Browsing by Author "Soveral, Graca"
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- Contents of conjugated linoleic acid isomers in ruminant-derived foods and estimation of their contribution to daily intake in PortugalPublication . Martins, Susana V.; Lopes, Paula A.; Alfaia, Cristina M.; Ribeiro, Veronica S.; Guerreiro, Teresa V.; Fontes, Carlos M. G. A.; Castro, Matilde F.; Soveral, Graca; Prates, Jose A. M.The present study provides a detailed overview of the contents of conjugated linoleic acid (CLA) isomers in the most consumed Portuguese CLA-rich foods (milk, butter, yoghurt, cheese, beef and lamb meat), by using silver ion-HPLC. In addition, the contribution of these ruminant-derived foods to the daily intake of CLA isomers was estimated based on Portuguese consumption habits. The total CLA concentration in milk and dairy products ranged from 4.00 mg/g fat in yoghurt to 7.22 mg/g fat in butter, and, regarding meats, from 4-45 mg/g fat in intensively produced beef to 11.29 mg/g fat in lamb meat. The predominant CLA isomers identified in these products were cis-9,trans-11 (59.89-79.21 %) and trans-7,cis-9 (8.04-20.20%). The average estimated total CLA intake for the Portuguese population was 73.70mg/d. Milk and cheese are probably the two products with the highest contribution to the final CLA intake, as a result of their high fat content and consumption values. The results also suggested that cis-9,trans-11 and trans-7,cis-9 are the isomers most represented, with, respectively, 76.10 and 12.56 % of the total CLA intake. Being the first detailed report on the contents of total and individual CLA isomers in Portuguese commercial ruminant-derived foods, we further discuss the implication of the results for diet characteristics and human health.
- Effect of dietary conjugated linoleic acid isomers on water and glycerol permeability of kidney membranesPublication . Soveral, Graca; Martins, Ana P.; Martins, Susana V.; Lopes, Paula A.; Alfaia, Cristina M.; Prates, Jose A. M.; Moura, Teresa F.Conjugated linoleic acid (CLA) refers to a group of positional and geometrical isomers of linoleic acid in which the double bonds are conjugated. Dietary CLA has been associated with various health benefits although details of its molecular mode of action remain elusive. The effect of CLA supplemented to palm oil-based diets in Wistar Fats, as a mixture of both or isolated c9,t11 and t11,c12 isomers, was examined on water and glycerol membrane permeability of kidney proximal tubule. Although water permeability was unaltered, an increase in glycerol permeability was obtained for the group supplemented with CLA mixture, even though the activation energy for glycerol permeation remained high. This effect was correlated with an increased CLA isomeric membrane incorporation for the same dietary group. These results suggest that diet supplementation with CLA mixture, in contrast to its individual isomers, may enhance membrane fluidity subsequently raising kidney glycerol reabsorption. (C) 2009 Elsevier Inc. All rights reserved.. - FCT [POCT1/CVT/2002/44750, PTDC/CVT/2006/66114, SFRH/BD/2005/22566, SFRH/BPD/2005/23931]. - This study was supported by FCT Grants POCT1/CVT/2002/44750 and PTDC/CVT/2006/66114 and individual FCT fellowships to Susana Martins (SFRH/BD/2005/22566) and Paula Alexandra Lopes (SFRH/BPD/2005/23931). The authors acknowledge Ana Madeira for technical support. We also thank Susana Alves and Rui Bessa (Unidade de Proclucao Animal, L-INIA-REQUIMTE) for providing fatty acid profile analyses.
