Morphological and functional changes of islets of Langerhans in FK506-treated rats

Topical Tacrolimus and Mycophenolic Acid Therapy Synergizes with Low Dose Systemic Immunosuppression to Sustain Vascularized Composite Allograft Survival

AIM

The goal of this study was to evaluate whether topical administration of tacrolimus (TAC) and mycophenolic acid (MPA) at the transplant site enables vascularized composite allograft (VCA) survival with significant minimization of the dose and adverse effects of systemic TAC (STAC) immunosuppression.

MATERIALS AND METHODS

Lewis (Lew) rats received orthotopic hind limb allotransplants from fully mismatched Brown Norway (BN) donors. Group 1 (Controls) received no treatment. Other groups were treated with STAC at a dose of 1 mg/kg/day for 7 days. On post-operative day (POD) 8, the STAC dose was dropped to 0.1 mg/kg/day for Group 2 and maintained at 1 mg/kg for Group 3. Group 4 received topical application of TAC and MPA on the transplanted (Tx) limb starting POD 8 without STAC. Group 5 received topical TAC and MPA on the contralateral non-Tx limb and Group 6 received topical TAC and MPA on the Tx limb starting POD 8 along with low dose STAC (0.1 mg/kg/day). Treatment was continued until the study end point was reached, defined as either grade 3 rejection or allograft survival exceeding 100 days. .We conducted sequential LC-MS/MS measurements to assess TAC and MPA concentrations in both blood/plasma and allograft tissues. Additionally, we evaluated markers indicative of organ toxicity associated with STAC immunosuppression.

RESULTS

Compared to controls, topical therapy with TAC+MPA significantly prolonged allograft survival beyond 100 daysat very low dose STAC (0.1 mg/kg/day) (Group 6). The histopathological assessment of the grafts was consistent with the clinical outcomes. .Drug levels in blood/plasma remained low or undetectable, while allograft tissues showed higher drug concentrations compared to contralateral limb tissues (P<0.05). . Urinary creatinine clearance remained within the normal range at 2.5 mL/min.

CONCLUSION

Combination therapy with topical TAC and MPA synergizes with a very low dose, corticosteroid- free-STAC regimen and facilitates rejection-free, prolonged VCA survival without morbidity.

Synthetic Pharmacotherapy for Systemic Lupus Erythematosus: Potential Mechanisms of Action, Efficacy, and Safety

The pharmacological treatment of systemic lupus erythematosus (SLE) aims to decrease disease activity, progression, systemic compromise, and mortality. Among the pharmacological alternatives, there are chemically synthesized drugs whose efficacy has been evaluated, but which have the potential to generate adverse events that may compromise adherence and response to treatment. Therapy selection and monitoring will depend on patient characteristics and the safety profile of each drug. The aim of this review is to provide a comprehensive understanding of the most important synthetic drugs used in the treatment of SLE, including the current treatment options (mycophenolate mofetil, azathioprine, and cyclophosphamide), review their mechanism of action, efficacy, safety, and, most importantly, provide monitoring parameters that should be considered while the patient is receiving the pharmacotherapy.

Functional and Morphological Characteristics of Pancreatic Islet Lesions Induced by Quinolone Antimicrobial Agent Gatifloxacin in Rats

We characterized pancreatic islet lesions induced by several quinolones using functional and morphological examinations of the pancreatic islets in male rats orally administered gatifloxacin, lomefloxacin, or levofloxacin at 300 mg/kg for 14 consecutive days. Consequently, in contrast to lomefloxacin or levofloxacin, gatifloxacin increased serum glucose and glycosylated albumin on day 14 and elevated serum glucose tended to decrease insulin in the intravenous glucose tolerance test. Microscopically, only gatifloxacin induced cytoplasmic vacuoles containing eosinophilic homogenous contents in islet cells. Immunohistochemical examination revealed that vacuolated islet cells were positively stained for insulin, demonstrating they were pancreatic β cells. Electron microscopy showed that the cytoplasmic vacuoles represented dilated cisterna of the rough endoplasmic reticulum filled with electron-lucent materials in pancreatic β cells. Moreover, insulin secretory granules were drastically decreased in vacuolated islet cells, suggesting impaired insulin synthesis and/or transport. This gatifloxacin-induced pancreatic toxicity in rats was considered to be associated with high pancreatic drug distribution. These results demonstrated that gatifloxacin provoked functional and morphological pancreatic β cell alteration associated with impaired insulin synthesis and/or transport, leading to hyperglycemia.

Clinical Profile of Patients With Diabetes Mellitus and Liver Transplantation: Results After a Multidisciplinary Team Intervention

BACKGROUND

Over the years, survival after liver transplantation has increased and metabolic complications are becoming more common, contributing to patients' morbidity and mortality. The objectives of this study were to describe a population of patients with hepatic transplantation and diabetes mellitus (DM), evaluate the frequency of metabolic complications, and assess the impact of a multidisciplinary team on DM management.

MATERIALS AND METHODS

This was a retrospective study involving interview and medical record analysis of 46 consecutive patients followed at the diabetes mellitus and liver transplantation unit of a tertiary university hospital, all evaluated by a multidisciplinary team.

RESULTS

Of all patients, 76.1% were men, with a median age 60 years old (interquartile range: 56 to 65 years) and liver transplantation time of 5 years (interquartile range: 0.6-9 years). Hypertension, hypercholesterolemia, hypertriglyceridemia, alcoholism, and smoking were present in 47.8%, 34.8%, 23.9%, 34.8%, and 30.4% of the patients, respectively. The most frequent immunosuppressant in use was tacrolimus (71.1%). Regarding nutritional status, 37.9% of patients were classified as overweight according to body mass index, and 41.2% were considered overweight according to the triceps skin fold. The median glycosylated hemoglobin and weight before and after intervention of the multidisciplinary team in all 46 patients were, respectively, 7.6% (5.7% to 8.8%) versus 6.5% (5.7% to 7.7%); P = .022 and 70.5 kg (64.7 to 82.0 kg) versus 71.6 kg (65.0 to 85.0 kg); P = .18.

