Carbohydrate Response Element Binding Protein Gene Expression Is Positively Regulated by Thyroid Hormone

• Published in: Endocrinology (Philadelphia) Vol. 150; no. 7; pp. 3417 - 3424
• Main Authors: Hashimoto, Koshi, Ishida, Emi, Matsumoto, Shunichi, Okada, Shuichi, Yamada, Masanobu, Satoh, Teturou, Monden, Tsuyoshi, Mori, Masatomo
• Format: Journal Article
• Language: English
• Published: Chevy Chase, MD Endocrine Society 01.07.2009; The Endocrine Society
• Subjects: Animals; Biological and medical sciences; Cell Line, Tumor; DNA-Binding Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Liver - metabolism; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Nuclear Proteins - biosynthesis; Orphan Nuclear Receptors; Promoter Regions, Genetic - drug effects; Receptors, Cytoplasmic and Nuclear - metabolism; Thyroid Hormones - physiology; Transcription Factors - biosynthesis; Triiodothyronine - physiology; Up-Regulation; Vertebrates: endocrinology; Binding protein; Thyroid hormone; Carbohydrate; Gene expression; Response element
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2009-0059

The molecular mechanism of thyroid hormone (TH) effects to fatty acid metabolism in liver is yet to be clear. The carbohydrate response element-binding protein (ChREBP) as well as sterol response element-binding protein (SREBP)-1c plays a pivotal role in hepatic lipogenesis. Both SREBP-1c and ChREBP are target genes of liver X receptors (LXRs). Because LXRs and TH receptors (TRs) cross talk mutually in many aspects of transcription, we examined whether TRs regulate the mouse ChREBP gene expression. In the current study, we demonstrated that TH up-regulated mouse ChREBP mRNA and protein expression in liver. Run-on and luciferase assays showed that TH and TR-β1 positively regulated the ChREBP gene transcription. The mouse ChREBP gene promoter contains two direct repeat-4 sites (LXRE1 and LXRE2) and EMSAs demonstrated that LXR-α and TR-β1 prefer to bind LXRE1 and LXRE2, respectively. The direct repeat-4 deletion and LXRE2 mutants of the promoter deteriorate the positive regulation by TR-β1, indicating that LXRE2 is functionally important for the regulation. We also showed that human ChREBP gene expression and promoter activities were up-regulated by TH. These data suggest that ChREBP mRNA expression is positively regulated by TR-β1 and TH at the transcriptional level in mammals. This novel observation indicates that TH fine-tunes hepatic lipogenesis via regulating SREBP-1c and ChREBP gene expression reciprocally. Mouse and human carbohydrate response element-binding protein gene expression is positively regulated by thyroid hormone in liver at the transcriptional levels, indicating the hormone fine-tunes hepatic lipogenesis.