Intrahepatic glucose flux as a mechanism for defective intrahepatic islet alpha-cell response to hypoglycemia

Quality of life and metabolic outcomes after total pancreatectomy and simultaneous islet autotransplantation

Background

Pancreas surgery remains technically challenging and is associated with considerable morbidity and mortality. Identification of predictive risk factors for complications have led to a stratified surgical approach and postoperative management. The option of simultaneous islet autotransplantation (sIAT) allows for significant attenuation of long-term metabolic and overall complications and improvement of quality of life (QoL). The potential of sIAT to stratify a priori the indication for total pancreatectomy is yet not adequately evaluated.

Methods

The aim of this analysis was to evaluate the potential of sIAT in patients undergoing total pancreatectomy to improve QoL, functional and overall outcome and therefore modify the surgical strategy towards earlier and extended indications. A center cohort of 24 patients undergoing pancreatectomy were simultaneously treated with IAT. Patients were retrospectively analyzed regarding in-hospital and overall mortality, postoperative complications, ICU stay, hospital stay, metabolic outcome, and QoL.

Results

Here we present that all patients undergoing primary total pancreatectomy or surviving complicated two-stage pancreas resection and receiving sIAT show excellent metabolic outcome (33% insulin independence, 66% partial graft function; HbA1c 6,1 ± 1,0%) and significant benefit regarding QoL. Primary total pancreatectomy leads to significantly improved overall outcome and a significant reduction in ICU- and hospital stay compared to a two-stage completion pancreatectomy approach.

Conclusions

The findings emphasize the importance of risk-stratified pancreas surgery. Feasibility of sIAT should govern the indication for primary total pancreatectomy particularly in high-risk patients. In rescue completion pancreatectomy sIAT should be performed whenever possible due to tremendous metabolic benefit and associated QoL.

Intracranial Transplantation of Pancreatic Islets Attenuates Cognitive and Peripheral Metabolic Dysfunctions in a Rat Model of Sporadic Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is often associated with brain insulin resistance and peripheral metabolic dysfunctions. Recently, we developed a model of sporadic AD associated with obesity-related peripheral metabolic abnormalities in Lewis rats using intracerebroventricular administration of streptozotocin (icv-STZ).

OBJECTIVE

We aimed to assess the effect of intracranially grafted pancreatic islets on cognitive and peripheral metabolic dysfunctions in the icv-STZ Lewis rats.

METHODS

AD-like dementia associated with obesity was induced in inbred Lewis rats using a single icv-STZ. Two months after icv-STZ, syngeneic islets (100 islets per recipient) were implanted in the cranial subarachnoid cavity of icv-STZ rats. Morris water maze and marble burying tests were used for studying cognitive and behavioral functions. Central and peripheral metabolic alterations were assessed by histological and biochemical assays.

RESULTS

The icv-STZ induced increases in food intake, body weight, and blood levels of insulin and leptin without alteration of glucose homeostasis. Grafted islets reduced body weight gain, food consumption, peripheral insulin resistance, and hyperleptinemia. Biochemical and histological analysis of the brain revealed viable grafted islets expressing insulin and glucagon. The grafted islets did not affect expression of brain insulin receptors and peripheral glucose homeostasis. Two months after islet transplantation, cognitive and behavioral functioning in transplanted rats were significantly better than the sham-operated icv-STZ rats. No significant differences in the locomotor activity between transplanted and non-transplanted icv-STZ rats were found.

CONCLUSIONS

Intracranial islet transplantation attenuates cognitive decline and peripheral metabolic dysfunctions providing a novel therapeutic approach for sporadic AD associated with peripheral metabolic dysfunctions.

Unsurpassed Intrahepatic Islet Engraftment - the Quest for New Sites for Beta Cell Replacement

The liver is currently the site of choice for clinical islet transplantation, even though many alternative implantation sites have lately been proposed as more ideal for graft survival. The suggested sites, for example intramuscular space, omentum, bone marrow, and spleen, are sometimes difficult to compare due to differences in animal model, islet isolation procedure, and islet quality. In addition, the variation in transplanted islet mass is vast. The aim of this commentary is to review alternative implantation sites tested experimentally as well as in clinical islet transplantation. Although many sites have been investigated, none have convincingly proved better suited for clinical islet transplantation than intraportal injection to the liver, regardless of whether it is autologous or allogeneic transplantation. However, in order to fully evaluate upcoming bioengineering techniques, such as scaffolds containing insulin-producing cells derived from stem cells, the need of an alternative site has arisen to enable cellular monitoring, which currently cannot be achieved within the liver.

