Inflammatory alterations in mesenteric adipose tissue in Crohn's disease

Background & Aims: Abnormalities of fat in the mesentery including adipose tissue hypertrophy and fat wrapping have been long recognized on surgical s pecimens as characteristic features of Crohn's disease. However, the import ance, origin, and significance of the mesenteric fat hypertrophy in this ch ronic inflammatory disease am unknown. Peroxisome proliferator-activated re ceptor gamma (PPAR gamma) is a crucial factor involved in the homeostasis o f adipose tissue, a major source of biologically active mediators. Methods: Intraabdominal fat accumulation was quantified using a magnetic resonance imaging method in patients with Crohn's disease and controls. PPAR gamma an d inflammatory cytokines synthesized by mesenteric adipose tissues were ass essed by quantitative polymerase chain reaction, in situ hybridization, and immunohistochemistry. Results: In vivo, patients with Crohn's disease have an important accumulation of intra-abdominal fat. This mesenteric obesity, present from the onset of the disease, is associated with overexpression o f PPAR gamma and tumor necrosis factor (TNF)-alpha, synthesized, at least i n part, by adipocytes. Conclusions: These results suggest that confined inc reased PPAR gamma mesenteric concentrations could lead to the mesenteric fa t hypertrophy, which could actively participate through the synthesis of TN F-alpha in the inflammatory response.