Post-mortem analysis of lactate concentration in diabetics and metformin poisonings

Lactate is produced in carbohydrate metabolism under anaerobic conditions. Lactic acidosis occurs when the production of lactate exceeds its removal. In post-mortem (PM) context, the lactic acidosis is difficult to interpret due to unknown pathophysiological factors prior to death and PM changes that may affect the lactate levels. We evaluated 1865 medico-legal autopsy cases where the quantitation of glucose, lactate, and ketone bodies was performed as a part of the cause of death (CoD) investigation. Lactate was shown to ascend in a logarithmic manner as the PM interval increased until a plateau was achieved approximately after 8-10 days PM, and the elevation was caused mainly by PM changes. The lactate level was higher than the mean in cases where the CoD was diabetes mellitus type 2 (DM2) or metformin poisoning. Although there was a correlation between metformin and lactate levels, our findings suggest the DM2 and its complications were the cause for elevated lactate levels rather than metformin, since the lactate levels were similar in DM2-associated deaths where no metformin was detected. Elevated lactate levels in PM samples rather referred to metabolic disturbances often caused by DM2. An assay to detect D-lactate in PM samples was described.