Long-Term Administration of Omeprazole-Induced Hypergastrinemia and Changed Glucose Homeostasis and Expression of Metabolism-Related Genes

Introduction

PPIs, or proton pump inhibitors, are the most widely prescribed drugs. There is a debate regarding the relationship between long-term PPI use and the risk of type 2 diabetes mellitus (T2DM). A potential connection between T2DM and PPIs could be an elevated gastrin concentration. This study is aimed at investigating the long-term effects of PPI omeprazole (OZ) on glucose homeostasis and pancreatic gene expression profile in mice.

Methods

Healthy adult male BALB/c mice were randomly divided into three equal groups (n = 10 in each one): (1) experimental mice that received OZ 20 mg/kg; (2) control mice that received 30 μl saline per os; (3) intact mice without any interventions. Mice were treated for 30 weeks. Glucose homeostasis was investigated by fasting blood glucose level, oral glucose tolerance test (GTT), insulin tolerance test (ITT), and basal insulin resistance (HOMA-IR). Serum gastrin and insulin concentration were determined by ELISA. Expressions of Sirt1, Pparg, Nfκb1 (p105), Nfe2l2, Cxcl5, Smad3, H2a.z, and H3f3b were measured by RT-PCR.

Result

The ROC analysis revealed an increase in fasting blood glucose levels in OZ-treated mice in comparison with control and intact groups during the 30-week experiment. A slight but statistically significant increase in glucose tolerance and insulin sensitivity was observed in OZ-treated mice within 30 weeks of the experiment. The mice treated with OZ exhibited significant increases in serum insulin and gastrin levels, accompanied by a rise in the HOMA-IR level. These animals had a statistically significant increase in Sirt1, Pparg, and Cxcl5 mRNA expression. There were no differences in β-cell numbers between groups.

Conclusion

Long-term OZ treatment induced hypergastrin- and hyperinsulinemia and increased expression of Sirt1, Pparg, and Cxcl5 in mouse pancreatic tissues accompanied by specific changes in glucose metabolism. The mechanism of omeprazole-induced Cxcl5 mRNA expression and its association with pancreatic cancer risk should be investigated.

Advancements in innate immune regulation strategies in islet transplantation

As a newly emerging organ transplantation technique, islet transplantation has shown the advantages of minimal trauma and high safety since it was first carried out. The proposal of the Edmonton protocol, which has been widely applied, was a breakthrough in this method. However, direct contact between islets and portal vein blood will cause a robust innate immune response leading to massive apoptosis of the graft, and macrophages play an essential role in the innate immune response. Therefore, therapeutic strategies targeting macrophages in the innate immune response have become a popular research topic in recent years. This paper will summarize and analyze recent research on strategies for regulating innate immunity, primarily focusing on macrophages, in the field of islet transplantation, including drug therapy, optimization of islet preparation process, islet engineering and Mesenchymal stem cells cotransplantation. We also expounded the heterogeneity, plasticity and activation mechanism of macrophages in islet transplantation, providing a theoretical basis for further research.

Construction of engineered 3D islet micro-tissue using porcine decellularized ECM for the treatment of diabetes

Islet transplantation improves diabetes patients' long-term blood glucose control, but its success and utility are limited by cadaver availability, quality, and considerable islet loss after transplantation due to ischemia and inadequate angiogenesis. This study used adipose, pancreatic, and liver tissue decellularized extracellular matrix (dECM) hydrogels in an effort to recapitulate the islet sites inside the pancreas in vitro, and successfully generated viable and functional heterocellular islet micro-tissues using islet cells, human umbilical vein endothelial cells, and adipose-derived mesenchymal stem cells. The three-dimensional (3D) islet micro-tissues maintained prolonged viability and normal secretory function, and showed high drug sensitivity in drug testing. Meanwhile, the 3D islet micro-tissues significantly enhanced survival and graft function in a mouse model of diabetes. These supportive 3D physiomimetic dECM hydrogels can be used not only for islet micro-tissue culture in vitro, but also have great promise for islet transplantation for the treatment of diabetes.

