Altered sirtuin deacetylase gene expression in patients with a mood disorder

Sirtuins are a family of NAD+-dependent enzymes that regulate cellular functions through deacetylation of various proteins. Although recent reports have suggested an important role of deacetylases (i.e., histone deacetylases) in mood disorders and antidepressant action, the involvement of sirtuins in the pathophysiology of mood disorders is largely unknown. In this study, we aimed to determine whether there are alterations in sirtuin mRNA expression in peripheral white blood cells of patients with a mood disorder. Also, to examine whether the altered sirtuin mRNA expression is state- or trait-dependent, mood disorder patients who were in a remissive state were assessed. We used quantitative real-time polymerase chain reaction to measure the mRNA levels of seven sirtuin isoforms (SIRT1-7) in peripheral white blood cells of patients with major depressive disorder (MDD) or bipolar disorder (BPD) during depressive and remissive states and in normal healthy subjects. The SIRT1, 2 and 6 mRNA levels in MDD and BPD patients decreased significantly in those who were in a depressive state compared to healthy controls, whereas the expression of those mRNAs in both MDD and BPD of patients in a remissive state were comparable to those in healthy controls. Thus, our data suggest that altered SIRT1, 2 and 6 expression is state-dependent and might be associated with the pathogenesis and/or pathophysiology of mood disorders.