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Zhang Z, Emami S, Hennebelle M, Morgan RK, Lerno LA, Slupsky CM, Lein PJ, Taha AY. Linoleic acid-derived 13-hydroxyoctadecadienoic acid is absorbed and incorporated into rat tissues. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1866:158870. [PMID: 33340768 DOI: 10.1016/j.bbalip.2020.158870] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 10/22/2020] [Accepted: 12/14/2020] [Indexed: 12/22/2022]
Abstract
Linoleic acid (LNA)-derived 13-hydroxyoctadecadienoic acid (13-HODE) is a bioactive lipid mediator that regulates multiple signaling processes in vivo. 13-HODE is also produced when LNA is oxidized during food processing. However, the absorption and incorporation kinetics of dietary 13-HODE into tissues is not known. The present study measured unesterified d4-13-HODE plasma bioavailability and incorporation into rat liver, adipose, heart and brain following gavage or intravenous (IV) injection (n = 3 per group). Mass spectrometry analysis revealed that d4-13-HODE was absorbed within 20 min of gavage, and continued to incorporate into plasma esterified lipid fractions throughout the 90 min monitoring period (incorporation half-life of 71 min). Following IV injection, unesterified d4-13-HODE was rapidly eliminated from plasma with a half-life of 1 min. Analysis of tracer incorporation kinetics into rat tissues following IV injection or gavage revealed that the esterified tracer preferentially incorporated into liver, adipose and heart compared to unesterified d4-13-HODE. No tracer was detected in the brain. This study demonstrates that dietary 13-HODE is absorbed, and incorporated into peripheral tissues from esterified plasma lipid pools. Understanding the chronic effects of dietary 13-HODE exposure on peripheral tissue physiology and metabolism merits future investigation.
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Affiliation(s)
- Zhichao Zhang
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA
| | - Shiva Emami
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA
| | - Marie Hennebelle
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA
| | - Rhianna K Morgan
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Larry A Lerno
- Food Safety and Measurement Facility, University of California, Davis, CA, USA
| | - Carolyn M Slupsky
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA; Department of Nutrition, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Ameer Y Taha
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA.
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Otoki Y, Metherel AH, Pedersen T, Yang J, Hammock BD, Bazinet RP, Newman JW, Taha AY. Acute Hypercapnia/Ischemia Alters the Esterification of Arachidonic Acid and Docosahexaenoic Acid Epoxide Metabolites in Rat Brain Neutral Lipids. Lipids 2020; 55:7-22. [PMID: 31691988 PMCID: PMC7220815 DOI: 10.1002/lipd.12197] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 12/15/2022]
Abstract
In the brain, approximately 90% of oxylipins are esterified to lipids. However, the significance of this esterification process is not known. In the present study, we (1) validated an aminopropyl solid phase extraction (SPE) method for separating esterified lipids using 100 and 500 mg columns and (2) applied the method to quantify the distribution of esterified oxylipins within phospholipids (PL) and neutral lipids (NL) (i.e. triacylglycerol and cholesteryl ester) in rats subjected to head-focused microwave fixation (controls) or CO2 -induced hypercapnia/ischemia. We hypothesized that oxylipin esterification into these lipid pools will be altered following CO2 -induced hypercapnia/ischemia. Lipids were extracted from control (n = 8) and CO2 -asphyxiated (n = 8) rat brains and separated on aminopropyl cartridges to yield PL and NL. The separated lipid fractions were hydrolyzed, purified with hydrophobic-lipophilic-balanced SPE columns, and analyzed with ultra-high-pressure liquid chromatography coupled to tandem mass spectrometry. Method validation showed that the 500 mg (vs 100 mg) aminopropyl columns yielded acceptable separation and recovery of esterified fatty acid epoxides but not other oxylipins. Two epoxides of arachidonic acid (ARA) were significantly increased, and three epoxides of docosahexaenoic acid (DHA) were significantly decreased in brain NL of CO2 -asphyxiated rats compared to controls subjected to head-focused microwave fixation. PL-bound fatty acid epoxides were highly variable and did not differ significantly between the groups. This study demonstrates that hypercapnia/ischemia alters the concentration of ARA and DHA epoxides within NL, reflecting an active turnover process regulating brain fatty acid epoxide concentrations.
