N. Ogawa

Possible involvement and the mechanisms of excess trans-fatty acid consumption in severe NAFLD in mice

BACKGROUND & AIMS Excessive trans-fatty acids (TFA) consumption has been thought to be a risk factor mainly for coronary artery diseases while less attention has been paid to liver disease. We aimed to clarify the impact of TFA-rich oil consumption on the hepatic pathophysiology compared to natural oil. METHODS Mice were fed either a low-fat (LF) or high-fat (HF) diet made of either natural oil as control (LF-C or HF-C) or partially hydrogenated oil, TFA-rich oil (LF-T or HF-T) for 24 weeks. We evaluated the liver and body weight, serological features, liver lipid content and composition, liver histology and hepatic lipid metabolism-related gene expression profile. In addition, primary cultures of mice Kupffer cells (KCs) were evaluated for cytokine secretion and phagocytotic ability after incubation in cis- or trans-fatty acid-containing medium. RESULTS The HF-T-fed mice showed significant increases of the liver and body weights, plasma alanine-aminotransferase, free fatty acid and hepatic triglyceride content compared to the HF-C group, whereas the LF-T group did not differ from the LF-C group. HF-T-fed mice developed severe steatosis, along with increased lipogenic gene expression and hepatic TFA accumulation. KCs showed increased tumor necrosis factor secretion and attenuated phagocytotic ability in the TFA-containing medium compared to its cis-isomer. CONCLUSIONS Excessive consumption of the TFA-rich oil up-regulated the lipogenic gene expression along with marked hepatic lipid accumulation. TFA might be pathogenic through causing severe steatosis and modulating the function of KCs. The quantity and composition of dietary lipids could be responsible for the pathogenesis of non-alcoholic steatohepatitis.

Attenuation of cross-talk between the complement and coagulation cascades by C5a blockade improves early outcomes after intraportal islet transplantation.

Background. Complement 5a factor (C5a) elicits a broad range of proinflammatory effects, including chemotaxis of inflammatory cells and cytokine release. C5a is also linked to the coagulant activity in autoimmune diseases. Therefore, C5a most likely plays a crucial role in the instant blood-mediated inflammatory reaction. Methods. Intraportal transplantation of 2.5 islet equivalents/g of syngeneic rat islet grafts was performed in two groups of streptozotocin-induced diabetic rats: controls and C5a inhibitory peptide (C5aIP)-treated group. Results. The thrombin-antithrombin complex was significantly suppressed in the C5aIP group (P=0.003), and both the curative rate and the glucose tolerance were significantly improved in the C5aIP group (P<0.05 and P<0.005, respectively). Expression of tissue factor on granulocytes in recipient livers was up-regulated 1 h after islet infusion (P<0.0001), which was significantly suppressed by C5aIP (P<0.005). However, C5aIP was unable to regulate tissue factor expression on isolated islets. Furthermore, no differences were detected between the groups, regarding infiltration of CD11b-positive cells and deposition of C5b-9 on the islet grafts. Conclusions. These data suggest that C5aIP attenuates cross-talk between the complement and coagulation cascades through suppressing up-regulation of tissue factor expression on leukocytes in recipient livers but not on islet grafts, a process leading to improvement in islet engraftment. Therefore, C5aIP in combination with conventional anticoagulants could be a strong candidate strategy to control the instant blood-mediated inflammatory reaction induced in clinical islet transplantation.

Brain death in combination with warm ischemic stress during isolation procedures induces the expression of crucial inflammatory mediators in the isolated islets.

