Insulin receptors in the CA1 field of hippocampus and selected blood parameters in diabetic rats fed with bilberry fruit

Abstract

Introduction. Bilberry fruit is believed to be a promising factor in the treatment of diabetes mellitus. Chronic hyperglycaemia affects the function of the central nervous system, which may be manifested as changes in hypothalamic insulin signalling. Materials and method. Using DPPH and ABTS assays, total phenolic content in bilberry fruit and its antioxidant activities were examined. The selected biochemical parameters of blood (glucose, fructosamine, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides), as well as the expression of insulin receptors, were studied in the hippocampal CA1 field of healthy and diabetic (streptozotocin-induced; 60 mg kg-1 body weight) Wistar rats fed with bilberry fruit (16 g kg-1 body weight per day; 6 weeks), as well as of the corresponding control groups. Results. Biochemical analyses revealed ambiguous results, but a significantly (P<0.05) decrease in the level of LDL-cholesterol was observed in the group of healthy rats supplemented with bilberry pulp after 6 weeks of the treatment. There was also a difference (P<0.05) in the level of LDL-cholesterol in the mentioned healthy animals fed with bilberry, versus the healthy control group. An increased number of insulin receptors-immunoreactive neurons as well as nerve fibres in the CA1 field of diabetic rats fed with bilberry fruit was also found. Conclusions. An inclusion of bilberry fruit in the daily diet during the course of diabetes can lead to plasticity of hippocampal neurons/nerve fibres, manifested by changes in insulin receptors expression. Whether or not the observed changes had protective effects (by reducing damages caused by diabetes mellitus) on the function of the central nervous system neurons needs further study.

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“…After euthanasia (decapitation), the rats’ brains were stored in 10% buffered formalin (pH = 7) for 12 h at 4 °C, hydrated in decreasing concentrations of ethyl alcohol, and embedded in paraffin blocks in accordance with the previously described method [ 27 ]. Briefly, the paraffin blocks were cut into 5 μm-thick sections which were placed on silanized glass-slides (SuperFrostPlus, Thermo Fisher Scientific, Braunschweig, Germany).…”