Peroxisome proliferator-activated receptor-gamma agonist, pioglitazone prevents early graft loss in canine pancreatic islet auto-transplantation
Yoh Asahi1, Masaomi Ogura1, Masaaki Watanabe1, Hitoshi Ono1, Shin Emoto1, Akihisa Nagatsu1, Hirofumi Kamachi1, Tadashi Yoshida1, Yasuyuki Koshizuka1, Akinobu Taketomi1, Satoru Todo2, Kenichiro Yamashita3.
1Department of Gastroenterological Surgery I, Hokkaido University Graduate School of Medicine, Sapporo, Japan; 2Department of Surgery, St. Marys’ Hospital, Kurume, Japan; 3Department of Transplant Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan
Purpose: After pancreatic islet transplantation (PITx), more than a half of islet grafts are destroyed within 72 hours mainly due to apoptosis induced by non-specific inflammatory responses. The proliferator-activated receptor (PPAR)-gamma is a transcription factor involved in not only lipid/glucose metabolism but also inflammation and immune-responses. It has been shown that ligation of PPAR-gamma inhibits activation of the key pro-inflammatory transcription factor, NF-kappaB. In this study, we examined the effect of PPAR-gamma agonist on islet graft loss in a canine auto-PITx model.
Methods: Diabetes was induced in female beagle dogs by a total pancreatectomy. Follwing isolation from the extracted pancreas, islet grafts were auto-transplanted into the liver through the portal vein. A PPAR-gamma agonist, pioglitazone (PIO), was given orally 1 hour before PITx and twice daily thereafter for 3 days (n=7). Fasting blood glucose level (FBGL) was monitored daily. An intravenous glucose tolerance test (IVGTT) was performed on day 14 after PITx. Isolated canine islet cells (500 IEQ) were cultured together with TNF-alpha, IL-1beta and IFN-gamma, with or without PIO. After 12 hours incubation, islets were examined by MTT and TUNEL assays.
Results: When islets were transplanted at 500, 1000 or 2000 IEQ/kg, FBGL normalized in 0% (0/6), 42.9% (3/7) and 80.0% (4/5) of PITx animals, respectively. In the marginal auto-PITx model (with 1000 IEQ/kg), administration of PIO at 5 mg/kg improved the normo-glycemic rate to 71.4% (5/7). Furthermore, treatment with PIO at 10 mg/kg successfully reverted diabetes in all PITx animals (7/7, p<0.05). The calculated BG-AUC0-120 level upon IVGTT was 18949 ± 553 mg*min/dl in PIO (10 mg/kg) treated islet recipients, which was significantly lower than the control (34758 ± 4315, p<0.01), but was comparable to normal dogs (14194 ± 563) suggesting that islet function was well preserved in PIO treated recipients. After 12 hr-culture, islet count was 406.3 ± 17.3 IEQ. Addition of pro-inflammatory cytokines reduced islets to 324.5 ± 1.3 IEQ, whereas, PIO treatment prevented cytokine-induced islet death (385.8 ± 6.2 IEQ, p<0.05). These results were also confirmed by the MTT assay. The apoptotic index (AI) of islets was 1.1 ± 0.9% after isolation, 4.0 ± 1.2% following 12 hr-culture, and 19.9 ± 0.4% with pro-inflammatory cytokines. In contrast, PIO treatment significantly prevented cytokine-induced islet apoptosis (AI: 7.5 ± 1.1%).
Conclusion: A PPAR-gamma agonist, PIO prevents apoptotic cell death of islets. Three days administration of PIO ameliorates islet graft loss in canine auto-PITx.
15:30 - 17:00
|Getting Beta Cells to Survive: Beta Cell Survival and Injury Mechanisms||Peroxisome proliferator-activated receptor-gamma agonist, pioglitazone prevents early graft loss in canine pancreatic islet auto-transplantation||Plenary Room 1|