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Heden TD, Liu Y, Kanaley JA. Exercise timing and blood lactate concentrations in individuals with type 2 diabetes. Appl Physiol Nutr Metab 2017; 42:732-737. [DOI: 10.1139/apnm-2016-0382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to characterize how resistance exercise prior to or after a meal alters fasting and postprandial blood lactate concentrations in individuals with type 2 diabetes. Obese individuals with type 2 diabetes (N = 12) completed three 2-day trials, including (i) no exercise (NoEx), (ii) resistance exercise prior to dinner (Ex-M), and (iii) resistance exercise beginning at 45 min postdinner (M-Ex). During day 1 of each trial, fasting and postprandial blood lactate concentrations, perceived exertion, and substrate oxidation were measured, and subsequently on day 2 the following morning fasting blood lactate was measured. The premeal lactate incremental area under the curve (iAUC) during Ex-M (109 ± 66 mmol·L−1·1.6 h−1) was over 100-fold greater (P < 0.01) compared with NoEx (−15 ± 24 mmol·L−1·1.6 h−1) and M-Ex (−2 ± 18 mmol·L−1·1.6 h−1). The postprandial lactate iAUC during M-Ex (304 ± 116 mmol·L−1·4 h−1) was over 2-fold greater (P < 0.01) compared with NoEx (149 ± 74 mmol·L−1·4 h−1) and Ex-M (−140 ± 196 mmol·L−1·4 h−1). Average lactate during exercise was ∼45% greater (P = 0.03) during M-Ex (3.2 ± 0.9 mmol/L) compared with Ex-M (2.2 ± 0.9 mmol/L), but the change in lactate during Ex-M (2.4 ± 1.6 mmol/L) or M-Ex (2.3 ± 1.3 mmol/L) was not different (P > 0.05). Perceived exertion, substrate oxidation, or fasting blood lactate concentrations the day after testing were not different between trials. Blood lactate concentrations during acute resistance exercise are greater when exercise is performed in the postprandial period. Acute resistance exercise performed the night prior does not alter fasting blood lactate concentrations the following morning.
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Affiliation(s)
- Timothy D. Heden
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
| | - Ying Liu
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
| | - Jill A. Kanaley
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
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2
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Oliveira LF, de Salles Painelli V, Nemezio K, Gonçalves LS, Yamaguchi G, Saunders B, Gualano B, Artioli GG. Chronic lactate supplementation does not improve blood buffering capacity and repeated high-intensity exercise. Scand J Med Sci Sports 2016; 27:1231-1239. [DOI: 10.1111/sms.12792] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2016] [Indexed: 11/27/2022]
Affiliation(s)
- L. F. Oliveira
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - V. de Salles Painelli
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - K. Nemezio
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - L. S. Gonçalves
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - G. Yamaguchi
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - B. Saunders
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - B. Gualano
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
| | - G. G. Artioli
- Applied Physiology & Nutrition Research Group; University of Sao Paulo; São Paulo Brazil
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Lancha Junior AH, Painelli VDS, Saunders B, Artioli GG. Nutritional Strategies to Modulate Intracellular and Extracellular Buffering Capacity During High-Intensity Exercise. Sports Med 2016; 45 Suppl 1:S71-81. [PMID: 26553493 PMCID: PMC4672007 DOI: 10.1007/s40279-015-0397-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Intramuscular acidosis is a contributing factor to fatigue during high-intensity exercise. Many nutritional strategies aiming to increase intra- and extracellular buffering capacity have been investigated. Among these, supplementation of beta-alanine (~3–6.4 g/day for 4 weeks or longer), the rate-limiting factor to the intramuscular synthesis of carnosine (i.e. an intracellular buffer), has been shown to result in positive effects on exercise performance in which acidosis is a contributing factor to fatigue. Furthermore, sodium bicarbonate, sodium citrate and sodium/calcium lactate supplementation have been employed in an attempt to increase the extracellular buffering capacity. Although all attempts have increased blood bicarbonate concentrations, evidence indicates that sodium bicarbonate (0.3 g/kg body mass) is the most effective in improving high-intensity exercise performance. The evidence supporting the ergogenic effects of sodium citrate and lactate remain weak. These nutritional strategies are not without side effects, as gastrointestinal distress is often associated with the effective doses of sodium bicarbonate, sodium citrate and calcium lactate. Similarly, paresthesia (i.e. tingling sensation of the skin) is currently the only known side effect associated with beta-alanine supplementation, and it is caused by the acute elevation in plasma beta-alanine concentration after a single dose of beta-alanine. Finally, the co-supplementation of beta-alanine and sodium bicarbonate may result in additive ergogenic gains during high-intensity exercise, although studies are required to investigate this combination in a wide range of sports.
