Bariatric Surgery to Target Obesity in the Renal Transplant Population: Preliminary Experience in a Single Center.

During the last century, obesity has become a global epidemic. The effect of obesity on renal transplantation may occur in perioperative complications and impairment of organ function. Obese patients have metabolic derangements that can be exacerbated after transplantation and obesity directly impacts most transplantation outcomes. These recipients are more likely to develop adverse graft events, such as delayed graft function and early graft loss. Furthermore, obesity is synergic to some immunosuppressive agents in triggering diabetes and hypertension. As behavioral weight loss programs show disappointing results in these patients, bariatric surgery has been considered as a means to achieve rapid and long-term weight loss. Up-to-date literature shows laparoscopic bariatric surgery is feasible and safe in transplantation candidates and increases the rate of transplantation eligibility in obese patients with end-stage organ disease. There is no evidence that restrictive procedures modify the absorption of immunosuppressive medications. From 2013 to 2016 we performed six bariatric procedures (sleeve gastrectomy) on obese patients with renal transplantation; mean preoperative body mass index (BMI) was 39.8 kg/m2. No postoperative complication was observed and no change in the immunosuppressive medications regimen was needed. Mean observed estimated weight loss was 27.6%, 44.1%, 74.2%, and 75.9% at 1, 3, 6, and 12 months follow-up, respectively. Our recommendation is to consider patients with BMI >30 kg/m2 as temporarily ineligible for transplantation and as candidates to bariatric surgery if BMI >35 kg/m2. We consider laparoscopic sleeve gastrectomy as a feasible, first-choice procedure in this specific population.

Pancreas Transplantation From Very Small Pediatric Donor Using the "Cephalic Placement" Technique: A Case Report.

INTRODUCTION: The gap between the number of diabetic patients on the waiting list for transplantation and the number of pancreas donors is growing and it is mandatory to extend criteria for donor eligibility. Several reports showed the feasibility of pancreas transplantation from pediatric donors with comparable outcomes to adult donors in terms of long-term ß-cell function. However, there is no consensus about donor age and weight limits. CASE REPORT: We present two cases of pancreas transplantation alone (PTA) from very small pediatric donors: a 2-year-old female (weight 13 kg, height 88 cm) and a 6-year-old male (weight 29 kg, height 122 cm). We used a novel "cephalic placement" technique. The pancreas was placed upon the aortic carrefour with cephalic pole upward with 3 anchorage points: the left common iliac vein (or the inferior cava vein), the right common iliac artery, and an ileal loop. RESULTS: No postoperative thrombosis occurred and the patients gained insulin independence instantaneously. CT scan performed on postoperative day 3 showed regular organ perfusion in both cases. Graft volume and surface calculated by CT reconstruction were, respectively, 25 cc and 89 cm(2) in the first case, and 46.5 cc and 123 cm(2) in the second case. Postoperative mixed meal tolerance tests showed normal glycemic profile. Patients are actually insulin independent at 4 years and 8 months. CONCLUSIONS: Pancreases from very young pediatric donors are adequate to restore insulin independence after PTA in adult patients. The "cephalic placement" technique is feasible and effective using very small pancreases.

Renal artery stenosis due to fibromuscular dysplasia in a transplanted kidney from a deceased donor: a difficult diagnosis at color Doppler ultrasonography.

Atherosclerotic renal artery stenosis is a frequent cause of arterial hypertension and/or allograft dysfunction after kidney transplantation and is usually located at the iliac artery anastomosis. Fibromuscular dysplasia is a less frequent, nonatherosclerotic, vascular disease, inducing stenosis at the proximal/mid-distal part of the renal artery. We report the case of a 44-year-old woman, in whom serum creatinine concentration increased and arterial hypertension developed 3 months after renal transplantation. Color Doppler ultrasonography showed a low arterial resistance index and prolonged acceleration time in the interlobar arteries, and a significantly increased peak systolic velocity at the mid third of the renal artery, demonstrating hemodynamically significant stenosis. Percutaneous transluminal angioplasty allowed stenosis correction and was followed by creatinine concentration and arterial blood pressure normalization.