CONCLUSIONS

Hypertension and dyslipidemia were common in transplanted patients with DM. Intervention of the multidisciplinary team resulted in a significant improvement in glycosylated hemoglobin without significant weight gain.

Differential influence of tacrolimus and sirolimus on mitochondrial-dependent signaling for apoptosis in pancreatic cells

To examine and compare the mitochondria-related cellular mechanisms by which tacrolimus (TAC) or sirolimus (SIR) immunosuppressive drugs alter the pancreatic exocrine and endocrine β-cell fate. Human exocrine PANC-1 and rat endocrine insulin-secreting RIN-m5F cells and isolated rat islets were submitted to 1-100 nM TAC or SIR. In cultures, insulin secretion was measured as endocrine cell function marker. Apoptosis was quantified by annexin 5 and propidium iodide staining. Cleaved caspase-3, Bax apoptosis indicators, and p53, p21 cell cycle regulators were detected by Western blot. Cell cycle and mitochondrial membrane potential (ΔΨm) were analyzed by flow cytometry and SA-beta-galactosidase (SA-β-gal) activity by fluorescence microscopy. Only TAC reduced insulin secretion by RIN-m5F after 24 h. TAC and SIR promoted moderate apoptosis in both PANC-1 and RIN-m5F after 24 h. Apoptosis was associated with up-regulated Bax (threefold) and cleaved caspase-3 (fivefold) but only in PANC-1, while p53 and p21 were up-regulated (twofold) in both cell lines. ΔΨm was impaired only in PANC-1 by TAC and SIR. Only SIR prompted cell cycle arrest in both cell lines. The induction of a premature senescence-like phenotype was confirmed in isolated islets by SA-β-gal activity. TAC and SIR are early inducers of pancreatic cell dysfunction and apoptosis but differentially alter endocrine and exocrine cells via mitochondrial-driven pathways. In rat islets, TAC and SIR prompt a senescence-like phenotype.

Npas4 Transcription Factor Expression Is Regulated by Calcium Signaling Pathways and Prevents Tacrolimus-induced Cytotoxicity in Pancreatic Beta Cells

Cytosolic calcium influx activates signaling pathways known to support pancreatic beta cell function and survival by modulating gene expression. Impaired calcium signaling leads to decreased beta cell mass and diabetes. To appreciate the causes of these cytotoxic perturbations, a more detailed understanding of the relevant signaling pathways and their respective gene targets is required. In this study, we examined the calcium-induced expression of the cytoprotective beta cell transcription factor Npas4. Pharmacological inhibition implicated the calcineurin, Akt/protein kinase B, and Ca(2+)/calmodulin-dependent protein kinase signaling pathways in the regulation of Npas4 transcription and translation. Both Npas4 mRNA and protein had high turnover rates, and, at the protein level, degradation was mediated via the ubiquitin-proteasome pathway. Finally, beta cell cytotoxicity of the calcineurin inhibitor and immunosuppressant tacrolimus (FK-506) was prevented by Npas4 overexpression. These results delineate the pathways regulating Npas4 expression and stability and demonstrate its importance in clinical settings such as islet transplantation.

CRTC2 is required for β-cell function and proliferation

Previous work in insulinoma cell lines has established that calcineurin plays a critical role in the activation of cAMP-responsive element binding protein (Creb), a key transcription factor required for β-cell function and survival, by dephosphorylating the Creb coactivator Creb-regulated transcription coactivator (Crtc)2 at 2 regulatory sites, Ser171 and Ser275. Here, we report that Crtc2 is essential both for glucose-stimulated insulin secretion and cell survival in the β-cell. Endogenous Crtc2 activation is achieved via increasing glucose levels to the physiological feeding range, indicating that Crtc2 is a sensor that couples ambient glucose concentrations to Creb activity in the β-cell. Immunosuppressant drugs such as cyclosporin A and tacrolimus that target the protein phosphatase calcineurin are commonly administered after organ transplantation. Chronic use is associated with reduced insulin secretion and new onset diabetes, suggestive of pancreatic β-cell dysfunction. Importantly, we show that overexpression of a Crtc2 mutant rendered constitutively active by introduction of nonphosphorylatable alanine residues at Ser171 and Ser275 permits Creb target gene activation under conditions when calcineurin is inhibited. Taken together, these data suggest that promoting Crtc2-Creb activity is required for β-cell function and proliferation and promoting this pathway could ameliorate symptoms of new onset diabetes after transplantation.

Childhood onset diabetes posttransplant in a girl with TCF2 mutation

Heterozygous mutations of TCF2 (transcription factor 2) have been associated with maturity onset diabetes of the young, renal malformations, hyperuricemia, and occasionally internal genital malformations in female. We report a female patient with bilateral renal hypodysplasia and de novo heterozygous TCF2 gene mutation. At the age of 9 yr, she developed transient ketoacidosis immediately posttransplant, temporarily requiring insulin. During glucocorticoid tapering, impaired glucose tolerance persisted and overt insulin-dependent diabetes mellitus developed 1 yr later. Pathogenic factors which might have played a role in the acceleration of diabetes were (i) switch from cyclosporine to tacrolimus, (ii) weight excess, and (iii) cytomegalovirus infection. TCF2 analysis might, therefore, be of interest in patients with congenital abnormalities of the kidney and the urinary tract in order to improve posttransplant management in terms of steroid and tacrolimus exposure.

Increased body mass index but not common vitamin D receptor, peroxisome proliferator-activated receptor γ, or cytokine polymorphisms confers predisposition to posttransplant diabetes

CONTEXT

Posttransplant diabetes mellitus (PTDM) is a major complication after solid organ transplantation. The use of corticosteroids and calcineurin inhibitors, especially tacrolimus, are significant risk factors. However, it is not clear what genetic factors modify the risk. Evidence suggests vitamin D deficiency, perturbed glucose homeostasis, and increased inflammation all play roles in the development of diabetes.

OBJECTIVE

To investigate whether common vitamin D receptor (VDR), cytokine, and peroxisome proliferator-activated receptor γ (PPARγ) polymorphisms are correlated with the development of PTDM.

