arginine and glutamine suggests a direct effect of OKG on the pancreas. To assess the involvement of the synthesis of nitric oxide and glutamine in OKG-induced insulin secretion, the experiments were repeated in the presence of inhibitors of these 2 pathways, respectively L-nitroarginine-methylester (L-NAME) and methionine sulfoximine (MSO). Both inhibitors were able significantly to reduce OKG-induced insulin secretion without affecting either basal or glucose-induced insulin release. Thus OKG acts directly with glucose on islets to induce insulin secretion via mechanisms involving NO and glutamine synthesis. In addition, our results suggest that OKG and glucose act via separate pathways.
Conflicting data on the effects of amino acids on biliary function led us to investigate their in... more Conflicting data on the effects of amino acids on biliary function led us to investigate their interaction with taurocholate in the perfused rat liver model. To investigate the influence of amino acids on the bile acid-independent component of bile flow, 12 livers were perfused with (n = 6) and without (n = 6) amino acid addition from t30 min. For the study of bile acid-dependent bile flow, 24 livers were perfused under 8 experimental conditions according to the perfusate taurocholate concentration (12.5, 25, 37.5 or 50 microM) and whether amino acids were or were not added from t30 min. In the absence of taurocholate, amino acids induced a 40% (p&amp;amp;lt;0.01) decrease in bile flow together with an increase in hepatic water content (17.8%, p&amp;amp;lt; 0.05). Thus, amino acids exert an inhibitory effect on bile acid-independent bile flow despite the postulated cell swelling-dependent increase in bile flow. When livers were perfused at various taurocholate concentrations, amino acids induced, in addition to their inhibitory effect on bile acid-independent bile flow, a significant increase in taurocholate apparent choleretic activity (13.2 microl/micromol vs. 10.6 microl/micromol; p = 0.05), while taurocholate intrinsic clearance was significantly decreased (4.5+/-1.2 ml x min(-1) x g(-1) vs. 6.1+/-1.3 ml x min(-1) x g(-1); p&amp;amp;lt;0.01). These data suggest that at physiological bile acid concentrations amino acids exert an inhibitory effect on both bile acid-dependent and- independent bile flow, whereas at higher taurocholate concentrations this inhibitory effect disappears, probably because of cell swelling-dependent mechanisms.
Background/Aims: Energy charge and capacity for adenosine triphosphate (ATP) synthesis have been ... more Background/Aims: Energy charge and capacity for adenosine triphosphate (ATP) synthesis have been demonstrated to play a major role in the maintenance of organ function after liver preservation for transplantation. The aim of this study was to evaluate whether a supply of liposomally-entrapped ATP during preservation could improve the energy state and metabolism of cold-stored rat liver.Methods: In the first set
Increased susceptibility to infections in obese patients may be related to decreased availability... more Increased susceptibility to infections in obese patients may be related to decreased availability of arginine and glutamine, which may affect immune cell functions. Our aim was to evaluate the in vitro effects of these amino acids on the function of macrophages from obese insulin-resistant Zucker rats. Macrophages, isolated from male Zucker obese or lean rats by peritoneal lavage, were incubated in Dulbecco&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s modified Eagle medium (DMEM) without arginine or glutamine. Arginine or glutamine was added to the medium at increasing final concentrations (0, 0.25, 0.5, 1 or 2 mM). After stimulation by lipopolysaccharide (LPS) from E. coli (40 microg/ml), productions of tumour necrosis factor alpha (TNFalpha) and of nitric oxide (NO) were measured after 3 or 48 h incubation, respectively. NO production, lower in macrophages from obese rats, decreased in macrophages from lean rats (0 mM: 2,423 +/- 1,174 vs. 2 mM: 198 +/- 31 microM/mg protein/24 h; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), but not in those from obese rats, when glutamine was added. TNFalpha production, lower in macrophages from obese rats, was inversely correlated with glutamine concentration. In the presence of arginine, NO production was constantly higher in macrophages from obese rats. It peaked at 0.5 mM arginine and decreased thereafter in both groups. TNFalpha production in macrophages from lean rats was unaffected by arginine, but decreased in macrophages from obese rats (0 mM: 1920 +/- 450 vs. 2 mM: 810 +/- 90 microM/mg protein/3 h; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). These results suggest that abnormalities in cell signalling or in arginine and glutamine metabolism in macrophages of obese rats, resulting in decreased TNFalpha production and increased NO release, may contribute to increased susceptibility to infection in insulin-resistant states.