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Affiliation(s)
- Yurika Otoki
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
- Food and Biodynamic Laboratory, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Adam H. Metherel
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, ON, M5S 1A8, Canada
| | - Theresa Pedersen
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Jun Yang
- Department of Entomology and Nematology, College of Agriculture and Environmental Sciences, University of California, Davis, CA 95616, USA
- Comprehensive Cancer Center, Medical Center, University of California, Davis, CA 95616, USA
| | - Bruce D. Hammock
- Department of Entomology and Nematology, College of Agriculture and Environmental Sciences, University of California, Davis, CA 95616, USA
- Comprehensive Cancer Center, Medical Center, University of California, Davis, CA 95616, USA
- West Coast Metabolomics Center, Genome Center, University of California–Davis, Davis, CA 95616, USA
| | - Richard P. Bazinet
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, ON, M5S 1A8, Canada
| | - John W. Newman
- West Coast Metabolomics Center, Genome Center, University of California–Davis, Davis, CA 95616, USA
- Department of Nutrition, University of California–Davis, Davis, CA 95616, USA
- United States Department of Agriculture, Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA 95616, USA
| | - Ameer Y. Taha
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
- West Coast Metabolomics Center, Genome Center, University of California–Davis, Davis, CA 95616, USA
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Taha AY, Chang L, Chen M. Threshold changes in rat brain docosahexaenoic acid incorporation and concentration following graded reductions in dietary alpha-linolenic acid. Prostaglandins Leukot Essent Fatty Acids 2016; 105:26-34. [PMID: 26869088 PMCID: PMC4752724 DOI: 10.1016/j.plefa.2015.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/06/2015] [Accepted: 12/11/2015] [Indexed: 12/23/2022]
Abstract
BACKGROUND This study tested the dietary level of alpha-linolenic acid (α-LNA, 18:3n-3) required to maintain brain (14)C-Docosahexaenoic acid (DHA, 22:6n-3) metabolism and concentration following graded α-LNA reduction. METHODS Fischer-344 (CDF) male rat pups (18-21 days old) were randomized to the AIN-93G diet containing as a % of total fatty acids, 4.6% ("n-3 adequate"), 3.6%, 2.7%, 0.9% or 0.2% ("n-3 deficient") α-LNA for 15 weeks. Rats were intravenously infused with (14)C-DHA to steady state for 5 min, serial blood samples collected to obtain plasma, and brains excised following microwave fixation. Labeled and unlabeled DHA concentrations were measured in plasma and brain to calculate the incorporation coefficient, k*, and incorporation rate, J(in). RESULTS Compared to 4.6% α-LNA controls, k* was significantly increased in ethanolamine glycerophospholipids in the 0.2% α-LNA group. Circulating unesterified DHA and brain incorporation rates (J(in)) were significantly reduced at 0.2% α-LNA. Brain total lipid and phospholipid DHA concentrations were reduced at or below 0.9% α-LNA. CONCLUSION Threshold changes for brain DHA metabolism and concentration were maintained at or below 0.9% dietary α-LNA, suggesting the presence of homeostatic mechanisms to maintain brain DHA metabolism when dietary α-LNA intake is low.
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Affiliation(s)
- Ameer Y Taha
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of California, Davis, CA, USA.