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Affiliation(s)
- Antonio Herbert Lancha Junior
- Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sport, University of São Paulo, Av. Mello de Moraes, 65 Butanta, São Paulo, SP, 05508-030, Brazil.
| | - Vitor de Salles Painelli
- Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sport, University of São Paulo, Av. Mello de Moraes, 65 Butanta, São Paulo, SP, 05508-030, Brazil
| | - Bryan Saunders
- Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sport, University of São Paulo, Av. Mello de Moraes, 65 Butanta, São Paulo, SP, 05508-030, Brazil
| | - Guilherme Giannini Artioli
- Laboratory of Applied Nutrition and Metabolism, School of Physical Education and Sport, University of São Paulo, Av. Mello de Moraes, 65 Butanta, São Paulo, SP, 05508-030, Brazil
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Jin ES, Sherry AD, Malloy CR. Interaction between the pentose phosphate pathway and gluconeogenesis from glycerol in the liver. J Biol Chem 2014; 289:32593-603. [PMID: 25288790 DOI: 10.1074/jbc.m114.577692] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
After exposure to [U-(13)C3]glycerol, the liver produces primarily [1,2,3-(13)C3]- and [4,5,6-(13)C3]glucose in equal proportions through gluconeogenesis from the level of trioses. Other (13)C-labeling patterns occur as a consequence of alternative pathways for glucose production. The pentose phosphate pathway (PPP), metabolism in the citric acid cycle, incomplete equilibration by triose phosphate isomerase, or the transaldolase reaction all interact to produce complex (13)C-labeling patterns in exported glucose. Here, we investigated (13)C labeling in plasma glucose in rats given [U-(13)C3]glycerol under various nutritional conditions. Blood was drawn at multiple time points to extract glucose for NMR analysis. Because the transaldolase reaction and incomplete equilibrium by triose phosphate isomerase cannot break a (13)C-(13)C bond within the trioses contributing to glucose, the appearance of [1,2-(13)C2]-, [2,3-(13)C2]-, [5,6-(13)C2]-, and [4,5-(13)C2]glucose provides direct evidence for metabolism of glycerol in the citric acid cycle or the PPP but not an influence of either triose phosphate isomerase or the transaldolase reaction. In all animals, [1,2-(13)C2]glucose/[2,3-(13)C2]glucose was significantly greater than [5,6-(13)C2]glucose/[4,5-(13)C2]glucose, a relationship that can only arise from gluconeogenesis followed by passage of substrates through the PPP. In summary, the hepatic PPP in vivo can be detected by (13)C distribution in blood glucose after [U-(13)C3]glycerol administration.