DESIGN

DNA was isolated from the peripheral blood of 51 kidney transplant recipients with PTDM and 72 patients without diabetes pretransplant or posttransplant at the time of follow-up. The genotypes for 5 polymorphisms, 1 each in VDR, PPARγ, INFγ, TGFβ1, and TNF, were determined using direct sequencing. Age, sex, number of acute rejection episodes, follow-up length, ethnicity, body mass index, and the frequency of alleles and genotypes for each polymorphism were compared between the 2 groups.

RESULTS

Body mass index was the only factor that was statistically different between the 2 groups (P  =  .001). The frequency of different alleles and genotypes for each of the 5 polymorphisms did not differ between the 2 groups.

CONCLUSIONS

These results indicate that increased body mass index is a significant risk factor for the development of PTDM. However, none of the genetic polymorphisms studied confer predisposition to PTDM with the current sample size.

Unique cellular and mitochondrial defects mediate FK506-induced islet β-cell dysfunction

OBJECTIVE

To determine biological mechanisms involved in posttransplantation diabetes mellitus caused by the immunosuppressant tacrolimus (FK506).

METHODS

INS-1 cells and isolated rat islets were incubated with vehicle or FK506 and harvested at 24-hr intervals. Cells were assessed for viability, apoptosis, proliferation, cell insulin secretion, and content. Gene expression studies by microarray analysis, quantitative polymerase chain reaction, and motifADE analysis of the microarray data identified potential FK506-mediated pathways and regulatory motifs. Mitochondrial functions, including cell respiration, mitochondrial content, and bioenergetics were assessed.

RESULTS

Cell replication, viability, insulin secretion, oxygen consumption, and mitochondrial content were decreased (P<0.05) 1.2-, 1.27-, 1.77-, 1.32-, and 1.43-fold, respectively, after 48-hr FK506 treatment. Differences increased with time. FK506 (50 ng/mL) and cyclosporine A (800 ng/mL) had comparable effects. FK506 significantly decreased mitochondrial content and mitochondrial bioenergetics and showed a trend toward decreased oxygen consumption in isolated islets. Cell apoptosis and proliferation, mitochondrial DNA copy number, and ATP:ADP ratios were not significantly affected. Pathway analysis of microarray data showed FK506 modification of pathways involving ATP metabolism, membrane trafficking, and cytoskeleton remodeling. PGC1-α mRNA was down-regulated by FK506. MotifADE identified nuclear factor of activated T-cells, an important mediator of β-cell survival and function, as a potential factor mediating both up- and down-regulation of gene expression.

CONCLUSIONS

At pharmacologically relevant concentrations, FK506 decreases insulin secretion and reduces mitochondrial density and function without changing apoptosis rates, suggesting that posttransplantation diabetes induced by FK506 may be mediated by its effects on mitochondrial function.

New-onset diabetes after transplantation: risk factors and clinical impact

With improvements in patient and graft survival, increasing attention has been placed on complications that contribute to long-term patient morbidity and mortality. New-onset diabetes after transplantation (NODAT) is a common complication of solid-organ transplantation, and is a strong predictor of graft failure and cardiovascular mortality in the transplant population. Risk factors for NODAT in transplant recipients are similar to those in non-transplant patients, but transplant-specific risk factors such as hepatitis C (HCV) infection, corticosteroids and calcineurin inhibitors play a dominant role in NODAT pathogenesis. Management of NODAT is similar to type 2 diabetes management in the general population. However, adjusting the immunosuppressant regimen to improve glucose tolerance must be weighed against the risk of allograft rejection. Lifestyle modification is currently the strategy with the least risk and the most benefit.

[Drug-induced hyperglycemia: a study in the French pharmacovigilance database]

OBJECTIVE

To analyse drugs inducing hyperglycemia by using data reported to the French spontaneous reporting system and recorded in the French PharmacoVigilance Database (FPVD).

METHODS

All cases with a report of hyperglycemia and/or diabetes in the French database between 1985 and 2008 were included in the study. We estimated the risk of hyperglycemia linked to drugs by the case/non-case method. Cases were reports including hyperglycemia and non cases all other reports. This risk was estimated through calculation of reporting odds ratios (ROR).

RESULTS

During this period, 1219 reports including the words "hyperglycemia and/or diabetes" were registered (0.34% of the database). This adverse drug reaction occurred 1 fold over 4 in diabetics or as a part of HIV infection. Effect was "serious" in approximatively 50% of cases. We found an increase of risk during exposition with methylprednisolone [ROR=43.5; 95% CI (37.3-50.8)], tacrolimus [ROR=25; 95% CI (17.9-34.8)], olanzapine [ROR=19.9; 95% CI (14.9-26.5)], prednisone [ROR=18.9; 95% CI (15.7-22.8)] or pentamidine [ROR=15.4; 95% CI (8.2-28.3)].

CONCLUSION

Drug classes most frequently found in FPVD linked to hyperglycemia are antiretroviral, steroidal anti-inflammatory, second generation neuroleptic, immunosuppressive and diuretic drugs.

Tacrolimus causes a blockage of protein secretion which reinforces its immunosuppressive activity and also explains some of its toxic side-effects

BACKGROUND

Tacrolimus (FK506) is a macrolide immunosuppressant drug from the calcineurin inhibitor family, widely used in solid organ and islet cell transplantation, but produces significant side-effects.

OBJECTIVE

This study examined the effect of FK506 on interleukin-2 (IL-2) and insulin secretion, establishing a novel characteristic of this drug that could explain its diverse adverse effects, and developed an experimental model for the simultaneous analysis of mRNA expression and protein secretion affected by this drug.

METHODS

The IL-2 levels when tacrolimus was administered were analysed by Western blot, immunocytochemistry and RT-PCR in a T lymphocyte cellular line (Jurkat) 24 h post-stimulation. The insulin levels when tacrolimus was administered were analysed 4 h after stimulation of glucose-induced insulin secretion in a pancreatic cellular line (MIN6).

