LEP and obesity due to melanocortin 4 receptor deficiency: Several animal and clinical studies demonstrated that obesity is linked with pathophysiological changes (e.g., metabolic dysfunction, insulin resistance, leptin resistance, systemic inflammation, and adiponectin dysregulation), which result in the reduction of neurotrophic factors, neurogenesis, angiogenesis, and consequently lead to cognitive impairment [12,13,15,16,17].