Lactate : le substrat énergétique de demain

Lactate, an ubiquitous metabolite derives from glycolysis. Pyruvate is enzymatically reduced into lactate by the lacticodeshydrogenase. Lactate consumption results from pyruvate oxidation or gluconeogenesis, essentially by the liver. Lactatemia results from an equilibrium between its production and its consumption. Lactatemia does not reflect lactate turnover which may be accelerated or braked without any variation in lactatemia. Lactate has been considered for a long time as a final metabolite, at least useless if not toxic. As a shuttle implicated in various cycles (glucose-lactate Cori's cycle), lactate appears as an energy substrate used in various conditions. Indeed, Cori's cycle is essential for ATP production by erythrocytes, which do not contain mitochondrias. This cycle is also effective for skeletal muscles during exercise. Myocardium during ischemia-reperfusion or hypoxia, shifts its oxidative metabolism from free fatty acids to carbohydrates, especially lactate. Indeed, sodium lactate after cardiac surgery improves cardiac index. Lactate seems to be also implicated as an energy substrate in brain. Clinical studies have shown that sodium lactate infusion decreased intracranial hypertension and improved the neurological outcome of severe traumatic brain injury. This treatment was also able to improve the neurological recovery after hypoglycemia, which indicates clearly that brain can consume lactate to supply its energy demand.