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Background : Obesity is a pandemic disease characterized by excessive severe body comorbidities. Reduction in fat accumulation represents a mechanism of prevention, and the replacement of white adipose tissue (WAT) with brown adipose tissue (BAT) has been proposed as one promising strategy against obesity. In the present study, we sought to investigate the ability of a natural mixture of polyphenols and micronutrients (A5 + ) to counteract white adipogenesis by promoting WAT browning. Methods : For this study, we employed a murine 3T3-L1 fibroblast cell line treated with A5 + , or DMSO as control, during the differentiation in mature adipocytes for 10 days. Cell cycle analysis was performed using propidium iodide staining and cytofluorimetric analysis. Intracellular lipid contents were detected by Oil Red O staining. Inflammation Array, along with qRT-PCR and Western Blot analyses, served to measure the expression of the analyzed markers, such as pro-inflammatory cytokines. Results : A5 + administration significantly reduced lipids' accumulation in adipocytes when compared to control cells ( p < 0.005). Similarly, A5 + inhibited cellular proliferation during the mitotic clonal expansion (MCE), the most relevant stage in adipocytes differentiation ( p < 0.0001). We also found that A5 + significantly reduced the release of pro-inflammatory cytokines, such as IL-6 and Leptin ( p < 0.005), and promoted fat browning and fatty acid oxidation through increasing expression levels of genes related to BAT, such as UCP1 ( p < 0.05). This thermogenic process is mediated via AMPK-ATGL pathway activation. Conclusion : Overall, these results demonstrated that the synergistic effect of compounds contained in A5 + may be able to counteract adipogenesis and then obesity by inducing fat browning.

Tyrosol (TR), a major polyphenol found in extra virgin olive oil (EVOO), exerts several antioxidant effects. However, only scarce evidences are present regarding its activity on adipocytes and obesity. This study evaluated the role of TR in adipogenesis. Murine 3T3-L1 preadipocytes were incubated with TR (300 and 500  μ M), and TR administration inhibited adipogenesis by downregulation of several adipogenic factors (leptin and aP2) and transcription factors (C/EBP α , PPAR γ , SREBP1c, and Glut4) and by modulation of the histone deacetylase sirtuin 1. After complete differentiation, adipocytes treated with 300 and 500  μ M TR showed a reduction of 20% and 30% in lipid droplets, respectively. Intracellular triglycerides were significantly reduced after TR treatment ( p < 0.05). Mature adipocytes treated with TR at 300 and 500  μ M showed a marked decrease in the inflammatory state and oxidative stress as shown by the modulation of specific biomarkers (TNF, IL6, ROS, and SOD2). TR treatment also acted on the early stage of differentiation by reducing cell proliferation (~40%) and inducing cell cycle arrest during Mitotic Expansion Clonal (first 48 h of differentiation), as shown by the increase in both S1 phase and p21 protein expression. We also showed that TR induced lipolysis by activating the AMPK-ATGL-HSL pathway. In conclusion, we provided evidence that TR reduces 3T3-L1 differentiation through downregulation of adipogenic proteins, inflammation, and oxidative stress. Moreover, TR may trigger adipose tissue browning throughout the induction of the AMPK-ATGL-UCP1 pathway and, subsequently, may have promise as a potential therapeutic agent for the treatment and prevention of obesity., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2020 Francesca Pacifici et al.)

White adipose tissue (WAT) is no longer considered a depot for energy storage in the form of triglycerides, but is a secretory organ that releases factors, known as adipokines, capable of regulating several physiological processes. Alteration of WAT function with subsequent dysfunctional expression and secretion of adipokines plays a key role in the pathogenesis of obesity, diabetes, and other metabolic diseases. For this reason, a deeper understanding of the molecular mechanisms regulating adipocyte function is deemed necessary for planning strategies to treat and prevent obesity and its metabolic complications. This review examines cell culture models currently available for studying adipocyte biology. We focus on advantages, disadvantages and main differences between established preadipocyte cell lines and primary preadipocyte cultures. We revise protocols used to promote adipocyte differentiation and mature adipocytes dedifferentiation into preadipocytes. Finally, we briefly describe co-cultures of adipocytes with other cell types and three-dimensional adipocyte culture systems. These models allow investigation of cell-cell interactions with the cross-talk physiologically occurring between adipocytes and other cell types residing within or outside adipose tissue., ((c) 2010 Wiley-Liss, Inc.)