1
|
Martino MR, Habibi M, Ferguson D, Brookheart RT, Thyfault JP, Meyer GA, Lantier L, Hughey CC, Finck BN. Disruption of hepatic mitochondrial pyruvate and amino acid metabolism impairs gluconeogenesis and endurance exercise capacity in mice. Am J Physiol Endocrinol Metab 2024; 326:E515-E527. [PMID: 38353639 DOI: 10.1152/ajpendo.00258.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 01/25/2024] [Accepted: 02/08/2024] [Indexed: 02/23/2024]
Abstract
Exercise robustly increases the glucose demands of skeletal muscle. This demand is met by not only muscle glycogenolysis but also accelerated liver glucose production from hepatic glycogenolysis and gluconeogenesis to fuel mechanical work and prevent hypoglycemia during exercise. Hepatic gluconeogenesis during exercise is dependent on highly coordinated responses within and between muscle and liver. Specifically, exercise increases the rate at which gluconeogenic precursors such as pyruvate/lactate or amino acids are delivered from muscle to the liver, extracted by the liver, and channeled into glucose. Herein, we examined the effects of interrupting hepatic gluconeogenic efficiency and capacity on exercise performance by deleting mitochondrial pyruvate carrier 2 (MPC2) and/or alanine transaminase 2 (ALT2) in the liver of mice. We found that deletion of MPC2 or ALT2 alone did not significantly affect time to exhaustion or postexercise glucose concentrations in treadmill exercise tests, but mice lacking both MPC2 and ALT2 in hepatocytes (double knockout, DKO) reached exhaustion faster and exhibited lower circulating glucose during and after exercise. Use of 2H/1³C metabolic flux analyses demonstrated that DKO mice exhibited lower endogenous glucose production owing to decreased glycogenolysis and gluconeogenesis at rest and during exercise. Decreased gluconeogenesis was accompanied by lower anaplerotic, cataplerotic, and TCA cycle fluxes. Collectively, these findings demonstrate that the transition of the liver to the gluconeogenic mode is critical for preventing hypoglycemia and sustaining performance during exercise. The results also illustrate the need for interorgan cross talk during exercise as described by the Cahill and Cori cycles.NEW & NOTEWORTHY Martino and colleagues examined the effects of inhibiting hepatic gluconeogenesis on exercise performance and systemic metabolism during treadmill exercise in mice. Combined inhibition of gluconeogenesis from lactate/pyruvate and alanine impaired exercise endurance and led to hypoglycemia during and after exercise. In contrast, suppressing either pyruvate-mediated or alanine-mediated gluconeogenesis alone had no effect on these parameters. These findings provide new insight into the molecular nodes that coordinate the metabolic responses of muscle and liver during exercise.
Collapse
Affiliation(s)
- Michael R Martino
- Division of Nutritional Sciences and Obesity Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Mohammad Habibi
- Division of Nutritional Sciences and Obesity Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Daniel Ferguson
- Division of Nutritional Sciences and Obesity Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Rita T Brookheart
- Division of Nutritional Sciences and Obesity Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
| | - John P Thyfault
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, Missouri, United States
| | - Gretchen A Meyer
- Department of Medicine, Program in Physical Therapy, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Louise Lantier
- Department of Molecular Physiology and Biophysics, Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Curtis C Hughey
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, United States
| | - Brian N Finck
- Division of Nutritional Sciences and Obesity Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States
| |
Collapse
|
2
|
Hughey CC, Bracy DP, Rome FI, Goelzer M, Donahue EP, Viollet B, Foretz M, Wasserman DH. Exercise training adaptations in liver glycogen and glycerolipids require hepatic AMP-activated protein kinase in mice. Am J Physiol Endocrinol Metab 2024; 326:E14-E28. [PMID: 37938177 DOI: 10.1152/ajpendo.00289.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/06/2023] [Accepted: 11/06/2023] [Indexed: 11/09/2023]
Abstract
Regular exercise elicits adaptations in glucose and lipid metabolism that allow the body to meet energy demands of subsequent exercise bouts more effectively and mitigate metabolic diseases including fatty liver. Energy discharged during the acute exercise bouts that comprise exercise training may be a catalyst for liver adaptations. During acute exercise, liver glycogenolysis and gluconeogenesis are accelerated to supply glucose to working muscle. Lower liver energy state imposed by gluconeogenesis and related pathways activates AMP-activated protein kinase (AMPK), which conserves ATP partly by promoting lipid oxidation. This study tested the hypothesis that AMPK is necessary for liver glucose and lipid adaptations to training. Liver-specific AMPKα1α2 knockout (AMPKα1α2fl/fl+AlbCre) mice and littermate controls (AMPKα1α2fl/fl) completed sedentary and exercise training protocols. Liver nutrient fluxes were quantified at rest or during acute