Telomere length — What is a telomere and why do I care how long mine are?

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Hello everyone:

 

As promised a few months ago, here is the article on the importance of telomere length in health and aging. I had mentioned that while two decades ago most of the emphasis in natural health was on “boosting the immune system,” now there is more concern about free radicals, cell membrane stability, and telomere length.

 

So – “What’s a telomere and why do I care how long mine is?” are the questions I’ll be answering. There’s a lot of research in this area, lot with rats and mice, and fair amount with humans, but the field is rather new and that means there remain as many questions as answers. I did the research yesterday, and now today I’ll try to sort it into understandable, plain English answers.

 

A telomere is an end cap on each chromosome. They are actually made up of compressed genetic material, but do not replicate when the cell divides. In fact, for the most part, each time a cell divides, the telomere becomes a little bit shorter. They’ve been compared to the plastic tips on shoelaces.  When enough of the plastic tip on your shoelaces wears away, the shoelace begins to unravel. Likewise, when the telomere shortens too much, the chromosomes start to stick to one another, and in fact that cell can no longer divide. Under the microscope, our chromosomes look like this picture, and the bright end caps of highly compressed genetic base pairs (telomeres) are very clearly seen in this picture.

 

Image

 

Cell division is how we repair our organs. The skin cells, the surface tissue of the eye, the cells that line the digestive tract and the bone marrow cells are all particularly rapidly dividing cells. We need them to be able to continue to divide in order to keep those tissues repaired and functioning well.

 

Decades ago a researcher, Dr. Hayflick, noticed that in cell cultures, the cells can only divide so many times, and then they become senescent, or actually die.  A cell culture could go through an average of 50 population doublings, and then the culture would become senescent. This failure to be able to continue to divide apparently has a great deal to do with the quality of the telomeres. Because cells with shortened telomere’s also have DNA that sticks to itself, forming mutations, there is a strong correlation with telomere’s wearing out and the development of cancer.

 

Now that more human studies have been done, primarily looking at the length of the telomeres of white blood cells (leukocytes), we know that there are large differences in telomere length among human individuals, even at birth. They then shorten in the first few years after birth, remain stable through much of later childhood and adolescence, but then begin to shorten dramatically after adolescence.

 

There is a compound called telomerase, which in technical terms is a ribonucleoprotein complex. Telomerase is able to elongate existing telomeres. This substance is very active embryonically, but is suppressed just a few weeks after birth. Skin cells, sperm producing cells, and lymphocytes retain high levels of telomerase, and therefore are able to maintain telomere length well. Curiously, cancer cells whether in the body or in cell culture, produce huge levels of telomerase and thus effectively make themselves immortal, able to continue to divide indefinitely.

 

Stem cells as a rule also retain high telomerase activity, so research in this area involves replacement of senescent cells with deficient telomeres with the telomerase containing stem cells. There is, of course, a concern that keeping telomerase high through some artificial means throughout the body might actually cause runaway growth like a cancer, but so far in what limited experimentation has been done, just increasing telomerase has not produced an increased amount of cancer.

 

Leukocyte telomere length is pretty easy to measure, and while it is only an experimental tool right now, we may find it being used as a regular lab test in the next decade or so.  This is all in the early stages of scientific investigation, but a review article from the NIH states, “A link between telomere length and mortality has been established.”

 

Telomeres are measured in numbers of “base pairs” which is the genetic code.  The exact sequence of these base pairs is known, and is the same in everyone. A healthy young person will have a telomere length of 8,000 base pairs, dropping to more like 3,000 base pairs with aging, and in very elderly people, as low as 1500 base pairs. 

 

While telomeres do not shorten in heart muscle, because it does not divide, people with severe cardiovascular disease with plaque lined arteries have very short telomeres in the rest of their tissues, even in the bone marrow derived stem cells!

 

Other conditions associated with shortening of telomeres are diabetes, and prediabetes with insulin resistance, obesity and smoking, alcoholism, as well as any chronic inflammatory condition. We fight infection with inflammation, so chronic, long-term infection can really shorten telomeres. Chronic infection is also blamed for inflaming the lining cells of the arteries, and causing them to be blocked with plaque.  The cells found in arteriosclerotic plaque have extremely foreshortened telomeres, and many of them are fully senescent, incapable of doing any repair. 

 

A few other curious facts I discovered include that in people with congestive heart failure (and remember, the heart tissue telomeres don’t themselves grow shorter) have extremely short telomeres in the rest of their tissues.

 

High blood pressure is associated with shortened telomeres.

 

People who are born with short telomeres get clinically significant coronary artery and vascular systemic disease and die at a young age. Even the offspring of parents who have coronary artery disease will start off life with shorter telomeres.

 

On the other hand, older fathers tend to have offspring with longer telomeres. Even their grandchildren will have longer than average telomeres. Women, who on the whole life longer than men, have longer telomeres on average than do men.

 

Now, lest you think it is so simple as long telomeres means long life, it is not necessarily so. Mice have very long telomeres, longer than humans, but far shorter life spans. Statistics on likelihood of death in the elderly bear out some factor of telomere length being involved, but probably less than half, with estimates of 37% of the increased mortality of aging being related to telomere length.

 

Nonetheless, despite the unknowns here, there are some takeaway facts.  One is that smoking and alcohol consumption drastically reduce telomere length, which definitely means a shortened life span. These are controllable factors. Prediabetes and obesity are also treatable with proper diet, exercise, and certain specific supplements to aid the metabolism. Chronic infections, especially chronic gum disease has already been associated with increased risk of arteriosclerosis, and no doubt plays a role in telomere shortening. That, too, is treatable. And then, there is our old familiar refrain of “oxidative stress” that we talked about in the newsletter on hydrogen peroxide intravenous treatments.

 

Reducing oxidative stress means avoiding free radicals in things like fried foods, especially in heated polyunsaturated fats. Cigarette smoke is loaded with free radicals. Some of these we can avoid, and for the rest, eating a diet with lots of antioxidants and taking antioxidant vitamins and minerals are important.

 

As you can see, this is fascinating material, and there is much more to learn. Attention is being turned to increased telomerase, perhaps with adult stem cells, or other methods, to protect, or actually restore, telomeres. I predict a great deal of “longevity medicine” or “anti-aging” medicine is going to revolve around this topic of telomeres.

 

Feel free to let me know about topics you might like to explore. There is a recently published retake on an old 1970’s article recently published in British Journal of Medicine that has some interesting re-interpretations about polyunsaturated fats. I could certainly do a newsletter on that. I also want to discuss the much lesser known forms of Vitamin E called tocotrienols, and their association to nonalcoholic fatty liver disease. Also, years ago I published a newsletter on the ORAC values and how they are determined, and which foods have the highest ORAC scores – a high ORAC score means highly anti-oxidant with much protection from free radicals from eating those foods. A repeat review of that information might be timely.

 

Let me know if you have special interests or special questions that I can address. And thank you, so many of you, who have written me to express your appreciation of these newsletters.

 

Alice

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About alicelaule

Physician, dancer, writer, lover of all the arts. A bit of an arm chair philosopher, who hopes with imminent retirement (7/1/11) to be able to get out the armchair and write on philosophy of health care, as well as get back to writing fiction again. Love music of all kinds, but for the last year or so, have been absolutely fanatical about Linkin Park.
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