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Park S, Shim M, Lee G, You YA, Kim SM, Hur YM, Ko H, Park MH, Na SH, Kim YH, Cho GJ, Bae JG, Lee SJ, Lee SH, Lee DK, Kim YJ. Urinary metabolite biomarkers of pregnancy complications associated with maternal exposure to particulate matter. Reprod Toxicol 2024; 124:108550. [PMID: 38280687 DOI: 10.1016/j.reprotox.2024.108550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 01/02/2024] [Accepted: 01/23/2024] [Indexed: 01/29/2024]
Abstract
Particulate matter 2.5 (PM2.5) is associated with reproductive health and adverse pregnancy outcomes. However, studies evaluating biological markers of PM2.5 are lacking, and identifying biomarkers for estimating prenatal exposure to prevent pregnancy complications is essential. Therefore, we aimed to explore urine metabolites that are easy to measure as biomarkers of exposure. In this matched case-control study based on the PM2.5 exposure, 30 high PM2.5 group (>15 μg/m3) and 30 low PM2.5 group (<15 μg/m3) were selected from air pollution on pregnancy outcome (APPO) cohort study. We used a time-weighted average model to estimate individual PM exposure, which used indoor PM2.5 and outdoor PM2.5 concentrations by atmospheric measurement network based on residential addresses. Clinical characteristics and urine samples were collected from participants during the second trimester of pregnancy. Urine metabolites were quantitatively measured using gas chromatography-mass spectrometry following multistep chemical derivatization. Statistical analyses were conducted using SPSS version 21 and MetaboAnalyst 5.0. Small for gestational age and gestational diabetes (GDM) were significantly increased in the high PM2.5 group, respectively (P = 0.042, and 0.022). Fifteen metabolites showed significant differences between the two groups (P < 0.05). Subsequent pathway enrichment revealed that four pathways, including pentose and glucuronate interconversion with three pentose sugars (ribose, arabinose, and xylose; P < 0.05). The concentration of ribose increased preterm births (PTB) and GDM (P = 0.044 and 0.049, respectively), and the arabinose concentration showed a tendency to increase in PTB (P = 0.044). Therefore, we identified urinary pentose metabolites as biomarkers of PM2.5 and confirmed the possibility of their relationship with pregnancy complications.
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Affiliation(s)
- Sunwha Park
- Department of Obstetrics and Gynecology, College of Medicine, Ewha Medical Research Institute, Ewha Womans University, Seoul, Korea
| | - Minki Shim
- College of Pharmacy, Chung-Ang University, Seoul, Korea
| | - Gain Lee
- Graduate program in system health science and engineering, Ewha Womans University, Seoul, Korea
| | - Young-Ah You
- Department of Obstetrics and Gynecology, College of Medicine, Ewha Medical Research Institute, Ewha Womans University, Seoul, Korea
| | - Soo Min Kim
- Graduate program in system health science and engineering, Ewha Womans University, Seoul, Korea
| | - Young Min Hur
- Department of Obstetrics and Gynecology, College of Medicine, Ewha Medical Research Institute, Ewha Womans University, Seoul, Korea
| | - Hyejin Ko
- Department of Obstetrics and Gynecology, College of Medicine, Ewha Medical Research Institute, Ewha Womans University, Seoul, Korea
| | - Mi Hye Park
- Department of Obstetrics and Gynecology, Ewha Womans University Seoul Hospital, Korea
| | - Sung Hun Na
- Department of Obstetrics and Gynecology, Kangwon National University, School of Medicine, Korea
| | - Young-Han Kim
- Department of Obstetrics and Gynecology, Yonsei University College of Medicine, Korea
| | - Geum Joon Cho
- Department of Obstetrics and Gynecology, Korea University College of Medicine, Korea
| | - Jin-Gon Bae
- Department of Obstetrics and Gynecology, Keimyung University, School of Medicine, Dongsan Medical Center, Korea
| | - Soo-Jeong Lee
- Department of Obstetrics and Gynecology, University of Ulsan College of Medicine, Korea
| | | | - Dong-Kyu Lee
- College of Pharmacy, Chung-Ang University, Seoul, Korea.
| | - Young Ju Kim
- Department of Obstetrics and Gynecology, College of Medicine, Ewha Medical Research Institute, Ewha Womans University, Seoul, Korea; Graduate program in system health science and engineering, Ewha Womans University, Seoul, Korea.
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2
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Ziari N, Hellerstein M. Measurement of gluconeogenesis by 2H 2O labeling and mass isotopomer distribution analysis. J Biol Chem 2023; 299:105206. [PMID: 37660907 PMCID: PMC10539955 DOI: 10.1016/j.jbc.2023.105206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/21/2023] [Accepted: 08/23/2023] [Indexed: 09/05/2023] Open
Abstract
The gluconeogenesis pathway, which converts nonsugar molecules into glucose, is critical for maintaining glucose homeostasis. Techniques that measure flux through this pathway are invaluable for studying metabolic diseases such as diabetes that are associated with dysregulation of this pathway. We introduce a new method that measures fractional gluconeogenesis by heavy water labeling and gas chromatographic-mass spectrometric analysis. This technique circumvents cumbersome benchwork or inference of positionality from mass spectra. The enrichment and pattern of deuterium label on glucose is quantified by use of mass isotopomer distribution analysis, which informs on how much of glucose-6-phosphate-derived glucose comes from the gluconeogenesis (GNG) pathway. We use an in vivo model of the GNG pathway that is based on previously published models but offers a new approach to calculating GNG pathway and subpathway contributions using combinatorial probabilities. We demonstrated that this method accurately quantifies fractional GNG through experiments that perturb flux through the pathway and by probing analytical sensitivity. While this method was developed in mice, the results suggest that it is translatable to humans in a clinical setting.
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Affiliation(s)
- Naveed Ziari
- Department of Nutritional Sciences & Toxicology, University of California, Berkeley, California, USA
| | - Marc Hellerstein
- Department of Nutritional Sciences & Toxicology, University of California, Berkeley, California, USA.
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3
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Mei M, Liu D, Tang X, You Y, Peng B, He X, Huang J. Vitamin B6 Metabolic Pathway is Involved in the Pathogenesis of Liver Diseases via Multi-Omics Analysis. J Hepatocell Carcinoma 2022; 9:729-750. [PMID: 35979344 PMCID: PMC9377404 DOI: 10.2147/jhc.s370255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 08/04/2022] [Indexed: 11/23/2022] Open
Abstract
Purpose To clarify the underlying regulatory mechanisms of progression from liver cirrhosis to hepatocellular carcinoma (HCC), we analyzed the microbiomics, metabolomics, and proteomics in plasma and tissues from patients with HCC or decompensated liver cirrhosis (DC). Patients and Methods Tissues and plasma from 44 HCC patients and 28 patients with DC were collected for metabolomic analysis. 16S rRNA sequencing was performed in nine HCC tissues (HCCT), four distal noncancerous tissues (HCCN), and 11 DC tissues (DCT). Five HCC tissues had liver cirrhosis (HCCT-LC). Five hepatocellular carcinoma tissues without liver cirrhosis (HCCT-NLC) and five DCT were selected for proteomic sequencing. After combining proteomic and metabolomic analysis, we constructed a mouse model of chronic liver injury using carbon tetrachloride (CCl4) and treated them with vitamin B6 (VB6). Results 16s rRNA sequence results showed that HCC tissues had higher alpha diversity. The highest LDA scores were detected for Elizabethkingia in HCCT, Subsaxibacter in DCT, and Stenotrophomon in HCCN. Metabolomics results demonstrated some metabolites, including capric acid, L-threonate, choline, alpha-D-Glucose, D-ribose, betaine, 2E-eicosenoic acid, linoleic acid, L-palmitoylcarnitine, taurodeoxycholic acid, L-pyroglutamic acid, androsterone sulfate, and phthalic acid mono-2-ethylhexyl ester (MEHP), had better diagnostic efficacy than AFP (AUC: 0.852; 95% CI: 0.749, 0.954). In a combined analysis of metabolomics and proteomics, we found that HCCT-LC had more obvious disorders of VB6 metabolism and pentose and glucuronate interconversions than DCT, and kynurenine metabolism disorder was more significant in HCCT-LC than in HCCT-NLC. In the CCl4-induced chronic liver injury model, after VB6 supplementation, inflammatory cell infiltration, hepatocyte edema, and degeneration were significantly improved. Conclusion We found significant differences in the flora distribution between HCCT and DC; MEHP was a new diagnostic biomarker of HCC, and VB6 ameliorated the inflammatory cell infiltration, hepatocyte edema, and degeneration in chronic liver injury.
