Protective Effects Of Pre-germinated Brown Rice Diet On Low-levels Of Pb Induced Learning And Memory Deficits In Developing Rat

Objective : Lead (Pb) is a known neurotoxicant in humans and experimental animals. Numerous studies have provided evidence that humans, especially young children, and animals chronically intoxicated with low levels of Pb show learning and memory impairments. Unfortunately, Pb-poisoning cases continue to occur in many countries. Because the current treatment options are very limited, there is a need for alternative methods to attenuate Pb toxicity. Therefore, the effects of feeding three rice diets (WR, BR and PR) on learning and memory impairment induced by Pb in weaning rats were evaluated in this study. This study provides a regimen to reduce Pb-induced toxicity, especially future learning and memory.Methods:1 In this study, the weaning (postnatal day 21, PND21) rats were randomly divided into five groups: the control group (AIN-93G diet, de-ionized water), the lead acetate (PbAC) group (AIN-93G diet, 2g/L PbAC in de-ionized water), the lead acetate+WR group (white rice diet, 2g/L PbAC in de-ionized water; PbAC+WR), the lead acetate+BR group (brown rice diet, 2g/L PbAC in de-ionized water; PbAC+BR) and the lead acetate+PR group (pre-germinated brown rice diet, 2g/L PbAC in de-ionized water; PbAC+PR). The animals received the different diets until PND60, and then the experiment were terminated.2 The protective effects of pre-germinated brown rice (PR) on Pb-induced learning and memory impairment in weaning rats were assessed by the Morris water maze and one-trial-learning passive avoidance test.3 The lead levels in the sera and hippocampi were measured by atomic absorption spectrophotometry. 4 The GABA and glutamate levels were quantified by highperformance liquid chromatography.5 Measurement of oxidative stress state: The levels of reactive oxygen species (ROS) was determined by flow cytometry. The activities of anti-oxidase glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), and the levels of malonaldehyde (MDA) in sera and hippocampi were determined using biochemical methods. The levels of 8-hydroxy-2-deoxyguanosine (8-OHdG) were determined by HPLC.6 Theδ-aminolevulinic acid concentration was measured using biochemical methods.Results:1 The levels of Pb in sera and hippocampi of rats on different diets. The Pb levels in sera and hippocampi of rats after PbAC treatment were significantly increased compared with the control (P<0.05), respectively. The Pb levels in sera and hippocampi of rats on BR and PR diet were decreased significantly compared with that of PbAC group (P<0.05), respectively.2 Effects of feeding different diets on Pb induced learning and memory abilities.The water maze task showed that the escape latencies of rats in both PbAC and PbAC+WR groups were increased significantly compared with the control (P<0.05). The escape latencies of rat in both PbAC+BR and PbAC+PR groups were reduced significantly compared with that of the PbAC group (P<0.05).One-trial-learning passive avoidance test showed that the step-through latencies of rats in PbAC, PbAC+WR and PbAC+BR groups were increased significantly compared with the control (P<0.05), respectively. The step-through latencies of rats in both PbAC+BR and PbAC+PR groups were reduced significantly compared with that of the PbAC group (P<0.05), respectively.3 Effects of feeding different diets on GABA and glutamate content in rat hippocampi. The GABA levels in hippocampi of rats in PbAC+BR and PbAC+PR groups were significantly increased compared with PbAC group (P<0.05), respectively. The glutamate levels in hippocampi of rats in PbAC group were significantly increased compared with the control (P<0.05).4 Effects of feeding different diets on oxidative stress levels.The ROS levels of rats in PbAC group were significantly increased compared with that of the control (P<0.05). The ROS levels of rats with different rice-diet including PbAC+WR, PbAC+BR and PbAC+PR were decreased significantly compared with that of PbAC group (P<0.05).The GSH-Px and SOD activities in sera and hippocampi from PbAC treated animals fed with different diets were decreased compared with those of the control (Table 1). The GSH-Px and SOD activities in sera of rats in PbAC treatment groups feeding different rice diets (PbAC+WR, PbAC+BR and PbAC+PR) were significantly increased (P<0.05) compared with those of PbAC-fed animals. The SOD activities in hippocampi of rats in the PbAC+BR and PbAC+PR groups were significantly increased compared with that of the PbAC group (P<0.05). The MDA levels in sera from rats fed with the normal diet (PbAC) and rice diet groups (PbAC+WR and PbAC+BR) significantly increased compared with the control (P<0.05). However, the levels of MDA were not increased significantly in the PbAC+PR group compared with the control. The MDA levels in sera from PbAC+WR-, PbAC+BR- and PbAC+PR-treated animals were reduced significantly compared with that of the PbAC group (P<0.05), but no significant changes were seen in the hippocampi from rats on the different diet groups.The 8-OHdG levels in Hippocampal DNA of rats in PbAC group were significantly increased compared with that of the control (P<0.05). The 8-OHdG levels in Hippocampal DNA of rats with different rice-diet including PbAC+WR, PbAC+BR and PbAC+PR were decreased significantly compared with that of PbAC group (P<0.05), respectively.5 Effects of feeding different diets on the levels ofδ-aminolevulinic acid in sera. After Pb treatment, theδ-aminolevulinic acid levels were significantly increased compared with the control (P<0.05). Theδ-aminolevulinic acid levels in sera of rats in PbAC+BR and PbAC+PR groups were significantly decreased compared with PbAC group (P<0.05), respectively.Conclusions:1 The BR and PR diets might prevent the Pb accumulation to some degree.2 The PR diet might improve the learning and memory deficits induced by low-level lead in developing rats.3 The effects of PR diet improved learning and memory deficits induced by low-level lead in developing rats may be related with the high levels of GABA in PR and the antagonistic action to the oxidative stress levels.