Telomere length

Telomeres are the protective caps of the chromosomes. Their length is discussed as a possible marker of biological age and is looked at in ageing and cell health diagnostics. Telomeres shorten with each cell division; in studies stress, inflammation, smoking and lack of sleep were associated with shorter telomeres. Measurement requires a blood draw at the practice.

What telomeres do in the cell

Telomeres consist of short DNA sections with the sequence TTAGGG, repeated thousands of times at the ends of every chromosome. A protein complex called shelterin binds to them and folds the end into a loop. In this way the cell does not recognise its chromosome ends as DNA breaks, does not wrongly repair them and does not stick chromosomes together. When DNA is copied before each cell division, the copying enzyme cannot fully reproduce the outermost end. The enzyme telomerase makes up for this loss by adding new repeats using a built-in RNA template; it is active mainly in germ cells, stem cells and activated immune cells, and hardly at all in most body cells.

Short telomeres – what happens in the cell?

When a telomere becomes so short that shelterin can no longer protect it, the cell reports DNA damage. Via the guardian protein p53 it then permanently stops dividing – it becomes senescent – or initiates orderly cell death. Senescent cells often remain in the tissue and release inflammatory messengers and tissue-degrading enzymes. In tissues that renew themselves a great deal, such as blood formation, skin or the gut lining, the supply of new cells can decline. Telomere length is usually measured in white blood cells; in studies shorter telomeres were associated, among other things, with cardiovascular diseases. Rare inherited disorders of telomerase lead to very short telomeres and affect the bone marrow, lungs and liver.

Long telomeres – what does it mean?

Long telomeres mean that the cells still have many divisions ahead of them before the chromosome ends lose their protection. How long the telomeres are is to a large extent already set at birth and is partly inherited; length differs considerably between people of the same age, and in studies women had somewhat longer telomeres than men on average. Longer is not better in every respect, however: in genetic studies, inherited longer telomeres were associated with a slightly higher risk of certain types of cancer, because cells with genetic errors can then divide for longer before the division brake takes effect. Telomere length is therefore one building block among many for describing cell ageing.

The interpretation is given in your report.