Macrophage activation in type 1 diabetic patients with catheter obstruction during peritoneal insulin delivery with an implantable pump

Strategies for extended lifetime of implantable intraperitoneal insulin catheters

Implantable insulin infusion systems using the intra-peritoneal route have dramatically changed the management of diabetes paving the way toward the realization of the potential "holy grail" of a fully implantable artificial pancreas. However, the wear duration of delivery catheters is compromised by the foreign body-mediated immune response. Both occlusion material present at the distal catheter tip end and fibrotic encapsulation surrounding the catheters influence the controlled and precise delivery of insulin, which eventually leads to the need for surgical intervention. The novel part of the current work is the investigation of the roles of implant physical properties (catheter size and tip configuration), as well as local inflammation control (through utilization of an anti-inflammatory agent) on the host fibrotic response using a previously developed animal model. The cellular and molecular response, the medication delivery efficacy as well as the ability to flush the catheters were examined and further compared among the different mitigation strategies. Reduction in catheter size as well as tuning the tip configuration from a cone shape to a round shape showed delayed host recognition and delayed propagation of the fibrotic response. However, the round shaped tips had an increased occurrence of lumen occlusion as a result of flow change. It became apparent that changing the physical properties of the catheters was not a long-term solution to catheter obstructions caused by the foreign body reaction. In comparison, control of the local inflammatory response through the use of an anti-inflammatory agent demonstrated a promising strategy for maintenance of catheter functionality without any type of obstructions. These finding will have a large impact toward the development of long-term use catheters for continuous intraperitoneal insulin infusion.

Root cause determination of intraperitoneal catheter obstructions: Insulin amyloid aggregates vs foreign body reaction

Continuous intraperitoneal insulin infusion, from an implanted insulin pump connected to a catheter that delivers insulin directly to the peritoneal cavity has many clinical advantages for patients with Type 1 diabetes. However, the ongoing incidence of catheter obstructions remains a barrier to the widespread use of this therapy. To date, the root cause of these obstructions remains unknown. Here, a two-year clinical investigation was conducted, along with the development of an animal model to enable a mechanistic investigation into this issue. This novel animal model was able to mimic the catheter obstructions that occur in patients and, fortuitously, at an accelerated rate. This model allowed for independent assessment of each potential cause associated with catheter obstructions to help identify the root cause. Both macroscopic and microscopic analysis were conducted with regards to the onset and progression of catheter obstructions, along with monitoring of insulin delivery. Interestingly, although insulin aggregation occurs in insulin pumps and insulin aggregates were found in some catheter obstructions, insulin is unlikely to be the root cause, since obstructions also occurred in the control groups where only diluent (no insulin) was administered to the animals. Inflammatory cells, different phenotypes of fibroblasts, as well as collagen were observed in all obstructed catheters explanted from the patients and the animals. The presence of these cells and collagen is indicative of a typical foreign body reaction. In addition, the dynamic change in the fibroblasts with respect to morphology, phenotype, and spatial distribution suggests that tissue irritation-mediated epithelial to mesenchymal transition plays a role in catheter obstructions.

Finding the right route for insulin delivery - an overview of implantable pump therapy

INTRODUCTION

Implantable pump therapy adopting the intraperitoneal route of insulin delivery has been available for the past three decades. The key rationale for implantable pump therapy is the restoration of the portal-peripheral insulin gradient of the normal physiology. Uptake in clinical practice is limited to specialized centers and selected patient populations. Areas covered: Implantable pump therapy is discussed, including technical aspects, rationale for its use, and glycemic and non-glycemic effects. Target populations, summaries of clinical studies and issues related to implantable pump therapy are highlighted. Limitations of implantable pump therapy and its future outlook in clinical practice are presented. Expert opinion: Although intraperitoneal insulin delivery appears closer to the normal physiology, technical, pharmacological, and costs barriers prevent a wider adoption. Evidence from clinical studies remains scarce and inconclusive. As a consequence, the use of implantable pump therapy will be confined to a small population unless considerable technological progress is made and well-conducted studies can demonstrate glycemic and/or non-glycemic benefits justifying wider application.

Advances in pump technology: insulin patch pumps, combined pumps and glucose sensors, and implanted pumps

This review discusses the most recent developments in insulin pump technology. The benefits of the insulin pump to patients with type 1 diabetes are recognized both for its metabolic effectiveness and its positive effects on quality of life. The current pumps are reliable, small and light, and are becoming more and more sophisticated. Nevertheless, there remain practical and psychological constraints for the patient. However, recent patch-pump advances should simplify the technical aspects of pump treatment and enhance patient comfort. Another advance combines the insulin pump with a glucose sensor. Such a combination is logical for optimizing pump use and, to that end, developing an automated or 'closed-loop'system that permits the delivery of subcutaneous insulin adjusted according to measured levels of subcutaneous glucose. Finally, implanted insulin pumps have proven their worth not only because of their simple use, but also for their contribution in the artificial pancreas project. Indeed, the prompt response with intraperitoneal administration of insulin makes it of interest for use in a closed-loop system.