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Affiliation(s)
- Eunsook S Jin
- From the Advanced Imaging Research Center and Departments of Internal Medicine and
| | - A Dean Sherry
- From the Advanced Imaging Research Center and Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, the Department of Chemistry, University of Texas at Dallas, Richardson, Texas 75080, and
| | - Craig R Malloy
- From the Advanced Imaging Research Center and Departments of Internal Medicine and Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, the Veterans Affairs North Texas Health Care System, Dallas, Texas 75216
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Parallel labeling experiments and metabolic flux analysis: Past, present and future methodologies. Metab Eng 2012; 16:21-32. [PMID: 23246523 DOI: 10.1016/j.ymben.2012.11.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Revised: 11/09/2012] [Accepted: 11/21/2012] [Indexed: 01/22/2023]
Abstract
Radioactive and stable isotopes have been applied for decades to elucidate metabolic pathways and quantify carbon flow in cellular systems using mass and isotope balancing approaches. Isotope-labeling experiments can be conducted as a single tracer experiment, or as parallel labeling experiments. In the latter case, several experiments are performed under identical conditions except for the choice of substrate labeling. In this review, we highlight robust approaches for probing metabolism and addressing metabolically related questions though parallel labeling experiments. In the first part, we provide a brief historical perspective on parallel labeling experiments, from the early metabolic studies when radioisotopes were predominant to present-day applications based on stable-isotopes. We also elaborate on important technical and theoretical advances that have facilitated the transition from radioisotopes to stable-isotopes. In the second part of the review, we focus on parallel labeling experiments for (13)C-metabolic flux analysis ((13)C-MFA). Parallel experiments offer several advantages that include: tailoring experiments to resolve specific fluxes with high precision; reducing the length of labeling experiments by introducing multiple entry-points of isotopes; validating biochemical network models; and improving the performance of (13)C-MFA in systems where the number of measurements is limited. We conclude by discussing some challenges facing the use of parallel labeling experiments for (13)C-MFA and highlight the need to address issues related to biological variability, data integration, and rational tracer selection.
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Browning JD, Burgess SC. Use of (2)H(2)O for estimating rates of gluconeogenesis: determination and correction of error due to transaldolase exchange. Am J Physiol Endocrinol Metab 2012; 303:E1304-12. [PMID: 23032685 PMCID: PMC3774082 DOI: 10.1152/ajpendo.00306.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of deuterated water as a method to measure gluconeogenesis has previously been well validated and is reflective of normal human physiology. However, there has been concern since the method was first introduced that transaldolase exchange may lead to the overestimation of gluconeogenesis. We examined the impact of transaldolase exchange on the estimation of gluconenogenesis using the deuterated water method under a variety of physiological conditions in humans by using the gluconeogenic tracer [U-(13)C]propionate, (2)H(2)O, and (2)H/(13)C nuclear magnetic resonance (NMR) spectroscopy. When [U-(13)C]propionate was used, (13)C labeling inequality occurred between the top and bottom halves of glucose in individuals fasted for 12-24 h who were weight stable (n = 18) or had lost weight via calorie restriction (n = 7), consistent with transaldolase exchange. Similar analysis of glucose standards revealed no significant difference in the total (13)C enrichment between the top and bottom halves of glucose, indicating that the differences detected were biological, not analytical, in origin. This labeling inequality was attenuated by extending the fasting period to 48 h (n = 12) as well as by dietary carbohydrate restriction (n = 7), both conditions associated with decreased glycogenolysis. These findings were consistent with a transaldolase effect; however, the resultant overestimation of gluconeogenesis in the overnight-fasted state was modest (7-12%), leading to an error of 14-24% that was easily correctable by using either a simultaneous (13)C gluconeogenic tracer or a correction nomogram generated from data in the present study.
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Affiliation(s)
- Jeffrey D Browning
- The Advanced Imaging Research Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA.