Process parameter development for the scaled generation of stem cell-derived pancreatic endocrine cells

Diabetes is a debilitating disease characterized by high blood glucose levels. The global prevalence of this disease has been projected to reach 700 million adults by the year 2045. Type 1 diabetes represents about 10% of the reported cases of diabetes. Although islet transplantation can be a highly effective method to treat type 1 diabetes, its widespread application is limited by the paucity of cadaveric donor islets. The use of pluripotent stem cells as an unlimited cell source to generate insulin‐producing cells for implant is a promising alternative for treating diabetes. However, to be clinically relevant, it is necessary to manufacture these stem cell‐derived cells at sufficient scales. Significant advances have been made in differentiation protocols used to generate stem cell‐derived cells capable of reversing diabetes in animal models and for testing in clinical trials. We discuss the potential of both stem cell‐derived pancreatic progenitors and more matured insulin‐producing cells to treat diabetes. We discuss the need for rigorous bioprocess parameter optimization and identify some critical process parameters and strategies that may influence the critical quality attributes of the cells with the goal of facilitating scalable manufacturing of human pluripotent stem cell‐derived pancreatic endocrine cells.

The Efficacy of the Hepatocyte Spheroids for Hepatocyte Transplantation

The safety and short-term efficacy of hepatocyte transplantation (HCTx) have been widely proven. However, issues such as reduced viability and/or function of hepatocytes, insufficient engraftment, and lack of a long-term effect have to be overcome for widespread application of HCTx. In this study, we evaluated hepatocyte spheroids (HSs), formed by self-aggregation of hepatocytes, as an alternative to hepatocytes in single-cell suspension. Hepatocytes were isolated from C57BL/6 J mice liver using a three-step collagenase perfusion technique and HSs were formed by the hanging drop method. After the spheroids formation, the HSs showed significantly higher mRNA expression of albumin, ornithine transcarbamylase, glucose-6-phosphate, alpha-1-antitrypsin, low density lipoprotein receptor, coagulation factors, and apolipoprotein E (ApoE) than 2 dimensional (2D)-cultured hepatocytes (p < 0.05). Albumin production by HSs was significantly higher than that by 2D-cultured hepatocytes (9.5 ± 2.5 vs 3.5 ± 1.8 μg/dL, p < 0.05). The HSs, but not single hepatocytes, maintained viability and albumin mRNA expression in suspension (92.0 ± 2.8% and 1.03 ± 0.09 at 6 h). HSs (3.6 × 10⁶ cells) or isolated hepatocytes (fSH, 3.6 × 10⁶ cells) were transplanted into the liver of ApoE knockout (KO-/-) mice via the portal vein. Following transplantation, serum ApoE concentration (ng/mL) of HS-transplanted mice (1w: 63.1 ± 56.7, 4w: 17.0 ± 10.9) was higher than that of fSH-transplanted mice (1 w: 33.4 ± 13.0, 4w: 13.7 ± 9.6). In both groups, the mRNA levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α, MCP-1, and MIP-1β) were upregulated in the liver following transplantation; however, no significant differences were observed. Pathologically, transplanted HSs were observed as flat cell clusters in contact with the portal vein wall on day 7. Additionally, ApoE positive cells were observed in the liver parenchyma distant from the portal vein on day 28. Our results indicate that HS is a promising alternative to single hepatocytes and can be applied for HCTx.

Does Islet Size Really Influence Graft Function After Clinical Islet Transplantation?

Background

It has been proposed that islet transplants comprised primarily of small rather than large islets may provide better graft function, due to their lower susceptibility to hypoxic damage. Our aim was to determine whether islet size correlated with in vivo graft function in islet transplant recipients with C peptide–negative type 1 diabetes when islets have undergone pretransplant islet culture.

