Acetoacetate protects macrophages from lactic acidosis-induced mitochondrial dysfunction by metabolic reprograming
Clément Adam, Léa Paolini, Naïg Guéguen, Guillaume Mabilleau, Laurence Preisser, Simon Blanchard, Pascale Pignon, Florence Manero, Morgane Le Mao, Alain Morel, Pascal Reynier, Céline Beauvillain, Yves Delneste, Vincent Procaccio, Pascale Jeannin
Abstract
Lactic acidosis, the extracellular accumulation of lactate and protons, is a consequence of increased glycolysis triggered by insufficient oxygen supply to tissues. Macrophages are able to differentiate from monocytes under such acidotic conditions, and remain active in order to resolve the underlying injury. Here we show that, in lactic acidosis, human monocytes differentiating into macrophages are characterized by depolarized mitochondria, transient reduction of mitochondrial mass due to mitophagy, and a significant decrease in nutrient absorption. These metabolic changes, resembling pseudostarvation, result from the low extracellular pH rather than from the lactosis component, and render these cells dependent on autophagy for survival. Meanwhile, acetoacetate, a natural metabolite produced by the liver, is utilized by monocytes/macrophages as an alternative fuel to mitigate lactic acidosis-induced pseudostarvation, as evidenced by retained mitochondrial integrity and function, retained nutrient uptake, and survival without the need of autophagy. Our results thus show that acetoacetate may increase tissue tolerance to sustained lactic acidosis.