The NERP-4-SNAT2 axis regulates pancreatic β-cell maintenance and function

Insulin secretion from pancreatic β cells is regulated by multiple stimuli, including nutrients, hormones, neuronal inputs, and local signalling. Amino acids modulate insulin secretion via amino acid transporters expressed on β cells. The granin protein VGF has dual roles in β cells: regulating secretory granule formation and functioning as a multiple peptide precursor. A VGF-derived peptide, neuroendocrine regulatory peptide-4 (NERP-4), increases Ca2+ influx in the pancreata of transgenic mice expressing apoaequorin, a Ca2+-induced bioluminescent protein complex. NERP-4 enhances glucose-stimulated insulin secretion from isolated human and mouse islets and β-cell-derived MIN6-K8 cells. NERP-4 administration reverses the impairment of β-cell maintenance and function in db/db mice by enhancing mitochondrial function and reducing metabolic stress. NERP-4 acts on sodium-coupled neutral amino acid transporter 2 (SNAT2), thereby increasing glutamine, alanine, and proline uptake into β cells and stimulating insulin secretion. SNAT2 deletion and inhibition abolish the protective effects of NERP-4 on β-cell maintenance. These findings demonstrate a novel autocrine mechanism of β-cell maintenance and function that is mediated by the peptide-amino acid transporter axis.

Innovative transdermal delivery of insulin using gelatin methacrylate-based microneedle patches in mice and mini-pigs

Painless and controlled on-demand drug delivery is the ultimate goal for the management of various chronic diseases, including diabetes. To achieve this purpose, microneedle patches are gaining increased attention. While degradable microneedle (MN) arrays are widely employed, the use of non-dissolving MN patches remains a challenge to overcome. In this study, we demonstrate that crosslinking gelatin methacrylate with polyethylene glycol diacrylate (PEGDA) is potent for engineering non-dissolving MN arrays. Incorporation of MoS₂ nanosheets as a photothermal component into MN hydrogels results in MNs featuring on-demand release properties. An optimized MoS₂-MN array patch formed using a hydrogel solution containing 500 μg mL^-1 of MoS₂ and photochemically crosslinked for 5 min shows required mechanical behavior under a normal compressive load to penetrate the stratum corneum of mice or pig skin and allows the delivery of macromolecular therapeutics such as insulin upon swelling. Using ex vivo and in vivo models, we show that the MoS₂-MN patches can be used for loading and releasing insulin for therapeutic purposes. Indeed, transdermal administration of insulin loaded into MoS₂-MN patches reduces blood glucose levels in C57BL/6 mice and mini-pigs comparably to subcutaneously injected insulin. We believe that this on-demand delivery system might alter the current insulin therapies and might be a potential approach for delivery of other proteins.

Effects of proprotein convertase subtilisin kexin type 9 modulation in human pancreatic beta cells function

BACKGROUND AND AIMS

Proprotein Convertase Subtilisin Kexin Type 9 (PCSK9) is an endogenous inhibitor of the LDL receptor (LDLR). Mendelian randomization studies suggest that PCSK9 deficiency increases diabetes risk, but the underlying mechanisms remain unknown. The aim of our study was to investigate whether PCSK9 or its inhibition may modulate beta cell function.

METHODS

We assessed PCSK9 and insulin colocalization in human pancreatic sections by epifluorescent and confocal microscopy. We also investigated the expression and the function of PCSK9 in the human EndoC-βH1 beta cell line, by ELISA and flow cytometry, respectively. PCSK9 was inhibited with Alirocumab or siRNA. LDLR expression and LDL uptake were assessed by flow cytometry.

RESULTS

PCSK9 was expressed and secreted from beta cells isolated from human pancreas as well as from EndoC-βH1 cells. PCSK9 secretion was enhanced by statin treatment. Recombinant PCSK9 decreased LDLR abundance at the surface of these cells, an effect abrogated by Alirocumab. Alirocumab as well as PCSK9 silencing increased LDLR expression at the surface of EndoC-βH1 cells. Neither exogenous PCSK9, nor Alirocumab, nor PCSK9 silencing significantly altered glucose-stimulated insulin secretion (GSIS) from these cells. High-low density lipoproteins (LDL) concentrations decreased GSIS, but the addition of PCSK9 or its inhibition did not modulate this phenomenon.

CONCLUSIONS

While PCSK9 regulates LDLR abundance in beta cells, inhibition of exogenous or endogenous PCSK9 does not appear to significantly impact insulin secretion. This is reassuring for the safety of PCSK9 inhibitors in terms of beta cell function.

Pancreatic islet transplantation under the kidney capsule of mice: model of refinement for molecular and ex-vivo graft analysis

Diabetes cell therapy by human islet transplantation can restore an endogenous insulin secretion and normal glycaemic control in type 1 diabetic patients for as long as 10 years post transplantation. Before transplantation, each clinical islet preparation undergoes extensive in-vitro and in-vivo quality controls. The in-vivo quality control assay consists of transplanting human islets under the kidney capsule of immunocompromised mice. Currently, it is considered the best predictive factor to qualify clinical transplant efficiency. This chimeric model offers a wide area of study since it combines the possibility of producing not only quantitative but also a maximum of qualitative data. Today's technological advances allow us to obtain more accurate and stronger data from the animals used in research while ensuring their comfort and well-being throughout the protocol, including cage enrichment and pain treatment during and after surgery. As demonstrated in this valuable model, we are able to generate more usable results (Refine), while reducing the number of animals used (Reduce), by focusing on the development of ex-vivo analysis techniques (Replace), which clearly highlights the Burch and Russell 3Rs concept.

P1672IMPACT OF ISLET TRANSPLANTATION VERSUS INSULIN ALONE AFTER KIDNEY TRANSPLANTATION IN TYPE 1 DIABETES PATIENTS

Background and Aims

In patients with type 1 diabetes and end-stage renal disease, kidney transplantation improves both quality of life and survival. When simultaneous kidney-pancreas transplantation appears too invasive, or after failure of the pancreatic graft, an islet after kidney transplantation (IAK) may be considered to restore a stable endocrine function. The aim of our work was to assess the impact of islet transplantation on kidney transplantation outcomes versus insulin alone.

Method

In this retrospective parallel-arm cohort study in Lille, we included all type 1 diabetes patients who received a kidney graft from 2000 to 2017, followed by an islet transplantation after kidney (IAK) or not (kidney alone, KA). The primary study endpoint was the change of renal function (estimated glomerular filtration rate, eGFR). Secondary endpoints were glycemic control-related markers, such as HBA1c.

Results

During the period of study, 14 patients were included in the KA group versus 15 in the IAK group (including 5 after failure of a simultaneous pancreatic graft) were enrolled. At baseline, kidney donor sex, BMI, cause of death, cold ischemia time and recipient sex, waiting time on dialysis, type of dialysis, and number of previous kidney transplantation, were similar between the two groups. Yet, there were significant differences between KA and IAK, considering donor age (resp. 56.0±15.0 vs 35.2±13.7 years, p<0.001), use of perfusion machine (resp. 7 vs 0, p= 0.002), recipient age (resp. 55.7±5.7 vs 42.1±6.1, p<0.001), and recipient BMI (24.7± 1.8 vs 21.9±2.5 k/m? p=0.004). In IAK, the median (IQR) time between islet and kidney transplantation was 21.8 months (19.0 – 29.4). eGFR was not significantly different at baseline (IAK: 57.8±17.7 vs KA: 48.9±21.4 ml/min, p=0.22) but the decrease was significantly lower up to 5 years in the IAK group (IAK: 0.05±1.99 ml/min/year vs KA: -2.42±3.43 ml/min/year, p=0.03). HBA1c was similar at baseline in both groups (IAK: 7.8±1.6% versus KA: 7.9±1.1%, p=0.31), but significantly lower in the IAK group up to 5 years (IAK: 6.6±0.97% versus KA: 7.8±1.12%, p<0.001).

