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Di Ciaula A, Calamita G, Shanmugam H, Khalil M, Bonfrate L, Wang DQH, Baffy G, Portincasa P. Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests. Int J Mol Sci 2021; 22:7702. [PMID: 34299321 PMCID: PMC8305940 DOI: 10.3390/ijms22147702] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/08/2021] [Accepted: 07/14/2021] [Indexed: 02/07/2023] Open
Abstract
The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD.
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Affiliation(s)
- Agostino Di Ciaula
- Clinica Medica “A. Murri”, Department of Biomedical Sciences & Human Oncology, University of Bari Medical School, 70124 Bari, Italy; (A.D.C.); (H.S.); (M.K.); (L.B.)
| | - Giuseppe Calamita
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari “Aldo Moro”, 70100 Bari, Italy;
| | - Harshitha Shanmugam
- Clinica Medica “A. Murri”, Department of Biomedical Sciences & Human Oncology, University of Bari Medical School, 70124 Bari, Italy; (A.D.C.); (H.S.); (M.K.); (L.B.)
| | - Mohamad Khalil
- Clinica Medica “A. Murri”, Department of Biomedical Sciences & Human Oncology, University of Bari Medical School, 70124 Bari, Italy; (A.D.C.); (H.S.); (M.K.); (L.B.)
| | - Leonilde Bonfrate
- Clinica Medica “A. Murri”, Department of Biomedical Sciences & Human Oncology, University of Bari Medical School, 70124 Bari, Italy; (A.D.C.); (H.S.); (M.K.); (L.B.)
| | - David Q.-H. Wang
- Marion Bessin Liver Research Center, Einstein-Mount Sinai Diabetes Research Center, Department of Medicine and Genetics, Division of Gastroenterology and Liver Diseases, Albert Einstein College of Medicine, Bronx, NY 10461, USA;
| | - Gyorgy Baffy
- Department of Medicine, VA Boston Healthcare System and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02130, USA;
| | - Piero Portincasa
- Clinica Medica “A. Murri”, Department of Biomedical Sciences & Human Oncology, University of Bari Medical School, 70124 Bari, Italy; (A.D.C.); (H.S.); (M.K.); (L.B.)
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Exploring Liver Mitochondrial Function by 13C-Stable Isotope Breath Tests: Implications in Clinical Biochemistry. Methods Mol Biol 2021; 2310:179-199. [PMID: 34096004 DOI: 10.1007/978-1-0716-1433-4_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The liver is at the crossroad of key metabolic processes, which include detoxification, glycolipidic storage and export, and protein synthesis. The gut-liver axis, moreover, provides hepatocytes with a series of bacterial products and metabolites, which contribute to maintain liver function in health and disease. Breath tests (BTs) are developed as diagnostic tools for indirect, rapid, noninvasive assessment of several metabolic processes in the liver. BTs monitor the appearance of CO2 in breath as a marker of a specific substrate metabolized in the liver, typically within microsomes, cytosol, or mitochondria. The noninvasiveness of BTs originates from the use of the, nonradioactive, naturally occurring stable isotope 13C marking a specific substrate which is metabolized in the liver, leading to the appearance of 13CO2 in expired air. Some substrates (ketoisocaproic acid, methionine, and octanoic acid) provide information about dynamic liver mitochondrial function in health and disease. In humans, the application of 13C-breath tests ranges from nonalcoholic and alcoholic liver diseases to liver cirrhosis, hepatocarcinoma, preoperative and postoperative assessment of liver function, and drug-induced liver damage. 13C-BTs are an indirect, cost-effective, and easy method to evaluate dynamic liver function and gastric kinetics in health and disease, with ongoing studies focusing on further applications in clinical medicine.
