Metformin-related colonic glucose uptake; potential role for increasing glucose disposal?--A retrospective analysis of (18)F-FDG uptake in the colon on PET-CT.

Aim: The use of metformin has been associated with diffusely increased colonic (18)F-fluorodeoxyglucose ((18)F-FDG) uptake. Interestingly, metformin use is associated with moderate weight loss. It could be hypothesized that increased colonic glucose disposal is related to this weight loss. It is unknown whether other factors influence (18)F-FDG uptake in the colon. The aim of this study was to retrospectively assess independent determinants of colonic (18)F-FDG uptake.
Methods: We retrospectively analysed 270 (18)F-FDG PET-CTs which were made for diagnostic purposes. Colonic (18)F-FDG uptake was assessed using a 4-point scale using the liver as a reference (1; lower, 2; similar, 3; moderately higher than hepatic activity, 4; intense diffuse increased uptake). Determinants of (18)F-FDG uptake in the colon were assessed using forward logistic regression (i.e., grade 1&2 vs 3&4).
Results: The patients had a mean age of 60.2±14.8 years, a BMI of 25.8±5.2kg/m(2) and 52% were female. Most patients had a grade 2 (44%) or grade 3 (39%) (18)F-FDG uptake in the colon. Diabetes mellitus type 2 was observed in 14% of the patients. In total, 5% of the patients used insulin, 12% used metformin and 5% used sulfonylurea derivatives (SU). While there seemed to be an effect of SU on (18)F-FDG uptake in the ileum [OR 3.6 (95% CI: 1.3-33.1), p=0.03], metformin was the only drug associated with (18)F-FDG uptake for both the whole colon [OR 10.0 (95% CI: 2.9-34.7), p<0.001] and all individual segments.
Conclusion: Metformin use is an independent determinant of increased colonic (18)F-FDG uptake, suggesting a potential role for increasing colonic glucose disposal.
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