Thyroid hormone regulates muscle function during cold acclimation in zebrafish (Danio rerio).

Area of Science:

• Comparative physiology
• Endocrinology
• Aquatic animal science

Background:

• Thyroid hormone (TH) is crucial for metabolism and development in vertebrates, particularly during cold exposure.
• In zebrafish, TH influences locomotor performance and metabolism, but its role in muscle phenotype modulation is unclear.

Purpose of the Study:

• To investigate if TH influences zebrafish muscle phenotypes.
• To determine if TH-mediated muscle changes explain altered swimming capacity during thermal acclimation.

Main Methods:

• Zebrafish were made hypothyroid using propylthiouracil and iopanoic acid, then acclimated to 18°C or 28°C.
• TH-deficient fish were supplemented with T2 or T3 to confirm TH's role.
• Locomotor performance, tail beat kinematics, muscle enzyme activity, and gene expression were analyzed.

Main Results:

• Cold-acclimated fish showed higher sustained swimming (Ucrit) and tail beat frequency.
• Hypothyroidism reduced Ucrit, burst speed, tail beat frequency, and SERCA activity, while increasing myofibrillar ATPase.
• TH supplementation (T2/T3) normalized all measured parameters in hypothyroid fish.

Conclusions:

• TH directly regulates zebrafish muscle physiology, impacting locomotor performance.
• TH's modulation of SERCA1 expression during cold acclimation may link to thermogenesis regulation.