Abstract
The farnesoid X receptor (FXR; NR1H4) is an intracellular bile acid-sensing transcription factor that plays a critical role in the regulation of synthesis and transport of bile acids as well as lipid metabolism. Although the reciprocal relationship between bile acid and triglyceride levels is well known, the mechanism underlying this link is not clearly defined. In this study, we demonstrate that FXR regulates the expression of at least two secreted factors, complement component C3 and FGF15, the rat ortholog of FGF19, known to influence lipid metabolism. The analysis of the human complement C3 gene reveals the presence of functional FXR response elements in the proximal promoter of C3. Furthermore, rats given a single dose of an FXR agonist exhibit an increase in the plasma concentration of complement C3 protein. These studies demonstrate a mechanism by which FXR, a nuclear receptor with a limited tissue expression pattern, regulates secretion of factors that ultimately can affect lipid metabolism in an endocrine or paracrine manner.
MeSH terms
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Animals
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Base Sequence
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Bile Acids and Salts / metabolism*
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Binding Sites
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Blotting, Northern
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Blotting, Western
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Caco-2 Cells
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Cell Line
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Cell Line, Tumor
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Cell Membrane / metabolism
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Cell Nucleus / metabolism
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Complement C3 / biosynthesis*
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Complement C3 / genetics
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DNA Primers / chemistry
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DNA, Complementary / metabolism
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DNA-Binding Proteins / metabolism*
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Electrophoresis, Polyacrylamide Gel
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Fibroblast Growth Factors / metabolism
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Genes, Reporter
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Genetic Complementation Test
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Humans
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Ligands
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Lipid Metabolism
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Luciferases / metabolism
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Male
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Models, Genetic
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Molecular Sequence Data
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Mucous Membrane / pathology
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Oligonucleotides / chemistry
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Promoter Regions, Genetic
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RNA, Messenger / metabolism
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Rats
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Rats, Inbred F344
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Receptors, Cytoplasmic and Nuclear
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Reverse Transcriptase Polymerase Chain Reaction
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Time Factors
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Transcription Factors / metabolism*
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Transfection
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Triglycerides / metabolism
Substances
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Bile Acids and Salts
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Complement C3
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DNA Primers
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DNA, Complementary
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DNA-Binding Proteins
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Ligands
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Oligonucleotides
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RNA, Messenger
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Receptors, Cytoplasmic and Nuclear
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Transcription Factors
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Triglycerides
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fibroblast growth factor 15, mouse
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farnesoid X-activated receptor
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Fibroblast Growth Factors
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Luciferases