Context: Researchers have found out that mutations in Mitochondria result in gradual decline in mitochondrial functions which leads to the death of muscle cells. The death of muscle cells in turn leads to loss of muscle mass.
Relevance of the Topic: Prelims: Key facts about Mitochondria and Age-related muscle loss.
What is Sarcopenia?
- Age-related muscle loss, called sarcopenia, is a natural part of aging.
- After age 30, humans begin to lose muscle mass as much as 3% to 5% per decade.
- Less muscle means greater weakness and less mobility, both of which may increase your risk of falls and fractures.
What are Mitochondria?
- Mitochondria are cellular organelles found in the cytoplasm. They are called powerhouse of the cell as they generate most of the cell's energy currency- ATP (adenosine triphosphate).
- Some DNA is also present in the mitochondria (mtDNA). mtDNA codes for a small number of genes, essential for the proper functioning of mitochondria.
- Mitochondria are the descendants of free-living bacteria that our early single-celled ancestors then absorbed. Today, mitochondria can not survive independently of their host cell.
- Inheritance: mtDNA is inherited almost exclusively from the mother. (Nuclear DNA comes from both parents)
- Mitochondrial DNA is more prone to mutations compared to nuclear DNA as it is exposed to free radicals generated during energy production, which can damage DNA.
- When mitochondria are impaired they do not produce sufficient energy. It causes inherited conditions like heart problems, liver failure, brain disorders, blindness and muscular dystrophy. There is no cure for mitochondrial DNA diseases at present.
Mitochondria and Age-related Muscle Loss
- mtDNA molecules can suffer from age-related deletion mutations. (A deletion mutation is when one to few thousands of base-pairs become deleted from a gene)
- The deletion mutations accumulate in the mitochondrial genome (mtDNA) and can affect the expression of normal mtDNA.
- Over time, this leads to critical shortage of functional mitochondria (those producing ATP) in the muscle cells.
- If the number of functioning mitochondria becomes too low, the muscle cell is unable to properly contract and dies. This underlies the loss of muscle mass.
- Significance: mtDNA deletion mutations are a useful predictor of biological age. A better understanding of the process that causes deletion mutations can help researchers develop new ways to delay age-related decline in mtDNA quality.