exercise following training. Liver metabolites and molecular regulators of metabolism were assessed. Training increased liver glycogen in AMPKα1α2fl/fl mice, but not in AMPKα1α2fl/fl+AlbCre mice. The inability to increase glycogen led to lower glycogenolysis, glucose production, and circulating glucose during acute exercise in trained AMPKα1α2fl/fl+AlbCre mice. Deletion of AMPKα1α2 attenuated training-induced declines in liver diacylglycerides. In particular, training lowered the concentration of unsaturated and elongated fatty acids comprising diacylglycerides in AMPKα1α2fl/fl mice, but not in AMPKα1α2fl/fl+AlbCre mice. Training increased liver triacylglycerides and the desaturation and elongation of fatty acids in triacylglycerides of AMPKα1α2fl/fl+AlbCre mice. These lipid responses were independent of differences in tricarboxylic acid cycle fluxes. In conclusion, AMPK is required for liver training adaptations that are critical to glucose and lipid metabolism.NEW & NOTEWORTHY This study shows that the energy sensor and transducer, AMP-activated protein kinase (AMPK), is necessary for an exercise training-induced: 1) increase in liver glycogen that is necessary for accelerated glycogenolysis during exercise, 2) decrease in liver glycerolipids independent of tricarboxylic acid (TCA) cycle flux, and 3) decline in the desaturation and elongation of fatty acids comprising liver diacylglycerides. The mechanisms defined in these studies have implications for use of regular exercise or AMPK-activators in patients with fatty liver.
Collapse
Affiliation(s)
- Curtis C Hughey
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Deanna P Bracy
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
- Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, United States
| | - Ferrol I Rome
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, Minnesota, United States
| | - Mickael Goelzer
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - E Patrick Donahue
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Benoit Viollet
- Université Paris Cité, CNRS, Inserm, Institut Cochin, Paris, France
| | - Marc Foretz
- Université Paris Cité, CNRS, Inserm, Institut Cochin, Paris, France
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
- Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, United States
| |
Collapse
|
3
|
Schweitzer GG, Ditzenberger GL, Hughey CC, Finck BN, Martino MR, Pacak CA, Byrne BJ, Cade WT. Elevated liver glycogenolysis mediates higher blood glucose during acute exercise in Barth syndrome. PLoS One 2023; 18:e0290832. [PMID: 37651450 PMCID: PMC10470866 DOI: 10.1371/journal.pone.0290832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/17/2023] [Indexed: 09/02/2023] Open
Abstract
Barth syndrome (BTHS) is an X-linked recessive genetic disorder due to mutations in the Tafazzin (TAFAZZIN) gene that lead to cardiac and skeletal muscle mitochondrial dysfunction. Previous studies in humans with BTHS demonstrate that the defects in muscle mitochondrial oxidative metabolism result in an enhanced reliance on anaerobic metabolism during exercise to meet energy demands of muscular work. During exercise, the liver normally increases glucose production via glycogenolysis and gluconeogenesis to match the elevated rate of muscle glucose uptake and meet the ATP requirements of working muscle. However, the impact of Tafazzin deficiency on hepatic glucose production and the pathways contributing to hepatic glucose production during exercise is unknown. Therefore, the purpose of this study was to quantify in vivo liver gluconeogenesis and glycogenolysis in Tafazzin knockdown mice at rest and during acute exercise. METHODS Male TAFAZZIN shRNA transgenic (TG) and wild-type (WT) mice completed exhaustive treadmill running protocols to test exercise tolerance. Mice underwent 2H- and 13C-stable isotope infusions at rest and during a 30-minute treadmill running bout to quantify hepatic glucose production and associated nutrient fluxes under sedentary conditions and during acute exercise. Circulating and tissue (skeletal muscle and liver) samples were obtained during and following exercise to assess static metabolite levels. RESULTS TG mice reached exhaustion sooner during exhaustive treadmill running protocols and exhibited higher plasma lactate concentrations after exhaustive exercise compared to WT mice. Arterial glucose levels were comparable between genotypes at rest, but higher in TG mice compared to WT mice during exercise. Consistent with the higher blood glucose, TG mice showed increased endogenous glucose production owing to elevated glycogenolysis compared to WT mice during exercise. Total gluconeogenesis, gluconeogenesis from glycerol, gluconeogenesis from phosphoenolpyruvate, pyruvate cycling, total cataplerosis, and anaplerotic fluxes were similar between TG and WT mice at rest and during exercise. However, lactate dehydrogenase flux and TCA cycle fluxes trended higher in TG mice during exercise. Liver glycogen content in TG was higher in TG vs. controls. CONCLUSION Our data in the Tafazzin knockdown mouse suggest that elevated anaerobic metabolism during rest and exercise previously reported in humans with BTHS are supported by the finding of higher hepatic glycogenolysis.
