Introduction: SIRT3 is a NAD+ dependent protein deacetylase which, when under-expressed, has been linked to the metabolic syndrome and pulmonary arterial hypertension. Our laboratory has shown that animals with pulmonary hypertension associated with heart failure with preserved ejection fraction (PH-HFpEF) associated with the metabolic syndrome demonstrate SIRT3 deficiency exclusively in the skeletal muscle. Restoration of SIRT3 in skeletal muscle with nitrite and metformin therapies improve disease phenotype, suggesting a casual role of SIRT3 activation in skeletal muscle in the management of metabolic syndrome-associated pulmonary hypertension. In this study, we attempted to (a) identify more potent SIRT3 activators using high throughput screening (HTS) and (b) assess their efficacy in activating SIRT3 in skeletal muscle cells.
Methods and Results: A library of 1100 FDA-approved drugs were screened for SIRT3 activity by adding each drug to the final concentration of 10uM, followed by incubation with substrate of SIRT3, human recombinant SIRT3, and co-factor NAD+. SIRT3 activation was determined by relative increase in florescence. Dolutegravir, Chlortetracycline, Prazosin, Terazosin, Alfusozin were identified as SIRT3 activators by this HTS method. In comparison with other SIRT3 activators identified by our group and others, such as Honokiol, Adjudin, Losartan, Metformin, and Nitrite, we next assessed their efficacy in activating SIRT3 in C2C12 cells. These drugs were administered to C2C12 cells (passage 10-12) during myoblast differentiation to a final concentration of 10uM in the presence or absence of the treatment of PGI (0.35 mM palmitic acid, 25mM glucose, and 120nM insulin) to induce insulin resistance. SIRT3 expression was assessed by Western blot. Our data showed that C2C12 cells treated with Prazosin, Adjudin, Terazosin, and Dolutegravir had higher activation levels of SIRT3 compared to other drugs tested.
Conclusions: We identified five potential SIRT3 activators by HTS with the small library of FDA-approved drugs. Our data also suggests that Prazosin, Adjudin, Terazosin, and Dolutegravir may function as skeletal muscle SIRT3 activators, which may offer a new avenue for treating PH-HFpEF.