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Arteriovenous Blood Metabolomics: A Readout of Intra-Tissue Metabostasis.

Ivanisevic J, Elias D, Deguchi H, Averell PM, Kurczy M, Johnson CH, Tautenhahn R, Zhu Z, Watrous J, Jain M, Griffin J, Patti GJ, Siuzdak G - Sci Rep (2015)

Bottom Line: Global profiling of paired arterial and venous plasma from 20 healthy individuals, followed up by targeted analysis made it possible to measure subtle (<2 fold), yet highly statistically significant and physiologically important differences in water soluble human plasma metabolome.While we detected changes in lactic acid, alanine, glutamine, and glutamate as expected from skeletal muscle activity, a number of unanticipated metabolites were also determined to be significantly altered including Krebs cycle intermediates, amino acids that have not been previously implicated in transport, and a few oxidized fatty acids.This study provides the most comprehensive assessment of metabolic changes in the blood during circulation to date and suggests that such profiling approach may offer new insights into organ homeostasis and organ specific pathology.

View Article: PubMed Central - PubMed

Affiliation: Center for Metabolomics and Mass Spectrometry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States.

ABSTRACT
The human circulatory system consists of arterial blood that delivers nutrients to tissues, and venous blood that removes the metabolic by-products. Although it is well established that arterial blood generally has higher concentrations of glucose and oxygen relative to venous blood, a comprehensive biochemical characterization of arteriovenous differences has not yet been reported. Here we apply cutting-edge, mass spectrometry-based metabolomic technologies to provide a global characterization of metabolites that vary in concentration between the arterial and venous blood of human patients. Global profiling of paired arterial and venous plasma from 20 healthy individuals, followed up by targeted analysis made it possible to measure subtle (<2 fold), yet highly statistically significant and physiologically important differences in water soluble human plasma metabolome. While we detected changes in lactic acid, alanine, glutamine, and glutamate as expected from skeletal muscle activity, a number of unanticipated metabolites were also determined to be significantly altered including Krebs cycle intermediates, amino acids that have not been previously implicated in transport, and a few oxidized fatty acids. This study provides the most comprehensive assessment of metabolic changes in the blood during circulation to date and suggests that such profiling approach may offer new insights into organ homeostasis and organ specific pathology.

No MeSH data available.


Related in: MedlinePlus

Simplified scheme of main biochemical transformations taking place at the skeletal muscle level of the circulatory system.The observed significant arteriovenous metabolite changes that fit into the context are pointed out in red (glucose, glutamate, aspartate, serine) and blue (lactate, alanine, glutamine and succinate). The uptake pattern of glucose, glutamate, aspartate and serine (in addition to being formed by breakdown of muscle proteins) demonstrates their use by muscle cells as supply for TCA cycle as well as nitrogen and/or carbon donors in the synthesis of alanine, glutamine and other amino acids. Lactate, alanine, glutamine and succinate produced by muscle cells are released into the venous blood. α-KG—α-ketoglutarate, OAA—oxaloacetate, αAA—α-aminoacids, αKA—α-ketoacids. Drawing of a muscle has been downloaded from Science Slides for MS PowerPoint (VisiScience Corporation).
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f6: Simplified scheme of main biochemical transformations taking place at the skeletal muscle level of the circulatory system.The observed significant arteriovenous metabolite changes that fit into the context are pointed out in red (glucose, glutamate, aspartate, serine) and blue (lactate, alanine, glutamine and succinate). The uptake pattern of glucose, glutamate, aspartate and serine (in addition to being formed by breakdown of muscle proteins) demonstrates their use by muscle cells as supply for TCA cycle as well as nitrogen and/or carbon donors in the synthesis of alanine, glutamine and other amino acids. Lactate, alanine, glutamine and succinate produced by muscle cells are released into the venous blood. α-KG—α-ketoglutarate, OAA—oxaloacetate, αAA—α-aminoacids, αKA—α-ketoacids. Drawing of a muscle has been downloaded from Science Slides for MS PowerPoint (VisiScience Corporation).