Pancreata from pediatric donors restore insulin independence in adult insulin-dependent diabetes mellitus recipients.

CONTEXT: The use of pediatric donors can increase the number of donors available for pancreas transplantation. AIM: The aim of this study was to verify if pancreas transplantation from pediatric donors is as effective as transplantation from adult donors to restore metabolic control in type 1 diabetic patients. MATERIALS AND METHODS: From 2000 to April 2009 we performed 17 pancreas transplantations from pediatric donors: 9 simultaneous kidney-pancreas (SPK), 6 pancreas transplantation alone (PTA), and 2 pancreas after kidney (PAK). All subjects received whole organs with enteric diversion of exocrine secretions; 11 underwent systemic and 6 underwent portal venous graft drainage. The immunosuppressive therapy was as follows: prednisone, mycophenolate mofetil, anti-thymocyte globulin (ATG), and cyclosporine or tacrolimus. The pediatric donor population had a mean age of 15.3 years (range, 12-17), a mean weight of 60.1 kg (range, 42-75), and a mean body mass index (BMI) of 21 (range, 17.9-23.4). RESULTS: After 9 years the overall patient survival rate was 94.12%, whereas the graft survival rate was 63.35%. Normal glucose and insulin levels were maintained either fasting or during oral glucose tolerance test (OGTT). The group of recipients of pediatric organs was compared with patients receiving organs from adult donors (n = 125); the mean glucose values were lower in the pediatric group, whereas insulin production was higher in the adult patients. Early venous thrombosis was 17.6% in the pediatric group and 20% in adult recipients (Fisher exact test, P = not significant [NS]). CONCLUSION: Pediatric donors restored insulin independence in adult diabetic recipients, representing a valid source of organs for pancreas transplantation.

High levels of donor CCL2/MCP-1 predict graft-related complications and poor graft survival after kidney-pancreas transplantation.

In this study we analyzed the role of CCL2, a member of the chemokine family, in early graft damage. Using simultaneous kidney-pancreas transplantation (SPK) as a model, we showed that brain death significantly increases circulating CCL2 levels in humans. We found that in such situations, high donor CCL2 levels (measured before organ recovery and at the onset of cold preservation) correlate with increased postreperfusion release of CCL2 by both the graft and recipient throughout the week following transplantation (n = 28). In a retrospective study of 77 SPK recipients, we found a significant negative association between high donor levels of CCL2 and graft survival. Decreased survival in these patients is related to early posttransplant complications, including a higher incidence of pancreas thrombosis and delayed kidney function. Taken together our data indicate that high CCL2 levels in the donor serum predict both an increase in graft/recipient CCL2 production and poor graft survival. This suggests that the severity of the inflammatory response induced by brain death influences the posttransplant inflammatory response, independent of subsequent ischemia and reperfusion.

Impact of recipient and donor ages on patient and graft survival after kidney transplantation.

BACKGROUND: The purpose of the study was to evaluate the impact of donor and recipient ages on patient and graft survival after kidney transplant. METHODS: Patients in a hospital database undergoing kidney transplant for end-stage renal disease (ESRD) during the period 1985 to May 2006 (n = 410; mean age 42 +/- 10 years; 61% men and 39% women) were divided into two groups: group A, patients of 60 years or older (6%, n = 24), and group B, those younger than 60 years (94, n = 386). In 204 patients (49.8%) the pancreas was transplanted simultaneously with the kidney. RESULTS: Overall 1-, 3-, 5-year patient survivals were 92%, 90%, 88% in group A and 95%, 90%, 87% in group B (P = .6, NS). Overall 1-, 3-, 5-year kidney graft was 92%, 75%, 65% in group A and 92%, 84%, 79% in group B (P = .7, NS). Donors were divided into two groups: group 1, 55 years or older (15%, n = 62), versus group 2, those younger than 55 years (85%, n = 348). Overall 1-, 3-, 5-year patient survivals were 91%, 86%, 76% in group 1 and 97%, 94%, 90% in group 2 (P = .0009). Overall 1-, 3-, 5-year kidney graft survivals were 87%, 82%, 76% in group 1 and 94%, 86%, 82% in group 2 (P = .02). CONCLUSIONS: Renal transplantation is an effective option for the treatment of ESRD in elderly patients. The overall rates of patient and kidney graft survival are comparable to those of younger patients. Donor age > or =55 years had a negative effect on patient and kidney graft survival.

