Ginsenoside Re attenuates diabetes-associated cognitive deficits in rats

Objective: This study was designed to investigate the effect of ginsenoside Re (Re) on cognitive functions, oxidative stress and inflammation in streptozotocin-induced diabetic rats. Research design and method: Diabetic rats were treated with Re (40 mg/kg) for 8 weeks, blood glucose and body weight were measured monthly and weekly, respectively. Cognitive performances were evaluated with Morris water maze. Brain was obtained for measurements of TNF-alpha and malondialdehyde (MDA) contents in both temporal cortex and hippocampus, blood was collected for assays of TNF-alpha, MDA and reduced glutathione (GSH) levels. Results: Leaming and memory abilities were significantly (both P<0.01) impaired in diabetic rats, accompanied by the marked (all P<0.01) elevations of TNF-a and MDA levels in temporal cortex and hippocampus. Increment of MDA and decrement of GSH in serum also occurred with significant differences (both P<0.01). Chronic treatment with Re markedly (P<0.05) improved the cognition of diabetic rats, evidenced by the decreased escape latency and the increased percentage of time spent in the target quadrant. Furthermore, Re treatment remarkably (P<0.05) reduced the levels of TNF-a and MDA in both brain areas of diabetic rats. Decline of MDA level and elevation of GSH level in serum were also seen in Re-treated diabetic rats, coupled with decrease in serum glucose level, all with statistically significant differences. Conclusions: Our findings firstly provide the first evidence that ginsenoside Re can remarkably attenuate diabetes-associated cognitive decline, secondly confirm the involvement of oxidative stress and inflammation in the development of cognitive impairment caused by diabetes, finally point toward the potential of ginsenoside Re as an adjuvant therapy to conventional anti-hyperglycemic regimens as well as diabetes-associated cognitive decline. (C) 2011 Elsevier Inc. All rights reserved.