Measurement of keto-acids is important in various clinical situations. The aim of the present wor... more Measurement of keto-acids is important in various clinical situations. The aim of the present work was to develop a rapid HPLC method for the determination of keto-acids in human serum and to assess the concentrations of these acids in young adults and institutionalized elderly adults. This method was applied to the determination of blood keto-acid concentrations of young adults and institutionalized elderly people, divided into age groups Four keto-acids (alpha-ketoisocaproate, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, and pyruvate) were derivatized with o-phenylenediamine to give fluorescent derivatives. After the sample preparation step (75 min to prepare 20 samples), the derivatives were separated chromatographically on a reversed-phase column using a binary gradient. The fluorometric detection of the four keto-acids was rapid, <12 min. The method is repeatable and reproducible: the CVs were <6% and <11%, respectively, for each of the keto-acids. We found n...
To investigate appropriate mode and daily dose of enteral ornithine alpha-ketoglutarate (OKG) adm... more To investigate appropriate mode and daily dose of enteral ornithine alpha-ketoglutarate (OKG) administration, 54 burn patients (total burn surface area: 20-50%) were included in a randomized controlled trial and assigned to receive either a supplement of OKG (10, 20 or 30 g/d) as bolus or continuous infusion, or a continuous infusion of an isonitrogenous amount of a soy protein mixture (Protil-1: 10, 20 or 30 g/d) in addition to their enteral diet. The influence of these treatments on clinical outcome and biological indices was evaluated. OKG administration significantly improved nitrogen balance and reduced 3-methylhistidine and hydroxyproline urinary elimination. This was associated with a gradual rise in plasma glutamine over time. Given as a bolus, OKG significantly improved wound healing, assessed both clinically [day of last graft: (mean +/- SEM) OKG bolus 23.7 +/- 2.1 d versus Protil-1, 39.9 +/- 9.9 d; P < 0.05] and by hydroxyproline excretion, and biological markers of ni...
ABSTRACT Increase in life expendancy and global aging of the population have led to increased int... more ABSTRACT Increase in life expendancy and global aging of the population have led to increased interest in the aging process. A better understanding of aging-related modifications of meta-bolism is needed. For example, aging is an independent risk factor in critically ill patients. Allowing for illnesses whose frequency increases with age (obesity, NIDDM, cardiovascular disease), this may result from impaired metabolic response to hormones. This review present the current literature data concerning the evolution of the responsiveness to anabolic (insulin) and catabolic hormones (glucagon, glucocorticoids, catecholamines and thyroid hormones) with aging. Although some studies indicate a decrease in the responsiveness to various hormones, these modifications are moderate and their consequences are difficult to ascertain given the influence of confounding factors such as abnormal energy metabolism linked to dietary habits and life-style.
