Hypertriglyceridemia in renal transplant recipients treated with sirolimus

Sirolimus-induced Hypertriglyceridemia Leads to Acute Pancreatitis and Diabetic Ketoacidosis Post Stem Cell Transplant for Sickle Cell Disease

Sirolimus (mammalian target of rapamycin inhibitor) is a potent immunosuppressive agent, used in patients receiving hematopoietic stem cell transplant (HSCT) for Graft vs Host disease prophylaxis. Compared to calcineurin inhibitors, sirolimus has no neurotoxicity or nephrotoxicity, but sirolimus causes dose-dependent thrombocytopenia, leukopenia, delayed wound healing, hyperlipidemia, and hypertriglyceridemia. Here we report a case of acute pancreatitis and diabetic ketoacidosis in a patient with sickle cell disease post haploidentical family donor HSCT which was managed conservatively without plasmapheresis. Based on our review of the literature, this is the first reported case of developing acute pancreatitis as an adverse effect of sirolimus-induced hypertriglyceridemia leading to diabetic ketoacidosis in a recipient of HSCT.

Single Center Experience of Sirolimus Therapy in Head and Neck Low-flow Vascular Malformations

OBJECTIVE

Recently, studies have shown that sirolimus is clinically efficacious in the treatment of some low-flow vascular malformations (LFVM). This study aimed to assess the efficacy and safety of sirolimus in treating complex head and neck (H&N) LFVM that were challenging and/or refractory to standard treatment.

METHODS

Each patient had baseline and 6-months assessments consisting of clinical history and examination, quality of life (QoL) questionnaires, laboratory investigations, MRI and medical photography. Patients were followed up 1-week and then 1-monthly for 6-months. Wilcoxon signed-rank test was used to compare pre-and 6-months treatment in all 8 domains of RAND 36-Item Short Form Health Survey (SF-36), hospital anxiety and depression scale (HADS), and visual analog score for pain (VAS-P). P < 0.05 was considered significant.

RESULTS

Seven patients (median age 43 years, range 23-65 years) were recruited. Six patients completed the six-months course of therapy with 1 patient withdrawing due to intolerable side effects. All six patients reported reduction of swelling with and without other symptom improvement related to the vascular malformations while on treatment. However, at 1-month review after discontinuation of sirolimus, 5 patients reported return of initial symptoms. Overall, patients demonstrated an improvement in QoL six-months treatment but there was no statistical significance (P > 0.05) in all 8 domains of SF-36, HADS and VAS-P. Five patients demonstrated a minimum 10% decrease in lesion size six-months treatment (median 21%, range 13-40%). A Wilcoxon signed-rank test showed that sirolimus treatment did elicit a statistically significant change in lesion size in either direction (Z = -1.992, P = 0.046). The most common side effects found were dyslipidaemia (n-4) and mouth ulcers (n = 2).

CONCLUSION

In our preliminary experience, sirolimus is effective and safe in treating patients with complex H&N LFVM. This provides an alternative treatment where standard treatment is challenging and/or refractory.

Severe Hypertriglyceridemia Induced by Sirolimus Treated With Medical Management Without Plasmapheresis: A Case Report

Hypertriglyceridemia and hyperlipidemia are the most remarkable metabolic complications seen with long-term sirolimus therapy. We report the case of a 36-year-old woman status post bilateral lung transplantation on a maintenance immunosuppression regimen of sirolimus, tacrolimus, and prednisone who presented with status migrainosus, chest pain, abdominal discomfort, and triglyceride levels greater than 4425 mg/dL. In previously reported cases of severe hypertriglyceridemia that developed on maintenance sirolimus therapy, plasmapheresis has been utilized as an early strategy to rapidly lower triglycerides in order to minimize the risk of acute complications such as pancreatitis, but our case was managed medically without plasmapheresis. The most recent triglyceride was down to 520 mg/dL 2 months after discontinuation of sirolimus. We estimate the probability of this reaction to sirolimus as probable based on a score of 5 points on the Naranjo scale. This is the first case report to our knowledge that highlights the sole use of oral lipid-lowering drug agents to treat severe hypertriglyceridemia secondary to sirolimus without the use of plasmapheresis.

CONCLUSION

Sirolimus-induced severe hypertriglyceridemia can be managed with oral lipid-lowering agents without plasmapheresis. Clinician needs to be aware of the importance of baseline and regular triglyceride monitoring in patients on sirolimus.

Rapamycin Blocks Induction of the Thermogenic Program in White Adipose Tissue

Rapamycin extends life span in mice, yet paradoxically causes lipid dysregulation and glucose intolerance through mechanisms that remain incompletely understood. Whole-body energy balance can be influenced by beige/brite adipocytes, which are inducible by cold and other stimuli via β-adrenergic signaling in white adipose depots. Induction of beige adipocytes is considered a promising strategy to combat obesity because of their ability to metabolize glucose and lipids, dissipating the resulting energy as heat through uncoupling protein 1. Here, we report that rapamycin blocks the ability of β-adrenergic signaling to induce beige adipocytes and expression of thermogenic genes in white adipose depots. Rapamycin enhanced transcriptional negative feedback on the β3-adrenergic receptor. However, thermogenic gene expression remained impaired even when the receptor was bypassed with a cell-permeable cAMP analog, revealing the existence of a second inhibitory mechanism. Accordingly, rapamycin-treated mice are cold intolerant, failing to maintain body temperature and weight when shifted to 4°C. Adipocyte-specific deletion of the mTORC1 subunit Raptor recapitulated the block in β-adrenergic signaling. Our findings demonstrate a positive role for mTORC1 in the recruitment of beige adipocytes and suggest that inhibition of β-adrenergic signaling by rapamycin may contribute to its physiological effects.

Rapamycin impairs HPD-induced beneficial effects on glucose homeostasis

BACKGROUND AND PURPOSE

Rapamycin, which is used clinically to treat graft rejection, has also been proposed to have an effect on metabolic syndrome; however, very little information is available on its effects in lean animals/humans. The purpose of this study was to characterize further the effects of the continuous use of rapamycin on glucose homeostasis in lean C57BL6/J mice.

EXPERIMENTAL APPROACH

Mice were fed a high-protein diet (HPD) for 12 weeks to develop a lean model and then were treated daily with rapamycin for 5 weeks while remaining on a HPD. Metabolic parameters, endocrine profiles, glucose tolerance tests, insulin sensitivity index, the expression of the glucose transporter GLUT4 and chromium distribution were measured in vivo.