| | - Lisa Chang
- Brain Physiology and Metabolism Section, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - Mei Chen
- Brain Physiology and Metabolism Section, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
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Karmi A, Iozzo P, Viljanen A, Hirvonen J, Fielding BA, Virtanen K, Oikonen V, Kemppainen J, Viljanen T, Guiducci L, Haaparanta-Solin M, Någren K, Solin O, Nuutila P. Increased brain fatty acid uptake in metabolic syndrome. Diabetes 2010; 59:2171-7. [PMID: 20566663 PMCID: PMC2927939 DOI: 10.2337/db09-0138] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To test whether brain fatty acid uptake is enhanced in obese subjects with metabolic syndrome (MS) and whether weight reduction modifies it. RESEARCH DESIGN AND METHODS We measured brain fatty acid uptake in a group of 23 patients with MS and 7 age-matched healthy control subjects during fasting conditions using positron emission tomography (PET) with [(11)C]-palmitate and [(18)F]fluoro-6-thia-heptadecanoic acid ([(18)F]-FTHA). Sixteen MS subjects were restudied after 6 weeks of very low calorie diet intervention. RESULTS At baseline, brain global fatty acid uptake derived from [(18)F]-FTHA was 50% higher in patients with MS compared with control subjects. The mean percentage increment was 130% in the white matter, 47% in the gray matter, and uniform across brain regions. In the MS group, the nonoxidized fraction measured using [(11)C]-palmitate was 86% higher. Brain fatty acid uptake measured with [(18)F]-FTHA-PET was associated with age, fasting serum insulin, and homeostasis model assessment (HOMA) index. Both total and nonoxidized fractions of fatty acid uptake were associated with BMI. Rapid weight reduction decreased brain fatty acid uptake by 17%. CONCLUSIONS To our knowledge, this is the first study on humans to observe enhanced brain fatty acid uptake in patients with MS. Both fatty acid uptake and accumulation appear to be increased in MS patients and reversed by weight reduction.
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Affiliation(s)
- Anna Karmi
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Patricia Iozzo
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
- PET Centre, Institute of Clinical Physiology, National Research Council, Pisa, Italy
| | - Antti Viljanen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Jussi Hirvonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Barbara A. Fielding
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, University of Oxford, Churchill Hospital, Oxford, U.K
| | - Kirsi Virtanen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Vesa Oikonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Jukka Kemppainen
- Department of Clinical Physiology and Nuclear Medicine, University of Turku and Turku University Hospital, Turku, Finland
| | - Tapio Viljanen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Letizia Guiducci
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
- PET Centre, Institute of Clinical Physiology, National Research Council, Pisa, Italy
| | | | - Kjell Någren
- Department of Clinical Physiology and Nuclear Medicine, PET and Cyclotron Unit, Rigshospitalet, Copenhagen University, Copenhagen, Denmark
| | - Olof Solin
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
- Department of Medicine, University of Turku and Turku University Hospital, Turku, Finland
- Corresponding author: Pirjo Nuutila,
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Wakabayashi S, Freed LM, Chang M, Rapoport SI. In vivo imaging of brain incorporation of fatty acids and of 2-deoxy-D-glucose demonstrates functional and structural neuroplastic effects of chronic unilateral visual deprivation in rats. Brain Res 1995; 679:110-22. [PMID: 7648253 DOI: 10.1016/0006-8993(95)00069-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Regional cerebral 'incorporation coefficients' k* of each of 3 labeled long-chain fatty acids -[9,10-3H]palmitate ([3H]PA), [1-14C]arachidonate ([14C]AA) and [1-14C]docosahexaenoate ([14C]DHA)-were measured using quantitative autoradiography in 11 bilateral brain visual areas of 3.5-month-old awake, hooded, Long-Evans rats, and were compared with regional cerebral metabolic rates for glucose (rCMRglc). The rats, which had undergone unilateral orbital enucleation at 15 days of age, were studied either in the dark with eyelids of the intact eye sutured, or when stimulated in a light box with the intact eye open. rCMRglc did not differ between homologous contralateral and ipsilateral visual areas in the dark or during stimulation, but was elevated bilaterally by 25% or more in many visual areas during stimulation compared with dark. Contralateral compared with ipsilateral k* was lower for each fatty acid tracer in superficial gray of the superior colliculus (in dark and during stimulation) and dorsal nucleus of lateral geniculate body (during stimulation). In the dark, k* for [3H]PA was correlated significantly with rCMRglc for the 22 visual areas studied, whereas during stimulation k* for [14C]AA was correlated with rCMRglc. These results suggest that central neuroplastic changes following chronic unilateral enucleation are accompanied by reduced incorporation of [3H]PA, [14C]AA and [14C]DHA into contralateral brain ares that normally receive crossed retinofugal fibers, and by symmetry of rCMRglc in the dark but increased bilateral symmetrical responsiveness of rCMRglc to visual stimulation of the intact eye.