Triple arterial reconstruction improves vascularization of whole pancreas for transplantation.

We assessed the effect on duodenal stump vascular supply of reconstruction of the gastroduodenal artery performed before pancreas transplantation. The median pancreas graft and patient survival times were 144 and 72 months for cases with or without gastrointestinal bleeding. Transmural blood flow values were significantly different between the donor duodenal stump and the recipient anastomosed jejunum (P < .01). The rate of gastrointestinal bleeding was lower in patients who received a pancreatic graft with back-table reconstruction of the gastroduodenal artery (P = .005).

Cardiovascular benefits of simultaneous pancreas-kidney transplant versus kidney alone transplant in diabetic patients.

UNLABELLED: The aim of our study was to demonstrate the cardiovascular benefits of simultaneous pancreas-kidney transplantation when compared to kidney-alone transplants in diabetic recipients. PATIENTS AND METHODS: A total of 386 renal transplants were performed from 1985 to 2004, including 262 (68%) in diabetic recipients and 124 (32%) in nondiabetics. Among the former group, 200 kidneys were transplanted simultaneously to the pancreatic graft (KP group) and 62 were kidney-alone transplants (KA group). The mean time on dialysis was 31 +/- 20 months (range 0-126 months). The duration of diabetes was 24 +/- 7 years (range 5-51 years). Ninety-nine percent of the patients were on renal replacement therapy (79% on hemodialysis and 20% on peritoneal dialysis). RESULTS: Among 262 patients, 28 (11%) died due to a cardiovascular event, which was higher among KA patients compared with the KP group (P = .004). Overall patient survival was significantly higher in the KP group when compared with the KA group (log-rank: P = .0004). Patient survivals were 80% and 70% versus 70% and 40% at 5 and 10 years in the KP and KA groups, respectively. Kidney graft survivals were 81% and 60% versus 63% and 26% at 5 and 10 years in the KP and KA groups, respectively. Pancreas graft survival was 70% and 50% at 5 and 10 years, respectively. CONCLUSIONS: This clinical evaluation, even if retrospective, confirmed that simultaneous pancreas-kidney transplantation has a protective effect against cardiovascular mortality in diabetic recipients affected by end-stage renal disease.

Multivariate analysis of factors affecting patient and graft survival after renal transplant.

AIM: To evaluate factors affecting patient and kidney survival after renal transplant. PATIENT AND METHODS: Among 361 patients undergoing renal transplant: 52% (n = 189) were simultaneous with pancreas transplant (SPKT group) and 48% (n = 172), a kidney transplant alone (KT group). Out of 361 patients, 75% (n = 270) were diabetics. The patients were 220 (61%) men and 141 (39%) women of mean age 41 +/- 9 years. The mean time of dialysis was 42 +/- 21 months (range 0 to 126), and the mean duration of diabetes 24 +/- 7 years (range 5 to 51). A Cox regression analysis was done. RESULTS: The multivariate analysis revealed that in the final model diabetes and donor age were significant predictors of kidney graft survival; moreover, diabetes and recipient age were predictors of patient survival. Overall patient survival was significantly greater among nondiabetic patients (P = .002) or in diabetic patients who received SPKT, when compared with diabetics in whom only the kidney was transplanted (P = .001). CONCLUSIONS: Diabetes and donor age were independent prognostic factors affecting kidney graft survival after renal transplant, and recipient age and diabetes were prognostic factors affecting patient survival. Combined pancreas and kidney transplantation should be offered to patients with end-stage diabetic nephropathy.