KEY RESULTS

Lower body weight gain as well as a decreased caloric intake, fat pads, fatty liver scores, adipocyte size and glucose tolerance test values were observed in HPD-fed mice compared with mice fed a high-fat or standard diet. Despite these beneficial effects, rapamycin-treated lean mice showed greater glucose intolerance, reduced insulin sensitivity, lower muscle GLUT4 expression and changes in chromium levels in tissues even with high insulin levels.

CONCLUSION AND IMPLICATIONS

Our findings demonstrate that continuous rapamycin administration may lead to the development of diabetes syndrome, as it was found to induce hyperglycaemia and glucose intolerance in a lean animal model.

Inhibition of Adipogenesis by Oligonol through Akt-mTOR Inhibition in 3T3-L1 Adipocytes

Polyphenols have recently become an important focus of study in obesity research. Oligonol is an oligomerized polyphenol, typically comprised of catechin-type polyphenols from a variety of fruits, which has been found to exhibit better bioavailability and bioreactivity than natural polyphenol compounds. Here, we demonstrated that Oligonol inhibits 3T3-L1 adipocyte differentiation by reducing adipogenic gene expression. During adipogenesis, Oligonol downregulated the mRNA levels of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding proteins α (C/EBPα), and δ (C/EBPδ) in a dose-dependent manner and the expression of genes involved in lipid biosynthesis. The antiadipogenic effect of Oligonol appears to originate from its ability to inhibit the Akt and mammalian target of rapamycin (mTOR) signaling pathway by diminishing the phosphorylation of ribosomal protein S6 kinase (p70S6K), a downstream target of mTOR and forkhead box protein O1 (Foxo1). These results suggest that Oligonol may be a potent regulator of obesity by repressing major adipogenic genes through inhibition of the Akt signaling pathway, which induces the inhibition of lipid accumulation, ultimately inhibiting adipogenesis.

PPARγ activation attenuates glucose intolerance induced by mTOR inhibition with rapamycin in rats

mTOR inhibition with rapamycin induces a diabetes-like syndrome characterized by severe glucose intolerance, hyperinsulinemia, and hypertriglyceridemia, which is due to increased hepatic glucose production as well as reduced skeletal muscle glucose uptake and adipose tissue PPARγ activity. Herein, we tested the hypothesis that pharmacological PPARγ activation attenuates the diabetes-like syndrome associated with chronic mTOR inhibition. Rats treated with the mTOR inhibitor rapamycin (2 mg·kg(-1)·day(-1)) in combination or not with the PPARγ ligand rosiglitazone (15 mg·kg(-1)·day(-1)) for 15 days were evaluated for insulin secretion, glucose, insulin, and pyruvate tolerance, skeletal muscle and adipose tissue glucose uptake, and insulin signaling. Rosiglitazone corrected fasting hyperglycemia, attenuated the glucose and insulin intolerances, and abolished the increase in fasting plasma insulin and C-peptide levels induced by rapamycin. Surprisingly, rosiglitazone markedly increased the plasma insulin and C-peptide responses to refeeding in rapamycin-treated rats. Furthermore, rosiglitazone partially attenuated rapamycin-induced gluconeogenesis, as evidenced by the improved pyruvate tolerance and reduced mRNA levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Rosiglitazone also restored insulin's ability to stimulate glucose uptake and its incorporation into glycogen in skeletal muscle of rapamycin-treated rats, which was associated with normalization of Akt Ser(473) phosphorylation. However, the rapamycin-mediated impairments of adipose tissue glucose uptake and incorporation into triacylglycerol were unaffected by rosiglitazone. Our findings indicate that PPARγ activation ameliorates some of the disturbances in glucose homeostasis and insulin action associated with chronic rapamycin treatment by reducing gluconeogenesis and insulin secretion and restoring muscle insulin signaling and glucose uptake.

Carbamazepine suppresses calpain-mediated autophagy impairment after ischemia/reperfusion in mouse livers

Onset of the mitochondrial permeability transition (MPT) plays a causative role in ischemia/reperfusion (I/R) injury. Current therapeutic strategies for reducing reperfusion injury remain disappointing. Autophagy is a lysosome-mediated, catabolic process that timely eliminates abnormal or damaged cellular constituents and organelles such as dysfunctional mitochondria. I/R induces calcium overloading and calpain activation, leading to degradation of key autophagy-related proteins (Atg). Carbamazepine (CBZ), an FDA-approved anticonvulsant drug, has recently been reported to increase autophagy. We investigated the effects of CBZ on hepatic I/R injury. Hepatocytes and livers from male C57BL/6 mice were subjected to simulated in vitro, as well as in vivo I/R, respectively. Cell death, intracellular calcium, calpain activity, changes in autophagy-related proteins (Atg), autophagic flux, MPT and mitochondrial membrane potential after I/R were analyzed in the presence and absence of 20 μM CBZ. CBZ significantly increased hepatocyte viability after reperfusion. Confocal microscopy revealed that CBZ prevented calcium overloading, the onset of the MPT and mitochondrial depolarization. Immunoblotting and fluorometric analysis showed that CBZ blocked calpain activation, depletion of Atg7 and Beclin-1 and loss of autophagic flux after reperfusion. Intravital multiphoton imaging of anesthetized mice demonstrated that CBZ substantially reversed autophagic defects and mitochondrial dysfunction after I/R in vivo. In conclusion, CBZ prevents calcium overloading and calpain activation, which, in turn, suppresses Atg7 and Beclin-1 depletion, defective autophagy, onset of the MPT and cell death after I/R.

Hypertriglyceridemia in patients with metastatic breast cancer and treatment with capecitabine

Several reports have described hypertriglyceridemia (HTG) in cancer patients, including breast cancer patients treated with capecitabine (CAP). However, the exact range of HTG in patients with metastatic breast cancer (MBC) treated with CAP has clearly not been defined. A retrospective analysis on 54 patients with MBC treated with CAP longer than 2 months was conducted. HTG was defined as triglyceride blood level above 150 mg/dl. Baseline data included age, body mass index (BMI), tumour characteristics, treatment duration, concomitant treatment with lapatinib, diagnosis of dyslipidemia, and diabetes mellitus, as well as antihyperlipidemic therapy. Clinically significant HTG (triglycerides >300 mg/dl) was found in 4/54 (7%) of patients. Post-treatment HTG was associated only with concomitant treatment with lapatinib (P<0·01). Three of the patients had dyslipidemia before treatment with CAP, and one patient also had diabetes-mellitus. No HTG-related complications occurred. Clinically significant HTG in MBC patients treated with CAP may be associated with pre-existing risk factors, such as dyslipidemia or diabetes-mellitus.

