Improved Insulin Secretion by Autologous Islet Transplantation, Compared to Oral Antidiabetic Agents, after Distal Pancreatectomy

Glucolipotoxicity Suppressed Autophagy and Insulin Contents in Human Islets, and Attenuation of PERK Activity Enhanced Them in an ATG7-Dependent Manner

BACKGRUOUND

Administration of pancreatic endoplasmic reticulum kinase inhibitor (PERKi) improved insulin secretion and hyperglycemia in obese diabetic mice. In this study, autophagic balance was studied whether to mediate it.

METHODS

Human islets were isolated from living patients without diabetes. PERKi GSK2606414 effects were evaluated in the islets under glucolipotoxicity by palmitate. Islet insulin contents and secretion were measured. Autophagic flux was assessed by microtubule associated protein 1 light chain 3 (LC3) conversion, a red fluorescent protein (RFP)-green fluorescent protein (GFP)- LC3 tandem assay, and P62 levels. For mechanical analyses, autophagy was suppressed using 3-methyladenine in mouse islets. Small interfering RNA for an autophagy-related gene autophagy related 7 (Atg7) was transfected to interfere autophagy.

RESULTS

PERKi administration to mice decreased diabetes-induced P62 levels in the islets. Glucolipotoxicity significantly increased PERK phosphorylation by 70% and decreased insulin contents by 50% in human islets, and addition of PERKi (40 to 80 nM) recovered both. PERKi also enhanced glucose-stimulated insulin secretion (6-fold). PERKi up-regulated LC3 conversion suppressed by glucolipotoxicity, and down-regulated P62 contents without changes in P62 transcription, indicating enhanced autophagic flux. Increased autophagosome-lysosome fusion by PERKi was visualized in mouse islets, where PERKi enhanced ATG7 bound to LC3. Suppression of Atg7 eliminated PERKi-induced insulin contents and secretion.

CONCLUSION

This study provided functional changes of human islets with regard to autophagy under glucolipotoxicity, and suggested modulation of autophagy as an anti-diabetic mechanism of PERKi.

Islet Transplantation Attenuating Testicular Injury in Type 1 Diabetic Rats Is Associated with Suppression of Oxidative Stress and Inflammation via Nrf-2/HO-1 and NF-κB Pathways

Testicular structural and functional impairment is a serious complication in male diabetes mellitus (DM) patients that leads to impaired fertility in adulthood. In contrast to other endocrine therapies, islet transplantation (IT) can effectively prevent and even reverse diabetic nephropathy and myocardial damage. However, whether IT can alleviate diabetes-induced testicular injury remains unclear. In this study, we sought to investigate the effect of IT on diabetes-induced testicular damage. A diabetic rat model was established by streptozotocin injection. DM, IT, and insulin treatment (INS) groups were compared after 4 weeks of respective treatment. We confirmed that IT could effectively attenuate diabetes-induced testicular damage and recover sperm counts more extensively compared with INS in diabetic rats. In addition, significantly higher levels of superoxide dismutase (SOD) activity and lower contents of malondialdehyde (MDA) were detected in the testes of the IT group versus diabetic rats. Mechanism studies revealed that IT significantly activates the expression of Nrf-2, HO-1, and NQO-1 and inhibits upregulation of the NF-κB expression in response to DM, while INS only exhibit slight impact on the protein expression. Therefore, we speculate that IT may prevent the progression of testicular damage by downregulating oxidative stress and inhibiting inflammation via Nrf-2/HO-1 and NF-κB pathways.

Endoscopic Drainage of Pancreatic Fluid Collections

Endoscopy has emerged as a mainstay in the management of pancreatic fluid collections (PFCs), representing an important advance in clinical medicine that has significantly improved the risk-benefit ratio of treating this complex patient population. While endoscopic pseudocyst drainage has generally supplanted surgical and percutaneous approaches, the optimal strategy for walled-off necrosis remains variable and multi-disciplinary despite an emerging trend from randomized trials favoring endoscopy. Although several issues pertaining to endoscopic drainage appear to have been settled - such as the use of endoscopic ultrasound - other pressing questions - including the optimal prosthesis and debridement strategy - remain unanswered, and rigorous investigation is needed. This review aims to provide an evidence-based but practical appraisal of the endoscopic drainage of PFCs through the perspective of the author, with an emphasis on relevant clinical and endoscopic considerations and important research questions.

Liver transaminase levels after intraportal autologous islet transplantation after partial pancreatectomy were associated with long-term metabolic outcomes

AIMS

To investigate the changes of post-procedural liver transaminase levels after autologous islet transplantation (ITx), and their associations with glycemic outcomes.

METHODS

Non-diabetic patients who underwent distal pancreatectomy for benign tumors were enrolled. Islets isolated from the healthy part of the resected pancreas were transplanted via the portal vein. Metabolic parameters were evaluated in the subjects for 5 years.

RESULTS

Eight patients completed the study and four developed postoperative diabetes mellitus (PODM). Disposition index (DI) at postoperative 1 year showed prominent difference between the patients who develop PODM or not: DI was preserved in the PODM-free patients (49.7 ± 4.5 to 70.8 ± 14.4, P = 0.182), while it significantly decreased in the PODM patients (69.3 ± 9.9 to 28.5 ± 3.9, P = 0.019). The preoperative liver transaminase levels were not different between the two groups. However, transient increase in liver transaminase levels during the first week after ITx was observed only in the PODM patients, and their peak values demonstrated significant negative correlation with the changes in DI (r = -0.774 for alanine transaminase, r = -0.759 for aspartate transaminase; P < 0.05).

CONCLUSIONS

Elevation of serum transaminases after ITx could be one of the factors determining insulin secretion and PODM.

Senp2 expression was induced by chronic glucose stimulation in INS1 cells, and it was required for the associated induction of Ccnd1 and Mafa

Post-translational modification by bonding of small ubiquitin-like modifier (SUMO) peptides influences various cellular functions, and is regulated by SUMO-specific proteases (SENPs). Several proteins have been suggested to have diverse impact on insulin synthesis and secretion through SUMO modification in β cells. However, the role of SUMO modification in β cell mass has not been established. Here, we examined the changes in expression of Senp in INS1 cells and pancreatic islets under diabetes-relevant stress conditions and associated changes in β cell mass. Treatment with 25 mM glucose for 72 h induced Senp2 mRNA expression but not that of Senp1 in INS1 cells. Immunohistochemical staining with anti-SENP2 antibody on human pancreas sections revealed that SENP2 was localized in the nucleus. Moreover, in a patient with type 2 diabetes, SENP2 levels were enhanced, especially in the cytoplasm. Senp2 cytoplasmic levels were also increased in islet cells in obese diabetic mice. Cell number peaked earlier in INS1 cells cultured in high-glucose conditions compared to those cultured in control media. This finding was associated with increased Ccnd1 mRNA expression in high-glucose conditions, and siRNA-mediated Senp2 suppression abrogated it. Mafa expression, unlike Pdx1, was also dependent on Senp2 expression during high-glucose conditions. In conclusion, Senp2 may play a role in β cell mass in response to chronic high-glucose through Cyclin D1 and Mafa.