Mechanism of the diabetogenic action of cyclosporin A

Antidiabetic therapy in post kidney transplantation diabetes mellitus

Post-transplantation diabetes mellitus (PTDM) is a common complication after kidney transplantation that affects up to 40% of kidney transplant recipients. By pathogenesis, PTDM is a diabetes form of its own, and may be characterised by a sudden, drug-induced deficiency in insulin secretion rather than worsening of insulin resistance over time. In the context of deteriorating allograft function leading to a re-occurrence of chronic kidney disease after transplantation, pharmacological interventions in PTDM patients deserve special attention. In the present review, we aim at presenting the current evidence regarding efficacy and safety of the modern antidiabetic armamentarium. Specifically, we focus on incretin-based therapies and insulin treatment, besides metformin and glitazones, and discuss their respective advantages and pitfalls. Although recent pilot trials are available in both prediabetes and PTDM, further studies are warranted to elucidate the ideal timing of various antidiabetics as well as its long-term impact on safety, glucose metabolism and cardiovascular outcomes in kidney transplant recipients.

Antipsychotics-induced metabolic alterations: focus on adipose tissue and molecular mechanisms

The use of antipsychotic drugs for the treatment of mood disorders and psychosis has increased dramatically over the last decade. Despite its consumption being associated with beneficial neuropsychiatric effects in patients, atypical antipsychotics (which are the most frequently prescribed antipsychotics) use is accompanied by some secondary adverse metabolic effects such as weight gain, dyslipidemia and glucose intolerance. The molecular mechanisms underlying these adverse effects are not fully understood but have been suggested to involve a dysregulation of adipose tissue homeostasis. As such, the aim of this paper is to review and discuss the role of adipose tissue in the development of secondary adverse metabolic effects induced by atypical antipsychotics. Data analyzed in this article suggest that atypical antipsychotics may increase adipose tissue (particularly visceral adipose tissue) lipogenesis, differentiation/hyperplasia, pro-inflammatory mediator secretion and insulin resistance and decrease adipose tissue lipolysis. Consequently, patients receiving antipsychotic medication could be at risk of developing obesity, type 2 diabetes and cardiovascular disease. A better knowledge of the impact of these drugs on adipose tissue homeostasis may unveil strategies to develop novel antipsychotic drugs with less adverse metabolic effects and to develop adjuvant therapies (e.g. behavioral and nutritional therapies) to neuropsychiatric patients receiving antipsychotic medication.

The impact of cytomegalovirus infection on new-onset diabetes mellitus after kidney transplantation: a review on current findings

CONTEXT

New onset diabetes mellitus after transplantation (NODAT) increases the risk of cardiovascular disease, rate of infections, graft rejection and graft loss as well as decreases patient and graft survival rates. There is a controversy surrounding the impact of cytomegalovirus (CMV) infection in the development of NODAT. This meta-analysis aims to identify the role of CMV infection leading to the development of NODAT in kidney recipient patients.

EVIDENCE ACQUISITIONS

We searched several electronic databases, including PubMed, Embase, Medline, Scopus, Trip Database and Google Scholar for studies that completely fulfill our criteria between January 1990 and January 2014 RESULTS: Seven studies with 1389 kidney transplant patients were included in this metaanalysis.The mean age of patients ranged from 42.8 to 48.8 years and males made up 53% to 75% of patients in the cohort studies. The incidence of NODAT varies from 14.3% to 27.1% in these studies. Overall adj OR was 1.94 [exp (0.66)] with a 95% CI of 1.26-2.98 [exp (0.23) and (1.09)]. There was no significant publication bias based on the Begg's and Egger's test (p value = 0.17 and 0.54, respectively).

CONCLUSIONS

Our study showed that CMV infection is a risk factor for increasing incidence of NODAT. Thus, prophylaxis against CMV infection after kidney transplantation is strongly suggested. However, further clinical trials and cohorts are needed to confirm this association.

Nutrition in kidney transplantation

Organ transplantation has progressively established itself as the preferred therapy for many end-stage organ failures. However, many of these chronic diseases and their treatments can negatively affect nutritional status, leading to malnutrition and mineral deficiencies.Nutritional status is an important determinant of the clinical outcome of kidney transplant recipients.Malnutrition and obesity may represent a contraindication to transplantation in many cases and may increase the risk of postoperative complications after the transplantation. Nutritional support in kidney transplant recipients is challenging, since it must take into account the pre-transplant nutritional status, the side effects of immunosuppression, the function of the transplanted graft, the presence of infection, and the general status of the patient at the time of the transplantation.With these considerations in mind, we reviewed current literature on the impact of nutritional status on the outcome of kidney transplantation.

