Bacteria implicated in stress-related heart attacks

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By Sara Reardon

 

Stress has long been thought to trigger heart attacks, but the mechanism is unknown. Now, researchers think that bacteria could play a role. A study published today in mBio1  suggests that stress hormones can break up mats of bacteria growing on the fatty plaques in arteries, releasing the plaques and causing strokes or heart attacks.

Researchers have suspected for years that bacteria infect the plaques of hardened arteries. The plaques form a surface on which bacteria can attach and grow in masses called biofilms, held together in a scaffold. To test this, a team led by bacteriologist David Davies of Binghamton University in New York analysed arteries from 15 patients with cardiovascular disease. Using fluorescent tags that mark bacterial DNA, they discovered at least 10 species of bacteria clustered tightly around the plaques, including the biofilm-forming Pseudomonas aeruginosa.

If these biofilms are tightly attached to plaques, they may have an effect on cardiovascular disease, Davies says. Plaques in blood vessels are normally stable, but if they break up and enter the bloodstream, they can trigger blood clots that lead to heart attacks or strokes.

To test this idea, the researchers grew P. aeruginosa in artificial arteries made of silicone tubing and waited for the bacteria to form biofilms. They then flooded the tubes with the stress hormone noradrenaline, which caused the biofilms to break up.

The authors say that stress hormones in the blood trigger the body’s cells to release iron into the bloodstream. The iron causes bacteria such as P. aeruginosa to produce enzymes that sever the polymer bonds that hold the bacteria together in the biofilm matrix and attach the bacteria to the plaque. The plaque is broken up as collateral damage, Davies says. Although he says that much more research in animals and humans is needed, the work ”introduces a completely unexpected potential culprit” in the mystery of how plaques trigger heart attacks, he adds.

2 COMMENTS

  1. Wow that’s interesting stuff – makes me wonder if exercising too energetically when you’ve had a sedentary lifestyle might be enough of a stress trigger to release the plaque to do damage? I might just ease my way back into exercising more regularly…

  2. I think the sedentary lifestyle is a contradiction in terms. It’s more of a death option.

    Fortunately you can be ‘deskbound’ but not sedentary. Just buy yourself a cheap table top and legs. Chop the legs so that the modified table can sit on top of your existing desktop, but with the surface level with your elbow when standing. Just as if you were sitting at your desk. (Most table legs have adjusters for fine height adjustment – so no need to be extremely accurate in the chopping.) Put some rubber feet on the legs and make sure you place the standing desk against a wall – so that when you lean against it you’re pushing into the wall rather than pushing your desktop and all it’s fragile contents off the back of your desk onto the floor.

    While you’re getting used to the idea of standing up all day you can occasionally just sit normally at the lower level desk, or set aside the coffee tale height top desk, as if nothing has changed.

    You might also need a low stool or something like a fitness step to act like a bar rail to put up 1 foot from time to time. (Greatly reduces stress on the lower back from prolonged standing.)

    It’s something of a cliche: a sudden shock and the surprised victim dies on the spot.

    If you think you’ve got layers of plaques in your arteries then you’ve really got a problem. They’re an accident waiting to happen. Many things could dislodge them to run amok to cause heart attacks and strokes. So just avoiding shocks is not the best mitigation strategy.

    Good news is that there is clinical evidence of plaque reversal based on diet. i.e. measurably diminished atherosclerosis using scanning technology, ultrasound I think. From what I remember significant changes occurred over several months. Basically just from giving up dietary sugars and excess starch.

    Lack of use over hundreds of thousands of years means that humans have partially lost the physiological mechanisms and enzymes that enable many of us tolerate high doses of dietary starches and sugars. In comparison some other primates and grazing or browsing mammals do tolerate higher amounts of dietary starch, including cellulose, which is otherwise indigestible by humans except indirectly via hunting and eating the protein, organ, and fat tissue of browsing and grazing animals.

    The ancestral human environment provided greatly reduced availability of starches and sugars in the form of roots, honey, and fruits. Which were either only seasonally available or otherwise difficult to obtain. E.g. The hard work of digging for roots, otherwise inedible without complex preparation including soaking and cooking. And even then these foods aren’t ‘moreish’. So hard to overdose. And it’s technically impossible to overdose on actual raw fruit. That can only be done via the technology of cordials, soft drinks, juicer machines, and sports drinks. Honey bees obviously imposed other hurdles, not least of which being falling from trees in the days before elevated work platforms, safety harnesses, and beehive smokers. Plus that there just aren’t that many wild beehives around in pre-agricultural times.

    For many people who don’t exercise regularly a chronic exposure to very high doses of dietary starch can cause increasing insulin resistance. Indications being an expanding waistline. (Many people know believe that what’s currently considered normal carbohydrate consumption may be grossly excessive for inactive people.) Another key symptom of the problem is elevated blood pressure. Which is caused by a stiffening and disruption of the arterial lining following decades of exposure to mostly glucose, and also to nicotine, alcohol, and fructose (as in table sugar) ,which all have similar or significantly greater glycating effects on structural proteins. (Random unwanted protein glycation is very similar to the effects of vulcanisation on natural rubber – loses stretch, resilience, and self-healing properties of the material. Becomes more like car tyres. Possibly having extremely tough and durable arterial linings, like car tires, might not be the best option for long term human health.)

    Add lots of salt and various forms of dietary fats and you have a recipe for disaster. People who regularly exercise have various additional physiological mechanisms for rapidly sequestering excess dietary starches to prevent them from remaining too long as glucose in the blood. But people who don’t exercise have reduced options, and therefore experience significantly greater glycation damage from the blood sugar molecules. But damage only manifests after a very long time when the bodies capabilities to respond to glycation are exceeded by the rate of accumulating glycation. Not all that different to people who smoke and drink too much alcohol.

    Aside from the waistline the most obvious sign of arterial damage is elevated blood pressure. Being a consequence of chronic stress damage to the stiffer arterial structures, resulting inflammation, and healing and rehealing etc. including the accumulation of plaques. Just stopping doing this to yourself apparently allows the problem to self-correct fairly quickly. (A confounding issue is that elevated blood pressure has for a long time been attributed to kidney function and salt intake, which it probably is to some extent. But possibly is not the significant factor for most people. Quitting sugar and excess dietary starch seems to be an easy fix for most people. The reason this wasn’t known until recently was because eating less starch implies eating more protein and more fat. But protein is known to be carginogenic in large amounts, and in the pre-Ioannidis era dietary fat was ‘known’ to be the one true cause of pretty much all known diseases.)

    I think the implications are that you probably can exercise if you have normal blood pressure. But if you’re got high blood pressure then don’t attempt to exercise your way to normal blood pressure. Change you food habits first. Then start the exercise once blood pressure is normal. And get medical advice first. (As most gyms routinely request before commencing a program as a new member.)

    If the science turns out to be right then the dangerous plaque structures may dissipate in response to dietary changes. (Being low carbohydrate, low protein, high fat diet. And if you’re already fat then you can internally consume your own adipose tissue – which basically means a low everything diet. At least until you’re more or less lean again.) In the meantime there’s plenty of low impact activity that you can do. Just plain walking may be all that’s required.

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