Mentions: The differences in arterial vs. venous plasma, primarily observed in amino acid and other organic acid levels, appear to mainly reflect the metabolic requirements of muscle tissue in a postabsorptive state, the period following an overnight fast when the blood is usually sampled in the process of clinical examination. The postabsorptive metabolic state in muscle is primarily associated with an increase in glycolysis, resulting in an excess of pyruvate734. Our observations indicate that the excess of pyruvate independently governs the production of lactate, and the production of alanine via transamination of glutamate (Fig. 6). The significantly higher lactate level in venous plasma (referred to as negative arteriovenous balance) is likely associated with its release to venous plasma as the end-product of pyruvate conversion. This observation is congruent with earlier findings on peripheral lactate levels3536 and is representative of incomplete glycolysis even at rest, in aerobic conditions at early fasting metabolic state (Fig. 6). It also demonstrates the role of lactate as a mobile nutrient (gluconeogenic metabolite) that is further taken up by the liver to regenerate glucose and complete the Cori cycle235. The observations of a significantly lower levels of glutamate (positive AV balance), and increased levels of alanine (negative AV balance) and glutamine (negative AV balance) in venous plasma imply the uptake of glutamate (by muscle) and the production and release of alanine and glutamine by transamination. While early metabolic studies demonstrated the synthesis of glutamine and alanine, as two main gluconeogenic amino acids formed by transamination of α-ketoacids (pyruvate and oxaloacetate, Fig. 6) in muscle837, the uptake pattern of glutamate by human muscle has been reported only by Marliss et al. using enzymatic assays38. Our results reflect a significant uptake pattern of glutamate suggesting that glutamate is the major amino acid precursor, primarily as a nitrogen donor, in the synthesis of alanine and glutamine. Furthermore, a significant positive arteriovenous difference was observed for aspartate, suggesting that aspartate could play an important role in glutamate supply in the muscle cells. The uptake of aspartate by muscle is a new finding that is likely coupled to excess of α-ketoglutarate, produced by transamination of glutamate (Fig. 6). The excess of α-ketoglutarate could lead the amino transfer from aspartate to glutamate and concurrently replenish the TCA-cycle (Fig. 6). Early tracing experiments using rat muscle in vitro indicate that glutamate, aspartate and specific branched amino acids (isoleucine and valine) should enter the TCA cycle and serve as carbon skeleton and nitrogen supply for glutamine synthesis78, however only the uptake pattern of glutamate has been previously reported38, The uptake pattern of serine, reflected as lower concentration in venous blood, is a new finding as well, which may imply its usage for pyruvate anaplerosis, as a non-carbohydrate precursor, by serine dehydratase mediated direct conversion to pyruvate (Fig. 6). This finding supports the original formulation of the glucose-alanine cycle after which pyruvate is derived from glucose as well as other metabolized amino acids37. Tracer experiments in humans in vivo have implied that the carbon atoms of alanine are mostly derived from plasma glucose and muscle glycogen839 and that glutamine should be a major gluconeogenic precursor for a positive transfer of new carbon to the glucose pool78, originating primarily from protein-derived amino acids. Therefore, the hypothesis of serine deamination for pyruvate anaplerosis needs to be further investigated.


Arteriovenous Blood Metabolomics: A Readout of Intra-Tissue Metabostasis.

Ivanisevic J, Elias D, Deguchi H, Averell PM, Kurczy M, Johnson CH, Tautenhahn R, Zhu Z, Watrous J, Jain M, Griffin J, Patti GJ, Siuzdak G - Sci Rep (2015)

Simplified scheme of main biochemical transformations taking place at the skeletal muscle level of the circulatory system.The observed significant arteriovenous metabolite changes that fit into the context are pointed out in red (glucose, glutamate, aspartate, serine) and blue (lactate, alanine, glutamine and succinate). The uptake pattern of glucose, glutamate, aspartate and serine (in addition to being formed by breakdown of muscle proteins) demonstrates their use by muscle cells as supply for TCA cycle as well as nitrogen and/or carbon donors in the synthesis of alanine, glutamine and other amino acids. Lactate, alanine, glutamine and succinate produced by muscle cells are released into the venous blood. α-KG—α-ketoglutarate, OAA—oxaloacetate, αAA—α-aminoacids, αKA—α-ketoacids. Drawing of a muscle has been downloaded from Science Slides for MS PowerPoint (VisiScience Corporation).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525490&req=5

