Energy metabolism and substrates oxidative patterns in type 2 diabetic patients treated with sulphonylurea alone or in combination with metformin

Objective: To compare substrates oxidative patterns in type 2 diabetic patients treated with sulphonylurea alone or in combination with metformin. Methods: Plasma glucose (PG), plasma insulin (PI) and substrates oxidation rates measured by indirect calorimetry were compared during a test day at 8.00 a.m. (before breakfast), 11.00 a.m. (before the lunch), 2.00 p.m. (2 h after the lunch) and at 5.00 p.m. in 56 diabetic patients treated with diet (group C, n = 14), sulphonylurea (group S, n = 14) or with a sulphonylurea-metformin combination (group SM, n = 28). Results: The three groups were comparable for age, body mass index (b.m.i.), body composition and PG levels. Mean glucose oxidation (Gox) was increased since mean lipid oxidation (Lox) was decreased in group S in comparison both with group C (3.02 +/- 0.08 vs. 2.62 +/- 0.08 g/min/kg/10(3), p < 0.05; 0.53 +/- 0.04 vs. 0.88 +/- 0.09 g/min/kg/10(3), p < 0.01). Mean Lox was also decreased in group S in comparison with group SM (0.88 +/- 0.06 vs. 0.53 +/- 0.04 g/min(1)/kg(1)/10(3), p < 0.0001) whereas the difference in Gox between these latter two groups was only significant in the basal state (1.94 +/- 0.17 vs. 2.47 +/- 0.17 g/min(1)/kg(1)/10(3), p < 0.05). Mean respiratory quotient (RQ) was increased in group S (0.90 +/- 0.01) in comparison both with group C (0.86 +/- 0.01, p < 0.001) and with group SM (0.86 +/- 0.01, p < 0.001). Mean energy expenditure was lower in group S than in group SM (21.4 +/- 0.6 vs. 23.6 +/- 0.6 kcal/min/kg/10(3), p < 0.05). Substrates oxidative patterns, RQ values and energy expenditure were similar in group C and in group SM. Conclusions: When compared to patients treated with a sulphonylurea-metformin bitherapy, patients treated with a sulphonylurea monotherapy have a shift in their ratio of fat to carbohydrate oxidation that could make body weight loss more difficult in this latter group.