Rapid synergistic interaction between thyroid hormone and carbohydrate on mRNAS14 induction

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Hepatic mRNAS14 shows rapid response to thyroid hormone and increases with carbohydrate-rich diets.
• mRNAS14 shares properties with hepatic lipogenic enzymes, suggesting a role in carbohydrate metabolism.
• Lipogenic enzymes exhibit synergistic interactions between thyroid hormones and carbohydrates.

Purpose of the Study:

• To investigate the kinetics of mRNAS14 response to carbohydrate feeding.
• To explore the interaction between mRNAS14, carbohydrates, and triiodothyronine (T3).
• To elucidate the mechanism of synergistic induction of mRNAS14 by T3 and carbohydrates.

Main Methods:

• Studied mRNAS14 response to sucrose in euthyroid and hypothyroid rats.
• Investigated the effect of insulin and T3 administration on mRNAS14 levels.
• Performed dose-response studies with T3 and examined T3-nuclear receptor interaction.
• Utilized primary hepatocyte cultures to assess T3 and glucose synergism.

Main Results:

• Sucrose rapidly increased mRNAS14 in euthyroid rats (2-fold in 30 min, 25-fold in 4 h).
• Hypothyroid rats showed a diminished sucrose response (2-3 fold), not enhanced by insulin.
• T3 administration restored the rapid sucrose response, demonstrating synergism.
• Synergistic response to T3 and glucose observed in hepatocytes, independent of extrahepatic factors.

Conclusions:

• The T3-nuclear receptor complex likely amplifies signals from carbohydrate metabolism to induce hepatic mRNAS14.
• The synergistic interaction between T3 and carbohydrates is mediated by T3 receptor occupancy.
• This induction mechanism does not appear to require prior induction of carbohydrate-metabolizing enzymes.