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Affiliation(s)
- Meihua Mei
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China.,Department of Laboratory Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Danping Liu
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China.,Department of Laboratory Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Xiuxin Tang
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China.,Department of Laboratory Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Ying You
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China.,Department of Laboratory Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Baogang Peng
- Hepatobiliary Surgery, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
| | - Xiaoshun He
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China
| | - Junqi Huang
- Organ Transplant Center, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation & Transplant Immunology, Guangzhou, 510080, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science & Technology (Organ Transplantation), Guangzhou, 510080, People's Republic of China.,Department of Laboratory Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, People's Republic of China
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4
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Jin ES, Lee MH, Malloy CR. 13 C NMR of glutamate for monitoring the pentose phosphate pathway in myocardium. NMR IN BIOMEDICINE 2021; 34:e4533. [PMID: 33900680 DOI: 10.1002/nbm.4533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/05/2021] [Accepted: 04/13/2021] [Indexed: 06/12/2023]
Abstract
After administration of 13 C-labeled glucose, the activity of the pentose phosphate pathway (PPP) is often assessed by the distribution of 13 C in lactate. However, in some tissues, such as the well-oxygenated heart, the concentration of lactate may be too low for convenient analysis by NMR. Here, we examined 13 C-labeled glutamate as an alternative biomarker of the PPP in the heart. Isolated rat hearts were perfused with media containing [2,3-13 C2 ]glucose and the tissue extracts were analyzed. Metabolism of [2,3-13 C2 ]glucose yields [1,2-13 C2 ]pyruvate via glycolysis and [2,3-13 C2 ]pyruvate via the PPP. Pyruvate is in exchange with lactate or is further metabolized to glutamate through pyruvate dehydrogenase and the TCA cycle. A doublet from [4,5-13 C2 ]glutamate, indicating flux through the PPP, was readily detected in 13 C NMR of heart extracts even when the corresponding doublet from [2,3-13 C2 ]lactate was minimal. Benfotiamine, known to induce the PPP, caused an increase in production of [4,5-13 C2 ]glutamate. In rats receiving [2,3-13 C2 ]glucose, brain extracts showed well-resolved signals from both [2,3-13 C2 ]lactate and [4,5-13 C2 ]glutamate in 13 C NMR spectra. Assessment of the PPP in the brain based on glutamate had a strong linear correlation with lactate-based assessment. In summary, 13 C NMR analysis of glutamate enabled detection of the low PPP activity in isolated hearts. This analyte is an alternative to lactate for monitoring the PPP with the use of [2,3-13 C2 ]glucose.
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Affiliation(s)
- Eunsook S Jin
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Min H Lee
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- VA North Texas Health Care System, Dallas, Texas, USA
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5
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Barosa C, Shanmugam H, Cabral F, Jones JG. p-Aminobenzoic acid as an alternative chemical biopsy agent for human hepatic UDP-glucose. Anal Biochem 2019; 590:113511. [PMID: 31759975 DOI: 10.1016/j.ab.2019.113511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 10/29/2019] [Accepted: 11/20/2019] [Indexed: 11/30/2022]
Abstract
p-Aminobenzoic acid (PABA) was evaluated for noninvasive sampling of UDP-glucose in the liver. Six healthy subjects ingested 550 mg PABA during a breakfast meal. Urine was collected 0-2 and 2-4 h after PABA ingestion. N-acetyl PABA glucuronide (NAPG) was identified with 522 ± 212 μmol recovered in the 2-4 h urines. One of the subjects ingested 2 g of 98% [U-2H7]glucose alongside PABA and the NAPG was analyzed for positional 2H-enrichment by 2H NMR following derivatization to 5-O-acetyl monoacetone glucuronolactone. In conclusion, PABA is an effective agent for the chemical biopsy of hepatic UDP-glucose in humans.
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Affiliation(s)
- Cristina Barosa
- CNC - Center for Neurosciences and Cell Biology, UC-Biotech, University of Coimbra, Portugal
| | - Harshitha Shanmugam
- CNC - Center for Neurosciences and Cell Biology, UC-Biotech, University of Coimbra, Portugal; UNIBA- University Aldo Moro of Bari, Bari, Italy
| | - Fernando Cabral
- CNC - Center for Neurosciences and Cell Biology, UC-Biotech, University of Coimbra, Portugal
| | - John G Jones
- CNC - Center for Neurosciences and Cell Biology, UC-Biotech, University of Coimbra, Portugal; APDP-Portuguese Diabetes Association, Lisbon, Portugal.
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6
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Lee MH, Malloy CR, Corbin IR, Li J, Jin ES. Assessing the pentose phosphate pathway using [2, 3- 13 C 2 ]glucose. NMR IN BIOMEDICINE 2019; 32:e4096. [PMID: 30924572 PMCID: PMC6525052 DOI: 10.1002/nbm.4096] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/27/2019] [Accepted: 02/28/2019] [Indexed: 05/24/2023]
Abstract
The pentose phosphate pathway (PPP) is essential for reductive biosynthesis, antioxidant processes and nucleotide production. Common tracers such as [1,2-13 C2 ]glucose rely on detection of 13 C in lactate and require assumptions to correct natural 13 C abundance. Here, we introduce a novel and specific tracer of the PPP, [2,3-13 C2 ]glucose. 13 C NMR analysis of the resulting isotopomers is informative because [1,2-13 C2 ]lactate arises from glycolysis and [2,3-13 C2 ]lactate arises exclusively through the PPP. A correction for natural abundance is unnecessary. In rats receiving [2,3-13 C2 ]glucose, the PPP was more active in the fed versus fasted state in the liver and the heart, consistent with increased expression of key enzymes in the PPP. Both the PPP and glycolysis were substantially increased in hepatoma compared with liver. In summary, [2,3-13 C2 ]glucose and 13 C NMR simplify assessment of the PPP.