Circulating insulin antibodies: influence of continuous subcutaneous or intraperitoneal insulin infusion, and impact on glucose control

The purification of animal insulin preparations and the use of human recombinant insulin have markedly reduced the incidence, but not completely suppressed, the development of anti-insulin antibodies (IAs). Advances in technologies concerning the mode of delivery of insulin, i.e. continuous subcutaneous insulin infusion (CSII), continuous peritoneal insulin infusion (CPII) and more recently inhaled insulin administration, appear to significantly increase circulating levels of immunoglobulin G (IgG) anti-IAs in diabetic patients. However, the increase is usually moderate and mostly transient as compared to previous observations with poorly purified animal insulin preparations. The clinical impact of these circulating anti-IAs remains unclear. Nevertheless, several studies have suggested that antibodies could retard insulin action, leading to a worsening of postprandial hyperglycaemia and/or serve as a carrier, thus leading to unexpected hypoglycaemia. CPII may be associated with more marked and sustained increase in IAs levels, possibly related to the use of an unstable insulin and the formation of immunogenic aggregates of insulin. The possible clinical consequences of these high levels of IAs remain to be evaluated because a low-glucose morning syndrome or severe insulin resistance with ketone bodies production have been reported in some cases. In conclusion, even if CSII and CPII may promote the development of circulating IAs, this increase does not lead to immunological insulin resistance, compared to that previously described with animal non-purified insulin preparations, and seems to have only marginal influence on blood glucose control or complications in most diabetic patients.

Implantable insulin delivery pumps

Implantable insulin delivery pumps are a response to the search for an insulin therapy that would be more physiological, more comfortable and, finally, better adapted to instantaneous insulin needs by their connection to a long term glucose sensor. The last decade has been devoted to their technical finalization and to the acquisition of the clinical knowledge on how to use them, so that these devices can be safe and reliable. The forthcoming availability on the market of the specific insulin formulation they require and the present development of glucose sensors are two favourable conditions for the diffusion of this technology aiming at an improved diabetes treatment. This review summarizes the rationale for the choice of intraperitoneal insulin route, the key-steps in assessing their feasibility and effectiveness in blood glucose control of diabetic patients, and the present development of this technique toward an implantable artificial beta-cell.

A case of insulin-induced localized lobular panniculitis with evidence for the phagocytosis of insulin by histiocytes

Insulin-induced localized lipoatrophy is a well-known localized side effect. Although an immune process has been suggested as its etiology, no definitive evidence has been reported to show that insulin is involved. Here, we report the first evidence for the phagocytosis of insulin by histiocytes as a very early stage of lipoatrophy, which was reproducible in two different lobular panniculitis tissues from a 71 year-old male patient. He had taken a subcutaneous insulin injection in his arms because of a sight disturbance. Since these subcutaneous tumors were likely due to inflammation by insulin, a biopsy sample was taken from the subcutaneous tumor of his right arm with his consent. The primary antibodies for insulin (1 : 200) and CD68 (1 : 50) were obtained from DAKO (guinea pig anti-insulin and mouse anti-human CD68). HE staining revealed the infiltration of mononuclear cells and histiocytes into the subcutaneous fat tissue, and some parts of this tissue had fibrosis with rich collagen fibers. These findings are consistent with a lobular panniculitis. Some histiocytes contained intracellular substances with a positive immunoreactivity to insulin. This activity was reduced when the anti-insulin antibody was preincubated with an excess amount of insulin antigen. The same substances were also positive to CD68. Thus, the phagocytosis of insulin by histiocytes appears to occur in this region. Therefore, the activation of subcutaneous macrophages by the complex of insulin and insulin antibodies may account for the initial autoimmune process.

Implantable insulin pumps. A position statement about their clinical use

AIM

To review clinical use of implantable insulin pumps and to suggest indications for this therapy.

METHODS

The EVADIAC group performed a review of published reports on implantable insulin pumps for the last 15 years and analyzed its own centralized database. From this update, a position statement on indications of this therapy is drawn.

RESULTS

Published papers mostly report safety and effectiveness data from observational cumulated experiences of 15-350 patient-years. While HbA(1c) reduction does not reach statistical significance in all reported studies, improvement of blood glucose stability and reduction of severe hypoglycaemia appear as constant characteristics of this therapy. When compared to subcutaneous insulin therapy in randomized controlled studies, implantable pumps allow significantly reduced blood glucose fluctuations and improved quality of life in both type 1 and type 2 diabetic patients, and a significant weight decrease in type 2 diabetic patients. While the EVADIAC registry shows the reduced occurrence of pump-pocket complications thanks to preventive measures and a lower incidence of catheter obstructions following improvements of catheter design, underdelivery due to insulin aggregation in pumps remains a recurrent although reversible issue. Determinants of increased anti-insulin antibody production in some patients remain elusive but impact on blood glucose control is limited in most cases.

