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

- The colon seems to be involved to some extent in the disposal of excess glucose in humans.
- Approximately half of the subjects have a high 18F-FDG uptake in the colon.
- In multivariable analysis, metformin remained the strongest predictor for 18F-FDG uptake in the colon.
- SU's might also have an effect on 18F-FDG uptake in the colon.

AimThe use of metformin has been associated with diffusely increased colonic 18F-fluorodeoxyglucose (18F-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 18F-FDG uptake in the colon. The aim of this study was to retrospectively assess independent determinants of colonic 18F-FDG uptake.MethodsWe retrospectively analysed 270 18F-FDG PET-CTs which were made for diagnostic purposes. Colonic 18F-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 18F-FDG uptake in the colon were assessed using forward logistic regression (i.e., grade 1&2 vs 3&4).ResultsThe patients had a mean age of 60.2 ± 14.8 years, a BMI of 25.8 ± 5.2 kg/m2 and 52% were female. Most patients had a grade 2 (44%) or grade 3 (39%) 18F-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 18F-FDG uptake in the ileum [OR 3.6 (95% CI: 1.3-33.1), p = 0.03], metformin was the only drug associated with 18F-FDG uptake for both the whole colon [OR 10.0 (95% CI: 2.9-34.7), p < 0.001] and all individual segments.ConclusionMetformin use is an independent determinant of increased colonic 18F-FDG uptake, suggesting a potential role for increasing colonic glucose disposal.