Anti-adipogenic activity of oleoresin from Nigella sativa L. seeds via modulation of PPAR-γ and C/EBP-α expression in 3T3-L1 adipocytes

The in vitro antiadipogenic properties of oleoresin obtained from Nigella sativa L.(black cumin) seeds was evaluated in this study using 3T3-L1 cells as model cell line. Despite containing beneficial compounds like polyphenols, thymoquinone, flavonoids, and unsaturated fatty acids known for their antioxidant properties, its role in obesity management is not fully understood. We hypothesized that black cumin seed oleoresin treatment would inhibit differentiation of 3T3-L1 preadipocytes by regulating expression of transcription factors, peroxisome proliferator-activated receptor γ (PPAR-γ) and CCAAT enhancer binding protein α (C/EBP-α). Cells were cultured and differentiated for 8 days in Dulbecco modified Eagle media (DMEM) containing 10% fetal bovine serum, both in the absence (control) and presence of 25, 50 and 100 µg/ml oleoresin. Oil red O staining after differentiation revealed a dose-dependent, substantial reduction in lipid droplet accumulation in the differentiated adipocytes treated with oleoresin than differentiated control (DC) group. Molecular analysis revealed downregulation in cellular induction of PPAR-γ, C/EBP-α and sterol regulatory element-binding protein 1 (SREBP1) transcription factors. Furthermore, mRNA expression of particular target genes of these transcription factors— adiponectin, adipocyte fatty acid binding protein (aP2), leptin and fatty acid synthase (FAS) was also dose dependently inhibited in differentiated adipocytes by oleoresin treatment. The activation of adenosine monophosphate protein kinase (AMPK) and phosphorylation of its substrate acetyl-CoA carboxylase (ACC) was detected by western blotting showing a significant increase in their phosphorylated protein levels. Collectively, these findings suggest that black cumin seed oleoresin showed anti-obesity effects by inhibiting lipid droplet formation and modulating molecular pathways involved in adipogenesis, highlighting its potential as a natural therapeutic agent for obesity and related metabolic disorders.