Methods

Human pancreatic islets were isolated, cultured for 24 hours and infused by standardized protocols. Ninety-minute stimulated C-peptide concentrations were determined during a standard meal tolerance test 3 months posttransplant. The islet isolation index (IEq/islet number) was determined immediately after isolation and again before transplantation (after tissue culture). This was correlated with patient insulin requirement or stimulated C-peptide.

Results

Changes in insulin requirement did not significantly correlate with islet isolation index. Stimulated C-peptide correlated weakly with IEq at isolation (P = 0.40) and significantly with IEq at transplantation (P = 0.018). Stimulated C-peptide correlated with islet number at isolation (P = 0.013) and more strongly with the islet number at transplantation (P = 0.001). In contrast, the correlation of stimulated C-peptide and islet isolation index was weaker (P = 0.018), and this was poorer at transplantation (P = 0.034). Using linear regression, the strongest association with graft function was islet number (r = 0.722, P = 0.001). Islet size was not related to graft function after adjusting for islet volume or number.

Conclusions

These data show no clear correlation between islet isolation index and graft function; both small and large islets are suitable for transplantation, provided the islets have survived a short culture period postisolation.

By analyzing the insulin requirements from 25 islet transplantation recipients, Hughes et al determined the strongest association with graft function was islet number while islet size was not related to graft function after adjusting for islet volume or number.

The Flaws and Future of Islet Volume Measurements

When working with isolated islet preparations, measuring the volume of tissue is not a trivial matter. Islets come in a large range of sizes and are often contaminated with exocrine tissue. Many factors complicate the procedure, and yet knowledge of the islet volume is essential for predicting the success of an islet transplant or comparing experimental groups in the laboratory. In 1990, Ricordi presented the islet equivalency (IEQ), defined as one IEQ equaling a single spherical islet of 150 μm in diameter. The method for estimating IEQ was developed by visualizing islets in a microscope, estimating their diameter in 50 μm categories and calculating a total volume for the preparation. Shortly after its introduction, the IEQ was adopted as the standard method for islet volume measurements. It has helped to advance research in the field by providing a useful tool improving the reproducibility of islet research and eventually the success of clinical islet transplants. However, the accuracy of the IEQ method has been questioned for years and many alternatives have been proposed, but none have been able to replace the widespread use of the IEQ. This article reviews the history of the IEQ, and discusses the benefits and failings of the measurement. A thorough evaluation of alternatives for estimating islet volume is provided along with the steps needed to uniformly move to an improved method of islet volume estimation. The lessons learned from islet researchers may serve as a guide for other fields of regenerative medicine as cell clusters become a more attractive therapeutic option.

Intraportal Transplantation of Pancreatic Islets in Mouse Model

Pancreatic islet transplantation to reduce hyperglycemia is highly successful in rodents with chemically-induced diabetes. The most common transplantation site in experimental islet transplantation is the kidney capsule. However, as less is known about the interaction of pancreatic islets with blood constituents, it also makes sense to utilize the portal vein approach in experimental islet transplantation. This protocol demonstrates an intraportal islet transplantation technique in NMRI nude mice. Streptozotocin (180 mg/kg) is injected intraperitoneally to induce hyperglycemia in recipient mice. They are considered as diabetic at a non-fasting blood glucose level greater than 20 mmol/L. One day prior to transplantation, mouse pancreatic islets are isolated from the donor pancreas by collagenase digestion; a minimum of 350 islets are utilized per diabetic recipient. Depending upon the islet isolation yield, two or more donor mice are utilized per recipient. After overnight culture at 37 °C, islets are administered into the recipient liver via the portal vein. After surgery, the mice are protected in red Makrolon houses and observed until are awake. This protocol maintains glycemic control for 120 days in syngeneic mice and 15 days in allogeneic mice.

