Cell experiment:

MTT assay is used to measure cell growth-inhibitory activity of the selected most promising compounds in HepG2 cell lines. Cells are cultured in 96-well culture plate at 1×104 cells/well. After 24 h cultured at 37 ℃ in the atmosphere of 5% CO2, cells are adhered and treated with different concentrations of the targeted compounds (e.g., Nordihydroguaiaretic acid, 0, 30, 60, 80, 100, 120, and 140 μM) and incubated for 24 h. Then, the supernatants are discarded and MTT (0.5 mg/mL) is added to each well and incubated at 37℃ in 5% CO2 for an additional 4 h. Following, the MTT is removed and 150 μL of formazan in DMSO is added to terminate response and then plates are set to the table shaker for 5 min at low speed. Cell proliferation is evaluated by measuring the absorbance at 570 nm using ELISA Plate Reader. The IC50 values are calculated by SPSS statistics 17.0[2].

Animal experiment:

Mice[3]Seven-week-old male control C57BL/6J mice, male leptin-deficient (ob/ob) mice, and male Pparα-deficient mutant mice (B6.129S4-Pparatm1Gonz/J) are used. These mice are fed a standard chow diet for 1 wk to allow them to acclimatize to a controlled new environment (25±2℃, 55±5% relative humidity with a 12-h light-dark cycle). Subsequently, one group of ob/ob mice is switched to a chow diet supplemented with either low- (0.83 g/kg chow diet) or high-dose (2.5 g/kg chow diet) Nordihydroguaiaretic acid and maintained on this diet for 16 wk. The other groups of ob/ob mice and control mice continue to be fed a normal chow diet for 16 wk. In another set of studies, C57BL/6J mice and Pparα-deficient mutant mice are fed either a high-fat diet (~60% of total calories come from fat), or the same high-fat diet supplemented with a high dose of Nordihydroguaiaretic acid (2.5 g/kg diet). Food intake and body weights are measured once a week throughout the experiment.