Evaluation of effect of Ninjin'yoeito on regional brain glucose metabolism by 18F-FDG autoradiography with insulin loading in superaged mice

1611 Objectives: With a globally aging population, health issues caused by aging and age-related diseases have become inevitable challenges in all countries. Ninjin’yoeito (NYT, Ren-Shen-Yang-Rong-Tang) is a traditional Japanese medicine (Kampo medicine) and a formulation composed of 12 crude drug extracts. It is used for individuals with deteriorating physical or psychiatric conditions, particularly among the elderly. A recent clinical study revealed that NYT may potentially improve cognitive outcome and Alzheimer’s disease (AD)-related depression in patients with AD. However, the mechanism by which NYT exerts its effect on elderly patients remains unclear. The aim of this study is to evaluate the effect of Ninjin9yoeito on regional brain glucose metabolism by 18F-FDG autoradiography with insulin loading in superaged wild-type mice. Methods: Male C57BL/6J mice (72 weeks old) were fed an original diet (CRF-6). After 12 weeks (84 weeks old), mice were randomly assigned to the control and treated groups. The mice in the control group were continued on the original diet (100% CRF-6). The mice in the treatment group were fed the original diet with NYT (97% CRF-6 mixed with 3% NYT). After 12 weeks (96 weeks old), all mice were fasted overnight and then further divided into two subgroups without and with insulin loading in both the control and NYT-treated groups (n=6, each group). The mice in the insulin-loaded groups were intraperitoneally injected with human insulin (2 U/kg body weight) 30 min prior to 18F-FDG injection. Ninety minutes later, the animals were sacrificed, then brains were rapidly removed, placed in Brain Matrix and cut into 9-10 coronal slices (2 mm/slice). The slices were exposed to a phosphor imaging plate with a set of calibrated standards. The radioactivity concentration in each region of interest (ROI) was determined per unit area, and the percentage of injected dose per pixel of the cortex, striatum, thalamus, and hippocampus was obtained and normalized to the animal weight [%ID/pixel/kg body weight (%ID/p/kg)]. Blood samples for glucose concentration measurement were obtained from all groups. Results: The body weight and blood glucose concentration were not significantly different between the control and NYT-treated groups. The levels of 18F-FDG accumulation in the cortex, striatum, thalamus, and hippocampus were also not significantly different between these two groups. In the control group, the blood glucose concentration significantly decreased after insulin loading (p<0.0001). The level of 18F-FDG accumulation in the cortex significantly decreased after insulin loading (p<0.05). In NYT-treated group, the blood glucose concentration also significantly decreased after insulin loading (P < 0.0001). However, the levels of 18F-FDG accumulation in the striatum and hippocampus tended to increase after insulin loading. The levels of 18F-FDG accumulation in the cortex were higher in the NYT-treated group than in the control group after insulin loading. The levels of 18F-FDG accumulation in the striatum were significantly higher in the NYT-treated group than in the control group after insulin loading (P < 0.05). The 18F-FDG accumulation showed negative changes in the cortex, striatum, thalamus, and hippocampus in the control group, whereas positive changes were observed in the NYT-treated group. Conclusions: Ninjin9yoeito could improve the glucose metabolic dysfunction in brain regions in superaged mice. Ninjin9yoeito may potentially reduce insulin resistance in the brain regions in superaged mice, thereby preventing age-related brain diseases.