Tissue factor (TF) and monocyte chemoattractant protein-1 (MCP-1) expressed on the islets have been identified as the main trigger of the instant blood-mediated inflammatory reaction (IBMIR) in islet transplantation. Because the key steps that directly induce TF and MCP-1 remain to be determined, we focused on the influence of brain death (BD) on TF and MCP-1 expression in the pancreatic tissues and isolated islets using a rodent model. TF and MCP-1 mRNA levels in the pancreatic tissues were similar between the BD and the control group. However, TF and MCP-1 mRNA in the fresh islets of the BD group were significantly higher than that of the control group (p < 0.01). BD may thus be suggested to be of great importance as an initiator of TF and MCP-1 induction in the isolated islets. Furthermore, the upregulation of crucial inflammatory mediators induced by BD could be exacerbated by warm ischemic damage during digestion procedures. In the present study, the islet yield and purity were affected by BD. However, almost no influences were observed with respect to islet viability, indicating that the expression of inflammatory mediators rather than islet viability is more susceptible to BD. According to the change in time course of TF and MCP-1 expression in the isolated islets, the selected time point for islet infusion in current clinical islet transplantation was thus shown to be at its worst level, at least with respect to the damage caused by BD and ischemic stress. In conclusion, BD in combination with warm ischemic stress during isolation procedures induces a high expression of TF and MCP-1 in the isolated islets. In order to reduce the expression of crucial inflammatory mediators in the islet grafts, the management of the pancreas from brain-dead donors with early anti-inflammatory treatments is thus warranted.

A Novel Predictive Method for Assessing the Quality of Isolated Pancreatic Islets Using Scanning Electrochemical Microscopy

INTRODUCTION The current methods for evaluating islet potency are not useful in clinical transplantation. Therefore, we need reliable, rapid methods enabling accurate prediction of islet quality. MATERIALS AND METHODS We evaluated respiratory activity using scanning electrochemical microscopy (SECM), glucose-stimulated respiratory activity, glucose-stimulated insulin release, ADP/ATP assays, insulin/DNA levels, and Trypan blue exclusion tests as predictive methods for the ability of isolated rat islets to cure syngeneic diabetic rats. RESULTS Although glucose-stimulated respiratory activity, basal respiratory activity, ADP/ATP ratio, and glucose-stimulated insulin release were significantly correlated with the outcome of transplantation into diabetic rats, there was no correlation between outcomes, insulin/DNA ratios, and Trypan blue exclusion tests. The glucose-stimulated respiratory activity in islet preparations that could cure diabetic rats was significantly greater than those unable to cure diabetes. Rat islets with >1.5-fold glucose-stimulated respiratory activity consistently cured diabetic rats, whereas those with a value <1.5 hardly cured any rats. CONCLUSION Measurement of the glucose-stimulated respiratory activity using SECM technique is a novel method that may be useful as a rapid, potent predictor of the outcome of clinical islet transplantation.

Superiority of Fresh Islets Compared With Cultured Islets

INTRODUCTION It has recently been reported that the outcomes of islet transplantation with short periods of culture are comparable with those of freshly isolated islets. To clarify the influence of culture, fresh islets were compared with cultured islets in terms of quality. MATERIALS AND METHODS The quality of freshly isolated islets was compared with that of cultured islets with CMRL 1066 including 10% allogeneic serum, CMRL 1066 including 0.5% human serum albumin, or Miami medium. We evaluated static glucose stimulation tests, insulin/DNA contents, ADP/ATP ratios, and an intraportal transplantation model into syngeneic diabetic rats. The expression of inflammatory mediators in the islets was examined using Western blotting for tissue factor (TF), which is the initiator of detrimental instant, blood-mediated, inflammatory reactions (IBMIR). RESULTS Although the survival rate was similar in all groups, the stimulation index upon glucose challenge and the insulin/DNA ratio were significantly higher among fresh islets. Most importantly, the expression of TF on islets was significantly lower in fresh islets, suggesting that culture enhanced TF-dependent IBMIR after transplantation. In an in vivo transplantation model, the curative rate and insulin production by the recipient liver was considerably greater in the fresh islet group. CONCLUSIONS Isolated islets without prior culture showed results superior to cultured islets.