Rapamycin selectively alters serum chemistry in diabetic mice

The study was undertaken to explore the effect of rapamycin, an anti-inflammatory agent, on the metabolic profile of type 2 diabetic mice. Seven-month-old diabetic db/db mice and their lean littermate non-diabetic controls (db/m) were randomized to receive control chow or chow mixed with rapamycin (2.24 mg/kg/day) (each group n =20, males and females) for 4 months and sacrificed. Serum samples were analyzed for the measurement of glucose, creatinine, blood urea nitrogen (BUN), alkaline phosphatase (ALP), alanine aminotransferase (ALT), total cholesterol, total triglyceride, and total protein, using the automated dry chemistry analysis. Rapamycin elevated serum glucose in female diabetic mice. Serum creatinine tended to be higher in diabetic mice but was not affected by rapamycin; there was no difference in BUN levels among the groups. Serum ALP was elevated in diabetic mice and rapamycin lowered it only in female diabetic mice; serum ALT levels were increased in female diabetic mice, unaffected by rapamycin. Serum total protein was elevated in diabetic mice of both genders but was not affected by rapamycin. Diabetic mice from both genders had elevated serum cholesterol and triglycerides; rapamycin did not affect serum cholesterol but decreased serum total triglycerides in male diabetic mice. We conclude that rapamycin elicits complex metabolic responses in aging diabetic mice, worsening hyperglycemia in females but improving ALP in female diabetic and total triglycerides in male diabetic mice, respectively. The metabolic effects of rapamycin should be considered while performing studies with rapamycin in mice.

Major involvement of mTOR in the PPARγ-induced stimulation of adipose tissue lipid uptake and fat accretion

Evidence points to a role of the mammalian target of rapamycin (mTOR) signaling pathway as a regulator of adiposity, yet its involvement as a mediator of the positive actions of peroxisome proliferator-activated receptor (PPAR)γ agonism on lipemia, fat accretion, lipid uptake, and its major determinant lipoprotein lipase (LPL) remains to be elucidated. Herein we evaluated the plasma lipid profile, triacylglycerol (TAG) secretion rates, and adipose tissue LPL-dependent lipid uptake, LPL expression/activity, and expression profile of other lipid metabolism genes in rats treated with the PPARγ agonist rosiglitazone (15 mg/kg/day) in combination or not with the mTOR inhibitor rapamycin (2 mg/kg/day) for 15 days. Rosiglitazone stimulated adipose tissue mTOR complex 1 and AMPK and induced TAG-derived lipid uptake (136%), LPL mRNA/activity (2- to 6-fold), and fat accretion in subcutaneous (but not visceral) white adipose tissue (WAT; 50%) and in brown adipose tissue (BAT; 266%). Chronic mTOR inhibition attenuated the upregulation of lipid uptake, LPL expression/activity, and fat accretion induced by PPARγ activation in both subcutaneous WAT and BAT, which resulted in hyperlipidemia. In contrast, rapamycin did not affect most of the other WAT lipogenic genes upregulated by rosiglitazone. Together these findings demonstrate that mTOR is a major regulator of adipose tissue LPL-mediated lipid uptake and a critical mediator of the hypolipidemic and lipogenic actions of PPARγ activation.

Unusual pattern of dyslipidemia in children receiving steroid minimization immunosuppression after renal transplantation

BACKGROUND AND OBJECTIVES

Corticosteroids are an important contributor to posttransplant hyperlipidemia. Since 2004, we have used a steroid minimization immunosuppression protocol. This study investigated the effect of steroid minimization on dyslipidemia in pediatric renal allograft recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Children (<18 years) who underwent renal transplants at our center from January 2001 to January 2008 were studied. Data analyzed included age, gender, race, body mass index, cholesterol, triglyceride, LDL cholesterol, HDL cholesterol, and steroid dose. Data between the cohorts receiving maintenance steroids and steroid-minimization were compared using multivariable analyses. The primary outcome measures were the prevalence of, and the effect of steroid use, on dyslipidemia.

RESULTS

Twenty-nine patients were studied. Sixteen were receiving maintenance steroids, and 13 were on a steroid minimization regimen. Mixed effects analysis of covariance models demonstrated that at 1 month, children receiving maintenance steroids had higher cholesterol compared with the steroid minimization group. Statistically significant differences in total cholesterol were not seen at other time points. Similar findings were noted for the LDL cholesterol, LDL/HDL, and cholesterol/HDL ratios. At 1 month, the serum HDL cholesterol was substantially lower in the steroid minimization group. Differences in the HDL cholesterol levels remained significant throughout the first year.

CONCLUSIONS

Steroid use is a significant independent risk factor for hypercholesterolemia during the first post-transplant month. The significance of lower HDL cholesterol among patients receiving steroid minimization needs further study and may be cause for concern.

Rapamycin protects against high fat diet-induced obesity in C57BL/6J mice

Rapamycin (RAPA), an immunosuprpressive drug used extensively to prevent graft rejection in transplant patients, has been reported to inhibit adipogenesis in vitro. In this study, we investigated the anti-obesity effects of RAPA in C57BL/6J mice on a high-fat diet (HFD). Mice treated with RAPA (2 mg/kg per week for 16 weeks) had reduced body weight and epididymal fat pads/body weight, reduced daily food efficiency, and lower serum leptin and insulin levels compared with the HFD control mice. However, RAPA-treated mice were hyperphagic, demonstrating an increase in food intake. Dissection of RAPA-treated mice revealed a marked reduction in fatty liver scores, average fat cell size, and percentage of large adipocytes of retroperitoneal and epididymal white adipose tissue (RWAT and EWAT), compared to the HFD control mice. These results suggest that RAPA prevented the effect of the high-fat diet on the rate of accretion in body weight via reducing lipid accumulation, despite greater food intake. It is likely that RAPA may serve as a potential strategy for body weight control and/or anti-obesity therapy.

Sirolimus for angiomyolipoma in tuberous sclerosis complex or lymphangioleiomyomatosis

BACKGROUND

Angiomyolipomas in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis are associated with mutations in tuberous sclerosis genes resulting in constitutive activation of the mammalian target of rapamycin (mTOR). The drug sirolimus suppresses mTOR signaling.

METHODS

We conducted a 24-month, nonrandomized, open-label trial to determine whether sirolimus reduces the angiomyolipoma volume in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis. Sirolimus was administered for the first 12 months only. Serial magnetic resonance imaging of angiomyolipomas and brain lesions, computed tomography of lung cysts, and pulmonary-function tests were performed.