RESULTS

The previously published information describes tacrolimus as only capable of partially blocking IL-2 mRNA expression. In our hands, the cellular content of IL-2 is almost undetectable in stimulated Jurkat cells and can be detected in cellular extracts only when the secretory pathway is blocked by brefeldin A (BFA). BFA added 2 h after the beginning of stimulation was able to inhibit IL-2 secretion, without affecting IL-2 mRNA expression. Therefore BFA utilization allowed us to establish a model to analyze the effect on IL-2 secretion, separately from its expression. Tacrolimus added before stimulation inhibits only IL-2 synthesis, but blocks IL-2 protein secretion when added 2 h after stimulation. Similarly, tacrolimus is also capable of blocking the glucose-stimulated secretion of insulin by MIN6 cells. An increase of the intracellular content can be detected concomitantly with a decrease of the hormone measured in the culture medium.

CONCLUSIONS

Results of this study indicate that tacrolimus possesses another important effect in addition to the inhibition of IL-2 gene transcription, namely the ability to act as a general inhibitor of the protein secretory pathway. These results strongly suggest that the diabetogenic effect of the immune suppressant FK506 could be caused by the blockade of insulin secretion. This novel effect also provides an explanation for other side-effects observed in immunosuppressive treatment.

New-onset diabetes mellitus after solid organ transplantation

New-onset diabetes mellitus is a common complication of solid organ transplantation and is likely to become even more common with the current epidemic of obesity in some countries. It has become clear that both new-onset diabetes and prediabetic states (impaired fasting glucose and impaired glucose tolerance) negatively influence graft and patient survival after transplantation. This observation forms the basis for recommending meticulous screening for glucose intolerance before and after transplantation. Although a number of clinical factors including age, weight, ethnicity, family history, and infection with hepatitis C are closely associated with the new-onset diabetes mellitus, immunosuppression with corticosteroids, calcineurin inhibitors and possibly sirolimus plays a dominant role in its pathogenesis. Management of new-onset diabetes after transplantation generally conforms to the guidelines for treatment of type 2 diabetes mellitus in the general population. However, further studies are needed to determine the optimal immunosuppressive regimens for patients with this disorder.

Exendin-4 does not promote Beta-cell proliferation or survival during the early post-islet transplant period in mice

Current pancreatic islet transplantation protocols achieve remarkable short-term success, but long-term insulin independence remains elusive. Hypoxic and inflammatory insults cause substantial early posttransplant graft loss while allo/autoimmunity and immunosuppressive drug toxicity threaten long-term graft mass and function. Exendin-4 (Ex4) is a GLP-1 receptor agonist that promotes beta-cell proliferation, survival, and differentiation. To determine whether Ex-4 displays potential as a graft-supportive agent, we transplanted 500 murine islets under the kidney capsule of syngeneic or allogeneic streptozocin-treated recipient mice and immediately initiated daily treatment with vehicle or Ex4. Graft beta-cell proliferation, death, and vascularity were assessed at 1, 3, and 10 days after syngeneic islet transplantation. For allogeneic recipients, blood glucose and body weight were assessed until glycemic deterioration. Ex-4 did not promote graft beta-cell proliferation, reduce beta-cell death, or enhance graft vascularity over the first 10 days after syngeneic islet transplantation. A trend toward prolongation of posttransplant euglycemia was observed with Ex4 treatment in nonimmune-suppressed allograft recipients, but its use in this setting was associated with frequent, severe hypoglycemia over the first 2 posttransplant days. Our findings do not support a beneficial effect of Ex-4 on islet grafts during the critical early posttransplant period, further, they demonstrate a significant hypoglycemic potential of Ex-4 in the first days after islet transplantation in mice. Optimal application of GLP-1 receptor agonists for long-term proliferative and survival benefits in transplantation may require earlier intervention prior to and/or during islet isolation for peri-transplant cytoprotection and administration beyond the period of engraftment.

Development of β-Cells in the Native Pancreas After Pancreas Allo-Transplantation in the Spontaneously Diabetic Torii Rat

BACKGROUND

We previously demonstrated the development of beta-cells in the native pancreas after syngeneic pancreas transplantation (PTx) in a model of type 2 diabetes, namely the Spontaneously Diabetic Torii (SDT; RT1 a) rat. In this study, we evaluated the effect of fully allogeneic PTx (allo-PTx) under immunosuppression on the native pancreases in the recipients.

MATERIALS AND METHODS

Diabetic 25-week-old SDT rats were divided into two groups: untreated controls and PTx-treated recipients. Dark Agouti (RT1 a) pancreases were then transplanted into the SDT rats. FK506 was administered daily postoperatively. Each group was examined for 15 weeks.

RESULTS

Control SDT rats showed a disappearance of the pancreatic and duodenal homeobox-1 (PDX-1) expression of the pancreases with the development of diabetes. In addition, the islets were gradually replaced by fibrosis, thus resulting in a marked decrease in the beta-cell mass at 40 weeks of age. On the other hand, in PTx recipients, islet-like cell clusters were found in the native pancreases. The beta-cell mass significantly increased in the native pancreases in the recipients at 10 and 15 weeks posttransplantation in comparison to the age-matched controls. Moreover, we observed the re-expression of PDX-1 in the islet-like cell clusters. Interestingly, insulin and glucagon double-positive stained cells in the mesenchyme and insulin single-positive cells in the ductal epithelium were also observed.

CONCLUSIONS

Our results indicated that the benefits of avoiding glucose toxicity by allo-PTx under immunosuppression could therefore induce the PDX-1 expression in the native pancreases, thus potentially resulting in the development of beta-cells in type 2 diabetic recipients.

Immunosuppressive agents: effects on glucose and lipid metabolism

Immunosuppressive therapies are critical elements in successful organ transplantation. Although immunosuppressant drugs are essential in preventing graft rejection and graft maintenance after transplantation, their use is complicated by adverse effects, many being detrimental to graft and even patient long-term survival. Commonly used agents are associated with dysregulated glucose metabolism and dyslipidemia. This article focuses on the effects of immunosuppressive agents on glucose and lipid metabolism. Adrenal effects of these drugs, where known, also are discussed.

