Vitamin B12-folic acid supplementation regulates neuronal immediate early gene expression and improves hippocampal dendritic arborization and memory in old male mice

Abstract

As the relationship among diet, brain aging and memory is complex, it provides ample opportunity for research in multiple directions including behaviour, epigenetics and neuroplasticity. Nutritional deficiencies together with genetic and environmental factors are the major cause of many age-associated pathologies including memory loss. A compromised vitamin B12-folate status in older people is highly prevalent worldwide. Researchers have established a close association between the adequate level of B12-folate and the maintenance of cognitive brain functions. One of the main reasons for age-associated memory loss is downregulation of neuronal immediate early genes (nIEGs). Therefore, we hypothesize here that vitamin B12-folic acid supplementation in old mice can improve memory by altering the expression status of nIEGs. To check this, 72-week-old male Swiss albino mice were orally administered with 2 μg of vitamin B12 and 22 μg of folic acid/mouse/day for eight weeks. Such supplementation improved recognition memory in old and altered the expression of nIEGs. The expression of nIEGs was further found to be regulated by changes in DNA methylation at their promoter regions and CREB phosphorylation (pCREB). In addition, Golgi-Cox staining showed significant improvement in dendritic length, number of branching points and spine density of hippocampal CA1 pyramidal neurons by B12-folic acid supplementation. Taken together, these findings suggest that vitamin B12-folic acid supplementation regulates nIEGs expression and improves dendritic arborization of hippocampal neurons and memory in old male mice.