Mechanism of lipoprotein retention by the extracellular matrix

Lipoproteins: When size really matters

The field of nanoscience is extending the applications of physics, chemistry and biology into previously unapproached infinitesimal length scales. Understanding the behavior and manipulating the positions and properties of single atoms and molecules hold great potential to improve areas of science as disparate as medicine and computation, and communication and orbiting satellites. Yet, in the race to develop novel, previously unavailable nanoparticles, there is an opportunity for scientists in this field to digress and to apply their growing understanding of nanoscience and the tools of nanotechnology to one of the most pressing problems in all of human biology-diseases related to lipoproteins. Although not appreciated outside the field of lipoprotein biology, variations in the compositions, structures and properties of these nanoscale-sized, blood-borne particles are responsible for most of the variations in health, morbidity and mortality in the Western world. If the lipoproteins could be understood at the nanometer length scale with precise details of their structures and functions, scientists could understand a wide range of perplexing physiological processes and also address the dysfunctions in normal lipoprotein biology that lead to such diseases as hypercholesterolemia, heart disease, stroke and neurodegenerative diseases. Furthermore, if the capabilities of nanoscience to assemble and manipulate nanometer-sized particles could be recruited to studies of lipoproteins, these biological particles would provide a new dimension to therapeutic agents, and these natural particles could be designed to carry out many specialized beneficial tasks.

Role of diabetes in atherosclerotic pathogenesis. What have we learned from animal models?

Diabetes mellitus is associated with a greater risk of developing atherosclerosis and its complications: stroke, myocardial infarction, and peripheral vascular disease. In patients with diabetes, atherosclerosis represents a complex multifactorial disease with increased lesion progression and severity compared to the nondiabetic population. Several risk factors have been proposed to explain the increased risk of cardiovascular disease with diabetes. They include: hyperglycaemia, dyslipidemia, accelerated formation of advanced glycation end-products (AGEs), increased oxidative stress, and genetic factors. It is difficult to precisely establish the elements leading to diabetes-accelerated atherosclerosis by means of epidemiological studies because all these factors coexist in diabetic patients. Thus, diabetic animal models that reproduce exacerbation of atherosclerosis would be helpful to understand why atherosclerosis is accelerated by diabetes, and to design appropriate treatments to limit its progression. This review analyzes most of the animal models developed to reproduce diabetes-accelerated atherosclerosis, and summarizes the effects of hyperglycaemia and lipid abnormalities on atherogenesis.

Increased Apolipoprotein Deposits in Early Atherosclerotic Lesions Distinguish Symptomatic From Asymptomatic Patients

OBJECTIVE

Apolipoprotein E (apoE) and apolipoprotein B100 (apoB) are both involved in receptor-mediated uptake of atherogenic lipoproteins by the liver. Inefficient hepatic clearance of these lipoproteins leads to symptomatic atherosclerosis. Using arterial tissue microarrays, we tested the hypothesis that apoE and apoB accumulation in the arterial wall discriminates between patients with symptomatic atherosclerosis and patients who never experienced cardiovascular events.

METHODS AND RESULTS

In a postmortem study involving 49 patients (22 patients with symptomatic atherosclerosis), we quantified apolipoprotein deposits in arterial rings obtained from the left main coronary, the common carotid, the common iliac, and the renal artery applying tissue microarray technology and semiquantitative immunohistochemistry. In early atherosclerotic lesions, even before atheroma appeared, symptomatic patients had significantly more arterial apoE and apoB deposits than patients without cardiovascular events (P<0.001). Among the symptomatic patients, those without diabetes had more intense apolipoprotein deposits than diabetics. Large amounts of apoE and apoB were found in advanced atherosclerotic lesions, regardless of the activity of the disease.

CONCLUSIONS

Increased apolipoprotein deposits are an early sign of symptomatic atherosclerosis. They may reflect either enhanced retention of atherogenic lipoproteins or impaired local apolipoprotein degradation. The arterial lipoprotein turnover may be different in diabetic patients.

A proteomic study of the apolipoproteins in LDL subclasses in patients with the metabolic syndrome and type 2 diabetes

The exchangeable apolipoproteins present in small, dense LDL (sdLDL) and large, buoyant LDL subclasses were evaluated with a quantitative proteomic approach in patients with the metabolic syndrome and with type 2 diabetes, both with subclinical atherosclerosis and the B LDL phenotype. The analyses included surface-enhanced laser adsorption/ionization, time-of-flight mass spectrometry, and subsequent identification by mass spectrometry or immunoblotting and were carried out in LDL subclasses isolated by ultracentrifugation in deuterium oxide gradients with near physiological salt concentrations. The sdLDLs of both types of patients were enriched in apolipoprotein C-III (apoC-III) and were depleted of apoC-I, apoA-I, and apoE compared with matched healthy controls with the A phenotype. The LDL complexes formed in serum from patients with diabetes with the arterial proteoglycan (PG) versican were also enriched in apoC-III. In addition, there was a significant correlation between the apoC-III content in sdLDL in patients and the apparent affinity of their LDLs for arterial versican. The unique distribution of exchangeable apolipoproteins in the sdLDLs of the patients studied, especially high apoC-III, coupled with the augmented affinity with arterial PGs, may contribute to the strong association of the dyslipidemia of insulin resistance with increased risk for cardiovascular disease.