New onset of diabetes after transplantation - an overview of epidemiology, mechanism of development and diagnosis

New onset of diabetes after transplantation (NODAT) is a serious and common complication following solid organ transplantation. NODAT has been reported to occur in 2% to 53% of renal transplant recipients. Several risk factors are associated with NODAT, however the mechanisms underlying were unclear. Renal transplant recipients who develop NODAT are reported to be at increased risk of infections, cardiovascular events, graft loss and patient loss. It has been reported that the incidence of NODAT is high in the early transplant period due to the exposure to the high doses of corticosteroids, calcineurin inhibitors and the physical inactivity during that period. In addition to these risk factors the traditional risk factors also play a major role in developing NODAT. Early detection is crucial in the management and control of NODAT which can be achieved through pretransplant screening there by identifying high risk patients and implementing the measures to reduce the development of NODAT. In the present article we reviewed the literature on the epidemiology, risk factors, mechanisms involved and the diagnostic criteria in the development of NODAT. Development of diagnostic tools for the assessment of β-cell function and determination of the role of glycemic control would include future area of research.

Novel views on new-onset diabetes after transplantation: development, prevention and treatment

New-onset diabetes after transplantation (NODAT) is associated with increased risk of allograft failure, cardiovascular disease and mortality, and therefore, jeopardizes the success of renal transplantation. Increased awareness of NODAT and the prediabetic states (impaired fasting glucose and impaired glucose tolerance, IGT) has fostered previous and present recommendations, based on the management of type 2 diabetes mellitus (T2DM). Unfortunately, the idea that NODAT merely resembles T2DM is potentially misleading, because the opportunity to initiate adequate anti-hyperglycaemic treatment early after transplantation might be given away for 'tailored' immunosuppression in patients who have developed NODAT or carry personal risk factors. Risk factor-independent mechanisms, however, seem to render postoperative hyperglycaemia with subsequent development of overt or 'full-blown' NODAT, the unavoidable consequence of the transplant and immunosuppressive process itself, at least in many cases. A proof of the concept that timely preventive intervention with exogenous insulin against post-transplant hyperglycaemia may decrease NODAT was recently provided by a small clinical trial, which is awaiting confirmation from a multicentre study. However, because early insulin therapy aimed at beta-cell protection seems to contrast the currently recommended, stepwise approach of 'watchful waiting' prior to pancreatic decompensation, we here aim at reviewing recent concepts regarding the development, prevention and treatment of NODAT, some of which seem to challenge the traditional view on T2DM and NODAT. In summary, we suggest a novel, risk factor-independent management approach to NODAT, which includes glycaemic monitoring and anti-hyperglycaemic treatment in virtually everybody after transplantation. This approach has widespread implications for future research and is intended to tackle NODAT and also ultimately cardiovascular disease.

Diabetes and kidney transplantation: past, present, and future

Diabetes mellitus is the most common etiology for end stage renal disease (ESRD) worldwide and in the United States. The incidence of morbidity and mortality is higher in diabetic patients with ESRD due to increased cardiovascular events. Patients with type 2 diabetes who receive a renal allograft have a higher survival rate compared with patients who are maintained on chronic hemodialysis therapy, but there is scarcity of data on long-term graft outcomes. Most recently the development of new onset diabetes after transplantation (NODAT) poses a serious threat to patient and allograft survival. Pre-emptive transplantation and the use of living donors have improved overall survival. In addition, critical management of glucose, blood pressure, and cholesterol are some of the factors that can help minimize adverse outcomes in both patients with pre-existing diabetes and patients who develop NODAT. Future clinical trials are warranted to improve therapeutic medical management of these patients thus influencing graft attrition.

Impact of obesity on children undergoing liver transplantation

Controversies exist with respect to the mortality of patients undergoing liver transplantation at the extremes of the body mass index (BMI). For pediatric liver transplantation, weight is usually the only factor considered in survival analysis. A review of the United Network for Organ Sharing database (1987-2007) revealed 9701 pediatric patients (<18 years old) who underwent primary liver transplantation. Patients were stratified into 5 BMI categories established by the World Health Organization according to their Z score, which was based on age, gender, and BMI: -3, -2, 0, +2, and +3. The survival rates in these 5 categories were compared with Kaplan-Meier survival curves and log-rank testing. Patients with thinness (Z score = -2) and severe thinness (Z score = -3) had significantly (P < 0.0001) lower survival at 1 year (84.4%) versus the survival (88.7%) of the normal and overweight groups (Z score = 0 and Z score = + 2, respectively). For patients with obesity (Z score = +3), there was no significant difference in survival early after transplantation, but their mortality gradually increased in the later years after transplantation. By 12 years after liver transplantation, the obese group had significantly (P = 0.04) lower survival (72%) than the normal and overweight groups (77%). In conclusion, liver transplantation holds increased risk for obese pediatric patients. Thin pediatric patients experience early mortality after liver transplantation, and obese pediatric patients experience late mortality after liver transplantation. Transplant management can be modified to optimize the care of these patients.

Abnormal glucose metabolism and metabolic syndrome in non-diabetic kidney transplant recipients early after transplantation

BACKGROUND

Abnormal glucose metabolism (AGM) and metabolic syndrome (MS) are individually associated with a poor cardiovascular outcome in kidney transplant recipients. We prospectively studied the relationship between AGM and MS in non-diabetic kidney transplant recipients early after transplantation.