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Thompson SN. Dietary fat mediates hyperglycemia and the glucogenic response to increased protein consumption in an insect, Manduca sexta L. Biochim Biophys Acta Gen Subj 2004; 1673:208-16. [PMID: 15279893 DOI: 10.1016/j.bbagen.2004.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2004] [Revised: 05/04/2004] [Accepted: 05/10/2004] [Indexed: 10/26/2022]
Abstract
Many insects display non-homeostatic regulation over blood sugar level. The concentration of trehalose varies dramatically depending on physiological and nutritional state. In the absence of dietary carbohydrate, blood trehalose in larvae of the lepidopteran insect Manduca sexta is maintained by gluconeogenesis and is dependent on dietary protein consumption. In the present study, the effect of dietary fat on the glucogenic response of insects to increased dietary protein was examined by NMR analysis of (2-13C)pyruvate metabolism. Last instar larvae were maintained on a carbohydrate-free chemically defined artificial diet having variable levels of casein with and without corn oil. Gluconeogenic flux, the ratio of the rate of gluconeogenesis to the rate of glycolysis, was estimated from the 13C distribution in trehalose arising by gluconeogenesis and the 13C enrichment of alanine due to pyruvate cycling. Insects grew well on carbohydrate-free diets and growth increased with increasing dietary protein level. At all dietary protein levels, larvae grew better on diets with fat. Without dietary fat, larvae were glucogenic but displayed low blood trehalose concentrations, <30 mM, regardless of protein consumption. When fat was included in the diet, however, gluconeogenic flux and blood trehalose level increased sharply in response to increased dietary protein level, with trehalose concentrations >50 mM at higher levels of protein consumption. When offered a choice of a high carbohydrate and a high protein diet, larvae maintained on diets with fat displayed a food preference related to blood sugar level. Those with low blood sugar fed on carbohydrate, while those with high blood sugar preferred protein. Trehalose synthesized from (2-13C)pyruvate exhibited asymmetry in the 13C distribution in individual glucose molecules, indicating a disequilibrium at the triose phosphate isomerase-catalyzed step of the gluconeogenic pathway. In trehalose from larvae on diets with fat, the asymmetric 13C distribution was higher than in trehalose from insects on diets lacking fat. This may partially result from isotopic disequilibrium when unenriched glycerol is metabolized to dihydroxyacetone phosphate following fat hydrolysis. The asymmetry in 13C distribution, however, also occurred in insects on diets without fat and decreased with increased gluconeogenic flux suggesting that true disequilibrium between the triose phosphates is the principal reason for the asymmetry.
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Affiliation(s)
- S N Thompson
- Analytical Chemistry Instrumentation Facility and Department of Entomology, University of California, Riverside, CA 92521, USA.
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Thompson SN, Borchardt DB. Glucogenic blood sugar formation in an insect Manduca sexta L.: asymmetric synthesis of trehalose from 13C enriched pyruvate. Comp Biochem Physiol B Biochem Mol Biol 2003; 135:461-71. [PMID: 12831766 DOI: 10.1016/s1096-4959(03)00110-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gluconeogenesis and blood sugar formation were examined in Manduca sexta, fed carbohydrate- and fat-free diets with varying levels of casein. De novo carbohydrate synthesis was examined by nuclear magnetic resonance spectroscopy of the 13C enrichment in blood trehalose and alanine derived from (2-(13)C)pyruvate and (2,3-(13)C(2))pyruvate administered to 5th instar larvae. Gluconeogenic flux and blood trehalose concentration were positively correlated with protein consumption. On all diets, the 13C distribution in trehalose was asymmetric, with C6 more highly enriched than C1. The C6/C1 13C enrichment ratio, however, decreased with increased protein consumption and gluconeogenic flux. Although the asymmetric 13C enrichment pattern in trehalose is consistent with pentose cycling via the pentose phosphate pathway following de novo synthesis, experiments employing [2,3-(13)C(2)]pyruvate demonstrated that pentose cycling is not detected in insects under these nutritional conditions. Analysis of the multiplet NMR signal structure in trehalose due to spin-spin coupling between adjacent 13C enriched carbons showed the absence of uncoupling expected by pentose phosphate pathway activity. Here we suggest that the asymmetric 13C distribution in trehalose results from a disequilibrium of the triose phosphate isomerase-catalyzed reaction.
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Affiliation(s)
- S N Thompson
- Analytical Chemistry Instrumentation Facility and Department of Entomology, University of California, 3401 Watkins Drive, 92521, Riverside, CA, USA.
