Piceatannol effects on lipolysis of 3T3-L1 adipocytes

Adipose tissue plays an essential role in the regulation of lipid metabolism by storing the excess energy and releasing it through lipolysis. However, in some cases, dysfunctions in adipose tissue metabolism, specifically in lipolysis, may occur and cause metabolic disorders. Specifically, excessive lipolysis may promote the development of obesity and some cancers that may ultimately lead to insulin resistance/type 2 diabetes and cancer-associated cachexia, respectively. Because phytochemicals are actually viewed as promising therapeutic compounds for the control of metabolic diseases, a recent study investigated the effects of piceatannol on lipolysis. Piceatannol is a stilbene already known for its anti-adipogenic and anti-lipogenic effects. In that study, piceatannol was shown to inhibit isoproterenol-induced lipolysis when incubated with mouse adipocytes, for 4 hours, at a dose ≥ 100 µM (Les et al., 2016). In this context, the aim of this master thesis was to investigate and confirm the potential antilipolytic effects of piceatannol, using 3T3-L1 mouse adipocytes. For this purpose, 3T3-L1 preadipocytes were cultured and differentiated using classical differentiation cocktails containing insulin, among others. After 12 days of differentiation, cells were preincubated with piceatannol for either 2 or 24 hours before lipolysis. The following 5 piceatannol concentrations were tested : 10 µM, 50 µM, 100 µM, 500 µM and 1 mM. After this preincubation, the cytotoxicity of each piceatannol treatment was evaluated. Then, lipolysis was stimulated for 12 hours, using a lipolytic medium containing isoproterenol, a synthetic β-adrenergic agonist inducing lipolysis. During lipolysis, cells were still in contact with piceatannol, at the same concentrations than before. In order to highlight the effects of piceatannol on lipolysis, the levels of glycerol released in the lipolytic medium were regularly assessed for each piceatannol treatment. Our results demonstrate that piceatannol, at 1 mM and 500 µM, was cytotoxic after 24 hours of preincubation, while no cell damage was observed after 2 hours of preincubation with piceatannol. Therefore, the levels of lipolysis were only evaluated in the second scheme, when cells were preincubated with piceatannol for 2 hours before stimulating lipolysis during 12 hours. In total, cells were incubated with piceatannol for 14 hours. We showed that the glycerol levels released with 1 mM and 500 µM piceatannol were significantly lower than those released with smaller piceatannol concentrations as well as those observed with the lipolytic control, in which no piceatannol was added. In fact, the levels of glycerol released with 1 mM and 500 µM piceatannol were closer to those obtained during a basal lipolysis. We concluded that piceatannol, at 1 mM and 500 µM, inhibits stimulated lipolysis and induces a return to basal lipolysis. On a short-term basis, further examinations of the mechanism of action used by piceatannol to inhibit lipolysis are needed. On a long-term basis, thanks to its anti-lipolytic effects, piceatannol could be used in vivo for the control of insulin resistance and cancer-associated cachexia.