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Affiliation(s)
- Min Hee Lee
- Department of Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Craig R. Malloy
- Department of Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- VA North Texas Health Care System, Dallas, TX 75216
| | - Ian R. Corbin
- Department of Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Junjie Li
- Department of Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Eunsook S. Jin
- Department of Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390
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7
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Turck D, Bresson JL, Burlingame B, Dean T, Fairweather-Tait S, Heinonen M, Hirsch-Ernst KI, Mangelsdorf I, McArdle H, Naska A, Neuhäuser-Berthold M, Nowicka G, Pentieva K, Sanz Y, Siani A, Sjödin A, Stern M, Tomé D, Vinceti M, Willatts P, Engel KH, Marchelli R, Pöting A, Poulsen M, Schlatter JR, Germini A, Van Loveren H. Safety of d-ribose as a novel food pursuant to Regulation (EU) 2015/2283. EFSA J 2018; 16:e05265. [PMID: 32625902 PMCID: PMC7009719 DOI: 10.2903/j.efsa.2018.5265] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on D-ribose as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The applicant intends to market the NF as ingredient in a variety of foods, food supplements and in certain foods for specific groups. The NF is produced by fermentation using a transketolase-deficient strain of Bacillus subtilis and marketed as Bioenergy Ribose™. The information provided on the batch-to-batch variability, specifications, stability, production process and history of the organism used as a source of the NF is sufficient and does not raise safety concerns. The Panel considers that the effects observed in a subchronic toxicity study in rats could be the consequence of nutritional imbalances, but toxicological effects could not be ruled out; from this study, the Panel derived a No observed adverse effect level (NOAEL) of 3.6 g/kg body weight (bw) per day. From the human studies indicating a potential decrease in glucose levels and/or the occurrence of transient symptomatic hypoglycaemia at intakes of 10 g of d-ribose, the Panel defined 70 mg/kg bw per day as the NOAEL with respect to hypoglycaemia that can be considered applicable for adults. For children, the Panel acknowledges the lack of human data directly relevant for this population group. Based on the NOAEL derived from the subchronic toxicity study in rats, an acceptable level of intake of 36 mg/kg bw per day was defined that would also take into account the potentially increased sensitivity of certain population groups to hypoglycaemia. The Panel concludes that the NF is safe for the general population at intake levels up to 36 mg/kg bw per day and considers that the safety of the NF at the intended uses and use levels as proposed by the applicant has not been established.
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8
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Jin ES, Sherry AD, Malloy CR. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver. J Biol Chem 2016; 291:19031-41. [PMID: 27432878 DOI: 10.1074/jbc.m116.742262] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Indexed: 11/06/2022] Open
Abstract
Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver.
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Affiliation(s)
- Eunsook S Jin
- From the Advanced Imaging Research Center and the Departments of Internal Medicine and
| | - A Dean Sherry
- From the Advanced Imaging Research Center and Radiology, University of Texas Southwestern Medical Center at Dallas, 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 the Departments of Internal Medicine and Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, the VA North Texas Health Care System, Dallas, Texas 75216
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9
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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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10
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Marin-Valencia I, Cho SK, Rakheja D, Hatanpaa KJ, Kapur P, Mashimo T, Jindal A, Vemireddy V, Good LB, Raisanen J, Sun X, Mickey B, Choi C, Takahashi M, Togao O, Pascual JM, DeBerardinis RJ, Maher EA, Malloy CR, Bachoo RM. Glucose metabolism via the pentose phosphate pathway, glycolysis and Krebs cycle in an orthotopic mouse model of human brain tumors. NMR IN BIOMEDICINE 2012; 25:1177-86. [PMID: 22383401 PMCID: PMC3670098 DOI: 10.1002/nbm.2787] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 12/29/2011] [Accepted: 01/03/2012] [Indexed: 05/05/2023]
Abstract
It has been hypothesized that increased flux through the pentose phosphate pathway (PPP) is required to support the metabolic demands of rapid malignant cell growth. Using orthotopic mouse models of human glioblastoma (GBM) and renal cell carcinoma metastatic to brain, we estimated the activity of the PPP relative to glycolysis by infusing [1,2-(13) C(2) ]glucose. The [3-(13) C]lactate/[2,3-(13) C(2) ]lactate ratio was similar for both the GBM and brain metastasis and their respective surrounding brains (GBM, 0.197 ± 0.011 and 0.195 ± 0.033, respectively (p = 1); metastasis: 0.126 and 0.119 ± 0.033, respectively). This suggests that the rate of glycolysis is significantly greater than the PPP flux in these tumors, and that the PPP flux into the lactate pool is similar in both tumors. Remarkably, (13) C-(13) C coupling was observed in molecules derived from Krebs cycle intermediates in both tumor types, denoting glucose oxidation. In the renal cell carcinoma, in contrast with GBM, (13) C multiplets of γ-aminobutyric acid (GABA) differed from its precursor glutamate, suggesting that GABA did not derive from a common glutamate precursor pool. In addition, the orthotopic renal tumor, the patient's primary renal mass and brain metastasis were all strongly immunopositive for the 67-kDa isoform of glutamate decarboxylase, as were 84% of tumors on a renal cell carcinoma tissue microarray of the same histology, suggesting that GABA synthesis is cell autonomous in at least a subset of renal cell carcinomas. Taken together, these data demonstrate that (13) C-labeled glucose can be used in orthotopic mouse models to study tumor metabolism in vivo and to ascertain new metabolic targets for cancer diagnosis and therapy.
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Affiliation(s)
- Isaac Marin-Valencia
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Division of Pediatric Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Steve K. Cho
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Dinesh Rakheja
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Kimmo J. Hatanpaa
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Payal Kapur
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Tomoyuki Mashimo
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Ashish Jindal
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Vamsidhara Vemireddy
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Levi B. Good
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Jack Raisanen
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Xiankai Sun
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Bruce Mickey
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Neurological Surgery, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Changho Choi
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Masaya Takahashi
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Osamu Togao
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Juan M. Pascual
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Division of Pediatric Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Ralph J. DeBerardinis
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Elizabeth A. Maher
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Craig R. Malloy
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Medical Service, Veterans Affairs North Texas Healthcare System, Lancaster, Texas 75216
- Corresponding authors: Robert M. Bachoo, MD, PhD, Department of Neurology, Annette G. Strauss Center for Neuro-Onoclogy, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75235, ; Craig Malloy, M.D., Mary Nell and Ralph B. Rogers Magnetic Resonance Center, 5323 Harry Hines Blvd., Dallas,TX 75390-8568.,
| | - Robert M. Bachoo
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Annette G. Strauss Center for Neuro-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
- Corresponding authors: Robert M. Bachoo, MD, PhD, Department of Neurology, Annette G. Strauss Center for Neuro-Onoclogy, UT Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75235, ; Craig Malloy, M.D., Mary Nell and Ralph B. Rogers Magnetic Resonance Center, 5323 Harry Hines Blvd., Dallas,TX 75390-8568.,
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11
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Delgado TC, Silva C, Fernandes I, Caldeira M, Bastos M, Baptista C, Carvalheiro M, Geraldes CFGC, Jones JG. Sources of hepatic glycogen synthesis during an oral glucose tolerance test: Effect of transaldolase exchange on flux estimates. Magn Reson Med 2010; 62:1120-8. [PMID: 19780152 DOI: 10.1002/mrm.22107] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Sources of hepatic glycogen synthesis during an oral glucose tolerance test were evaluated in six healthy subjects by enrichment of a 75-g glucose load with 6.67% [U-(13)C]glucose and 3.33% [U-(2)H(7)]glucose and analysis of plasma glucose and hepatic uridine diphosphate-glucose enrichments (sampled as urinary menthol glucuronide) by (2)H and (13)C nuclear magnetic resonance. The direct pathway contribution, as estimated from the dilution of [U-(13)C]glucose between plasma glucose and glucuronide, was unexpectedly low (36 +/- 5%). With [U-(2)H(7)]glucose, direct pathway estimates based on the dilution of position 3 (2)H-enrichment between plasma glucose and glucuronide were significantly higher (51 +/- 6%, P = 0.05). These differences reflect the exchange of the carbon 4, 5, and 6 moiety of fructose-6-phosphate and glyceraldehyde-3-phosphate catalyzed by transaldolase. As further evidence of this exchange, (2)H-enrichments in glucuronide positions 4 and 5 were inferior to those of position 3. From the difference in glucuronide positions 5 and 3 enrichments, the fraction of direct pathway carbons that experienced transaldolase exchange was estimated at 21 +/- 4%. In conclusion, the direct pathway contributes only half of hepatic glycogen synthesis during an oral glucose tolerance test. Glucose tracers labeled in positions 4, 5, or 6 will give significant underestimates of direct pathway activity because of transaldolase exchange.
