Metformin and exercise: no additive effect on blood lactate levels in health volunteers

Metformin administration has been associated with substantial rises in blood lactate concentrations in individual Type 2 diabetic patients. Exercise also leads to increases in blood lactate levels. The objective of this study was to determine whether metformin administration augments the rise in plasma lactate concentrations during intermittent exercise in healthy subjects, when compared to placebo. Twelve healthy males (age 28 +/- 5 years, body mass index 22.7 +/- 1.3 kg m-2) took either 1.7 g metformin or placebo daily for 4 consecutive days before being subjected to strenuous intermittent exercise. On the morning of the fourth day exercise was performed on an upright bicycle ergometer at a work load of 200 W for 2 min alternating with 2 min rest for an overall duration of 60 min. Maximal plasma lactate levels during exercise (metformin: 4.1 +/- 2.6 mmol l(-)1, placebo: 4.5 +/- 2.6 mmol (l-1)), areas under the plasma lactate curve (207 +/- 121 vs 222 +/- 133 mmol l(-1) h(-1), blood pyruvate levels at the end of exercise (0.06 +/- 0.04 vs 0.07 +/- 0.04 mmol l(-1)), lactate/pyruvate ratio (65 +/- 41 vs 60 +/- 36), serum insulin (25.4 +/- 8.9 vs 32.3 +/- 13.0 pmol l(-1)), and plasma glucose (4.4 +/- 0.3 vs 4.5 +/- 0.3 mmol l(-1)) did not differ significantly between metformin and placebo administration. Administration of metformin did not lead to an augmented rise in endogenous plasma lactate concentrations during intermittent exercise in healthy fasting subjects under the experimental design chosen.