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Godoy Coto J, Pereyra EV, Cavalli FA, Valverde CA, Caldiz CI, Maté SM, Yeves AM, Ennis IL. Exercise-induced cardiac mitochondrial reorganization and enhancement in spontaneously hypertensive rats. Pflugers Arch 2024:10.1007/s00424-024-02956-7. [PMID: 38625371 DOI: 10.1007/s00424-024-02956-7] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 03/22/2024] [Accepted: 03/28/2024] [Indexed: 04/17/2024]
Abstract
The myocardium is a highly oxidative tissue in which mitochondria are essential to supply the energy required to maintain pump function. When pathological hypertrophy develops, energy consumption augments and jeopardizes mitochondrial capacity. We explored the cardiac consequences of chronic swimming training, focusing on the mitochondrial network, in spontaneously hypertensive rats (SHR). Male adult SHR were randomized to sedentary or trained (T: 8-week swimming protocol). Blood pressure and echocardiograms were recorded, and hearts were removed at the end of the training period to perform molecular, imaging, or isolated mitochondria studies. Swimming improved cardiac midventricular shortening and decreased the pathological hypertrophic marker atrial natriuretic peptide. Oxidative stress was reduced, and even more interesting, mitochondrial spatial distribution, dynamics, function, and ATP were significantly improved in the myocardium of T rats. In the signaling pathway triggered by training, we detected an increase in the phosphorylation level of both AKT and glycogen synthase kinase-3 β, key downstream targets of insulin-like growth factor 1 signaling that are crucially involved in mitochondria biogenesis and integrity. Aerobic exercise training emerges as an effective approach to improve pathological cardiac hypertrophy and bioenergetics in hypertension-induced cardiac hypertrophy.
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Affiliation(s)
- Joshua Godoy Coto
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Erica V Pereyra
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Fiorella A Cavalli
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Claudia I Caldiz
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner" - Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina
| | - Alejandra M Yeves
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina.
| | - Irene L Ennis
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata (UNLP) - CONICET, La Plata, Argentina.
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Vázquez RF, Ovalle-García E, Antillón A, Ortega-Blake I, Muñoz-Garay C, Maté SM. Formation and Nanoscale Characterization of Asymmetric Supported Lipid Bilayers Containing Raft-Like Domains. Methods Mol Biol 2022; 2402:243-256. [PMID: 34854049 DOI: 10.1007/978-1-0716-1843-1_19] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The development of new strategies for achieving stable asymmetric membrane models has turned interleaflet lipid asymmetry into a topic of major interest. Cyclodextrin-mediated lipid exchange constitutes a simple and versatile method for preparing asymmetric membrane models without the need for sophisticated equipment. Here we describe a protocol for preparing asymmetric supported lipid bilayers mimicking membrane rafts by cyclodextrin-mediated lipid exchange and the main guidelines for obtaining structural information and quantitative measures of their mechanical properties using Atomic force microscopy and Force spectroscopy; two powerful techniques that allow membrane characterization at the nanoscale.
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Affiliation(s)
- Romina F Vázquez
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
- Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
| | - Erasmo Ovalle-García
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Armando Antillón
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Carlos Muñoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
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Vázquez RF, Ovalle-García E, Antillón A, Ortega-Blake I, Bakás LS, Muñoz-Garay C, Maté SM. Asymmetric bilayers mimicking membrane rafts prepared by lipid exchange: Nanoscale characterization using AFM-Force spectroscopy. Biochim Biophys Acta Biomembr 2020; 1863:183467. [PMID: 32871116 DOI: 10.1016/j.bbamem.2020.183467] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 08/07/2020] [Accepted: 08/24/2020] [Indexed: 01/03/2023]
Abstract
Sphingolipids-enriched rafts domains are proposed to occur in plasma membranes and to mediate important cellular functions. Notwithstanding, the asymmetric transbilayer distribution of phospholipids that exists in the membrane confers the two leaflets different potentials to form lateral domains as next to no sphingolipids are present in the inner leaflet. How the physical properties of one leaflet can influence the properties of the other and its importance on signal transduction across the membrane are questions still unresolved. In this work, we combined AFM imaging and Force spectroscopy measurements to assess domain formation and to study the nanomechanical properties of asymmetric supported lipid bilayers (SLBs) mimicking membrane rafts. Asymmetric SLBs were formed by incorporating N-palmitoyl-sphingomyelin (16:0SM) into the outer leaflet of preformed 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Cholesterol SLBs through methyl-β-cyclodextrin-mediated lipid exchange. Lipid domains were detected after incorporation of 16:0SM though their phase state varied from gel to liquid ordered (Lo) phase if the procedure was performed at 24 or 37 °C, respectively. When comparing symmetric and asymmetric Lo domains, differences in size and morphology were observed, with asymmetric domains being smaller and more interconnected. Both types of Lo domains showed similar mechanical stability in terms of rupture forces and Young's moduli. Notably, force curves in asymmetric domains presented two rupture events that could be attributed to the sequential rupture of a liquid disordered (Ld) and a Lo phase. Interleaflet coupling in asymmetric Lo domains could also be inferred from those measurements. The experimental approach outlined here would significantly enhance the applicability of membrane models.