CONCLUSION

From analyzed data, the EVADIAC group states that implantable pumps can be safely indicated and provide metabolic improvements in type 1 diabetic patients who remain far from targeted HbA(1c) below 7% and/or experience large fluctuations of blood glucose including recurrent severe hypoglycaemia, in spite of intensive follow-up and education when treated by subcutaneous insulin.

Activation of human macrophages by allogeneic islets preparations: inhibition by AOP-RANTES and heparinoids

During transplantation, pancreatic islets release chemokines which promote macrophage attraction, hampering engraftment of islets. The aim of this study was to modulate chemotaxis and the immune response of human macrophages induced by islets. Human monocyte-derived macrophages of healthy subjects were exposed to supernatants of human islets. Chemotaxis, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) release were evaluated. To modulate migration, human macrophages were incubated in the presence of aminooxypentane-regulated on activation, normal, T-cell expressed, and secreted (AOP-RANTES), a potent antagonist of CCR5. Chemotactic activity of islets supernatant was modulated by the addition of heparin or heparinoids [pentosan and calix[8S]arene (C8S)]. AOP-RANTES significantly reduced, in a dose-dependent manner, macrophage chemotaxis and cytokine release induced by islets supernatant. The chemotactic index was reduced from 3.05 +/- 0.27 to 0.71 +/- 12, TNF-alpha from 1205 +/- 52 to 202 +/- 12 pg/ml, and IL-1beta from 234 +/- 12 to 10 +/- 6 pg/ml. The trapping of chemokines by heparinoids reduced the chemotactic activity of islets supernatant from 3.05 +/- 0.27 to 1.2 +/- 0.1 with heparin or pentosan and to 1.72 +/- 0.22 with C8S, and also decreased the TNF-alpha release by human macrophages from 1205 +/- 35 to 1000 +/- 26 (C8S), 250 +/- 21 (heparin) and 320 +/- 19 (pentosan) pg/ml, and IL-1beta from 234 +/- 13 to 151 +/- 5 (C8S), 50 +/- 3 (heparin) and 57 +/- 4 (pentosan) pg/ml. In conclusion, AOP-RANTES and heparinoids inhibit human macrophage activation and migration induced by islets supernatant.

Reduction of blood glucose variability in type 1 diabetic patients treated by pancreatic islet transplantation: interest of continuous glucose monitoring

OBJECTIVE

To compare the glycemic profiles of patients with type 1 diabetes treated with either an implantable insulin pump or pancreas or islet transplantation by the means of the continuous glucose monitoring system (CGMS; Minimed, Sylmar, CA).

RESEARCH DESIGN AND METHODS

The CGMS enabled recording of subcutaneous glucose concentrations (range 2.2-22 mmol/l) over 72 h (288 measurements per day). Over 3 days, 26 patients with type 1 diabetes were connected to a CGMS: 10 patients were treated with intraperitoneal insulin infusion through an implantable pump (IPII), 9 patients were treated with simultaneous pancreas-kidney transplantation (SPK), and 7 patients were treated with pancreatic islet transplantation after kidney grafting (IAK). All SPK patients and four IAK patients were insulin independent, whereas three IAK patients had partial graft function and reduced exogenous insulin needs. Glucose control was evaluated by the mean glucose concentration, glucose variability, and the number and duration of hypoglycemic events (<3.3 mmol/l) over 3 days.

RESULTS

The mean glucose concentration and the glucose variability in SPK and IAK patients were significantly lower than those observed in patients treated with IPII: 5.38 +/- 1.12 and 5.83 +/- 0.81 vs. 7.81 +/- 1.55 mmol/l (P < 0.001) and 1.40 +/- 0.42 and 1.32 +/- 0.53 vs. 3.47 +/- 1.66 mmol/l (P < 0.001), respectively. Furthermore, the mean glucose concentration and the glucose variability were comparable between SPK and IAK patients. Over 3 days, no hypoglycemic events were observed in SPK patients and insulin-independent IAK patients. A total of 4.12 +/- 1.66 hypoglycemic events were detected in the IPII patient group, whereas only 0.66 +/- 0.57 events were observed in IAK patients with partial graft function (P < 0.001). The duration of the hypoglycemic events was significantly longer in IPII patients as compared with IAK patients: 64 +/- 33 vs. 30 +/- 15 min for the day period and 130 +/- 62 vs. 30 +/- 27 min for the night period (P < 0.001).

CONCLUSIONS

Use of subcutaneous CGMS confirms that islet transplantation can be as efficient as pancreas transplantation in restoring good metabolic control and reducing blood glucose variability. Metabolic improvement due to use of an implantable insulin pump requires insulin delivery by a closed loop.