Radioactivity Reduction of 2-Deoxy-2-[18F] Fluoro-D-Glucose by Milk and Ursodeoxycholic Acid in Preclinical Study

Purpose: 2-Deoxy-2-[¹⁸F] fluoro-d-glucose positron emission tomography (¹⁸F-FDG-PET) is a less-invasive and widely used diagnostic tool for detection of malignant tumors. However, prolonged retention of ¹⁸F-FDG in the body increases radiation exposure. This study evaluated the effect of oral administration of milk and ursodeoxycholic acid (UDCA) in terms of reducing radiation exposure by ¹⁸F-FDG. Methods: ¹⁸F-FDG radioactivity was measured using a digital γ counter in the whole body and in various organs of rats after oral administration of milk and milk plus UDCA (milk + UDCA). Western blotting was performed to measure the expression levels of G6Pase, HK 2, CREB, FoxO1, and PGC-1α in the brain, liver, small intestine, and large intestine to assess the mechanism underlying the reduction in radiation exposure from ¹⁸F-FDG by oral administration of milk and UDCA. Results: We found a significant reduction in ¹⁸F-FDG radioactivity in the whole body and in the brain, liver, and small and large intestines. Expression of G6Pase was significantly increased in the above-mentioned organs in the milk and milk + UDCA groups. Expression of HK 2 was significantly decreased in the brain and small intestine in the milk and milk + UDCA groups. CREB, FoxO1, and PGC-1α expression levels in the brain, liver, and small intestine were increased in the milk and milk + UDCA groups. However, expression of PGC-1α in the large intestine in the milk and milk + UDCA groups was significantly decreased compared with that in the control group. Conclusion: The present study demonstrated that administration of milk and UDCA increased G6Pase expression levels and ¹⁸F-FDG release from the tissue. These results suggest milk and UDCA could be used to reduce radiation exposure from ¹⁸F-FDG after image acquisition. The mechanisms underpinning this phenomenon should be explored in a human study.