Leptin, a protein with a cytokine-like structure, is produced predominantly by adipocytes. It appears to play a key role in immune responses by increasing the secretion of Th1 and pro-inflammatory cytokines. As fat-wrapping is a characteristic feature of Crohn's disease (CD), and as increased leptin levels have been reported in animal models of intestinal inflammation, this study investigated whether mesenteric adipose tissue could be a source of leptin in human inflammatory bowel disease (IBD).

To quantify the expression of leptin mRNA in mesenteric adipose tissue of patients with CD or ulcerative colitis (UC).

Specimens were obtained from mesenteric white adipose tissue close to healthy and inflammatory small intestine and/or colon in patients with CD or UC and, for controls, from apparently healthy mesentery of patients operated for carcinoma of the right colon. The expression of leptin mRNA was assessed by reverse transcription-competitive polymerase chain reaction.

Leptin mRNA levels were significantly higher in mesenteric adipose tissue of CD and UC patients than in controls (P ≪ 0.05). In CD and UC, concentrations were not significantly different in mesenteric fat specimens, whether contiguous to macroscopically normal or grossly abnormal intestine.

This study provides the first evidence of a novel abnormality of the mesentery of patients with IBD. Overexpression of leptin mRNA in mesenteric adipose tissue may contribute to (a) the inflammatory process, (b) enhancement of mesenteric TNFα expression in CD (as recently reported), and/or (c) the anorexia frequently reported during flares of IBD.