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Stunff CL, Bougnères PF. Alterations of plasma lactate and glucose metabolism in obese children. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:E814-20. [PMID: 8944666 DOI: 10.1152/ajpendo.1996.271.5.e814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Using a double stable isotope infusion method, we quantified plasma glucose and lactate inter-relationships in five recently obese children. Compared with five age-matched controls, obese children had an approximately 50% increase of total body lactate turnover [167 +/- 20 vs. 111 +/- 20 (SE) mg/min, P < 0.05]. The rate of lactate conversion to glucose was double the normal rate (96 +/- 21 vs. 46 +/- 10 mg/min, P < 0.05). Increased gluconeogenesis from plasma lactate correlated with total glucose production (r = 0.74), with plasma lactate contributing to 58% of glucose production in obese children vs. 38% in normal children (P < 0.05). Conversion into glucose correlated with the rate of lactate release in the circulation (r = 0.76). In turn, the obese children converted a larger fraction (35 +/- 2 vs. 27 +/- 2%, P < 0.02) and amount (58 +/- 10 vs. 34 +/- 5 mg/min, P < 0.05) of glucose into plasma lactate. The amount of lactate originating from plasma glucose correlated (r = 0.70) with lipid oxidation, which was increased in the obese children (58 +/- 4 vs. 23 +/- 5 mg/min, P < 0.02). Our data suggest that increased gluconeogenesis from lactate is associated with increased lipid oxidation and could contribute to the progressive development of insulin resistance and glucose intolerance in juvenile obesity.
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Affiliation(s)
- C L Stunff
- Institut National de la Santé et de la Recherche Médicale Unité 342, René Descartes University, Hôpital Saint Vincent de Paul, Paris, France
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Ekberg K, Chandramouli V, Kumaran K, Schumann WC, Wahren J, Landau BR. Gluconeogenesis and glucuronidation in liver in vivo and the heterogeneity of hepatocyte function. J Biol Chem 1995; 270:21715-7. [PMID: 7665589 DOI: 10.1074/jbc.270.37.21715] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In order to examine metabolic zonation in human liver, [2-14C]glycerol, which labels carbons 2 and 5 of glucose-6-P, and [1-14C]lactate, which labels carbons 3 and 4 of glucose-6-P, in the process of gluconeogenesis, were infused intravenously into healthy subjects who ingested acetaminophen and had fasted 36 h. Distributions of 14C were determined in glucose in blood and in the glucuronic acid moiety of acetaminophen glucuronide excreted in urine. Ratios of 14C in carbons 2 and 5 to 14C in carbons 3 and 4 were significantly higher in blood glucose than in glucuronide. Since glucose and glucuronic acid are formed from glucose-6-P in liver without randomization of carbon, the differences in the ratios indicate that the pool of glucose-6-P in liver is not homogeneous. The glucuronide sampled glucose-6-P with more label from lactate than glycerol compared to the glucose-6-P sampled by the glucose. The apparent explanation is the greater decrease in glycerol compared with lactate concentration as blood streams from the periportal to the perivenous zones of the liver lobule. Glucuronidation is then expressed in humans relatively more in the perivenous than periportal zones and gluconeogenesis from glycerol more in the periportal than perivenous zones.