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Afolabi PR, Scorletti E, Calder PC, Byrne CD. Factors independently associated with cardiorespiratory fitness in patients with non-alcoholic fatty liver disease. Liver Int 2020; 40:2998-3007. [PMID: 32706931 DOI: 10.1111/liv.14618] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 07/16/2020] [Accepted: 07/17/2020] [Indexed: 02/13/2023]
Abstract
UNLABELLED Low cardiorespiratory fitness (CRF) is associated with non-alcoholic fatty liver disease (NAFLD) and low CRF is an important risk factor for cardiovascular disease. The factors that influence CRF in NAFLD are poorly understood and it has been suggested that reduced hepatic mitochondrial function (HMF) may be linked to low CRF. Therefore, our aim was to determine the factors associated with CRF in NAFLD. METHODS Ninety-seven patients with NAFLD were studied. CRF was assessed by treadmill testing and expressed as maximal O2 consumption (VO2 peak) per lean body mass. HMF was assessed by the 13 C-ketoisocaproate breath test. Multivariable linear regression modelling was undertaken to test the independence of associations with CRF. RESULTS Mean (SD) age was 51 (13) years and 61% were men. With CRF as the outcome, age (B coefficient -0.3, 95%CI -0.4, -0.2, P < .0001), total body fat mass (B coefficient -0.2, 95%CI -0.3, -0.05, P = .01), type 2 diabetes mellitus (T2DM) (B coefficient -3.6, 95%CI -1.1, -6.1, P = .005), smoking status (B coefficient -5.7, 95%CI -1.9, -9.5, P = .004), serum γ-glutamyl transferase (GGT) (B coefficient -0.04, 95%CI -0.05, -0.02, P < .0001), HMF (B coefficient -0.5, 95%CI -0.8, -0.1, P = .01) and diastolic function (B coefficient 0.1, 95%CI 0.05, 0.13, P < .0001) were independently associated with CRF. This model explained 60% of the total variance in CRF (R2 = 0.6, P < .0001); and this model with GGT alone explained 24% of the variance in CRF. CONCLUSIONS In patients with NAFLD, HMF is independently associated with CRF and a model with GGT alone explained most of the variance in CRF.
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Affiliation(s)
- Paul R Afolabi
- National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Eleonora Scorletti
- National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK.,Department of Gastroenterology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Philip C Calder
- National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Christopher D Byrne
- National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK.,School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
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Afolabi PR, Scorletti E, Calder PC, Byrne CD. The evaluation of the repeatability of the 13C-ketoisocaproate breath test for assessing hepatic mitochondrial function. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2019; 55:150-160. [PMID: 30880467 DOI: 10.1080/10256016.2019.1588265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/22/2019] [Indexed: 06/09/2023]
Abstract
The 13C-ketoisocaproate (13C-KICA) breath test (BT) has been recently proposed as a non-invasive test for assessing hepatic mitochondrial function. Results of the 13C-KICA BT can be expressed as different parameters. However, the best parameter for expressing the 13C-KICA BT result is uncertain which hinders use of the BT in routine clinical practice. We have investigated the repeatability of different parameters of 13C-KICA BT. Thirteen healthy adult subjects (5 men and 8 women) underwent a 13C-KICA BT on two occasions separated by a gap of approximately 30 days. There were no significant differences between the repeated measurements for all the test parameters over 30 days. Furthermore, the Bland Altman statistics showed no fixed or proportional bias for any of the test parameters. The cumulative 13C-dose enrichment over 60 min had the lowest within-subject variability of 12% compared to all other test parameters. The cumulative 13C-dose enrichment over 60 min could be a very useful parameter for the 13C-KICA BT to detect impaired hepatic mitochondrial function in patients with chronic liver diseases.
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Affiliation(s)
- Paul R Afolabi
- a National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust , Southampton , UK
- b Human Development and Health, Faculty of Medicine , University of Southampton , Southampton , UK
| | - Eleonora Scorletti
- a National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust , Southampton , UK
- b Human Development and Health, Faculty of Medicine , University of Southampton , Southampton , UK
- c Department of Gastroenterology, Perelman School of Medicine , University of Pennsylvania , Philadelphia , PA , USA
| | - Philip C Calder
- a National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust , Southampton , UK
- b Human Development and Health, Faculty of Medicine , University of Southampton , Southampton , UK
| | - Christopher D Byrne
- a National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust , Southampton , UK
- b Human Development and Health, Faculty of Medicine , University of Southampton , Southampton , UK
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Afolabi PR, Scorletti E, Smith DE, Almehmadi AA, Calder PC, Byrne CD. The characterisation of hepatic mitochondrial function in patients with non-alcoholic fatty liver disease (NAFLD) using the 13C-ketoisocaproate breath test. J Breath Res 2018; 12:046002. [PMID: 29943733 DOI: 10.1088/1752-7163/aacf12] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hepatic mitochondrial function (HMF) assessed by the 13C-ketoisocaproate breath test (13C-KICA BT) has been previously shown to be significantly associated with the severity of biopsy proven non-alcoholic fatty liver disease (NAFLD). However, it is uncertain whether any perturbation in HMF relates specifically to severity of liver disease or factors associated with metabolic syndrome within (NAFLD). Our aim was to investigate whether there was any change in HMF assessed by 13C-KICA BT in patients with NAFLD compared to control subjects, and to assess the factors that are independently associated with HMF. METHODS 77 patients with NAFLD and 11 healthy control subjects were studied. HMF was assessed using 13C-KICA BT and expressed as cumulative % 13C-dose recovered on breath over 1 h (cPDR over 1 h). Liver fat and fibrosis was assessed by transient elastography. Multivariable linear regression modelling was undertaken to test the independence of associations with HMF. RESULTS HMF (cPDR over 1 h) was lower in NAFLD compared to controls [13.4% (4.8) v. 21.0% (6.3); p < 0.0001)]. In NAFLD, HMF was lower in patients with diabetes versus no diabetes [12.7% (3.4) v. 14.3% (6.1); p = 0.003)]. Regression modelling showed age (β = -0.08; p = 0.01), waist circumference (β = -0.08; p = 0.01), hip circumference (β = -0.04; p = 0.01), aspartate aminotransferase (AST) (β = -0.05; p = 0.01) and diabetes status (β = -1.81; p = 0.01) were independently associated with HMF (R2 = 41.5%; p < 0.0001). CONCLUSIONS In patients with NAFLD (compared to healthy subjects), there was a reduction in HMF assessed by the 13C-KICA BT. Furthermore, in patients with NAFLD, HMF is independent and inversely associated with age, waist and hip circumference, AST and diabetes status.
