PPARG and obesity due to melanocortin 4 receptor deficiency: Several olive leaf constituents have been reported to exert beneficial effects against obesity both in vitro and in vivo. Oleuropein [23, 26], hydroxytyrosol [26, 27], luteolin [28], apigenin [29, 30], rutin [31], and caffeic acid [32] were found to decrease the accumulation of intracellular lipid, as detected by Oil Red O staining, and the expression of adipogenic transcription factors such as PPARγ and C/EBPα in 3T3-L1 cells.