Pancreatic Islet Transplantation in Humans: Recent Progress and Future Directions

Pancreatic islet transplantation has become an established approach to β-cell replacement therapy for the treatment of insulin-deficient diabetes. Recent progress in techniques for islet isolation, islet culture, and peritransplant management of the islet transplant recipient has resulted in substantial improvements in metabolic and safety outcomes for patients. For patients requiring total or subtotal pancreatectomy for benign disease of the pancreas, isolation of islets from the diseased pancreas with intrahepatic transplantation of autologous islets can prevent or ameliorate postsurgical diabetes, and for patients previously experiencing painful recurrent acute or chronic pancreatitis, quality of life is substantially improved. For patients with type 1 diabetes or insulin-deficient forms of pancreatogenic (type 3c) diabetes, isolation of islets from a deceased donor pancreas with intrahepatic transplantation of allogeneic islets can ameliorate problematic hypoglycemia, stabilize glycemic lability, and maintain on-target glycemic control, consequently with improved quality of life, and often without the requirement for insulin therapy. Because the metabolic benefits are dependent on the numbers of islets transplanted that survive engraftment, recipients of autoislets are limited to receive the number of islets isolated from their own pancreas, whereas recipients of alloislets may receive islets isolated from more than one donor pancreas. The development of alternative sources of islet cells for transplantation, whether from autologous, allogeneic, or xenogeneic tissues, is an active area of investigation that promises to expand access and indications for islet transplantation in the future treatment of diabetes.

Local, Controlled Release In Vivo of Vascular Endothelial Growth Factor Within a Subcutaneous Scaffolded Islet Implant Reduces Early Islet Necrosis and Improves Performance of the Graft

Islet transplantation remains the only alternative to daily insulin therapy for control of type 1 diabetes (T1D) in humans. To avoid the drawbacks of intrahepatic islet transplantation, we are developing a scaffolded islet implant to transplant islets into nonhepatic sites. The implant test bed, sized for mice, consists of a limited (2-mm) thickness, large-pore polymeric sponge scaffold perforated with peripheral cavities that contain islets suspended in a collagen hydrogel. A central cavity in the scaffold holds a 2-mm diameter alginate sphere for controlled release of the angiogenic cytokine vascular endothelial growth factor ( VEGF). Host microvessels readily penetrate the scaffold and collagen gel to vascularize the islets. Here, we evaluate the performance of the implant in a subcutaneous (SC) graft site. Implants incorporating 500 syngeneic islets reversed streptozotocin-induced diabetes in mice approximately 30 d after SC placement. Controlled release of a modest quantity (20 ng) of VEGF within the implant significantly reduced the time to normoglycemia compared to control implants lacking VEGF. Investigation of underlying causes for this effect revealed that inclusion of 20 ng of VEGF in the implants significantly reduced central necrosis of islets 24 h after grafting and increased implant vascularization (measured 12 d after grafting). Collectively, our results demonstrate (1) that the scaffolded islet implant design can reverse diabetes in SC sites in the absence of prevascularization of the graft site and (2) that relatively low quantities of VEGF, delivered by controlled release within the implant, can be a useful approach to limit islet stress after grafting.

Deficient Glucagon Response to Hypoglycemia During a Mixed Meal in Total Pancreatectomy/Islet Autotransplantation Recipients

CONTEXT

Total pancreatectomy and intrahepatic islet autotransplantation (TP/IAT) is performed to alleviate severe abdominal pain, avoid narcotic use, maintain islet function, and avoid diabetes in patients with chronic pancreatitis. However, many TP/IAT recipients complain of postprandial hypoglycemia.

OBJECTIVE

This study was designed to discover the mechanisms of this problem.

DESIGN

Participants consumed a triple-isotope mixed meal.

SETTING

This study was performed in a hospital research unit.

PARTICIPANTS

We studied 10 TP/IAT recipients and 10 age- and body mass index-matched control subjects. Seven of 10 recipients had a history of postprandial hypoglycemia.

INTERVENTIONS

Participants were given a [1-13C]-labeled mixed meal and two tracer infusions ([6,6-2H2]- and [6-3H]-glucose).

MAIN OUTCOME MEASURES

Glucose kinetics and concentrations of regulatory hormones were determined.

RESULTS

Immediately after the meal, peak glucose was elevated in recipients compared with control subjects [266 ± 20 mg/dL (14.8 ± 1.1 mmol/L) vs 185 ± 13 mg/dL (10.3 ± 0.7 mmol/L); P = 0.01]. However, mean Δ glucose for TP/IAT recipients between minutes 240 and 360 postprandially was significantly lower than for control subjects (P < 0.05); six of the seven recipients with a history of hypoglycemia experienced abnormally low postprandial Δ glucose. Δ Glucagon remained unchanged (minutes 240 to 360; P = 0.58) in TP/IAT recipients despite abnormal decreases in postprandial glucose. Radioisotopic studies revealed that meal appearance, glucose disappearance, and endogenous glucose production in TP/IAT recipients were not different from control subjects.

