I was surprised initially when I read that gluten ingestion actually increased the production of zonulin in some people...that there was a direct link there. I can't remember off hand, but have found it in print in the past. YOu can start by looking at the zonulin thread in TGF, there are some full text articles if you click on the links, others are abstracts. We'll be able to find it...just a matter of finding it.
http://jccglutenfree.googlepages.com/zonulin
Cara