Conclusion

In patients with type 1 diabetes and a functioning kidney graft, IAK was associated with a better glucose control and a slower decrease of eGFR than standard insulin therapy. Our results suggest that IAK should be proposed to type 1 diabetes patients with a functional kidney graft.

Interindividual Heterogeneity of SGLT2 Expression and Function in Human Pancreatic Islets

Studies implicating sodium-glucose cotransporter 2 (SGLT2) inhibitors in glucagon secretion by pancreatic α-cells reported controversial results. We hypothesized that interindividual heterogeneity in SGLT2 expression and regulation may affect glucagon secretion by human α-cells in response to SGLT2 inhibitors. An unbiased RNA-sequencing analysis of 207 donors revealed an unprecedented level of heterogeneity of SLC5A2 expression. To determine heterogeneity of SGLT2 expression at the protein level, the anti-SGLT2 antibody was first rigorously evaluated for specificity, followed by Western blot and immunofluorescence analysis on islets from 10 and 12 donors, respectively. The results revealed a high interdonor variability of SGLT2 protein expression. Quantitative analysis of 665 human islets showed a significant SGLT2 protein colocalization with glucagon but not with insulin or somatostatin. Moreover, glucagon secretion by islets from 31 donors at low glucose (1 mmol/L) was also heterogeneous and correlated with dapagliflozin-induced glucagon secretion at 6 mmol/L glucose. Intriguingly, islets from three donors did not secrete glucagon in response to either 1 mmol/L glucose or dapagliflozin, indicating a functional impairment of the islets of these donors to glucose sensing and SGLT2 inhibition. Collectively, these data suggest that heterogeneous expression of SGLT2 protein and variability in glucagon secretory responses contribute to interindividual differences in response to SGLT2 inhibitors.

The Map3k12 (Dlk)/JNK3 signaling pathway is required for pancreatic beta-cell proliferation during postnatal development

Unveiling the key pathways underlying postnatal beta-cell proliferation can be instrumental to decipher the mechanisms of beta-cell mass plasticity to increased physiological demand of insulin during weight gain and pregnancy. Using transcriptome and global Serine Threonine Kinase activity (STK) analyses of islets from newborn (10 days old) and adult rats, we found that highly proliferative neonatal rat islet cells display a substantially elevated activity of the mitogen activated protein 3 kinase 12, also called dual leucine zipper-bearing kinase (Dlk). As a key upstream component of the c-Jun amino terminal kinase (Jnk) pathway, Dlk overexpression was associated with increased Jnk3 activity and was mainly localized in the beta-cell cytoplasm. We provide the evidence that Dlk associates with and activates Jnk3, and that this cascade stimulates the expression of Ccnd1 and Ccnd2, two essential cyclins controlling postnatal beta-cell replication. Silencing of Dlk or of Jnk3 in neonatal islet cells dramatically hampered primary beta-cell replication and the expression of the two cyclins. Moreover, the expression of Dlk, Jnk3, Ccnd1 and Ccnd2 was induced in high replicative islet beta cells from ob/ob mice during weight gain, and from pregnant female rats. In human islets from non-diabetic obese individuals, DLK expression was also cytoplasmic and the rise of the mRNA level was associated with an increase of JNK3, CCND1 and CCND2 mRNA levels, when compared to islets from lean and obese patients with diabetes. In conclusion, we find that activation of Jnk3 signalling by Dlk could be a key mechanism for adapting islet beta-cell mass during postnatal development and weight gain.

Single Low Dose of Human Recombinant Antithrombin (ATryn) has no Impact on Endotoxin-Induced Disseminated Intravascular Coagulation: An Experimental Randomized Open Label Controlled Study

BACKGROUND

Antithrombin (AT) III physiological levels are decreased during septic shock and supplementation therapy could therefore be beneficial.

OBJECTIVE

We hypothesized that the use of recombinant human AT could reduce disseminated intravascular coagulation (DIC) occurrence.

METHODS

We conducted a randomized open label controlled experimental study. Ten female "Large White" pigs were challenged with i.v. infusion of Escherichia coli endotoxin. Two groups of 5 pigs were randomly assigned to receive either recombinant human AT 100 U/kg over 30 min (ATryn group) or 0.9% saline (control group). AT III levels, coagulation, hemostasis, inflammation parameters, hemodynamics, and microcirculatory parameters were measured over a 5-h period. Immediately after euthanasia, kidneys were withdrawn for histology evaluation. Statistical analysis was performed with nonparametric tests and Dunn's test for multiple comparisons.

RESULTS

AT III activity was significantly higher in the ATryn group than in the control group from 60% (213% [203-223] vs. 104% [98-115], P = 0.008, respectively) to 300 min (115% [95-124] vs. 79% [67-93], P = 0.03). Recombinant human AT supplementation had no impact on hemodynamics, microcirculatory parameters, and sequential changes of coagulation parameters (platelet count, fibrinogen level, thrombin-AT complexes, and von Willebrand factor). Interleukin 6 and tumor necrosis factor α values were statistically the same for both groups throughout the study. Percentage of thrombosed glomeruli and percentage of thrombosed capillary in glomerulus were not significantly different between both groups.

CONCLUSIONS

In our model of endotoxic shock, a single low dose of recombinant human AT did not prevent DIC occurrence, severity, inflammatory profile, or hemodynamic alterations.

Islets for Research: Nothing Is Perfect, but We Can Do Better

In December 2018, Diabetes and Diabetologia began requiring authors of papers reporting data obtained from studies on human islets to report critical characteristics of the human islets used for research. The islet community was asked to provide feedback on it. Here is the contribution by the European Consortium for Islet Transplantation.

Purity of islet preparations and 5-year metabolic outcome of allogenic islet transplantation

In allogenic islet transplantation (IT), high purity of islet preparations and low contamination by nonislet cells are generally favored. The aim of the present study was to analyze the relation between the purity of transplanted preparations and graft function during 5 years post-IT. Twenty-four patients with type 1 diabetes, followed for 5 years after IT, were enrolled. Metabolic parameters and daily insulin requirements were compared between patients who received islet preparations with a mean purity <50% (LOW purity) or ≥50% (HIGH purity). We also analyzed blood levels of carbohydrate antigen 19-9 (CA 19-9)-a biomarker of pancreatic ductal cells-and glucagon, before and after IT. At 5 years, mean hemoglobin A1c (HbA1c levels) (P = .01) and daily insulin requirements (P = .03) were lower in the LOW purity group. Insulin independence was more frequent in the LOW purity group (P < .05). CA19-9 and glucagon levels increased post-IT (P < .0001) and were inversely correlated with the degree of purity. Overall, our results suggest that nonislet cells have a beneficial effect on long-term islet graft function, possibly through ductal-to-endocrine cell differentiation. ClinicalTrial.gov NCT00446264 and NCT01123187.

Sodium lactate improves renal microvascular thrombosis compared to sodium bicarbonate and 0.9% NaCl in a porcine model of endotoxic shock: an experimental randomized open label controlled study

Background

Sodium lactate seemed to improve fluid balance and avoid fluid overload. The objective of this study was to determine if these beneficial effects can be at least partly explained by an improvement in disseminated intravascular coagulation (DIC)-associated renal microvascular thrombosis.