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Affiliation(s)
- Teresa C Delgado
- NMR Laboratory, Center for Neurosciences and Cell Biology, Coimbra University, Coimbra, Portugal
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12
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Jones JG, Garcia P, Barosa C, Delgado TC, Diogo L. Hepatic anaplerotic outflow fluxes are redirected from gluconeogenesis to lactate synthesis in patients with Type 1a glycogen storage disease. Metab Eng 2009; 11:155-62. [PMID: 19558966 DOI: 10.1016/j.ymben.2009.01.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 09/23/2008] [Accepted: 01/26/2009] [Indexed: 11/25/2022]
Abstract
Hepatic glucose production and relative Krebs cycle fluxes (indexed to a citrate synthase flux of 1.0) were evaluated with [U-(13)C]glycerol tracer in 5 fed healthy controls and 5 Type 1a glycogen storage disease (GSD1a) patients. Plasma glucose, hepatic glucose-6-phosphate (G6P) and glutamine (13)C-isotopomers were analyzed by (13)C NMR via blood sampling and chemical biopsy. In healthy subjects, 35+/-14% of plasma glucose originated from hepatic G6P while GSD1a patients had no detectable G6P contribution. Compared to controls, GSD1a patients had an increased fraction of acetyl-CoA from pyruvate (0.5+/-0.2 vs. 0.3+/-0.1, p<0.01), and increased pyruvate recycling fluxes (14.4+/-3.8 vs. 8.7+/-2.8, p<0.05). Despite negligible gluconeogenic flux, net anaplerotic outflow was not significantly different from controls (2.2+/-0.8 vs. 1.3+/-0.5). The enrichment of lactate with (13)C-isotopomers derived from the Krebs cycle suggests that lactate was the main anaplerotic product in GSD1a patients.
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Affiliation(s)
- John G Jones
- NMR Research Unit, Department of Biochemistry and Center for Neurosciences and Cell Biology, Faculty of Sciences and Technology, University of Coimbra, 3001-401 Coimbra, Portugal.
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13
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Cedersund G, Strålfors P. Putting the pieces together in diabetes research: towards a hierarchical model of whole-body glucose homeostasis. Eur J Pharm Sci 2008; 36:91-104. [PMID: 19056492 DOI: 10.1016/j.ejps.2008.10.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 10/22/2008] [Indexed: 12/13/2022]
Abstract
Type 2 diabetes is one of the most widespread and rapidly spreading diseases world-wide and has been subject of extensive research efforts. However, understanding the molecular basis of the disease is increasing piecemeal and a consensus regarding the overall picture of normal metabolic regulation and malfunction in diabetes has not emerged. A systems biology approach, combining mathematical modelling with simultaneous high-throughput measurements, can be of considerable help. On the whole-body level, this has been done in pharmacokinetic and pharmacodynamic models, which recently have started to mature into more physiologically realistic organ-based models. At the other end of the spectrum, detailed models for crucial cellular processes are starting to mature into complete modules that potentially can be fitted into such whole-body organ-based models. The result of such a merge is a multi-level hierarchical model, which is a model type that has been common in technical systems. In this review, we report and exemplify some of the recent progress that has been made to achieve such a hierarchical model, and we argue why it is only through such a model that a complete picture of diabetes mellitus can be obtained.
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Affiliation(s)
- Gunnar Cedersund
- Department of Clinical and Experimental Medicine, Cell Biology and Diabetes Research Centre, Linköping University, Linköping, Sweden.
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14
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Jones JG, Garcia P, Barosa C, Delgado TC, Caldeira MM, Diogo L. Quantification of hepatic transaldolase exchange activity and its effects on tracer measurements of indirect pathway flux in humans. Magn Reson Med 2008; 59:423-9. [DOI: 10.1002/mrm.21451] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Staehr P, Hother-Nielsen O, Beck-Nielsen H, Roden M, Stingl H, Holst JJ, Jones PK, Chandramouli V, Landau BR. Hepatic autoregulation: response of glucose production and gluconeogenesis to increased glycogenolysis. Am J Physiol Endocrinol Metab 2007; 292:E1265-9. [PMID: 17213474 DOI: 10.1152/ajpendo.00411.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of increased glycogenolysis, simulated by galactose's conversion to glucose, on the contribution of gluconeogenesis (GNG) to hepatic glucose production (GP) was determined. The conversion of galactose to glucose is by the same pathway as glycogen's conversion to glucose, i.e., glucose 1-phosphate --> glucose 6-phosphate --> glucose. Healthy men (n = 7) were fasted for 44 h. At 40 h, hepatic glycogen stores were depleted. GNG then contributed approximately 90% to a GP of approximately 8 micromol.kg(-1).min(-1). Galactose, 9 g/h, was infused over the next 4 h. The contribution of GNG to GP declined from approximately 90% to 65%, i.e., by approximately 2 micromol.kg(-1).min(-1). The rate of galactose conversion to blood glucose, measured by labeling the infused galactose with [1-(2)H]galactose (n = 4), was also approximately 2 micromol.kg(-1).min(-1). The 41st h GP rose by approximately 1.5 micromol.kg(-1).min(-1) and then returned to approximately 9 micromol.kg(-1).min(-1), while plasma glucose concentration increased from approximately 4.5 to 5.3 mM, accompanied by a rise in plasma insulin concentration. Over 50% of the galactose infused was accounted for in blood glucose and hepatic glycogen formation. Thus an increase in the rate of GP via the glycogenolytic pathway resulted in a concomitant decrease in the rate of GP via GNG. While the compensatory response to the galactose administration was not complete, since GP increased, hepatic autoregulation is operative in healthy humans during prolonged fasting.
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Affiliation(s)
- Peter Staehr
- Medical Endocrinological Department, Odense University Hospital, Odense, Denmark
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16
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Mendes AC, Caldeira MM, Silva C, Burgess SC, Merritt ME, Gomes F, Barosa C, Delgado TC, Franco F, Monteiro P, Providencia L, Jones JG. Hepatic UDP-glucose 13C isotopomers from [U-13C]glucose: a simple analysis by 13C NMR of urinary menthol glucuronide. Magn Reson Med 2007; 56:1121-5. [PMID: 17036288 DOI: 10.1002/mrm.21057] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Menthol glucuronide was isolated from the urine of a healthy 70-kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U-(13)C]glucose. Glucuronide (13)C-excess enrichment levels were 4-6% and thus provided high signal-to-noise ratios (SNRs) for confident assignment of (13)C-(13)C spin-coupled multiplet components within each (13)C resonance by (13)C NMR. The [U-(13)C]glucuronide isotopomer derived via direct pathway conversion of [U-(13)C]glucose to [U-(13)C]UDP-glucose was resolved from [1,2,3-(13)C(3)]- and [1,2-(13)C(2)]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U-(13)C]glucose. In a second study, a group of four overnight-fasted patients (63 +/- 10 kg) with severe heart failure were given peppermint oil and infused with [U-(13)C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady-state plasma [U-(13)C]glucose enrichment of 4.6% +/- 0.6%. Menthol glucuronide was harvested and glucuronide (13)C-isotopomers were analyzed by (13)C NMR. [U-(13)C]glucuronide enrichment was 0.6% +/- 0.1%, and the sum of [1,2,3-(13)C(3)] and [1,2-(13)C(2)]glucuronide enrichments was 0.9% +/- 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% +/- 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% +/- 10% of GP.