METHODS

A total of 203 de novo kidney transplant recipients underwent standard 2-hr glucose tolerance test 10 weeks after transplantation. Demographic and clinical characteristics were collected. AGM was defined as impaired fasting glucose, impaired glucose tolerance, and new onset diabetes after transplant according to the WHO criteria, and MS was defined according to the National Cholesterol Education Expert Panel criteria.

RESULTS

Overall, 97 patients (47.8%) met the diagnosis of AGM and 98 patients (48.3%) met the criteria of MS. AGM and MS are highly associated (chi, P<0.001). Fasting plasma glucose levels before the transplant are independent predictors common for AGM and MS. Age predicts AGM with and without MS, whereas body mass index before transplant predicts MS. Patients with impaired glucose tolerance and new-onset diabetes after transplant displayed significant worsening of their fasting plasma glucose levels during the 10-week observational period. MS and the components of MS, but not AGM, were associated with reduced transplant renal function (P=0.002).

CONCLUSION

The early screening of AGM and MS should be emphasized, and the role of early therapeutic interventions aimed at both conditions explored. The long-term follow-up of these patients will yield more insight on the significance of such findings.

Pilot study: association of traditional and genetic risk factors and new-onset diabetes mellitus following kidney transplantation

INTRODUCTION

New-onset diabetes mellitus, which occurs after kidney transplant and type 2 diabetes mellitus (T2DM), shares common risk factors and antecedents in impaired insulin secretion and action. Several genetic polymorphisms have been shown to be associated with T2DM. We hypothesized that transplant recipients who carry risk alleles for T2DM are "tipped over" to develop diabetes mellitus in the posttransplant milieu.

METHODS

We investigated the association of genetic and traditional risk factors present before transplantation and the development of new-onset diabetes mellitus after kidney transplantation (NODAT). Markers in 8 known T2DM-linked genes were genotyped using either the iPLEX assay or allelic discrimination (AD)-PCR in the study cohort testing for association with NODAT. We used univariate and multivariate logistic regression models for the association of pretransplant nongenetic and genetic variables with the development of NODAT.

RESULTS

The study cohort included 91 kidney transplant recipients with at least 1 year posttransplant follow-up, including 22 who developed NODAT. We observed that increased age, family history of T2DM, pretransplant obesity, and triglyceridemia were associated with NODAT development. In addition, we observed positive trends, although statistically not significant, for association between T2DM-associated genes and NODAT.

CONCLUSIONS

These findings demonstrated an increased NODAT risk among patient with a positive family history for T2DM, which, in conjunction with the observed positive predictive trends of known T2DM-associated genetic polymorphisms with NODAT, was suggestive of a genetic predisposition to NODAT.

Transplantation in diabetic kidney failure patients: modalities, outcomes, and clinical management

Diabetes mellitus (DM) is a common and devastating disease, affecting up to 19.3 million Americans. It is the leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD) in the United States. Diabetic patients with ESRD have a high incidence of cardiovascular disease and death. For those kidney transplant patients with no history of DM prior to transplantation, the development of new onset diabetes after transplantation (NODAT) also poses a serious threat to both graft and patient survival. Kidney transplantation is the best renal replacement option for diabetic ESRD and has the potential to halt the progression of cardiovascular diseases. Early referral for transplant evaluation is essential for pre-emptive or early kidney transplantation in this cohort of patients. In type 1 DM patients with ESRD, simultaneous pancreas and kidney transplantation (SPK) should be encouraged; and in patients facing prolonged waiting time for SPK transplantation but with an available living donor, living donor kidney transplantation followed by pancreas after kidney transplantation (PAK) is a suitable alternative. Islet transplantation in type 1 diabetics is deemed experimental by Medicare, and easy access to this modality remains restricted to qualified patients enrolled in clinical trials or with private insurance. The optimal management of kidney transplant patients with pre-existent DM or NODAT involves a multi-pronged approach consisting of pharmacological and nonpharmacological intervention to address all potential cardiovascular risk factors such as glycemic and lipid control, blood pressure control, weight loss, and smoking cessation. Finally, re-transplantation should be recommended in suitable kidney transplant patients when the kidney allograft demonstrates continuous and progressive decline in function.

Calcineurin inhibitor effects on glucose metabolism and endothelial function following renal transplantation

BACKGROUND

Calcineurin inhibitors (CNI) are involved in the development of post-transplant diabetes mellitus (PTDM). Changes in insulin secretion and sensitivity contribute to the development of PTDM and are associated with endothelial function.

METHODS

In a pre-defined substudy of a previously published randomized trial in renal transplant recipients we compared the effect of CNI treatment (n = 23) with complete CNI-avoidance (n = 21) on insulin secretion and sensitivity (oral glucose tolerance test) as well as endothelial function (laser Doppler flowmetry), 10 wk and 12 months following transplantation.

RESULTS

Insulin sensitivity differed 10 wk post-transplant and was significantly better after 12 months in patients never treated with CNI drugs [0.091 (0.050) vs. 0.083 (0.036) micromol/kg/min/pmol/L, p = 0.043]. Insulin secretion tended to be higher in CNI treated patients at both time points (p = 0.068). Endothelial function was not significantly different at week 10 [540 (205) vs. 227 (565) arbitary units x minutes, p = 0.35] or month 12 [510 (620) vs. 243 (242), p = 0.33].

