MMP9 and type 1 diabetes mellitus: A recent mouse model study by Horikawa et al. comparing skin dryness in type 1 and type 2 diabetes found that type 1 diabetes increased AGEs and matrix metalloproteinase-9 (MMP-9), leading to a decrease in collagen IV, while type 2 diabetes reduced hyaluronic acid levels and increased inflammatory cytokines levels [61].