Towards a better understanding of diabetic atherogenesis

Bruce Wong

    Research output: ThesisDoctoral Thesis

    463 Downloads (Pure)

    Abstract

    [Truncated abstract] Background: Macrophages in arterial walls accumulate lipids leading to the development of atherosclerotic plaques which progress to cause heart attacks or strokes. However, mechanisms underlying macrophage lipid accumulation are often studied without accounting for risk factors such as dyslipidemia alone, and diabetes with or without dyslipidemia. Objectives: Human-derived macrophages (hMDMs) tend to be cultured under generic conditions or with supplementation of oxidized low-density lipoproteins (oxLDL) to unphysiological levels to create a model of the diseased/pathological state. Therefore, I aimed to develop a more physiological model of macrophage to foam cell transition using diabetic or non-diabetic human sera with contrasting endogenous lipid profiles. Firstly, I sought to investigate the effect of varying concentrations of triglyceride within physiological range on macrophage fatty acid (FA) accumulation and expression of cholesterol efflux proteins. Next, I investigated the effect of severe hyperlipidemia on macrophage lipid accumulation and FA composition and expression of genes involved in lipid metabolism. Lastly, I examined effects of dyslipidemic diabetic serum on macrophage lipid accumulation as a model of foam cell formation. Methods: To investigate the effect of subtle variations in triglyceride levels on macrophage lipid metabolism, normal human monocytes were cultured in media supplemented with 10% serum derived from pooled fresh frozen plasma varying triglyceride concentrations (A to D, with increasing triglyceride concentrations). To investigate the effects of severe hyperlipidemia on macrophage lipid metabolism, monocytes were cultured in media supplemented with 10% human serum pooled from control normolipidemic (Con) or from a hyperlipidemic subject (Hyp). To investigate effects of dyslipidemic, diabetic or dyslipidemic diabetic serum on macrophage lipid accumulation, monocytes were cultured in media supplemented with 10% serum pooled from control non-diabetic normolipidemic (A) or non-diabetic hypercholesterolemic subjects (B) vs. subjects with type 2 diabetes (C); diabetes with hypertriglyceridemia (D); or diabetes with hypercholesterolemia (E). Human monocyte-derived macrophages (hMDMs) were harvested for analysis of lipid content and FA composition, cholesterol efflux and expression of genes relevant to lipid metabolism, followed by siRNA inhibition of differentially expressed genes. Results: Exposure to higher triglyceride concentrations in media resulted in hMDMs with greater intracellular lipid content compared with controls. Analysis of macrophage FA confirmed that hMDMs exposed to higher triglyceride concentrations had increased total FA content compared with controls (876 μg/mg protein vs 652 μg/mg protein, p
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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