Calcineurin/NFAT signaling in the beta-cell: From diabetes to new therapeutics

Pancreatic beta-cells in the islet of Langerhans produce the hormone insulin, which maintains blood glucose homeostasis. Perturbations in beta-cell function may lead to impairment of insulin production and secretion and the onset of diabetes mellitus. Several essential beta-cell factors have been identified that are required for normal beta-cell function, including six genes that when mutated give rise to inherited forms of diabetes known as Maturity Onset Diabetes of the Young (MODY). However, the intracellular signaling pathways that control expression of MODY and other factors continue to be revealed. Post-transplant diabetes mellitus in patients taking the calcineurin inhibitors tacrolimus (FK506) or cyclosporin A indicates that calcineurin and its substrate the Nuclear Factor of Activated T-cells (NFAT) may be required for beta-cell function. Here recent advances in our understanding of calcineurin and NFAT signaling in the beta-cell are reviewed. Novel therapeutic approaches for the treatment of diabetes are also discussed.

[Influence of tacrolimus and ciprofloxacin on glucose metabolism]

Tacrolimus is an immunosuppressive drug that causes glucose intolerance. On the other hand, ciprofloxacin, which is widely used in the treatment of infectious diseases, is known to cause hypoglycemia as a side effect. We investigated the effects of tacrolimus and ciprofloxacin on serum glucose and insulin levels in rats, as well as on insulin secretion and the viability of HIT-T15 cells. The rats received intraperitoneal injections of tacrolimus and/or ciprofloxacin for 1 week, and their arterial blood was sampled after the administration of glucose. HIT-T15 cells were cultured in the presence of tacrolimus and/or ciprofloxacin, and the insulin level in the supernatant was measured. Ciprofloxacin did not show a significant effect on serum glucose and insulin levels after multiple administrations in the rats. In contrast, rats in the tacrolimus treatment group showed low serum insulin and high serum glucose levels. Moreover, the coadministration of ciprofloxacin and tacrolimus resulted in higher glucose levels compared with tacrolimus alone 0.5 h after glucose stimulation. In addition, we observed that the rats administered tacrolimus and/or ciprofloxacin had low body weight and food intake. Tacrolimus caused a dose-dependent decrease in the viability of the HIT-T15 cells. Furthermore, both drugs were highly toxic to HIT-T15 cells. In contrast, tacrolimus alone and coadministration of the drugs resulted in no significant difference in insulin secretion. These results suggest that the cytotoxic effects of ciprofloxacin and tacrolimus cause a decrease in insulin secretion, leading to glucose intolerance.

Tacrolimus-induced diabetes in rats courses with suppressed insulin gene expression in pancreatic islets

An animal model of post-transplant diabetes was induced in rats by treating them daily with 0.1 mg/kg body weight of tacrolimus (FK506) in two i.p. injections. Rats developed hyperglycaemia and glucose intolerance after 9 days of treatment. Pancreatic islets, isolated from treated rats on different days, showed a decreased capacity to secrete insulin in response to 20 mM glucose at days 7 and 14. This suppression of insulin secretion was preceded by a reduction of the islet insulin content on day 5 that was progressively decreasing until the end of the treatment (day 14). Islet content of insulin mRNAs, transcribed from rat insulin genes 1 and 2, was strongly suppressed, similar to the insulin content, at days 7 and 14. Islet mass was not strikingly modified by tacrolimus treatment: the DNA content was slightly decreased at the end (day 14) and the rate of islet cell apoptosis slightly increased. Tacrolimus-induced diabetes in the rat seems to be mainly provoked by a decreased insulin gene transcription with little or no alteration of islet mass. This explains that the observed suppression of all the islet and animal parameters studied was completely reversed 2 weeks after interrupting tacrolimus treatment.

Impaired metabolism-secretion coupling in pancreatic beta-cells: role of determinants of mitochondrial ATP production

Glucose-induced insulin secretion from beta-cells is often impaired in diabetic condition and by exposure to diabetogenic pharmacological agents. In pancreatic beta-cells, intracellular glucose metabolism regulates exocytosis of insulin granules, according to metabolism-secretion coupling in which glucose-induced mitochondrial ATP production plays an essential role. Impaired glucose-induced insulin secretion often results from impaired glucose-induced ATP elevation in beta-cells. Mitochondrial ATP production is driven by the proton-motive force including mitochondrial membrane potential (DeltaPsi(m)) generated by the electron transport chain. These electrons are derived from reducing equivalents, generated in the Krebs cycle and transferred from cytosol by the shuttles. Here, roles of the determinants of mitochondrial ATP production in impaired glucose-induced insulin secretion are discussed. Cytosolic alkalization, H(+) leak in the inner membrane by uncoupler (e.g. free fatty acid exposure), decrease in the supply of electron donors including NADH and FADH(2) to the respiratory chain, and endogenous mitochondrial ROS (e.g. Na(+)/K(+)-ATPase inhibition) all reduce hyperpolarlization of DeltaPsi(m) and ATP production, causing decresed glucose-induced insulin release. The decrease in the supply of NADH and FADH(2) to the respiratory chain derives from impairments in glucose metabolism including glycolysis (e.g. MODY2 and exposure to NO) and the shuttles (e.g. diabetic state and exposure to ketone body).

Calcineurin inhibitors in pediatric renal transplant recipients

The calcineurin inhibitors, cyclosporine (ciclosporin) [microemulsion] and tacrolimus, are the principal immunosuppressants prescribed for adult and pediatric renal transplantation. For pediatric patients, both drugs should be dosed per body surface area, and pharmacokinetic monitoring is mandatory. While monitoring of the trough levels may suffice for tacrolimus, cyclosporine therapy that utilizes the microemulsion formulation requires additional monitoring (e.g. determination of 2-hour post-dose levels). In a well designed randomized study in children, as in studies in adults, there was no difference in short-term patient and graft survival with cyclosporine microemulsion and tacrolimus. However, tacrolimus was significantly more effective than cyclosporine microemulsion in preventing acute rejection after renal transplantation when used in conjunction with azathioprine and corticosteroids. With regard to long-term outcome, the difference in acute rejection episodes resulted in a better glomerular filtration rate at 1 year after transplantation and eventually in better graft survival 4 years after renal transplantation. Whether this difference persists when calcineurin inhibitors are used in combination with mycophenolate mofetil has not been determined. The prevalence of hypomagnesemia was higher in the tacrolimus group whereas hypertrichosis and gingival hyperplasia occurred more frequently in the cyclosporine group. In contrast with adults, the incidence of post-transplantation diabetes mellitus was not significantly different between tacrolimus- and cyclosporine-treated patients. There was also no difference with regard to post-transplantation lymphoproliferative disorder. Medication costs were similar, but in view of the lower rejection episodes and better long-term graft survival as well as the more favorable cosmetic side effect profile, tacrolimus may be preferable. The recommendation drawn from the available data is that both cyclosporine and tacrolimus can be used safely and effectively in children. We recommend that cyclosporine should be chosen when patients experience tacrolimus-related adverse events.

