What does telomerase do to the length of your telomeres?
Telomerase keeps telomeres intact for longer by compensating for shortening during cell division, but in most body cells the enzyme is barely active, causing telomeres to shrink over time.
Telomerase is an enzyme that replenishes the ends of chromosomes, the telomeres, with each cell division. It continuously attaches new pieces of DNA (the sequence TTAGGG) to those ends. Without this enzyme, telomeres become slightly shorter with every cell division, until the cell stops dividing. That process is regarded as a biological ageing clock.
In most ordinary body cells, telomerase is barely active after the early embryonic phase. As a result, those cells become exhausted with repeated division: the telomeres grow too short, the cell enters a kind of dormant state (senescence) and no longer divides. Stem cells and germ cells are an exception; these keep telomerase active for longer.
Telomerase does not operate without regulation either. Specific proteins on the telomeres determine when the enzyme gains access. The shortest telomeres take priority: they are replenished first. In this way the system maintains a balance and the telomere does not grow indefinitely.
There is an important downside. In most cancer cells, telomerase becomes active again, allowing those cells to keep dividing without limit. Telomere shortening in healthy cells acts precisely as a brake: a cell that has divided too many times simply stops. That brake also restrains tumour formation.
When telomerase does not function properly due to an inherited mutation, so-called telomeropathies arise. These are conditions in which telomeres wear down structurally too quickly, with serious consequences for tissues that require a great deal of cell division, such as bone marrow and lungs. This shows how essential a properly functioning telomerase system is.
All claims are based on multiple studies (PMIDs 24993696, 18432920, 16741708, 21429730, 29415479, 9524748, 40609992). The mechanistic and cellular findings are robust; the role in male fertility is insufficiently supported and has not been included as a conclusion.
Why do your telomeres get shorter as you age?
Telomeres shorten because the copying process during cell division cannot fully reproduce the ends of chromosomes, and the repair enzyme telomerase is switched off in adult body cells. Stress and oxidative damage can accelerate that process further, but the fundamental mechanism is unavoidable as long as cells divide.
Can you lengthen or restore your telomeres?
Healthy adult body cells cannot lengthen their own telomeres, and no proven safe way to do so from the outside yet exists. Be sceptical of supplements or therapies that promise otherwise.
How do telomeres protect your DNA?
Telomeres protect your chromosome ends through a system of proteins that simultaneously prevents false alarms and harmful fusions. If that system fails due to inherited defects, you can develop serious ageing-related diseases.
What exactly does senescence do to your cells as you age?
Senescent cells stop dividing and secrete inflammatory substances that damage tissues over time. They are necessary in youth, but when they accumulate they accelerate ageing and disease.
What are telomeres and can I keep them longer?
A healthy lifestyle, regular exercise, stress reduction and adequate vitamin D appear to slow telomere shortening, but anyone looking for a quick fix will not find one: the science is not there yet.
Does your telomere length tell you anything useful about your health?
Telomere length is a relevant biological measure, but does not give a clear-cut signal: shorter telomeres increase the risk of heart disease and fibrosis, while longer telomeres increase the risk of certain cancers. A commercial telomere test in blood is therefore difficult to translate into concrete health advice.