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Affiliation(s)
- Ana C Mendes
- Department of Chemistry, University of Coimbra, Coimbra, Portugal
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17
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Stingl H, Chandramouli V, Schumann WC, Brehm A, Nowotny P, Waldhäusl W, Landau BR, Roden M. Changes in hepatic glycogen cycling during a glucose load in healthy humans. Diabetologia 2006; 49:360-8. [PMID: 16380802 DOI: 10.1007/s00125-005-0099-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Accepted: 09/19/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS Glycogen cycling, i.e. simultaneous glycogen synthesis and glycogenolysis, affects estimates of glucose fluxes using tracer techniques and may contribute to hyperglycaemia in diabetic conditions. This study presents a new method for quantifying hepatic glycogen cycling in the fed state. Glycogen is synthesised from glucose by the direct and indirect (gluconeogenic) pathways. Since glycogen is also synthesised from glycogen, i.e. glycogen-->glucose 1-phosphate-->glycogen, that synthesised through the direct and indirect pathways does not account for 100% of glycogen synthesis. The percentage contribution of glycogen cycling to glycogen synthesis then equals the difference between the sum of the percentage contributions of the direct and indirect pathways and 100. MATERIALS AND METHODS The indirect and direct pathways were measured independently in nine healthy volunteers who had fasted overnight. They ingested (2)H(2)O (5 ml/kg body water) and were infused with [5-(3)H]glucose and acetaminophen (paracetamol; 1 g) during hyperglycaemic clamps (7.8 mmol/l) lasting 8 h. The percentage contribution of the indirect pathway was calculated from the ratio of (2)H enrichments at carbon 5 to that at carbon 2, and the contribution of the direct pathway was determined from the (3)H-specific activity, relative to plasma glucose, of the urinary glucuronide excreted between 2 and 4, 4 and 6, and 6 and 8 h. RESULTS Glucose infusion rates increased (p<0.01) to approximately 50 mumol kg(-1) min(-1). Plasma insulin and the insulin : glucagon ratio rose approximately 3.6- and approximately 8.3-fold (p<0.001), respectively. From the difference between 100% and the sum of the direct (2-4 h, 54+/-6%; 4-6 h, 59+/-5%; 6-8 h, 63+/-4%) and indirect (32+/-3, 38+/-4, 36+/-3%) pathways, glycogen cycling was seen to be decreased (p<0.05) from 14+/-4% (2-4 h) to 4+/-3% (4-6 h) and 1+/-3% (6-8 h). CONCLUSIONS/INTERPRETATION This method allows measurement of hepatic glycogen cycling in the fed state and demonstrates that glycogen cycling occurs most in the early hours after glucose loading subsequent to a fast.
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Affiliation(s)
- H Stingl
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
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18
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Kishore AI, Mayer MR, Prestegard JH. Partial 13C isotopic enrichment of nucleoside monophosphates: useful reporters for NMR structural studies. Nucleic Acids Res 2005; 33:e164. [PMID: 16254075 PMCID: PMC1270954 DOI: 10.1093/nar/gni165] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Analysis of the 13C isotopic labeling patterns of nucleoside monophosphates (NMPs) extracted from Escherichia coli grown in a mixture of C-1 and C-2 glucose is presented. By comparing our results to previous observations on amino acids grown in similar media, we have been able to rationalize the labeling pattern based on the well-known biochemistry of nucleotide biosynthesis. Except for a few notable absences of label (C4 in purines and C3′ in ribose) and one highly enriched site (C1′ in ribose), most carbons are randomly enriched at a low level (an average of 13%). These sparsely labeled NMPs give less complex NMR spectra than their fully isotopically labeled analogs due to the elimination of most 13C–13C scalar couplings. The spectral simplicity is particularly advantageous when working in ordered systems, as illustrated with guanosine diphosphate (GDP) bound to ADP ribosylation factor 1 (ARF1) aligned in a liquid crystalline medium. In this system, the absence of scalar couplings and additional long-range dipolar couplings significantly enhances signal to noise and resolution.
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Affiliation(s)
| | | | - James H. Prestegard
- To whom correspondence should be addressed. Tel: +1 706 542 6281; Fax: +1 706 542 4412;
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19
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Jones JG, Solomon MA, Cole SM, Sherry AD, Malloy CR. An integrated (2)H and (13)C NMR study of gluconeogenesis and TCA cycle flux in humans. Am J Physiol Endocrinol Metab 2001; 281:E848-56. [PMID: 11551863 DOI: 10.1152/ajpendo.2001.281.4.e848] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hepatic glucose synthesis from glycogen, glycerol, and the tricarboxylic acid (TCA) cycle was measured in five overnight-fasted subjects by (1)H, (2)H, and (13)C NMR analysis of blood glucose, urinary acetaminophen glucuronide, and urinary phenylacetylglutamine after administration of [1,6-(13)C(2)]glucose, (2)H(2)O, and [U-(13)C(3)]propionate. This combination of tracers allows three separate elements of hepatic glucose production (GP) to be probed simultaneously in a single study: 1) endogenous GP, 2) the contribution of glycogen, phosphoenolpyruvate (PEP), and glycerol to GP, and 3) flux through PEP carboxykinase, pyruvate recycling, and the TCA cycle. Isotope-dilution measurements of [1,6-(13)C(2)] glucose by (1)H and (13)C NMR indicated that GP in 16-h-fasted humans was 10.7 +/- 0.9 micromol.kg(-1).min(-1). (2)H NMR spectra of monoacetone glucose (derived from plasma glucose) provided the relative (2)H enrichment at glucose H-2, H-5, and H-6S, which, in turn, reflects the contribution of glycogen, PEP, and glycerol to total GP (5.5 +/- 0.7, 4.8 +/- 1.0, and 0.4 +/- 0.3 micromol.kg(-1).min(-1), respectively). Interestingly, (13)C NMR isotopomer analysis of phenylacetylglutamine and acetaminophen glucuronide reported different values for PEP carboxykinase flux (68.8 +/- 9.8 vs. 37.5 +/- 7.9 micromol.kg(-1).min(-1)), PEP recycling flux (59.1 +/- 9.8 vs. 27.8 +/- 6.8 micromol.kg(-1).min(-1)), and TCA cycle flux (10.9 +/- 1.4 vs. 5.4 +/- 1.4 micromol.kg(-1).min(-1)). These differences may reflect zonation of propionate metabolism in the liver.
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Affiliation(s)
- J G Jones
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas 75235, USA
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20
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Dirlewanger M, Schneiter P, Jéquier E, Tappy L. Effects of fructose on hepatic glucose metabolism in humans. Am J Physiol Endocrinol Metab 2000; 279:E907-11. [PMID: 11001775 DOI: 10.1152/ajpendo.2000.279.4.e907] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hepatic and extrahepatic insulin sensitivity was assessed in six healthy humans from the insulin infusion required to maintain an 8 mmol/l glucose concentration during hyperglycemic pancreatic clamp with or without infusion of 16.7 micromol. kg(-1). min(-1) fructose. Glucose rate of disappearance (GR(d)), net endogenous glucose production (NEGP), total glucose output (TGO), and glucose cycling (GC) were measured with [6,6-(2)H(2)]- and [2-(2)H(1)]glucose. Hepatic glycogen synthesis was estimated from uridine diphosphoglucose (UDPG) kinetics as assessed with [1-(13)C]galactose and acetaminophen. Fructose infusion increased insulin requirements 2.3-fold to maintain blood glucose. Fructose infusion doubled UDPG turnover, but there was no effect on TGO, GC, NEGP, or GR(d) under hyperglycemic pancreatic clamp protocol conditions. When insulin concentrations were matched during a second hyperglycemic pancreatic clamp protocol, fructose administration was associated with an 11.1 micromol. kg(-1). min(-1) increase in TGO, a 7.8 micromol. kg(-1). min(-1) increase in NEGP, a 2.2 micromol. kg(-1). min(-1) increase in GC, and a 7.2 micromol. kg(-1). min(-1) decrease in GR(d) (P < 0. 05). These results indicate that fructose infusion induces hepatic and extrahepatic insulin resistance in humans.