Collapse
Affiliation(s)
- George G. Schweitzer
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Grace L. Ditzenberger
- Doctor of Physical Therapy Division, Duke University School of Medicine, Durham, NC, United States of America
| | - Curtis C. Hughey
- Department of Medicine, Division of Molecular Medicine, University of Minnesota, Minneapolis, MN, United States of America
| | - Brian N. Finck
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Michael R. Martino
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Christina A. Pacak
- Department of Neurology, University of Minnesota School of Medicine, Minneapolis, MN, United States of America
| | - Barry J. Byrne
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL, United States of America
| | - William Todd Cade
- Doctor of Physical Therapy Division, Duke University School of Medicine, Durham, NC, United States of America
- Program in Physical Therapy, Washington University School of Medicine, St. Louis, Missouri, United States of America
| |
Collapse
|
4
|
Martino MR, Habibi M, Ferguson D, Brookheart RT, Thyfault JP, Meyer GA, Lantier L, Hughey CC, Finck BN. Disruption of Hepatic Mitochondrial Pyruvate and Amino Acid Metabolism Impairs Gluconeogenesis and Endurance Exercise Capacity in Mice. bioRxiv 2023:2023.08.22.554345. [PMID: 37662392 PMCID: PMC10473655 DOI: 10.1101/2023.08.22.554345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Exercise robustly increases the glucose demands of skeletal muscle. This demand is met not only by muscle glycogenolysis, but also by accelerated liver glucose production from hepatic glycogenolysis and gluconeogenesis to fuel mechanical work and prevent hypoglycemia during exercise. Hepatic gluconeogenesis during exercise is dependent on highly coordinated responses within and between muscle and liver. Specifically, exercise increases the rate at which gluconeogenic precursors such as pyruvate/lactate or amino acids are delivered from muscle to the liver, extracted by the liver, and channeled into glucose. Herein, we examined the effects of interrupting gluconeogenic efficiency and capacity on exercise performance by deleting hepatic mitochondrial pyruvate carrier 2 (MPC2) and/or alanine transaminase 2 (ALT2) in mice. We found that deletion of MPC2 or ALT2 alone did not significantly affect time to exhaustion or post-exercise glucose concentrations in treadmill exercise tests, but mice lacking both MPC2 and ALT2 in liver (DKO) reached exhaustion faster and exhibited lower circulating glucose during and after exercise. Use of ²H/¹³C metabolic flux analyses demonstrated that DKO mice exhibited lower endogenous glucose production owing to decreased glycogenolysis and gluconeogenesis at rest and during exercise. The decreased gluconeogenesis was accompanied by lower anaplerotic, cataplerotic, and TCA cycle fluxes. Collectively, these findings demonstrate that the transition of the liver to the gluconeogenic mode is critical for preventing hypoglycemia and sustaining performance during exercise. The results also illustrate the need for interorgan crosstalk during exercise as described by the Cahill and Cori cycles.
Collapse
Affiliation(s)
- Michael R. Martino
- Department of Medicine, Division of Nutritional Sciences and Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Mohammad Habibi
- Department of Medicine, Division of Nutritional Sciences and Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Daniel Ferguson
- Department of Medicine, Division of Nutritional Sciences and Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Rita T. Brookheart
- Department of Medicine, Division of Nutritional Sciences and Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - John P. Thyfault
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, MO
| | - Gretchen A. Meyer
- Department of Medicine, Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO
| | - Louise Lantier
- Department of Molecular Physiology and Biophysics, Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine, Nashville, TN
| | - Curtis C. Hughey
- Department of Medicine, Division of Molecular Medicine, University of Minnesota, Minneapolis, MN
| | - Brian N. Finck
- Department of Medicine, Division of Nutritional Sciences and Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| |
Collapse
|