A treadmill exercise regimen for identifying cardiovascular phenotypes in transgenic mice

Area of Science:

• Cardiovascular physiology
• Exercise science
• Animal models in research

Background:

• Treadmill exercise is crucial for detecting latent cardiac abnormalities.
• Assessing cardiac performance and metabolic data in mice requires non-invasive methods.
• Genetic manipulation of cardiac proteins can lead to subtle functional changes.

Purpose of the Study:

• To describe a novel treadmill exercise protocol for mice.
• To quantify animal performance and gather metabolic data non-invasively.
• To evaluate the effects of a specific genetic modification on cardiac function during exercise.

Main Methods:

• Development of a non-restraining treadmill exercise protocol for mice.
• Utilizing telemetry implant devices for metabolic monitoring.
• Subjecting transgenic (TG) mice overexpressing ventricular myosin regulatory light chain (MLC2v) and nontransgenic (NTG) littermates to a 5-week exercise regimen.

Main Results:

• TG mice exhibited significantly decreased exercise capacity at higher treadmill speeds compared to NTG mice.
• No evidence of cardiac hypertrophy was observed in either TG or NTG mice post-exercise.
• Exercise did not affect MLC2v phosphorylation levels.
• Ultrastructural analysis revealed a proliferation of the transverse-axial tubular system in TG atrial tissue.

Conclusions:

• The developed treadmill exercise protocol is effective for detecting subtle cardiac phenotypes in genetically modified mice.
• Overexpression of MLC2v in TG mice leads to impaired exercise capacity without inducing hypertrophy.
• The proliferation of the transverse-axial tubular system in TG atria may contribute to altered cardiac function.