Ancient Bacteria

It's generally agreed that low-grade chronic inflammation is related to metabolic syndrome, cardiovascular disease, and type 2 diabetes. But no one knows what causes this generalized inflammation.

Acute, localized inflammation is a good thing. It's what walls off an infection, "eats" the offending organism, and then digests it with the help of heavy-duty oxidants. Then, when things are working right, the body repairs the damage, and the cells that have been doing all this leave the scene.

Chronic inflammation, on the other hand, is not a good thing, and the more scientists can find out about it, the better.

Hence I was intrigued by a recent paper in Nature that proposed a totally new idea and confirmed an old idea. You can read a popularized description here, or a link to the original paper here.

When we are invaded by pathogens, the body mounts what is called the innate immune response. This is a nonspecific response triggered by certain chemicals on the surface of many organisms that are unique to them and are not found on our own cells. The body sends out cells called macrophages to engulf the offending organisms and sends chemical signals to recruit other cell types to help rid the body of the organisms and then repair any damage that occurred.

This response is more primitive than the adaptive immune response that uses antibodies and is more specific than the innate immune response.

Usually, the cause of the response is clear, as bacteria or viruses or other pathogens can be found in the blood. But sometimes people seem to have such a response when no pathogens can be found. This puzzled scientists for a long time.

But Carl Hauser and colleagues, the authors of the Nature paper, came up with a fascinating hypothesis. It is generally accepted that mitochondria, known as the "powerhouses of the cell" because they are where most of the cell's energy is produced, were originally bacteria that invaded the cells of other organisms and adapted to the benefit of both.

Mitochondria have their own DNA, which comes only from the mother.

Hauser and colleagues wondered if perhaps trauma that destroys cells could release mitochondria from the damaged cells into the bloodstream. Then, because the mitochondria are descended from bacteria, they might have surface molecules that our bodies would interpret as foreign, so we would mount an innate immune response, just as we do to other bacteria.

His researched suggested that this does indeed happen.

It explains why severe trauma patients sometimes get reactions that look like severe infections when no signs of infecting organisms can be found.

And I wonder if less severe chronic trauma could cause just enough of an innate immune response to trigger chronic disease. For example, we know that chronic gum disease can increase blood glucose levels, along with various signs if inflammation. Could this be because the gum disease is causing gum cells to break down and release mitochondria?

Could other hidden infections be doing the same? By reducing various chronic infections, could we reduce people's chance of getting type 2 diabetes?

I find this research exciting, not because it offers an immediate chance for a cure of type 2 diabetes, but because it's a new idea and I find new paradigm-shifting ideas much more fascinating than huge studies of drugs that rely on statistics to prove anything. Even then, although the statistics can show that the drug worked on average, it can never show whether or not it will help you in particular, as I discussed here.

Creative new ideas can suggest new research paths that may some day lead to real cures.







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