16th August 2018
Having talked about the end, I shall now talk about the beginning of cardiovascular disease (CVD). Or, to be more precise, the beginning of atherosclerotic plaque development.
The problem that I always had with the LDL/cholesterol hypothesis was that it relied on a mechanism of action that sounded reasonable – if you didn’t think about it in any great depth. However, once you started looking at it closely, it become more and more unlikely. Namely, the idea that it is possible for low density lipoprotein to simply “leak” into artery walls, triggering the development of atherosclerotic plaques.
Whilst everyone, and I mean everyone (apart from about a hundred flat-earthers), confidently states that leakage of LDL in the artery wall is the first step in atherosclerotic plaque development, the pattern of atherosclerosis around the body is impossible to reconcile with this hypothesis.
Lets just start with a short list of problems. It may not look short, but it is. Just don’t get me started on ‘oxidised LDL’ and LDL particle size, and inflammation, and suchlike:
One: If LDL is leaking into artery walls, by active transport, or down a concentration gradient, or through any other mechanism you can come up with, why doesn’t it leak into all artery walls at exactly the same rate? Or, to put this another way, why are some arteries devoid of atherosclerotic plaques, when other arteries, in the same person, are highly atherosclerotic?
In the same way, how can you have a discrete area of plaque in an artery wall, when the rest of the artery wall, even the opposite side of the artery wall, is plaque free. Or, to put this another way, why does LDL leak through only in certain places, and not others?
If your answer is that LDL can only leak through in areas of arterial/endothelial damage then I would say, fine, reasonable argument. However, it means that the starting point for atherosclerosis is arterial/endothelial damage – not LDL leaking into the artery wall. And once you have damage to the arterial wall, you have moved into a completely different ball game. The ball game of endothelial damage and clot formation. Which means that you are now in my world. My rules, I win.
Two: Why does LDL never leak into vein walls? Again, if your hypothesis is that LDL can get past endothelial cells and then move straight into the artery wall, then why cannot it do this in veins? Veins and arteries have exactly the same basic structure. Arteries are somewhat thicker, with more smooth muscle and suchlike, but otherwise all is the same, and the endothelial cells lining both arteries and veins are identical in structure and function.
And no, the high blood pressure in an artery cannot force LDL into the artery wall. Whilst pressure may be involved in damaging the artery wall, pressure alone cannot be the answer. For pressure to force LDL into the artery wall, you would first have to breach the endothelial layer, at which point everything else in the bloodstream would flood into the artery wall at the same time. Then you are into the ‘damage to the blood vessels’ discussion again. My rules, I win.
Three: The arteries, at least those where atherosclerosis develops, have their own blood supply. Yes, bigger blood vessels (both arteries and veins) have their own blood vessels to provide them with the nutrients they require – the vasa vasorum, literally ‘blood vessels of the blood vessels.’
LDL molecules can freely move out of the vasa vasorum, and into the surrounding artery wall – then back again. Therefore, the concentration of LDL in the artery wall, and the bloodstream, is identical. So, for one thing, there can be no concentration gradient between the LDL in the blood flowing through the artery, and within the artery wall itself.
Equally, even if LDL did enter the artery wall by passing through the endothelial layer and then, against all the laws of physics, the concentration of LDL in the artery wall managed to rise above that in the bloodstream, it would simply be absorbed back into the vasa vasorum to be taken back into the blood circulating around the body.
To put this another way, there is nothing to stop LDL entering the artery wall, and vein walls, via the vasa vasorum. So, why does LDL entering the artery wall from the blood, that is flowing through the artery, cause damage, when the LDL entering the artery wall (and vein walls) from the vasa vasorum does no harm? Same LDL, same rules.
Four: The intact/healthy endothelial layer is impermeable to LDL, no matter what the concentration in the blood. We know this because the brain has to manufacture its own cholesterol because, in turn, LDL cannot force entry through the endothelial cells that line the blood vessels.
In the brain all endothelial cells, even in the smallest blood vessels (capillaries) remain tightly locked together, which is the ‘structure’ that creates the blood brain barrier (BBB).
‘The BBB is defined as the ‘microvasculature’ of the brain and is formed by a continuous layer of capillary endothelium joined by tight junctions that are generally impermeable (except by active transport) to most large molecules, including antibodies and other proteins.’1
In the rest of the body, when you reach the level of capillaries, these minute blood vessels are loosely bound, with gaps between the endothelial cells. There are also holes (fenestrations) in the endothelial cells themselves. Which is why LDL can move in and out of the vasa vasorum quite easily. This is not the case in the brain, or the larger blood vessels, where tight junctions are the rule.
