High accumulation of metformin in colonic tissue of subjects with diabetes or metabolic syndrome.

1557Background: Epidemiological studies consistently observed an association between metformin use in diabetic patients and decreased colon cancer incidence and mortality at clinical doses (1500-2250 mg day), corresponding to plasma levels of 0.003-0.045 mM. Preclinical models report much higher doses of metformin, ranging between 1 and 40 mM for in vitro and 0.006-0.145 mM for in vivo studies. A recent trial using a low dose of metformin (250 mg/day, Higurashi T et al. Lancet 2016;17:475) showed a 40% reduction of colorectal adenoma recurrence. We performed a pilot study to measure metformin in plasma and colonic tissue of subjects with diabetes or metabolic syndrome and to explore their correlation with different tissue biomarkers, including Ki-67, pS6k, a mTOR effector protein, and EGFR expression. Methods: We used LC-MS/MS to quantify metformin in plasma and colonic tissues from 13 volunteers with diabetes or metabolic syndrome undergoing screening colonoscopy. All patients had received metformin at 1...