Methods

Ancillary work of an interventional randomized open label controlled experimental study. Fifteen female “Large White” pigs (2 months old) were challenged with intravenous infusion of E. coli endotoxin. Three groups of five animals were randomly assigned to receive different fluids: a treatment group received sodium lactate 11.2% (SL group); an isotonic control group received 0.9% NaCl (NC group); a hypertonic control group, with the same amount of osmoles and sodium than SL group, received sodium bicarbonate 8.4% (SB group). Glomerular filtration rate (GFR) markers, coagulation and inflammation parameters were measured over a 5-h period. Immediately after euthanasia, kidneys were withdrawn for histological study. Statistical analysis was performed with nonparametric tests and the Dunn correction for multiple comparisons. A p < 0.05 was considered significant.

Results

The direct immunofluorescence study revealed that the percentage of capillary sections thrombosed in glomerulus were significantly lesser in SL group [5 (0–28) %] compared to NC [64 (43–79) %, p = 0.01] and SB [64 (43–79), p = 0.03] groups. Alterations in platelet count and fibrinogen level occurred earlier and were significantly more pronounced in both control groups compared to SL group (p < 0.05 at 210 and 300 min). The increase in thrombin–antithrombin complexes was significantly higher in NC [754 (367–945) μg/mL; p = 0.03] and SB [463 (249–592) μg/mL; p = 0.03] groups than in SL group [176 (37–265) μg/mL]. At the end of the experiment, creatinine clearance was significantly higher in SL group [55.46 (30.07–67.85) mL/min] compared to NC group [1.52 (0.17–27.67) mL/min, p = 0.03].

Conclusions

In this study, we report that sodium lactate improves DIC-associated renal microvascular thrombosis and preserves GFR. These findings could at least partly explain the better fluid balance observed with sodium lactate infusion.

Pharmacological approach to understanding the control of insulin secretion in human islets

AIMS

To understand better the control of insulin secretion by human β cells and to identify similarities to and differences from rodent models.

METHODS

Dynamic insulin secretion was measured in perifused human islets treated with pharmacological agents of known modes of action.

RESULTS

Glucokinase activation (Ro28-1675) lowered the glucose threshold for stimulation of insulin secretion to 1 mmol/L (G1), augmented the response to G3-G5 but not to G8-G15, whereas tolbutamide remained active in G20, which indicates that not all K_ATP channels were closed by high glucose concentrations. An almost 2-fold greater response to G15 than to supramaximal tolbutamide in G3 or to KCl+diazoxide in G15 vs G3 quantified the contribution of metabolic amplification to insulin secretion. Both disruption (latrunculin-B) and stabilization (jasplakinolide) of microfilaments augmented insulin secretion without affecting metabolic amplification. Tolbutamide-induced insulin secretion was consistently greater in G10 than G3, with a threshold at 1 and maximum at 10 µmol/L tolbutamide in G10, vs 10 and 25 µmol/L in G3. Sulphonylurea effects were thus clearly glucose-dependent. Insulin secretion was also increased by inhibiting K channels other than K_ATP channels: Kv or BK channels (tetraethylammonium), TASK-1 channels (ML-365) and SK4 channels (TRAM-34). Opening K_ATP channels with diazoxide inhibited glucose-induced insulin secretion with half maximum inhibitory concentrations of 9.6 and 24 µmol/L at G7 and G15. Blockade of L-type Ca channels (nimodipine) abolished insulin secretion, whereas a blocker of T-type Ca channels (NNC-55-0396) was ineffective at specific concentrations. Blockade of Na channels (tetrodotoxin) did not affect glucose-induced insulin secretion.

CONCLUSIONS

In addition to sharing a K_ATP channel-dependent triggering pathway and a metabolic amplifying pathway, human and rodent β cells were found to display more similarities than differences in the control of insulin secretion.

Human Recombinant Antithrombin (ATryn®) Administration Improves Survival and Prevents Intravascular Coagulation After Intraportal Islet Transplantation in a Piglet Model

Human islet transplantation is a viable treatment option for type 1 diabetes mellitus (T1DM). However, pancreatic islet inflammation after transplantation induced by innate immune responses is likely to hinder graft function. This is mediated by incompatibility between islets and the blood interface, known as instant blood-mediated inflammatory reaction (IBMIR). Herein we hypothesized that portal venous administration of islet cells with human recombinant antithrombin (ATryn®), a serine protease inhibitor (serpin), which plays a central role in the physiological regulation of coagulation and exerts indirect anti-inflammatory activities, may offset coagulation abnormalities such as disseminated intravascular coagulation (DIC) and IBMIR. The current prospective, randomized experiment was conducted using an established preclinical pig model. Three groups were constituted for digested pancreatic tissue transplantation (0.15 ml/kg): control, NaCl 0.9% (n = 7); gold standard, heparin (25 UI/kg) (n = 7); and human recombinant ATryn® (500 UI/kg) (n = 7). Blood samples were collected over time (T0 to 24 h), and biochemical, coagulation, and inflammatory parameters were evaluated. In both the control and heparin groups, one animal died after a portal thrombosis, while no deaths occurred in the ATryn®-treated group. As expected, islet transplantation was associated with an increase in plasma IL-6 or TNF-α levels in all three groups. However, DIC was only observed in the control group, an effect that was suppressed after ATryn® administration. ATryn® administration increased antithrombin activity by 800%, which remained at 200% for the remaining period of the study, without any hemorrhagic complications. These studies suggest that coadministration of ATryn® and pancreatic islets via intraportal transplantation may be a valuable therapeutic approach for DIC without risk for islets and subjects.

Bile Diversion in Roux-en-Y Gastric Bypass Modulates Sodium-Dependent Glucose Intestinal Uptake

Gastro-intestinal exclusion by Roux-en-Y gastric bypass (RYGB) improves glucose metabolism, independent of weight loss. Although changes in intestinal bile trafficking have been shown to play a role, the underlying mechanisms are unclear. We performed RYGB in minipigs and showed that the intestinal uptake of ingested glucose is blunted in the bile-deprived alimentary limb (AL). Glucose uptake in the AL was restored by the addition of bile, and this effect was abolished when active glucose intestinal transport was blocked with phlorizin. Sodium-glucose cotransporter 1 remained expressed in the AL, while intraluminal sodium content was markedly decreased. Adding sodium to the AL had the same effect as bile on glucose uptake. It also increased postprandial blood glucose response in conscious minipigs following RYGB. The decrease in intestinal uptake of glucose after RYGB was confirmed in humans. Our results demonstrate that bile diversion affects postprandial glucose metabolism by modulating sodium-glucose intestinal cotransport.

Hypertonic sodium lactate improves fluid balance and hemodynamics in porcine endotoxic shock

Introduction

Based on the potential interest in sodium lactate as an energy substrate and resuscitative fluid, we investigated the effects of hypertonic sodium lactate in a porcine endotoxic shock.

Methods

Fifteen anesthetized, mechanically ventilated pigs were challenged with intravenous infusion of E. coli endotoxin. Three groups of five animals were randomly assigned to receive 5 mL/kg/h of different fluids: a treatment group received hypertonic sodium lactate 11.2% (HSL group); an isotonic control group receiving 0.9% NaCl (NC group); a hypertonic control group with the same amount of osmoles and sodium than HSL group receiving hypertonic sodium bicarbonate 8.4% (HSB group). Hemodynamic and oxygenation variables, urine output and fluid balance were measured at baseline and at 30, 60, 120, 210 and 300 min. Skin microvascular blood flow at rest and during reactive hyperemia was obtained using a laser Doppler flowmetry technique. Results were given as median with interquartile ranges.

