Effects of Aging on the Brain: The Cycle of Life

Every organism that comes into existence goes through a cycle which begins with birth, continues through development, and always ends with death. Regardless of the organism, it seems that aging and death has been largely determined by genetics and the genetic alterations that occur within a life-span. According to the Brain Research Centre, several biochemical pathways are involved in the aging process, which “include those that govern DNA repair, control the death and survival of individual cells in a process called apoptosis, control the functions of mitochondria in cells, regulate the organism’s response to oxidative stress, and govern metabolic consequences of glucose intake.”

Our genetic coding is important in regulating metabolic functions, controlling what genes are expressed, determining cell death, and managing other functions within the body. Of these functions, cell death plays a major role in aging. For people older than 60, it has been found that those with shorter telomeres have are three times more likely to die from heart disease and eight times more likely to die from infectious disease.

One major change that occurs in the body during aging is the cell death, and scientists have hypothesized that cell death, or apoptosis, is controlled by telomeres. Telomeres are repetitive sequences at the ends of chromosomal DNA that help protect the chromosome from deterioration. During cell division, the enzymes that duplicate the DNA are unable to copy the DNA all the way to the end; therefore, cell replication always causes a shortening of DNA. Once the DNA is shortened to a certain degree, the cell can no longer divide and can lead to cell death, or apoptosis. Apoptosis is programmed to prevent further replication of any damaged DNA in order to ensure that cell replication is done accurately (inaccurately replicating DNA can cause abnormal tumor growth and cancer).

Because DNA replication results in a chromosomal shortening, an enzyme known as telomerase utilizes the mechanism of reverse transcriptase to lengthen the repetitive ends and protect the chromosome from damage. Some research has also been done to see whether or not telomerase activity could “immortalize” human cells and extend human life. Dr. Richard Cawthon, a researcher at the University of Utah’s School of Medicine, did a study and confirmed that people with longer telomeres lived five years longer than people with shorter telomeres and believes that the human lifespan can be extended by ten to thirty years if telomere shortening was completely stopped. Cawthon’s study proves that exercise and a healthy lifestyle are not the only factors that can affect life span but that genetic factors play a major role in the average life expectancy.