f6: Simplified scheme of main biochemical transformations taking place at the skeletal muscle level of the circulatory system.The observed significant arteriovenous metabolite changes that fit into the context are pointed out in red (glucose, glutamate, aspartate, serine) and blue (lactate, alanine, glutamine and succinate). The uptake pattern of glucose, glutamate, aspartate and serine (in addition to being formed by breakdown of muscle proteins) demonstrates their use by muscle cells as supply for TCA cycle as well as nitrogen and/or carbon donors in the synthesis of alanine, glutamine and other amino acids. Lactate, alanine, glutamine and succinate produced by muscle cells are released into the venous blood. α-KG—α-ketoglutarate, OAA—oxaloacetate, αAA—α-aminoacids, αKA—α-ketoacids. Drawing of a muscle has been downloaded from Science Slides for MS PowerPoint (VisiScience Corporation).
Mentions: The differences in arterial vs. venous plasma, primarily observed in amino acid and other organic acid levels, appear to mainly reflect the metabolic requirements of muscle tissue in a postabsorptive state, the period following an overnight fast when the blood is usually sampled in the process of clinical examination. The postabsorptive metabolic state in muscle is primarily associated with an increase in glycolysis, resulting in an excess of pyruvate734. Our observations indicate that the excess of pyruvate independently governs the production of lactate, and the production of alanine via transamination of glutamate (Fig. 6). The significantly higher lactate level in venous plasma (referred to as negative arteriovenous balance) is likely associated with its release to venous plasma as the end-product of pyruvate conversion. This observation is congruent with earlier findings on peripheral lactate levels3536 and is representative of incomplete glycolysis even at rest, in aerobic conditions at early fasting metabolic state (Fig. 6). It also demonstrates the role of lactate as a mobile nutrient (gluconeogenic metabolite) that is further taken up by the liver to regenerate glucose and complete the Cori cycle235. The observations of a significantly lower levels of glutamate (positive AV balance), and increased levels of alanine (negative AV balance) and glutamine (negative AV balance) in venous plasma imply the uptake of glutamate (by muscle) and the production and release of alanine and glutamine by transamination. While early metabolic studies demonstrated the synthesis of glutamine and alanine, as two main gluconeogenic amino acids formed by transamination of α-ketoacids (pyruvate and oxaloacetate, Fig. 6) in muscle837, the uptake pattern of glutamate by human muscle has been reported only by Marliss et al. using enzymatic assays38. Our results reflect a significant uptake pattern of glutamate suggesting that glutamate is the major amino acid precursor, primarily as a nitrogen donor, in the synthesis of alanine and glutamine. Furthermore, a significant positive arteriovenous difference was observed for aspartate, suggesting that aspartate could play an important role in glutamate supply in the muscle cells. The uptake of aspartate by muscle is a new finding that is likely coupled to excess of α-ketoglutarate, produced by transamination of glutamate (Fig. 6). The excess of α-ketoglutarate could lead the amino transfer from aspartate to glutamate and concurrently replenish the TCA-cycle (Fig. 6). Early tracing experiments using rat muscle in vitro indicate that glutamate, aspartate and specific branched amino acids (isoleucine and valine) should enter the TCA cycle and serve as carbon skeleton and nitrogen supply for glutamine synthesis78, however only the uptake pattern of glutamate has been previously reported38, The uptake pattern of serine, reflected as lower concentration in venous blood, is a new finding as well, which may imply its usage for pyruvate anaplerosis, as a non-carbohydrate precursor, by serine dehydratase mediated direct conversion to pyruvate (Fig. 6). This finding supports the original formulation of the glucose-alanine cycle after which pyruvate is derived from glucose as well as other metabolized amino acids37. Tracer experiments in humans in vivo have implied that the carbon atoms of alanine are mostly derived from plasma glucose and muscle glycogen839 and that glutamine should be a major gluconeogenic precursor for a positive transfer of new carbon to the glucose pool78, originating primarily from protein-derived amino acids. Therefore, the hypothesis of serine deamination for pyruvate anaplerosis needs to be further investigated.

Bottom Line: Global profiling of paired arterial and venous plasma from 20 healthy individuals, followed up by targeted analysis made it possible to measure subtle (<2 fold), yet highly statistically significant and physiologically important differences in water soluble human plasma metabolome.While we detected changes in lactic acid, alanine, glutamine, and glutamate as expected from skeletal muscle activity, a number of unanticipated metabolites were also determined to be significantly altered including Krebs cycle intermediates, amino acids that have not been previously implicated in transport, and a few oxidized fatty acids.This study provides the most comprehensive assessment of metabolic changes in the blood during circulation to date and suggests that such profiling approach may offer new insights into organ homeostasis and organ specific pathology.

View Article: PubMed Central - PubMed

Affiliation: Center for Metabolomics and Mass Spectrometry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States.

ABSTRACT
The human circulatory system consists of arterial blood that delivers nutrients to tissues, and venous blood that removes the metabolic by-products. Although it is well established that arterial blood generally has higher concentrations of glucose and oxygen relative to venous blood, a comprehensive biochemical characterization of arteriovenous differences has not yet been reported. Here we apply cutting-edge, mass spectrometry-based metabolomic technologies to provide a global characterization of metabolites that vary in concentration between the arterial and venous blood of human patients. Global profiling of paired arterial and venous plasma from 20 healthy individuals, followed up by targeted analysis made it possible to measure subtle (<2 fold), yet highly statistically significant and physiologically important differences in water soluble human plasma metabolome. While we detected changes in lactic acid, alanine, glutamine, and glutamate as expected from skeletal muscle activity, a number of unanticipated metabolites were also determined to be significantly altered including Krebs cycle intermediates, amino acids that have not been previously implicated in transport, and a few oxidized fatty acids. This study provides the most comprehensive assessment of metabolic changes in the blood during circulation to date and suggests that such profiling approach may offer new insights into organ homeostasis and organ specific pathology.

No MeSH data available.


Related in: MedlinePlus