HFD-induced obesity also leads to neuroinflammation46; the massive concentration of free fatty acids (which are able to cross the BBB47) enables their binding to specific microglia receptors (e.g., Toll-like receptor-4 [TLR4]), which activates microglia and increases the release of pro-inflammatory cytokines29. The gene discussed is TLR4; the disease is obesity due to melanocortin 4 receptor deficiency.