“What Causes Aging ?”
Why are the skin old people look wrinkle and old? What causes them look like that? Ageing! Yes, it is caused by a complex interplay. And it is the interplay of 2 different things, gene and environment these two things is the main factor of aging. Some examples for external environment, things like stress, exercise, and infection of disease or internal environment, in our body cells such changes marks on DNA aka changes of Epigenetic and also things like an oxidative stress. Loss cellular fitness and accumulation of the cellular damage is some of the effects of aging over the time. What causes the damage? The compensatory mechanism makes things become good or bad?
Hallmarks of Aging
With aging, there are changes occurs in our cells. According to the scientist, there 10 hallmarks of aging and it can be divided into a few things that will accelerate the aging process. The things are Telomere Shortening, Epigenetic Changes, DNA Damage, defective handling of the protein and the mutation of the Mitochondrial DNA. There are also things that can be good and sometimes can be harmful to our body cells such senescence, nutrient sensing and also the oxidative stress that I have stated above. Ageing of the cells also caused by the things that happen at the outside of the cells, it is the malfunction and the intercellular communication of the stem cell. Let's dive deeper into this.
DNA Damage
Did you know In our cells there is the DNA repair mechanism, the DNA repair mechanism used to repair our DNA inside our cells. This is because the DNA inside our cells is always being damaged and it needs to be repaired to works as usual. When we age, this repair mechanism becomes less effective and the damaged DNA will accumulate in the old tissue. Abnormal Chromosome and the mutation of DNA are more commonly occurs in old humans and also the old animals than young humans and animal. This will accelerate the aging and who are suffering this mutation they will age very quickly than others.
Mitochondrial DNA Mutations
Every cell needs the energy to survive, so all of the cells need the Mitochondria to generate the energy that needed by the cells. The cell ages will become more quickly if the mitochondria don't work properly. In the older cell, the mitochondria also will become less efficient and ATP that generate by Mitochondria will decrease.
Mitochondria are organelles inside each cell that generate the energy needed for the cell to survive. When mitochondria don't work properly, the cell ages more quickly. And mitochondria are less efficient in older cells – they make less ATP (which the cell uses for energy). There will be reactive oxygen species or ROS in the old cells. Examples of the ROS are peroxides, superoxide, hydroxyl radical, and singlet oxygen.
Telomere shortening
Telomeres are located at the end of the chromosome it is a repetitive Nucleotides sequence at the end of the chromosome. The telomeres will protect the DNA from the important DNA being chopped off when the DNA copied, for these reasons the cell can reproduce and divide properly. Some of the telomeres are lost when the cell divided. The old cell will divide more than the younger cell, so the Telomeres of the older cells will become shorter than younger's Telomeres. The normal DNA repair mechanisms cannot repair the Telomeres. This is because the telomeres are protected by the enzymes and the DNA repair protein located in the complex of the protein. The chromosome would fuse together if the telomeres were repaired. It is because the breaks DNA can't be repaired at the same time. So, there is an enzyme called Telomerase, this enzyme will repair the Telomeres. But, unfortunately, Telomerase is not in most cells in adult human. Telomeres are more expose to the age-related damage. This because the Telomeres can't be repaired like the DNA. The cell will die because of the damage to the DNA in the Telomeres. Cell can't divide if there no more Telomeres. The tissue in the body can't regenerate properly and there also high risk to suffer disease like Aplastic Anaemia and Dyskeratosis Congnetia.
Epigenetic Changes
It is reversible marks on the DNA and the DNA sequence will not changes. The epigenetic changes also include the Chromatin Remodeling, DNA Methylation and also the Post-Translation Histone modification. Genome stability and DNA repair will have some problem if the Epigenetic changes happen. The energy and the metabolism production in the cells will change also. These change, Epigenetic changes are easier to alter than the DNA mutation. So, it will be great for the treatment of the anti-aging.
Defective Protein Handling
For your information, in our cell there is protein and it is constantly being recycled. In the recycling process protein that is old and damage was being removed and there will be new protein will replace the old and damage protein. There will be an accumulation of the damaged protein in the cell if the system does not work properly or it does not work. There will be toxic in the cell and it is caused by the damaged protein. This may cause the disease like Alzheimer's and Huntington's.
Nutrient Sensing
To balance the energy produced, stored and used in the cell there is an intricate nutrient sensing system. This system plays their roles as a balancer for a cell and each cell owns this system. It can manipulate aging in an animal model, cells will age more quickly, it can speed up and slow down the aging. Lifespan can be increased by changing the key of the nutrient sensing genes and also the calorie restriction. The animal will die when there no minimal energy required to stay alive.
Oxidative Stress
The byproduct of energy production is produced by the ROS. The ROS will cause the oxidative stress to occurs. Longtime ROS recognized will cause aging, but now it works as a stress signal. The stress signal will offset the stress by turn on the compensatory pathway. But, it can cause cellular damage if the level of ROS going up over their threshold.
Cellular Senescence
When the cell is not divided, the cellular senescence will occur. Cellular senescence will cause DNS damage and Telomere shortening.
Stem Cell Exhaustions
What is Stem Cells? Stem Cells is an immature cell, this immature cells can be divided to generate the adult cells. Many adult cells can be created by one Stem Cell. For this reason, we can see how is important the Stem Cell. It is an important mechanism to regenerate back the damaged tissue and the aged tissue. As we age, stem cell number will decline and it will less efficient to regenerate new tissue that needed by the body.
Altered Intracellular Communication
To communicate with each other in cells and organs, there are many different ways can be used as the medium of the communication. Such as hormones that secrete from a few organs in our body can affect the other organs this process called endocrine signaling. Thanks for reading and let's continue My Biologist's Adventure.
Reference and Further Reading
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