Flavonoid apigenin is an inhibitor of the NAD⁺ase CD38: Implications for cellular NAD⁺ metabolism, protein acetylation, and treatment of metabolic syndrome

Metabolic syndrome is a growing health problem worldwide. It is therefore imperative to develop new strategies to treat this pathology. In the past years, the manipulation of NAD⁺ metabolism has emerged as a plausible strategy to ameliorate metabolic syndrome. In particular, an increase in cellular NAD⁺ levels has beneficial effects, likely because of the activation of sirtuins. Previously, we reported that CD38 is the primary NAD⁺ase in mammals. Moreover, CD38 knockout mice have higher NAD ⁺ levels and are protected against obesity and metabolic syndrome. Here, we show that CD38 regulates global protein acetylation through changes in NAD⁺ levels and sirtuin activity. In addition, we characterize two CD38 inhibitors: quercetin and apigenin. We show that pharmacological inhibition of CD38 results in higher intracellular NAD⁺ levels and that treatment of cell cultures with apigenin decreases global acetylation as well as the acetylation of p53 and RelA-p65. Finally, apigenin administration to obese mice increases NAD⁺ levels, decreases global protein acetylation, and improves several aspects of glucose and lipid homeostasis. Our results show that CD38 is a novel pharmacological target to treat metabolic diseases via NAD⁺-dependent pathways.