Neuroprotective properties of GABA and its derivatives in diabetic encephalopathy in old animals

Abstract

The aim of the work was to evaluate the GABA neuroprotective properties and its structural analogues in old animals after seven months of hyperglycemia. Materials and methods. Diabetes mellitus was modeled in white outbred male rats (12 months old) by the administration of a streptozotocin (65 mg/kg) and nicotinamide (230 mg/kg) combination. After 6 months, the animals with a postprandial glycemia level between 11 and 18 mmol/l were selected for the study. After the groups had been formed, the animals were administrated with GABA and GABAergic compounds (Compositions МРВА and PPC), respectively, for 1 month, the control group animals were administrated with saline. After the treatment, an oral glucose tolerance test and a set of behavioral tests aimed at studying sensory-motor (Open Field, Adhesion test, Rotarod) and cognitive functions (New Object Recognition and Morris Water Maze), as well as the functional state evaluation of the endothelium were performed. Further on, sampling of blood and brain tissues for a biochemical and enzyme immunoassay (the level of glucagon-like peptide-1 (GLP-1) and TNF-α in serum and the level of Klotho protein, BDNF, Nrf2, NF-κB and malondialdehyd (MDA) in brain homogenates), as well as a morphological analysis of changes in CA1 and CA3 neurons of the hippocampus and somatosensory cortex, was carried out. Results. GABA and compositions with its derivatives had a pronounced neuroprotective effect in old animals with prolonged hyperglycemia. The hypoglycemic effect of the studied compositions was accompanied by an increase in the production of GLP-1. In the animals with DM, after 6 weeks of the test substances administration, higher rates of sensory-motor and cognitive functions and a less structural damage to the sensory-motor cortex and the brain hippocampus were recorded. These effects may be due to higher levels of the Klotho proteins, Nrf2 and BDNF, as well as lower levels of NF-κB, which may underlie the suppression of the oxidative stress, the reduction of MDA and inflammation (TNF-α). Conclusion. After 6 weeks of the administration, GABA and its compositions in old animals (19 months old) significantly improved sensory-motor and cognitive functions, reduced negative structural changes in the hippocampus and somatosensory cerebral cortex.