M. Carmellini

The biguanide compound metformin prevents desensitization of human pancreatic islets induced by high glucose

Pancreatic islet desensitization by high glucose concentrations is a temporary and reversible state of beta-cell refractoriness to glucose (and possibly other secretagogues), due to repeated or prolonged pre-exposure to increased glucose concentrations. We evaluated whether the oral antidiabetic agent metformin affects this phenomenon in isolated, human pancreatic islets, and whether the possible effects of the biguanide are influenced by the presence of a sulphonylurea, glyburide. Islets prepared from five human pancreases were incubated for 24 h in M199 culture medium containing either 5.5 or 22.2 mmol/l glucose, with or without a therapeutic concentration (2.4 microg/ml) of metformin. Then, the islets were challenged with either 3.3 mmol/l glucose, 16.7 mmol/l glucose, or 3.3 mmol/l glucose + 10 mmol/l arginine, and insulin release was measured. After incubation in the absence of metformin, the human islets exposed to 22.2 mmol/l glucose showed no significant increase in insulin release when challenged with 16.7 mmol/l glucose (confirming that hyperglycemia desensitizes pancreatic beta-cells). In the presence of metformin, the islets fully maintained the ability to significantly increase their insulin release in response to glucose, even when previously exposed to 22.2 mmol/l glucose. No major effect on arginine-induced insulin release was observed, whatever the culture conditions. The protective action of metformin was observed also when glyburide was present in the incubation medium, whereas the sulphonylurea alone did not affect insulin release from the islets previously exposed to high glucose concentrations. These in vitro results suggest that metformin can prevent the desensitization of human pancreatic islets induced by prolonged exposure to increased glucose concentrations.

Renal Transplant From Very Old Donors: How Far Can We Go?

Background. The organ shortage has led many transplant centers to accept kidneys from old, suboptimal deceased donors, and make increasing use of old-for-old allocation systems. We report the experience of an Italian transplant center in the utilization of “ultra-old” (>75 years old) donors. Methods. Sixty grafts from donors aged 75 years or older (mean age 79.1 years, range 75–90 years) were used for 38 patients: 16 as single and 22 as double transplants. Results. The actuarial graft survival rate was 73.7% for year 1, 69.8% for year 2, and 64.0% for year 3. The patient survival rate was 81.2% and remained stable for years 1, 2, and 3. The delayed graft function rate was 57.9%. Acute rejection and chronic allograft nephropathy rates were comparable with our other expanded criteria donors. The majority of the patients had stable creatinine levels, between 2 and 3 mg/mL after the second month, with sufficient creatinine clearance. Conclusions. Our results seems encouraging with patient and graft survival rates, complication rates, and renal function parameters being slightly worse than in expanded criteria donors, but still generally acceptable. The use of old kidneys in old recipients, bearing in mind their usual life expectancy, gives them a properly functioning kidney and improved quality of life.

PERIPHERAL BENZODIAZEPINE RECEPTORS IN ISOLATED HUMAN PANCREATIC ISLETS

Peripheral benzodiazepine receptors have been shown in some endocrine tissues, namely the testis, the adrenal gland, and the pituitary gland. In this work we evaluated whether peripheral benzodiazepine receptors can be found in the purified human pancreatic islets and whether they may have a role in insulin release. Binding of the isoquinoline compound [3H]1‐(2‐chlorophenyl‐N‐methyl‐1‐methyl‐propyl)‐3‐isoquinolinecarboxamide ([3H]PK‐11195), a specific ligand of peripheral benzodiazepine receptors, to cellular membranes was saturable, and Scatchards analysis of the saturation curve demonstrated the presence of a single population of binding sites, with an affinity constant value of 9.20 ± 0.80 nM and a maximum number of binding sites value of 8913 ± 750 fmol/mg of proteins. PK‐11195 and 7‐chloro‐1,3‐dihydro‐1‐methyl‐5‐(p‐chlorophenyl)‐2H‐1,4‐benzodiazepin‐2‐on (Ro 5‐4864) significantly potentiated insulin secretion from freshly isolated human islets at 3.3 mM glucose. These results show the presence of peripheral benzodiazepine receptors in purified human pancreatic islets and suggest their role in the mechanisms of insulin release. J. Cell. Biochem. 64:273–277.

Effects of glibenclamide and metformin (alone or in combination) on insulin release from isolated human pancreatic islets

Abstract Isolated human pancreatic islets were prepared by collagenase digestion and density gradient purification, and the effects of glibenclamide (0.5 and 5.0 µmol/l) and metformin (20 and 200 µmol/l), alone or in combination, on insulin release were evaluated at varying glucose concentrations. At 3.3 mmol/l glucose level, the addition of 5.0 µmol/l glibenclamide or 5.0 µmol/l glibenclamide plus 200 µmol/l metformin caused a significant increase of insulin release, compared with glucose alone. At 16.7 mmol/l glucose concentration, a significant increase of insulin secretion, compared with glucose alone, was produced by the addition of either 5.0 µmol/l glibenclamide, 200 µmol/l metformin, or both 5.0 µmol/l glibenclamide and 200 µmol/l metformin. The effect of the combination of the two drugs was significantly higher than that with either drug used alone. Thus, glibenclamide was shown to have an insulinotropic effect on human islets at both low and high glucose concentrations, and metformin at high glucose concentrations. A possible synergistic effect of glibenclamide and metformin at high glucose concentrations is also suggested.