- Membrane tension regulates water transport in yeastPublication . Soveral, Graca; Madeira, Ana; Loureiro-Dias, Maria C.; Moura, Teresa F.Evidence that membrane surface tension regulates water fluxes in intact cells of a Saccharomyces cerevisiae strain overexpressing aquaporin AQY1 was obtained by assessing the osmotic water transport parameters in cells equilibrated in different osmolarities. The osmotic water permeability coefficients (P-f) obtained for yeast cells overexpressing AQY1 incubated in low osmolarity buffers were similar to those obtained for a double mutant aqy1aqy2 and approximately three times lower (with higher activation energy, E-a) than values obtained for cells incubated in higher osmolarities (with lower E-a). Moreover, the initial inner volumes attained a maximum value for cells equilibrated in lower osmolarities (below 0.75 M) suggesting a pre-swollen state with the membrane under tension, independent of aquaporin expression. In this situation, the impairment of water channel activity suggested by lower P-f and higher E-a could probably be the first available volume regulatory toot that, in cooperation with other osmosensitive solute transporters, aims to maintain cell volume. The results presented point to the regulation of yeast water channels by membrane tension, as previously described in other cell systems. (C) 2008 Elsevier B.V. All rights reserved.. - Fundacao para a Ciencia e Tecnologia [POCT1/AGR/57403/2004]. - This work was supported by Fundacao para a Ciencia e Tecnologia, POCT1/AGR/57403/2004. We thank Doctor Paulo Costa Lemos, REQUIMTE, Portugal, for the supervision on the epifluorescence experiments.
- Pyruvate uptake is inhibited by valproic acid and metabolites in mitochondrial membranesPublication . Aires, Catia C. P.; Soveral, Graca; Luis, Paula B. M.; ten Brink, Herman J.; de Almeida, Isabel Tavares; Duran, Marinus; Wanders, Ronald J. A.; Silva, Margarida F. B.The pyruvate uptake rate in inverted submitochondrial vesicles prepared from rat liver was optimized and further characterized; the potential inhibitory effects of the anticonvulsive drug valproic acid or 2-n-propyl-pentanoic acid (VPA), Delta(4)-valproic acid or 2-n-propyl-4-pentenoic acid and the respective coenzyme A ( CoA) conjugates were studied in the presence of a proton gradient. All tested VPA metabolites inhibited the pyruvate uptake, but the CoA esters were stronger inhibitors (40% and 60% inhibition, respectively, for valproyl-CoA and Delta(4)-valproyl-CoA, at 1 mM). At the same concentration, the specific inhibitor 2-cyano-4-hydroxycinnamate decreased the pyruvate uptake rate by 70%. The reported inhibition of the mitochondrial pyruvate uptake may explain the significant impairment of the pyruvate-driven oxidative phosphorylation induced by VPA. (C) 2008 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.. - Fundacao para a Ciencia e a Tecnologia (FCT) , Lisboa, Portugal [POCTI/FCB/48800/2002]; FEDER ; [SFRH/BD/22420/2005]. - This work was financially supported by Fundacao para a Ciencia e a Tecnologia (FCT), Lisboa, Portugal (POCTI/FCB/48800/2002 with partial funding of FEDER and SFRH/BD/22420/2005).
- Valproic acid metabolites inhibit dihydrolipoyl dehydrogenase activity leading to impaired 2-oxoglutarate-driven oxidative phosphorylationPublication . Luis, Paula B. M.; Ruiter, Jos P. N.; Aires, Catia C. P.; Soveral, Graca; de Almelda, Isabel Tavares; Duran, Marinus; Wanders, Ronald J. A.; Silva, Margarida F. B.The effect of the antiepileptic drug valproic acid (VPA) on mitochondrial oxidative phosphorylation (OXPHOS) was investigated in vitro. Two experimental approaches were used, in the presence of selected respiratory-chain Substrates: (1) formation of ATP i
- Water transport in intact yeast cells as assessed by fluorescence self-quenchingPublication . Soveral, Graca; Madeira, Ana; Loureiro-Dias, Maria C.; Moura, Teresa F.Intact yeast cells loaded with 5- and-6-carboxyfluorescein were used to assess water transport. The results were similar to those previously reported for protoplasts assessed by using either fluorescence or light scattering, and the activation energies were 8.0 and 15.1 kcal mol(-1) (33.4 and 63.2 kJ mol(-1)) for a strain overexpressing AQY1 aquaporin and a parental strain, respectively.