MMP1 and fatty liver disease: However, leptin overproduction, due to increased adipose tissue, acts as a pro-inflammatory and fibrogenic factor acting on metalloproteinases (TIMP metallopeptidase inhibitor 1 and matrix metalloproteinase-1), stimulating TGF-β, and upregulating CD14 on liver Kupffer cells, thus worsening liver steatosis [24,25,26,27].