Training-induced apoptosis in skeletal muscle.

This research focused on understanding whether physical training induces programmed cell death (known as apoptosis) in skeletal muscle. Such apoptosis might be a mechanism for enhancing fitness because it could lead to the replacement of older muscle cells with stronger, newer ones. The researchers used thoroughbred horses and treadmills in a three-month training programme to study the phenomenon.

Methodology

• The researchers used Thoroughbred horses as the subject of the research. These horses underwent a three-month training programme on a treadmill. This provided a controlled environment to monitor any changes closely.
• At the end of the training, venous blood samples were taken for a creatine kinase (CK) assay, a test to understand muscle damage.
• Muscle biopsy samples were also obtained. These samples were used for two measurements. One was to detect the level of membrane lipid peroxidation by performing a malondialdehyde (MDA) assay. This helped understand the level of oxidative stress in the muscle cells. The second was to detect the presence of apoptotic cells.
• To detect apoptosis, the so-called TUNEL method was used. This method identifies cells where the DNA is in the process of being cut into smaller fragments, as normally happens during apoptosis.
• Finally, the DNA obtained from the biopsies was subjected to 1.5% agarose gel electrophoresis. This is a laboratory method used to visualize DNA fragmentation — a characteristic of apoptosis.

Results

• The research showed a significant increase in the levels of protein-bound MDA, indicating increasing levels of oxidative stress.
• While there was a nonsignificant trend for the control group to have higher levels of CK compared to the trained group, it doesn’t definitively prove no muscle damage in the trained group.
• Under light microscopy, the percentage of TUNEL positive cells (those going through apoptosis) was higher in the trained group. This was confirmed by checking for DNA fragmentation, which also showed higher levels of DNA fragmentation in the same group.

Conclusions

• Based on the results, the study concludes that physical training indeed induces apoptosis in skeletal muscle. The apoptosis might be a way for the body to replace older muscle cells with stronger, newer ones — a mechanism that could underlie training-induced increases in fitness.