CONCLUSIONS

Findings in the present study indicate that long-term CNI treatment negatively affects glucose metabolism and this may contribute to the increased risk for premature cardiovascular disease in CNI treated renal transplant recipients. Further studies to elucidate this hypothesis are, however, needed.

Metabolic syndrome in liver transplantation: relation to etiology and immunosuppression

Excessive weight gain, hypertension, hyperlipidemia, and diabetes are frequently observed in patients having undergone liver transplantation (LTx). These alterations are probably multifactorial in origin, and cluster to generate a metabolic syndrome (MS), increasing the risk of cardiovascular events. We assessed the prevalence of MS (National Cholesterol Education Program-Adult Treatment Panel III criteria) in 296 LTx patients in the course of regular follow-up, at least 6 months after transplantation (median, 38 months). Several pre-LTx and post-LTx data were collected to identify the factors associated with the presence of MS. In a subset of 99 patients, insulin resistance was measured by the homeostasis model assessment. High blood pressure was present in 53% of cases, hyperlipidemia in 51%, high glucose in 37%, and enlarged waist circumference in 32%. Overall, MS (defined as 3 or more of the above features) was present in 44.5% of cases. Insulin resistance (homeostasis model assessment > 2.7) was observed in 41% of cases. Hypertension and hyperlipidemia were more frequent in subjects on cyclosporine than in tacrolimus-treated cases, whereas the type of immunosuppressive drug had no effect on the prevalence of diabetes, enlarged waist, and MS. In a logistic regression analysis, only pre-LTx body mass index (odds ratio, 1.20), body mass index increase (odds ratio, 1.18), and pre-LTx diabetes (odds ratio, 2.36) predicted MS; age, gender, etiology of liver disease, time from LTx, type of immunosuppressive drug, and previous hepatocellular carcinoma were removed from the model. Disorders related to MS are frequent in LTx patients, and are related to both pre-LTx conditions and to weight gain. Weight control is mandatory in LTx patients to prevent risk factors of premature atherosclerosis.

Metabolic Syndrome and Atherosclerotic Events in Renal Transplant Recipients

BACKGROUND

Metabolic syndrome (MS) is a known cardiovascular risk factor in the general population. We explored the influence of MS on the occurrence of atherosclerotic events (AEs) after renal transplantation.

METHODS

Three hundred thirty-seven renal transplant recipients were included in the study. Various parameters (e.g., anthropometric and biological) were measured 1 year after transplant.

RESULTS

One year after transplant, 32% of the study population met criteria for MS. Older age, male gender, pretransplant high body mass index, and an increase in body mass index>or=5% in the first year after transplant were predictive factors for development of MS at 1 year after transplant. Forty-two patients (12.4%) experienced AEs during the 8 years of follow-up. The cumulated incidence of AEs was greater in patients with MS compared with others without MS (25% vs. 7%; P<0.001). In multivariate analysis, patients with MS at 1 year after transplant had an increased risk of AE (hazard ratio 3.40, 95% confidence interval 1.58-7.32, P=0.002). Older age, low creatinine clearance, high C-reactive protein level, and a past history of cardiovascular disease were other independent risk factors for AE.

CONCLUSIONS

Similar to the general population, MS is an independent risk factor for AE after renal transplantation. Relevant preventive measures targeting different aspects of MS would then have a potential impact on prevalence of AE in this population.

Effects of non-steroid immunosuppressive drugs on insulin secretion in transplantation

Post-transplantation diabetes (PTD) is a serious complication in organ transplantation: not only does it increase the risk of graft dysfunction; it also increases cardiovascular morbidity and mortality. PTD incidence is correlated with age, non-Caucasian ethnic background, a family history of diabetes, excess weight, hepatitis C infection and steroid boluses for potential rejection. Different mechanisms might explain post-transplantation glucose metabolism disorders: ischemia-reperfusion disorders, whether renal, hepatic or cardiac, are responsible for insulin-resistance, which is increased by post-transplantation steroids; the detrimental effect of non-steroid immunosuppressive drugs on insulin-secretion could also be involved, especially with calcineurin inhibitors. In vivo and in vitro studies have shown that tacrolimus has inhibitory effects on insulin-secretion, while these effects are less obvious for cyclosporin, and were mainly demonstrated in vitro. Mycophenolate has no overt effect on insulin-secretion. Sirolimus and everolimus, two mTOR inhibitors, have shown controversial results in this realm. The effects of sirolimus (most often studied mTOR inhibitor) appear to depend on serum levels, cell type (ss cell or cell line), species (human or animal) and also environmental nutrients. At therapeutic concentrations, a stimulatory effect on insulin secretion was observed on human beta cells. This might explain the success of islet cell transplantation with the Edmonton protocol. Finally, steroids are mainly detrimental because they accentuate insulin resistance whereas anticalcineurins, in particular tacrolimus, lower insulin synthesis.

