In Streptozotocin (STZ)-induced AD rats model, the levels of apelin/APJ were decreased in the hippocampus, while intraventricular injection of apelin can reduce the activation of glial cells and the expressions of Interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) in the hippocampus to alleviate neuronal damage (Luo et al., 2019). This evidence concerns the gene APLN and Alzheimer disease.