Abstract P045: High Methionine, Low Folate and Vitamin B6/B12 Containing Diet Leads to Cognitive Functions Impairment by Epigenetic Silencing of Netrin Gene

Abstract

Hypermethylation of the genes silence the transcriptions of functional genes associated to cognitive functions. Loss of memory due to epigenetic modifications, called memory-epigenetics was studied. Netrin is a glycoprotein involved in neurogenesis, axonal guidance and maintenance of synaptic plasticity. We hypothesized that high methionine-low vitamins containing diet leads to memory impairment by increasing global DNA methylation and therefore, silencing the netrin gene. Wild type (C57BL/6J) mice were fed diet containing excess met (1.2%), low-folate (0.08 mg/kg), vitamin B6 (0.01 mg/kg), and B12 (10.4 μg/kg) for 6 weeks. Mice were weekly examined for cognitive functions. Our results using a passive avoidance test confirmed a loss in fear motivated long-term memory starting from 4th week that continued up to 6th week of diet (F=37.14, p<0.001). The loss of memory was negatively associated with an increase in global DNA methylation in mice brains fed with diet (R2=-0.99, p<0.001). We found a time-dependent decrease in netrin protein expression (F=27.63, p<0.001) and an increase in methylation of netrin gene promoter, defined by restriction digestion-PCR analysis, in mice fed with diet. The increase in methylation of netrin gene promoter was further validated by high resolution melting and sequencing analysis. In addition, the association of netrin with memory impairment was confirmed by delivering netrin protein to diet-fed mice brains through intracerebral route. The data suggest that netrin introduction helped in considerable memory regain (~50%) in mice on diet. Taken together, these results suggest that high met, low folate and vitamin B6/B12 containing diet can induce defects in learning and memory. Furthermore, the data indicates that decrease in netrin level due to hypermethylation of its gene promoter can be associated with memory loss.