Resveratrol Induces a Mitochondrial Complex I-dependent Increase in NADH Oxidation Responsible for Sirtuin Activation in Liver Cells

Background: The mechanism of action of resveratrol on sirtuin and mitochondrial metabolism remains elusive. Results: Resveratrol increases the mitochondrial NAD(+) level by direct stimulation of complex I, leading to a SIRT3-dependent increase in substrate supplies. Conclusion: Our results link the direct stimulation by resveratrol of NADH oxidation to the SIRT3 activation. Significance: Mitochondrial NAD(+)/NADH ratio is a critical parameter mediating resveratrol effect on mitochondrial function. Resveratrol (RSV) has been shown to be involved in the regulation of energetic metabolism, generating increasing interest in therapeutic use. SIRT1 has been described as the main target of RSV. However, recent reports have challenged the hypothesis of its direct activation by RSV, and the signaling pathways remain elusive. Here, the effects of RSV on mitochondrial metabolism are detailed both in vivo and in vitro using murine and cellular models and isolated enzymes. We demonstrate that low RSV doses (1-5 m) directly stimulate NADH dehydrogenases and, more specifically, mitochondrial complex I activity (EC50 approximate to 1 m). In HepG2 cells, this complex I activation increases the mitochondrial NAD(+)/NADH ratio. This higher NAD(+) level initiates a SIRT3-dependent increase in the mitochondrial substrate supply pathways (i.e. the tricarboxylic acid cycle and fatty acid oxidation). This effect is also seen in liver mitochondria of RSV-fed animals (50 mg/kg/day). We conclude that the increase in NADH oxidation by complex I is a crucial event for SIRT3 activation by RSV. Our results open up new perspectives in the understanding of the RSV signaling pathway and highlight the critical importance of RSV doses used for future clinical trials.