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Affiliation(s)
- Paul R Afolabi
- National Institute for Health Research, Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom. Human Development and Health Academic Unit, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
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Exploring liver mitochondrial function by ¹³C-stable isotope breath tests: implications in clinical biochemistry. Methods Mol Biol 2015; 1241:137-52. [PMID: 25308494 DOI: 10.1007/978-1-4939-1875-1_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The liver plays a pivotal role in a myriad of metabolic processes, including detoxification, glycolipidic storage and export, and protein synthesis. Breath tests employing (13)C as stable isotope have been introduced to explore such energy-dependent pathways involving mitochondrial function in the liver. Specific substrates are ketoisocaproic acid, methionine, and octanoic acid. In humans, the application of (13)C-breath tests ranges from nonalcoholic and alcoholic liver diseases to liver cirrhosis, hepatocarcinoma, preoperative and postoperative assessment of liver function, and drug-induced liver damage. Studying liver mitochondrial function by (13)C-breath tests represents a complementary tool to monitor complex metabolic processes in health and disease.
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Dänicke S, Diers S. Effects of ergot alkaloids in feed on performance and liver function of piglets as evaluated by the13C-methacetin breath test. Arch Anim Nutr 2013; 67:15-36. [DOI: 10.1080/1745039x.2012.736279] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Dänicke S, Diers S. Effects of ergot alkaloids on liver function of piglets as evaluated by the (13)C-methacetin and (13)C-α-ketoisocaproic acid breath test. Toxins (Basel) 2013; 5:139-61. [PMID: 23322130 PMCID: PMC3564074 DOI: 10.3390/toxins5010139] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 12/12/2012] [Accepted: 12/20/2012] [Indexed: 11/29/2022] Open
Abstract
Ergot alkaloids (the sum of individual ergot alkaloids are termed as total alkaloids, TA) are produced by the fungus Claviceps purpurea, which infests cereal grains commonly used as feedstuffs. Ergot alkaloids potentially modulate microsomal and mitochondrial hepatic enzymes. Thus, the aim of the present experiment was to assess their effects on microsomal and mitochondrial liver function using the 13C-Methacetin (MC) and 13C-α-ketoisocaproic acid (KICA) breath test, respectively. Two ergot batches were mixed into piglet diets, resulting in 11 and 22 mg (Ergot 5-low and Ergot 5-high), 9 and 14 mg TA/kg (Ergot 15-low and Ergot 15-high) and compared to an ergot-free control group. Feed intake and live weight gain decreased significantly with the TA content (p < 0.001). Feeding the Ergot 5-high diet tended to decrease the 60-min-cumulative 13CO2 percentage of the dose recovery (cPDR60) by 26% and 28% in the MC and KICA breath test, respectively, compared to the control group (p = 0.065). Therefore, both microsomal and mitochondrial liver function was slightly affected by ergot alkaloids.
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Affiliation(s)
- Sven Dänicke
- Institute of Animal Nutrition, Friedrich-Loeffler-Institute, Federal Research Institute for Animal Health, Braunschweig D-38116, Germany.
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Dänicke S, Diers S. Effects of ergot alkaloids on liver function of piglets can be detected by the [(13)C]methacetin breath test irrespective of oral or intramuscular route of tracer administration. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2012; 48:558-572. [PMID: 22612381 DOI: 10.1080/10256016.2012.688825] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ergot alkaloids (sum=total alkaloids, TA) originate from the phyto-pathogenic fungus Claviceps purpurea and might exert feed intake depressing and hepatotoxic effects on animals. The aim of the study was to evaluate TA effects on performance and liver function of piglets with the [(13)C]methacetin breath test and two routes of tracer administration (orally, p.o.; intramuscularly, i.m.). Two ergot batches were mixed into piglet diets resulting in 21 and 17 mg TA kg(-1) (Ergot-5 and -12, respectively) and compared with an ergot-free control diet. Feed intake was significantly depressed after feeding the ergot containing diets (p=<0.001). The time at maximum (13)CO(2) exhalation (t (max)) and the half-life (t (0.5)) were not influenced by treatments and varied between 25 and 68 min after the p.o., and 28 and 62 min after the i.m. administration of [(13)C]methacetin, respectively. The cumulative (13)C recovery (cPDR(30)) was significantly lower due to feeding the diet Ergot-5 (6.6 %) compared with the Ergot-12 (8.8 %) and the control diet (9.7 %) irrespective of the route of tracer administration (p=0.044). As a discrimination of the diet effects through both tracer administration routes is possible, the i.m. application should be preferred in piglets as this causes less stress than the oral forced administration.