Influence of early posttransplantation prednisone and calcineurin inhibitor dosages on the incidence of new-onset diabetes

Risk for new-onset diabetes (NOD) after renal transplantation is higher with tacrolimus (Tac) than with cyclosporine (CsA), but the extent to which the diabetogenic effect of Tac is dosage dependent or steroid dependent remains uncertain. Patients who received a transplant between 1995 and 2002 were drawn from the United Network for Organ Sharing registry and prescription records and NOD diagnoses from Medicare claims, both provided by the United States Renal Data System. Patients were divided into six groups of steroid and Tac doses at 30 d after transplantation and referenced against CsA. Relative hazards of NOD with Cox proportional hazards regression were estimated incorporating propensity scores for Tac and nonimmunosuppressive factors related to NOD. A total of 8839 patients with valid immunosuppression records and without pretransplantation evidence of diabetes were included in the study. Unadjusted, cumulative, NOD incidence 1 yr after transplantation was 14.6% with CsA and 22.2% with Tac and at 3 yr after transplantation was 23.4% with CsA and 32.9% with Tac (P < 0.0001). Neither higher CsA nor higher steroid dosages were associated with NOD in CsA-treated patients. However, NOD hazard was significantly higher with Tac than with CsA in all six steroid/Tac dosing groups, including the cohort with the lowest dosages of Tac (dosage thresholds at 30 d after transplantation <0.12 mg/kg per d [mean 0.07 mg/kg per d] and steroids (<0.75 mg/kg per d; hazard ratio 1.28; 95% confidence interval 1.10 to 1.48; P = 0.0012). Whereas the incidence of NOD is greatest with high Tac dosages, the increased risk versus CsA is sustained with lower Tac dosages. Higher steroid dosages increase the early diabetogenic effect of Tac but not of CsA.

Tacrolimus and sirolimus cause insulin resistance in normal sprague dawley rats

BACKGROUND

Tacrolimus-sirolimus immunosuppression has improved islet graft survival but may affect islet function.

METHODS

We studied the effects of tacrolimus, sirolimus, or both in normal adult male Sprague Dawley rats. Glucose and insulin response to oral glucose load and pancreas pathology were evaluated after two weeks of daily tacrolimus (1-8 mg/kg/day), sirolimus (0.08-8 mg/kg/day), or low-dose sirolimus (0.08 mg/kg/day) plus tacrolimus (1 mg/kg/day) treatment compared to controls.

RESULTS

Tacrolimus and sirolimus each caused dose-dependent hyperglycemia with hyperinsulinemia in response to oral glucose compared to controls, suggesting insulin resistance. At the highest doses of sirolimus, fasting insulin concentrations were high and did not increase with oral glucose suggesting loss of first phase insulin release. The combination of low doses of tacrolimus and sirolimus, at concentrations used in clinical transplantation, resulted in hyperglycemia without hyperinsulinemia after oral glucose administration. The combination of tacrolimus and sirolimus decreased islet size, and increased islet apoptosis more than either medication alone, or controls.

CONCLUSIONS

In summary, short-term therapy with either tacrolimus or sirolimus causes insulin resistance in normal rats. Combination tacrolimus-sirolimus causes greater islet changes suggesting early islet failure.

Relative risk of new-onset diabetes during the first year after renal transplantation in patients receiving tacrolimus or cyclosporine immunosuppression

Clinical trials have consistently shown a higher incidence of new-onset diabetes mellitus with tacrolimus than cyclosporine. However, in protocol-driven studies steroid doses are comparable in both treatment arms, while in clinical practice steroid dose used in conjunction with tacrolimus or cyclosporine may differ. This retrospective study analysed renal transplant recipients without pre-existing diabetes receiving tacrolimus (n = 100) or cyclosporine (n = 100) for whom one-year follow-up data were available. Diabetes was defined as use of insulin or oral hypoglycemic agents; fasting glucose >6.9 mmol/L; or non-fasting glucose >11 mmol/L on three consecutive occasions. Tacrolimus-treated patients were significantly older than cyclosporine-treated patients (49 +/- 14 vs. 44 +/- 13 yr, p < 0.05) and received a significantly lower cumulative dose of corticosteroids over the first three months post-transplant (1284 +/- 379 vs. 1714 +/- 486 mg, p < 0.0001). At 3, 6, 9 and 12 months significantly more tacrolimus-treated patients had new-onset diabetes than cyclosporine- treated patients. At 12 months, 18 patients receiving tacrolimus and two receiving cyclosporine had diabetes (p < 0.0001). There was a clear relationship between age and incidence of new-onset diabetes at three months in the tacrolimus cohort. After stratifying patients by age group, the frequency of diabetes was significantly higher with tacrolimus than with cyclosporine in patients aged 40-60 yr [8/46 (17.4%) vs. 2/48 (4.2%), p < 0.05] and >60 yr [9/28 (32.1%) vs. 0/14 (0%), p < 0.05]. The mean tacrolimus trough level during the first three months was similar in patients with diabetes (13.1 +/- 2.3 ng/mL) or without diabetes (13.0 +/- 2.8 ng/mL, n.s.). These results indicate that new-onset diabetes is strongly and significantly associated with tacrolimus vs. cyclosporine in renal transplant recipients, even when steroid dosing is lower with tacrolimus.

