The telomere test for approximation of your biological age has been getting some press lately, so I thought I’d research it a bit and make it the topic for June’s NWTC “What’s Cooking” newsletter.
I’ve been interested in telomeres for a few years because of their relationship to aging.
Have you checked your telomeres lately? Do you need to? What the heck are telomeres?
There is a new test that you will soon encounter in the mass market media. The advertisement will read something like, “How much longer will you live,” or maybe, “Find out when you’re supposed to die.” Or, perhaps it will be more positively framed as something like, “Find out your biological age, and how to prolong it.” The test will require a blood sample (possibly saliva) and a payment of about $300, give or take. I’m guessing that the additional information, regarding the prolongation part, will be extra, likely having to do with daily supplements, specialty foods or other allegedly crucial interventions.
The telomere test is a provocative melding of actual science and the various human emotions in orbit around the all-too-real planet of our individual mortality. You have to admit that each of us has, at least to some extent, a morbid curiosity of if not the actual end-of-days, at least our own end-of-day; and, the desire to somehow impact it. This is what some selling the telomere test will promise—a calculation of your biological age, and how to prolong it…by taking vitamins, increasing physical activity, avoiding weight gain or obesity, and correcting insulin resistance (diabetes).
Telomeres are like protective caps on the end of chromosomes, and when the wear out, cells stop dividing and eventually die; so, long telomeres are good and short ones are less good, unless you’re 120 years-old, in which case short ones are expected; or so the argument goes. Of course, it’s not that simple, or predictable for a host of reasons. Let me explain.
You have 23 pairs of chromosomes (46 total) in each cell in your body. Each chromosome is made of your DNA that is specific to you alone in all the universe, unless you’re an identical twin. DeoxyRiboNucleic Acid is kind of like a zipper in that it is made of two matching molecular strands that can unzip and divide into two so that proteins in the cell can assemble new, matching strands so that where there was one, there now are two. This works because each zipper strand has four different kinds of teeth (nucleotide base pairs) call them A, C, G, and T. Each tooth will match up with only one other: G with C, and A with T. And it is the specific sequence of the base pairs that encodes specific genes, like blond hair and blue eyes, or risk of colon and breast cancer. Some genes might have only a few base-pairs, and others, thousands.
23 pairs, 4 different kinds of nucleotides, only two matching pairs—doesn’t sound like big numbers; but, each chromosome can contain up to 10 billion base pairs in a twisted tangled chain. 46 invisible threads in an invisible nucleus in an invisible cell that tell us what we are, if not who. Pretty amazing stuff; and all supposedly arising from a lightning bolt striking a primordial soup long ago; or God—it’s your choice.
The problem with cell division is every time the DNA unzips you lose 30-150 base-pairs off the ends. It’s called “the end replication problem.” Since the telomeres serve as the protective caps, losing a hundred pairs is no big deal—the gene sequences remain safe on the inside as the telomere sacrifices a little bit of itself. The telomeres have about 10,000 base pairs, which comes to 66.6 (10,000/150) cell divisions before they wear out and die.
The age-related diseases; cancer, diabetes, atherosclerosis and heart failure have all been associated with shorter telomere length; as are also obesity and smoking. The question is, do short telomeres cause all this bad stuff; or, does all this bad stuff cause shorter telomeres?
In these studies of associations, and the telomere test itself, it is the White Blood Cell (WBC) whose telomere is being measured. All of our other cells (brain, heart, etc.) have telomeres too, which are widely variable at birth and across population groups; but, they are much harder to sample for obvious reasons, as opposed to a finger stick for a tiny drop of blood. Perhaps the WBC telomeres are more a marker of inflammation, which is the root cause of the metabolic syndrome, diabetes, heart disease, and many types of cancer. Perhaps the telomere test is more a marker of lifestyle choices, the results of which should be no surprise, than it is of longevity.
I don’t think the telomere test is ready for prime time. There are too many variables and too many assumptions; and more importantly, what will it tell you that you don’t already know: that you should stop smoking, lose weight, and control your blood sugars if diabetic? Well, let me say it then. Stop smoking, lose weight, and control your blood sugar. That will be $300 please, and you didn’t even have to give me a blood sample.
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The nucleotides in DNA are; Adenine, Cytosine, Guanine, and Thymine; A, C, G, and T; and in humans, the telomere is made of repeating sequences of TTAGGG repeats for a total telomere length of 8-15 kilobase (kb) pairs, or 8-15,000 base pairs. This sequence is shared with mice, rats, and birds; and slime mold has an extra “T” (TTTAGGG). Hmmm…I wonder if there’s slime mold in primordial soup.
The cells in our bodies are called somatic cells; they have differentiated from stem cells into specific cell types; and as such, suffer from mortality, being good for about 50-70 divisions before cell senescence or apoptosis, which basically means cell death or disintegration. In contrast, embryonic stem cells are as immortal as a cell can be in that it has high levels of a protein complex, called telomerase, which can rebuild telomeres; so, in the stem cell, the telomeres don’t wear out. Some cancer cells also have high levels of telomerase, which is a factor in a tumors relentless growth.
Most of the studies drawing age-related associations have been with the telomere length of WBCs, which may be a more accurate measurement of the inflammatory state. The telomere lengths of various organs are widely variable from person to person, and from organ to organ within an individual. Do those individuals with shorter telomeres at birth of the heart cells have a shorter life span than those of an individual with longer ones? Do people that die at a young age from illness have shorter telomeres than age-matched controls?
I think the telomere is a factor in aging, and potentially, eventually, subject to interpretation and intervention for longevity; but at this time the test result is, I think, nothing more than a curious novelty, no more accurate than having your palm read at a carnival.