Endocrinol Metab > Volume 26(3); 2011 > Article
Endocrinology and Metabolism 2011;26(3):232-238.
DOI: https://doi.org/10.3803/EnM.2011.26.3.232    Published online September 1, 2011.
Effect of Thyroid Hormone to the Expression of Bile Salt Export Pump.
Hwa Young Ahn, Kwan Jae Lee, Soon Hui Kim, Eun Ky Kim, Ah Reum Kang, Jung Ah Lim, Ji Won Yoon, Kyung Won Kim, Do Joon Park, Bo Youn Cho, Young Joo Park
1Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea. yjparkmd@snu.ac.kr
2Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
3Department of Internal Medicine, Seoul National University, Healthcare System, Seoul, Korea.
4Department of Internal Medicine, Chung-Ang University Hospital, College of Medicine, Chung-Ang University, Seoul, Korea.
Abstract
BACKGROUND
Bile acids were important for the regulation of cholesterol homeostasis. Thyroid hormone increased the expression of CYP7A1 (cholesterol 7alpha-hydroxylase), catalyzing the first step in the biosynthesis of bile acids. However, the effect of thyroid hormone on bile acid export has not been previously assessed. The principal objective of this study is to evaluate the effects of thyroid hormone on the bile salt export pump (BSEP). METHODS: Thyroid hormone, T3 (1 mg/g) was administered to male mice via intraperitoneal injection. After 6 hours and 5 days of T3 treatment, we measured serum total and LDL cholesterol and hepatobiliary bile acid concentrations. We assessed the changes associated with bile acid synthesis and transport. In order to evaluate the direct effect of thyroid hormone, we assessed the changes in the levels of BSEP protein after T3 administration in human hepatoma cells. RESULTS: Serum total and LDL cholesterol were reduced and hepatobiliary bile acid concentrations were increased following T3 treatment. Expressions of Cyp7a1 and BSEP mRNA were increased following T3 treatment. The levels of the BSEP protein in the mouse liver as well as in the human hepatoma cells were increased after T3 treatment. CONCLUSION: Thyroid hormone can regulate LDL cholesterol metabolism. It increases bile acid synthesis and the excretion of bile acids via increased BSEP expression.
Key Words: Bile acids, Cholesterol, Thyroid hormone


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