It is widely known that diabetes is a risk factor for dementia. It has been reported that the cognitive function is impaired in the streptozotocin (STZ)-induced diabetic mouse model. Recently, it has also been reported that alteration of the intestinal flora is a risk factor for dementia. However, effects of alteration of the intestinal flora due to dementia on the cognitive function have not been adequately assessed. One of the reasons is that germ-free mice, which have no intestinal flora, need to be housed in a germ-free environment. Therefore, it is difficult to subject to behavioral tests in a germ-free environment to assess the cognitive function.
In the present study, the cognitive function was assessed by a novel object recognition test in a germ-free environment using germ-free mice (C57B6N) in the control group treated with physiological saline and in the STZ group in which diabetes was induced by STZ administration.
In the STZ group, the rate of exploration time to the novel object in the retention trial was significantly lower than in the control group.
In conclusion, STZ-induced diabetic mouse model in a germ-free environment indicated impairment of cognitive function in the novel object recognition test performed in a germ-free environment.