Fully Automated Islet Cell Counter (ICC) for the Assessment of Islet Mass, Purity, and Size Distribution by Digital Image Analysis

For isolated pancreatic islet cell preparations, it is important to be able to reliably assess their mass and quality, and for clinical applications, it is part of the regulatory requirement. Accurate assessment, however, is difficult because islets are spheroid-like cell aggregates of different sizes (<50 to 500 μm) resulting in possible thousandfold differences between the mass contribution of individual particles. The current standard manual counting method that uses size-based group classification is known to be error prone and operator dependent. Digital image analysis (DIA)-based methods can provide less subjective, more reproducible, and better-documented islet cell mass (IEQ) estimates; however, so far, none has become widely accepted or used. Here we present results obtained using a compact, self-contained islet cell counter (ICC3) that includes both the hardware and software needed for automated islet counting and requires minimal operator training and input; hence, it can be easily adapted at any center and could provide a convenient standardized cGMP-compliant IEQ assessment. Using cross-validated sample counting, we found that for most human islet cell preparations, ICC3 provides islet mass (IEQ) estimates that correlate well with those obtained by trained operators using the current manual SOP method ( r² = 0.78, slope = 1.02). Variability and reproducibility are also improved compared to the manual method, and most of the remaining variability (CV = 8.9%) results from the rearrangement of the islet particles due to movement of the sample between counts. Characterization of the size distribution is also important, and the present digitally collected data allow more detailed analysis and coverage of a wider size range. We found again that for human islet cell preparations, a Weibull distribution function provides good description of the particle size.

Engineering islet for improved performance by optimized reaggregation in alginate gel beads

After islet isolation, diffusion has become the main mechanism to transport oxygen and nutrients into the core of islets. However, diffusion has limitations, by which nutrients cannot effectively reach the core of large islets and can eventually cause core cell death and islet loss. This problem can be resolved by dispersing islets into single islet cells, but single islet cells do not exhibit insulin release function in in vitro culture. In this study, we intended to establish a new islet engineering approach by forming islet cell clusters to improve islet survival and function. Therefore, alginate gels were used to encapsulate islet cells to form artificial islets after dispersion of islets into single cells. The shape of the islet cell clusters was similar to native islets, and the size of the islet cell clusters was limited to a maximum diameter of 100 μm. By limiting the diameter of this engineered islet cell cluster, cell viability was nearly 100%, a significant improvement over natural islets. Importantly, islet cell clusters express the genes of islets, including Isl-1, Gcg, and insulin-1, and insulin secretion ability was maintained in vitro.

Differences in insulin biosynthesis pathway between small and large islets do not correspond to insulin secretion

In a variety of mammalian species, small islets secrete more insulin per volume than large islets. This difference may be due to diffusional limitations of large islets, or inherent differences in the insulin production pathways. The purpose of this study was to identify possible differences in the early phase of glucose-stimulated insulin biosynthesis between large and small islets. Isolated small and large rat islets were challenged with 30 minutes of high glucose. The expression of insulin gene transcription factors (MafA, NeuroD/ Beta2, and PDX-1), preproinsulin mRNA, proinsulin and insulin were compared between large and small islets. Under basal (low glucose) conditions, MafA and NeuroD had higher mRNA levels and greater protein amounts in large islets compared to small when normalized to GAPDH levels. 30 minutes of high glucose stimulation failed to alter the mRNA or subsequent protein levels of either gene. However, 30 minutes of high glucose suppressed activated PDX-1 protein levels in both small and large islets. High glucose stimulation did not statistically alter the preproinsulin mRNA (insulin 1 and insulin 2) levels. At the translational level, high glucose increased the proinsulin levels, and large islets showed a higher proinsulin content per cell than small islets. Insulin content per cell was not significantly different between small and large islets under basal or high glucose levels. The results fail to explain the higher level of insulin secretion noted in small versus large islets and may suggest that possible differences lie downstream in the secretory pathway rather than insulin biosynthesis.

