SUMMARY
Objective Brown adipose tissues (BAT) activation is important for losing weight as its high energy expenditure in Mammalian. Recent studies showed that exercise may also be essential for BAT activation. Uncoupling protein 1 (UCP1), specifically expressed in BAT's mitochondria, uncouples oxidative phosphorylation and dissipates energy from Free Fatty Acids into heat. Activating the Adrenergic Receptor ß3 (Adrß3) provides fuel for mitochondrial heat production and up-regulates Cyclooxygenase 2 (COX2), which is a key factor of UCP1 synthesis. Sympathetic nerve excitement stimulated by exercise can release norepinephrine as a neurotransmitter, which can affect Adrß3. Brown adipocyte (BAC) is a kind of adipocyte in vitro as a model to study heat production. Isoprenaline Hydrochloride (ISO) is a widely used as an Adrß agonist. In this research, we tried to figure out the response of BAC to Adrß3 activations with different time points and whether ISO can be used as a BAC activator.Methods C3H10T1/2 cells were maintained in a humidified, 37°C, 5% CO2 incubator in DMEM/F12 medium with 10% fetal bovine serum (FBS). For brown adipogenesis, cells were first split into differentiation medium (DMEM/F12 containing 10% FBS, 20nM insulin, 1nM 3,3’5-Triiodo-L-thyronine(T3)) for 4 days, the medium was changed every other day. Confluent cells were treated for 2 days with brown adipose adipogenesis cocktails (differentiation medium containing 2µg/mL dexamethasone, 0.5mM isobutylmethylxanthine (IBMX), 0.125mM indomethacin and 1µM rosiglitazone) on day 4. Then the medium was replaced by differentiation medium and changed every other day. At day 10, the full differentiation adipocytes were treated with 10µM ISO for 0 (as control), 1, 3, 6, 12 and 24 hours. For the lipid droplets staining, the cells were fixed by 4% paraformaldehyde solution then stained with Oil Red O. The cells were harvested and the total cell lysates were extracted for protein analysis after each time point. The UCP1, COX2, and Adrß3 expression levels were detected by western blot, using Actin as the internal protein. The results were expressed as the mean ± standard error of the mean (SEM). Group comparisons were performed using two-way ANOVA and LSD’s post-hoc tests.Results After differentiation, the cell shapes converted from fibroblastic to a spherical shape. Dispersed small lipid droplets were observed in the cells. After ISO treatment, the red color after Oil Red Staining became lighter and the size of the lipid droplets turned to smaller. The Adrß3 protein expressions were 1.00±0.00, 1.34±0.32, 1.07±0.50, 4.65±1.84*, 2.44±0.73, and 3.43±1.09 at 0h, 1h, 3h, 6h, 12h, and 24h after ISO treatment, respectively. After introduced to ISO, the UCP1 expression levels were 1.00±0.00, 1.95±0.39, 2.72±0.57, 5.68±1.82*, 3.49±0.92, and 2.79±1.05 at 0h, 1h, 3h, 6h, 12h, and 24h, respectively. And for COX2, the protein expressions were 1.00±0.00, 2.13±0.67, 1.82±0.33, 4.67±1.82*, 2.88±0.44, and 2.65±0.54, respectively. The * means p ? 0.05, compared with oh controls. The proteins expressions were reached to peak after 6 hours ISO treatment from the above results.Conclusions UCP1 and COX2 protein expressions were increased in BAC according to Adrß3's expression in different time points, indicating that Adrß3 may induce adipolysis in BAC and help to burn fat and produce heat.