Telomere is a biomarker of cellular aging.
What's a telomere?
A telomere is the end of a chromosome. Telomeres are made of repetitive sequences of non-coding DNA that protect the chromosome from damage.
In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division, however, and when they reach a critical length the cell stops dividing or dies.
Telomere length shortens with age. The progressive shortening of telomeres leads to aging, cell death, or cancer cell transformation, affecting the health and lifespan of an individual. Shorter telomeres have been associated with increased incidence of diseases and poor survival.
Telomere shortening and aging
Shortening of telomere length is a hallmark of cellular senescence. One of the most important theories about aging is telomere theory, which is based on the mechanisms of telomeres shortening and demonstrates telomeres as a rather elegant biomarker of cellular aging.
Telomere length, how to maintain?
The rate of telomere shortening can be either increased or decreased by specific lifestyle factors. Lifestyle factors such as an unhealthy diet, physical inactivity, or smoking habits have been related to shorter telomere length.
Factors related to telomere shortening
Smoking increases oxidative stress, expedites telomere shortening, and may increase the pace of the aging process.
A study conducted in women indicates that telomeric DNA is lost at an average rate of ‘25.7–27.7 base pairs per year and with daily smoking of each pack of cigarettes, an additional ‘5 base pairs’ is lost. Therefore, the telomere attrition caused by smoking one pack of cigarettes a day for a period of 40 years is equivalent to 7.4 years of life.
Obesity is also associated with increased oxidative stress and DNA damage. Waist circumference and BMI significantly correlate with the elevated plasma and urinary levels of reactive oxygen species. Oxidative stress can induce DNA damage and may therefore expedite telomere shortening.
Telomeres in obese women have been shown to be significantly shorter than those in lean women of the same age group. The excessive loss of telomeres in obese individuals was calculated to be equivalent to 8.8 years of life, an effect that seems to be worse than smoking.
Unhealthy dietary habits
Unhealthy dietary habits also have been linked to an inflammatory state, contributing to progressive telomere attrition.
Exposure to genotoxic agents, which may induce damage to DNA in general or more extensively at telomeres, can increase cancer risk and the pace of aging.
Exposure to pollution such as toluene and benzene. The investigators found that telomere length in traffic police officers was shorter, relative to telomere length in office workers.
Stress hormones have been shown to reduce the levels of antioxidant proteins and may cause increased oxidative damage to DNA and accelerated telomere shortening.
Women, exposed to stress in their daily life, had evidence of increased oxidative pressure, reduced telomerase activity, and shorter telomeres, relative to the women in the control group. The difference in telomere length in these two groups of women was equivalent to 10 years of life.
Several studies suggest that reducing sugary beverage consumption could be associated with extended telomere length.
Factors that may preserve telomere length
Eat more fibers
Telomere length positively correlated with dietary intake of fiber and negatively associated with waist circumference and dietary intake of polyunsaturated fatty acids, especially linoleic acid.
The “prudent dietary pattern” (whole grains, fish and seafood, legumes, vegetables, and seaweed) was found to be positively associated with telomere length while an inverse trend was found in the “western dietary pattern”.
Mediterranean diet (high intake of vegetables, legumes, nuts, fruits, a moderate intake of fish; a low intake of saturated lipids but high intake of unsaturated lipids, particularly olive oil; a regular but moderate intake of alcohol, specifically wine) has been shown to prevent age-associated telomere shortening.
In animal models, calorie restriction has been shown to have a positive effect on telomere length and to globally delay the onset of aging and age-related disease such as diabetes, cardiovascular diseases, various neurological disorders, cancer, and obesity, possibly via a reduction in oxidative stress.
In humans, the data are less convincing, probably because decreasing the caloric intake by a third or a half is very challenging in that population, certainly in the long term practically.
A recent study indicated that moderate amounts of exercise are sufficient to protect telomere health, The young athlete had longer telomeres than their inactive peers. Telomere length was 11% higher in ultra-marathon runners compared to 56 healthy subjects, matched for age.
A diet containing antioxidant omega-3 fatty acids is associated with a reduced rate of telomere shortening, whereas a lack of these antioxidants correlates with an increased rate of telomere attrition in study participants. Antioxidants can potentially protect telomeric DNA from oxidative damage caused by extrinsic and intrinsic DNA damaging agents.
The research found that women who consumed a diet lacking antioxidants had shorter telomeres and a moderate risk for the development of breast cancer, whereas the consumption of a diet rich in antioxidants such as vitamin E, vitamin C, and beta-carotene was associated with longer telomeres and lower risk of breast cancer.
The latest research about telomere length extension
"Turning back the internal clock"
Researchers delivered a modified RNA that encodes a telomere-extending protein to cultured human cells this method can lengthen human telomeres by as much as 1,000 nucleotides, turning back the internal clock in these cells by the equivalent of many years of human life, This new approach paves the way toward preventing or treating diseases of aging.