Role of IL-2 and Helper T-Lymphocytes in Limiting Periapical Pathosis

The purpose of this study was to examine the role of IL-2 and helper T-lymphocytes in the development of periradicular lesions in rats. In control animals, periradicular lesions developed within 28 days following pulpal infection. Immunologically, some anti IL-2 and anti CD4-reactive helper T-lymphocytes infiltrated the periapical tissue at 14 days, and their numbers increased at 28 days. In experimental animals, tacrolimus (FK506) was injected every day to inhibit the IL-2 production by helper T-cells. Histologically, the pulpal necrosis and periradicular inflammation in tacrolimus-treated rats were more severe than those in the control rats. Furthermore, the areas of pulpal necrosis and periradicular lesion in the immunosuppressed rat were significantly greater than those in the normal ones. The numbers of IL-2- and CD4-positive cells in the lesion of the experimental rats were statistically lower than those of the control ones. These results show that the decrease in IL-2 might have promoted the development of periradicular lesions.

Tacrolimus suppresses glucose-induced insulin release from pancreatic islets by reducing glucokinase activity

Tacrolimus is widely used for immunosuppressant therapy, including various organ transplantations. One of its main side effects is hyperglycemia due to reduced insulin secretion, but the mechanism remains unknown. We have investigated the metabolic effects of tacrolimus on insulin secretion at a concentration that does not influence insulin content. Twenty-four-hour exposure to 3 nM tacrolimus reduced high glucose (16.7 mM)-induced insulin secretion (control 2.14 +/- 0.08 vs. tacrolimus 1.75 +/- 0.02 ng.islet(-1).30 min(-1), P < 0.01) without affecting insulin content. In dynamic experiments, insulin secretion and NAD(P)H fluorescence during a 20-min period after 10 min of high-glucose exposure were reduced in tacrolimus-treated islets. ATP content and glucose utilization of tacrolimus-treated islets in the presence of 16.7 mM glucose were less than in control (ATP content: control 9.69 +/- 0.99 vs. tacrolimus 6.52 +/- 0.40 pmol/islet, P < 0.01; glucose utilization: control 103.8 +/- 6.9 vs. tacrolimus 74.4 +/- 5.1 pmol.islet(-1).90 min(-1), P < 0.01). However, insulin release from tacrolimus-treated islets was similar to that from control islets in the presence of 16.7 mM alpha-ketoisocaproate, a mitochondrial fuel. Glucokinase activity, which determines glycolytic velocity, was reduced by tacrolimus treatment (control 65.3 +/- 3.4 vs. tacrolimus 49.9 +/- 2.8 pmol.islet(-1).60 min(-1), P < 0.01), whereas hexokinase activity was not affected. These results indicate that glucose-stimulated insulin release is decreased by chronic exposure to tacrolimus due to reduced ATP production and glycolysis derived from reduced glucokinase activity.

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.

New onset diabetes mellitus in patients receiving calcineurin inhibitors: a systematic review and meta-analysis

New onset diabetes mellitus (NODM) is a serious complication of transplantation. This meta-analysis evaluates the reported incidence of NODM after solid organ transplantation in patients receiving CNI treatment. Databases from January 1992 to April 2002 were searched. Fifty-six publications providing NODM incidence data were reviewed. Sixteen prospective, randomized comparative studies providing information on incidence of insulin-dependent diabetes mellitus (IDDM) were subjected to meta-analysis. New onset diabetes mellitus was reported in 13.4% of patients after solid organ transplantation, with a higher incidence in patients receiving tacrolimus than cyclosporine (16.6% vs. 9.8%). This trend was observed across renal, liver, heart and lung transplant groups. Meta-analysis of 16 studies included patients receiving either tacrolimus (n=1636) or cyclosporine (n=1407). The incidence of IDDM was significantly higher among tacrolimus-treated patients (10.4% vs. 4.5%, p<0.00001), an effect observed in renal (9.8% vs. 2.7% p<0.00001) and nonrenal (11.1% vs. 6.2%; p<0.003) groups, and among patients receiving equal doses of concomitant medication in both treatment arms (12.0% vs. 3.0%; p<0.00001). The reported incidence of NODM during the past decade was significantly higher among patients receiving tacrolimus than cyclosporine. These data provide a quantitative foundation for studies designed to reduce the rates of NODM following solid organ transplantation.

Additive Effects of Leflunomide and Tacrolimus in Prevention of Islet Xenograft Rejection

Leflunomide is a low molecular weight immunosuppressive drug which inhibits the enzymes dehydroorotate dehydrogenase and protein tyrosine kinase, both of which are important components in the immune response. As the mechanisms of action of leflunomide and tacrolimus are different, we postulated an additive or synergistic effect of the two drugs and investigated the effects of leflunomide alone, or in combination with a suboptimal dose of tacrolimus, on xenogeneic islet transplantation in a rat-to-mouse model. A total of 1200-1500 rat islets were transplanted under the left kidney capsule of streptozotocin-induced diabetic BALB/c mice. The median survival time (MST) of the untreated group was 6 days. Leflunomide at 5, 10 and 20 mg/kg/d administrated for 10 days significantly prolonged MST to 10, 16 and 20 days. A dose of tacrolimus (2 mg/kg/d) was associated with a graft survival of 9 (range 6-12) days; most grafts rejected during ongoing therapy. When tacrolimus (2 mg/kg/d) was combined with leflunomide (10 mg/kg/d), the survival time of the islet xenografts was increased further to 22 days, significantly longer than with leflunomide or tacrolimus alone. In summary, our findings demonstrate that leflunomide prolonged xenogeneic islet graft survival, and that its immunosuppressive effect was improved when combined with tacrolimus.

High incidence of tacrolimus-associated posttransplantation diabetes in the Korean renal allograft recipients according to American Diabetes Association criteria

OBJECTIVE

The incidence of posttransplantation diabetes mellitus (PTDM) has been reported to vary according to different study populations or different definitions. In this study, using American Diabetes Association criteria, the incidence and clinical characteristics of PTDM in Korean renal allograft recipients undergoing tacrolimus-based immunosuppression were examined.