Islet isolation for allotransplantation: variables associated with successful islet yield and graft function.

AIMS/HYPOTHESIS: Efficient islet isolation is an important prerequisite for successful clinical islet transplantation. Although progressively improved, islet yield and quality are, however, unpredictable and variable and require standardisation. METHODS: Since 1989 we have processed 437 pancreases using the automated method. The donor characteristics, pancreas procurement, and digestion and purification procedures including a wide enzyme characterisation of these pancreases were analysed and correlated with islet yield and transplant outcome. RESULTS: By univariate analysis, islet yield was significantly associated with donor age (r=0.16; p=0.0009), BMI (r=0.19; p=0.0004), good pancreas condition (p=0.0031) and weight (r=0.15; p=0.0056), total collagenase activity (r=0.22; p=0.0001), adjusted collagenase activity/mg (r=0.18; p=0.0002), collagenase activity/solution volume (r=0.18; p=0.0002) and neutral protease activity/solution volume (r=0.14; p=0.0029). A statistically significant contribution to the variability of islet yield in a multivariate analysis performed on donor variables was found for donor BMI (p=0.0008). In a multivariate analysis performed on pancreas variables a contribution was found for pancreas weight (p=0.0064), and for a multivariate analysis performed on digestion variables we found a contribution for digestion time (p=0.0048) and total collagenase activity (p=0.0001). Twenty-four patients with type 1 diabetes received single islet preparations from single donors. In these patients, multivariate analyses showed that the reduction in insulin requirement was significantly associated with morphological aspects of islets (p=0.0010) and that 1-month C-peptide values were associated with islet purity (p=0.0071). CONCLUSIONS/INTERPRETATION: These data provide baseline donor, digestion and purification selection criteria for islet isolation using the automated method and indicate that the morphological aspect may be a clinically relevant measure of islets on which the decision for transplant can be based.

Outcome of simultaneous kidney pancreas transplantation: a single center analysis.

The aim of this study was to evaluate the outcome of simultaneous kidney pancreas transplantation (SKPT) by various surgical techniques. The 161 patients submitted to SKPT underwent the following: 36 pancreas with duct occlusion (from 1985 to 1989), 75 with whole pancreas with bladder diversion (from 1990 to 1998), and 50 whole pancreas with enteric diversion (40 with systemic and 10 with portal drainage) (from 1999 to September 2002). A positive effect on patient survival was evident using enteric diversion versus the duct occlusion group (P = .005), and versus the bladder diversion group (.035), and on pancreas graft survival in the enteric diversion versus the duct occlusion group (P < .028). These improvements may be due to refined donor and patient selection criteria, surgical technique, and immunosuppression.

Long-term survival after kidney and kidney-pancreas transplantation in diabetic patients.

PURPOSE: To investigate the influence of diabetes mellitus on patient and graft survival among renal versus renal-pancreatic recipients. METHODS: Among 270 renal transplants performed from 1985 to 2002, a total of 204 (75%) were in diabetic patients and 66 (25%) in nondiabetic patients. Among the 204 diabetic patients 161 (60%) kidneys were transplanted simultaneously with a pancreatic graft (SKPT group). The overall group of patient included 164 (61%) men and 106 (39%) women with mean time on dialysis of 31 +/- 21 months (range 0 to 126 months). The mean duration of diabetes was 24 +/- 7 years (range 5 to 51 years). Ninety-nine percent of the patients were on renal replacement therapy (79% hemodialysis and 20% peritoneal dialysis). RESULTS: The overall rejection rate was similar (NS). Both patient and kidney graft survival rates were worse in diabetics. Patient survival was 82% at 5 years among patients undergoing SKPT, 60% in diabetics receiving only a kidney, and 88% in nondiabetic transplanted patients. Kidney graft survival at 5 years was 77% in diabetics receiving SKPT, 68% in diabetics receiving a kidney alone, and 82% in nondiabetic patients. Overall patient survival was significantly greater among nondiabetics (P =.002) or in diabetics who received SKPT compared with diabetics who only had a kidney transplant (P =.001). CONCLUSIONS: This retrospective clinical evaluation confirms that combined pancreas and kidney transplantation should be the first choice to insulin-dependent diabetes mellitus (IDDM) patients with end-stage diabetic nephropathy.

