[The impact of bilberry leaves' polyphenols on the anxiety level, spatial learning and memory of db/db mice]

Numerous experimental and clinical studies have shown high efficiency of plant polyphenolic compounds in restoring age-related memory and learning disorders. In the present study a functional food ingredient (FFI) was obtained by sorption of an aqueous solution of bilberry leaves extract on buckwheat flour, which allowed to concentrate polyphenols and increase their storage stability. The aim of this study was to evaluate the impact of a developed FFI, enriched with bilberry leaves` polyphenols, on the anxiety level, locomotor activity, memory and spatial learning of db/db mice with genetical type 2 diabetes. Material and methods. The experiment was conducted using 10 heterozygote male db/db mice and 10 homozygote male db/+ mice as the comparison control group (7 weeks of age). According to body weight, blood glucose level, the results of insulin resistance test and elevated plus-maze (EPM) test, animals were randomized into three groups: control group C1 - db/+ animals, control group C2 and experimental group G3 - obese db/db mice. Buckwheat flour was included into the diet of C2 group in a dose 22.5 g/100 g; FFI was included into the diet of G3 group in a dose 2.5 g/100 g (that was equal to 59.2± 1.4 mg-eq gallic acid per 100 g of the diet). The anxiety level and general locomotor activity were evaluated in the EPM test. The evaluation of behavior, memory and spatial learning was performed using passive avoidance test (PAT). Glycated hemoglobin level was determined in blood, insulin and leptin levels were determined in blood plasma, general antioxidant activity was determined in liver cytosolic fraction. Results and discussion. The obtained data on biochemical parameters and insulin resistance tests showed the absence of normalizing effects of developed FFI. However, the inclusion of polyphenol-containing FFI into the diet led to beneficial changes in physiological parameters. Animals of G3 group, provided with FFI, were significantly less anxious compared to both control groups. During PAT testing of short-term memory, no animals in G3 group entered to the dark compartment (0%), what demonstrated increased learning ability and well-established memory of these animals in comparison with C1 (50%) and C2 groups (80%). Conclusion. The results prove the effectiveness of bilberry leaves` polyphenols, sorbed on the brown buckwheat flour, in the correction of central nervous system disorders in db/ db mice with genetically altered type 2 diabetes, what points at possible prospect of FFI inclusion in therapeutic products for patients with type 2 diabetes mellitus.