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DOI: 10.1055/s-0036-1580818
Pharmacological inhibition of nicotinamide N-methyltransferase (NNMT) in adipocytes by romidepsin
Background: Expression of nicotinamide N-methyltransferase (NNMT) is increased in adipose tissue in obesity. Fat-specific knockdown of NNMT with antisense oligonucleotides (ASO) prevents diet-induced obesity in mice. In cultured adipocytes however, transfection efficiency of ASO is poor. Romidepsin (depsipeptide) is a small molecule that suppresses NNMT expression in cultured thyroid cancer cells, but whose effects on differentiated cultured adipocytes are unknown.
Aim: We aimed to determine if romidepsin is suitable for the study of NNMT activity in adipocytes.
Methods: Fully differentiated 3T3-L1 adipocytes and immortalized brown adipocytes were treated with romidepsin at various concentrations. NNMT activity was assayed using a novel non-radioactive microtiter-plate assay.
Results: Romidepsin suppresses NNMT activity in a dose-dependent manner by up to 35% with a first effect seen at 5 ng/ml in white 3T3-L1 adipocytes (p = 0.017 by linear regression). In brown adipocytes, romidepsin suppresses NNMT activity in a dose-dependent manner by up to 50% with a first effect also seen at 10 ng/ml (p = 0.022 by linear regression). In agreement with the effects of NNMT knockdown by ASO in vivo, romidepsin-induced suppression of NNMT activity reduces the lipid content of adipocytes without appreciable impact on cell viability at low concentrations of romidepsin.
Conclusion: Romidepsin may be a more suitable tool than transfection with ASO or viral transduction to manipulate NNMT in fully differentiated cultured adipocytes.