Simultaneous pancreas-kidney transplantation: short- and long-term results.

Simultaneous kidney and pancreas transplantation (SKPT) is the treatment of choice for a majority of type I diabetic patients with end-stage renal disease. With continual refinements in surgical technique and an evolving immunosuppressive arsenal, graft and patient survival have continually improved. The purpose of this study was to evaluate the short- and long-term results of SKPTs performed in 174 recipients from June 1985 to March 2003 including 37 segmental grafts with duct occlusion, 73 whole pancreas transplants with bladder diversion, and 64 whole pancreas grafts with enteric diversion. The series includes 160 cases with systemic drainage and 14 with portal drainage. In the segmental pancreas group, patient survival was 85%, 76%, and 53% with pancreas survival of 67%, 36%, and 15%, and kidney survival of 82%, 63%, and 15%, respectively, at 1, 5, and 10 years. Among the bladder diversion group, patient survival was 94%, 83%, and 73% pancreas survival 72%, 67%, and 65%, and kidney survival 89%, 78%, and 58%, respectively, 1, 5, and 10 years. Among the enter diversion group patient survival was 90% and 90% at 12 and 108 months, pancreas survival 80% and 65%, and kidney survival 85% and 85%, respectively. There were significant differences between curves of survival distribution according to the surgical technique applied for patients (P =.04), pancreas (P =.007), and kidney (P =.005). Based on the results from our study, the short- and long-term prognosis after SKPT is satisfactory, especially compared to the outcomes of long-term dialysis among patients with end-stage renal disease caused by type I diabetes.

[Simultaneous pancreas-kidney transplantation: a single center experience on 148 cases]. / Risultati del trapianto simultaneo di rene e pancreas: esperienza su 148 casi.

AIM: To evaluate the outcome of simultaneous pancreas transplantation (SKPT) focusing on the surgical technique applied. PATIENTS AND METHODS: One hundred forty-eight patients were submitted to SKPT 33 with segmental pancreas with duct occlusion (from 1985 to 1990), 77 with whole pancreas with bladder diversion (from 1990 to 1998) and 38 whole pancreas with enteric diversion (29 with systemic and 9 with portal drainage) (from 1998 to December 2001). RESULTS: Patient survival was 92%, 82%, 63% at 1, 5, and 10 years respectively. Kidney survival was 87%, 75%, and 48% at 1, 5, 10 years. Pancreas graft survival was 71%, 58%, and 46% at 1, 5, 10 years. In the enteric diversion group patient, kidney, pancreas survival at one year was 93%, 92%, and 75%. A positive effect on patient survival was evident in enteric diversion versus duct occlusion group (p = 0.03), but not versus bladder diversion group and on pancreas graft survival in enteric diversion versus duct occlusion group (p < 0.01). CONCLUSIONS: These data suggest that SKPT has become a successful intervention for patients with type I diabetes and end stage renal disease. Reasons for these improvements include improved donor and patient selection criteria, refinements in surgical technique and better immunosuppression.

Metabolic effects of restoring partial beta-cell function after islet allotransplantation in type 1 diabetic patients.

