Related Experiment Videos
The decrease of liver LDL receptor mRNA during fasting is related to the decrease in serum T3
A M van der Wal1, O Bakker, W M Wiersinga
1Department of Endocrinology, Academical Medical Center, University of Amsterdam, The Netherlands.
Summary
Fasting lowers thyroid hormones (T3 and T4) and decreases liver LDL receptor expression, leading to increased LDL cholesterol. Maintaining T3 levels prevents this rise, suggesting a link between thyroid function and cholesterol during fasting.
Area of Science:
- Endocrinology
- Metabolic Research
- Lipid Metabolism
Background:
- Fasting is known to alter thyroid hormone levels and lipid profiles.
- A potential link between fasting-induced hypothyroidism and increased LDL cholesterol has been proposed.
Purpose of the Study:
- To investigate the relationship between changes in thyroid hormones and cholesterol metabolism during fasting.
- To determine if a hypothyroid-like state induced by fasting contributes to elevated LDL cholesterol.
Main Methods:
- Rats were fasted for varying durations (0-48 hours).
- Measurements included serum thyroid hormones (T3, T4, TSH), liver enzyme mRNA expression (5'-deiodinase, LDL receptor, HMG CoA reductase, cholesterol 7 alpha-hydroxylase), and plasma LDL cholesterol.
- T3 supplementation was administered to some fasted rats.
Main Results:
- Fasting decreased liver 5'-deiodinase mRNA, serum T3, and serum T4.
- Plasma LDL cholesterol increased after 24 hours of fasting.
- Decreased liver LDL receptor mRNA expression preceded the rise in LDL cholesterol and correlated with serum T3 levels.
- T3 supplementation prevented the decrease in LDL receptor mRNA during fasting.
Conclusions:
- Fasting induces a hypothyroid-like condition, potentially due to inhibited hepatic T4 to T3 conversion.
- Fasting increases plasma LDL cholesterol, primarily mediated by reduced hepatic LDL receptor gene expression linked to lower serum T3 levels.