Diabetes Impairs Wnt3 Protein-induced Neurogenesis in Olfactory Bulbs via Glutamate Transporter 1 Inhibition

Diabetes is associated with impaired cognitive function. Streptozotocin (STZ)-induced diabetic rats exhibit a loss of neurogenesis and deficits in behavioral tasks involving spatial learning and memory; thus, impaired adult hippocampal neurogenesis may contribute to diabetes-associated cognitive deficits. Recent studies have demonstrated that adult neurogenesis generally occurs in the dentate gyrus of the hippocampus, the sub ventricular zone, and the olfactory bulbs (OB) and is defective in patients with diabetes. We hypothesized that OB neurogenesis and associated behaviors would be affected in diabetes. In this study, we show that inhibition of Wnt3-induced neurogenesis in the OB causes several behavioral deficits in STZ-induced diabetic rats, including impaired odor discrimination, cognitive dysfunction, and increased anxiety. Notably, the sodium- and chloride-dependent GABA transporters and excitatory amino acid transporters that localize to GABAergic and glutamatergic terminals decreased in the OB of diabetic rats. Moreover, GAT1 inhibitor administration also hindered Wnt3-induced neurogenesis in vitro. Collectively, these data suggest that STZ-induced diabetes adversely affects OB neurogenesis via GABA and glutamate transporter systems, leading to functional impairments in olfactory performance.