The muscle cells of a trained athlete tend to have more mitochondria than those of a couch potato. Why?
The reason why the muscle cells of a trained athlete tend to have more mitochondria compared to those of a couch potato is due to a process called mitochondrial biogenesis. Mitochondria are the powerhouse of the cell, responsible for producing energy in the form of ATP. Mitochondrial biogenesis is the process through which new mitochondria are created within cells.
When someone engages in regular exercise and trains their muscles, the demand for energy increases. To meet this increased demand, their muscle cells undergo adaptations to become more efficient in producing ATP. One of these adaptations is an increase in mitochondrial density.
During exercise, the muscles experience oxidative stress, which triggers a series of cellular signaling pathways. These pathways lead to the activation of certain genes and transcription factors involved in mitochondrial biogenesis. The expression of these genes stimulates the production of new mitochondria.
Regular exercise also increases the activity of AMP-activated protein kinase (AMPK), which plays a crucial role in regulating energy metabolism. AMPK activates various signaling pathways that promote mitochondrial biogenesis. It stimulates the activation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), a key regulator of mitochondrial biogenesis.
PGC-1α then binds to and activates various transcription factors involved in mitochondrial biogenesis, such as nuclear respiratory factors 1 and 2 (NRF1 and NRF2) and mitochondrial transcription factor A (TFAM). These transcription factors promote the expression of genes responsible for mitochondrial replication, maintenance, and function.
As a result of regular exercise and increased demand for ATP, these signaling pathways and transcription factors work together to induce the production of new mitochondria. Over time, this leads to an increase in mitochondrial density in the muscle cells of trained athletes.
It's worth noting that while mitochondrial biogenesis is a significant factor, other factors such as genetic predisposition, dietary habits, and overall lifestyle choices can also influence the number of mitochondria in muscle cells.