Optimization of a Prominent Oxygen-Permeable Device for Pancreatic Islets

BACKGROUND We have demonstrated a culture bag system that is useful for pancreatic islet transplantation. To improve and simplify islet transplantation procedures from culture to transplantation, we developed a novel device specific for both islet culture and transplantation (TUBERO Device [TD]) using an oxygen-permeable material. MATERIALS AND METHODS Porcine islets with 30 minutes warm ischemia time were cultured for 24 hours at 37 degrees C in 5% CO2 and humidified air under three different procedures: (1) ordinary culture flask, (2) culture bag suitable for platelets, and (3) TD. Loss of islets during culture, glucose-stimulated insulin release as an islet functional test, and ADP/ATP ratio as an index of islet viability tests were evaluated to compare the devices. TD was further applied in two clinical islet transplantations using non-heart-beating donors in Japan. RESULTS The loss of islets during culture was considerably lower in the TD group. The stimulation index upon glucose challenge tests was significantly higher in the TD group than the others. The ADP/ATP ratio in TD group was significantly lower than that in the ordinary flask group, suggesting that the apoptotic islets were relatively lower among TD. Most importantly, TD was successfully applied both in the clinical islet cultures and in transplantation, resulting in excellent graft function. CONCLUSIONS We propose that the TD, a novel product, not only simplifies islet transplantation procedures, but also maintain the quality of isolated islets.

The Impact of Ischemic Stress on the Quality of Isolated Pancreatic Islets

BACKGROUND Although the ischemic stress of donated organs has been shown to have strong negative effects on islet recovery, the impact on islet quality remains uncertain. In the present study, therefore, we examined the influence of ischemic stress on the expression of inflammatory mediators among isolated islets. MATERIALS AND METHODS Islets were isolated from adult porcine pancreata subjected to 16-hour cold ischemia time (CIT) in addition to 40-minute warm ischemia time (WIT). We evaluated the islet yield, islet loss during the first 24 hours in culture, adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio, ATP/DNA ratio, glucose-stimulated respiratory activity, in vivo bioassay, and the expression of inflammatory mediators (tissue factor [TF], [MCP-1], macrophage migration inhibitory factor) on the isolated islets. We also analyzed ATP/DNA ratios of the exocrine tissues during isolation procedures. RESULTS The islet yield, survival rate during culture, and glucose-stimulated respiratory activity were significantly lower in cases of 16-hour CIT plus 40-minute WIT compared with the control group (P < .0001, .0006, and .002, respectively). In contrast, ADP/ATP ratio as well as TF and MCP-1 expressions on the isolated islets were higher among the ischemic group (P = .005, .16, and .005, respectively). During isolation procedures, the ATP/DNA of the exocrine tissues was extremely lower in the ischemic compared to the control group (P < .0001). Notably, however, both ATP/DNA and ADP/ATP ratio of isolated islets were well preserved even in the ischemic group (P = .45 and .40). DISCUSSION These data suggest that ischemic stress during the preservation period negatively affects the energy status of exocrine tissues. Destruction of the exocrine tissues, in combination with warm ischemic stress during the isolation procedures, subsequently decreases isolated islet activity, inducing the expression of inflammatory mediators.

Influence of a current style of culture on the quality of isolated pancreatic islets.

OBJECTIVE Comparable outcomes of islet transplantation with short periods of culture may be achieved with various culture media. To clarify the influence of a style of culture on isolated pancreatic islets, islet quality of fresh islets was compared with those cultured in several different fashions including not only for viability but also for inflammatory mediators. MATERIALS AND METHODS Wistar rat islets were cultured for 48 hours with CMRL including 10% allogeneic serum; CMRL including 0.5% human serum albumin (HSA); and Miami medium including 0.5% HSA. The influence of culture conditions on islet integrity was evaluated by survival rate of islets during culture and visual scoring. The influence of culture conditions on islet function and viability was examined by ADP/ATP tests, insulin/DNA content, and glucose stimulation tests. RESULTS Although the survival rates were similar for all groups, the visual scoring was lower in Miami medium. The stimulation index in glucose challenge tests was higher for fresh islets than the media (P = .02). Insulin/DNA ratios revealed the same tendency as glucose challenge tests (P = .0005). ADP/ATP ratio was lower in both the fresh and serum groups than in the others (P = .38), suggesting that apoptotic islets are relatively fewer in both fresh and serum groups. Most importantly, the expression of tissue factor (TF) on the islets was considerably lower in the fresh group, suggesting that a current style of culture could enhance TF-dependent instant blood-mediated inflammatory reactions after transplantation. CONCLUSION In conclusion, Isolated islets without prior culture shows characteristics beneficial for transplantation using current modes of culture.