RESULTS

Of the 25 patients enrolled, 20 completed the 12-month evaluation, and 18 completed the 24-month evaluation. The mean (+/-SD) angiomyolipoma volume at 12 months was 53.2+/-26.6% of the baseline value (P<0.001) and at 24 months was 85.9+/-28.5% of the baseline value (P=0.005). At 24 months, five patients had a persistent reduction in the angiomyolipoma volume of 30% or more. During the period of sirolimus therapy, among patients with lymphangioleiomyomatosis, the mean forced expiratory volume in 1 second (FEV1) increased by 118+/-330 ml (P=0.06), the forced vital capacity (FVC) increased by 390+/-570 ml (P<0.001), and the residual volume decreased by 439+/-493 ml (P=0.02), as compared with baseline values. One year after sirolimus was discontinued, the FEV1 was 62+/-411 ml above the baseline value, the FVC was 346+/-712 ml above the baseline value, and the residual volume was 333+/-570 ml below the baseline value; cerebral lesions were unchanged. Five patients had six serious adverse events while receiving sirolimus, including diarrhea, pyelonephritis, stomatitis, and respiratory infections.

CONCLUSIONS

Angiomyolipomas regressed somewhat during sirolimus therapy but tended to increase in volume after the therapy was stopped. Some patients with lymphangioleiomyomatosis had improvement in spirometric measurements and gas trapping that persisted after treatment. Suppression of mTOR signaling might constitute an ameliorative treatment in patients with the tuberous sclerosis complex or sporadic lymphangioleiomyomatosis. (ClinicalTrials.gov number, NCT00457808.)

The effects of sirolimus on wound healing in dermatologic surgery

BACKGROUND

Sirolimus, a TOR (target of rapamycin)-binding immunosuppressant, has been associated with wound healing complications; however, its effects have not been documented in dermatologic surgery.

OBJECTIVE

The objective was to determine the effect of sirolimus on wound healing in dermatologic surgery.

METHODS AND MATERIALS

Databases at Mayo Clinic were queried for organ transplant recipients undergoing dermatologic surgery. Medical records were reviewed retrospectively, and telephone interviews were conducted. Patients receiving sirolimus were compared with patients not receiving sirolimus.

RESULTS

Postoperative infections occurred in 19.2% of the sirolimus group (n=26) and 5.4% of the controls (n=37; p=.11; odds ratio [OR], 4.2; 95% confidence interval [CI], 0.7-23.4). The incidence of wound dehiscence was greater in the sirolimus group (7.7% vs. 0%; p=.17; OR, 7.7; 95% CI, 0.4-166.3).

CONCLUSION

No significantly increased risk of wound complications was found in organ transplant recipients receiving sirolimus while undergoing dermatologic surgery. However, this study was retrospective and had a small sample size. A larger study is necessary for corroboration.

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.

The mammalian target of rapamycin regulates lipid metabolism in primary cultures of rat hepatocytes

The mammalian target of rapamycin (mTOR) is a conserved serine-threonine kinase that regulates cell growth and metabolism in response to nutrient signals. However, the specific involvement of mTOR in regulation of energy metabolism is poorly understood. To determine if signaling via mTOR might be directly involved in regulation of fatty acid metabolism in hepatocytes, we performed studies with rapamycin, a specific inhibitor of mTOR. Rapamycin-mediated inhibition of mTOR (18-48 hours) increased oxidation of exogenous fatty acids (46%-100%, respectively). In addition, esterification of exogenous fatty acids and de novo lipid synthesis were reduced (40%-60%, respectively). Consistent with inhibition of lipogenic pathways, rapamycin decreased expression of genes encoding acetyl-coenzyme A carboxylase I and mitochondrial glycerol phosphate acyltransferase. Non-insulin-dependent glucose transport and glycogen synthesis were decreased by 20% to 30%, whereas glucose utilization was unaffected by rapamycin. The data suggest that the hyperlipidemia observed with the drug in vivo is likely not the result of enhanced hepatic synthesis, but rather of delayed peripheral clearance. However, these results are consistent with the idea that mTOR may play a significant role, not only in "energy sensing," but also in regulation of energy production through profound effects on hepatic fatty acid metabolism.

Effect of Sirolimus Treatment on Gene Expression in Renal Transplant Patients

BACKGROUND

Sirolimus (rapamycin), a strong immunosuppressive agent, is administered to renal transplant patients to prevent rejection. The rapamycin signaling pathway [mammalian target of rapamycin (mTOR)] has been implicated in transcriptional regulation.

METHODS

We used high-density oligonucleotide human microarrays to evaluate the effects of sirolimus treatment on gene expression in renal transplant patients. With this technique, we assessed selected genes in the rapamycin signaling, immunosuppression, insulin signaling, and triglyceride metabolism pathways.

RESULTS

Filtered data from both treated and untreated patients showed variability within each group. Significant fold changes were observed in genes from the immunosuppression and insulin signaling pathways but not the rapamycin signaling pathway. The triglyceride metabolism pathway revealed a significant reduction of message levels in lipoprotein and triglyceride synthesis genes.

CONCLUSIONS

These results show that using oligonucleotide microarrays to analyze the effects of sirolimus treatment in patients with renal transplant is an effective way to evaluate gene message levels in multiple pathways.

Rapamycin-mediated inhibition of mammalian target of rapamycin in skeletal muscle cells reduces glucose utilization and increases fatty acid oxidation

The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays an important role in cell growth and metabolism. mTOR has been postulated as a nutrient sensor, but its role in the regulation of fatty acid and glucose metabolism is poorly understood. For the first time, we show that mTOR inhibition in skeletal muscle cells has pronounced effects on intermediary metabolism. Rapamycin, a uniquely specific mTOR inhibitor with clinical applications, increased fatty acid oxidation by 60% accompanied by increased activities of carnitine palmitoyltransferases I and II, the former believed to be the primary intracellular regulatory enzyme of the fatty acid oxidation pathway. Furthermore, glucose transport capacity, glycogen synthesis, and glycolysis were reduced by approximately 40% under the same conditions. In addition, in the presence of rapamycin, hyperinsulinemic conditions (100 nmol/L insulin, 24 hours) were unable to suppress fatty acid oxidation in L6 myotubes. Rapamycin treatment also decreased baseline phosphorylation of mTOR residues S2448 and S2481 by 30% and almost completely abolished p70 S6 kinase phosphorylation. These results show that rapamycin causes a metabolic shift from glucose utilization to fatty acid oxidation in model muscle cells in the presence of nutrient abundance and underline the importance of mTOR as a key regulator in glucose and lipid metabolism.