Effect of cilastatin on cyclosporine-induced acute nephrotoxicity in kidney transplant recipients

BACKGROUND Cyclosporine (CsA)-induced acute nephrotoxicity could be reduced by prevention of parenchymal accumulation of the drug itself. The objective of this prospective study was to evaluate whether cilastatin, an inhibitor of active tubular resorption of CsA, reduces CsA-induced acute nephrotoxicity in kidney graft recipients. METHODS Sixty-nine kidney recipients with immediate graft functional recovery were randomly assigned to either the treatment group (imipenem/cilastatin, n=33) or the control group (ceftazidime, n=36). All patients followed a standard immunosuppressive regimen based on CsA and low-dose prednisone. Graft function and CsA levels were evaluated 3, 5, 10, 15, and 30 days after transplantation. RESULTS Compared with the control group, imipenem/cilastatin administration reduced the serum creatinine level in the first 2 weeks after transplantation, reaching a significant effect on postoperative day 10 (P<0.05). No significant differences were demonstrated between the two groups for CsA levels, patient and graft survival, and all the other examined parameters. CONCLUSIONS Our findings support the hypothesis that cilastatin administration can reduce CsA-induced acute nephrotoxicity after kidney transplantation.

Effect of kidney transplantation on quality of life measures

Assessing the quality of life should be an essential part of the long-term results of surgery, particularly for those procedures that may influence a patients lifestyle and body image. Eliminating the need for dependence on chronic hemodialysis, kidney transplantation improves the patients autonomy but exposes them to the side-effects of immunosuppression and the constant threat of rejection. The purpose of this study was to compare the quality of life of patients on the waiting list for a kidney transplantation to that of those already transplanted at our Center to quantify carefully the impact of this therapy on the patients physical, emotional, and social well-being. Computer analysis of the data collected from self-administered questionnaires revealed that the vast majority of successfully transplanted patients experience a significant improvement in almost all the areas investigated compared with the pretransplant group. In addition, we tried to use the questionnaire to predict which type of patient will adjust more fully to the impact of a kidney transplantation and which will probably need posttransplant psychological care and social support. Aside from clinical factors such as the time spent on hemodialysis before transplantation, the gender, the age, as well as the source of the organ (living vs. cadaver donor) seem to play a role in the final outcome of a successful kidney transplantation.

A randomized study comparing three cyclosporine-based regimens in cadaveric renal transplantation: results at 7 years

AFTER the worldwide adoption of cyclosporine (CsA) for maintenance immunosuppression, a striking improvement in renal transplant survival has been obtained. Recipients of first cadaver allografts commonly achieve 1-year graft survival approaching 90% with low patient mortality. Yet, in spite of the large experience accumulated with CsA, we still do not know which CsA-based protocol is better in the long-term. Although CsA was administered alone in clinical transplantation at the beginning of its use, steroid-free immunosuppression has not been accepted in most transplant centers because of the risk of nephrotoxicity associated with the large dose of CsA required for successful immunosuppresion and the increased risk of acute rejection, which could expose patients to chronic graft dysfunction in the long term. The results obtained using an association between CsA and steroids (double therapy) or CsA, steroids, and azathioprine (triple therapy) did not show any significant differences in either the patient or graft survival rates or in the incidence of drug-related complications. We recently reported the results of a randomized trial simultaneously comparing the three treatment schemes. We have now reanalyzed the data by extending the follow-up at 7 years after transplantation.

Effects of prolonged exposure to pancreatic glucagon on the function, antigenicity and survival of isolated human islets.

Certain clinical conditions are associated with inappropriately high levels of circulating glucagon. To date, little information is available about the direct effects of prolonged exposure of human islet cells to pancreatic glucagon. In the present study we evaluated the function, antigenicity and survival of human islets exposed for 24 h to human pancreatic glucagon.

Lymphokine release during co-culture of human lympho-mononuclear cells and fresh or cultured human, porcine and bovine pancreatic islets

In this study we evaluated whether isolated human (HI), porcine (PI) and bovine (BI) islets, either fresh (Fr) or cultured for 4 weeks (4w) affect cytokine release from human lymphomononuclear cells (LMC) differently. We prepared LMC from peripheral blood by density gradient purification and co-cultured 1×106 LMC for 24 h with 100 hand-picked islets, either within 48 h of isolation or after culture for 4 weeks. Soluble interleukin-2 receptor (IL-2R), interferon-gamma (IFN), interleukin-4 (IL-4) and interleukin-10 (IL-10) were measured by sandwich enzyme-linked immunoadsorbent assay. Compared with controls (Ctrl, LMC without islets), Fr-HI, Fr-PI and Fr-BI caused a similar increase of IL-2R and IFN release, whereas 4w-HI and 4w-BI did not lead to any significant production of these two cytokines. IL-10 concentrations increased with Fr-PI and Fr-BI, but not with Fr-HI, and no major effect of the 4-week culture was seen. IL-4 levels were below the detection limit of the method used in these experiments. Thus, fresh allo- and xeno-islets caused a similar increase of the release of cytokines known to be markers of Th1 activation, whereas the release of IL-10, a marker of Th2 activation, increased with xeno-, but not with allo-islets; culturing the islets for 4 weeks decreased Th1, but not Th2 activation.

Role of Ultrasound in Renal Transplantation

Ultrasound examination of a renal transplant was performed in 27 patients over a period of 28 months; there were kidneys from 12 living and 15 cadaveric donors. The ultrasonic scans were performed over a period ranging from 2 days to 12 years following transplantation. We were able to observe and describe the echographic findings of the normal evolution of a well functioning renal transplant, acute tubular necrosis, acute and chronic rejection, perirenal fluid collection, and obstructive uropathy. Ultrasound evaluation of renal transplant was accurate in the diagnosis of postoperative complications together with clinical and laboratory findings. Ultrasound imaging is independent of renal function and can be performed quickly as often as necessary. Percutaneous procedures, including fine needle aspiration, biopsy, aspiration of fluid collection, and positioning of the pyelostomy catheter can be performed under ultrasonic guidance.