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Affiliation(s)
- K Ekberg
- Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden
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11
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Bougnères PF, Rocchiccioli F, Nurjhan N, Zeller J. Stable isotope determination of plasma lactate conversion into glucose in fasting infants. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:E652-9. [PMID: 7733264 DOI: 10.1152/ajpendo.1995.268.4.e652] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To quantify lactate gluconeogenesis, we developed a gas chromatography-mass spectrometry method based on the infusion of [6,6-2H2]glucose and [3-13C]lactate tracers to 12 infants aged 1-25 mo fasting for 11.5 +/- 1.5 h. Both rates of appearance of plasma glucose (26.7 +/- 2.6 mumol.kg-1.min-1, 4.8 +/- 0.5 mg.kg-1.min-1) and lactate (30.8 +/- 3.1 mumol.kg-1.min-1, 2.8 +/- 0.3 mg.kg-1.min-1) were remarkably elevated compared with adult values. The interconversion of plasma lactate and glucose was determined by 1) measuring the incorporation of 13C from [3-13C]lactate into plasma glucose; 2) correcting for the metabolic exchange of carbon atoms in the tricarboxylic acid cycle. For this purpose, an additional group of six infants was infused with [3-13C]lactate, and the distribution of 13C at specific carbon positions in the glucose molecule was determined using relevant ions in the electron-impact mass spectrum of its 1,2,5,6-diisopropylidene-3-O-acetyl-alpha-furanosyl derivative; and 3) measuring the reverse conversion of glucose to lactate in five other infants infused with [1-13C]glucose. We found that 54 +/- 2% of glucose was derived from plasma lactate (14.4 +/- 1.3 mumol.kg-1.min-1, 2.6 +/- 0.2 mg.kg-1.min-1). Lactate and glucose rates of appearance were correlated (r = 0.58, P < 0.05) and decreased with fasting duration (r = 0.66, P < 0.02). The correction factor for carbon exchange in the tricarboxylic acid cycle was 1.14 +/- 0.11.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P F Bougnères
- Institut National de la Santé et de la Recherche Médicale Unité 342, Hôpital Saint Vincent de Paul, Paris, France
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12
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Landau BR. Noninvasive approaches to tracing pathways in carbohydrate metabolism. JPEN J Parenter Enteral Nutr 1991; 15:74S-77S. [PMID: 1865562 DOI: 10.1177/014860719101500374s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Compounds that can be given safely in large quantity, conjugate with intermediates of carbohydrate metabolism in liver, and are excreted, allow large amounts of those intermediates to be isolated noninvasively. By administering labeled compounds that form those intermediates and determining the amount and/or distribution of label in those intermediates, the metabolism of those compounds can be traced. Thus, glucuronide formation has been used to sample hepatic uridine diphosphate glucose (UDP-glucose) and study glycogen metabolism and the pentose pathway, phenylacetate to sample hepatic alpha-ketoglutarate and estimate relative flux through the Krebs cycle, and acetylation to sample hepatic acetyl CoA. Interpretations require knowledge of the anatomical sites of formation of the intermediates, since more than one pool of an intermediate can exist in liver. The extent the labeled compound is metabolized in extrahepatic tissues also must be taken into account.
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Affiliation(s)
- B R Landau
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
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Schumann WC, Magnusson I, Chandramouli V, Kumaran K, Wahren J, Landau BR. Metabolism of [2-14C]acetate and its use in assessing hepatic Krebs cycle activity and gluconeogenesis. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)89599-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Magnusson I, Chandramouli V, Schumann WC, Kumaran K, Wahren J, Landau BR. Pathways of hepatic glycogen formation in humans following ingestion of a glucose load in the fed state. Metabolism 1989; 38:583-5. [PMID: 2725297 DOI: 10.1016/0026-0495(89)90221-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The relative contributions of the direct and the indirect pathways to hepatic glycogen formation following a glucose load given to humans four hours after a substantial breakfast have been examined. Glucose loads labeled with [6-(14)C]glucose were given to six healthy volunteers along with diflunisal (1 g) or acetaminophen (1.5 g), drugs excreted in urine as glucuronides. Distribution of 14C in the glucose unit of the glucuronide was taken as a measure of the extent to which glucose was deposited directly in liver glycogen (ie, glucose----glucose-6-phosphate----glycogen) rather than indirectly (ie, glucose----C3-compound----glucose-6-phosphate----glycogen). The maximum contribution to glycogen formation by the direct pathway was estimated to be 77% +/- 4%, which is somewhat higher than previous estimates in humans fasted overnight (65% +/- 1%, P less than 0.05). Thus, the indirect pathway of liver glycogen formation following a glucose load is operative in both the overnight fasted and the fed state, although its contribution may be somewhat less in the fed state.
