Deiodinases: How Nonmammalian Research Helped Shape Our Present View

Area of Science:

• Biochemistry
• Evolutionary Biology
• Endocrinology

Background:

• Iodothyronine deiodinases (D1, D2, D3) are crucial enzymes for activating and inactivating thyroid hormones (THs).
• Their existence was confirmed via cDNA cloning in the 1990s, and genomic data reveal their presence across diverse species, suggesting an ancient evolutionary origin.
• Deiodinases play a vital role in regulating TH action at the tissue level.

Observation:

• Biochemical properties of deiodinases, such as inhibition and temperature optima, exhibit variation across species.
• Research in non-mammalian models has significantly expanded the understanding of deiodinase function and diversity.
• Studies in fish, amphibians, and birds highlighted the importance of deiodination pathways in both local and systemic TH availability.

Findings:

• Non-mammalian models have revealed new local functions of deiodinases, such as reciprocal changes in hypothalamic tanycytes related to seasonal rhythms.
• Comparative studies demonstrate significant variations in deiodinase biochemical characteristics, including responses to inhibitors and temperature.
• Data from diverse species have reshaped the understanding of the relative importance of activating versus inactivating deiodination pathways.

Implications:

• Comparative deiodinase research provides critical insights into the regulation of thyroid hormone action.
• Understanding deiodinase diversity and function across species can inform studies on human thyroid hormone regulation.
• Advanced gene silencing techniques will further facilitate comparative research, deepening our knowledge of deiodinase roles in TH action.