CONCLUSION

Initially high glucose levels followed by hypoglycemia with an absent glucagon response is a mechanistic sequence that contributes to postprandial hypoglycemia after TP/IAT.

Long-Term Improvement in Glucose Control and Counterregulation by Islet Transplantation for Type 1 Diabetes

CONTEXT

Islet transplantation has been shown to improve glucose counterregulation and hypoglycemia symptom recognition in patients with type 1 diabetes (T1D) complicated by severe hypoglycemia episodes and symptom unawareness, but long-term data are lacking.

OBJECTIVE

To assess the long-term durability of glucose counterregulation and hypoglycemia symptom responses 18 months after intrahepatic islet transplantation and associated measures of glycemic control during a 24-month follow-up period.

DESIGN, SETTING, AND PARTICIPANTS

Ten patients with T1D disease duration of approximately 27 years were studied longitudinally before and 6 and 18 months after transplant in the Clinical & Translational Research Center of the University of Pennsylvania and were compared to 10 nondiabetic control subjects.

INTERVENTION

All 10 patients underwent intrahepatic islet transplantation according to the CIT07 protocol at the Hospital of the University of Pennsylvania.

MAIN OUTCOME MEASURES

Counterregulatory hormone, endogenous glucose production, and autonomic symptom responses derived from stepped hyperinsulinemic-hypoglycemic and paired hyperinsulinemic-euglycemic clamps with infusion of 6,6-²H₂-glucose.

RESULTS

Near-normal glycemia (HbA_1c ≤ 6.5%; time 70-180 mg/dL ≥ 95%) was maintained for 24 months in all patients, with one returning to low-dose insulin therapy. In response to insulin-induced hypoglycemia, glucagon secretion was incompletely restored at 6 and 18 months, epinephrine was improved at 6 months and normalized at 18 months, and endogenous glucose production and symptoms, absent before, were normalized at 6 and 18 months after transplant.

CONCLUSIONS

In patients with T1D experiencing problematic hypoglycemia, intrahepatic islet transplantation can lead to long-term improvement of glucose counterregulation and hypoglycemia symptom recognition, physiological effects that likely contribute to glycemic stability after transplant.

Spontaneous Hypoglycemia After Islet Transplantation: The Case For Using Non-Hepatic Sites

This Perspective provides a brief history of intrahepatic alloislet and autoislet transplantation in humans and an update of the recent success rates. It also examines the important role that hypoglycemia plays in clinical outcomes. On the one hand, recurrent serious hypoglycemic episodes related to insulin therapy are a major criterion for alloislet transplantation. On the other hand, spontaneous clinical hypoglycemia, perhaps related to the accompanying Roux-en-Y procedure for total pancreatectomy, is a complication of autoislet transplantation. Complex alterations in glucagon secretion compromise counter-regulation of hypoglycemia in both situations. The glucagon response to hypoglycemia is intrinsically defective in type 1 diabetes before transplant because of the absence of physiological regulation of α-cell secretion by neighboring β-cells. Glucagon secretion from intrahepatic islets during systemic hypoglycemia is also defective, although β-cells in the graft are normally regulated by glucose and arginine. My personal perspective is that the latter is caused by intrahepatic glycogenolysis stimulated by systemic hypoglycemia with consequent increases in intrahepatic glucose flux, which incorrectly signals intrahepatic α-cells to be quiescent. This defect is liver-specific, which strongly suggests modifying the current approach to islet transplantation by placing a portion of allo- and autoislets in nonhepatic sites in addition to hepatic sites to ensure physiological glucagon secretion as a strategy to ameliorate post-transplant hypoglycemia.

Spontaneous Hypoglycemia After Islet Autotransplantation for Chronic Pancreatitis

CONTEXT

Spontaneous hypoglycemia has been reported in patients after total pancreatectomy (TP) and islet autotransplantation (IAT) with maintained insulin independence. Details surrounding these events have not been well described.

OBJECTIVE

The objective of the study was to determine the frequency and characteristics of spontaneous hypoglycemia in patients undergoing TP-IAT and/or to ascertain predictive or protective factors of its development.

DESIGN

This was an observational cohort study in 40 patients who underwent TP-IAT from August 2008 to May 2014, with a median follow-up of 34 months.

SETTING

The study was conducted at a single institution (Cleveland Clinic).

PATIENTS

Patients included recipients of TP-IAT.

