Taking metformin with a meal has been shown to decrease bioavailability of metformin. We hypothesized that taking metformin 30 min before a meal improves glucose metabolism. As an animal model, 18 Zucker-rats were divided into three groups as follows: no medication (Control), metformin (600 mg/kg) with meal (Met), and metformin 10 min before meal (pre-Met). In addition, five diabetic patients were recruited and randomized to take metformin (1000 mg) either 30 min before a meal (pre-Met protocol) or with a meal (Met protocol). In the animal model, the peak glucose level of pre-Met (7.8 ± 1.5 mmol/L) was lower than that of Control (12.6 ± 2.5 mmol/L, P = 0.010) or Met (14.1 ± 2.9 mmol/L, P = 0.020). Although there was no statistical difference among the three groups, total GLP-1 level at t = 0 min of pre-Met (7.4 ± 2.7 pmol/L) tended to be higher than that of Control (3.7 ± 2.0 pmol/L, P = 0.030) or Met (3.9 ± 1.2 pmol/L, P = 0.020). In diabetic patients, the peak glucose level of pre-Met protocol (7.0 ± 0.4 mmol/L) was lower than that of Met protocol (8.5 ± 0.9 mmol/L, P = 0.021). Total GLP-1 level at t = 30 min of pre-Met protocol (11.0 ± 6.1 pmol/L) was higher than that of Met protocol (6.7 ± 3.9 pmol/L, P = 0.033). Taking metformin 30 min before a meal ameliorated postprandial hyperglycemia. This promises to be a novel approach for postprandial hyperglycemia.
Keywords: Biguanides; Gastric emptying; Glucagon-like peptide-1 (GLP-1); Incretin; Metformin; Postprandial hyperglycemia; Type 2 diabetes.