Studies have also indicated that FGF21 can protect the BBB through the FGF21/FGFR1/KLB signal axis, and alleviate neurological injury and prevent cognitive decline by repairing brain mitochondrial damage, altering hippocampal synaptic plasticity and ameliorating cell apoptosis 17, 19, 53, 62. The gene discussed is KLB; the disease is Mental deterioration.