INTERVENTION

The intervention included small, frequent meals in those patients who developed spontaneous hypoglycemia.

MAIN OUTCOME MEASURES

Incidence of spontaneous hypoglycemia development, characteristics of the patients developing hypoglycemia, and their response to small, frequent meals were measured.

RESULTS

Six of 12 patients, who maintained insulin independence, developed spontaneous hypoglycemia. The episodes could be fasting, postprandial, and/or exercise associated, with the frequency ranging from two to three times daily to once every 1-2 weeks. All patients experienced at least one episode that required external assistance, glucagon administration, and/or emergent medical attention. Patients who developed hypoglycemia had a lower median age and tended to have a lower median islet equivalent/kg body weight but a higher median total islet equivalent, body mass index, and homeostatic model assessment for insulin resistance score. All patients who received small, frequent meal intervention had improvement in severity and/or frequency of the hypoglycemic episodes.

CONCLUSIONS

Spontaneous hypoglycemia is prevalent after TP-IAT. Although the underlying pathophysiology responsible for these hypoglycemia events remains to be elucidated, small, frequent meal intervention is helpful in ameliorating this condition.

Rapid adaptation of rat brain and liver metabolism to a ketogenic diet: an integrated study using (1)H- and (13)C-NMR spectroscopy

The ketogenic diet (KD) is an effective alternative treatment for refractory epilepsy in children, but the mechanisms by which it reduces seizures are poorly understood. To investigate how the KD modifies brain metabolism, we infused control (CT) and 7-day KD rats with either [1-(13)C]glucose (Glc) or [2,4-(13)C2]β-hydroxybutyrate (β-HB). Specific enrichments of amino acids (AAs) measured by (1)H- and (13)C-NMR in total brain perchloric acid extracts were similar between CT and KD rats after [1-(13)C]Glc infusion whereas they were higher in KD rats after [2,4-(13)C2]β-HB infusion. This suggests better metabolic efficiency of ketone body utilization on the KD. The relative rapid metabolic adaptation to the KD included (1) 11%-higher brain γ-amino butyric acid (GABA)/glutamate (Glu) ratio versus CT, (2) liver accumulation of the ketogenic branched-chain AAs (BCAAs) leucine (Leu) and isoleucine (ILeu), which were never detected in CT, and (3) higher brain Leu and ILeu contents. Since Glu and GABA are excitatory and inhibitory neurotransmitters, respectively, higher brain GABA/Glu ratio could contribute to the mechanism by which the KD reduces seizures in epilepsy. Increased BCAA on the KD may also contribute to better seizure control.

Islet transplantation for type 1 diabetes, 2015: what have we learned from alloislet and autoislet successes?

The therapeutic potential of pancreatic islet allotransplantation, in which human donor islets are used, as a treatment for type 1 diabetes (T1D) has fascinated diabetes researchers and clinicians for decades. At the same time, the therapeutic potential of total pancreatectomy and islet autotransplantation (TPIAT) (in which one's own islets are used) as a preventive treatment for diabetes in patients who undergo total pancreatectomy for chronic, painful pancreatitis has received relatively less attention. This is ironic, since the latter has been much more effective than the former in terms of successful glucose management and duration of efficacy. The reasons for this disparity can be partially identified. TPIAT receives very little attention in textbooks of internal medicine and general surgery and surprisingly little print in textbooks of endocrinology and transplantation. T1D is much more predominant than TPIAT as a clinical entity. Provision of insulin or replacement of islets is mandatory and a primary goal in T1D. Provision of pain relief from chronic pancreatitis is the primary goal of total pancreatectomy in TPIAT, whereas treatment of diabetes, and certainly prevention of diabetes, has been more of a secondary consideration. Nonetheless, research developments in both fields have contributed to success in one another. In this Perspective, I will provide a brief history of islet transplantation and contrast and compare the procedures of allo- and autoislet transplantation from three major points of view 1) the procedures of islet procurement, isolation, and transplantation; 2) the role and complications of immunosuppressive drugs; and 3) the posttransplant consequences on β- as well as α-cell function.

