Visceral adipocytes: old actors in obesity and new protagonists in Crohn's disease?

Objective Crohn's disease (CD) is a chronic inflammatory bowel disease characterised by a peculiar accumulation of mesenteric adipose tissue covering the inflamed intestinal wall. Methods The authors characterised different adipose tissue compartments of patients with CD using morphological and molecular techniques and compared them to those of subjects with obesity (OB) and healthy subjects with normal weight (N). Adipose tissue samples were taken from subcutaneous adipose tissue, omental visceral adipose tissue (VAT) and healthy mesenteric depot (hMES), as well as from fat wrapping the affected (unhealthy) intestinal tracts (uhMES). Microarray analyses, validated by real-time quantitative PCR technique, were performed in whole adipose tissue and in isolated adipocytes. Results The morphology of subcutaneous adipose tissue was similar in subjects with CD and those with N. In patients with CD, VAT adipocytes were smaller than those derived from uhMES and hMES and were smaller than VAT adipocytes of subjects with N. The molecular profiles of CD, VAT and uhMES were characterised by upregulation of genes related to inflammation and downregulation of those involved in lipid metabolism. Adipocytes isolated from VAT of subjects with CD and those with OB exhibited similar upregulation of genes involved in inflammation and immunity. VAT adipocytes of patients with CD compared to those of patients with OB also showed a greater upregulation of several anti-inflammatory genes. Conclusion In patients with CD, VAT distant from uhMES is affected by inflammation and displays features similar to those of VAT of patients with severe OB. The small diameter of VAT adipocytes of CD, together with their high expression of anti-inflammatory genes, suggests a potentially protective role for this tissue. VAT adipocytes may play an important role in the pathophysiology and/or activity of CD.