Metformin improves cognition of aged mice by promoting cerebral angiogenesis and neurogenesis

The cerebral microvasculature is essential for preservation of normal cerebral function. Age-related decreases of neurogenesis and cognitive function are accompanied by reduced blood flow and a decline in neural stem cell (NSC) number. Here, we report that metformin administered by tail vein injection enhanced cognition in aged but not young mice in a dose-dependent manner. Further, metformin restored cerebral blood flow and brain vascular density and promoted neurogenic potential of the subependymal zone/subventricular zone both in vivo and in vitro. RNA-Seq result indicated that metformin could enhance glycolysis in blood, with an increase in relative mRNA expression of the enzyme in the glycolysis pathway from hippocampal tissue of metformin-treated mice. Mechanistically, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme in the glycolysis pathway, may contribute to angiogenic and neurogenic potentials of NSCs. Interestingly, examination of peripheral blood mononuclear cells from people of various ages showed that mRNA expression of GAPDH gradually decreased with age, while its expression level positively correlated with cognitive levels. Our results indicate that metformin represents a candidate pharmacological approach for recruitment of NSCs in aged mouse brain by enhancing glycolysis and promoting neurovascular generation, a strategy that might be of therapeutic value for anti-aging in humans.