Results

Endotoxin infusion resulted in hypodynamic shock. At 300 min, hemodynamics and oxygenation were significantly enhanced in HSL group: mean arterial pressure (103 [81–120] mmHg vs. 49 [41–62] in NC group vs. 71 [60–78] in HSB group), cardiac index (1.6 [1.2–1.8] L/min/m² vs. 0.9 [0.5–1.1] in NC group vs. 1.3 [0.9–1.6] in HSB group) and partial pressure of oxygen (366 [308–392] mmHg vs. 166 [130–206] in NC group vs. 277 [189–303] in HSB group). At the same time, microvascular reactivity was significantly better in HSL group with a lower venoarterial CO₂ tension difference (5.5 [4–10] mmHg vs. 17 [14–25] in NC group vs. 14 [12–15] in HSB group). The cumulative fluid balance was lower in HSL group (-325 [-655; -150] mL) compared to NC (+560 [+230; +900] mL, p = 0.008) and HSB (+185 [-110; +645] mL, p = 0.03) groups.

Conclusions

In our hypodynamic model of endotoxic shock, infusion of hypertonic sodium lactate improves hemodynamic and microvascular reactivity with a negative fluid balance and a better oxygenation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0467-3) contains supplementary material, which is available to authorized users.

JNK3 is required for the cytoprotective effect of exendin 4

Preservation of beta cell against apoptosis is one of the therapeutic benefits of the glucagon-like peptide-1 (GLP1) antidiabetic mimetics for preserving the functional beta cell mass exposed to diabetogenic condition including proinflammatory cytokines. The mitogen activated protein kinase 10 also called c-jun amino-terminal kinase 3 (JNK3) plays a protective role in insulin-secreting cells against death caused by cytokines. In this study, we investigated whether the JNK3 expression is associated with the protective effect elicited by the GLP1 mimetic exendin 4. We found an increase in the abundance of JNK3 in isolated human islets and INS-1E cells cultured with exendin 4. Induction of JNK3 by exendin 4 was associated with an increased survival of INS-1E cells. Silencing of JNK3 prevented the cytoprotective effect of exendin 4 against apoptosis elicited by culture condition and cytokines. These results emphasize the requirement of JNK3 in the antiapoptotic effects of exendin 4.

Automated digital image analysis of islet cell mass using Nikon's inverted eclipse Ti microscope and software to improve engraftment may help to advance the therapeutic efficacy and accessibility of islet transplantation across centers

Reliable assessment of islet viability, mass, and purity must be met prior to transplanting an islet preparation into patients with type 1 diabetes. The standard method for quantifying human islet preparations is by direct microscopic analysis of dithizone-stained islet samples, but this technique may be susceptible to inter-/intraobserver variability, which may induce false positive/negative islet counts. Here we describe a simple, reliable, automated digital image analysis (ADIA) technique for accurately quantifying islets into total islet number, islet equivalent number (IEQ), and islet purity before islet transplantation. Islets were isolated and purified from n = 42 human pancreata according to the automated method of Ricordi et al. For each preparation, three islet samples were stained with dithizone and expressed as IEQ number. Islets were analyzed manually by microscopy or automatically quantified using Nikon's inverted Eclipse Ti microscope with built-in NIS-Elements Advanced Research (AR) software. The AIDA method significantly enhanced the number of islet preparations eligible for engraftment compared to the standard manual method (p < 0.001). Comparisons of individual methods showed good correlations between mean values of IEQ number (r(2) = 0.91) and total islet number (r(2) = 0.88) and thus increased to r(2) = 0.93 when islet surface area was estimated comparatively with IEQ number. The ADIA method showed very high intraobserver reproducibility compared to the standard manual method (p < 0.001). However, islet purity was routinely estimated as significantly higher with the manual method versus the ADIA method (p < 0.001). The ADIA method also detected small islets between 10 and 50 µm in size. Automated digital image analysis utilizing the Nikon Instruments software is an unbiased, simple, and reliable teaching tool to comprehensively assess the individual size of each islet cell preparation prior to transplantation. Implementation of this technology to improve engraftment may help to advance the therapeutic efficacy and accessibility of islet transplantation across centers.

Islet survival and function following intramuscular autotransplantation in the minipig

The liver may not be an optimal site for islet transplantation due to obstacles by an instant blood-mediated inflammatory response (IBMIR), and low revascularization of transplanted islets. Therefore, intramuscular islet transplantation (IMIT) offers an attractive alternative, based on its simplicity, enabling easier access for noninvasive graft imaging and cell explantation. In this study, we explored the outcome of autologous IMIT in the minipig (n = 30). Using the intramuscular injection technique, we demonstrated by direct histological evidence the rapid revascularization of islets autotransplanted into the gracilius muscle. Islet survival assessment was performed using immunohistochemistry staining for insulin and glucagon up to a period of 6 months. Furthermore, we showed the crucial role of minimizing mechanical trauma to the myofibers and limiting exocrine contamination. Intramuscular islet graft function after transplantation was confirmed by documenting the acute insulin response to intravenous glucose in 5/11 pancreatectomized animals. Graft function after IMIT remained however significantly lower than the function measured in 12 out of 18 minipigs who received a similar islet volume in the liver through intraportal infusion. Collectively, these results demonstrated in a clinically relevant preclinical model, suggest IMIT as a promising alternative to intraportal infusion for the transplantation of β cells in certain medical situations.

Adaptive changes of human islets to an obesogenic environment in the mouse

AIMS/HYPOTHESIS

In this study, we used an immunodeficient mouse model to explore, in vivo, the longitudinal adaptation of human islets to an obesogenic environment.

METHODS

Non-diabetic Rag2 (-/-) mice (n = 61) were transplanted with human islets (400 islet equivalents [IEQ]) from six pancreases: four non-diabetic and two with overt metabolic dysfunction (older, high HbA(lc) or history of diabetes). Animals were fed for 12 weeks with a control or high-fat diet (HFD), and followed for weight, serum triacylglycerol, fasting blood glucose and human C-peptide. After the mice were killed, human grafts and the endogenous pancreas were analysed for endocrine volume, distribution of beta and alpha cells, and proliferation.

RESULTS

Transplanted mice on an HFD gained significantly more weight (p < 0.001) and had higher fasting glycaemia (2-12 weeks; p = 0.0002) and consistently higher fasting human C-peptide levels (2-12 weeks; p = 0.04) compared with those on the control diet. Histology demonstrated doubling of human islet graft volume at 12 weeks in animals on the HFD and increased beta cell volume (p < 0.001), but no change in alpha cell volume. Human islet function (hyperbolic product HOMA2%BS) at 12 weeks was four times lower in HFD animals (p < 0.001 vs controls) because of insufficient beta cell adaptation to decreased (70%) sensitivity (HOMA%S). Human islets obtained from donors with metabolic dysfunction failed to adapt to the HFD.

CONCLUSIONS/INTERPRETATION

This longitudinal study provides direct evidence that human islets adapt both endocrine and beta cell mass, function and gene expression to obesity in vivo. The present model will facilitate the identification of mechanisms by which human islets adapt to obesity in vivo and the cell type(s) responsible, and factors predisposing human beta cells to decompensation.

mTORC1 and mTORC2 regulate insulin secretion through Akt in INS-1 cells

Regulated associated protein of mTOR (Raptor) and rapamycin-insensitive companion of mTOR (rictor) are two proteins that delineate two different mTOR complexes, mTORC1 and mTORC2 respectively. Recent studies demonstrated the role of rictor in the development and function of β-cells. mTORC1 has long been known to impact β-cell function and development. However, most of the studies evaluating its role used either drug treatment (i.e. rapamycin) or modification of expression of proteins known to modulate its activity, and the direct role of raptor in insulin secretion is unclear. In this study, using siRNA, we investigated the role of raptor and rictor in insulin secretion and production in INS-1 cells and the possible cross talk between their respective complexes, mTORC1 and mTORC2. Reduced expression of raptor is associated with increased glucose-stimulated insulin secretion and intracellular insulin content. Downregulation of rictor expression leads to impaired insulin secretion without affecting insulin content and is able to correct the increased insulin secretion mediated by raptor siRNA. Using dominant-negative or constitutively active forms of Akt, we demonstrate that the effect of both raptor and rictor is mediated through alteration of Akt signaling. Our finding shed new light on the mechanism of control of insulin secretion and production by the mTOR, and they provide evidence for antagonistic effect of raptor and rictor on insulin secretion in response to glucose by modulating the activity of Akt, whereas only raptor is able to control insulin biosynthesis.

