Antiadipogenic effect of carnosic acid, a natural compound present in Rosmarinus officinalis, is exerted through the C/EBPs and PPARγ pathways at the onset of the differentiation program

Background: Obesity is a serious health problem all over the world, and inhibition of adipogenesis constitutes one of the therapeutic strategies for its treatment. Carnosic acid (CA), the main bioactive compound of Rosmarinus officinalis extract, inhibits 3T3-L1 preadipocytes differentiation. However, very little is known about the molecular mechanism responsible for its antiadipogenic effect. Methods: We evaluated the effect of CA on the differentiation of 3T3-L1 preadipocytes analyzing the process of mitotic clonal expansion, the level of adipogenic markers, and the subcellular distribution of C/EBP beta. Results: CA treatment only during the first day of 3T3-L1 differentiation process was enough to inhibit adipogenesis. This inhibition was accompanied by a blockade of mitotic clonal expansion. CA did not interfere with C/EBP beta and C/EBP delta mRNA levels but blocked PPAR gamma, and FABP4 expression. C/EBP beta has different forms known as LIP and LAP. CA induced an increase in the level of LIP within 24 h of differentiation, leading to an increment in LIP/LAP ratio. Importantly, overexpression of LAP restored the capacity of 3T3-L1 preadipocytes to differentiate in the presence of CA. Finally, CA promoted subnuclear de-localization of C/EBP beta. Conclusions: CA exerts its anti-adipogenic effect in a multifactorial manner by interfering mitotic clonal expansion, altering the ratio of the different C/EBP beta forms, inducing the loss of C/EBP beta proper subnuclear distribution, and blocking the expression of C/EBP alpha and PPAR gamma. General significance: Understanding the molecular mechanism by which CA blocks adipogenesis is relevant because CA could be new a food additive beneficial for the prevention and/or treatment of obesity. (C) 2013 Elsevier B.V. All rights reserved.