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Affiliation(s)
- Romina F Vázquez
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina; Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115, 1900 La Plata, Argentina.
| | - Erasmo Ovalle-García
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210 Cuernavaca, México
| | - Armando Antillón
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210 Cuernavaca, México
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210 Cuernavaca, México
| | - Laura S Bakás
- Centro de Investigación en Proteínas Vegetales (CIProVe), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115, 1900 La Plata, Argentina
| | - Carlos Muñoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, 62210 Cuernavaca, México
| | - Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina.
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Vázquez RF, Daza Millone MA, Pavinatto FJ, Fanani ML, Oliveira ON, Vela ME, Maté SM. Impact of sphingomyelin acyl chain (16:0 vs 24:1) on the interfacial properties of Langmuir monolayers: A PM-IRRAS study. Colloids Surf B Biointerfaces 2019; 173:549-556. [DOI: 10.1016/j.colsurfb.2018.10.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 09/28/2018] [Accepted: 10/09/2018] [Indexed: 11/17/2022]
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Vázquez RF, Daza Millone MA, Pavinatto FJ, Herlax VS, Bakás LS, Oliveira ON, Vela ME, Maté SM. Interaction of acylated and unacylated forms of E. coli alpha-hemolysin with lipid monolayers: a PM-IRRAS study. Colloids Surf B Biointerfaces 2017; 158:76-83. [PMID: 28683345 DOI: 10.1016/j.colsurfb.2017.06.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 06/12/2017] [Accepted: 06/19/2017] [Indexed: 11/18/2022]
Abstract
Uropathogenic strains of Escherichia coli produce virulence factors, such as the protein toxin alpha-hemolysin (HlyA), that enable the bacteria to colonize the host and establish an infection. HlyA is synthetized as a protoxin (ProHlyA) that is transformed into the active form in the bacterial cytosol by the covalent linkage of two fatty-acyl moieties to the polypeptide chain before the secretion of HlyA into the extracellular medium. The aim of this work was to investigate the effect of the fatty acylation of HlyA on protein conformation and protein-membrane interactions. Polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) experiments were performed at the air-water interface, and lipid monolayers mimicking the outer leaflet of red-blood-cell membranes were used as model systems for the study of protein-membrane interaction. According to surface-pressure measurements, incorporation of the acylated protein into the lipid films was faster than that of the nonacylated form. PM-IRRAS measurements revealed that the adsorption of the proteins to the lipid monolayers induced disorder in the lipid acyl chains and also changed the elastic properties of the films independently of protein acylation. No significant difference was observed between HlyA and ProHlyA in the interaction with the model lipid monolayers; but when these proteins became adsorbed on a bare air-water interface, they adopted different secondary structures. The assumption of the correct protein conformation at a hydrophobic-hydrophilic interface could constitute a critical condition for biologic activity.
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Affiliation(s)
- Romina F Vázquez
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata, 60 y 120, 1900, La Plata, Argentina
| | - María A Daza Millone
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT- La Plata, CONICET. Universidad Nacional de La Plata, Sucursal 4 Casilla de Correo 16, 1900, La Plata, Argentina
| | - Felippe J Pavinatto
- Instituto de Física de São Carlos (IFSC), Universidade de São Paulo, SP, Brazil
| | - Vanesa S Herlax
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata, 60 y 120, 1900, La Plata, Argentina
| | - Laura S Bakás
- Centro de Investigación de Proteínas Vegetales (CIPROVE), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas. Universidad Nacional de La Plata. 47 y 115, 1900, La Plata, Argentina
| | - Osvaldo N Oliveira
- Instituto de Física de São Carlos (IFSC), Universidade de São Paulo, SP, Brazil
| | - María E Vela
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT- La Plata, CONICET. Universidad Nacional de La Plata, Sucursal 4 Casilla de Correo 16, 1900, La Plata, Argentina
| | - Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata, 60 y 120, 1900, La Plata, Argentina.
