Let's look at old rats. If you feed rats a 5% fat diet, with the fat as "heart healthy" corn oil, you can actually make Dean Ornish look like a gourmand.
These rats are old. They are ex breeding rats. They do not have cholesterol poisoning and their diet has been specifically chosen, under a mistaken paradigm, to maximise health, longevity and breeding success.
If you eliminate the impatience of a cardiologist and wait for the rats to age, what do their coronary arteries look like? Bear in mind that rats are supposed to be resistant to arteriosclerosis (But that is probably only at the age a cardiologist can be persuaded to wait until).
First picture is an artery deep in the myocardium. This is where the disease begins in rats:
Notice the contorted internal elastic membrane between the arrows. The elastic lamina is thickened with mucopolysaccharide. There is a neat intimal cushion overlying this area. There is, err, no cholesterol. Oddly enough cholesterol does not seem to rupture elastin fibres! Like Lp(a), the LDL particle would have to carry that flick knife... Which it doesn't.
Next is an epicardial artery. These arteries, especially the left anterior, are particularly interesting because they are not supported by surrounding myocardial muscle so the artery wall is particularly pressure challenged. Apart from the appearance of multiple endothelial cushions overlying shredded elastin there are also dark black areas of "gunk" on the right hand arterial lining area of the artery. These stain positive for calcium.
There is, err, no cholesterol.
Just for fun the authors took another section from the same tissue block as was used for figure 6 and stained it for mucopolysaccharide. The section is nearly identical. This, here in figure 7, clearly shows the extent of the abnormal intima. No cholesterol. Strange that.
Do these rats get ischaemic disease? You bet!
The myocardial necrosis lesions, which are common, do not appear to be directly related to the diseased large arteries. They certainly make me think of Kurt's posts here and here on myocardial damage in marathon runners. The mice don't run, but they do carb load each and every meal. They have no choice. Carbs or starve. To me this suggests that it might actually be the diet used by marathon runners which kills them, rather than the running per se. Though the chronic cardio might well do a great deal of damage to the elastic intima due to the stretching needed to accommodate the high flow generated. But possibly they just eat rather more crap than normal human beings do. Just an idea.
It also begs the question of why cardiologist keep thinking that the cholesterol fed rat (or the equally poisoned Syrian hamster) has anything to do with human arteriosclerosis.
Peter
