LETTER Do

gliadin and tissue transglutaminase mediate PPAR downregulation in intestinal cells of patients with coeliac disease? The accumulation of toxic gliadin peptide was proposed to initiate tissue trans-glutaminase (tTG) upregulation in coeliac intestine.1 Upregulation of tTG drives inflammation through the ubiquitination and proteasomal degradation of the anti-inflammatory peroxisome proliferator-acti-vated receptor (PPAR). To understand further the contribution to mucosal-associated damage in coeliac disease caused by tTG upregulation, we have quantified the expression levels of several proteins directly involved in the PPAR signalling pathway and/or related to PPAR activation. Our study population consisted of patients with coeliac disease at first diagnosis with gut inflam-mation (n1 Marsh 2; n5 Marsh 3; immunoglobulin A (IgA)-tTG $cut-off); IgA-tTG-negative patients with coeliac disease who had recovered from intestinal damage while on a gluten-free diet (GFD) (n4 Marsh 0e1); and control patients with excluded coeliac disease (n7 Marsh 0