Functional and morphological study of cultured pancreatic islets treated with cyclosporine

Cyclosporine A (CsA), a potent immunosuppressive drug, has been found to induce glucose intolerance through its toxic effect on the endocrine pancreas. It is not exactly known whether CsA has a direct effect on the endocrine pancreas or induces its effect indirectly. The present study was therefore undertaken to examine the function and morphology of isolated pancreatic islets when they are directly exposed in vitro to CsA. Pancreatic islets were isolated from adult male Lewis rats using collagenase ductal perfusion technique. The islets were separated with the discontinuous Ficoll gradient technique and further purified by hand picking of the non-islet tissue. The islets were cultured in RPMI-1640, pH 7.4 and maintained at 37 degrees C in a humid atmosphere of 5% (v/v) carbon dioxide in air. Cyclosporine was added to the culture medium to give a final concentration of 1 microg/ml (therapeutic dose), 5 microg/ml (toxic dose), or vehicle (control). Islets were harvested at 1, 4 and 10 days of culture and processed for functional or histological study. The functional study of the islets cultured with 1 microg/ml CsA showed insulin and C-peptide contents similar to those of the control islets. The islets cultured with 5 microg/ml CsA showed a marked decrease in insulin and C-peptide contents. Glucose-dependent insulin release was variable. C-peptide release was lower than that of the control following both the therapeutic and toxic doses of CsA. Phase contrast microscopy showed that the islets cultured with 1 microg/ml CsA were mostly normal looking with a well-defined regular periphery; a few islets had ill-defined or irregular peripheries. The islets cultured with 5 microg/ml CsA had ill-defined irregular peripheries at 1 day, and were dense and forming clumps at 4 and 10 days following culture. There was a decrease in the islet number following the therapeutic dose; the decrease was more following the toxic dose of CsA. The islet diameters increased after the therapeutic dose, but slightly decreased following the toxic dose of CsA. Islets showed a weakly positive immunoperoxidase reaction for insulin that was weaker following the toxic dose of CsA. It is concluded that CsA has a direct effect on B-cells that was proved by the functional and morphological changes seen in the pancreatic islets cultured in vitro.

Validation of insulin resistance indexes in a stable renal transplant population

OBJECTIVE

The purpose of this study was to investigate the validity of established insulin resistance indexes, based on fasting blood parameters, in a stable renal transplant population.

RESEARCH DESIGN AND METHODS

Fasting insulin, homeostasis model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI), and McAuley's index were assessed for correlation and agreement with whole-body glucose uptake (M value) divided by prevailing serum insulin concentrations (I value) assessed during a hyperinsulinemic-euglycemic clamp in 51 stable renal transplant recipients, who were at a median of 7.5 years after transplant. Multivariate linear regression analyses were used to determine independent risk factors for insulin resistance.

RESULTS

The M/I value correlated with fasting insulin concentration (r = -0.56), HOMA (r = -0.53), QUICKI (r = 0.52), and McAuley's index (r = 0.61) (all P < 0.01). Linear regression showed agreement between all indexes and insulin resistance. However, McAuley's index showed the strongest agreement irrespective of age, sex, renal allograft function, and obesity. In multivariate analysis, fasting insulin concentration (beta = -0.59, P = 0.002), fasting triglyceride concentration (beta = -0.33, P = 0.04), and BMI (beta = -1.22, P = 0.05) were independently associated with the M/I value.

CONCLUSIONS

All investigated insulin resistance indexes were valid estimates of insulin resistance in the long-term stable renal transplant population. However, correlation and agreement were strongest for McAuley's index. In addition to fasting insulin and triglyceride concentrations, of which McAuley's index is composed, only BMI seemed to be independently associated with insulin resistance in this population.

Challenges in the diagnosis and management of new-onset diabetes after transplantation

With the availability of newer and more potent immunosuppressive agents, post-transplant survival has markedly improved. However, these agents, together with the rising age of transplant recipients, have been associated with a rise in the incidence of new-onset diabetes after transplantation (NODAT). Besides the traditional risk factors for diabetes mellitus, such as age, obesity, hypertension, and family history of diabetes, additional risk factors for NODAT are identified. These include immunosuppressive therapy, hepatitis C infection, acute rejection, and deceased donor kidney transplant. In this article, we discuss the epidemiology, risk factors, pathophysiology, clinical course, and therapeutic and diagnostic challenges of this emerging disease.

New-onset diabetes mellitus in transplant patients: pathogenesis, complications, and management

New-onset diabetes mellitus after transplantation is characterized by decreased insulin secretion and increased insulin resistance secondary to the effects of immunosuppression. Although impaired beta cell function appears to be the primary mechanism of calcineurin inhibitor-induced new-onset diabetes, impaired peripheral glucose utilization also appears to contribute to insulin resistance and abnormal glucose metabolism. Because transplant recipients who develop new-onset diabetes mellitus after transplantation are at increased risk for infections, cardiovascular disease, and poor patient and graft survival, all patients should undergo careful assessment of risk for diabetes prior to transplantation and regular screening for the development of hyperglycemia thereafter. For patients in high-risk groups, including certain ethnic backgrounds, older adults, and the very young, and patients with hepatitis C, consideration should be given to initiating immunosuppressive therapy with agents that are less diabetogenic. Recent guidelines include more stringent criteria for diagnosis and stress the importance of strict glycemic control. Diet, exercise, and weight management are core components of treatment with addition of oral hypoglycemic agents and/or insulin as needed to achieve control. Concomitant measures include aggressive control of lipids and blood pressure to reduce the risk of cardiovascular disease. New-onset diabetes after transplantation is a serious issue affecting patient and graft outcomes and warrants the attention of all health care professionals involved in assessing and managing the transplant recipient.

