Atherosclerosis. Why do we pretend the pathogenesis is mysterious?

The emperor's tailors: the failure of the medical weight loss paradigm and its causal role in the obesity of America

During the past century, the medical profession has developed a paradigm for the treatment of obesity, which prescribes specific exercise and dietary goals under the umbrella of 'lifestyle change'. It has three components, all of which evolved from origins that had nothing to do with weight control. First, it is individually prescriptive, that is weight loss is considered the responsibility of the individual as contrasted to a societal or group responsibility. Second, it recommends exercise aimed towards structured, or non-functional, activities with a variety of physiological endpoints. Last, dietary goals are defined by calories, exchanges, food groups and various nutritional components. Diets are usually grouped by these goals. This model is unique to America, it is not working and it has also played a causal role in the obesity it is attempting to eliminate. A new model must be developed, which contains an observationally based societal prescription and links activity with functional outcomes and diets, which are food rather than nutritionally based.

Concentration polarization of macromolecules in canine carotid arteries and its implication for the localization of atherogenesis

To test the hypothesis that concentration polarization of atherogenic lipids may occur in the arterial system and play an important role in the localization of atherogenesis, we measured in vitro the luminal surface concentration of bovine serum albumin (as a tracer macromolecule) in the canine carotid artery by directly taking liquid samples from the luminal surface of the artery. The experimental results show that the luminal surface albumin concentration, c(w), was higher than the bulk concentration, c(0) as predicted by our theory. The relative luminal surface albumin concentration, c(w)/c(0), decreased very sharply at low wall shear rate, G, but gradually approached the value of 1.0 asymptotically as G was increased. The experiment shows that water flux rate across the vessel wall, v(w), has a profound impact on concentration polarization. For instance, at G = 0 and 185 s(-1), when v(w) = 8.9 +/- 1.7 x 10(-6) cm/s, c(w) was 65% and 15% higher than c(0), respectively, meanwhile when v(w) = 4.8 +/- 0.6 x 10(-6)cm/s, c(w) was only 42% and 5% higher than c(0), respectively. The experiment also revealed that concentration polarization occurred in a thin layer close to the luminal surface of the artery. The thickness of this layer was water flux rate-dependent. The higher the water flux rate, the thicker was the layer. The present study therefore confirms that concentration polarization can indeed occur in the arterial system and our theoretical analysis is accurate in predicting this mass transfer phenomenon.

Fluid filtration across the arterial wall under flow conditions: is wall shear rate another factor affecting filtration rate?

The effect of flow on fluid filtration across an arterial wall was investigated in the canine common carotid artery. The arteries were cannulated in situ to maintain their in vivo length and endothelium intact. The excised vessels were pressurized at 120 mmHg through an overflow head-tank system that provided a constant flow rate to the perfused vessels. Filtration rates across the walls of the carotid arteries tested were measured under 4 different experimental conditions: 1) albumin-free Krebs solution under absent flow condition; 2) albumin-free Krebs solution with flow (148 +/- 8 ml/min); 3) Krebs solution containing 1.0 g/dl bovine serum albumin under absent flow condition; 4) Krebs solution containing 1.0 g/dl bovine serum albumin with flow (148 +/- 8 ml/min). Under absent flow conditions, the addition of albumin to the Krebs solution (1.0 g/dl) led to an approximate 25% drop in filtration rate (p < 0.001). It was found that fluid flow affected the filtration rate of the albumin solution, yet failed to affect the filtration rate of albumin-free solution across the arterial wall. The present study suggests that the change in filtration rate of the albumin solution under flow condition may indicate the change in the luminal surface concentration of albumin due to flow.

Science, atherosclerosis and the "age of unreason": a review

Research in atherosclerosis has been dominated by the lipid hypothesis. The pathology of both the cholesterol-fed animal and of familial hypercholesterolemia has been misrepresented. The vascular lesions of these disorders are not atherosclerotic but manifestations of fat storage. There has been undue faith in the epidemiology of coronary heart disease and atherosclerosis. Fundamental defects in the epidemiological approach to the cause of atherosclerosis include: (1) misuse of cause and risk factors; (2) misuse of coronary heart disease as an imprecise and inappropriate surrogate endpoint in clinical and mortality studies; (3) use of fallacious monocausal death certificates and mortality rates; (4) assumed causal role of risk factors; (5) use of fallacious dietary data; (6) ecological fallacies; (7) nonspecificity of statistical correlations and selection bias; (8) failure to take note of inconsistencies; (9) inappropriate use of the blood cholesterol level as a surrogate of atherosclerosis (substitution game) without demonstration of any such effect on arteries; and (10) misplaced faith in pathological and experimental corroborative evidence. The epidemiology of atherosclerosis is based on unscientific methodology and the lipid hypothesis as currently envisaged is invalid. There is need to review the cholesterol-lowering campaign especially for normolipidemic subjects.

Koch's postulates and experimental atherosclerosis

Koch's postulates contributed substantially to the evolution of scientific knowledge of infectious diseases, but are inapplicable to chronic non-infectious, degenerative diseases such as atherosclerosis. In experimental atherogenesis compliance with appropriately modified postulates is essential to preclude spurious causes from consideration. The crux of such postulates is that the experimental procedure must reproduce the disease and its complications and their pathogenesis and experimental conditions must be analogous to those prevailing in man. Since atherosclerosis is not species specific to man and consists of multiple lesions, which develop independently of one another but can ultimately coalesce, reproduction of the disease in a localized segment of a blood vessel in susceptible animals under conditions similar to those prevailing in man would comply with the spirit of Koch's postulates.

Accuracy of numerical coronary profile. Correlation of risk factors with arteriographically documented severity of atherosclerosis

We compared a coronary risk profile (developed by the Framingham Study) based on age, sex, cigarette smoking, glucose intolerance, left ventricular hypertrophy, systolic blood pressure and serum cholesterol to angiographically determined severity of coronary-artery disease in 158 consecutive patients undergoing cardiac catheterization. A profile of 1.0 indicated average relative risk. Risk profiles for 105 patients with angiographically documented coronary-artery disease was 1.52 whereas it was 1.08 for the group without coronary disease (P less than 0.01). There was no difference between the patients with coronary disease with (1.44) and those without previous infarct (1.46). The coronary risk profile, however, increased with increasing severity of coronary disease. The high-risk coronary patient can be identified by seven easily measured risk factors, and the extent of coronary-artery disease increases with the number and severity coronary risk factors.

The role of lipid in the pathogenesis of atherosclerosis

An experimental model of atherosclerosis sheep veins identical to the human disease indicates (i) that ingestion of an atherogenic diet is not a prerequistie in atherosclerosis and (ii) that haemodynamic stress must be the dominant aetiological factor in atherosclerosis. Ultrastructural studies reveal that the early lipid deposition in spontaneous human atherosclerosis and in haemodynamically induced atherosclerosis is related to the trasnformation of extracellular vesicular debris into closely packed membranous profiles with electron-translucent centres. It is postulated that the vesicular dtsintegration of mural cells is due to the same haemodynamic stresses which induce degenerative changes in the vascular connective tissues, and that the lipid accumulation within the vesicular disintegration of mural cells is due to the same haemodynamic stresses which induce degenerative changes in the vascular connective tissues, and that the lipid accumulation within the vesicular debris is a cellular debris which have not undergone resolution or phagocytosis.