SMAD7 and inflammatory bowel disease: In this context, we have previously shown that, in IBD mucosa, there are diminished activity of TGF-β1 due to elevated levels of Smad7, an intracellular inhibitor of TGF-β1 signaling (5), and reduced content of Sirt1, a deacetylase that controls negatively expression of various intracellular proteins (10).