Restoration of Glucose Counterregulation by Islet Transplantation in Long-standing Type 1 Diabetes

Patients with long-standing type 1 diabetes (T1D) may exhibit defective glucose counterregulation and impaired hypoglycemia symptom recognition that substantially increase their risk for experiencing severe hypoglycemia. The purpose of this study was to determine whether intrahepatic islet transplantation improves endogenous glucose production (EGP) in response to hypoglycemia in T1D patients experiencing severe hypoglycemia. We studied longitudinally subjects (n = 12) with ∼30 years, disease duration before and 6 months after intrahepatic islet transplantation using stepped hyperinsulinemic-hypoglycemic and paired hyperinsulinemic-euglycemic clamps with infusion of 6,6-(2)H2-glucose and compared the results with those from a nondiabetic control group (n = 8). After islet transplantation, HbA1c was normalized, and time spent while hypoglycemic (<70 mg/dL) was nearly abolished as indicated by continuous glucose monitoring. In response to insulin-induced hypoglycemia, C-peptide (absent before transplant) was appropriately suppressed, glucagon secretion was recovered, and epinephrine secretion was improved after transplantation. Corresponding to these hormonal changes, the EGP response to insulin-induced hypoglycemia, which was previously absent, was normalized after transplantation, with a similar effect seen for autonomic symptoms. Because the ability to increase EGP is ultimately required to circumvent the development of hypoglycemia, these results provide evidence that intrahepatic islet transplantation can restore glucose counterregulation in long-standing T1D and support its consideration as treatment for patients with hypoglycemia unawareness experiencing severe hypoglycemia.

Total pancreatectomy with islet autotransplantation: summary of an NIDDK workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis. The session was held on July 23, 2014 and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, GI complications in this population, and unique features of children with chronic pancreatitis considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of chronic pancreatitis and total pancreatectomy outcomes and postsurgical diabetes outcomes was repeatedly emphasized.

Assessment of β-cell mass and α- and β-cell survival and function by arginine stimulation in human autologous islet recipients

We used intravenous arginine with measurements of insulin, C-peptide, and glucagon to examine β-cell and α-cell survival and function in a group of 10 chronic pancreatitis recipients 1-8 years after total pancreatectomy and autoislet transplantation. Insulin and C-peptide responses correlated robustly with the number of islets transplanted (correlation coefficients range 0.81-0.91; P < 0.01-0.001). Since a wide range of islets were transplanted, we normalized the insulin and C-peptide responses to the number of islets transplanted in each recipient for comparison with responses in normal subjects. No significant differences were observed in terms of magnitude and timing of hormone release in the two groups. Three recipients had a portion of the autoislets placed within their peritoneal cavities, which appeared to be functioning normally up to 7 years posttransplant. Glucagon responses to arginine were normally timed and normally suppressed by intravenous glucose infusion. These findings indicate that arginine stimulation testing may be a means of assessing the numbers of native islets available in autologous islet transplant candidates and is a means of following posttransplant α- and β-cell function and survival.

Total pancreatectomy with islet autotransplantation: summary of a National Institute of Diabetes and Digestive and Kidney diseases workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis (CP). The session was held on July 23, 2014, and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, gastrointestinal complications in this population, and unique features of children with CP considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of CP and total pancreatectomy outcomes as well as postsurgical diabetes outcomes was repeatedly emphasized.

Total pancreatectomy with islet autotransplantation: summary of a National Institute of Diabetes and Digestive and Kidney diseases workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis (CP). The session was held on July 23, 2014, and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, gastrointestinal complications in this population, and unique features of children with CP considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of CP and total pancreatectomy outcomes as well as postsurgical diabetes outcomes was repeatedly emphasized.

Defective glucagon secretion during hypoglycemia after intrahepatic but not nonhepatic islet autotransplantation

Defective glucagon secretion during hypoglycemia after islet transplantation has been reported in animals and humans with type 1 diabetes. To ascertain whether this is true of islets from nondiabetic humans, subjects with autoislet transplantation in the intrahepatic site only (TP/IAT-H) or in intrahepatic plus nonhepatic (TP/IAT-H+NH) sites were studied. Glucagon responses were examined during stepped hypoglycemic clamps. Glucagon and symptom responses during hypoglycemia were virtually absent in subjects who received islets in the hepatic site only (glucagon increment over baseline = 1 ± 6, pg/mL, mean ± SE, n = 9, p = ns; symptom score = 1 ± 1, p = ns). When islets were transplanted in both intrahepatic + nonhepatic sites, glucagon and symptom responses were not significantly different than Control Subjects (TP/IAT-H + NH: glucagon increment = 54 ± 14, n = 5; symptom score = 7 ± 3; control glucagon increment = 67 ± 15, n = 5; symptom score = 8 ± 1). In contrast, glucagon responses to intravenous arginine were present in TP/IAT-H recipients (TP/IAT: glucagon response = 37 ± 8, n = 7). Transplantation of a portion of the islets into a nonhepatic site should be seriously considered in TP/IAT to avoid posttransplant abnormalities in glucagon and symptom responses to hypoglycemia.