Successful intraportal islet transplantation normalizes glucose metabolism in diabetic humans. To date, full function is not routinely achieved after islet transplantation in humans, with most grafts being characterized by only partial function. Moreover, the duration of full function is variable and cannot be sufficiently predicted with available methods. In contrast, most grafts retain partial function for a long time. We hypothesized that partial function can restore normal protein and lipid metabolism in diabetic individuals. We studied 45 diabetic patients after islet transplantation. Labeled glucose and leucine were infused to assess whole-body glucose and protein turnover in 1) 6 type 1 diabetic patients with full function after intraportal islet transplantation (FF group; C-peptide > 0.6 nmol/l; daily insulin dosage 0.03 +/- 0.02 U x kg(-1) body wt x day(-1); fasting plasma glucose < 7.7 mmol/l; HbA1c < or = 6.5%), 2) 17 patients with partial function (PF group; C-peptide > 0.16 nmol/l; insulin dosage < 0.4 U x kg(-1) body wt x day(-1)), 3) 9 patients with no function (NF group; C-peptide < 0.16 nmol/l; insulin dosage > 0.4 U x kg(-1) body wt x day(-1)), and 4) 6 patients with chronic uveitis as control subjects (CU group). Hepatic albumin synthesis was assessed in an additional five PF and five healthy volunteers by means of a primed-continuous infusion of [3,3,3-2H3]leucine. The insulin requirement was 97% lower than pretransplant levels for the FF group and 57% lower than pretransplant levels for the PF group. In the basal state, the PF group had a plasma glucose concentration slightly higher than that of the FF (P = 0.249) and CU groups (P = 0.08), but was improved with respect to the NF group (P < 0.01). Plasma leucine (101.1 +/- 5.9 micromol/l) and branched-chain amino acids (337.6 +/- 16.6 micromol/l) were similar in the PF, FF, and CU groups, and significantly lower than in the NF group (P < 0.01). During insulin infusion, the metabolic clearance rate of glucose was defective in the NF group versus in the other groups (P < 0.01). Both the basal and insulin-stimulated proteolytic and proteosynthetic rates were comparable in the PF, FF, and CU groups, but significantly higher in the NF group (P = 0.05). In addition, the PF group had a normal hepatic albumin synthesis. Plasma free fatty acid concentrations in the PF and FF groups were similar to those of the CU group, but the NF group showed a reduced insulin-dependent suppression during the clamp. We concluded that the restoration of approximately 60% of endogenous insulin secretion is capable of normalizing the alterations of protein and lipid metabolism in type 1 diabetic kidney recipients, notwithstanding chronic immunosuppressive therapy. The results of the present study indicate that "success" of islet transplantation may be best defined by a number of metabolic criteria, not just glucose concentration/metabolism alone.

Insights from a successful case of intrahepatic islet transplantation into a type 1 diabetic patient.

We report a case of long-term (>4 yr) successful intrahepatic islet transplantation into a type 1 diabetic patient chronically immunosuppressed for a prior kidney graft. The exogenous insulin requirement decreased progressively after transplantation, and insulin treatment was withdrawn at 6 months. Glycosylated hemoglobin levels were in the normal range at 1 and 2 yr (5.3%) and increased slightly above the upper normal limit at 3 and 4 yr (6.3% and 6.4%). Fasting C peptide levels remained stable during the entire follow-up, but the proinsulin to insulin ratios increased dramatically at yr 3. Glycemic levels after an oral glucose tolerance test showed a diabetic profile at 1 yr, a normal profile at 2 yr, and an impaired glucose tolerance profile at 3 yr. Intravenous glucose tolerance test-induced first phase insulin release, present at 1 and 2 yr, disappeared at 3 yr. Diabetes-related autoantibodies (islet cell antibodies, glutamic acid decarboxylase antibodies, and tyrosine phosphatase-like protein antibodies) were undetectable before transplantation and remained so during the entire follow-up. The patient died of myocardial infarction 50 months after transplantation while she was still in good metabolic control (glycosylated hemoglobin, <6.8%) in the absence of exogenous insulin administration. The autoptic liver showed well granulated islets, richly vascularized and without evidence of lympho-mononuclear cell infiltration. The morphometrically extrapolated intrahepatic beta-cell mass was 99.9 mg. In conclusion, this successful islet graft showed a bell-shaped clinical effect, maximal at 2 yr after transplantation, followed by a slow progressive decline. The absence of allo- and autoreactivities against the transplanted islets points to a nonimmune-mediated beta-cell loss as the cause of graft functional deterioration.

Polarity of the first episode, clinical characteristics, and course of manic depressive illness: a systematic retrospective investigation of 320 bipolar I patients.

