Increased secretion of insulin and proliferation of islet ß-cells in rats with mesenteric lymph duct ligation.

BACKGROUND & AIMS: It has been suggested that intestinal lymph flow plays an important role in insulin secretion and glucose metabolism after meals. In this study, we investigated the influence of ligation of the mesenteric lymph duct on glucose metabolism and islet ß-cells in rats. METHODS: Male Sprague-Dawley rats (10 weeks old) were divided into two groups: one underwent ligation of the mesenteric lymph duct above the cistern (ligation group), and the other underwent a sham operation (sham group). After 1 and 2 weeks, fasting plasma concentrations of glucose, insulin, triglyceride, glucose-dependent insulinotropic polypeptide (GIP), and the active form of glucagon-like peptide-1 (GLP-1) were measured. At 2 weeks after the operation, the oral glucose tolerance test (OGTT) and intravenous glucose tolerance test (IVGTT) were performed. After the rats had been sacrificed, the insulin content of the pancreas was measured and the proliferation of ß-cells was assessed immunohistochemically using antibodies against insulin and Ki-67. RESULTS: During the OGTT, the ligation group showed a significant decrease in the plasma glucose concentration at 120 min (p<0.05) and a significant increase in the plasma insulin concentration by more than 2-fold at 15 min (p<0.01). On the other hand, the plasma GIP concentration was significantly decreased at 60 min (p<0.01) in the ligated group, while the active form of GLP-1 showed a significantly higher level at 90 min (1.7-fold; p<0.05) and 120 min (2.5-fold; p<0.01). During the IVGTT, the plasma insulin concentration in the ligation group was significantly higher at 2 min (more than 1.4-fold; p<0.05). Immunohistochemistry showed that the ratios of ß-cell area/acinar cell area and ß-cell area/islet area, and also ß-cell proliferation, were significantly higher in the ligation group than in the sham group (p<0.05, p<0.01 and p<0.01, respectively). The insulin content per unit wet weight of pancreas was also significantly increased in the ligation group (p<0.05). CONCLUSIONS: In rats with ligation of the mesenteric lymph duct, insulin secretion during the OGTT or IVGTT was higher, and the insulin content and ß-cell proliferation in the pancreas were also increased. Our data show that mesenteric lymph duct flow has a role in glucose metabolism.