Human β cell transcriptome analysis uncovers lncRNAs that are tissue-specific, dynamically regulated, and abnormally expressed in type 2 diabetes

A significant portion of the genome is transcribed as long noncoding RNAs (lncRNAs), several of which are known to control gene expression. The repertoire and regulation of lncRNAs in disease-relevant tissues, however, has not been systematically explored. We report a comprehensive strand-specific transcriptome map of human pancreatic islets and β cells, and uncover >1100 intergenic and antisense islet-cell lncRNA genes. We find islet lncRNAs that are dynamically regulated and show that they are an integral component of the β cell differentiation and maturation program. We sequenced the mouse islet transcriptome and identify lncRNA orthologs that are regulated like their human counterparts. Depletion of HI-LNC25, a β cell-specific lncRNA, downregulated GLIS3 mRNA, thus exemplifying a gene regulatory function of islet lncRNAs. Finally, selected islet lncRNAs were dysregulated in type 2 diabetes or mapped to genetic loci underlying diabetes susceptibility. These findings reveal a new class of islet-cell genes relevant to β cell programming and diabetes pathophysiology.

TCF7L2 rs7903146 impairs islet function and morphology in non-diabetic individuals

AIMS/HYPOTHESIS

Transcription factor 7-like 2 (TCF7L2) is a Wnt-signalling-associated transcription factor. Genetic studies have clearly demonstrated that DNA polymorphisms within TCF7L2 confer the strongest known association with increased risk of type 2 diabetes. However, the impact of the TCF7L2 type-2-diabetes-associated rs7903146 T allele on biological function and morphology of human pancreatic islets is unknown.

METHODS

Paraffin sections of pancreases from 187 brain-deceased donors (HbA(1c) <6.5% [48 mmol/mol]) were used to genotype the TCF7L2 variant rs7903146 and evaluate its impact on islet morphology and alpha and beta cell subpopulations following immunostaining for glucagon and C-peptide. Following islet isolation, we investigated the correlation between TCF7L2 genotype and in vitro islet functional variables from our in-house pancreatic database.

RESULTS

TCF7L2 rs7903146 (T/T) was associated with reduced basal and glucose-stimulated insulin secretion in isolated human islets, and reduced islet density in whole pancreas. Morphological analysis demonstrated islet size was increased in T/T carriers. Furthermore, rs7903146 was associated with an increased glucagon/C-peptide ratio, especially in bigger islets.

CONCLUSION/INTERPRETATION

The TCF7L2 variant rs7903146 risk allele is associated with impaired insulin secretion, reduction of total islet number and quantitative as well as qualitative morphological changes in human islets. Understanding how the TCF7L2 genotype modulates its activity and how TCF7L2 impacts the islet morphology may aid the design of new therapeutic approaches for the treatment of type 2 diabetes.

Regulation and functional effects of ZNT8 in human pancreatic islets

Zinc ions are essential for the formation of insulin crystals in pancreatic β cells, thereby contributing to packaging efficiency of stored insulin. Zinc fluxes are regulated through the SLC30A (zinc transporter, ZNT) family. Here, we investigated the effect of metabolic stress associated with the prediabetic state (zinc depletion, glucotoxicity, and lipotoxicity) on ZNT expression and human pancreatic islet function. Both zinc depletion and lipotoxicity (but not glucotoxicity) downregulated ZNT8 (SLC30A8) expression and altered the glucose-stimulated insulin secretion index (GSIS). ZNT8 overexpression in human islets protected them from the decrease in GSIS induced by tetrakis-(2-pyridylmethyl) ethylenediamine and palmitate but not from cell death. In addition, zinc supplementation decreased palmitate-induced human islet cell death without restoring GSIS. Altogether, we showed that ZNT8 expression responds to variation in zinc and lipid levels in human β cells, with repercussions on insulin secretion. Prospects for increasing ZNT8 expression and/or activity may prove beneficial in type 2 diabetes in humans.

The nuclear orphan receptor Nur77 is a lipotoxicity sensor regulating glucose-induced insulin secretion in pancreatic β-cells

The NR4A orphan nuclear receptors Nur77, Nurr1, and Nor1 exert multiple cellular and metabolic functions. These transcriptional regulators are activated in response to extracellular stresses, including lipotoxic fatty acids (FA) and proinflammatory cytokines. The contribution of NR4As to β-cell pathophysiology is, however, unknown. We have therefore examined the role of NR4As as downstream contributors to FA-induced β-cell dysfunctions. Human pancreatic islets and insulinoma β-cells were used to determine transcriptional programs elicited by NR4A, which were compared to those triggered by palmitate treatment. Functional studies evaluated the consequence of an increased NR4A expression on insulin biosynthesis and secretion and cell viability in insulinoma β-cells. FA and cytokine treatment increased NR4A expression in pancreatic β-cells, with Nur77 being most highly inducible in murine β-cells. Nur77, Nurr1, or Nor1 modulated common and distinct clusters of genes involved notably in cation homeostasis and insulin gene transcription. By altering zinc homeostasis, insulin gene transcription, and secretion, Nur77 was found to be a major transcriptional mediator of part of FA-induced β-cell dysfunctions. The repressive role of Nur77 in insulin gene regulation was tracked down to protein-protein interaction with FoxO1, a pivotal integrator of the insulin gene regulatory network. The present study identifies a member of the NR4A nuclear receptor subclass, Nur77/NR4A1, as a modulator of pancreatic β-cell biology. Together with its previously documented role in liver and muscle, its role in β-cells establishes Nur77 as an important integrator of glucose metabolism.

Efficient gene delivery and silencing of mouse and human pancreatic islets

Background

In view of the importance of beta cells in glucose homeostasis and the profound repercussions of beta cell pathology on human health, the acquisition of tools to study pancreatic islet function is essential for the design of alternative novel therapies for diabetes. One promising approach toward this goal involves the modification of gene expression profile of beta cells.

Results

This study describes a new method of gene and siRNA delivery into human pancreatic islets by microporation technology. We demonstrated that mild islet distention with accutase greatly enhanced the transfection efficiency without compromising in vitro function (secretion, apoptosis and viability). As an example, the recently identified gene involved in type 2 diabetes, ZnT8, can be over-expressed or silenced by RNA interference using this technology. Microporation can also be used on rodent islets.

Conclusions

Taken together, our results demonstrate that microporation technology can be used to modify gene expression in whole rodent and human islets without altering their in vitro function and will be key to the elucidation of the factors responsible for proper islet function.

5'-AZA induces Ngn3 expression and endocrine differentiation in the PANC-1 human ductal cell line

Neurogenin 3 is necessary for endocrine cell development in the embryonic pancreas and has been shown to induce transdifferentiation duct cells from adult pancreas toward a neuro-endocrine phenotype. Here we discovered that the demethylating agent 5'-Azadeoxycytidine (AZA) induced Ngn3 expression and endocrine differentiation from the PANC-1 human ductal cell line. The expression of markers specific to mature islet cells, i.e., glucagon and somatostatin, was also observed. In addition, we demonstrated that growth factors (betacellulin and soluble factors released during pancreas embryogenesis) increased the level of maturation. Our studies revealed that the PANC-1 model system may provide a basis for elucidating the ductal/endocrine differentiation.

