Anne Wojtusciszyn

The contribution of glucose variability to asymptomatic hypoglycemia in persons with type 2 diabetes

BACKGROUND The present study was designed to define the relative contributions of glucose variability and ambient glycemia to the incidence of asymptomatic hypoglycemia in type 2 diabetes. METHODS Two hundred twenty-two persons with type 2 diabetes were divided into three groups: Group I (n = 53) on insulin sensitizers alone, Group II (n = 87) on oral hypoglycemic agents (OHAs) to include at least one insulin secretagogue, and Group III (n = 82) on insulin alone or in combination with OHAs. Ambient mean glucose concentration (MG) values (in mmol/L) and glycemic variability (SD around the mean glucose value) (in mmol/L) or mean amplitude of glycemic excursions (in mmol/L) were assessed by a continuous glucose monitoring system. Asymptomatic hypoglycemia was recorded over a 48-h period. Poisson regression analysis was used for assessing the potential predictors of hypoglycaemia. RESULTS The best model fit was obtained with the two following explanatory variables: MG and SD. Hypoglycemia frequency was negatively associated with MG and positively with SD: Log (number of hypoglycemia episodes) = 1.37 - (0.72 × MG) + (1.33 × SD). Odds ratios (95% confidence interval) for hypoglycemic risk were significantly different from 1 for MG at 0.96 (0.95-0.97) (P < 0.0001) and for SD at 1.08 (1.06-1.10) (P < 0.0001). In addition, the risk for hypoglycemia was completely or virtually eliminated when the SD was <1.7 mmol/L irrespective of the ambient glucose level and treatment modality. CONCLUSIONS As the risk of asymptomatic hypoglycemia increases in the presence of increased glucose variability, avoidance of excess glucose fluctuations should be an important consideration for either reducing or preventing the risk of hypoglycemia in type 2 diabetes.

Expectations and strategies regarding islet transplantation: metabolic data from the GRAGIL 2 trial

Background. Whether islet transplantation should be aimed at restoring insulin independence or providing adequate metabolic control is still debated. The GRAGIL2 trial was designed as a phase 1–2 study where primary outcome was the rate of insulin independence, and secondary outcome was the success rate defined by a composite score based upon basal C-peptide, HbA1c, hypoglycemic events, and exogenous insulin needs. Methods. C-peptide negative type 1 brittle diabetic patients experiencing severe hypoglycemia were eligible to receive a maximum of two islet preparations totalizing 10,000 IE/kg or more, with a threshold of 5,000 IE/kg for the first infusion, according to the Edmonton protocol, within the Swiss-French GRAGIL multicentric network. A sequential analysis with a triangular test was performed in every five patients after 6- and 12-month follow-up. Maximal inefficiency was set at 40% and minimal efficiency at 66%. Results. From September 2003 to October 2005, 10 patients were included. Median waiting time was 6.7 months (first injection) and 9 weeks (second injection). All but one patient received 11,089±505 IE/kg: one received a single graft of 5398 IE/kg. At 6 months, insulin independence and composite success rates were 6 of 10 and 6 of 10, respectively. At 12 months, insulin independence was observed in 3 of 10 patients and success in 5 of 10 patients. Conclusion. Based upon our sequential analysis settings, islet transplantation failed to achieve the primary goal, insulin independence, but tended to succeed in reaching the secondary goal, successful metabolic control. Currently it appears to be a successful biological closed-loop glucose control method for brittle diabetes.

Sequential Kidney/Islet Transplantation: Efficacy and Safety Assessment of a Steroid-Free Immunosuppression Protocol

The aim of this study was to assess the efficiency and safety of the Edmonton immunosuppression protocol in recipients of islet‐after‐kidney (IAK) grafts. Fifteen islet infusions were administered to 8 patients with type 1 diabetes and a functioning kidney graft. Immunosuppression was switched on the day of transplantation to a regimen associating sirolimus‐tacrolimus‐daclizumab. Insulin‐independence was achieved in all patients for at least 3 months, with an actual rate of 71% at 1 year after transplantation (5 of 7 patients). After 24‐month mean follow‐up, five have ongoing insulin independence, 11–34 months after transplantation, with normal HbA1c, fructosamine and mean amplitude of glycemic excursions (MAGE) values. Results of arginine‐stimulation tests improved over time, mostly after the second islet infusion. Severe adverse events included bleeding after percutaneous portal access (n = 2), severe pneumonia attributed to sirolimus toxicity (n = 1), kidney graft loss after immunosuppression discontinuation (n = 1), reversible humoral kidney rejection (n = 1) and fever of unknown origin (n = 1). These data indicate that the Edmonton approach can be successfully applied to the IAK setting. This procedure is associated with significant side effects and only patients with stable function of the kidney graft should be considered. The net harm versus benefit has not yet been established and will require further studies with larger numbers of enrolled subjects.