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Affiliation(s)
- M Dirlewanger
- Institute of Physiology, University of Lausanne Medical School, 1005 Lausanne, Switzerland
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21
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Paquot N, Schneiter P, Scheen AJ, Lefèbvre PJ, Tappy L. Assessment of postprandial hepatic glycogen synthesis from uridine diphosphoglucose kinetics in obese and lean non-diabetic subjects. Int J Obes (Lond) 2000; 24:1297-302. [PMID: 11093291 DOI: 10.1038/sj.ijo.0801386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Obese patients are frequently characterized by insulin resistance and decreased insulin-mediated glycogen synthesis in skeletal muscle. Whether they also have impaired postprandial hepatic glycogen synthesis remains unknown. AIM To determine whether postprandial hepatic glycogen synthesis is decreased in obese patients compared to lean subjects. METHODS Lean and obese subjects with impaired glucose tolerance were studied over 4h after ingestion of a glucose load. Hepatic uridine diphosphoglucose kinetics were assessed using 13C-galactose infusion, with monitoring of urinary acetaminophen-glucuronide isotopic enrichment to estimate hepatic glycogen kinetics. RESULTS Estimated net hepatic glycogen synthesis amounted to 18.6 and 22.6% of the ingested load in lean and obese subjects, respectively. CONCLUSION Postprandial hepatic glycogen metabolism is not impaired in non-diabetic obese subjects.
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Affiliation(s)
- N Paquot
- Department of Medicine, CHU Sart-Tilman, University of Liège, Belgium
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22
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Schneiter P, Gillet M, Chioléro R, Wauters JP, Berger M, Tappy L. Postprandial hepatic glycogen synthesis in liver transplant recipients. Transplantation 2000; 69:978-81. [PMID: 10755560 DOI: 10.1097/00007890-200003150-00052] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The liver plays a central role in glucose homeostasis by releasing glucose in the fasting state and by taking up and converting into glycogen part of the glucose absorbed from the gastrointestinal tract after meal ingestion. METHODS To determine whether the hepatic denervation that accompanies liver transplantation interferes with these functions, we assessed glucose tolerance to an oral glucose load in seven patients at 2-6 weeks after orthotopic liver transplantation, in six patients after kidney transplantation, and in six healthy controls. Hepatic glycogen synthesis was non-invasively assessed over the 4 hours after ingestion of a glucose load by monitoring hepatic uridine diphosphoglucose turnover with 13C galactose and acetaminophen. RESULTS Liver and kidney transplant recipients had increased postprandial glucose concentrations but normal hepatic uridine diphosphoglucose turnover, indicating an unaltered hepatic glycogen synthesis. CONCLUSIONS These results indicate that denervated liver transplants have an adequate glucoregulatory function. Postprandial hyperglycemia in liver transplant recipients is therefore not due to alterations of liver glucose metabolism.
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Affiliation(s)
- P Schneiter
- Institute of Physiology, University of Lausanne, Switzerland
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23
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Landau BR. Quantifying the contribution of gluconeogenesis to glucose production in fasted human subjects using stable isotopes. Proc Nutr Soc 1999; 58:963-72. [PMID: 10817164 DOI: 10.1017/s0029665199001275] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The contribution of gluconeogenesis to glucose production is estimated from the enrichment of the H bound to C-5 of glucose relative to either that bound to C-2 of glucose or the enrichment in body water on ingesting 2H2O in the fasted state. Contributions of all gluconeogenic substrates are included in the estimate and the limitation of an uncertain precursor enrichment removed. The half-life of 2H2O in body water precludes a repeat study for many weeks. Glycogen cycling could result in underestimation, but there is evidence that glycogen cycling does not occur in liver in the fasted state. Gluconeogenesis has been estimated by mass-isotopomer-distribution analyses, usually by administering 13C-labelled glycerol. Underestimates emphasize the major limitation of the method, i.e. the need to assume a single enrichment of the precursor pool. Estimates of gluconeogenesis from isotopomer distribution in arterial-blood glucose and lactate on infusing [U-13C6] glucose are unreliable, as a proportion of the glucose is formed from glycerol and from amino acids not converted to glucose via pyruvate. Loss of label in the Krebs cycle and relying on enrichment of arterial-blood lactate as a measure of hepatic pyruvate further add to the uncertainty. Estimates of the rate of gluconeogenesis by NMR are obtained by subtraction of the rate of glycogenolysis determined by NMR from the rate of glucose production. Estimates are then the mean rate for the period over which glycogen contents are measured. Technical considerations can limit the accuracy of analyses and result in overestimates.
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Affiliation(s)
- B R Landau
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4951, USA.
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Chandramouli V, Ekberg K, Schumann WC, Wahren J, Landau BR. Origins of the hydrogen bound to carbon 1 of glucose in fasting: significance in gluconeogenesis quantitation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E717-23. [PMID: 10516132 DOI: 10.1152/ajpendo.1999.277.4.e717] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Healthy subjects ingested (2)H(2)O. (2)H enriched the hydrogen bound to carbon 1 of blood glucose 1.3 to 1.8 times more than the hydrogens bound to carbon 6. Enrichment at carbon 1 was more than at carbon 5 after 14 h, but not after 42 h, of fasting. After overnight fasting, when [2,3-(3)H]succinate was infused, 34 times as much (3)H was bound to carbon 6 as to carbon 1. On [1-(2)H,1-(3)H, 1-(14)C]galactose infusion, the ratios of (2)H to (14)C and of (3)H to (14)C in blood glucose were 30% less than in the galactose. (3)H at carbon 6 was 1% of that at carbon 1 of the glucose. Thus, although the two hydrogens bound to carbon 1 and the two bound to carbon 6 of fructose 6-phosphate (p) during gluconeogenesis are equally enriched in (2)H via pyruvate's equilibration with alanine, one of each is further enriched via hydration of fumarate that is converted to glucose. That hydrogen at carbon 1 of fructose 6-phosphate (P) is also enriched in fructose 6-P's equilibration with mannose 6-P. (2)H from (2)H(2)O at carbon 1 to carbon 2 of blood glucose cannot then quantitate gluconeogenesis because of [1-(2)H]glucose formation during glycogenolysis. Triose-P cycling has a minimal effect on quantitation. (2)H recovery in glucose from [1-(2)H]galactose does not quantitate galactose conversion via UDP-glucose to glycogen.