Primary graft function, metabolic control, and graft survival after islet transplantation

OBJECTIVE To investigate the influence of primary graft function (PGF) on graft survival and metabolic control after islet transplantation with the Edmonton protocol. RESEARCH DESIGN AND METHODS A total of 14 consecutive patients with brittle type 1 diabetes were enrolled in this phase 2 study and received median 12,479 islet equivalents per kilogram of body weight (interquartile range 11,072-15,755) in two or three sequential infusions within 67 days (44-95). PGF was estimated 1 month after the last infusion by the beta-score, a previously validated index (range 0-8) based on insulin or oral treatment requirements, plasma C-peptide, blood glucose, and A1C. Primary outcome was graft survival, defined as insulin independence with A1C < or =6.5%. RESULTS All patients gained insulin independence within 12 days (6-23) after the last infusion. PGF was optimal (beta-score > or =7) in nine patients and suboptimal (beta-score < or =6) in five. At last follow-up, 3.3 years (2.8-4.0) after islet transplantation, eight patients (57%) remained insulin independent with A1C < or =6.5%, including seven patients with optimal PGF (78%) and one with suboptimal PGF (20%) (P = 0.01, log-rank test). Graft survival was not significantly influenced by HLA mismatches or by preexisting islet autoantibodies. A1C, mean glucose, glucose variability (assessed with continuous glucose monitoring system), and glucose tolerance (using an oral glucose tolerance test) were markedly improved when compared with baseline values and were significantly lower in patients with optimal PGF than in those with suboptimal PGF. CONCLUSIONS Optimal PGF was associated with prolonged graft survival and better metabolic control after islet transplantation. This early outcome may represent a valuable end point in future clinical trials.

Acute insulin response to arginine in deceased donors predicts the outcome of human islet isolation

Despite a stringent donor selection, human islet isolation remains frustratingly unpredictable. In this study, we measured acute insulin response to arginine (AIRarg), an in vivo surrogate measure of islet mass, in 29 human deceased donors before organ donation, and correlated values with the outcome of islet isolation. Thirteen isolations (45%) met the threshold for clinical islet transplantation. Among all measured donor characteristics, the only discriminating variable between successful or unsuccessful isolations was donor AIRarg (p < 0.01). Using a threshold of 55 microIU/mL (ROC curve AUC: 72%), isolation was successful in 12/19 donors with high AIRarg and in 1/10 donors with low AIRarg (p < 0.001). The negative and positive predictive values were 90 and 63%, respectively. If used to select donors in the entire cohort, AIRarg would have increased our success rate by 40% and avoided 56% of unsuccessful isolations while missing only 8% of successful preparations. Our results suggest that donor AIRarg is markedly superior to body mass index (BMI) and other criteria currently used to predict isolation outcome. If routinely performed in deceased donors, this simple test could significantly reduce the failure rate of human islet isolation.

Evaluation of alternative sites for islet transplantation in the minipig: interest and limits of the gastric submucosa

Since the introduction of glucocorticoid-free immunosuppressive regimens, islet transplantation offers a less invasive alternative to pancreas transplantation. However, complications associated with intraportal islet injection and the progressive functional decline of intrahepatic islets encourage the exploration of alternative sites. Herein we evaluated, in the minipig, the use of the gastric submucosa (GS; group 1, n = 5) for islet transplantation compared with the kidney capsule (KC; group 2, n = 5). Subsequently we attempted to improve the vascularization of the submucosal graft (group 3, n = 5) by the addition of an extracellular matrix rich in growth factors (Matrigel). One month after grafting, we evaluated transplanted islet function in vivo and in vitro. Our study showed better function of islets engrafted in the GS than in the KC (P < .05). Despite the growth factors, Matrigel did not offer a more suitable environment to further improve engraftment (group 3, P < .05). Thus, even if the liver remains the gold standard, the GS represents a potential islet engraftment site, confirming the data obtained in vitro and in the rodent. Offering easy access by endoscopy, this site could constitute an interesting alternative for experimental studies in large mammals and, eventually, for clinical application.

1,25-Dihydroxyvitamin D3 protects human pancreatic islets against cytokine-induced apoptosis via down-regulation of the Fas receptor

Beta cell loss occurs at the onset of type 1 diabetes and after islet graft. It results from the dysfunction and destruction of beta cells mainly achieved by apoptosis. One of the mediators believed to be involved in beta cell apoptosis is Fas, a transmembrane cell surface receptor transducing an apoptotic death signal and contributing to the pathogenesis of several autoimmune diseases. Fas expression is particularly induced in beta cells by inflammatory cytokines secreted by islet-infiltrating mononuclear cells and makes cells susceptible to apoptosis by interaction with Fas-ligand expressing cells. We have previously demonstrated that 1,25(OH)2D3, the active metabolite of vitamin D, known to exhibit immunomodulatory properties and prevent the development of type 1 diabetes in NOD mice, is efficient against apoptosis induced by cytokines in human pancreatic islets in vitro. The effects were mainly mediated by the inactivation of NF-kappa-B. In this study we demonstrated that 1,25(OH)2D3 was also able to counteract cytokine-induced Fas expression in human islets both at the mRNA and protein levels. These results were reinforced by our microarray analysis highlighting the beneficial effects of 1,25(OH)2D3 on death signals induced by Fas activation. Our results provides additional evidence that 1,25(OH)2D3 may be an interesting tool to help prevent the onset of type 1 diabetes and improve islet graft survival.

Acute insulin response of donors is correlated with pancreatic islet isolation outcome in the pig

AIMS/HYPOTHESIS

Unpredictability of islet isolation outcome remains a frustrating and costly issue in the clinical implementation of islet transplantation. The aim of this experimental study was to test the hypothesis that the donor's insulin secretory reserve, an in vivo surrogate of functional pancreatic mass, is correlated with the outcome of islet isolation.

METHODS

Insulin secretory reserve was evaluated in 28 healthy adult minipigs prior to pancreatectomy and islet isolation. Blood glucose and insulinaemia were measured before and 1, 3, 5, 10, 15, 30, 60 and 90 min after glucose infusion. Following total pancreatectomy, islet isolation was performed according to Ricordi's semi-automated method, and the total number of islets obtained was determined. Fasting blood glucose, insulinaemia, acute insulin response (AIR), maximal insulinaemia and the glucose decay constant (K(G)) were calculated, and possible associations with the outcome of islet isolation were assessed.

RESULTS

AIR and maximal insulinaemia after glucose injection were correlated with the outcome of islet isolation (p<0.01). Mean values for AIR and maximal insulinaemia were significantly different between animals in which islet isolation was successful (n=11) vs those in which it was unsuccessful (n=17) (77.6+/-13.7 microU/ml vs 42.3+/-7.8 microU/ml, p<0.05; 144.7+/-21.6 microU/ml vs 71.9+/-10.4 microU/ml, p<0.05, respectively).

CONCLUSIONS/INTERPRETATION

This study suggests that the donor's pancreatic endocrine mass, as estimated by AIR, is a major determinant of the outcome of islet isolation in large mammals. Our results may explain the frustrating variability of human islet isolation outcome and could lead to a new approach for optimising the selection of brain-dead and/or living pancreas donors.

