BDNF and obesity due to melanocortin 4 receptor deficiency: Recent studies suggested that hyperinsulinemia and insulin resistance are linked to Alzheimer's disease (AD) and the increased amyloid beta-peptide (Abeta) in the brain of HFD-fed mice is associated with reduced brain-derived neurotrophic factor expression, which led to abnormal feeding behavior and increased food intake, resulting in obesity and insulin resistance in these animals, so experimental evidence suggests that alterations in glucose and insulin metabolism may influence the onset of AD through their influence on the synthesis and degradation of Ab peptides [34].