The Preoperative Evaluation of the Transplanted Patient for Nontransplant Surgery

With the improved success of solid-organ transplantation, there has been an increased willingness to transplant individuals previously felt to be unsuitable for such procedures. Factors such as age and various medical comorbidities are no longer considered contraindications to transplantation, and hence, an increasing number of recipients may require medical care not specifically related to the transplant. After transplantation, many of these patients may require elective or emergent surgery, making it important for all surgeons to be familiar with the factors that may influence surgical outcomes in this population, asa well asa factors that affect postoperative care. Most transplant centres use a team approach to manage these complex patients, relying on medical professionals experienced in their care and management. Close interaction with the transplant team is likely the single most important step in preparing the transplanted patient for surgery and managing their postoperative care.

Rapamycin, an mTOR inhibitor, disrupts triglyceride metabolism in guinea pigs

This study was designed to define some of the mechanisms by which rapamycin (RAPA), an mTOR inhibitor, induces hypertriglyceridemia when used as an immunosuppressive or antiproliferative agent and to determine whether low doses result in less undesirable side effects. Thirty male guinea pigs (n=10 per group) were randomly assigned to control (no RAPA), low-RAPA (0.08 mg/d), or high-RAPA (0.85 mg/d) treatment for 3 weeks. Rapamycin treatment resulted in more than a 2-fold increase in plasma triglycerides (TG) (P<.01), whereas no differences were observed in plasma cholesterol between RAPA and control groups. Low-RAPA treatment resulted in lower concentrations of cholesterol in the aorta (28.6%) and lower hepatic acyl-CoA cholesteryl acyltransferase activity compared to control and high-RAPA groups (P<.01). In addition, acyl-CoA cholesteryl acyltransferase activity was positively correlated with aortic cholesterol (r=0.43, P<.05). In contrast, aortic TG concentrations were higher in RAPA-treated guinea pigs than in control (P<.01). Very low density lipoprotein and low-density lipoprotein particles isolated from guinea pigs treated with RAPA were larger in size and contained more TG molecules than particles from control animals. Interestingly, plasma free fatty acids and fasting plasma glucose were 65% and 72% higher in the high-RAPA group than in control (P<.01). Tumor necrosis factor-alpha concentrations in the aorta were 3.6- and 10.4-fold higher in the low-RAPA and high-RAPA groups than in control guinea pigs (P<.01). These results suggest that RAPA interferes with TG metabolism by altering the insulin signaling pathway, inducing increased secretion of very low density lipoprotein and promoting deposition of TG in the aorta. Low RAPA was found to decrease cholesterol accumulation in tissue (liver and aorta) compared to high RAPA, suggesting that lower doses could be less detrimental to transplant patients.

Should we quantify insulin resistance in patients with renal disease?

Cardiovascular disease is a major cause of morbidity and mortality in dialysis patients. Vascular disease develops before the initiation of dialysis, and it is now recognized that chronic kidney disease (CKD) is an independent risk factor for cardiovascular disease. Death from cardiovascular disease is a more common endpoint of CKD than progression to dialysis. There are multiple mechanisms that contribute to the increased vascular risk of CKD, one of which is the presence of insulin resistance (IR). CKD is characterised by many features of the metabolic syndrome, and features of IR are also observed in dialysis and transplant patients. IR may be quantified by several different methods. One such method is homeostatic model assessment (HOMA) technique, which derives a measurement of IR from fasting plasma glucose and insulin concentrations. The HOMA index has been demonstrated to be an independent predictor of survival in dialysis patients. CKD is characterised by a chronic inflammatory response and abnormalities in the production and regulation of adipose tissue derived proteins, which may contribute to the development of IR. There are a range of interventions including diet and exercise programmes or medications that may influence IR; however, the impact of these interventions in the context of CKD has not been systematically evaluated.

Benefit-Risk Assessment of Sirolimus in Renal Transplantation

Sirolimus (rapamycin) is a macrocyclic lactone isolated from a strain of Streptomyces hygroscopicus that inhibits the mammalian target of rapamycin (mTOR)-mediated signal-transduction pathways, resulting in the arrest of cell cycle of various cell types, including T- and B-lymphocytes. Sirolimus has been demonstrated to prolong graft survival in various animal models of transplantation, ranging from rodents to primates for both heterotopic, as well as orthotopic organ grafting, bone marrow transplantation and islet cell grafting. In human clinical renal transplantation, sirolimus in combination with ciclosporin (cyclosporine) efficiently reduces the incidence of acute allograft rejection. Because of the synergistic effect of sirolimus on ciclosporin-induced nephrotoxicity, a prolonged combination of the two drugs inevitably leads to progressive irreversible renal allograft damage. Early elimination of calcineurin inhibitor therapy or complete avoidance of the latter by using sirolimus therapy is the optimal strategy for this drug. Prospective randomised phase II and III clinical studies have confirmed this approach, at least for recipients with a low to moderate immunological risk. For patients with a high immunological risk or recipients exposed to delayed graft function, sirolimus might not constitute the best therapeutic choice--despite its ability to enable calcineurin inhibitor sparing in the latter situation--because of its anti-proliferative effects on recovering renal tubular cells. Whether lower doses of sirolimus or a combination with a reduced dose of tacrolimus would be advantageous in these high risk situations remains to be determined. Clinically relevant adverse effects of sirolimus that require a specific therapeutic response or can potentially influence short- and long-term patient morbidity and mortality as well as graft survival include hypercholesterolaemia, hypertriglyceridaemia, infectious and non-infectious pneumonia, anaemia, lymphocele formation and impaired wound healing. These drug-related adverse effects are important determinants in the choice of a tailor-made immunosuppressive drug regimen that complies with the individual patient risk profile. Equally important in the latter decision is the lack of severe intrinsic nephrotoxicity associated with sirolimus and its advantageous effects on arterial hypertension, post-transplantation diabetes mellitus and esthetic changes induced by calcineurin inhibitors. Mild and transient thrombocytopenia, leukopenia, gastrointestinal adverse effects and mucosal ulcerations are all minor complications of sirolimus therapy that have less impact on the decision for choosing this drug as the basis for tailor-made immunosuppressive therapy. It is clear that sirolimus has gained a proper place in the present-day immunosuppressive armament used in renal transplantation and will contribute to the development of a tailor-made immunosuppressive therapy aimed at fulfilling the requirements outlined by the individual patient profile.