The Influence of Brain Death on Tissue Factor Expression in the Pancreatic Tissues and Isolated Islets in Rats

INTRODUCTION Tissue factor (TF) in islets has been identified as the main trigger of the instant blood-mediated inflammatory reaction. Because the crucial events that directly induce TF remain to be determined, we focused on the influence of brain death (BD) on TF expression in pancreatic tissues and isolated islets. MATERIALS AND METHODS BD was induced in male Lewis rats weighing 250-300 g by inflation of a Fogarty catheter placed intracranially. The rats were mechanically ventilated for 6 hours until removal of the pancreas. The expression of TF protein in pancreatic tissues was examined using Western blotting assay. Messenger RNA (mRNA) expressions of TF in pancreatic tissue and isolated islets were analyzed using real-time polymerase chain reaction (PCR) assay. The influence of BD on the isolation outcome was evaluated by islet yield, purity, viability, and function. RESULTS TF protein and mRNA levels in the pancreatic tissues were similar between the groups. However, TF mRNA in the isolated islets of the BD group was significantly greater than that of the control group (P = .04). Islet yield was considerably lower, and purity significantly lower in the BD than the control group (P = .002). Unexpectedly, ATP/DNA ratio and respiratory activity were comparable between the groups. CONCLUSIONS Although BD per se was not sufficient to induce TF expression in pancreatic tissues, BD combined with subsequent warm ischemic damage during isolation procedures remarkably up-regulated TF expression in isolated islets, suggesting that BD is of great importance as an initiator of TF induction in the islet grafts. The present study demonstrated that the expression of inflammatory mediators rather than islet viability is more susceptible to BD.

C5a Inhibitory Peptide Combined With Gabexate Mesilate Is a Clinically Available Candidate for Preventing the Instant Blood-Mediated Inflammatory Reaction

BACKGROUND The instant blood-mediated inflammatory reaction, characterized by activation of both the coagulation and complement cascades, is a serious obstacle to successful islet engraftment. No attractive protocol is clinically available as yet. The objective of the present study was to examine whether complementary peptide against an active region of C5a in combination with a clinically available anticoagulant could provide an effective protocol for suppression of the instant blood-mediated inflammatory reaction. METHODS Three islet equivalents per gram of syngeneic rat grafts were transplanted intraportally into 6 pairs of rats with streptozotocin-induced diabetes. Islets from the same donor were transplanted into each pair. In each pair, one rat was treated with C5a inhibitory peptide in addition to continuous intravenous infusion of gabexate mesilate and the other rat, injected with equivalent amount of saline solution, served as the control. In addition, 6 rats that received transplants from irrelevant donors were treated with the same dose of gabexate mesilate. We evaluated the cure rate, time to normoglycemia, liver insulin concentration in recipients, and results of in vivo glucose tolerance tests. RESULTS The cure rate was remarkably improved and the time to normoglycemia in cured animals was significantly shortened with C5a inhibitor plus gabexate treatment. In six rats that received only gabexate mesilate, normoglycemia was not restored during the study. CONCLUSIONS These data suggest that C5a inhibitory peptide combined with gabexate mesilate could be an attractive drug candidate without adverse effects to control the detrimental innate immune responses induced in clinical islet transplantation.