Leptin alleviates intestinal mucosal barrier injury and inflammation in obese mice with acute pancreatitis.

Background/objectives: Obesity is an independent risk factor for severe acute pancreatitis (AP). Leptin plays an important role in energy homeostasis. It has been reported that leptin might also participate in the regulation of the intestinal mucosal barrier and inflammatory response. This study aimed to evaluate the effects of leptin on the intestinal mucosal barrier and inflammatory injury in obese mice with AP.

Subjects/methods: AP was induced in leptin-deficient (ob/ob) or wild type (WT) mice by peritoneal injection of caerulein. The animals were divided into 4 groups: WT mice with or without exogenous leptin injection and ob/ob mice with or without leptin treatment. The inflammatory scoring of the pancreas and intestine were evaluated. Intestinal permeability, ileal interleukin (IL)-6 and IL-1β, proliferation, apoptosis and intestinal expression levels of claudin-1 and occludin were measured.

Results: Pancreatic pathologic scores (8.50 ± 0.96 vs. 3.78 ± 1.35, p < 0.001), pancreatic levels of IL-6 (8.34 ± 3.21 ng/mg vs. 4.99 ± 0.53 ng/mg, p = 0.022), intestinal oedema scores (2.25 ± 0.46 vs. 1.14 ± 0.69, p = 0.001) and intestinal permeability to FD4 (0.78 ± 0.06 μg/ml vs. 0.53 ± 0.11 μg/ml, p < 0.001) were significantly higher in ob/ob mice than those in WT mice. Leptin replacement in ob/ob mice greatly improved the intestinal permeability (FD4 0.66 ± 0.03 μg/ml, vs. 0.78 ± 0.06 μg/ml, p = 0.012), increased the ileal expression of claudin-1(1.07 ± 0.08 vs. 0.83 ± 0.07 relative densitometry, p = 0.001) and reduced intestinal IL-6 and IL-1β to levels comparable to those in WT mice. The pancreatic level of IL-6 in ob/ob mice treated with leptin was also significantly decreased relative to that of untreated ob/ob mice (4.45 ± 1.71 ng/mg vs. 8.34 ± 3.21 ng/mg, p = 0.010).

Conclusions: Obesity may aggravate intestinal inflammation and increase intestinal permeability under the condition of acute pancreatitis. Exogenous leptin supplementation was in favour of anti-inflammation and improvement of intestinal mucosal barrier.