Sirolimus-Associated Hepatotoxicity in Liver Transplantation

BACKGROUND

Sirolimus is an immunosuppressant that exerts anti-rejection activity by inhibiting T-cell activity and is used to treat chronic rejection and calcineurin-related nephrotoxicity. Unlike tacrolimus and cyclosporine, it has no effect on calcineurin activity in liver transplant recipients.

OBJECTIVE

To report correlates of survival outcomes in a series of patients with putative sirolimus-related hepatotoxicity after liver transplant.

METHODS

We retrospectively reviewed the medical records of patients who underwent a liver transplant for chronic hepatitis C virus (HCV) and who received sirolimus immunosuppressive therapy between November 2000 and November 2003. Extracted data included sirolimus serum concentrations, frequency of sirolimus-related adverse effects, drug-related clinical hepatitis, and survival outcomes.

RESULTS

Ten patients were found to have been treated with sirolimus for either renal insufficiency (n = 6) or chronic rejection (n = 4). Six patients had liver biopsies, while the remaining 4 patients were clinically diagnosed with rejection. Two of the 6 patients demonstrated changes consistent with sinusoidal congestion and one with eosinophilia, consistent with an allergic drug reaction. HCV viral load increased slightly, from 600 000 to 700 000 IU/mL. Mean baseline transaminase levels were 45 IU/L for aspartate aminotransferase and 50 IU/L for alanine aminotransferase, with peak levels of 210 and 180 IU/L, respectively. The time to transaminase increase was a mean of 21 days when sirolimus was added, with resolution within 27 days (mean) after its discontinuation. No changes were evident in antiviral therapy. Combination sirolimus and tacrolimus concentrations were maintained at >10 ng/mL; average monotherapy with sirolimus was 12 ng/mL, and average time on therapy was 25 weeks.

CONCLUSIONS

Sirolimus-related hepatotoxicity is an important complication after liver transplant. Immediate recognition is critical to avoid confusion with other causes of abnormal serum aminotransferases after liver transplant, and discontinuation of the drug may be required.

A Retrospective Review of Liver Transplant Patients Treated with Sirolimus from a Single Center: An Analysis of Sirolimus-Related Complications

BACKGROUND

Sirolimus (SRL) is a powerful immunosuppressant used primarily in calcineurin inhibitors (CNI)-related nephrotoxicity. However, reports of drug-related side effects are increasing. The aim of our report is to review the frequency and timing of these complications within our transplant patient population.

METHODS

We retrospectively reviewed the medical records of liver-transplanted patients treated with sirolimus between November 1998 and April 2002. The data collected included SRL serum levels, frequency of reported and documented SRL-related side effects, and survival outcomes. Statistical evaluation included Pearson chi-square and the Fisher's exact tests.

RESULTS

Overall, 205 patients were identified, with 30 patients removed from the analysis for different reasons. Of the remaining 175 patients, 91 (52%) patients developed a complication other than an increase in serum triglycerides and/or cholesterol. The most frequent complications were: bilateral lower extremity edema (57.1%), dermatitis (25.3%), oral ulcers (24.2%), joint pain (23.0%), pleural effusion (16.5%) and increase in abdominal girth (9.9%). Other complications included: generalized edema (5.5%), pericardial effusion (5.5%), facial edema (2.2%), and upper extremity edema (1.3%). In addition, we reported two cases of hepatic artery thrombosis, one case of wound dehiscence with evisceration that required surgical repair, and one case of skin cancer. Interestingly, we found that a previous history of myocardial ischemia correlates with the development of SRL side effects.

CONCLUSIONS

SRL is a powerful immunosuppressant but not devoid of side effects. These results have elevated our level of suspicion when instituting SRL and may help with early recognition and prevention of drug related complications.

Sirolimus-induced hyperlipidaemia in liver transplant recipients is not dose-dependent

BACKGROUND

Sirolimus is a potent immunosuppressive medication that acts by inhibiting T-cell proliferation. It has been used in kidney transplantation because of its lack of nephrotoxicity. It is now being investigated in liver transplantation, but there are concerns about safety and long-term side effects such as dyslipidaemia. Hypertriglyceridaemia is a common adverse event seen with sirolimus use, and often does not respond to dose reduction or anti-lipemic drugs.

METHOD

We report six patients who have developed significant hyperlipidaemia while receiving sirolimus, in spite of therapeutic trough levels.

CONCLUSION

All six patients showed either resolution or improvement in lipid levels with discontinuation of sirolimus.

Continued superior outcomes with modification and lengthened follow-up of a steroid-avoidance pilot with extended daclizumab induction in pediatric renal transplantation1

BACKGROUND

Corticosteroids have been invariant transplant immunosuppressives with numerous adverse effects. We previously reported 6-month results in 10 patients using extended daclizumab induction to safely eliminate steroid use in pediatric renal transplantation. This expanded pilot series discusses immunosuppression dosing modification to further minimize drug toxicity without sacrificing regimen efficacy.

METHODS

Fifty-seven pediatric renal transplant recipients were enrolled in the pilot steroid-free protocol. Extended daclizumab induction, tacrolimus, and mycophenolate mofetil (MMF) were intended maintenance drugs. Fourteen patients were equal to or younger than 5 years, and 43 patients were older than 5 years of age at transplantation. There were seven protocol breaks. Study patients underwent serial protocol transplant biopsies (n=246), and serum daclizumab and mycophenolic acid (MPA) trough levels were evaluated. In this efficacy study, controls were 50 historical-matched steroid-based children receiving tacrolimus with 100% 2-year graft survival and without delayed graft function.

RESULTS

Mean follow-up was 20 (range, 4.5-41) months with 98% overall graft and patient survival. At 1 year of analysis, steroid-free recipients showed significant improvements for clinical acute rejection (8%), graft function, hypertension, and growth, without increased infectious complications. Leukopenia, anemia, and allograft nephrotoxicity were addressed by solely decreasing MMF and tacrolimus dosing and/or by replacing MMF with sirolimus, without increasing acute rejection. Early daclizumab levels of more than 5 microg/mL were observed for the first time in children of all ages.

CONCLUSIONS

Pediatric renal transplantation is safe without steroids. Daclizumab first-dose doubling and extended use for 6 months replaces steroids effectively without evidence of overimmunosuppression and may be the pivotal cause for the reduced acute rejection seen in this trial. This pilot study provides preliminary data to test this protocol in a prospective, multicenter randomized study.

