Menadione and iron overload trigger neutral lipid remodelling in adipocytes and adipose tissue

Abstract

A growing body of evidence indicates that oxidative stress (OS) can cause an increase in preadipocyte proliferation, and adipocyte differentiation. However, the biochemical mechanisms by which OS alters adipocyte neutral lipid metabolism are not completely elucidated. Menadione and iron (Fe) overload are well known OS enhancers through the induction of Fenton and Haber-Weiss reactions. We have previously demonstrated that menadione exposure (20 and 50 µM) in differentiated 3T3- L1 adipocytes results in increased cell oxidant levels and downregulation of adipogenic genes and transcription factors. In this work, our goal was to investigate the effect of menadione and Fe overload in neutral lipid metabolism both in adipocyte cell culture and by using an in vivo model. For this purpose, we worked with differentiated adipocytes challenged with menadione and C57BL/6 mice exposed to Fe overload. Differentiated 3T3-L1 adipocytes were exposed to menadione for 24 h, and then neutral lipid profile was analyzed. For the in vivo OS model, Fe-saccharate (800 or 1332 mg/kg) or vehicle were administered by intraperitoneal injection (four-dose scheme in 16 days). Plasma, visceral and gonadal adipose tissue obtained from Fetreated animals and controls were used to determine OS markers and neutral lipids. In mice, lipid peroxide levels and conjugated dienes derived from fatty acid oxidation were increased in visceral and gonadal adipose tissue after Fe treatment. No changes were detected in catalase activity. Moreover, OS markers from plasma were also augmented by Fe-overload. We found that menadione-induced OS increased triglyceride content and activated lipolysis in adipocytes. Intriguingly, monoacylglycerol and diacylglycerol levels were decreased, and no difference was observed in triacylglycerol levels in Feoverloaded mice. Fe treatment caused a diminution in wet weight of both gonadal and visceral adipose tissues when compared to control animals. Consequently, the ratio triacylglycerol/g wet tissue was increased by the effect of OS. Together, our results demonstrate that different OS inducers promote an active remodeling of neutral lipids in adipose tissue.