Enhancement of depressed plasma concentrations of glutamine and arginine is associated with bette... more Enhancement of depressed plasma concentrations of glutamine and arginine is associated with better clinical outcome. Supplementation of glutamine might be a way to provide the patient with glutamine, and also arginine, because glutamine provides the kidney with citrulline, from which the kidney produces arginine when plasma levels of arginine are low. The aim of the present study was to investigate the parenteral and enteral response of the administered dipeptide Ala-Gln, glutamine, citrulline and arginine. Therefore, seven patients received 20 g Ala-Gln, administered over 4 h, parenterally or enterally, on two separate occasions. Arterial blood samples were taken before and during the administration of Ala-Gln. ANOVA and a paired t test were used to test differences (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05). Ala-Gln was undetectable with enteral administration, whereas Ala-Gln remained stable at a plasma concentration of 268 micromol/l throughout parenteral infusion and rapidly decreased towards zero after infusion was stopped. The highest level of glutamine was observed with parenteral infusion of the dipeptide, although enteral infusion also significantly increased plasma levels of glutamine. The highest plasma response of citrulline was observed with the enteral administration of the dipeptide, although parenteral administration also increased plasma levels of citrulline. Plasma arginine increased significantly with parenteral infusion, but not with enteral administration of Ala-Gln. In conclusion, administrations of Ala-Gln, parenteral or enteral, resulted in an increased plasma glutamine response, as compared with baseline. Interestingly, in spite of the high availability of citrulline with enteral administration of the dipeptide, only parenteral infusion of Ala-Gln increased plasma arginine concentration.
Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via ant... more Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via anti-oxidative defences. The aim of this study was to evaluate the protective effect of these AAs on warm ischaemia-reperfusion (I/R) injury in the isolated perfused rat liver. Livers from fasted male Sprague-Dawley rats were isolated and perfused without (control group) or with (AP group) a mixture of regulatory AAs (glutamine, histidine, leucine, methionine, proline, phenylalanine, tryptophan and alanine). After 45 min of perfusion, warm ischaemia was induced for 45 min by clamping the portal vein catheter; thereafter, reperfusion was performed for 30 min. TNF-alpha production was significantly lower in the AP group during reperfusion ( 39+/-7 versus AP: 16+/-2 pg min-1 g-1, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), and lactate dehydrogenase (LDH) release decreased significantly during the last 15 min of reperfusion ( 0.13+/-0.03 versus AP: 0.04+/-0.02 IU min-1 g-1, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05), despite similar levels of oxidative stress. The addition of regulatory AAs was not associated with variations in portal flow, bile flow, hepatic glucose or urea metabolism. However, significant changes in intrahepatic glutamine ( 1.4+/-0.2 versus AP: 2.6+/-0.5 micromol g-1, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) together with higher glutamate release in the AP group ( 10.2+/-5.4 versus AP: 42.6+/-10.9 nmol min-1 g-1, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) indicated modifications in nitrogen metabolism. Taken together, the lower TNF-alpha production, suggesting decreased inflammatory response, the decrease in LDH release in the AP group, demonstrating a better preservation of liver viability, and the increase in hepatic glutamine indicate that AAs play an important role in the liver&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s response to I/R.
We previously demonstrated that ornithine alpha-ketoglutarate (OKG), known for its anabolic prope... more We previously demonstrated that ornithine alpha-ketoglutarate (OKG), known for its anabolic properties, induces insulin secretion in vitro. The present study was undertaken to further characterize this effect in vivo and investigate a possible interaction with glucose both in vivo and in vitro. Male Wistar rats received an intravenous bolus of OKG (25 mg/kg) and/or glucose (0.8 g/kg) or saline, and their plasma insulin and glucose levels were monitored for 30 minutes. OKG alone increased plasma insulin to a similar extent to glucose. In combination with glucose, OKG significantly increased glucose-induced insulin secretion in vivo and in vitro, and led to a significant increase in glucose utilization in vivo. The absence of significant variations in plasma arginine and glutamine suggests a direct effect of OKG on the pancreas. To assess the involvement of the synthesis of nitric oxide and glutamine in OKG-induced insulin secretion, the experiments were repeated in the presence of inhibitors of these 2 pathways, respectively L-nitroarginine-methylester (L-NAME) and methionine sulfoximine (MSO). Both inhibitors were able significantly to reduce OKG-induced insulin secretion without affecting either basal or glucose-induced insulin release. Thus OKG acts directly with glucose on islets to induce insulin secretion via mechanisms involving NO and glutamine synthesis. In addition, our results suggest that OKG and glucose act via separate pathways.
