Design and Characterization of a Novel Fluorinated Magnetic Resonance Imaging Agent for Functional Analysis of Bile Acid Transporter Activity
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To synthesize a trifluorinated bile acid that can be used for 19F magnetic resonance imaging (MRI) of bile acid enterohepatic circulation, characterize its in vitro transporter affinity, stability, and 19F-MRI signal, and assess its ability to concentrate in the gallbladder of C57BL/6 mice.
Target compound CA-lys-TFA was synthesized and tested for affinity toward the apical sodium dependent bile acid transporter (hASBT) and the Na+/taurocholate cotransporting polypeptide (hNTCP). In a pilot study, fasted mice were gavaged with vehicle control, 150 mg/kg or 300 mg/kg CA-lys-TFA. CA-lys-TFA in gallbladder, liver and plasma at t = 5 h was quantified. Additionally, a 24-h time course (24 mice across eight time points) was studied using 50 mg/kg CA-lys-TFA.
CA-lys-TFA was a potent substrate of hASBT (Kt = 39.4 μM, normalized Vmax = 0.853) and hNTCP (Kt = 8.99 μM, normalized Vmax = 0.281). 19F MRI phantom imaging showed linear signal-concentration dependence. In vivo studies showed that rapid accumulation of CA-lys-TFA in the gallbladder was maximal within 4–7 h.
These findings suggest that CA-lys-TFA, a fluorinated non-radioactive bile acid analogue, has potential for use in MRI to measure in vivo bile acid transport and diagnose bile acid malabsorption and other conditions associated with impaired bile acid transport.
KEY WORDSapical sodium-dependent bile acid transporter bile acid transport enterohepatic circulation fluorine MRI Na+/taurocholate cotransporting polypeptide
bile acid malabsorption
cholic acid-trifluoroacetyl lysine
dulbecco’s modified Eagle medium
dulbecco’s phosphate buffered saline
fetal bovine serum
fibroblast growth factor 19
fast low angle shot
human apical sodium-dependent bile acid transporter
hematoxylin and eosin
Hank’s balanced salt solution
O-benztriazol-1-yloxytris-1,1,3,3 tetra methyl uranium hexafluorophosphate
human embryonic kidney
Na+/taurocholate cotransporting polypeptide
irritable bowel syndrome
liquid chromatography/mass spectrometry
Madin-Darby canine kidney
multifluorinated bile acid
magnetic resonance imaging
number of average
aqueous boundary layer permeability
positron emission tomography
simulated intestinal fluid with pancreatic enzymes
ACKNOWLEDGMENTS AND DISCLOSURES
We acknowledge Dr. Kellie Hom for NMR help, Dr. Cinthia Drachenberg for histology analysis, and Dr. Werner Weitschies for donation of stably transfected hNTCP-HEK cells.
This work was supported by the National Institutes of Health [NIDDK T32 DK067872 Research Training in Gastroenterology; R21 DK093406, DK67530, and K08DKO81479].
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