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Affiliation(s)
- S Wakabayashi
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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Gazzah N, Gharib A, Bobillier P, Lagarde M, Sarda N. Evidence for brain docosahexaenoate recycling in the free-moving adult rat: implications for measurement of phospholipid synthesis. Neurosci Lett 1994; 177:103-6. [PMID: 7824158 DOI: 10.1016/0304-3940(94)90055-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The specific activity (SA) of unesterified docosahexaenoic acid (22:6 n-3) in the brain and arterial plasma was measured after constant intravenous infusion of [3H] 22:6 n-3 in the free-moving rat. Within 40-105 min, an apparent steady state of labeled unesterified 22:6 n-3 in plasma and in brain was reached. However, the values of the brain to plasma 22:6 n-3 SA ratios ranged from 0.03 to 0.05, indicating that an isotopic equilibrium between brain and plasma was not attained. This suggests that a considerable endogenous source of unesterified 22:6 n-3 (95-97%) (likely derived from lipid metabolism) dilutes the SA of the tracer coming from plasma. Using the SA of 22:6 in plasma instead of brain would thus lead to a gross underestimation of the rate of phospholipid synthesis.
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Affiliation(s)
- N Gazzah
- INSERM U 352, Laboratoire de Chimie Biologique, INSA-Lyon, Villeurbanne, France
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Wakabayashi S, Freed LM, Bell JM, Rapoport SI. In vivo cerebral incorporation of radiolabeled fatty acids after acute unilateral orbital enucleation in adult hooded Long-Evans rats. J Cereb Blood Flow Metab 1994; 14:312-23. [PMID: 8113326 DOI: 10.1038/jcbfm.1994.38] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We examined effects of acute unilateral enucleation on incorporation from blood of intravenously injected unsaturated [1-14C]arachidonic acid ([14C]AA) and [1-14C]docosahexaenoic acid ([14C]DHA), and of saturated [9,10-3H]palmitic acid ([3H]PA), into visual and nonvisual brain areas of awake adult Long-Evans hooded rats. Regional cerebral metabolic rate for glucose (rCMRglc) values also were assessed with 2-deoxy-D-[1-14C]glucose ([14C]DG). One day after unilateral enucleation, an awake rat was placed in a brightly lit visual stimulation box with black and white striped walls, and a radiolabeled fatty acid was infused for 5 min or [14C]DG was injected as a bolus. [14C]DG also was injected in a group of rats kept in the dark for 4 h. Fifteen minutes after starting an infusion of a radiolabeled fatty acid, or 45 min after injecting [14C]DG, the rat was killed and the brain was prepared for quantitative autoradiography. Incorporation coefficients k* of fatty acids, or rCMRglc values, were calculated in homologous brain regions contralateral and ipsilateral to enucleation. As compared with ipsilateral regions, rCMRglc was reduced significantly (by as much as -39%) in contralateral visual areas, including the superior colliculus, lateral geniculate body, and layers I, IV, and V of the primary (striate) and secondary (association, extrastriate) visual cortices. Enucleation did not affect incorporation of [3H]PA into contralateral visual regions, but reduced incorporation of [14C]AA and of [14C]DHA by -18.5 to -2.1%. Percent reductions were correlated with percent reductions in rCMRglc in most but not all regions. No effects were noted at any of nine non-visual structures that were examined. These results indicate that enucleation acutely reduces neuronal activity in contralateral visual areas of the awake rat and that the reductions are coupled to reduced incorporation of unsaturated fatty acids into sn-2 regions of phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Reduced fatty acid incorporation likely reflects reduced activity of phospholipases A2 and/or phospholipase C.
