Materials and methods
Experimental animals
10-Week-old male KKAy mice (n = 20) were purchased from Beijing Huafukang Biology Technology Co. Ltd (Approval number: SCXK Beijing-2009-0004). Mice were housed individually in cages at a temperature (22 ± 1 °C), humidity (50 ± 10%) with illumination for 12 h in a specific pathogen-free (SPF) environment. The experiment was carried out according to the European Community Guidelines for the Use of Experimental Animals.