Technique du prélèvement pancréatique pour l'isolement des îlots de Langerhans

AIM OF THE STUDY

The allograft of pancreatic islets represents a potential alternative to insulin therapy in patients suffering from the most severe forms of Type 1 diabetes. Here we report our experience of pancreatic procurement for isolation and islet allograft.

MATERIALS AND METHODS

Pancreata were procured in brain-dead donors. The islets were isolated using techniques developed and validated in pigs and men. Injection of a given preparation was decided after quantitative and qualitative controls. Islets were transplanted in Type 1 diabetic patients already grafted with a kidney or suffering from severe and/or unstable diabetes, after percutaneous or surgical settlement of an intra-portal catheter. Patients received an "Edmonton-like" immunosuppressive protocol. Grafts were repeated once or twice until a total quantity of 10,000 transplanted islet-equivalents was obtained.

RESULTS

Twenty-nine pancreata were procured and 14 preparations were grafted to 7 patients. Eleven graftings were done percutaneously and three were surgical. The initial function of the 14 transplants was confirmed by secretion of C-peptide and decrease of insulin doses. Insulin therapy was completely interrupted in the 5 patients having received at least two grafts.

CONCLUSION

These preliminary clinical results confirmed that the isolation technique of human islets and the technique of pancreas procurement are mastered by our team. If the results of this assay (assessment one year after graft) confirm our hopes, we will be able to offer islet allografts to an increasing number of patients with severe Type 1 diabetes.

Expression of progenitor cell markers during expansion of sorted human pancreatic beta cells

Functional pancreatic beta cell mass is dynamic and although fully differentiated, beta cells are capable of reentering the cell cycle upon appropriate stimuli. Stimulating regeneration-competent cells in situ is clearly the most desirable way to restore damaged tissue. Regeneration by dedifferentiation and transdifferentiation is a potential source of cells exhibiting a more developmentally immature phenotype and a wide differentiation potential. In this context and to gain a better understanding of the transformation induced in human beta cells during forced in vitro expansion, we focused on identifying differences in gene expression along with phenotypical transformation between proliferating and quiescent human beta cells. FACS-purified beta cells from three different human pancreata were cultured during 3-4 months (8-10 subcultures) on HTB-9 cell matrix with hepatocyte growth factor. Gene expression profiling was performed on cells from each subculture on "in-house" pancreas-specific microarrays consisting of 218 genes and concomitant morphological transformations were studied by immunocytochemistry. Immunocytochemical studies indicated a shift from epithelial to neuroepithelial cell phenotype, including progenitor cell features such as protein gene product 9.5 (PGP 9.5), Reg, vimentin, and neurogenin 3 protein expression. The expression of 49 genes was downregulated, including several markers of endocrine differentiation while 76 were induced by cell expansion including several markers of progenitor cells. Their pattern also argues for the transdifferentiation of beta cells into progenitor cells, demonstrating neuroepithelial features and overexpressing both PBX1, a homeodomain protein that can bind as a heterodimer with PDX1 and could switch the nature of its transcriptional activity, and neurogenin 3, a key factor for the generation of endocrine islet cells. Our study of the machinery that regulates human beta cell expansion and dedifferentiation may help elucidate some of the critical genes that control the formation of adult pancreatic progenitor cells and hence design targets to modify their expression in view of the production of insulin-secreting cells.

Implication of Reg I in human pancreatic duct-like cells in vivo in the pathological pancreas and in vitro during exocrine dedifferentiation

A feature associated frequently with the pathologic pancreas is the presence of tubular complexes produced by a phenotypic modulation of acinar cells that take on the characteristics of ductular cells. Since the type I Reg gene, an acinar cell product, is increased in the pancreas following an acinar injury, we aimed to evaluate whether the Reg I protein might be involved in this dedifferentiation process in the human pancreas. We studied duct-like structures in fixed human pathologic pancreatic tissues and human cells with a ductal phenotype obtained by culturing human exocrine preparations. Immunocytochemistry, Western blotting, and RT-PCR were applied for detection of type I Reg. Reg I was observed not only in acinar cells but also in the duct-like cells and dilated duct cells, both positive for cytokeratin 19. However, none of the other acinar markers was observed in these cells. In vitro, human acinar cells dedifferentiated, losing their acinar phenotype, but expression of Reg I remained constant throughout the culture duration. Furthermore, Reg I was not associated with proliferation. We demonstrated that Reg I expression was linked to acinar cell dedifferentiation. We postulate that Reg I might be used as a marker to understand the events leading to phenotypic changes of acinar cells to address the physiological role of Reg I in the pancreas.

Kinetics of diabetes-associated autoantibodies after sequential intraportal islet allograft associated with kidney transplantation in type 1 diabetes

OBJECTIVE

Presence or occurrence of pancreas auto-antibodies (aAb) has been shown to be of poor prognosis for islet cell transplantation. The aim of the study was to monitor the kinetics of these aAb after sequential intra-portal islet plus kidney transplantation with pre-Edmonton immunosuppressive regimen in order to determine whether the sequential protocol of transplantation was involved in the occurrence of the immune response.

PATIENTS AND METHODS

Three patients with IDDM and a previous (IAK) or simultaneous (SIK) kidney transplantation received 3 or 4 ABO compatible islet preparations. Islets (> 8 000 IEQ/kg post culture) were sequentially transplanted within a 12 day period via a per-cutaneous catheter. Immunosuppressive treatment included cyclosporine, steroïds and mycophenolate. Plasma ICAs, GAD 65, IA2 and C peptide (C-p) levels were monitored. Type II HLA phenotype was determined in donors and recipients.

RESULTS

Patient #1 had high anti-GAD levels (26.5 UI/l) before the IAK, while anti-IA2 and ICA levels were low. After the transplantation, C-p levels increased to 4.9 ng/ml at one month before becoming undetectable at 2 months. GAD levels remained high, ICA and IA2 aAb were undetectable. Patients #2 and #3 did not have significant levels of aAb before the islet transplantation. A slight increase in GAD was observed with each islet transplantation, followed by an overt but transient increase in ICA. IA2 levels remained undetectable. Three months after the transplantation and 2 weeks after the increase of ICA, C-p levels, that were >3.4 ng/ml at one month, fell below 0.2 (N: 0.5-2).

CONCLUSION

The immunosuppressive regimen used in kidney transplantation is unable to control perfectly anti-pancreas aAb production. Moreover, these results seem to indicate that the benefits of sequential islet transplantation lie more in the increased islet mass they provide than in potential immune benefit.

Non-esterified fatty acids are deleterious for human pancreatic islet function at physiological glucose concentration

AIMS/HYPOTHESIS

Whether excess glucose (glucotoxicity) and excess non-esterified fatty acids (lipotoxicity) act synergistically or separately to alter beta-cell function on Type 2 diabetes remains controversial. We examined the influence of non-esterified fatty acids, with or without concomitant increased glucose concentrations, on human islet function and on the expression of genes involved in lipid metabolism.

METHODS

Human islets isolated from non-diabetic and non-obese donors were cultured with 5.5, 16 or 30 mmol/l glucose, and when appropriate with 1 or 2 mmol/l non-esterified fatty acids. After 48 h, glucose-stimulated insulin secretion, insulin content, triglyceride content and expression of different genes were evaluated.

RESULTS

Non-esterified fatty acids decreased glucose-stimulated insulin secretion, insulin content and increased triglyceride content of human isolated islets, independently from the deleterious effect of glucose. Increased glucose concentrations also decreased glucose-stimulated insulin secretion and insulin content, but had no influence on triglyceride content. Glucose-stimulated insulin secretion of islets appeared to be significantly correlated with their triglyceride content. Glucose and non-esterified fatty acids modified the gene expression of carnitine palmitoyltransferase-I, acetyl-CoA carboxylase, acyl-CoA oxidase and uncoupling protein 2.