Magnitude and mechanisms of glucose counterregulation following islet transplantation in patients with type 1 diabetes suffering from severe hypoglycaemic episodes

AIMS/HYPOTHESIS

Pancreatic islet transplantation stabilises glycaemic control in type 1 diabetes mellitus patients with neuroglycopoenia, despite them not achieving insulin independence because of limited graft function. However, the extent and underlying metabolic pathways of restored glucose counterregulation are unknown. We therefore compared systemic glucose turnover, including lactate gluconeogenesis (GN) and muscle glucose uptake, in individuals with type 1 diabetes who were transplant recipients with partial graft function (T1DM/ITx(+)), matched non-transplanted individuals with type 1 diabetes (T1DM/ITx(-)) and matched healthy non-diabetic individuals.

METHODS

Participants (n = 12 in each group) underwent a euglycaemic and a hypoglycaemic (2.5-2.8 mmol/l) hyperinsulinaemic clamp (0.8 mU kg(-1) min(-1)) in a randomised crossover fashion. Systemic and skeletal muscle glucose and lactate kinetics were assessed using a combination of isotopic and forearm balance techniques.

RESULTS

Whole-body glucose counterregulation, the difference in glucose infusion rates required to maintain the glycaemic goal between the hypoglycaemic and euglycaemic clamps, was improved in T1DM/ITx(+) (7.8 ± 1.3 μmol kg(-1) min(-1)) compared with T1DM/ITx(-) (0.3 ± 0.9 μmol kg(-1) min(-1)), but was ~45% lower than in controls (14.1 ± 2.1 μmol kg(-1) min(-1)). Increased endogenous glucose production (EGP) and decreased systemic glucose disposal accounted for 49% and 39% of glucose counterregulation in T1DM/ITx(+), respectively, compared with 60% and 36% in controls. Lactate GN increased in T1DM/ITx(+) (2.7 ± 0.4 μmol kg(-1) min(-1)) and controls (1.7 ± 0.5 μmol kg(-1) min(-1)), such that it accounted for 70% and 20% of the increased EGP, respectively. Skeletal muscle accounted for similar proportions of the decrease in systemic glucose disposal in controls (49%) and T1DM/ITx(+) (41%).

CONCLUSIONS/INTERPRETATION

Partial islet graft function improves hypoglycaemia counterregulation by increasing EGP, largely via lactate GN and decreasing systemic glucose disposal. This may explain the reduction in severe hypoglycaemic events in T1DM/ITx(+) individuals.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01668485.

Chronic AMPK activity dysregulation produces myocardial insulin resistance in the human Arg302Gln-PRKAG2 glycogen storage disease mouse model

Background

The cardiac PRKAG2 mutation in the γ2-subunit of adenosine monophosphate activated kinase (AMPK) is characterized by excessive glycogen deposition, hypertrophy, frequent arrhythmias, and progressive conduction system disease. We investigated whether myocardial glucose uptake (MGU) was augmented following insulin stimulation in a mouse model of the PRKAG2 cardiac syndrome.

Methods

Myocardial and skeletal muscle glucose uptake was assessed with 2-[¹⁸F]fluoro-2-deoxyglucose positron emission tomography imaging in n = 3 transgenic wildtype (TGwt) vs n = 7 PRKAG2 mutant (TGmut) mice at baseline and 1 week later, 30 min following acute insulin. Systolic function, cardiac glycogen stores, phospho-AMPK α, and insulin-receptor expression levels were analyzed to corroborate to the in vivo findings.

Results

TGmut Patlak Ki was reduced 56% at baseline compared to TGwt (0.3 ± 0.2 vs 0.7 ± 0.1, t test p = 0.01). MGU was augmented 71% in TGwt mice following acute insulin from baseline (0.7 ± 0.1 to 1.2 ± 0.2, t test p < 0.05). No change was observed in TGmut mice. As expected for this cardiac specific transgene, skeletal muscle was unaffected at baseline with a 33% to 38% increase (standard uptake values) for both genotypes following insulin stimulation. TGmut mice had a 47% reduction in systolic function with a fourfold increase in cardiac glycogen stores correlated with a 29% reduction in phospho-AMPK α levels. There was no difference in cardiac insulin receptor expression between mouse genotypes.

Conclusions

These results demonstrate a correlation between insulin resistance and AMPK activity and provide the basis for the use of this animal model for assessing metabolic therapy in the treatment of affected PRKAG2 patients.