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Affiliation(s)
- I Magnusson
- Department of Clinical Physiology, Karolinska Institute, Huddinge Hospital, Sweden
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16
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Landau BR. Why the L-type pentose pathway does not function in liver. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1989; 21:99-102. [PMID: 2666185 DOI: 10.1016/0020-711x(89)90032-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. The classical pentose and not the L-type pathway functions in liver (Rognstad et al., 1982; Landau and Wood, 1983a; Landau, 1985; Scofield et al., 1985b). 2. It seems necessary to summarize again the reasons for this conclusion because of a recent review by Williams and his coworkers in this Journal (Williams et al., 1987).
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Affiliation(s)
- B R Landau
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106
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17
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Kosugi K, Chandramouli V, Kumaran K, Schumann WC, Landau BR. Determinants in the pathways followed by the carbons of acetone in their conversion to glucose. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)69287-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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18
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Kosugi K, Scofield RF, Chandramouli V, Kumaran K, Schumann WC, Landau BR. Pathways of acetone's metabolism in the rat. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35607-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Scofield RF, Kosugi K, Schumann WC, Kumaran K, Landau BR. Quantitative estimation of the pathways followed in the conversion to glycogen of glucose administered to the fasted rat. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39419-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Foster DM, Hetenyl G, Berman M. A model for carbon kinetics among plasma alanine, lactate, and glucose. THE AMERICAN JOURNAL OF PHYSIOLOGY 1980; 239:E30-8. [PMID: 7395987 DOI: 10.1152/ajpendo.1980.239.1.e30] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To account for the exchange of carbon atoms among alanine, lactate, and glucose in vivo, [2,3-3H]- and [U-14C]alanine or [3-3H]- and [U-14C]glucose were injected simultaneously to nonanesthetized normal dogs. The concentrations in plasma of 14C-labeled alanine, lactate, and glucose, and the injected 3H-labeled substrate were followed for 160 min after injection of the tracers. An integrated kinetic model describing the exchange of carbon atoms among substrates was developed from these data. The analysis suggests that there is a very rapid exchange of the carboxyl carbon of alanine with lactate in contrast to carbons 2 and 3. The model was used to calculate the fluxes of carbon atoms among the substrates in a steady state. In normal dogs plasma alanine and lactate contribute 14% of the carbon atoms released into the circulation as glucose.
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Abstract
The effect of prolonged (3-5 wk) fasting on tracer-determined glucose turnover and of recycling radioactive glucose has been examined. We followed the specific activity of plasma glucose after the simultaneous administration of 1-14C-glucose and 3-3H-glucose. The rate of glucose turnover decreased during prolonged fasting. Recycling of radioactive glucose was estimated by two different techniques: (1) the appearance of 14C in positions 2 to 6 glucose was measured; (2) the difference in the slopes of specific activity decline for 1-14C-glucose and for 3-3H-glucose was calculated. The two methods of estimating the radioactive recycling gave results similar to each other. The amount of glucose recycled did not change during prolonged fasting. However, in view of the decline in glucose production during fasting, the proportion of glucose production which was represented by recycling increased. Based on weight and urinary nitrogen loss an estimate of the glucose production from amino acids and glycerol was obtained. The difference between the rate of glucose production from the contribution of amino acids and glycerol and that estimated by radioisotopic techniques was much larger than the measured rate of recycling. This finding suggests that either a large exchange of 12C with 14C occurred in some glycolytic intermediates or that a hitherto unknown source of carbon for glucose production appeared during prolonged fasting.
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Freinkel N, Antony G, Williams HR, Landau BR. Metabolism of myo-inositol in rabbit kidney and in man. BIOCHIMICA ET BIOPHYSICA ACTA 1970; 201:425-33. [PMID: 5437656 DOI: 10.1016/0304-4165(70)90161-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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