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.

Resources:

1. http://learn.genetics.utah.edu/content/begin/traits/telomeres/

2. http://www.brain.ubc.ca/TheAgingBrain.php

3. http://www.scientificamerican.com/article.cfm?id=anti-aging-pill-targets-telomeres

Sweet Tooth or Sweet Brain?

As we all know, an uncontrolled diet high in sugars and fats can have noticeable effects on weight, provide insufficient nutrients for the body, and increase the risk of diabetes. However, few people realize that rising glucose levels in the body may also affect the function of vital organs, such as the pancreas and, especially, the brain.

Approximately 120 grams of glucose are needed by the brain in a single day, most of which is generated via gluconeogenesis from non-sugar molecules within the body. Although glucose is a necessary component for the normal functioning of the brain, it has also been proven that an excess could cause damage to the brain itself and decrease cognitive decline. According to a study conducted by Dr. Scott A. Small, associate professor of neurology in the Sergievsky Center and in the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at Columbia University Medical Center, glucose specifically targets the dentate gyrus within the hippocampus, decreasing activity in that region of the brain. Because high blood glucose levels damage the part of the brain that controls memory and learning, which suggests that it may play a major role in Alzheimer’s disease and dementia.

Since the brain is constantly firing neurons, it requires about two times more glucose than other cells within the body. However, neurons cannot store glucose, so they depend on the bloodstream to deliver a constant supply glucose to fuel the brain. Because of this, physical exercise, which helps reduce blood glucose level, can help to lower glucose levels in the dentate gyrus and enhance cognitive function. Once again, it seems pretty obvious that exercise plays a huge role in the process of aging—physically and mentally.

Resources:

1. http://www.washingtonpost.com/wp-dyn/content/article/2008/12/30/AR2008123000993.html

2. http://www.cumc.columbia.edu/news/press_releases/081230_Aging.html

3. http://brainfuels.com/2010/03/toxic-glycolysis-and-brain-aging/