MMP9 and obesity due to melanocortin 4 receptor deficiency: The deleterious effects of obesity in experimental models of stroke may be mediated, at least partly, through activation of matrix metalloproteinase (MMP)-9, as high fat diet-induced obesity increases MMP-9 expression in ischaemic murine brain [144, 150] and MMP-9 knockdown reversed the damaging effects of obesity following ischaemic challenge [144].