Longevity Word of the Week: Mitophagy - Part 1

Written by Anil Bajnath, MD
Posted November 23, 2021

Dear Longevity Insider,

The longevity word for this week is mitophagy.

The word “mitophagy” was coined in 2007 by the researchers who discovered this process. The prefix "mit-" means "thread" and "phage" means "eat." So we define mitophagy as the destruction of mitochondria via a cellular mechanism called autophagy. Autophagy is a process that involves the degradation and recycling of cellular components.

Mitophagy is the selective kind of autophagy mechanism that removes mitochondria.  A cell can digest its own organelles through this process, but it will only remove damaged structures and not healthy structures. This selective quality is what makes mitophagy so unique because most other forms of autophagy just degrade cellular components indiscriminately.

There are two other forms of autophagy: chaperone-mediated autophagy and micropexophagy.

  1. Chaperone-mediated autophagy is a process that degrades damaged proteins. (This type of degradation occurs in the lysosome or sac-like structure.) 
  2. Micropexophagy, on the other hand, targets  mitochondria for degradation.

Mitophagy and Mitochondria

The mitochondria is an organelle that is responsible for converting energy into a form of molecules that our cells can use. Inside the mitochondria are enzymes called electron transport chains (ETCs), which take electrons and try to pair them with hydrogen atoms to produce chemical energy. This process also creates free radicals as by-products, so our cells must have an enzyme called superoxide. Superoxide dismutase (SOD) eliminates superoxides and turns them into hydrogen peroxide. Hydrogen peroxide (H2O2) is broken down by catalase and glutathione peroxidase into water and oxygen gas.

This cellular structure is responsible for helping generate adenosine triphosphate (ATP), which stores energy in the form of phosphate bonds. Cells need ATP to get rid of excess calcium ions that build up due to metabolism, and also to open up calcium ion channels for muscle contraction.

The severing of the mitochondria from the rest of a cell triggers apoptosis, which is a programmed form of cellular death. The lack of a link to other organelles and its proximity to calcium ions makes it susceptible to damage. Because of this susceptibility, cells have developed a mechanism which allows them to dispose of defective mitochondria.

But that's not the only thing autophagy allows these cells to dispose of...

To your longevity,

Anil Bajnath MD
CEO/Founder, Institute for Human Optimization
Chief Medical Officer, Longevity Insider HQ