Ten years of sirolimus therapy in orthotopic liver transplant recipients

BACKGROUND

Sirolimus therapy has been used in orthotopic liver transplant (OLT) recipients diagnosed with a variety of diseases; chronic graft rejection (CR), calcineurin associated renal toxicity, preemptive immune suppression, calcineurin related neurotoxicity, preemptive therapy in transplant recipients with history of hepatocellular carcinoma, and steroid resistant allograft rejection.

METHODS

A search for the medical literature and experiences involving sirolimus was done.

RESULTS

Several animal and human reports evaluating the use sirolimus in liver transplant recipients are found and discussed.

CONCLUSION

Sirolimus has been used for multitude of indications, primarily based on anecdotal experiences. However, reports of sirolimus related side effects have decreased the transplant communities' enthusiasm towards promoting this agent as a safe immune suppression agent.

Sirolimus changes lipid concentrations and lipoprotein metabolism in kidney transplant recipients

BACKGROUND

Sirolimus (Rapammune, rapamycin, RAPA) is a strong immunosuppressive agent that reduces kidney transplant rejection. Hyperlipidemia is a significant side effect of sirolimus treatment and often leads to vascular disease. We have studied the repeatability, reversibility, and dose dependence of the plasma lipid and apoprotein changing effects of sirolimus and attempted to determine the mechanism by which sirolimus induces hypertriglyceridemia in some kidney transplant recipients.

METHODS

Six patients with renal allografts maintained on cyclosporine A and prednisone were selected on the basis of their previous hyperlipidemic response to short-term (14 days) sirolimus administration. For longer-term treatment, each patient was started on 10 mg/d sirolimus and continued as tolerated for 42 days to reinduce hyperlipidemia. Timed blood samples were analyzed for lipid, apoprotein, and sirolimus levels.

RESULTS

During sirolimus administration, mean total plasma cholesterol increased from 214 to 322 mg/dL (+50%); low density lipoprotein-cholesterol levels changed in a similar pattern. Mean triglyceride level rose from 227 to 432 mg/dL (+95%). ApoB-100 concentration rose from 124 to 160 mg/dL (+28%). ApoC-III level increased from 28.9 to 55.5 mg/dL (+92%). These lipid and apoprotein changes were found to be repeatable, reversible, and dose dependent. [(13)C(4)]-palmitate metabolic studies in four patients with hypertriglyceridemia indicated that the free fatty acid pool was expanded by sirolimus treatment (mean = 42.3%). Incorporation of [(13)C(4)]-palmitate into triglycerides of very low density lipoprotien, intermediate density lipoprotein, low density lipoproteins was decreased 38.3%, 42.1%, and 38.4%, respectively, by sirolimus treatment of these patients.

CONCLUSIONS

These results suggest that sirolimus alters the insulin signaling pathway so as to increase adipose tissue lipase activity, decrease lipoprotein lipase activity, or both, resulting in increased hepatic synthesis of triglyceride, increased secretion of VLDL, and increased hypertriglyceridemia.

Effects of sirolimus on plasma lipids, lipoprotein levels, and fatty acid metabolism in renal transplant patients

Sirolimus (Rapammune, rapamycin, RAPA) is a potent immunosuppressive drug that reduces renal transplant rejection. Hyperlipidemia is a significant side effect of sirolimus treatment, and frequently leads to cardiovascular disease. This study was undertaken to determine the repeatability, reversibility, and dose dependence of the plasma lipid and apolipoprotein altering effects of sirolimus, and to elucidate the mechanism by which sirolimus induces hypertriglyceridemia in some renal transplant patients. Six patients with renal allografts maintained on cyclosporine A and prednisone were selected on the basis of their previous hyperlipidemic response to short term (14 days) sirolimus administration. For longer-term treatment, each patient was started on 10 mg/day sirolimus and continued as tolerated for 42 days to reinduce hyperlipidemia. Timed blood samples were analyzed for lipid, apolipoprotein, and sirolimus levels. During sirolimus administration, mean total plasma cholesterol increased from 214 mg/dl to 322 mg/dl (+50%; range 25-92%); LDL-cholesterol levels followed a similar pattern. Mean triglyceride level rose from 227 to 432 mg/dl (+95%; range 9-254%). ApoB-100 concentration rose from 124 to 160 mg/dl (+28%; P < 0.05). ApoC-III level increased from 28.9 to 55.5 mg/dl, +92%; (P < 0.013). These lipid and apolipoprotein changes were found to be repeatable, reversible, and dose dependent. [(13)C(4)]palmitate metabolic studies in four patients with hypertriglyceridemia indicated that the free fatty acid pool was expanded by sirolimus treatment (mean = 42.3%). Incorporation of [(13)C(4)]palmitate into triglycerides of VLDL, IDL, and LDL was decreased 38.3%, 42,1%, and 38.4%, respectively, by sirolimus treatment of these patients. These results suggest that sirolimus alters the insulin signaling pathway so as to increase adipose tissue lipase activity and/or decrease lipoprotein lipase activity, resulting in increased hepatic synthesis of triglyceride, increased secretion of VLDL, and increased hypertriglyceridemia.

Interstitial pneumonitis associated with sirolimus: a dilemma for lung transplantation

Rapamycin/sirolimus (SR), trade named Rapammune (Wyeth-Ayerst, Sydney, Australia), is a potent immunosuppressive drug associated with myelosuppression, hypertension, hyperlipidemia, and infection. Rapamycin/sirolimus-induced pneumonitis has been described previously in renal transplant recipients, and this report describes a stable heart-lung transplant recipient who developed a pulmonary infiltrate that reversed after ceasing SR therapy. We believe that immunosuppression-induced pneumonitis in a lung allograft is a serious dilemma for lung transplant physicians

Effect of sirolimus on the metabolism of apoB100- containing lipoproteins in renal transplant patients

BACKGROUND

Sirolimus (Rapamune, rapamycin, RAPA) is a potent immunosuppressive drug that has reduced the rate of acute rejection episodes by more than 40% in phase III trials when added to an immunosuppression regimen of cyclosporine (CsA) and prednisone. However, RAPA treatment tends to increase lipid levels, particularly among patients with pre-existing hyperlipidemia.

METHODS

To identify the metabolic pathway(s) leading to RAPA-mediated hyperlipidemia, five patients with renal transplants maintained on CsA+/-prednisone+/- azathioprine (AZA) were studied before and after 6 weeks of treatment with RAPA (off RAPA and on RAPA, respectively). Each study patient was infused with a single bolus of [2H4]-lysine to derive metabolic parameters for apoB100-containing lipoproteins by using kinetic analysis based upon quantitation of isotopic enrichment by gas chromatography-mass spectrometry.

