Abstract: Objective To study effects of rice germ on glucose tolerance and its mechanism in adult mice.Methods Thirty six-week-old imprinting control region (ICR) mice were divided randomly into control,low- and high-dose rice germ groups.The mice were fed with fundamental feed,10%,and 40% rice germ feed for 4 weeks,respectively.After the treatment,fasting blood glucose (FBG) and insulin (INS) levels were measured,and the insulin sensitivity index (ISI) was calculated.Oral glucose tolerance test (OGTT) was performed.Serum and liver samples were collected to measure the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) enzyme and malondialdehyde (MDA) content.The mRNA expression levels of glucokinase(GCK)in liver tissue and glucose transporter type 4 (GLUT-4) in adipose tissue were determined by real-time quantitative PCR.Results Compared with the control group,the ISI (-2.59±0.33) was higher,the 0.5 h blood glucose (6.75±2.20 mmol/L) and the area under the curve of blood glucose (12.81±3.19) were lower in high-dose rice germ group (all P<0.05).Compared with the control group,the enzymatic activities of GSH-PX (44.34±11.96 U/g protein) and SOD (34.88±7.70 U/g protein) of liver tissue increased,and MDA level (1.57±0.43 nmol/mL) decreased in high-dose rice germ group (all P< 0.05).Compared with the control group,the enzymatic activities of SOD (48.45±2.54 U/g protein,53.27±2.51 U/g protein) increased,and the serum MDA levels (1.44±0.25 nmol/mL,1.46±0.35 nmol/mL) decreased in low- and high-dose rice germ groups (all P<0.05).The GCK mRNA expression of liver tissue increased in high-dose rice germ group (P<0.05),and GLUT-4 mRNA expression of adipose tissue increased in low and high-dose rice germ groups (both P< 0.05).Conclusion Rice germ could improve glucose tolerance in adult mice;the mechanism may related to rice germ's antioxidant activity and ability to regulate the expression of glucose metabolism-related gene.