No islets left behind: islet autotransplantation for surgery-induced diabetes

For patients with severe chronic pancreatitis refractory to medical interventions, total pancreatectomy can be considered to relieve the root cause of pain. The goal of a simultaneous islet autotransplant is to prevent or minimize the otherwise inevitable surgical diabetes. Islet autotransplant can successfully preserve some endogenous islet function in the majority of recipients, which mediates protection against brittle diabetes. Most maintain reasonably good glycemic control, while 30 %-40 % successfully discontinue insulin therapy. With islet autotransplants reaching a wider clinical audience, refinements in islet isolation techniques and strategies to protect islet grafts post-transplant may further improve the success of this procedure.

Glucagon secretion and signaling in the development of diabetes

Normal release of glucagon from pancreatic islet α-cells promotes glucose mobilization, which counteracts the hypoglycemic actions of insulin, thereby ensuring glucose homeostasis. In treatment of diabetes aimed at rigorously reducing hyperglycemia to avoid chronic complications, the resulting hypoglycemia triggering glucagon release from α-cells is frequently impaired, with ensuing hypoglycemic complications. This review integrates the physiology of glucagon secretion regulating glucose homeostasis in vivo to single α-cell signaling, and how both become perturbed in diabetes. α-cells within the social milieu of the islet micro-organ are regulated not only by intrinsic signaling events but also by paracrine regulation, particularly by adjacent insulin-secreting β-cells and somatostatin-secreting δ-cells. We discuss the intrinsic α-cell signaling events, including glucose sensing and ion channel regulation leading to glucagon secretion. We then discuss the complex crosstalk between the islet cells and the breakdown of this crosstalk in diabetes contributing to the dysregulated glucagon secretion. Whereas, there are many secretory products released by β- and δ-cells that become deficient or excess in diabetes, we discuss the major ones, including the better known insulin and lesser known somatostatin, which act as putative paracrine on/off switches that very finely regulate α-cell secretory responses in health and diabetes. Of note in several type 1 diabetes (T1D) rodent models, blockade of excess somatostatin actions on α-cell could normalize glucagon secretion sufficient to attain normoglycemia in response to hypoglycemic assaults. There has been slow progress in fully elucidating the pathophysiology of the α-cell in diabetes because of the small number of α-cells within an islet and the islet mass becomes severely reduced and inflamed in diabetes. These limitations are just now being surmounted by new approaches.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.

Pancreatectomy and autologous islet transplantation for painful chronic pancreatitis: indications and outcomes

Total pancreatectomy with intrahepatic autoislet transplantation (TP/IAT) is a definitive treatment for relentlessly painful chronic pancreatitis. Pain relief is reported to be achieved in approximately 80% of patients. Overall, 30% to 40% achieve insulin independence, and 70% of recipients remain insulin independent for > 2 years, sometimes longer if > 300 000 islets are successfully transplanted. Yet, this approach to chronic pancreatitis is underemphasized in the general medical and surgical literature and vastly underused in the United States. This review emphasizes the history and metabolic outcomes of TP/IAT and considers its usefulness in the context of other, more frequently used approaches, such as operative intervention with partial pancreatectomy and/or lateral pancreaticojejunostomy (Puestow procedure), as well as endoscopic retrograde cholangiopancreatography with pancreatic duct modification and stent placement. Distal pancreatectomy and Puestow procedures compromise isolation of islet mass, and adversely affect islet autotransplant outcomes. Therefore, when endoscopic measures fail to relieve pain in severe chronic pancreatitis, we recommend early intervention with TP/IAT.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

Influence of microenvironment on engraftment of transplanted β-cells

Pancreatic islet transplantation into the liver provides a possibility to treat selected patients with brittle type 1 diabetes mellitus. However, massive early β-cell death increases the number of islets needed to restore glucose homeostasis. Moreover, late dysfunction and death contribute to the poor long-term results of islet transplantation on insulin independence. Studies in recent years have identified early and late challenges for transplanted pancreatic islets, including an instant blood-mediated inflammatory reaction when exposing human islets to the blood microenvironment in the portal vein and the low oxygenated milieu of islets transplanted into the liver. Poor revascularization of remaining intact islets combined with severe changes in the gene expression of islets transplanted into the liver contributes to late dysfunction. Strategies to overcome these hurdles have been developed, and some of these interventions are now even tested in clinical trials providing a hope to improve results in clinical islet transplantation. In parallel, experimental and clinical studies have, based on the identified problems with the liver site, evaluated the possibility of change of implantation organ in order to improve the results. Site-specific differences clearly exist in the engraftment of transplanted islets, and a more thorough characterization of alternative locations is needed. New strategies with modifications of islet microenvironment with cells and growth factors adhered to the islet surface or in a surrounding matrix could be designed to intervene with site-specific hurdles and provide possibilities to improve future results of islet transplantation.