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Affiliation(s)
- S Wakabayashi
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
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Nariai T, Greig NH, DeGeorge JJ, Genka S, Rapoport SI. Intravenously injected radiolabelled fatty acids image brain tumour phospholipids in vivo: differential uptakes of palmitate, arachidonate and docosahexaenoate. Clin Exp Metastasis 1993; 11:141-9. [PMID: 8444007 DOI: 10.1007/bf00114972] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
This paper investigates the incorporation of intravenously (i.v.) administered radiolabelled fatty acids--[9,10(3)-H]palmitate (3H-PA), [1-14C]arachidonate (14C-AA) and [1-14C]docosahexaenoate (14C-DHA)--into intracerebrally implanted tumours in awake Fischer-344 rats. A suspension of Walker 256 carcinosarcoma tumour cells (1 x 10(6) cells) was implanted into the right cerebral hemisphere of 8- to 9-week-old rats. Seven days after implantation, the awake rat was infused i.v. for 5 min with 3H-PA (6.4 mCi/kg), 14C-AA (170 microCi/kg) or 14C-DHA (100 microCi/kg). Twenty minutes after the start of infusion, the rat was killed and coronal brain sections were obtained for quantitative autoradiography and histology. Each fatty acid showed well-demarcated incorporation into tumour tissue. Areas of necrosis or haemorrhage showed no or small levels of incorporation. The ratios of incorporation into the tumour to incorporation into contralateral brain regions were 2.8-5.5 for 3H-PA, 2.1-3.3 for 14C-AA and 1.5-2.2 for 14C-DHA. The mean ratios differed significantly between the fatty acids (P < 0.01). 3H-PA was not incorporated into necrotic tumours despite the presence of an open blood-tumour barrier, indicated by extravasated horseradish peroxidase. The incorporation rate constant of 3H-PA was similar for small intracerebral and large extracerebral tumours. The results show that 3H-PA, 14C-AA and 14C-DHA are incorporated more readily into tumour tissue than into brain, and that the increase is primarily due to increased utilization of fatty acids by tumour cells and not due to a high blood-tumour permeability. The relative increases in rates of incorporation for the different fatty acids may be related to lipid composition of the tumour and to the requirement of and specific role of these fatty acids in tumour cell growth and division.
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Affiliation(s)
- T Nariai
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892
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Robinson PJ, Noronha J, DeGeorge JJ, Freed LM, Nariai T, Rapoport SI. A quantitative method for measuring regional in vivo fatty-acid incorporation into and turnover within brain phospholipids: review and critical analysis. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1992; 17:187-214. [PMID: 1467810 DOI: 10.1016/0165-0173(92)90016-f] [Citation(s) in RCA: 213] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An experimental method and its associated mathematical model are described to quantitate in vivo incorporation rates into and turnovers of fatty acids (FAs) within stable brain metabolic compartments, particularly phospholipids. A radiolabeled FA is injected i.v. in a rat, and arterial plasma unacylated FA radioactivities and unlabeled concentrations are sampled until the animal is killed after 15 min, when the brain is analyzed biochemically or with quantitative autoradiography. Unbound unacylated label in blood easily crosses the blood-brain barrier; rapidly equilibrates in the unacylated FA, acyl-CoA and phosphatidate-diacylglycerol brain pools; then is incorporated into phospholipids and other stable metabolic compartments. Uptake and incorporation of labeled FAs are independent of cerebral blood flow at constant brain blood volume. Different labeled FAs enter specific sn positions of different brain phospholipids, suggesting that a combination of probes can be used to investigate metabolism of these phospholipids. Thus, [9,10-3-H]palmitate preferentially labels the sn1 position of phosphatidylcholine; [1-14C]arachidonate the sn2 positions of phosphatidylinositol and phosphatidylcholine; and [1-14C]docosahexaenoate the sn2 positions of phosphatidylethanolamine and phosphatidylcholine. The FA model provides an operational equation for rates of incorporation of FAs into brain phospholipids, taking into account intracerebral recycling and de novo synthesis of the FA, as well as entry into brain of FA from acylated blood sources. The equation is essentially independent of specific details of the proposed model, and can be used to calculate turnovers and half-lives of FAs within different phospholipid classes. For the model to be most applicable, experiments should satisfy conditions for pulse-labeling of the phospholipids, with brain sampling times short enough to minimize exchange of label between stable metabolic compartments. A 15-20 min sampling time satisfies these criteria. The FA method has been used to elucidate the dynamics of brain phospholipids metabolism in relation to brain development, brain tumor, chronically reduced auditory input, transient ischemic insult, axotomy with and without nerve regeneration, and cholinergic stimulation in animals with or without a chronic unilateral lesion of the nucleus basalis magnocellularis.
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Affiliation(s)
- P J Robinson
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892
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