Age-related alteration in the distribution of methylglyoxal and its metabolic enzymes in the mouse brain

Methylglyoxal (MG) is an a-dicarbonyl compound that is naturally produced in vivo through glucose metabolism. In general, MG is metabolized by the glyoxalase 1(GLO1)/GLO2 system and aldose reductase (AR); however, excessive MG can react with proteins and nucleic acids to induce the accumulation of advanced glycation end products (AGEs). Recently, the accumulation of AGEs in the brain has been presumed to be related to neurodegenerative diseases such as Parkinson's and Alzheimer's disease, respectively. Research investigating the role of AGEs in such diseases is ongoing. However, the changes in MG concentration that occur in the brain during healthy ageing remain unclear. Therefore, we performed fractionation of the brains of aged and young mice, measured the MG concentration in each part of the brain, and then examined the distribution. We also investigated the expression levels of GLO1 and AR, the main metabolizing enzymes of MG, in various brain regions, across age groups. We show that MG concentration varies among different regions of the brain, and that MG concentration in aged mice is significantly lower than that in young mice across all regions of the brain, except the brain stem. In addition, although the expression level of the GLO1 protein in the brain did not change with ageing, the expression level of AR was higher in aged than in young mice. Moreover, although a significant positive correlation was observed between GLO1 expression and MG concentration in the brains of young mice, no significant correlations were observed in the brains of aged mice. Meanwhile, the production of protein carbonyls and the accumulation of AGEs were not observed in the brains of aged mice. These results suggest that the accumulation of MG in the brain, along with the carbonyl stress are suppressed and regionally controlled during healthy ageing. This finding is useful as the foundation for further studies to investigate the role and toxicity of MG in various age-related disease conditions.