Improved physiological properties of gravity-enforced reassembled rat and human pancreatic pseudo-islets

Previously we demonstrated the superiority of small islets vs large islets in terms of function and survival after transplantation, and we generated reaggregated rat islets (pseudo-islets) of standardized small dimensions by the hanging-drop culture method (HDCM). The aim of this study was to generate human pseudo-islets by HDCM and to evaluate and compare the physiological properties of rat and human pseudo-islets. Isolated rat and human islets were dissociated into single cells and incubated for 6-14 days by HDCM. Newly formed pseudo-islets were analysed for dimensions, morphology, glucose-stimulated insulin secretion (GSIS) and total insulin content. The morphology of reaggregated human islets was similar to that of native islets, while rat pseudo-islets had a reduced content of α and δ cells. GSIS of small rat and human pseudo-islets (250 cells) was increased up to 4.0-fold (p < 0.01) and 2.5-fold (p < 0.001), respectively, when compared to their native counterparts. Human pseudo-islets showed a more pronounced first-phase insulin secretion as compared to intact islets. GSIS was inversely correlated to islet size, and small islets (250 cells) contained up to six-fold more insulin/cell than large islets (1500 cells). Tissue loss with this new technology could be reduced to 49.2 ± 1.5% in rat islets, as compared to the starting amount. With HDCM, pseudo-islets of standardized size with similar cellular composition and improved biological function can be generated, which compensates for tissue loss during production. Transplantation of small pseudo-islets may represent an attractive strategy to improve graft survival and function, due to better oxygen and nutrient supply during the phase of revascularization. Copyright © 2014 John Wiley & Sons, Ltd.

Microchip-based engineering of super-pancreatic islets supported by adipose-derived stem cells

Type 1 diabetes mellitus (T1DM) is a chronic disorder characterized by targeted autoimmune-mediated destruction of the β cells of Langerhans within pancreatic islets. Currently, islet transplantation is the only curative therapy; however, donor shortages and cellular damage during the isolation process critically limit the use of this approach. Here, we describe a method for creating viable and functionally potent islets for successful transplantation by co-culturing single primary islet cells with adipose-derived stem cells (ADSCs) in concave microwells. We observed that the ADSCs segregated from the islet cells, eventually yielding purified islet spheroids in the three-dimensional environment. Thereafter, the ADSC-exposed islet spheroids showed significantly different ultrastructural morphologies, higher viability, and enhanced insulin secretion compared to mono-cultured islet spheroids. This suggests that ADSCs may have a significant potential to protect islet cells from damage during culture, and may be employed to improve islet cell survival and function prior to transplantation. In vivo experiments involving xenotransplantation of microfiber-encapsulated spheroids into a mouse model of diabetes revealed that co-culture-transplanted mice maintained their blood glucose levels longer than mono-culture-transplanted mice, and required less islet mass to reverse diabetes. This method for culturing islet spheroids could potentially help overcome the cell shortages that have limited clinical applications and could possibly be developed into a bioartificial pancreas.

Impact of islet size on pancreatic islet transplantation and potential interventions to improve outcome

Better results have been recently reported in clinical pancreatic islet transplantation (ITX) due mostly to improved isolation techniques and immunosuppression; however, some limitations still exist. It is known that following transplantation, 30% to 60% of the islets are lost. In our study, we have investigated 1) the role of size as a factor affecting islet engraftment and 2) potential procedural manipulations to increase the number of smaller functional islets that can be transplanted. C57/BL10 mice were used as donors and recipients in a syngeneic islet transplant model. Isolated islets were divided by size (large, >300 μm; medium 150-300 μm; small, <150 μm). Each size was transplanted in chemically induced diabetic mice as full (600 IEQ), suboptimal (400 IEQ), and marginal mass (200 IEQ). Control animals received all size islets. Engraftment was defined as reversal of diabetes by day 7 posttransplantation. When the superiority of smaller islets was observed, strategies of overdigestion and fragmentation were adopted during islet isolation in the attempt to reduce islet size and improve engraftment. Smaller islets were significantly superior in engraftment compared to medium, large, and control (all sizes) groups. This was more evident when marginal mass data were compared. In all masses, success decreased as islet size increased. Once islets were engrafted, functionality was not affected by size. When larger islets were fragmented, a significant decrease in islet functionality was observed. On the contrary, if pancreata were slightly overdigested, although not as successful as small naive islets, an increase in engraftment was observed when compared to the control group. In conclusion, smaller islets are superior in engraftment following islet transplantation. Fragmentation has a deleterious effect on islet engraftment. Islet isolations can be performed by reducing islet size with slight overdigestion, and it can be safely adopted to improve clinical outcome.

