The neglected foodborne mycotoxin Fusaric acid induces bioenergetic adaptations by switching energy metabolism from mitochondrial processes to glycolysis in a human liver (HepG2) cell line

Abstract

Metabolic flexibility defines the capacity of cells to respond to changes in nutrient status. Mitochondria are important mediators of metabolic flexibility and dysfunction is associated with metabolic inflexibility and pathology. Foodborne toxins are often overlooked as potential factors contributing to metabolic toxicity. Fusaric acid (FA), a neglected mycotoxin, is known to disrupt mitochondrial function. The aim of this study was to investigate the molecular mechanisms underlying a metabolic switch in response to FA. This study investigated the effects of FA on energy homeostasis in cultured human liver (HepG2) cells. HepG2 cells poised to undergo oxidative and glycolytic metabolism were exposed to a range of FA concentrations (4, 63 and 250 μg/mL) for 6 h. We determined mitochondrial toxicity, acetyl CoA levels and cell viability using luminometric, fluorometric and spectrophotometric methods. Expression of metabolic proteins (PDK1, PKM2, phosphorylated-PDH E1α and HIF-1α) and mRNAs (HIF-1α, PKM2, LDHa and PDK1) were determined using western blot and qPCR respectively. Our data connects a constitutive expression of HIF-1α in response to FA, to the inhibition of pyruvate decarboxylation through up-regulation of PDK-1 and phosphorylation of Pyruvate Dehydrogenase E1α subunit. Moreover, we highlight the potential of FA to induce a glucose “addiction” and phenotype reminiscent of the Warburg effect. The findings provide novel insights into the impact of this neglected foodborne mycotoxin in the dysregulation of energy metabolism.