[Size=4]About telomeres in general
What are chromosomes?[/size]
Chromosomes are highly condensed rods of Deoxyribonucleic Acid (DNA), the genetic material which contains the building blocks of life. DNA carries a specific code that gives instructions to our body on how to grow, develop and function. The instructions are organized into units called genes. Chromosomes serve as the storage for this important material, periodically dividing along with cells and replicating to make copies of the DNA they contain. Chromosomes are also very important in sexual reproduction, as they allow an organism to pass genetic material on to descendants.
In organisms with cell nuclei, known as eukaryotes, chromosomes are found inside the nucleus. Most of these organisms have a set of chromosomes which come in pairs. In structural cells, each cell retains a complete set of chromosomes, in what is known as diploid form, referring to the fact that the chromosome set is complete. In cells for sexual reproduction like eggs or sperm, each cell only has half of the parent organism’s genetic material, stored in haploid form, ensuring that the parent passes down half of its genes.
What are telomeres?
Telomeres are the ends of chromosomes, which have an essential role in protecting their integrity. They are analogous to the plastic caps at the end of shoe laces which keep the laces from unraveling.
Telomeres are formed by tandem repeats of a DNA sequence, which is conserved throughout evolution (TTAGGG in vertebrates) and associated proteins (the so-called telomere-binding proteins or “shelterins”). The function of telomeres is to protect chromosome ends from DNA repair and degradation activities, therefore, ensuring the proper functionality and viability of cells.
[Size=4]What is telomerase?[/size]
Telomerase is an enzyme which is able to maintain telomeres and repair short telomeres by re-elongating them. To this end, telomerase add telomeric repeats de novo to the chromosome ends. In non-pathological conditions telomerase is expressed associated to pluripotency (early stages of embryo development), as well as in certain adult stem cell compartments. Telomerase is also highly expressed in pathological conditions, such as cancer, where it sustains the immortal growth of cancer cells. Healthy cells usually produce little or no telomerase and, as a consequence of this, they progressively shorten their telomeres associated to successive cycles of cell division, until they reach a critically short length which triggers cell death or an irreversible cell arrest known as replicative senescence (also known as the Hayflick limit).
[Size=4]Why are telomeres important?[/size]
The length of telomeres at a given age is one of the best molecular markers of the degree of aging of an organism and therefore can be used to estimate the biological age of an organism. Telomeres are progressively eroded with increasing organismal age as the consequence of cumulative cycles of cell division to regenerate tissues. This occurs both in differentiated cells as well as in the stem cell compartments, and has been demonstrated to impair the ability of stem cells to regenerate tissues when needed. There is strong genetic evidence from genetically modified mouse models that demonstrates that accumulation of critically short telomeres is sufficient to cause organismal aging and that interventions that decrease the rate of telomere shortening with age, such as forced expression of the telomere-synthetizing enzyme telomerase, is also sufficient to delay aging and increase longevity.
Thus, therapeutic strategies based on telomerase activation are envisioned as potentially important for the treatment or cure of age-related diseases.
Telomeres and telomerase are also relevant for cancer biology. More than 95% of all types of tumors activate telomerase during their formation in order to achieve immortality. Telomerase is, therefore, considered necessary to sustain cancer growth. Therapies aimed to inhibit telomerase activity are currently tested in clinical trials of various types of human tumors.
What is the difference between average telomere length and short telomeres and why is this important?
Telomere length is heterogeneous within a single cell nucleus, so that each chromosome end has a different length of telomeric repeats (there are 4 telomeres per chromosome and 23 pairs of chromosomes per cell). Average telomere length is the mean length of all telomeres considered together, usually within a population of cells (not even per individual cell). However, scientific evidence shows that it is the short telomeres that are responsible for causing aging and disease. This is because critically short telomeres inflict permanent and deleterious damage to the cell, unless they are repaired by telomerase. Therefore, to be able to evaluate whether telomeres are prematurely short for a given chronological age is necessary to use techniques that allow quantification of the abundance of short telomeres. Just measuring average telomere length of a population of cells is not sufficient to “identify” premature telomere shortening. The technology commercialized by Life Length is based on its ability to measure the percentage of critically short telomeres.
What is the relationship between biological age and chronological age that we can learn from our telomeres?
Not all individuals age at the same speed even though they may have the same chronological age. Therefore, it is important to have molecular markers (other than chronological age) that can estimate the degree of aging of an organism. This information may be useful for health professionals to anticipate premature development of certain age-related diseases and to try to minimize this risk with a change life style (obesity, smoking have been shown to lead to accelerated telomere loss), to follow more closely our telomere dynamics over the years, or to benefit from potential telomere activators. Mounting evidence suggests that the length of telomeres is a good indicator of the degree of aging of an organism.
[Size=4]Do we know what the standard telomere length is by age? What is normal?[/size]
What are the factors that affect the length of my telomeres?
Does a greater biological age than chronological age indicate that the individual has the risks and risk factor associated with their biological age?
[Size=4]Why do I need to know my biological age?[/size]
First, it is an excellent indicator of overall general health. Second, by knowing our biological age, it permits us to obtain a better understanding of the life-style habits that impact aging and affords us the opportunity to make appropriate changes. Third, as physicians and the medical community become more comfortable with Life Length’s telomere measuring, it will allow for more personalized medicine as doctors treat patients increasingly taking into consideration their biological age.