Quality of life after islet transplantation: data from the GRAGIL 1 and 2 trials.

Background  Rigorous assessment of health‐related quality of life (HRQL) is mandatory to establish the benefits of islet transplantation.

Five-Year Metabolic, Functional, and Safety Results of Patients With Type 1 Diabetes Transplanted With Allogenic Islets Within the Swiss-French GRAGIL Network

OBJECTIVE To describe the 5-year outcomes of islet transplantation within the Swiss-French GRAGIL Network. RESEARCH DESIGN AND METHODS Retrospective analysis of all subjects enrolled in the GRAGIL-1c and GRAGIL-2 islet transplantation trials. Parameters related to metabolic control, graft function, and safety outcomes were studied. RESULTS Forty-four patients received islet transplantation (islet transplantation alone [ITA] 24 patients [54.5%], islet after kidney [IAK] transplantation 20 patients [45.5%]) between September 2003 and April 2010. Recipients received a total islet mass of 9,715.75 ± 3,444.40 IEQ/kg. Thirty-four patients completed a 5-year follow-up, and 10 patients completed a 4-year follow-up. At 1, 4, and 5 years after islet transplantation, respectively, 83%, 67%, and 58% of the ITA recipients and 80%, 70%, and 60% of the IAK transplant recipients reached HbA1c under 7% (53 mmol/mol) and were free of severe hypoglycemia, while none of the ITA recipients and only 10% of the IAK transplant recipients met this composite criterion at the preinfusion stage. Thirty-three of 44 patients (75%) experienced insulin independence during the entire follow-up period, with a median duration of insulin independence of 19.25 months (interquartile range 2–58). Twenty-nine of 44 recipients (66%) exhibited at least one adverse event; 18 of 55 adverse events (33%) were possibly related to immunosuppression; and complications related to the islet infusion (n = 84) occurred in 10 recipients (11.9%). CONCLUSIONS In a large cohort with a 5-year follow-up and in a multicenter network setting, islet transplantation was safe and efficient in restoring good and lasting glycemic control and preventing severe hypoglycemia in patients with type 1 diabetes.

Toward Defining the Threshold Between Low and High Glucose Variability in Diabetes.

OBJECTIVE To define the threshold for excess glucose variability (GV), one of the main features of dysglycemia in diabetes. RESEARCH DESIGN AND METHODS A total of 376 persons with diabetes investigated at the University Hospital of Montpellier (Montpellier, France) underwent continuous glucose monitoring. Participants with type 2 diabetes were divided into several groups—groups 1, 2a, 2b, and 3 (n = 82, 28, 65, and 79, respectively)—according to treatment: 1) diet and/or insulin sensitizers alone; 2) oral therapy including an insulinotropic agent, dipeptidyl peptidase 4 inhibitors (group 2a) or sulfonylureas (group 2b); or 3) insulin. Group 4 included 122 persons with type 1 diabetes. Percentage coefficient of variation for glucose (%CV = [(SD of glucose)/(mean glucose)] × 100) and frequencies of hypoglycemia (interstitial glucose <56 mg/dL [3.1 mmol/L]) were computed. RESULTS Percentages of CV (median [interquartile range]; %) increased significantly (P < 0.0001) from group 1 (18.1 [15.2–23.9]) to group 4 (37.2 [31.0–42.3]). In group 1, the upper limit of %CV, which served as reference for defining excess GV, was 36%. Percentages of patients with %CVs above this threshold in groups 2a, 2b, 3, and 4 were 0, 12.3, 19.0, and 55.7%, respectively. Hypoglycemia was more frequent in group 2b (P < 0.01) and groups 3 and 4 (P < 0.0001) when subjects with a %CV >36% were compared with those with %CV ≤36%. CONCLUSIONS A %CV of 36% appears to be a suitable threshold to distinguish between stable and unstable glycemia in diabetes because beyond this limit, the frequency of hypoglycemia is significantly increased, especially in insulin-treated subjects.

Computer-Assisted Digital Image Analysis to Quantify the Mass and Purity of Isolated Human Islets Before Transplantation

Background. Accurate determination of islet purity and mass before transplantation is an essential part of quality control. The standard method is based on manual evaluation of these parameters and thus subjective and prone to errors. Therefore, we developed a computerized approach aimed at evaluating more objectively the number and purity of isolated human islets. Methods. Islets were isolated and purified from human pancreata according to a standard method. For each preparation, two samples were dithizone stained. One sample was analyzed manually by microscopy, following the standard procedure, and the other was digitally photographed for both digital manual and computerized analyses. Computerized analysis was performed using the MetaMorph and ImageJ softwares to automatically quantify purity and size of islets. Islet equivalent (IEQ) number was calculated using the Ricordi algorithm or considering the individual volume of each islet. Computerized analysis was validated using calibrated red glass microspheres. Results. When digital manual and computerized analyses were compared, mean values of total islet number, IEQ number calculated using the Ricordi algorithm, and purity were similar. Comparisons of individual values showed good correlations (r2≥0.89). By standard manual analysis, total islet number and purity were higher and IEQ number similar compared with digital manual and computerized analyses. IEQ number was 10% lower (P<0.0001) when calculated using individual sphere volumes compared with the Ricordi algorithm. Measurement of red glass microspheres showed identical values comparing standard manual and computerized analyses. Conclusions. Computer-assisted digital image analysis is an objective and a reliable method for analyzing pancreatic islets before transplantation.