Post-Transplantation Diabetes Mellitus

Post-transplantation diabetes mellitus (PTDM) is defined as sustained hyperglycemia developing in any patient without history of diabetes before transplantation, that meets the current diagnostic criteria by the American Diabetes Association or the World Health Organization. Several risk factors have been identified: age, nonwhite ethnicity, and glucocorticoid therapy for rejection and chronic immunosuppression with cyclosporine and especially tacrolimus. The pathophysiology of this condition resembles that of type 2 diabetes mellitus: pretransplantation end-stage liver/renal and heart disease are insulin-resistant states, and after transplantation, glucocorticoids induce further peripheral insulin insensitivity. The "second hit" appears to be an acquired (yet reversible) insulin secretion defect resulting from the calcineurin inhibitors cyclosporine and tacrolimus. An international panel of experts has recently published the proceeding of a Consensus Conference proposing strategies for the screening, prevention and management of PTDM. Future directions include pre- and post-transplantation glucose load testing for high-risk individuals and pharmacological agents to decrease insulin resistance and to preserve beta-cell function.

Angiotension converting enzyme inhibition and calcium channel blockage improves cyclosporine induced glucose intolerance in rats

The aim of this study was to evaluate the effects of quinapril, valsartan, and amlodipin on glucose tolerance in cyclosporine (CsA)-toxic rats. Among 40 male Wistar rats 32 were administered cyclosporine (CsA) (15 mg/kg) intraperitoneally for 6 weeks. Quinapril (10 mg/kg per day) (group Q), valsartan (40 mg/kg per day) (group V), and amlodipine (10mg/kg per day) (group A) were administered to individual sets of eight CsA-treated animals via the drinking water with the remaining untreated hosts followed as a control group (group C) and 8 healthy controls (group H). A Glucose-tolerance test was performed by administering oral glucose (2 g/kg) followed by blood samples obtained from the tail vein at baseline as well as 30,60,90, and 120 minutes after the glucose load. Glucose area under the curve (AUC) was calculated according to the trapezoidal rule. CsA levels were determined using an immunofluorescence method. Kruskal Wallis ANOVA test was used for statistical analysis. Median CsA levels were 1968 ng/mL, 1982 ng/mL, 1580 ng/mL, 1600 ng/mL; and glucose AUC, 232.4 +/- 130 mg/min per dL, 63.1 +/- 25 mg/min per dL, 115.0 +/- 90 mg/min per dL, 47.4 +/- 34 mg/min per dL 53.4 +/- 38 mg/min per dL for groups C,Q,V,A and H, respectively. Quinapril-treated and amilodipine-treated rats displayed a lower glucose AUC than group C (P <.01), which had higher glucose levels than healthy controls (P <.001). In summary, CsA treated rats show impaired glucose tolerance, which is improved by quinapril or amlodipine treatment. Angiotensin converting enzymes inhibitors and calcium channel blockers affect beta cell function rather than insulin sensitivity.

Insulin resistance as putative cause of chronic renal transplant dysfunction

Transplantation is the preferred organ replacement therapy for most patients with end-stage renal disease. Despite impressive improvements over recent years in the treatment of acute rejection, approximately half of all grafts will loose function within 10 years after transplantation. Chronic renal transplant dysfunction, also known as transplant atherosclerosis, is a leading cause of late allograft loss. To date, no specific treatment for chronic renal transplant dysfunction is available. Although its precise pathophysiology remains unknown, it is believed that it involves a multifactorial process of alloantigen-dependent and alloantigen-independent risk factors. Obesity, posttransplant diabetes mellitus, dyslipidemia, hypertension, and proteinuria have all been identified as alloantigen-independent risk factors. Notably, these recipient-related risk factors are well-known risk factors for cardiovascular disease, which cluster within the insulin resistance syndrome in the general population. Insulin resistance is considered the central pathophysiologic feature of this syndrome. It is therefore tempting to speculate that it is insulin resistance that underlies the recipient-related risk factors for chronic renal transplant dysfunction. Recognition of insulin resistance as a central feature underlying many, if not all, recipient-related risk factors would not only improve our understanding of the pathophysiology of chronic renal transplant dysfunction, but also stimulate development of new treatment and prevention strategies.

Posttransplantation diabetes: a systematic review of the literature

OBJECTIVES

To systematically review the incidence of posttransplantation diabetes (PTD), risk factors for its development, prognostic implications, and optimal management.