RESULTS

Serial lipid measurements revealed that four patients displayed increased plasma triglyceride levels after RAPA treatment, which coincided with significantly higher plasma VLDL-apoB100 concentrations (21.7+/-12.1 mg/dl off RAPA vs. 38.7+/-14.8 mg/dl on RAPA, mean+/-SD, P<0.05). Kinetic analysis showed that the RAPA-induced increase in VLDL-apoB100 concentrations was due to a significant reduction in the fractional catabolic rate (FCR) of very low-density lipoprotein (VLDL) apoB100 (0.83+/-0.65 off RAPA vs. 0.24+/-0.10 on RAPA, mean+/-SD, P<0.05), rather than an enhanced VLDL-apoB100 synthesis. In one patient, RAPA treatment induced hypercholesterolemia but not hypertriglyceridemia. This hypercholesterolemia was due to elevated low-density lipoprotein (LDL) cholesterol levels, which coincided with a decreased FCR of LDL-apoB100. Heparin-induced lipoprotein lipase activity was significantly lower in the immunosuppressed hyperlipidemic patients than in normolipidemic controls. However, RAPA treatment did not significantly alter basal lipoprotein lipase activity in renal transplant patients in this study.

CONCLUSIONS

This study indicates that for renal transplant patients in whom RAPA treatment induces hyperlipidemia, this effect is the result of reduced catabolism of apoB100-containing lipoproteins.

Promising early outcomes with a novel, complete steroid avoidance immunosuppression protocol in pediatric renal transplantation

BACKGROUND

Corticosteroids have been a cornerstone of immunosuppression for four decades despite their adverse side effects. Past attempts at steroid withdrawal in pediatric renal transplantation have had little success. This study tests the hypothesis that a complete steroid-free immunosuppressive protocol avoids steroid dependency for suppression of the immune response with its accompanying risk of acute rejection on steroid withdrawal.

METHODS

An open labeled prospective study of complete steroid avoidance immunosuppressive protocol was undertaken in 10 unsensitized pediatric recipients (ages 5-21 years; mean 14.4 years) of first renal allografts. Steroids were substituted with extended daclizumab use, in combination with tacrolimus and mycophenolate mofetil. Protocol biopsies were performed in the steroid-free group at 0, 1, 3, 6, and 12 months posttransplantation. Clinical outcomes were compared to a steroid-based group of 37 matched historical controls.

RESULTS

Graft and patient survival was 100% in both groups. Clinical acute rejection was absent in the steroid-free group at a mean follow-up time of 9 months (range 3-13.7 months). Protocol biopsies in the steroid-free group (includes 10 patients at 3 months, 7 at 6 months, and 4 at 12 months) revealed only two instances of mild (Banff 1A) subclinical rejection (reversed by only a nominal increase in immunosuppression) and no chronic rejection. At 6 months the steroid-free group had no hypertension requiring treatment (P=0.003), no hypercholesterolemia (P=0.007), and essentially no body disfigurement (P=0.0001). Serum creatinines, Schwartz GFR, and mean delta height Z scores trended better in the steroid-free group. In the steroid-free group, one patient had cytomegalovirus disease at 1 month and three had easily treated herpes simplex stomatitis, but with no significant increase in bacterial infections or rehospitalizations over the steroid-based group. The steroid-free group was more anemic early posttransplantation (P=0.004), suggesting an early role of steroids in erythrogenesis; erythropoietin use normalized hematocrits by 6 months.

CONCLUSIONS

Complete steroid-free immunosuppression is efficacious and safe in this selected group of children with no early clinical acute rejection episodes. This protocol avoids the morbid side effects of steroids without increasing infection, and may play a future critical role in avoiding noncompliance, although optimizing renal function and growth.

Selective aspects of the insulin resistance syndrome

There is increasing recognition of new features in the insulin resistance syndrome and its association with new disease states or treatment modalities. Recent additions to the list of features in the insulin resistance syndrome include elevated non-esterified fatty acids, abnormalities in visceral fat metabolism, elevated uric acid, elevated hematocrit, endothelial dysfunction, abnormalities in glucocorticoids, and differences in the phenotypic expression of the syndrome between men and women. A critical factor that may be inherent in the syndrome is the distribution and metabolism of visceral fat. This finding is also accompanied by the recognition of the role of non-esterified fatty acids as a cause of many of the risk factors in the insulin resistance syndrome. Elevated non-esterified fatty acids contribute to hypertension, glucose intolerance and increased arteriosclerosis. Elevated cortisol levels and disrupted metabolism, as well as abnormalities in the hypothalamic-pituitary-adrenal axis are seen in the insulin resistance syndrome. In women, adipose cells express fewer glucocorticoid receptors and less of the enzyme that metabolizes cortisol, 11beta-hydroxysteroid dehydrogenase. Several inflammatory factors such as tumor necrosis factor-alpha may be an etiologic link in the risk found in the insulin resistance syndrome. Certain cases of the syndrome appear to be related to specific drug therapies (steroids, immunosuppressive agents and antiretroviral agents), as seen in transplant patients and HIV-infected individuals.

Sirolimus: continuing the evolution of transplant immunosuppression

OBJECTIVE

To review the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and economic issues associated with sirolimus, the most recent immunosuppressive agent approved for kidney transplantation.

DATA SOURCES

A MEDLINE search (1966-June 2000) was completed to identify primary and review articles. In addition, abstracts from recent meetings on transplantation were reviewed for information and research on sirolimus.

STUDY SELECTION AND DATA EXTRACTION

Blinded, randomized, controlled studies were the goal, but, as with most newly approved immunosuppressive agents, a significant amount of information on sirolimus is not available in this optimal form. All articles were assessed and all pertinent information was incorporated in this review.

DATA SYNTHESIS

Sirolimus is structurally related to the immunosuppressive agent tacrolimus, and retains a pharmacokinetic and drug interaction profile similar to that of the calcineurin inhibitors, cyclosporine and tacrolimus. However, the novel mechanism of action of sirolimus differs significantly from these agents, as does its adverse effect profile. The most significant adverse reaction is hyperlipidemia. Clinical experience with sirolimus has allowed transplant centers to expand its use into other areas of transplantation as well as certain autoimmune disorders.

CONCLUSIONS

The definitive role of sirolimus will continue to be determined; however, sirolimus offers an excellent addition to the transplant immunosuppression armamentarium.