Citrus sunki Peel Extract, Containing Nobiletin and Tangeretin, Enhances Proliferation and Differentiation in 3T3-L1 Adipocytes

Abstract

In this experiment, effects of Citrus sunki peel extract (CPE) on proliferation and differentiation of 3T3-L1 cells were analyzed. Citrus sunki peel was extracted with ethanol to obtain CPE. Results of measuring DPPH and hydrogen peroxide radical scavenging activity revealed that CPE had an antioxidant ability. The 3T3-L1 cells were cultured in the basal medium (C) or with 0.05% dimethyl-sulfoxide (CDMSO) or with 50, 100, 200, 300, and 400 μg/mL CPE (CPE50, CPE100, CPE200, CPE300, and CPE400, respectively). As a result of cell counting and MTS assay, CPE significantly enhanced proliferation capacity of 3T3-L1 cells. To analyze the effect of CPE on the differentiation capacity of 3T3-L1 cells, relative gene and protein expression levels of Cebpb, Cebpa, and FASN related to adipogenesis were measured by RT-qPCR and Western blot. CPE increased adipogenesis-related gene and protein expression in 3T3-L1 cells, with CPE300 being especially effective. In Oil Red O staining, adipogenesis was significantly greater in CPE200, CPE300, and CPE400 than in C. This was confirmed image wise through Nile Red staining. Through HPLC analysis, it was confirmed that nobiletin and tangeretin were most abundant in CPE. To analyze effects of nobiletin and tangeretin on 3T3-L1 cells, the cells were cultured with various concentrations of nobiletin, tangeretin, and both. As a result of cell counting and MTS assay, nobiletin and tangeretin significantly decreased the proliferation capacity of 3T3-L1 cells. In RT-qPCR, western blot, Oil Red O staining, and Nile Red staining to analyze differentiation capacity, nobiletin and tangeretin significantly enhanced the expression of genes and proteins related to adipogenic differentiation compared to the control group. In conclusion, CPE, which had high antioxidant capacity, enhanced proliferation and differentiation in 3T3-L1 adipocytes. This improvement in differentiation is due to the influence of nobiletin and tangeretin contained in CPE.