RESEARCH DESIGN AND METHODS

We searched databases (MEDLINE, EMBASE, the Cochrane Library, and others) from inception to September 2000, reviewed bibliographies in reports retrieved, contacted transplantation experts, and reviewed specialty journals. Two reviewers independently determined report inclusion (original studies, in all languages, of PTD in adults with no history of diabetes before transplantation), assessed study methods, and extracted data using a standardized form. Meta-regression was used to explain between-study differences in incidence.

RESULTS

Nineteen studies with 3,611 patients were included. The 12-month cumulative incidence of PTD is lower (<10% in most studies) than it was 3 decades ago. The type of immunosuppression explained 74% of the variability in incidence (P = 0.0004). Risk factors were patient age, nonwhite ethnicity, glucocorticoid treatment for rejection, and immunosuppression with high-dose cyclosporine and tacrolimus. PTD was associated with decreased graft and patient survival in earlier studies; later studies showed improved outcomes. Randomized trials of treatment regimens have not been conducted.

CONCLUSIONS

Physicians should consider modification of immunosuppressive regimens to decrease the risk of PTD in high-risk transplant recipients. Randomized trials are needed to evaluate the use of oral glucose-lowering agents in transplant recipients, paying particular attention to interactions with immunosuppressive drugs.

Insulin release and suppression by tacrolimus, rapamycin and cyclosporin A are through regulation of the ATP-sensitive potassium channel

AIM

By focusing on the pancreatic beta cell response to tacrolimus, cyclosporin A (CsA) and rapamycin we hoped to identify immunophilin, calcineurin and/or novel mechanism involvement and advance the understanding of immunosuppressant regulated insulin control.

METHODS

A glucose responsive beta cell model was established in which the glucose response was blocked by immunosuppressant treatment and this model was used to further characterise this effect. Quantification of insulin release to immunosuppressants and specific inhibitors was used to identify the mechanism involved.

RESULTS

It was found that upon the addition of tacrolimus, rapamycin, or CsA, rapid and significant exocytosis of cellular insulin was seen. A dose response study of this effect revealed optimal concentration windows of 50- 80 nm for tacrolimus, 100-300 nm for rapamycin, and 7-12 mm for CsA in RIN-5F cells. Optimal insulin release for HIT-T15 cells was similar. Additional experiments demonstrate that immunosuppressant pretreatment blocked the subsequent immunosuppressant induced insulin release but not that of a thapsigargin control, suggesting that suppression and release are non-toxic, specific and in the same pathway. Further experiments showed that this insulin release was a calcium dependent process, which was blocked by inhibitors of l-type calcium channels. Continued studies showed that the specific ATP-sensitive potassium channel agonist diazoxide (150 mm) also blocked immunosuppressant-induced insulin release.

CONCLUSIONS

A model that fits this data is a novel calcineurin-independent immunophilin mediated partial closing of the ATP-sensitive potassium channel, which would lead to an initial insulin release but would reduce subsequent responses through this pathway.

Insulin resistance after renal transplantation: impact of immunosuppressive and antihypertensive therapy

OBJECTIVE

The purpose of the present study was to validate various surrogate estimates of insulin sensitivity (IS) in a renal transplant population and to assess the influence of immunosuppressive and antihypertensive therapy on insulin resistance (IR) after renal transplantation.

RESEARCH DESIGN AND METHODS

A total of 167 consecutive renal transplant recipients without previously known diabetes underwent a 75-g oral glucose tolerance test (OGTT) 3 months after renal transplantation. A total of 43 patients also underwent a euglycemic-hyperinsulinemic glucose clamp study. Six OGTT-derived IS indexes were validated against the euglycemic-hyperinsulinemic glucose clamp-derived IS index (ISI(CLAMP)).

RESULTS

The OGTT-derived ISI(TX) correlated closely with the ISI(CLAMP) (r = 0.58, P < 0.001). The other surrogate estimates of IS were also significantly but less well correlated with the ISI(CLAMP) (Spearman's correlation; r = -0.45 to 0.41, P = 0.003-0.050). In the univariate model, BMI, daily prednisolone dose, creatinine clearance, hypertension, number of antihypertensive agents, and use of diuretics or beta-blockers were negatively associated with ISI(TX) (P < 0.05). After multiple regression analysis, BMI (P < 0.001), daily prednisolone dose (P < 0.001), cytomegalovirus infection (P = 0.030), and triglycerides (P = 0.034) were shown to be independent predictors of posttransplant IR.

CONCLUSIONS

The OGTT-derived ISI(TX) may be a useful estimate of IS in Caucasian renal transplant recipients. Increasing daily prednisolone dose is an independent predictor of IR after renal transplantation. Hypertension and the use of beta-blockers and diuretics may also deteriorate IR in this group of patients.

Diabetic rats transplanted with adult porcine islets and immunosuppressed with cyclosporine A, mycophenolate mofetil, and leflunomide remain normoglycemic for up to 100 days

BACKGROUND

Transplantation of adult porcine islets (APIs) offers a possible means of treating diabetes. However, isolating APIs has been notoriously difficult. Furthermore, islet xenograft rejection must be prevented.