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Affiliation(s)
- V Chandramouli
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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25
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Petersen KF, Krssak M, Navarro V, Chandramouli V, Hundal R, Schumann WC, Landau BR, Shulman GI. Contributions of net hepatic glycogenolysis and gluconeogenesis to glucose production in cirrhosis. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:E529-35. [PMID: 10070020 DOI: 10.1152/ajpendo.1999.276.3.e529] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Net hepatic glycogenolysis and gluconeogenesis were examined in normal (n = 4) and cirrhotic (n = 8) subjects using two independent methods [13C nuclear magnetic resonance spectroscopy (NMR) and a 2H2O method]. Rates of net hepatic glycogenolysis were calculated by the change in hepatic glycogen content before ( approximately 11:00 PM) and after ( approximately 7:00 AM) an overnight fast using 13C NMR and magnetic resonance imaging. Gluconeogenesis was calculated as the difference between the rates of glucose production determined with an infusion of [6,6-2H2]glucose and net hepatic glycogenolysis. In addition, the contribution of gluconeogenesis to glucose production was determined by the 2H enrichment in C-5/C-2 of blood glucose after intake of 2H2O (5 ml/kg body water). Plasma levels of total and free insulin-like growth factor I (IGF-I) and IGF-I binding proteins-1 and -3 were significantly decreased in the cirrhotic subjects (P < 0.01 vs. controls). Postprandial hepatic glycogen concentrations were 34% lower in the cirrhotic subjects (P = 0.007). Rates of glucose production were similar between the cirrhotic and healthy subjects [9.0 +/- 0.9 and 10.0 +/- 0.8 micromol. kg body wt-1. min-1, respectively]. Net hepatic glycogenolysis was 3.5-fold lower in the cirrhotic subjects (P = 0.01) and accounted for only 13 +/- 6% of glucose production compared with 40 +/- 10% (P = 0.03) in the control subjects. Gluconeogenesis was markedly increased in the cirrhotic subjects and accounted for 87 +/- 6% of glucose production vs. controls: 60 +/- 10% (P = 0.03). Gluconeogenesis in the cirrhotic subjects, as determined from the 2H enrichment in glucose C-5/C-2, was also increased and accounted for 68 +/- 3% of glucose production compared with 54 +/- 2% (P = 0.02) in the control subjects. In conclusion, cirrhotic subjects have increased rates of gluconeogenesis and decreased rates of net hepatic glycogenolysis compared with control subjects. These alterations are likely important contributing factors to their altered carbohydrate metabolism.
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Affiliation(s)
- K F Petersen
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Conneticut 06520-8020, USA.
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26
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Jones JG, Solomon MA, Sherry AD, Jeffrey FM, Malloy CR. 13C NMR measurements of human gluconeogenic fluxes after ingestion of [U-13C]propionate, phenylacetate, and acetaminophen. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:E843-52. [PMID: 9815005 DOI: 10.1152/ajpendo.1998.275.5.e843] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anaplerotic, pyruvate recycling, and gluconeogenic fluxes were measured by 13C isotopomer analysis of plasma glucose, urinary phenylacetylglutamine, and urinary glucuronide in normal, 24-h-fasted individuals after ingestion of [U-13C]propionate, phenylacetate, and acetaminophen. Plasma glucose isotopomer analysis reported a total anaplerotic flux of 5.92 +/- 1.03 (SD) relative to citrate synthase. This was not significantly different from glucuronide and phenylacetylglutamine analyses (6.08 +/- 1.16 and 7. 14 +/- 1.94, respectively). Estimates of pyruvate recycling from glucose and glucuronide isotopomer distributions were almost identical (3.55 +/- 0.99 and 3.66 +/- 1.11, respectively), whereas phenylacetylglutamine reported a significantly higher estimate (5.74 +/- 2.13). As a consequence, net gluconeogenic flux reported by phenylacetylglutamine (1.41 +/- 0.28) was significantly less than that reported by glucose (2.37 +/- 0.64) and glucuronide (2.42 +/- 0. 76). This difference in fluxes detected by analysis of phenylacetylglutamine vs. hexose is likely due to compartmentation of hepatic metabolism of propionate. Net gluconeogenic flux estimates made by use of this stable isotope method are in good agreement with recent measurements in humans with [14C]propionate.
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Affiliation(s)
- J G Jones
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas TX 75235, USA
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27
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Lee WN, Boros LG, Puigjaner J, Bassilian S, Lim S, Cascante M. Mass isotopomer study of the nonoxidative pathways of the pentose cycle with [1,2-13C2]glucose. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E843-51. [PMID: 9612242 DOI: 10.1152/ajpendo.1998.274.5.e843] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We present a single-tracer method for the study of the pentose phosphate pathway (PPP) using [1,2-13C2]glucose and mass isotopomer analysis. The metabolism of [1,2-13C2]glucose by the glucose-6-phosphate dehydrogenase, transketolase (TK), and transaldolase (TA) reactions results in unique pentose and lactate isotopomers with either one or two 13C substitutions. The distribution of these isotopomers was used to estimate parameters of the PPP using the model of Katz and Rognstad (J. Katz and R. Rognstad. Biochemistry 6: 2227-2247, 1967). Mass and position isotopomers of ribose, and lactate and palmitate (products from triose phosphate) from human hepatoma cells (Hep G2) incubated with 30% enriched [1,2-13C2]glucose were determined using gas chromatography-mass spectrometry. After 24-72 h incubation, 1.9% of lactate molecules in the medium contained one 13C substitution (m1) and 10% contained two 13C substitutions (m2). A similar m1-to-m2 ratio was found in palmitate as expected. Pentose cycle (PC) activity determined from incubation with [1,2-13C2]glucose was 5.73 +/- 0.52% of the glucose flux, which was identical to the value of PC (5.55 +/- 0.73%) determined by separate incubations with [1-13C] and [6-13C]glucose, 13C was found to be distributed in four ribose isotopomers ([1-13C]-, [5-13C]-, [1,2-13C2]-, and [4,5-13C2]ribose). The observed ribose isotopomer distribution was best matched with that provided from simulation by substituting 0.032 for TK and 0.85 for TA activity relative to glucose uptake into the model of Katz and Rognstad. The use of [1,2-13C2]glucose not only permits the determination of PC but also allows estimation of relative rates through the TK and TA reactions.
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Affiliation(s)
- W N Lee
- Department of Pediatrics, Harbor-University of California Los Angeles Medical Center, Torrance 90502, USA
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28
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Rother KI, Schwenk WF. Hepatic glycogen accurately reflected by acetaminophen glucuronide in dogs refed after fasting. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:E766-73. [PMID: 7485493 DOI: 10.1152/ajpendo.1995.269.4.e766] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To validate a method to "biochemically biopsy" the immediate precursor of intrahepatic glycogen [uridyl diphosphate (UDP)-glucose] using acetaminophen and to assess how fasting affects the direct and indirect pathways of glycogen synthesis, dogs were fasted overnight (group 1, n = 5) or for 2.5 days (group 2, n = 5) and then given a 4-h duodenal infusion of unlabeled glucose, [3-3H]glucose, and [U-14C]lactate to label hepatic glycogen via the direct and indirect pathways, respectively, and [1-13C]galactose to measure intrahepatic UDP-glucose flux. After 3 h for equilibration, acetaminophen was given and urine was collected for acetaminophen glucuronide. Multiple liver biopsies were obtained. The mean 3H/14C ratios of glucose derived from glycogen (10.4 +/- 4.1 and 1.1 +/- 0.3 for groups 1 and 2, respectively) and glucose derived from acetaminophen glucuronide (11.5 +/- 4.0 and 1.0 +/- 0.1 for groups 1 and 2, respectively) were similar. Fasting significantly increased UDP-glucose flux, the rate of glycogen synthesis, and the contribution of the indirect pathway. We conclude that, in dogs, 1) no functional hepatic zonation exists with regard to acetaminophen glucuronidation and liver glycogen synthesis and 2) with appropriate choice of isotopic tracers and study design, UDP-glucose flux can accurately reflect rates of hepatic glycogen synthesis.
