Nitric oxide suppresses preadipocyte differentiation in 3T3-L1 culture

Nitric oxide (NO) is an important chemical messenger controlling many physiological functions, involving cell proliferation, and differentiation. The purpose of this study was to investigate the effect of NO on adipocyte differentiation using a murine preadipocyte cell line, 3T3-L1. The treatment with a NO donor, 1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene (NOC18), reduced some markers of adipocyte differentiation such as glycerol-3-phosphate dehydrogenase activity, and intracellular lipid accumulation. To examine whether these effects of NOC18 on adipocyte differentiation markers are due to its cytotoxity, lactate dehydrogenase (LDH) release from the cells were measured. NOC18 did not affect LDH release into the culture medium. Thus, the suppressive actions of NO donor were unlikely to result from its cytotoxicity. Peroxisome proliferator-activated receptor (PPAR) γ is a critical transcription factor for adipocyte differentiation and adipocyte fatty acid binding protein (aP2) gene is one of its targets. Protein expression of PPARγ was not diminished by NOC18 treatment, although mRNA expression of aP2 was reduced. Electrophoretic mobility shift assay showed that NOC18 interfered with the DNA binding activity of PPARγ. Therefore, the present experiment suggest that NO suppresses adipocyte differentiation through suppressing the transcriptional activity of PPARγ, without suppressing its expression level.