KU-32, a novel drug for diabetic neuropathy, is safe for human islets and improves in vitro insulin secretion and viability

KU-32 is a novel, novobiocin-based Hsp90 inhibitor that protects against neuronal glucotoxicity and reverses multiple clinical indices of diabetic peripheral neuropathy in a rodent model. However, any drug with potential for treating diabetic complications must also have no adverse effects on the function of pancreatic islets. Thus, the goal of the current study was to assess the effect of KU-32 on the in vitro viability and function of human islets. Treating human islets with KU-32 for 24 hours showed no toxicity as assessed using the alamarBlue assay. Confocal microscopy confirmed that with a minimum of 2-day exposure, KU-32 improved cellular viability by blocking apoptosis. Functionally, isolated human islets released more glucose-stimulated insulin when preincubated in KU-32. However, diabetic BKS-db/db mice, a model for type 2 diabetes, administered KU-32 for 10 weeks did not show any significant changes in blood glucose and insulin levels, despite having greater insulin staining/beta cell in the pancreas compared to untreated BKS db/db mice. In summary, KU-32 did not harm isolated human islets and may even be protective. However, the effect does not appear significant enough to alter the in vivo metabolic parameters of diabetic mice.

Functional assessment of automatically sorted pancreatic islets using large particle flow cytometry

The size composition of human islet preparations has been attributed to functional potency, islet survival and transplantation outcomes. In the early post-transplantation phase islets are supplied with oxygen by diffusion only and are at risk of critical hypoxia. The high rate of early islet graft dysfunction is in part attributed to this condition. It has been presumed that islets with smaller diameter, and therefore smaller diffusion distance, are superior to large islets regarding early survival rate and graft function. In this study we aimed to evaluate Complex Object Parametric Analysis and Sorting (COPAS) as a device for automated sorting of human islets. The use of COPAS was validated for accuracy and sensitivity using polystyrene beads of known diameters. Based on time of flight relative to particle isolated islets were then automatically sorted and analyzed for viability and function using handpicked islets as control. Our results suggest that COPAS enables the automated and accurate sorting of islets with no negative impact on their integrity and viability. Thus, COPAS is an adequate tool for size-specific analysis of pancreatic islets and may be considered as part of a platform for automated high-throughput screening of pancreatic islets.

Low insulin content of large islet population is present in situ and in isolated islets

The existence of morphologically distinct populations of islets in the pancreas was described over 60 years ago. Unfortunately, little attention has been paid to possible functional differences between islet subpopulations until recently. We demonstrated that one population, the small islets, were superior to large islets in a number of functional aspects. However, that work did not determine whether these differences were inherent, or whether they arose because of the challenge of isolation procedures. Nor, were there data to explain the differences in insulin secretion. We utilized immunohistochemistry, immunofluorescence, ELISA, and transmission electron microscopy to compare the unique characteristics found in isolated rat islet populations in situ and after isolation. Insulin secretion of small isolated islets was significantly higher compared to large islets, which correlated with higher insulin content/area in small islets (in situ), a higher density of insulin secretory granules, and greater insulin content/volume in isolated islets. Specifically, the core b-cells of the large islets contained less insulin/cell with a lower insulin granule density than peripheral b-cells. When insulin secretion was normalized for total insulin content, large and small islets released the same percentage of total insulin. Small islets had a higher density of cells/area than large islets in vitro and in situ. The data provide a possible explanation for the inferior insulin secretion from large islets, as they have a lower total cell density and the b-cells of the core contain less insulin/cell.