Mitochondria – the secret behind aging?

Mitochondria are the power plants in our cells. They are responsible for the production of most of energy, in the form of ATP (Adenosine Triphosphate).
They are complex organelles (small structures that are parts of each cell, just like the organs are parts of our body), that live a life of symbiosis with their cell. Depending on the cell type and the energy requirements the number of mitochondria varies. Neurons (nerve cells) and myocytes (muscle cells) might have thousands of them. They seem to have an important role in the longevity of a cell, and the better the mitochondria are doing, the better your cells are doing. More about that a little later. First some good stuff to know:

The mitochondria are most likely bacteria, or prokaryotes, that developed an endosymbiotic (that is they are living in their symbiotic partner) relationship with eukaryotic cells (all our cells). There are features in the mitochondria, such as a circular genome and some structural elements, that resemble those of bacteria.
The mitochondria has a DNA of it’s own and is inherited maternally, that is, all the genes come from the egg. This is an exception from the rule that we get half of our genes from each of our parents. Since the genome isn’t mixed and there is little possibility for the existing genes to recombine with each other. It makes it possible for scientists to study evolutionary history for populations.
Even though it has it’s own DNA, it still needs the cell nucleus to make some of it’s proteins to function properly and that’s where the symbiosis comes in.

To make ATP the mitochondria uses two processes: The citric acid cycle and The Electron Transport Chain. Fats, proteins and carbohydrates are broken down Acetyl-CoA that is fed into the Citric Acid Cycle, generating ATP, FDAH, NADH and CO2. The process requires oxygen.
The NADH and FDHA are then fed into the Electron Transport Chain where they give away their hydrogen. The accumulation of hydrogen creates a chemical gradient and their energy is used to create ATP from ADP (Adenosine Triphosphate).

The mitochondria carry out a couple of other important functions as well:

  • Regulation of cell metabolism.
  • Executing apoptosis – controlled cell death.
  • Regulating cell maturation and division – probably through the regulation of available energy.
  • Production of steroidal hormones.
  • Heat production in brown fat. Here the use of the proton chemical gradient is not coupled to ATP production, instead the energy is released as heat.
  • Redox reactions, meaning reversing the oxidative stress that the making of ATP gives rise to. More about that below.

Since oxygen is used in the Citric Acid Cycle and there is a large amount of protons (the nuclei of hydrogen atoms) in the Electron Transport Chain these processes will give raise to Reactive Oxygen Species, or ROS. These are potentially dangerous for the cell, since they can react with DNA, proteins and fats and through that destroy their structure and make them dysfunctional. Enzymes and many cell structures are proteins and the cell wall and the walls of the mitochondria are made of fats. Imagine these structures being damaged by ROS and non-functional. That means that mutations in the DNA can occur and the cell and mitochondrial walls becomes leaky. Because the reactions are closer to it, there is usually more damage to the mitochondrial DNA than to the DNA in the nucleus.
The ROS can also affect the telomeres, the little end-caps on our chromosomes that gets shortened with every cell division and and are associated with aging. When they are shortened some genes that produces proteins important for mitochondrial survival are turned off and they become dysfunctional.

To balance this there are anti-oxidants, proteins that take up the protons and deliver them to a safe place where they can be used properly. Co-enzyme Q10 (CoQ10), glutathion, SuperOxide Dismutase (SOD), Vitamin E and C are a couple of important players.

Eating a ketogenic diet seems to be a more “clean” way of fueling your body, because using ketones instead of glucose give rise to less ROS. The ketones them selves seems to have a positive effect on the mitochondria and give them the right signals to duplicate and thrive. So lowering blood sugar and raising ketones through a low carb high fat diet might be a pretty easy way of keeping aging, especially for the brain, in check! Great news, isn’t it!

More reading:
http://www.drperlmutter.com/keep-ketosis/
http://hplusmagazine.com/2011/10/21/the-mitochondrial-theory-of-aging/
http://www.psychologytoday.com/blog/evolutionary-psychiatry/201104/your-brain-ketones
http://www.ncbi.nlm.nih.gov/pubmed/17240074

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