MATERIALS AND METHODS

APIs were isolated by a modified automated method. API quality was assessed by static glucose stimulation (SGS), by transplantation to diabetic nude mice and by intraperitoneal glucose tolerance tests (IPGTTs). The morphologic characteristics of API xenograft rejection in rats were studied immunohistochemically. Furthermore, APIs were transplanted to diabetic rats that were either left untreated or immunosuppressed with cyclosporine A (CsA), mycophenolate mofetil (MMF) and leflunomide (LEF). B-glucose and porcine C-peptide levels were monitored and grafts were studied morphologically.

RESULTS

Large numbers of APIs were isolated. At SGS, insulin release increased significantly. All nude mice transplanted with APIs were normoglycemic within 24 hr and remained so for up to 1 year. During IPGTTs, B-glucose levels were rapidly regulated to porcine levels. In untreated rats, API xenografts were destroyed within 6 days by a cellular infiltrate consisting mainly of macrophages. In untreated diabetic rats normoglycemia was sustained for 5.5+/-0.3 days. Rats immunosuppressed with CsA+MMF+LEF remained normoglycemic for 59.6+/-11.3 days. In 3 of 11 rats, normoglycemia was sustained for up to 101 days. Porcine C-peptide was detected in serum. At recurrence of hyperglycemia, many mononuclear cells were found close to the xenografts. However, only occasional cells infiltrated the grafts and many APIs were intact.

CONCLUSIONS

Well-functioning APIs can be isolated in large numbers. API xenografts can be protected from rejection and can maintain an adequate function for up to 100 days, in rats immunosuppressed with CsA+MMF+LEF.

Tapering off prednisolone and cyclosporin the first year after renal transplantation: the effect on glucose tolerance

BACKGROUND

Glucose intolerance is an untoward side effect of some immunosuppressive and anti-hypertensive drugs. The primary aim of the present prospective observational study was to test the hypothesis that tapering off prednisolone and cyclosporin (CsA) the first year after transplantation may have beneficial effects on glucose tolerance in renal transplant recipients.

METHODS

Ninety-one non-diabetic recipients were included, and 87 patients underwent a 75 g oral glucose tolerance test both 10 weeks and 1 year after renal transplantation. The change over time in 2-h blood glucose was compared with a number of variables potentially influencing glucose tolerance.

RESULTS

The proportion of glucose intolerant recipients was reduced from 55 to 34% during the study. Univariate linear regression analysis showed a significant association between the reduction in daily prednisolone dose down to 5 mg and decline in blood glucose (P=0.001), whereas weight gain was associated with increasing blood glucose (P=0.031). Each 1-mg reduction of prednisolone dose leads to an estimated decline in 2-h blood glucose of 0.12 mmol/l based on the multiple linear regression model (P=0.003). Twelve out of 22 patients with post-transplant diabetes mellitus (PTDM) at baseline improved to normal or impaired glucose tolerance. Ten PTDM-subjects who remained diabetic 1 year after transplantation had lower serum insulin levels during the oral glucose challenge, and five patients treated with anti-diabetic drugs at baseline required hypoglycaemic drugs also at follow up. The decline in CsA level of 100 microg/l and the lower number of patients treated with beta-blockers at follow-up, did not alter glucose tolerance significantly.

CONCLUSIONS

Tapering off prednisolone, but not CsA, significantly improves glucose tolerance during the first year after renal transplantation.

Post-transplant diabetes: incidence, relationship to choice of immunosuppressive drugs, and treatment protocol

Post-transplant diabetes mellitus (PTDM) is one of the feared complications of immunosuppressive therapy. Despite advances, including the introduction of the steroid-sparing calcineurin inhibitors, cyclosporine and tacrolimus, the incidence rate remains greater than 10% to 30%, especially in minority populations. PTDM increases the subsequent risk of both graft loss and patient death, and predisposes patients to all complications of diabetes, including retinopathy and neuropathy. Patients should be monitored closely, especially during the first 3 months post-transplant, and treated aggressively, should glucose intolerance be detected. Minimization of immunosuppression dose, diet, oral hypoglycemic agents, and insulin have all been used in the treatment of PTDM, however, the insulin-sensitizing agents have not been studied. It is hoped that newer immunosuppressive regimens and, ultimately, the ability to achieve tolerance will eventually solve the problem of PTDM.

The metabolic effects of cyclosporin and tacrolimus

The introduction of cyclosporin and, more recently, tacrolimus in the immunosuppression of transplanted patients has lead to prolonged graft survival and increased patients' life expectancy. It has been therefore possible to evaluate the effects of long-term treatment with these drugs and metabolic alterations in patients on cyclosporin or tacrolimus have been reported by several authors. In particular, the use of these drugs is associated with abnormalities of glucose and lipid metabolism. Post-transplant diabetes is more common with tacrolimus, probably due to more marked effects on the pancreatic beta-cells, whereas increased levels of cholesterol and triglycerides are more frequently associated with cyclosporin treatment, even though, in this latter case, steroid treatment seems to play a major role. Comparison and intervention studies must be planned to evaluate the best therapeutical approaches to control these abnormalities and to assess the possibility to further increase graft and patient survival by appropriate treatment of diabetes and hyperlipidemia.