Photometric measurement of lipoprotein-cholesterol after agarose electrophoresis: comparison with single-spin ultracentrifugal analysis

High plasma phospholipase A2 activity, inflammation markers, and LDL alterations in obesity with or without type 2 diabetes

Plasma phospholipases A(2) (PLA(2)) hydrolyze phospholipids of circulating lipoproteins or deposited in arteries producing bioactive lipids believed to contribute to the atherosclerotic inflammatory response. PLA(2)(s) are elevated in obesity and type 2 diabetes (T2D) but it is not clear which of these conditions is the cause since they frequently coexist. This study attempts to evaluate if high plasma PLA(2)(s) activities and markers of their effects in lipoproteins are associated with obesity or T2D diabetes, or with both. Total PLA(2) and Ca(2+)-dependent and -independent activities, lipids, lipoproteins, apoAI, and apoB apolipoproteins and affinity of apoB-lipoproteins for arterial proteoglycans were measured, as well as Inflammation markers. These parameters were evaluated in plasma samples of four groups: (i) apparently healthy controls with normal BMI (nBMI), (ii) obese subjects with no T2D, (iii) patients with T2D but with nBMI, and (iv) obese patients with T2D. PLA(2) activities were measured in the presence and absence of Ca(2+) and in the presence of specific inhibitors. Obese subjects, with or without T2D, had high activities of total PLA(2) and of Ca(2+)-dependent and Ca(2+)-independent enzymes. The activities were correlated with inflammation markers in obese subjects with and without diabetes and with alterations of low-density lipoproteins (LDLs) that increased their affinity for arterial proteoglycans. Ca(2+)-dependent secretory (sPLA(2)) enzymes were the main responsible of the obesity-associated high activity. We speculate that augmented PLA(2)(s) activity that increases affinity of circulating LDL for arterial intima proteoglycans could be another atherogenic component of obesity.

Intravascular hemolysis increases atherogenicity of diet-induced hypercholesterolemia in rabbits in spite of heme oxygenase-1 gene and protein induction

Free radical mediated oxidation of apoB lipoproteins in the arterial intima appears to contribute to atherogenicity of the entrapped particles. A plausible pathogenic mechanism for oxidation is the one induced by heme leaking from erythrocytes that is then carried into the arterial wall by its high affinity for lipoproteins. In the intima, in the presence of H(2)O(2) secreted by macrophages, heme can be a potent oxidant. To study the role of heme as a promoter of oxidative stress damage in vivo we used a model of intravascular hemolysis (IVH) caused by phenylhydrazine in rabbits with and without diet-induced moderate hypercholesterolemia (MHC). Evaluation of the antioxidant status of plasma indicated that at the end of the treatment period this was compromised by the MHC-IVH. After 10 weeks the animals with combined MHC-IVH showed more of the aorta surface covered by lesions (27%+/-8, mean (SD) than the animals with only MHC (11%+/-7), in spite of having similar plasma levels of VLDL+LDL lipoproteins. The animals with only IVH, as well as the controls, showed minimal lesions (<1%). Heme oxygenase (HO-1) expression in aorta and other tissues was markedly increased in the group with MHC-IVH and it was correlated with the extent of IVH. The data suggest that the oxidative stress associated with IVH potentiates the atherogenicity of moderate hypercholesterolemia and that in spite of a strong induction of HO-1 this is not sufficient to counteract the atherogenicity of the combined condition.

Advances in agarose gel electrophoresis of serum lipoproteins

Agarose gel electrophoresis has been extensively employed by researchers to gain a greater understanding of lipoprotein biology and its relationship to cardiovascular disease. Advances in this technique have been made in the visualization and quantitation of separated lipoproteins, in the use of agarose gel electrophoresis for detection and quantitation of apolipoproteins of the separated lipoproteins, and in the detection of lipoprotein heterogeneity. Agarose gel electrophoresis has been employed for two-dimensional electrophoretic analysis of lipoproteins as well as in several different methods which probe the immunological properties of lipoproteins. Agarose gel electrophoresis has thus become an important tool in the study of serum lipoproteins in both clinical and basic science laboratories.

Circulating immune complexes, immunoglobulins, complement, antibodies to dietary antigens, cholesterol and lipoproteins levels in patients with occlusive coronary lesions

The presence of circulating immune complexes, serum immunoglobulins, C3 (the third component of complement), antibodies to alpha-lactalbumin, beta-lactoglobulin and bovine serum albumin was studied in 39 patients subjected to coronary arteriography. Total serum cholesterol and triglycerides and cholesterol in VLDL, LDL and HDL were also estimated. The results obtained in the group of patients found with occlusive lesions were compared with those found in the group without lesions. With one of the five assays used for the detection of immune complexes, higher and significant levels were found in the group with lesions. A negative and significant correlation was found between the number of vessels with lesions and the levels of serum C3.