Polyphenols from a wild blueberry (Vaccinium angustifolium) powder reduce lipid accumulation in THP-1 derived macrophages

Polyphenols, such as phenolic acids and anthocyanins (ACNs), are widely studied for their protective effects against oxidative stress and inflammation. Recently, in vitro and in vivo studies suggest that polyphenol compounds may modulate lipid metabolism by preventing atherogenic and atherosclerotic processes. The molecular pathways involved in the prevention of lipid accumulation is not well known; however polyphenols seem to be able to modulate the transcriptional activities of different nuclear receptors that control lipid metabolism, including peroxisome proliferator-activated receptors, sterol regulatory element-binding proteins, liver X receptors. In the present study, we examined the effect of an ACN-rich fraction, obtained from a wild blueberry (WB) powder, on the capacity to counteract lipid accumulation in macrophages derived from monocytic THP-1 cells. The cells display characteristics similar to those in foam cells of atherosclerotic plaques. In addition it was tested the capacity to affect lipid accumulation of malvidin-3-glucoside (Mv-3glc; the most representative compound of the ACN-rich fraction) and syringic acid (SyAc; metabolic product of Mv-3glc). Cells were incubated with a solution of free fatty acids (500 μM oleic/palmitic acid) and different concentrations (from 0.05 to 10 μg mL-1) of ACN-rich fraction, Mv-3glc and SyAc. Lipid accumulation was measured in a fluorescence spectrophotometer by using the fluorescent dye Nile red and the number of fold increase respect to the control (without fatty acids, FA) was calculated. Results were analysed by ANOVA. Post-hoc analysis of differences between treatments was assessed by the Least Significant Difference (LSD) test with p ≤ 0.05 as level of statistical significance. Lipid accumulation was reduced at all doses of ACN-rich fraction tested with a maximum reduction at 10 μg mL-1 (-27.4%; p<0.0001), while the maximum effect with the single compounds was observed at the concentration of 0.05 μg mL-1 (-63% and -65%, p<0.0001, respectively for Mv-3glc and SyAc). These preliminary results demonstrated a potential role of polyphenol compounds in the regulation of lipid accumulation as evidenced in THP-1 macrophages. Moreover, the effects were observed also at the low doses, supporting a possible contribution at concentrations comparable with those achievable in vivo. The molecular mechanisms involved in such modulation are going to be investigated.