Induction of chimerism permits low-dose islet grafts in the liver or pancreas to reverse refractory autoimmune diabetes

OBJECTIVE

To test whether induction of chimerism lowers the amount of donor islets required for reversal of diabetes and renders the pancreas a suitable site for islet grafts in autoimmune diabetic mice.

RESEARCH DESIGN AND METHODS

The required donor islet dose for reversal of diabetes in late-stage diabetic NOD mice after transplantation into the liver or pancreas was compared under immunosuppression or after induction of chimerism. Recipient mice were monitored for blood glucose levels and measured for insulin-secretion capacity. Islet grafts were evaluated for beta-cell proliferation, beta-cell functional gene expression, and revascularization.

RESULTS

With immunosuppression, transplantation of 1,000, but not 600, donor islets was able to reverse diabetes when transplanted into the liver, but transplantation of 1,000 islets was not able to reverse diabetes when transplanted into the pancreas. In contrast, after induction of chimerism, transplantation of as few as 100 donor islets was able to reverse diabetes when transplanted into either the liver or pancreas. Interestingly, when lower doses (50 or 25) of islets were transplanted, donor islets in the pancreas were much more effective in reversal of diabetes than in the liver, which was associated with higher beta-cell replication rate, better beta-cell functional gene expression, and higher vascular density of graft islets in the pancreas.

CONCLUSIONS

Induction of chimerism not only provides immune tolerance to donor islets, but also markedly reduces the required amount of donor islets for reversal of diabetes. In addition, this process renders the pancreas a more superior site than the liver for donor islets in autoimmune mice.

Update on transplanting beta cells for reversing type 1 diabetes

Whole pancreas has been used successfully for transplantation for more than 30 years, and islets have been used reproducibly with success for 10 years; both procedures require drugs for immunosuppression. Success is judged by discontinuation of exogenous insulin-based treatment and maintenance of normal or nearly normal hemoglobin A1c. Successful pancreas transplantation has beneficial effects on retinopathy, nephropathy, neuropathy, macrovascular disease, and quality of life. Such findings are suggested for islet transplantation, but insufficient information is available to draw firm conclusions. Because of the paucity of annual pancreas donations, research for human beta cell surrogates is essential to provide a transplantation approach to therapy for a greater number of recipients.

Islet transplantation a decade later and strategies for filling a half-full glass

Alloislet transplantation for the treatment of type 1 diabetes enjoyed highly favorable status in the first half of the last decade but declined in favor during the second half. In this Perspective, I will briefly review the literature published in this area from 2000 to 2010 for the purposes of extracting lessons we have learned, considering whether the procedure should be deemed a partial success or a partial failure, and offering several strategies to improve alloislet transplantation outcomes in the future. In the end, I hope to strike a positive note about where this procedure is going, and how it will be applied to establish insulin independence in patients with type 1 diabetes.

Bone marrow as an alternative site for islet transplantation

The liver is the current site for pancreatic islet transplantation, but has many drawbacks due to immunologic and nonimmunologic factors. We asked whether pancreatic islets could be engrafted in the bone marrow (BM), an easily accessible and widely distributed transplant site that may lack the limitations seen in the liver. Syngeneic islets engrafted efficiently in the BM of C57BL/6 mice rendered diabetic by streptozocin treatment. For more than 1 year after transplantation, these animals showed parameters of glucose metabolism that were similar to those of nondiabetic mice. Islets in BM had a higher probability to reach euglycemia than islets in liver (2.4-fold increase, P = .02), showed a compact morphology with a conserved ratio between alpha and beta cells, and affected bone structure only very marginally. Islets in BM did not compromise hematopoietic activity, even when it was strongly induced in response to a BM aplasia-inducing infection with lymphocytic choriomeningitis virus. In conclusion, BM is an attractive and safe alternative site for pancreatic islet transplantation. The results of our study open a research line with potentially significant clinical impact, not only for the treatment of diabetes, but also for other diseases amenable to treatment with cellular transplantation.

Vascular niche of pancreatic islets

Pancreatic islets are highly vascularized micro-organs. Approximately 10% of an islet consists of blood vessels. The induction and maintenance of the islet vascular system depend on VEGF secreted from β-cells. VEGF is also critical for the phenotype of the islet vasculature by induction of a vast number of fenestrae. The islet vasculature serves the role of supplying the endocrine cells with oxygen and nutrients, but may also be important for proper glucose sensing of the cells, for paracrine support of endocrine function and growth, and for drainage of metabolites and secreted islet hormones into the systemic circulation. Emerging evidence suggests an important role of islet endothelial cells to maintain β-cell function and growth by secretion of molecules such as hepatocyte growth factor, thrombospondin-1 and laminins, thereby forming a vascular niche for the endocrine cells.