In short, an intact endothelial layer, with the cells locked together by protein bridges – as found in the BBB and in all large arteries – cannot be penetrated by LDL. Indeed, if it were possible for LDL to simply force entry into, and then pass straight though endothelial cells, you would not need LDL receptors to get LDL into cells, and you do.
This is why, in familial hypercholesterolaemia (FH) the level of LDL rises very high. It rises very high because there are fewer LDL receptors on cells, so the LDL remains trapped in the bloodstream. Somewhat ironically, FH provides powerful proof that the LDL/cholesterol hypothesis must be wrong, because it proves that LDL cannot enter cells unless the cell has an LDL receptor. At least it disproves the idea that LDL can simply move through endothelial cells.
As for the idea that LDL can slip through the gaps between endothelial cells. This too, is impossible. Endothelial cells, in larger arteries, and in the BBB, are locked together very tightly indeed. I quote here from Wikipedia. If you don’t like Wikipedia, then go to Google and look up “IMAGES” ‘tight junctions between endothelial cells.’ You will see how impossible it is for LDL to pass between endothelial cells that line artery walls.
‘Tight Junctions prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells, so materials must actually enter the cells in order to pass through the tissue.’2 Wikipedia ‘tight junction’.
Yes, there is not enough of a gap for ions (charged atoms) to pass between endothelial cells. Which means the idea that an LDL molecule, which is tens of thousands of times bigger – probably hundreds of thousands – can slip between cells is quite clearly, nonsense. It is like suggesting a super-tanker can slip through a gap that a rowing boat cannot.
Five: The only possible way that LDL could leak past or through the undamaged endothelium is if the endothelium wants it to get past. That would require active transport through endothelial cells. Now active transport exists – it is called transcytosis. A substance is absorbed into the cell on one side, it is then transported through the cell, and pops out the other side. [Transcytosis is clearly not possible with LDL, as we already know that it cannot cross the blood brain barrier BBB]
However, transcytosis only happens if the cell has a reason to transcytose a molecule. It is tightly controlled and highly complex process. It does not happen by chance, It is unaffected by any concentration gradient. It is the action of a living entity. In this case, an endothelial cell [other cells are just as clever].
The idea that an endothelial cell would be programmed to absorb LDL from the bloodstream, then actively transport it through itself, then deposit it in the artery wall behind – for no reason whatsoever – defies all laws of biology and physiology – and any other natural laws that you can think of. Especially when the artery wall can get any and all the LDL it requires from the vasa vasorum.
Now, there are more problems than this, but I am not taking it any further at present, as that is enough to be going on with. The counter argument has always been, well you do find LDL in atherosclerotic plaques, so it must have got there by passing through the endothelium.
Hmmmm. Well, as pointed out in the last blog, you can find red blood cells in atherosclerotic plaques too, and we know for an absolute certainty that red blood cells cannot penetrate the undamaged endothelium. Simply finding a substance in an atherosclerotic plaque does not mean it caused the plaque in the first place.
Having said all of this, the alterative ‘blood clotting’ hypothesis appears to immediately run into an alternative problem. When you look at early stage atherosclerotic plaques, they do not obviously look anything like a blood clot. In fact, they are often referred to as ‘fatty streaks.’ No sign of a blood clot there (at least, so it is almost universally believed).
I don’t refer to them as fatty streaks, because that immediately sets your thinking off down the fat/cholesterol LDL pathway, from where it can never again emerge. I prefer to call early stage plaques “fibrous streaks” which is far more descriptive of what they are, and what they look like.
However, that is slightly jumping ahead of myself. What I am going to do now, is to take you back in time to the 1960s and 1970s. A time when researchers were actually trying to work out exactly what was going on with CVD. Rather than now, when the LDL hypothesis is just accepted as an inarguable fact. Which means that no-one researches plaque growth any more, in any meaningful way. Or at least, they can only research it by accepting that, whatever else you see, LDL is the cause.
So, let us begin by looking at the fatty streak in more detail, as described in the book ‘Factors in Formation and Regression of the Atherosclerotic Plaque.’