In 320 patients with established bipolar I disorder, we examined the past course on the basis of polarity at onset (depressive, mixed, and manic). Despite the obvious limitations of retrospective methodology, information on course parameters in a large sample of affective disorders is most practically obtained by such methodology. We believe that our systematic interview of patients and their relatives--as well as the systematic study of their records--minimized potential biases. Depressive onsets were the most common, accounting for 50%, followed by mixed and manic onsets in about equal proportion. In general, the polarity of episodes over time reflected polarity at onset. Those with depressive onset had significantly higher levels of rapid cycling, as well as suicide attempts, but were significantly less likely to develop psychotic symptoms. Mixed onsets, too, had high rates of suicide attempts, but differed from depressive onsets in having significantly more chronicity yet negligible rates of rapid cycling at follow-up evaluation. Because cases with depressive onset had received significantly higher rates of psychopharmacologic treatment, our data are compatible with the hypothesis that antidepressants may play a role in the induction of rapid cycling. Overall, our data support the existence of distinct longitudinal patterns within bipolar I disorder, which in turn appear correlated with the polarity at onset. In particular, rapid cycling and mixed states emerge as distinct psychopathologic processes.

Mechanisms of coordination of Ca2+ signals in pancreatic islet cells.

Within pancreatic islet cells, rhythmic changes in the cytosolic Ca2+ concentration have been reported to occur in response to stimulatory glucose concentrations and to be synchronous with pulsatile release of insulin. We explored the possible mechanisms responsible for Ca2+ signal propagation within islet cells, with particular regard to gap junction communication, the pathway widely credited with being responsible for coordination of the secretory activity. Using fura-2 imaging, we found that multiple mechanisms control Ca2+ signaling in pancreatic islet cells. Gap junction blockade by 18 alpha-glycyrrhetinic acid greatly restricted the propagation of Ca2+ waves induced by mechanical stimulation of cells but affected neither Ca2+ signals nor insulin secretion elicited by glucose elevation. The source of Ca2+ elevation was also different under the two experimental conditions, the first being sustained by release from inner stores and the second by nifedipine-sensitive Ca2+ influx. Furthermore, glucose-induced Ca2+ waves were able to propagate across cell-free clefts, indicating that diffusible factors can control Ca2+ signal coordination. Our results provide evidence that multiple mechanisms of Ca2+ signaling operate in beta-cells and that gap junctions are not required for intercellular Ca2+ wave propagation or insulin secretion in response to glucose.

Effects of cryopreservation on in vitro and in vivo long-term function of human islets.

BACKGROUND: The possibility of performing transplantation several days after explant seems to be a peculiarity of islet grafts, and the opportunity to cryopreserve human islets may permit an indefinite period for modulating the recipient immune system. The aim of the present study was the evaluation of in vitro and in vivo functional properties of cryopreserved human islets. METHODS: We used six consecutive human islet preparations not suitable for an immediate transplantation in diabetic patients because the limited islet mass separated. The in vitro function of cryo and fresh islets was studied by determination of insulin and glucagon secretion in response to such classical stimuli as glucose (16.7 mM), glucose (16.7 mM) + 3-isobutyl-1-methylxanthine (0.1 mM), arginine (10 mM), and tolbutamide (100 microM). In vivo islet function was assessed through intravenous glucose tolerance tests performed at 15, 30, 60, and 90 days after transplantation of 1000 hand-picked fresh or cryopreserved islets in nude mice. RESULTS: Basal secretion of true insulin was significantly higher in cryopreserved islets than in fresh ones. The response of cryopreserved islets to arginine and glucose + isobutyl-1-methylxanthine seemed partially impaired. Proinsulin-like molecule secretion seemed higher in cryopreserved than in fresh islets in response to all secretagogues used, and the difference was statistically significant for arginine. The capacity of human cryopreserved islets to maintain a correct metabolic control in diabetic nude mice was progressively lost in 3 months. CONCLUSIONS: These findings showed that cryopreservation affects the function of isolated human islets, maintaining in vivo function for a limited period of time.