Conflicting data on the effects of amino acids on biliary function led us to investigate their in... more Conflicting data on the effects of amino acids on biliary function led us to investigate their interaction with taurocholate in the perfused rat liver model. To investigate the influence of amino acids on the bile acid-independent component of bile flow, 12 livers were perfused with (n = 6) and without (n = 6) amino acid addition from t30 min. For the study of bile acid-dependent bile flow, 24 livers were perfused under 8 experimental conditions according to the perfusate taurocholate concentration (12.5, 25, 37.5 or 50 microM) and whether amino acids were or were not added from t30 min. In the absence of taurocholate, amino acids induced a 40% (p&amp;amp;lt;0.01) decrease in bile flow together with an increase in hepatic water content (17.8%, p&amp;amp;lt; 0.05). Thus, amino acids exert an inhibitory effect on bile acid-independent bile flow despite the postulated cell swelling-dependent increase in bile flow. When livers were perfused at various taurocholate concentrations, amino acids induced, in addition to their inhibitory effect on bile acid-independent bile flow, a significant increase in taurocholate apparent choleretic activity (13.2 microl/micromol vs. 10.6 microl/micromol; p = 0.05), while taurocholate intrinsic clearance was significantly decreased (4.5+/-1.2 ml x min(-1) x g(-1) vs. 6.1+/-1.3 ml x min(-1) x g(-1); p&amp;amp;lt;0.01). These data suggest that at physiological bile acid concentrations amino acids exert an inhibitory effect on both bile acid-dependent and- independent bile flow, whereas at higher taurocholate concentrations this inhibitory effect disappears, probably because of cell swelling-dependent mechanisms.
Background/Aims: Energy charge and capacity for adenosine triphosphate (ATP) synthesis have been ... more Background/Aims: Energy charge and capacity for adenosine triphosphate (ATP) synthesis have been demonstrated to play a major role in the maintenance of organ function after liver preservation for transplantation. The aim of this study was to evaluate whether a supply of liposomally-entrapped ATP during preservation could improve the energy state and metabolism of cold-stored rat liver.Methods: In the first set
Increased susceptibility to infections in obese patients may be related to decreased availability... more Increased susceptibility to infections in obese patients may be related to decreased availability of arginine and glutamine, which may affect immune cell functions. Our aim was to evaluate the in vitro effects of these amino acids on the function of macrophages from obese insulin-resistant Zucker rats. Macrophages, isolated from male Zucker obese or lean rats by peritoneal lavage, were incubated in Dulbecco&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s modified Eagle medium (DMEM) without arginine or glutamine. Arginine or glutamine was added to the medium at increasing final concentrations (0, 0.25, 0.5, 1 or 2 mM). After stimulation by lipopolysaccharide (LPS) from E. coli (40 microg/ml), productions of tumour necrosis factor alpha (TNFalpha) and of nitric oxide (NO) were measured after 3 or 48 h incubation, respectively. NO production, lower in macrophages from obese rats, decreased in macrophages from lean rats (0 mM: 2,423 +/- 1,174 vs. 2 mM: 198 +/- 31 microM/mg protein/24 h; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), but not in those from obese rats, when glutamine was added. TNFalpha production, lower in macrophages from obese rats, was inversely correlated with glutamine concentration. In the presence of arginine, NO production was constantly higher in macrophages from obese rats. It peaked at 0.5 mM arginine and decreased thereafter in both groups. TNFalpha production in macrophages from lean rats was unaffected by arginine, but decreased in macrophages from obese rats (0 mM: 1920 +/- 450 vs. 2 mM: 810 +/- 90 microM/mg protein/3 h; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). These results suggest that abnormalities in cell signalling or in arginine and glutamine metabolism in macrophages of obese rats, resulting in decreased TNFalpha production and increased NO release, may contribute to increased susceptibility to infection in insulin-resistant states.
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Papers by Jean-pascal Bandt