‘Juvenile-type fatty streaks are the earliest lesions that can be recognized by macroscopic inspection of aortas of children. They characteristically appear as small yellow/white dots most frequently in longitudinal lines between the intercostal branches (places where arteries that travel around the chest branch out from the aorta. Intercostal means, between ribs). They stain brilliantly red with macroscopic Sudan staining, and Holman reported that they were already present in all children aged more than 3, increased rapidly in area between ages 8 – 15, and reached a maximum age 20.’
So, yes, there are such things as fatty streaks. Sorry to scare you, but they start in infancy, and every single child has them by the age of three. They reach their maximum level at age 20 (when no-one has a heart attack). However, most importantly, fatty streaks do not become atherosclerotic plaques:
‘For many years it was widely believed that they (fatty streaks) were the precursors of fibrous plaques, and it was postulated that the fat-filled cells disintegrated, releasing sclerotic organic lipid that stimulated proliferation of SMCs (smooth muscle cells) and collagen. However, there is now evidence from many different sources that suggests that fatty streaks and fibrous plaques develop by separate and independent pathways.’
‘Separate and independent pathways’. Today, if you read anything on atherosclerosis, any textbook, any research paper on atherosclerosis, it will inform you that atherosclerotic plaques start as fatty streaks which gradually grow larger and turn into atherosclerotic plaques – somehow or another. This is just an accepted fact, never challenged, constantly quoted. But it is, as with most facts in the world of CVD, wrong.
In the 1970s, a couple called the Velicans undertook a painstaking review of arteries at all ages, from those who had died of accidental causes. Children to adults. Two of their key findings are worth highlighting. The first, again, is that fatty streaks do not turn into plaques. The second is the association of microthrombi with plaque formation:
‘They, (the Velicans), record many significant morphological observations. They did not observe conversion of fatty streak into atherosclerotic plaques and concluded that the two types of lesion developed as unrelated pathological processes. ‘Advanced’ fatty streaks exhibiting cell disintegration and accumulation of extracellular lipid were first encountered in the 26 – 30 age group and increased fairly rapidly over the next decade, but again they did not observe ‘further transitional stages between advanced fatty streaks and atherosclerotic plaques.
In the third decade lipid became abundant in the plaques (the plaques, not the fatty streaks) in the form of foam cells which were particularly associated with areas of insudation. (insudation is the accumulation of a substance derived from the blood), and small pools of extracellular lipid: there was also ‘progressive involvement of microthrombi in the early steps of plaque formation.‘
What does this mean? At the risk of repeating myself to death. It means that fatty streaks exist, but these ‘lesions’ are not the things that become atherosclerotic plaques. Plaques form in a completely different way.
And, when you examine early stage plaques closely, they contain microthrombi (small blood clots) and other material derived from the blood – insudation. The Velicans did not know what caused plaques, but they observed that they began life as small fibrous streaks – not fatty streaks, with progressive involvement of microthrombi.
What is the most ‘fibrous’ material in the body? It is, of course, fibrin. Fibrin is the long string of protein the body uses to bind blood clots together. Sticky fishing line, if you will. It is formed with blood clots, as part of blood clots, and it is always found in high concentrations in and around atherosclerotic plaques.
What is important to note here is the fact that everyone believes about the growth and natural history of atherosclerotic plaques – is wrong. Fatty streaks have nothing whatsoever to do with atherosclerotic plaque development. On the other hand, fibrous streaks, fibrin and microthrombi do!
Which takes us way back in time to Karl von Rokitansky, who was studying plaques in the arteries of people who had died of accidents in the 1850s. Rokitansky noted that plaques looked very much like blood clots – in various stages of repair. He then proposed that atherosclerosis begins in the intima (the bit lying just beneath endothelial cells), with deposition of thrombus (blood clot) and its subsequent organisation by the infiltration of fibroblasts and secondary lipid deposition. ‘The Encrustation Theory.’
However, what Rokitansky could not do, the Velicans could not do, and Russell Ross and Elspeth Smith and Duguid could not do – explain the following:
How can a blood clot form under the endothelium?
The answer, as readers of this blog now know, is that the blood clot formed when the endothelium was not there. It had been damaged, and/or stripped away, at which point a blood clot formed on that area and then, once the blood clot stabilised, and most of it was broken down, apart from the fibrin and a few other bits and pieces (including Lp(a)), the endothelium simply re-grew on top of it. Like all magic tricks, it is simple once you know how it’s done.