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Maté SM, Vazquez R, Pavinatto FJ, Daza-Millone MA, Herlax V, Bakas L, Oliveira ON, Vela ME. Orientational Properties of DOPC/SM/Cholesterol Mixtures: A PM-IRRAS Study. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Vázquez RF, Maté SM, Bakás LS, Muñoz-Garay C, Herlax VS. Relationship between intracellular calcium and morphologic changes in rabbit erythrocytes: Effects of the acylated and unacylated forms of E. coli alpha-hemolysin. Biochim Biophys Acta 2016; 1858:1944-53. [PMID: 27206406 DOI: 10.1016/j.bbamem.2016.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 04/15/2016] [Accepted: 05/16/2016] [Indexed: 12/28/2022]
Affiliation(s)
- Romina F Vázquez
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina
| | - Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina
| | - Laura S Bakás
- Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115, 1900 La Plata, Argentina
| | - Carlos Muñoz-Garay
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México (UNAM), Av. Universidad 2001, Col. Chamilpa, 62210 Cuernavaca, Mexico
| | - Vanesa S Herlax
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina.
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Maté SM, Vázquez RF, Herlax VS, Daza Millone MA, Fanani ML, Maggio B, Vela ME, Bakás LS. Boundary region between coexisting lipid phases as initial binding sites for Escherichia coli alpha-hemolysin: A real-time study. Biochimica et Biophysica Acta (BBA) - Biomembranes 2014; 1838:1832-41. [DOI: 10.1016/j.bbamem.2014.02.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 02/24/2014] [Accepted: 02/27/2014] [Indexed: 11/29/2022]
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Maté SM, Layerenza JP, Ves-Losada A. Arachidonic acid pools of rat kidney cell nuclei. Mol Cell Biochem 2010; 345:259-70. [DOI: 10.1007/s11010-010-0580-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 08/28/2010] [Indexed: 11/29/2022]
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Maté SM, Herlax VS, Wolf C, Bakás LS. Long and unsaturated sphingomyelin determines selective cholesterol extraction from sheep erythrocytes detergent-resistant membranes. Chem Phys Lipids 2010. [DOI: 10.1016/j.chemphyslip.2010.05.074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Maté SM, Layerenza JP, Ves-Losada A. Incorporation of arachidonic and stearic acids bound to L-FABP into nuclear and endonuclear lipids from rat liver cells. Lipids 2007; 42:589-602. [PMID: 17551764 DOI: 10.1007/s11745-007-3063-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2007] [Accepted: 04/09/2007] [Indexed: 10/23/2022]
Abstract
The incorporation of exogenous fatty acids bound to L-FABP into nuclei was studied. Rat liver cell nuclei and nuclear matrices (membrane depleted nuclei) were incubated in vitro with [1-(14)C]18:0 and 20:4n-6 either free or bound to L-FABP, ATP and CoA. FA esterification in whole nuclei and endonuclear lipids was ATP-CoA-dependent, and with specificity regarding fatty acid type and lipid class. 18:0 and 20:4n-6, free or L-FABP bound, showed the same incorporation and esterification pattern in lipids of whole nuclei. Only 20:4n-6 L-FABP bound was less incorporated into TAG with respect to free 20:4n-6. In the nuclear matrix, 18:0 free or L-FABP bound was esterified with a higher specific activity (SA) into: PtdEtn > PtdIns, PtdSer > PtdCho. 20:4n-6 free or L-FABP bound was esterified into: PtdIns > PtdEtn > PtdCho. 20:4n-6:L-FABP was esterified in endonuclear total-PL and PtdIns with a greater SA with respect to free 20:4n-6 and with a minor one as FFA. To summarize, trafficking of FA to nuclei includes esterification of 18:0 and 20:4n-6 either free or L-FABP-bound, into nuclear and endonuclear lipids by an ATP-CoA-dependent pathway. Endonuclear fatty acid esterification was more active than that in whole nuclei, and independent of the nuclear membrane. Esterification patterns of fatty acids L-FABP-bound or free into whole nuclear lipids were the same whereas in the nuclear matrix, L-FABP could play an important role in the mobilization of 20:4n-6 into specific sites of utilization such as the PtdIns pools.