Detection of insulin mRNA in the peripheral blood after human islet transplantion predicts deterioration of metabolic control

Recent updates of the Edmonton trial have shown that insulin independence is progressively lost in approximately 90% of islet transplant recipients over the first 5 years. Early prediction of islet graft injury could prompt the implementation of strategies attempting to salvage the transplanted islets. We hypothesize that islet damage is associated with the release and detection of insulin mRNA in the circulating blood. Whole blood samples were prospectively taken from 19 patients with type 1 diabetes receiving 31 islet transplants, immediately prior to transplantation and at regular time‐points thereafter. After RNA extraction, levels of insulin mRNA were determined by quantitative reverse tran‐scriptase‐polymerase chain reaction. All patients exhibited a primary peak of insulin mRNA immediately after transplantation, without correlation of duration and amplitude with graft size or outcome. Twenty‐five subsequent peaks were observed during the follow‐up of 17 transplantations. Fourteen secondary peaks (56%) were closely followed by events related to islet graft function. Duration and amplitude of peaks were higher when they heralded occurrence of an adverse event. Peaks of insulin mRNA can be detected and are often associated with alterations of islet graft function. These data suggest that insulin mRNA detection in the peripheral blood is a promising method for the prediction of islet graft damage.

Acute nutrient regulation of the mitochondrial glutathione redox state in pancreatic β-cells

The glucose stimulation of insulin secretion by pancreatic β-cells depends on increased production of metabolic coupling factors, among which changes in NADPH and ROS (reactive oxygen species) may alter the glutathione redox state (EGSH) and signal through changes in thiol oxidation. However, whether nutrients affect EGSH in β-cell subcellular compartments is unknown. Using redox-sensitive GFP2 fused to glutaredoxin 1 and its mitochondria-targeted form, we studied the acute nutrient regulation of EGSH in the cytosol/nucleus or the mitochondrial matrix of rat islet cells. These probes were mainly expressed in β-cells and reacted to low concentrations of exogenous H2O2 and menadione. Under control conditions, cytosolic/nuclear EGSH was close to -300 mV and unaffected by glucose (from 0 to 30 mM). In comparison, mitochondrial EGSH was less negative and rapidly regulated by glucose and other nutrients, ranging from -280 mV in the absence of glucose to -299 mV in 30 mM glucose. These changes were largely independent from changes in intracellular Ca(2+) concentration and in mitochondrial pH. They were unaffected by overexpression of SOD2 (superoxide dismutase 2) and mitochondria-targeted catalase, but were inversely correlated with changes in NAD(P)H autofluorescence, suggesting that they indirectly resulted from increased NADPH availability rather than from changes in ROS concentration. Interestingly, the opposite regulation of mitochondrial EGSH and NAD(P)H autofluorescence by glucose was also observed in human islets isolated from two donors. In conclusion, the present study demonstrates that glucose and other nutrients acutely reduce mitochondrial, but not cytosolic/nuclear, EGSH in pancreatic β-cells under control conditions.

The role of macrophage migration inhibitory factor in mouse islet transplantation.

Background. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many tissues including pancreatic &bgr;-cells. Methods. This study investigates the impact of MIF on islet transplantation using MIF knock-out (MIFko) mice. Results. Early islet function, assessed with a syngeneic marginal islet mass transplant model, was enhanced when using MIFko islets (P<0.05 compared with wild-type [WT] controls). This result was supported by increased in vitro resistance of MIFko islets to apoptosis (terminal deoxynucleotide tranferase-mediated dUTP nick-end labeling assay), and by improved glucose metabolism (lower blood glucose levels, reduced glucose areas under curve and higher insulin release during intraperitoneal glucose challenges, and in vitro in the absence of MIF, P<0.01). The beneficial impact of MIFko islets was insufficient to delay allogeneic islet rejection. However, the rejection of WT islet allografts was marginally delayed in MIFko recipients by 6 days when compared with WT recipient (P<0.05). This effect is supported by the lower activity of MIF-deficient macrophages, assessed in vitro and in vivo by cotransplantation of islet/macrophages. Leukocyte infiltration of the graft and donor-specific lymphocyte activity (mixed lymphocyte reaction, interferon &ggr; ELISPOT) were similar in both groups. Conclusion. These data indicate that targeting MIF has the potential to improve early function after syngeneic islet transplantation, but has only a marginal impact on allogeneic rejection.