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Affiliation(s)
- Sven Dänicke
- Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Braunschweig, Germany.
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Wilk A, Seichter F, Kim SS, Tütüncü E, Mizaikoff B, Vogt JA, Wachter U, Radermacher P. Toward the quantification of the 13CO2/12CO2 ratio in exhaled mouse breath with mid-infrared hollow waveguide gas sensors. Anal Bioanal Chem 2011; 402:397-404. [DOI: 10.1007/s00216-011-5524-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 10/13/2011] [Accepted: 10/19/2011] [Indexed: 11/28/2022]
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Bandsma RHJ, Mendel M, Spoelstra MN, Reijngoud DJ, Boer T, Stellaard F, Brabin B, Schellekens R, Senga E, Heikens GT. Mechanisms behind decreased endogenous glucose production in malnourished children. Pediatr Res 2010; 68:423-8. [PMID: 20657348 DOI: 10.1203/pdr.0b013e3181f2b959] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Severe malnutrition is a major health problem in developing countries and can present itself as kwashiorkor or marasmus. Although marasmus is characterized by clinical wasting, kwashiorkor is associated with peripheral edema, oxidative stress, hypoalbuminemia, and hypoglycemia. The etiology of the hypoglycemia is poorly understood. We determined endogenous glucose production (EGP) in children with severe malnutrition. Children with kwashiorkor, marasmus, and controls received a primed constant infusion of [6,6H2]glucose for 2 h. An i.v. bolus of 13C-ketoisocaproic acid (KIC) was given, and breath samples were obtained during 2 h. Isotope dilution was used to calculate EGP, and 13CO2/12CO2 production was determined. Mean EGP ± SEM was 5.5 ± 0.3 mg/kg/min in the kwashiorkor group and 6.9 ± 0.4 mg/kg/min and 7.6 ± 0.7 mg/kg/min in the marasmic and control group, respectively, (p < 0.05 kwashiorkor versus marasmus and controls). EGP correlated with serum albumin concentration (r = 0.67; p < 0.001) and urinary 8-hydroxydeoxyguanosine as a marker of oxidative stress (r = -0.62; p < 0.005). 13CO2 secretion as a marker of hepatic mitochondrial function was significantly higher in the marasmic group compared with kwashiorkor and controls. We conclude that decreased EGP in severely malnourished children is related to the degree of hypoalbuminemia and oxidative stress but is not associated with a clear defect in hepatic mitochondrial function.
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Grattagliano I, Lauterburg BH, Palasciano G, Portincasa P. 13C-breath tests for clinical investigation of liver mitochondrial function. Eur J Clin Invest 2010; 40:843-50. [PMID: 20597965 DOI: 10.1111/j.1365-2362.2010.02331.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Mitochondria play a major role in cell energetic metabolism; therefore, mitochondrial dysfunction inevitably participates in or even determines the onset and progression of chronic liver diseases. The assessment of mitochondrial function in vivo, by providing more insight into the pathogenesis of liver diseases, would be a helpful tool to study specific hepatic functions and to develop rational diagnostic, prognostic and therapeutic strategies. DESIGN This review focuses on the utility of breath tests to assess mitochondrial function in humans and experimental animals. RESULTS The introduction in the clinical setting of specific breath tests may allow elegantly and noninvasively overcoming the difficulties caused by previous complex techniques and might provide clinically relevant information, i.e the effects of drugs on mitochondria. Substrates meeting this requirement are alpha-keto-isocaproic acid and methionine that are both decarboxylated by mitochondria. Long-and medium-chain fatty acids that are metabolized through the Krebs cycle, and benzoic acid which undergoes glycine conjugation, may also reflect the function of mitochondria. CONCLUSIONS Breath tests to assess in vivo mitochondrial function in humans represent a potentially useful diagnostic and prognostic tool in clinical investigation.
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Affiliation(s)
- Ignazio Grattagliano
- Clinica Medica "A. Murri", Department of Internal Medicine, University of Bari Medical School, Bari, Italy
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