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Affiliation(s)
- Sabina M Maté
- Facultad de Ciencias Médicas, Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CONICET-UNLP, 60 y 120, 1900 La Plata, Argentina
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Abstract
Lipids are not only components of cell nucleus membranes, but are also found in the membrane-depleted nuclei where they fulfill special functions. We have investigated the lipid composition of membrane-depleted rat liver nuclei obtained by incubation with low Triton X-100 concentrations of 0.04% and 0.08%, which rendered them unaltered or hardly altered. Under these conditions, 26% of proteins and 22% of phospholipids were recovered. The main phospholipids were phosphatidylcholine > phosphatidylethanolamine > phosphatidylinositol = or > phosphatidylserine and sphingomyelin (in decreasing concentrations). The fatty acid components of total lipids and phosphatidylcholine were mainly unsaturated. Over 40% belonged to the n-6 series (arachidonic > or = 25% and linoleic 15%); approximately 40% corresponded to saturated acids and <10% were monoenoic. Endonuclear phosphatidylcholine was built up by 16 molecular species, the most abundant being 18:0-20:4 (32%), 16:0-20:4 (19%), 16:0-18:2 (13%), and 18:0-18:2 (11%). The fatty acid composition and phosphatidylcholine molecular species distribution in the membrane-depleted nucleus of rat liver showed patterns similar to the whole nucleus, mitochondria, microsomes, and homogenate of the parent liver cells, suggesting that endonuclear lipid pool composition is mainly determined by a liver organ profile.
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Affiliation(s)
- Sabina M Maté
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, UNLP-CONICET, calles 60 y 120, Argentina
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Abstract
This study was performed to determine whether fatty acids incorporated into liver cell nuclei phosphatidylcholine (PtdCho) could be remodeled in the isolated nuclear. For this reason, rat liver cell nuclei were incubated in vitro with [1-14C]20:4n-6-CoA. PtdCho molecular species with the highest specific activity had an unsaturated fatty acid at sn-1 and sn-2 positions (20:4-20:4>18:2-20:4>18:1-20:4). 16:0-20:4 and 18:0-20:4 PtdChos showed a minor specific activity. When labeled nuclei were reincubated in the absence of labeled substrate with the addition of cytosol, ATP and CoA, the specific activity of 20:4-20:4, 18:2-20:4 and 18:1-20:4 species decreased, while that of 16:0-20:4 and 18:0-20:4 increased. In conclusion, the asymmetric fatty acid distribution of saturated fatty acids at sn-1 position, and unsaturated fatty acids at sn-2 position of nuclear PtdCho molecular species was re-established by an acyl-CoA-dependent remodeling process.
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Affiliation(s)
- S M Maté
- Facultad de Ciencias Médicas, Instituto de Investigaciones Bioquímicas de La Plata, UNLP-CONICET, calles 60 y 120, 1900 La Plata, Argentina
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Abstract
Liver nuclear incorporation of stearic (18:0), linoleic (18:2n-6), and arachidonic (20:4n-6) acids was studied by incubation in vitro of the [1-14C] fatty acids with nuclei, with or without the cytosol fraction at different times. The [1-14C] fatty acids were incorporated into the nuclei as free fatty acids in the following order: 18:0 > 20:4n-6 >> 18:2n-6, and esterified into nuclear lipids by an acyl-CoA pathway. All [1-14C] fatty acids were esterified mainly to phospholipids and triacylglycerols and in a minor proportion to diacylglycerols. Only [1-14C]18:2n-6-CoA was incorporated into cholesterol esters. The incorporation was not modified by cytosol addition. The incorporation of 20:4n-6 into nuclear phosphatidylcholine (PC) pools was also studied by incubation of liver nuclei in vitro with [1-14C]20:4n-6-CoA, and nuclear labeled PC molecular species were determined. From the 15 PC nuclear molecular species determined, five were labeled with [1-14C]20:4n-6-CoA: 18:0-20:4, 16:0-20:4, 18:1-20:4, 18:2-20:4, and 20:4-20:4. The highest specific radioactivity was found in 20:4-20:4 PC, which is a minor species. In conclusion, liver cell nuclei possess the necessary enzymes to incorporate exogenous saturated and unsaturated fatty acids into lipids by an acyl-CoA pathway, showing specificity for each fatty acid. Liver cell nuclei also utilize exogenous 20:4n-6-CoA to synthesize the major molecular species of PC with 20:4n-6 at the sn-2 position. However, the most actively synthesized is 20:4-20:4 PC, which is a quantitatively minor component. The labeling pattern of 20:4-20:4 PC would indicate that this molecular species is synthesized mainly by the de novo pathway.
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Affiliation(s)
- A Ves-Losada
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), Facultad de Ciencias Médicas, UNLP-CONICET, La Plata, Argentina.
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