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Affiliation(s)
- K I Rother
- Department of Pediatrics, Mayo Clinic, Rochester, Minnesota 55905, USA
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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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30
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Landau BR, Fernandez CA, Previs SF, Ekberg K, Chandramouli V, Wahren J, Kalhan SC, Brunengraber H. A limitation in the use of mass isotopomer distributions to measure gluconeogenesis in fasting humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:E18-26. [PMID: 7631774 DOI: 10.1152/ajpendo.1995.269.1.e18] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The use of distributions of mass isotopomers in glucose from [U-13C]glycerol to estimate fractional rates of gluconeogenesis was examined. [U-13C]glycerol was infused into normal subjects who ingested acetaminophen and fasted for 60 h. Isotopomer distributions were measured by mass spectrometry in blood glucose and in glucuronic acid from urinary acetaminophen glucuronide. The distributions are incompatible with glucose production solely via gluconeogenesis from a single pool of triose phosphates. Rather, with the assumption of a single enriched triose phosphate pool, the distributions indicate, despite the 60 h of fasting, about as much glucose formation from an unlabeled glucose source as from that pool. Therefore the data indicate cellular heterogeneity in glycerol's metabolism, so that two or more pools with significantly different enrichments were the source of the glucose and glucuronic acid. This heterogeneity is related to much greater concentrations of glycerol in periportal than in pericentral zones of the liver lobule. Beyond evidence for heterogeneity, the findings emphasize a limitation in applying analyses of mass isotopomer distributions to measure polymer biosynthesis in the presence of heterogeneity in the precursor pool.
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Affiliation(s)
- B R Landau
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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31
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Bonadonna RC, del Prato S, Bonora E, Gulli G, Solini A, DeFronzo RA. Effects of physiological hyperinsulinemia on the intracellular metabolic partition of plasma glucose. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:E943-53. [PMID: 8279550 DOI: 10.1152/ajpendo.1993.265.6.e943] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Methodology for assessing the glycolytic and oxidative fluxes from plasma glucose, by measuring 3H2O and 14CO2 rates of production during [3-3H]- and [U-14C]glucose infusion, was tested in healthy subjects. In study 1, during staircase 3H2O infusion in six subjects, calculated rates of 3H2O appearance agreed closely with 3H2O infusion rates. In study 2, when [2-3H]glucose and NaH14CO3 were infused in four subjects in the basal state and during a 4-h euglycemic insulin (approximately 70 microU/ml) clamp, accurate estimates of the rates of [2-3H]glucose detritiation were obtained (94-97% of the expected values), and the recovery factor of NaH14CO3 did not change during hyperinsulinemia. In study 3, 11 subjects underwent a 4-h euglycemic insulin (approximately 70 microU/ml) clamp with [3-3H]- and [U-14C]glucose infusion and measurement of gaseous exchanges by indirect calorimetry to estimate the rates of total glycolysis, glycogen synthesis, glucose oxidation, nonoxidative glycolysis, hepatic glucose production, glucose recycling, and glucose conversion to fat. Hyperinsulinemia stimulated glycogen synthesis above baseline more than glycolysis [increment of 4.78 +/- 0.37 vs. 2.0 +/- 0.17 mg.min-1 x kg-1 of lean body mass (LBM), respectively, P < 0.01] and incompletely suppressed (approximately 87%) hepatic glucose production. The major component of nonoxidative glycolysis shifted from glucose recycling in the postabsorptive state (approximately 57% of nonoxidative glycolysis) to glucose conversion to fat during hyperinsulinemia (approximately 59% of nonoxidative glycolysis). Lipid oxidation during the insulin clamp was negatively correlated with both isotopic glucose oxidation (r = -0.822, P < 0.002) and glycolysis (r = -0.582, P < 0.07). In conclusion, in healthy subjects, glycogen synthesis plays a greater role than glycolysis and glucose oxidation in determining insulin-mediated glucose disposal. Part of insulin-mediated increase in glycolysis/oxidation might be secondary to the relief of the competition between fat and glucose for oxidation.
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Affiliation(s)
- R C Bonadonna
- Metabolism Unit, Consiglio Nazionale delle Ricerche Institute of Clinical Physiology, Pisa, Italy
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Flanigan I, Collins JG, Arora KK, MacLeod JK, Williams JF. Exchange reactions catalyzed by group-transferring enzymes oppose the quantitation and the unravelling of the identify of the pentose pathway. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 213:477-85. [PMID: 8477719 DOI: 10.1111/j.1432-1033.1993.tb17784.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
1. The distributions and rates of transfer of carbon isotopes from a selection of specifically labelled ketosugar-phosphate substrates by exchange reactions catalyzed by the pentose and photosynthetic carbon-reduction-pathway group-transferring enzymes transketolase, transaldolase and aldolase have been measured using 13C-NMR spectroscopy. 2. The rates of these exchange reactions were 5, 4 and 1.5 mumol min-1 mg-1 for transketolase exchange, transaldolase exchange and aldolase exchange, respectively. 3. A comparison of the exchange capacities contributed by the activities of these enzymes in three in vitro liver preparations with the maximum non-oxidative pentose pathway flux rates of the preparations shows that transketolase and aldolase exchanges exceeded flux by 9-19 times in liver cytosol and acetone powder enzyme preparations and by 5 times in hepatocytes. Transaldolase was less effective in the comparison of exchange versus flux rates: transaldolase exchange exceeded flux by 1.6 and 5 in catalysis by liver cytosol and acetone powder preparations, respectively, but was only 0.6 times the flux in hepatocytes. 4. Values of group enzyme exchange and pathway flux rates in the above three preparations are important because of the feature role of liver and of these particular preparations in the establishment, elucidation and measurement of a proposed reaction scheme for the fat-cell-type pentose pathway in biochemistry. 5. It is the claim of this paper that the excess of exchange rate activity (particularly transketolase exchange) over pathway flux will overturn attempts to unravel, using isotopically labelled sugar substrates, the identity, reaction sequence and quantitative contribution of the pentose pathway to glucose metabolism. 6. The transketolase exchange reactions relative to the pentose pathway flux rates in normal, regenerating and foetal liver, Morris hepatomas, mammary carcinoma, melanoma, colonic epithelium, spinach chloroplasts and epididymal fat tissue show that transketolase exchange may exceed flux in these tissues by factors ranging over 5-600 times. 7. The confusion of pentose pathway theory by the effects of transketolase exchange action is illustrated by the 13C-NMR spectrum of the hexose 6-phosphate products of ribose 5-phosphate dissimilation, formed after 30 min of liver enzyme action, and shows 13C-labelling in carbons 1 and 3 of glucose 6-phosphate with ratios which range over 2.1-6.4 rather than the mandatory value of 2 which is imposed by the theoretical mechanism of the pathway.
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Affiliation(s)
- I Flanigan
- Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra
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33
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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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Larrabee MG. Evaluation of the pentose phosphate pathway from 14CO2 data. Fallibility of a classic equation when applied to non-homogeneous tissues. Biochem J 1990; 272:127-32. [PMID: 2124803 PMCID: PMC1149666 DOI: 10.1042/bj2720127] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A classic equation that has frequently been used to estimate the fraction of glucose metabolized by the pentose phosphate pathway, using 14CO2 data, is more simply re-derived with careful consideration of the assumptions involved and the conditions under which it is applicable. The equation is shown to be unreliable for non-homogeneous tissues, depending on the fraction of triose phosphate converted to CO2. The formula in question is as follows: ([1]CO2/G-[6]CO2/G)/(1-[6]CO2/G) = 3Fmet./(1 + 2Fmet.) where [1]CO2 and [6]CO2 are output rates of carbons 1 and 6 of glucose respectively to CO2, G is the rate of glucose uptake and Fmet. is the fraction of the glucose that is metabolized to CO2 and triose phosphate by the pentose phosphate pathway, allowing for recycling of an appropriate fraction of the fructose-6-phosphate produced by the pathway. This analysis illustrates the importance of suitably testing any equation that assumes homogeneity before application to non-homogeneous tissues.
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Affiliation(s)
- M G Larrabee
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218
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