CONCLUSION/INTERPRETATION

In our model of isolated human islets, increased glucose and non-esterified fatty acids separately reproduced the two major beta-cell alterations observed in vivo, i.e. loss of glucose-stimulated insulin secretion and reduction in islet insulin content. Our results also suggest that this deleterious effect was, at least in part, mediated by modifications in lipid metabolism gene expression.

1,25-dihydroxyvitamin D3 protects RINm5F and human islet cells against cytokine-induced apoptosis: implication of the antiapoptotic protein A20

Transplantation of islets of Langerhans is a potential cure for type 1 diabetes, but its success is hampered by destruction of the islets. The data presented herein suggest that the active metabolite of vitamin D3 [1,25-(OH)2D3] may promote islet cell survival by modulating the effects of inflammatory cytokines, which contribute to beta-cell demise. We investigated some of the mechanisms triggering the apoptotic machinery in rat insulinoma RINm5F cells and human islets treated with IL-1beta plus interferon-gamma plus TNFalpha and assessed the effects of 1,25-(OH)2D3 in these processes. Mitochondrial transmembrane permeability and apoptotic features, determined by percentage of sub-G1 cells, quantitation of DNA strand breaks, and Hoechst staining, were significantly increased by cytokines and reverted toward control values by 1,25-(OH)2D3 cotreatment. The cytoprotection of cells correlated with the abrogation of cytokine-induced nitric oxide production. The activation of nuclear factor-kappaB plays a key role in the different pathways implicated in nitric oxide generation. We demonstrated for the first time, in both RINm5F cells and human islets, that 1,25-(OH)2D3 was able to induce and maintain high levels of A20, an antiapoptotic protein known to block nuclear factor-kappaB activation. Our study showed a clear efficiency of 1,25-(OH)2D3 on the apoptotic machinery triggered by cytokines in beta-cells and suggests that 1,25-(OH)2D3 could help overcome a major obstacle encountered in the cellular therapy of diabetes, such as nonfunction in the immediate posttransplantation period.

[Coagulation activation with intraportal islets of Langerhans transplantation in swine]

STUDY AIM

Intraportal islet allograft appears to be one of the promising treatments for type I diabetes. However, many limiting factors persist. An activation of the coagulation cascade upon contact with islets, has been reported recently in vitro and could play a crucial role in a non specific inflammatory reaction and favour the specific immune reaction. The aim of this experimental study was to confirm in vivo this activation of the coagulation cascade.

MATERIAL AND METHODS

An allogenic islets preparation or a material control (inert microbeads) was injected intraportally, in Large White pigs (n = 26), associated with or without an anticoagulant treatment (heparin). Systemic markers of haemostasis were measured in pigs for 72 hours following injection of the studied material.

RESULTS

The thrombin-antithrombin complex increased and platelet count decreased in groups receiving preparation of islets, both indicators of an activation of the coagulation cascade. This activation was proportional to the injected volume and was partially attenuated by heparin. No activation was observed in pigs receiving the material control.

CONCLUSION

The activation of the coagulation cascade and the non specific inflammatory reaction could be one of the obstacles to the success of the islet allografts. The use of anticoagulant and anti-inflammatory molecules could potentially allow an improvement of the present results of islet allograft.

[Human pancreatic stem cell and diabetes cell therapy]

Cell therapy offers today important perspectives for the treatment of type 1 diabetes. The current utilization of primary human islets of Langerhans nevertheless forbids all hope of developing this treatment on a large scale. The recent description of the persistence of stem cells capable of proliferating and differentiating in the adult pancreas offers an attractive alternative for the production in vitro of homologous insulin-secreting cells. We first reproduced in vitro from human islet preparations the proliferation of ductal epithelial structures and their progressive organization. Thereafter, we focused on the description of a reproducible source of human ductal cells by the transdifferentiation of exocrine preparations. More recently we described in these exocrine derived ductal cells the the expression the of insulin promoter factor-1 (IPF-1/otherwise known as PDX-1), a transcription factor essential for the differentiation of ductal cells into endocrine cells during both development and pancreatic regeneration. If the proliferation and differentiation of these cells is confirmed, this approach could lead to the description of an abundant source of human pancreatic stem cells for the production ex vivo of human insulin secreting cells and may even allow autologous cell therapy, in the absence of immunosuppression.

Identification and purification of functional human beta-cells by a new specific zinc-fluorescent probe

Pancreatic beta-cells contain large amounts of zinc. We took advantage of this to try to localize, quantify, and isolate insulin-producing cells from islet preparations. Our study was designed to identify a non-toxic zinc-sensitive fluorescent probe able to selectively label labile zinc in viable beta-cells and to exhibit excitation and emission wavelengths in the visible spectrum, making this technique exploitable by most instruments. We tested Newport Green, a probe excitable at 485 nm with a dissociation constant in the micromolar range corresponding to a low affinity for zinc. The loading of the lipophilic esterified form of Newport Green was easy, rapid, specific, and non-toxic to cells. Confocal microscopy highlighted an intense fluorescence associated with secretory granules. Regression analyses showed a good relationship between zinc fluorescence and islet number (r = 0.98) and between zinc fluorescence and insulin content (r = 0.81). The determination of Zn fluorescence per DNA enabled us to assess the quality of the different islet preparations intended for islet allografting in terms of both purity and viability. Cell sorting of dissociated Newport Green-labeled cells resulted in a clear separation of beta-cells, as judged by insulin content per DNA and immunocytochemical analysis. This zinc probe, the first able to specifically label living cells in the visible spectrum, appears very promising for beta-cell experimentation, both clinically and for basic research.

Beneficial effect of 1,25 dihydroxyvitamin D3 on cytokine-treated human pancreatic islets

We examined whether 1,25 dihydroxyvitamin D(3) (1,25 D(3)), the active form of vitamin D involved in the regulation of the immune system, may also protect human pancreatic islet cells from destruction induced by cytokines. In this study, we specifically investigated the effect of 1,25 D(3) on oxidative stress and major histocompatibility complex (MHC) induction, both implicated in cytokine-induced islet cell dysfunction and destruction. We also investigated the effects of 1,25 D(3) on interleukin (IL)-6, a pleiotropic cytokine implicated in the pathogenesis of immunoinflammatory disorders. Human pancreatic islets, isolated from heart-beating donors, were treated with a combination of three cytokines, IL-1beta+tumor necrosis factor alpha+interferon gamma, in the presence or absence of vitamin D, and compared with with untreated control cells. Metabolic activity was assessed by cell viability and insulin content. Oxidative stress was estimated by heat shock protein 70 (hsp70) expression, cell manganese superoxide dismutase (MnSOD) activity and nitrite release, a reflexion of nitric oxide (NO) synthesis. Variation of immunogenicity of islet preparations was determined by analysis of the MHC class I and class II transcripts. Inflammatory status was evaluated by IL-6 production. After 48 h of contact with cytokines, insulin content was significantly decreased by 40% but cell viability was not altered. MHC expression significantly increased six- to sevenfold as well as NO and IL-6 release (two- to threefold enhancement). MnSOD activity was not significantly induced and hsp70 expression was not affected by the combination of cytokines. The addition of 1,25 D(3) significantly reduced nitrite release, IL-6 production and MHC class I expression which then became not significantly different from controls. These results suggest that the effect of 1,25 D(3) in human pancreatic islets cells may be a reduction of the vulnerability of cells to cytotoxic T lymphocytes and a reduction of cytotoxic challenge. Hence, 1,25 D(3) might play a role in the prevention of type 1 diabetes and islet allograft rejection.