MUC5AC and diabetes mellitus: When digestive enzymes in the small intestine leak across the mucin/epithelial barrier, for example after a high fat meal, several active degrading proteases are detectable in venous blood at levels up to 100 nM.26 In healthy individuals the activity is transient and returns to control values, after about two hours, but in individuals with preconditions, e.g. diabetics, the elevated plasma protease activity prevails over longer periods.