RESEARCH DESIGN AND METHODS

A total of 21 patients taking tacrolimus as primary immunosuppressant were recruited and tested with a serial 75-g oral glucose tolerance test at 0, 1, 3, and 6 months after renal transplantation.

RESULTS

The cumulative incidence of PTDM was 52.4% at 1 month and 57.1% at 3 and 6 months. The baseline characteristics of the PTDM group were old age (especially >40 years), a high BMI, a high fasting glucose level, a high plasma insulin level, and increased insulin resistance. Among these parameters, old age was the only independent risk factor. The insulin secretory capacity in the PTDM group was maximally suppressed 3 months after transplantation. Thereafter, it was gradually restored along with dose reduction of tacrolimus.

CONCLUSIONS

Routine screening for PTDM is necessary in patients over 40 years of age who are undergoing a relatively higher dose tacrolimus therapy during the early course of postrenal transplantation.

Cardiovascular toxicities of immunosuppressive agents

Cardiovascular disease is one of the major causes of morbidity and mortality following solid organ transplantation. Many of the current immunosuppressive drugs are associated with an increase of one or more risk factors for the development of atherosclerosis. This review compares the mechanism by which individual immunosuppressive agents may impact on these risk factors and the differential contribution of cyclosporine, tacrolimus, mycophenolate, azathioprine, and Rapamycin to these individual risk factors. Attention to the potential cardiovascular toxicities of individual immunosuppressive agents may help design strategies for maintenance of immunosuppression tailored to individual patients.

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.

Posttransplantation diabetes mellitus in FK-506-treated renal transplant recipients: analysis of incidence and risk factors

BACKGROUND

The development of posttransplantation diabetes mellitus has a major impact on the quality of life and long-term outcome.

METHODS

One hundred thirty-nine patients without known glucose metabolism abnormalities and treated with FK-506, methylprednisolone, and mycophenolate mofetil/azathioprine were analyzed for incidence of and risk factors for developing impaired fasting glycemia (IFG) and diabetes mellitus (DM).

RESULTS

Using the American Diabetes Association criteria, 15% developed IFG and 32% developed DM in the first year after transplantation. High trough levels of FK-506 during the first month after transplantation (especially >15 ng/ml) and high body mass index (BMI) were significant risk factors for IFG or DM. Patients with (steroid-treated) acute rejections in addition to high trough levels of FK-506 were most prone to develop DM, whereas high BMI conferred risk of developing IFG. Patients with posttransplantation glycemic abnormalities also had higher levels of serum triglycerides at the time of transplantation, but they needed a lower dose of FK-506 to obtain higher trough levels of FK-506, suggesting metabolic differences already present before transplantation. The only risk factor retained for persistent IFG or DM beyond the first year was a higher number of trough levels of FK-506 >15 ng/ml during the first month after transplantation.

CONCLUSIONS

Induction with an FK-506 based immunosuppressive regimen resulted in a high incidence of glucose metabolism disorders in renal transplantation recipients. Higher trough levels of FK-506 during the first month, acute rejections, and higher BMI were the most obvious risk factors.

Tacrolimus, but not cyclosporine A, significantly increases expression of ICAM-1 and IFN-gamma in the NOD mouse

We studied the alterations of cytokines and ICAM-1 expression in the NOD mouse pancreas produced by the administration of Cyclosporine A (CY) and Tacrolimus (TA), two widely used immunosuppressive drugs. Results evidenced differences in the effects of these two drugs. In fact, during treatment and after withdrawal, CY-treated animals remained euglycemic, showed good islet cell preservation and had low levels of Th1 and Th2 cytokines; ICAM-1 positivity within the islets was also found to be relatively low. On the other hand, TA-treated animals had infiltrated islets containing numerous dendritic cells, adhesion molecule overexpression, increased IFN-gamma and ICAM-1 mRNA transcripts, and interestingly, high levels of circulating ICAM-1. However, even these animals remained euglycemic. These findings lead to the thought that these drugs may exert their effects in very different ways. Moreover, in TA-treated animals, the presence of an islet infiltrate containing numerous dendritic cells coupled with maintenance of euglycemia is suggestive for the involvement of immunosurveillance mechanisms. J. Cell. Biochem. Suppl. 36: 107-116, 2001.

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.

Modern immunosuppression

The current treatment of posttransplant lymphoproliferative disease (PTLD) includes prophylaxis at the time of transplant, decreasing or stopping immunosuppresion and initiation of antiviral therapy in patients with polymerase chain reaction or clinical evidence of PTLD, and judicial reintroduction of immunosuppression in patients who have cleared their PTLD and have begun to have rejection. The pharmacology, pharmacokinetics, notable side effects, and toxicities of the immunosuppressive agents are described in this article. At the conclusion of each section the author's current practice with these agents and treatment strategies are described.

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.

Effect of tacrolimus (FK506) and sirolimus (rapamycin) mono- and combination therapy in prolongation of renal allograft survival in the monkey

BACKGROUND

Our previous studies confirmed that tacrolimus (FK506) and sirolimus [rapamycin (RAPA)], in combination, are not antagonistic but are synergistic in the prolongation of heart and small bowel grafts in the rodent. The aim of this study was to confirm further the synergistic effect of combined FK506 and RAPA in the more clinically relevant model, kidney transplantation in monkeys.

METHODS

A total of 60 male Vervet monkeys were randomly assigned to 10 groups (n> or =5). Monkeys with renal allografts were treated with different doses of FK506 and/or RAPA orally for 60 days. Graft survival, body weight, clinical biochemistry determinations, oral glucose tolerance test, trough levels of the two drugs, and histopathology were investigated.

RESULTS

Low doses of FK506 (1 or 4 mg/kg) combined with RAPA (0.5 mg/kg) produced synergistic effect in the prolongation of renal graft survival [combination index (CI) = 0.292, 0.565]. There were no additive or synergistic drug-associated toxicities such as hyperglycemia, nephrotoxicity, and hyperlipidemia. There also was no pharmacological antagonism.

CONCLUSION

Concomitant therapy of low-dose (drug-optimal) FK506 and RAPA produced a synergistic effect in the prolongation of kidney allograft survival in Vervet monkeys without additive drug-associated toxicities.