Mitochondrial function is enhanced by thyroid hormones during zebra finch development.

Area of Science:

• * Physiological Ecology
• * Developmental Biology
• * Mitochondrial Metabolism

Background:

• * Organismal response to environment relies on energy from aerobic mitochondrial metabolism and adenosine triphosphate (ATP) production.
• * Environmental factors influencing energy metabolism and mitochondrial function are poorly understood, with recent studies suggesting a role for thyroid hormones (TH).
• * Thyroid hormones (TH) are critical regulators of growth and metabolism, adaptable to environmental conditions like temperature and food availability.

Purpose of the Study:

• * To investigate the causal link between enhanced thyroid hormones (TH) and mitochondrial function during development.
• * To determine the effect of TH on growth and mitochondrial ATP production in a challenging environment.
• * To explore the implications of TH-mediated mitochondrial regulation for fitness-related traits.

Main Methods:

• * Oral administration of physiological concentrations of TH to zebra finch (Taeniopygia guttata) nestlings during their main growth phase.
• * Rearing nestlings in a challenging environmental setting to simulate real-world conditions.
• * Measurement of maximal mitochondrial working capacity as an indicator of ATP production.

Main Results:

• * TH treatment significantly accelerated maximal mitochondrial working capacity in nestling zebra finches.
• * Mitochondrial ATP production capacity was enhanced by TH treatment.
• * No significant effect of TH treatment on overall growth was observed.

Conclusions:

• * Thyroid hormones (TH) play a crucial role in regulating mitochondrial function during development.
• * Enhanced TH levels can increase mitochondrial energy production capacity without compromising growth.
• * This study provides the first characterization of TH regulation of mitochondria during development in a semi-naturalistic context, with implications for fitness traits.