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Publications (4)9.58 Total impact

  • G Camejo, B Wallin, M Enojärvi
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    ABSTRACT: Measurement of thiobarbituric acid reacting substances (TBARS), diene derivatives, and hydroperoxides are probably the most widely used procedures for evaluation of free radical-mediated oxidation of biological or model systems containing polyunsaturated fatty acids (PUFA). It is possible to write a sequence of rational reactions in which dienes formation comes first, followed by lipid hydroperoxides (LOOHs) production, and that terminates with fragmentation of the PUFA chains to carbonyl compounds that are TBARS. However, it appears that after the first few min, species of the three types co-exist even in simple suspensions of linoleic acid (1,2). These compounds are very reactive, especially in biological systems, and follow different rates of formation and conversion. Therefore, it is more informative to follow their kinetics of appearance and disappearance than to measure single time-points (3–5).
    Methods in Molecular Biology 02/1998; 108:377-87. DOI:10.1385/0-89603-472-0:377 · 1.29 Impact Factor
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    ABSTRACT: The atherogenicity of low density lipoproteins (LDL) may be modulated by its serum levels, structure and affinity for components of the intima, all properties that can be altered by diet. Linoleic acid-rich diets (n-G, 18:2) reduce the levels of LDL whereas those rich in oleic (n-9,18:1) are considered 'neutral'. However, LDL enriched in linoleic acid have been reported to be more vulnerable to free radical-mediated oxidation than those enriched in oleic, a potentially atherogenic property. The effect of dietary fats on other properties of LDL that may also modulate atherogenesis, such as size and capacity to interact with intima components, are not well established. We explored here how a change from an olive oil-rich diet (OO) to a sunflower oil-rich one (SFO) affects these parameters in a community with a traditional Mediterranean diet. Eighteen free-living volunteers were placed for 3 weeks on a diet with 31% of caloric intake as sunflower oil and then shifted for an additional 3 weeks to a diet in which OO provided 30.5% of the calories. The LDL after SFO had a fatty acids ratio of (18:2 + 18:3 + 20:4) to (16:0 + 16:1 + 18:0 + 18:1) of 1.06 +/- 0.11 compared to 0.73 +/- 0.06 after the OO period. Serum LDL was significantly lower after SFO than after OO. Unexpectedly, copper-catalyzed oxidation of LDL from the SFO period was significantly less than that of the particles from the OO period. The resistance to oxidation of LDL of the SFO and OO period related to alterations in content of the antioxidants alpha-tocopherol, beta-carotene and retinol, in addition to changes in size and fatty acids composition. In vitro binding of LDL to human arterial proteoglycans was also significantly lower for the SFO-LDL than the OO-LDL, a result that can also be attributed to the larger size of the SFO-LDL. Therefore, three properties of LDL: circulating levels, oxidizability, and affinity with intima proteoglycans, that may modulate its atherogenicity, were shifted in a favorable direction by diets rich in linoleic acid and natural antioxidants.
    Atherosclerosis 10/1996; 125(2):243-55. DOI:10.1016/S0021-9150(96)05882-0 · 3.97 Impact Factor
  • B Wallin, G Camejo
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    ABSTRACT: The oxidative modification of lipoproteins is of clinical importance because of potential contribution to atherogenesis [1, 2, 3]. An early step in the complex process of oxidation is the peroxidation of polyunsaturated fatty acids. We describe here a method for the Cu(II)-catalyzed oxidation of human low density lipoproteins with the subsequent analysis of hydroperoxides formation in a single microtitre plate. The procedure includes a modification of an iodometric peroxide assay for test tubes using a commercially available reagent. The microtitre plate method correlated well with the test tube procedure (r = 0.99) and showed comparable sensitivity and reproducibility. It was sensitive down to 0.5 nmol hydroperoxides/well and linear up to at least 20 nmol well-1. The method can handle several hundreds of samples a day with considerably less labour than the test tube procedure. It was well suited to monitor the kinetics of lipoprotein oxidation. The method was also used to test the potency of antioxidants, however, some antioxidants may interfere with the iodometric reaction and should be tested in the assay before use.
    Scandinavian Journal of Clinical and Laboratory Investigation 08/1994; 54(4):341-6. DOI:10.3109/00365519409087532 · 2.01 Impact Factor
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    ABSTRACT: Transition metals catalyze free radical-mediated oxidation of lipids and lipoproteins. This process is currently studied because of its potential relevance to pathological processes like atherosclerosis. Formation of thiobarbituric acid-reacting substances from polyenoic fatty acids is frequently used to follow oxidation of lipids and plasma lipoproteins. We describe here how Cu(II)- and Fe(III)-catalyzed oxidation of human low density lipoprotein or soy bean phospholipids and the photometric evaluation of the thiobarbituric acid-reaching substances formed can be conducted in the same 96-well microtiter plate. The procedure showed a correlation of 0.98 with conventional two-stage fluorimetric and spectrophotometric methods and also showed better reproducibility. The plate method can handle up to one plate per hour with considerably less labor than the test tube assays. The plate procedure required small volumes of diluted samples of lipoproteins lipids and reagents. The method was suitable for testing the concentration-dependent antioxidant potency of substances like probucol, butylated hydroxytoluene, and alpha-tocopherol. The method can also be used to follow the kinetics of oxidation of lipoproteins.
    Analytical Biochemistry 02/1993; 208(1):10-5. DOI:10.1006/abio.1993.1002 · 2.31 Impact Factor