The genetic information of all organisms is contained within the chromosomes making them the source of our organizational patterns like color, health, behavior and so on. Each chromosome in our body is buffered by the presence of structures at either of its ends made of protein-DNA complexes called telomeres. These telomeres protect the genome from being degraded nucleolytically; prevent them from getting fused with other chromosomes or recombination processes. In general terms, they protect the genome from undue erosion. The telomeres are therefore key to the preservation of our genetic code and can not be done away with. According to the normal physiological process, in each cellular division a little portion of DNA from the telomeres is lost as well. Beyond a threshold point of the telomeric length, the cells undergo orchestrated death through apoptosis. The length of the telomere therefore may act as an indicator that determines the cell or organism lifespan. Various agents that we encounter through our lifestyle may lack the shortening of the telomeres. These agents could cause damage to the DNA or directly affects the telomeres thereby modulating the general health and / or the lifespan of the individual. Therefore, there are factors that can accelerate the telomere shortening and interfere with healthy life and aging. Efforts are now being focused on decelerating this process and reverse the associated phenomenon of aging and related disorders.
Variability of the telomere length
Although the general notification is that the telomere length varies according to the age of the individual, there are high degrees of variation of the telomere length even among individuals of similar age. Existing reports suggest that the telomere length is determined genetically and that inheritance accounts for this variation in (40-80)% of the cases. According to the work of Okuda and his group it was observed that the lengths of telomeres from the DNA samples of neonatal showed significant synchronization that were isolated from umbilical artery, WBCs and skin. However, this was not the case with the telomere lengths of different newborns which seemed to vary to a great extent. The synchronization that was observed within the tissues of neonatals are lost and become more heterogeneous in the aged individuals. There are also literatures available which suggest that the length of the telomere varies between people from different ethnic background. The telomere lengths in African Americans are longer than those of the Caucasians while no significant difference between the telomere lengths was observed from the newborns of the two races. It was also significant that the adult women possess longer telomeres than their male counterparts. Women also show a lower rate of shortening of the telomere. A cue to this may be found from the study that estrogen stimulates telomerase activity. Significant association between estrogen levels and the activity of telomerase have been established. Misiti et al. have suggested that estrogen is also effective in up-regulating the gene expression of telomerase besides its activity.
Stress can affect telomeres
Besides the genetic factors in the determination of telomere length, exposure to varied environmental factors has a significant role to play in it. The telomeres due to their genetic make up show a high degree of sensitivity to oxidation induced stress. Such is the impact of the oxidative stress on telomere length that it has now been accepted that it causes greater damage to telomeres than even the cell division process. Increase in lifestyle related psychological stress enhancers oxidative stress that results in decreased telomerase activity and accelerated telomere attrition. Studies have revealed that the exposure to stress for longer duration of time can result in the reduced activity of telomerase that in turn pastens telomere shortening in cells of both endothelial or smooth muscle origin. Accordingly, it has been demonstrated that the intake of anti-oxidants causes the enhancement in telomerase activity with a concomitant reduced telomere shortening. An increase in the level of LDL oxidation has been linked to the leucocytes with shorter lengthened telomeres stiffening the artery.
Other environmental factors and length of telomeres
Evidences have been put forward that suggest that infection contributes to a large extent in the shortening of telomeres in immune system cells through the promotion of leucocytes. The telomere length has been negatively affected by the increase in the levels of some cytokines like C-reactive protein (CRP) and IL-6. It has even been observed that during childhood, illness of chronic nature and adverse events of life are linked to the formation of short telomeres at an early age. Smoking results in an increase in the inflammatory responses through oxidative stress and a consequent shorter lengthened telomere. Female smokers are more at risk of eroding the telomeres early. Smoking stimulates the telomere shortening according to a concentration gradient; more the smoking, more is the shortening of telomere. Good habits of physical exercises relating to improvements in telomeres in adults as also in the adolescents thereby suggesting its association with anti-aging process. Intake of marine foods rich in ω-fatty acids also positively influences telomeres. Cherkas and colleagues recently added to this growing list and stated that the socioeconomic status of the individuals can have an impact on the length of telomeres.
Mechanisms to lengthen telomeres
The main function of the telomeres is to support DNA erosion from the ends of chromosomes during replication thereby buffering the process. The enzymes involved in the replication process (DNA polymerases) are able to copy the entire template as a result with each cell cycle a length of the chromosomal end is not copied and is lost forever. However, in order to prevent this incomplete genome replication and DNA loss, the organizations have evolved different mechanisms. The majority of the organisms make use of the retro-transcriptase, telomerase to lengthen their telomeres. However, it has been found that organizations that are deficient in telomerase activity have devised other alternatives to protect and lengthen their telomeres by processes known as Alternative lengthening of Telomere (ALT). In some organizations, the RecQ helicase is required for ALT. In addition, the removal of Mismatch Repair Pathway can cause an increase in ALT process.
Therefore the telomere length is crucial in maintenance of our health and lifespan. On the other hand, the telomerase activity is absolutely necessary to lengthen the telomeres and keep us healthy and prolong our lives. With our lifestyle we expose ourselves to increased levels of oxidative stress that interferees with telomerase activity and accelerates telomere shortening. Therefore, the intake of supplements that can stimulate the telomerase activity can be quite beneficial in maintaining our health and acting as anti-aging factors. The administration of anti-oxidants could help in this regard by enhancing the activity of the telomerase which in part explains their effectiveness as age reversing agents.