Effect of oxidative stress on adipocyte differentiation

Abstract

Oxidative stress (OS) is a major characteristic of adipose tissue in obese patients and its role in adipose hyperplasia/hypertrophy has not been elucidated. The aim of our study was to analyze the effect of OS during adipogenesis as well on differentiated adipocytes. For this purpose, we worked with preadipocytes 3T3-L1 and menadione, a synthetic form of vitamin K known to generate intracellular oxygen species. Two different models were used: the “chronic”, in which OS (5, 10 y 15 μM menadione) was present during the whole process of 3T3-L1 differentiation, and the “acute”, in which differentiated adipo- cytes were exposed to OS (20 y 50 μM menadione) for 5 h. Adipogenesis, evaluated by Oil Red O staining as well as by the expression of adipogenic markers (PPARγ, C/EBPα, FAS, FABP4) by Western blot, was observed to be decreased in the chronic mod- el in a menadione concentration-dependent manner (p<0.01). The adipogenic markers were also found to significantly decrease upon acute treatment (p<0.001). However, no significant morphological changes were observed in differentiated adipocytes acutely treated with menadione. PI3K/Akt and ERK1/2 showed to be inversely reg- ulated: Akt was found to be inactivated whereas ERK1/2 were found to be activated in both models of menadione-induced OS. Interest- ingly, experiments in which adipogenesis was evaluated in the pres- ence of LY294002, a pharmacological PI3K inhibitor, but in the ab- sence of menadione showed a significant decreased differentiation. Our results demonstrate that acute menadione-induced OS triggers a gene expression program leading to the decreased expression of transcription factors and enzymes which are crucial for lipogenesis and, on the other hand, chronic menadione-induced OS prevents adipogenesis, presumably in part, in a PI3K-dependent manner. Keywords: adipogenesis, oxidative stress, lipid metabolism.