However, the existence of endothelial progenitor cells (EPCs), that could stick to, then re-grow, on top of a blood clot, was unknown until the mid-nineteen nineties. So, prior to this time, anyone suggesting the encrustation theory, or any variant thereof, could be easily dismissed. Just as Virchow dismissed Rokitansky in 1852. ‘Do not talk nonsense Rokitansky, blood clots cannot form under the endothelium – I win.’
Because of this, with no other hypothesis to challenge it, the LDL hypothesis gained such a powerful grip, that no-one was the least interested in the Encrustation theory. The time to strike had passed, the battle had been lost. The warriors grew old and withdrew from the battlefield, and then simply died of old age. Their names forgotten, ghosts in the machine.
‘After many years of neglect, the role of thrombosis in myocardial infarction is being reassessed. It is increasingly clear that all aspects of the haemostatic system are involved: not only in the acute occlusive event, but also in all stages of atherosclerotic plaque development from the initiation of atherogenesis and growth of large plaques.
Infusion of recombinant tissue plasminogen activator (rt-PA) into healthy men with no evidence of thrombotic events of predisposing conditions elicited significant production of crosslinked fibrin fragment D-dimer. Thus, in apparently healthy human subjects there appears to be a significant amount of fibrin deposited within arteries, and this should give pause for thought about the possible relationship between clotting and atherosclerosis. It also provided in vivo biochemical support for the numerous morphological studies in which mural fibrin and microthrombi have been observed adherent to both apparently normal intima and atherosclerotic lesions.
In 1852 Rokitansky discussed the ‘atheromatous process’ and asked ‘in what consists the nature of the disease.’ He suggested. ‘The deposit is an endogenous product derived from the blood, and for the most part from the fibrin of arterial blood.’ One hundred years later Duguid demonstrated fibrin within, and fibrin encrustations on fibrous plaque, and small fibrin deposits on the intima of apparently normal arteries.
These observations have been amply confirmed but, regrettably the emphasis on cholesterol and lipoproteins was so overwhelming that it was another 40 years before Duguid’s observations had a significant influence on epidemiological or interventional studies of haemostatic factors in coronary heart disease.’3
Those words were written almost thirty years ago by Dr Elspeth Smith, who once taught me at Aberdeen University. I should have listened more closely, it would have saved me twenty-nine years of research. Those words too, have now been forgotten, whilst LDL and statins bestride the world.
Silence has once again descended on this area. But when you look at it through fresh eyes, and you know of the existence of EPCs, these researchers had the answer, right there, in the palm of their hands. So close they could almost smell it. They just couldn’t quite join all the dots. They couldn’t explain how massive molecules that are normally found in the bloodstream, could get inside the artery wall. So, they were defeated by the facile, impossible, ridiculous, LDL hypothesis.
A great pity, because the encrustation theory explains what the LDL hypothesis cannot. Why do plaques form where they do, why do they not form in veins? Why do they contain substances that you can only find in blood clots? Why do so many grow in layers, like tree trunks? In fact, they all grow this way, it is just that – over time – the plaque can lose structure and turn to mush.
Why does smoking and air pollution increase the risk of CVD. How does avastin increase the risk of CVD by 1,200%? How do Rheumatoid Arthritis and Systemic Lupus erythematosus vastly increase the risk of CVD? It is because they all damage the endothelium and increase the risk of blood clotting at that point of damage. I could go on listing factor after factor. Using the encrustation theory everything can be explained, simply, quickly. There is no need to distort the evidence, no need to explain away paradoxes.
Statins, for example, which are held up as inarguable proof of the LDL hypothesis. How do they actually work to reduce the risk of CVD? It is because they increase nitric oxide synthesis in endothelial cells, and nitric oxide protects the endothelium, stimulates the growth of endothelial progenitor cells, and is also the most powerful anticoagulant agent known to nature.
‘Statins have pleiotropic effects on the expression and activity of endothelial nitric oxide synthase (eNOS) and lead to improved NO bioavailability. NO plays an important role in the effects of statins on neovascularization. In this review, we focus on the effects of statins on neovascularization and highlight specific novel targets, such as endothelial progenitor cells and NO.’4
Blood clots, blood clots. All the way down. Rokitansky was right, as were Ross, Duguid and Smith (and many others). They had worked it out, and they knew what was going on. They simply failed to convince the world. My role is to resurrect these forgotten scientific heroes and place them where they should always have been. The scientists who discovered what really causes CVD.