Increased Uptake of Oxidized LDL by Macrophages from Type 2 Diabetics is Inhibited by Polyamines: An Advanced Study

Abstract

Patients with diabetes mellitus have an increased incidence of atherosclerotic cardiovascular disease. To date, considerable evidence supports a role for oxidative modified low density lipoprotein (LDL) in the pathogenesis of atherosclerosis. The aim of this study was to evaluate the effect of polyamines putrescine, spermidine and spermine on human LDL oxidation and to assess the ability of macrophages derived from type 2 diabetic patients to uptake \(\mathrm{exLDL}\). Polyamine effect was compared with \(\alpha\)-tocopherol. Four healthy subjects and eight type 2 diabetic patients were included in this study. Data were expressed as the mean S.D. Significance among experimental groups was calculated by one-way ANOVA test and Tukey HSD test for multiple comparisons, using the SPSS Program. To characterize type 2 diabetic patients and non-diabetic subjects, laboratory tests were carried out. Glucose, glycated haemoglobin (HbA1c), triglycerides, low (LDL) and high-density lipoproteins (HDL) and serum lipid peroxidation were measured in blood. The study was performed in three stages. For each stage, ten experimental conditions comparing the effect of polyamines with \(\alpha\)-tocopherol ( \(10 \mu\mathrm{M}\) solutions) on LDL oxidation and the uptake of \(Q\) xLDL by macrophages were analyzed. MDA concentration was found to be significantly higher in type 2 diabetic patients compared to healthy subjects ( \(5.6 \pm 0.58\) vs. 2.66 \(\pm 0.31\) \(\mu\)M MDA, respectively, \((P<0.05)\) ). Percent of macrophages containing oxLDL was determined by means of red oil staining. The uptake of \(Q x L D L\) by macrophages derived from diabetic patients was clear. The uptake of oxLDL was inhibited when the oxidation was prevented by polyamines or a-tocopherol. Spermine showed high antioxidant capacity ( \(96.67 \pm 1.53 \%\) vs. \(25.67 \pm 2.30 \%\) ) compared to a-tocopherol ( \(96.67 \pm 1.53 \%\) vs. \(47.00 \pm 7.20 \%\) ) at the concentration tested.
In conclusion, polyamines especially spermine, has a potent antioxidant effect compared to a-tocopherol on human LDL oxidation, followed by spermidine and putrescine. The results have clinical relevance in the diabetic complications and add knowledge on the role of polyamines as natural antioxidants. This research is not a clinical evaluation rather a functional analysis utilizing clinical samples.