Sirolimus and cardiovascular disease risk in liver transplantation

Cancer therapy's impact on lipid metabolism: Mechanisms and future avenues

Atherosclerotic cardiovascular disease is a growing threat among cancer patients. Not surprisingly, cancer-targeting therapies have been linked to metabolic dysregulation including changes in local and systemic lipid metabolism. Thus, tumor development and cancer therapeutics are intimately linked to cholesterol metabolism and may be a driver of increased cardiovascular morbidity and mortality in this population. Chemotherapeutic agents affect lipid metabolism through diverse mechanisms. In this review, we highlight the mechanistic and clinical evidence linking commonly used cytotoxic therapies with cholesterol metabolism and potential opportunities to limit atherosclerotic risk in this patient population. Better understanding of the link between atherosclerosis, cancer therapy, and cholesterol metabolism may inform optimal lipid therapy for cancer patients and mitigate cardiovascular disease burden.

A Comprehensive Review on the Risk of Metabolic Syndrome and Cardiovascular Disease after Liver Transplantation

Survival rates after liver transplantation have increased dramatically over the past 20 years. Cardiovascular disease is the most common extra-hepatic cause of mortality in the long-term post liver transplant. This is intimately linked with both the higher pre-existing rates of metabolic syndrome in these patients as well as increased propensity to develop de novo metabolic syndrome post-transplant. This unfavorable metabolic profile that contributes to cardiovascular disease is multifactorial and largely preventable. This review explores metabolic syndrome and cardiovascular disease and their contributory factors post liver transplantation to highlight areas for potential intervention and thus reduce the significant morbidity and mortality of patients due to metabolic syndrome and cardiovascular disease.

Mtor inhibitors associated with higher cardiovascular adverse events-A large population database analysis

There are limited real-world data available regarding adverse events (AEs) of immunosuppressants. We utilized the FDA Adverse Event Reporting System (FAERS) database from 2004 to 2018 to perform a retrospective database analysis. We analyzed AE reports due to the individual agents tacrolimus, sirolimus, or everolimus and compared reporting odds ratios of the mTOR inhibitors to tacrolimus. The mTOR inhibitors arm had 1282 reports with 4176 AEs, while the tacrolimus arm had a total of 7587 reports with 20 940 individual AEs. mTOR inhibitors had significantly higher incidences of cardiovascular (ROR 1.95, 95% CI 1.70, 2.23), dermatologic (ROR 1.34, 95% CI 1.04, 1.73), endocrine (ROR 1.52, 95% CI 1.26, 1.82), gastrointestinal (ROR 1.15, 95% CI 1.01, 1.30), infectious disease (ROR 1.35, 95% 1.20, 1.52), musculoskeletal (ROR 1.39, 95% CI 1.13, 1.70), pulmonary (ROR 3.46, 95% 2.97, 4.03), renal (ROR 1.27, 95% CI 1.10, 1.46), and vascular AEs (ROR 3.10, 95% CI 2.14, 4.49). Across every organ type, mTOR inhibitors had greater cardiovascular AEs compared to tacrolimus, specifically in arteriosclerosis, heart failure, hypotension, tachycardia, chest pain, edema, and pericardial disorders. mTOR inhibitors may be associated with higher cardiovascular AEs. Further investigation is required to determine the potential mechanism of this effect.

Pre-transplant diabetes predicts atherosclerotic vascular events and cardiovascular mortality in liver transplant recipients: a long-term follow-up study

Background Early after surgery, liver transplant (LT) recipients often develop weight gain. Metabolic disorders and cardiovascular disease represent main drivers of morbidity and mortality. Our aim was to identify predictors of atherosclerotic vascular events (AVE) and to assess the impact of AVE on the long-term outcome. Methods We retrospectively analyzed data from patients transplanted between 2000 and 2005 and followed-up in five Italian transplant clinics. Cox Regression analysis was performed to identify predictors of AVE, global mortality, and cardiovascular mortality. Survival analysis was performed using the Kaplan-Meier method. Results We analyzed data from 367 subjects during a median follow-up of 14 years. Thirty-seven post-LT AVE were registered. Patients with AVE more frequently showed pre-LT diabetes mellitus (DM) (48.6 vs 13.9%, p=0.000). In the post-LT period, patients with AVE satisfied criteria of metabolic syndrome in 83.8% vs. 36.7% of subjects without AVE (p=0.000). At multivariate analysis, pre-LT DM independently predicted AVE (HR 2.250, CI 4.848-10.440, p=0.038). Moreover, both pre-LT DM and AVE strongly predicted cardiovascular mortality (HR 5.418, CI 1.060-29.183, p=0.049, and HR 86.097, CI 9.510-779.480, p=0.000, respectively). Conclusions Pre-LT DM is the main risk factor for post-LT AVE. Pre-LT DM and post-LT AVE are strong, long-term predictors of cardiovascular mortality. Patients with pre-LT DM should obtain a personalized follow-up for prevention or early diagnosis of AVE.

Understanding and managing cardiovascular outcomes in liver transplant recipients

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is a common cause of mortality after liver transplantation. The transplant community is focused on improving long-term survival. Understanding the prevalence of CVD in liver transplant recipients, precipitating factors as well as prevention and management strategies is essential to achieving this goal.

RECENT FINDINGS

CVD is the leading cause of death within the first year after transplant. Arrhythmia and heart failure are the most often cardiovascular morbidities in the first year after transplant which could be related to pretransplant diastolic dysfunction. Pretransplant diastolic dysfunction is reflective of presence of cirrhotic cardiomyopathy which is not as harmless as it was thought. Multiple cardiovascular risk prediction models have become available to aid management in liver transplant recipients.

SUMMARY

A comprehensive prevention and treatment strategy is critical to minimize cardiovascular morbidity and mortality after liver transplant. Weight management and metabolic syndrome control are cornerstones to any prevention and management strategy. Bariatric surgery is an underutilized tool in liver transplant recipients. Awareness of 'metabolic-friendly' immunosuppressive regimens should be sought. Strict adherence to the cardiology and endocrine society guidelines with regard to managing metabolic derangements post liver transplantation is instrumental for CVD prevention until transplant specific recommendations can be made.

PRAS40 suppresses atherogenesis through inhibition of mTORC1-dependent pro-inflammatory signaling in endothelial cells

Endothelial pro-inflammatory activation plays a pivotal role in atherosclerosis, and many pro-inflammatory and atherogenic signals converge upon mechanistic target of rapamycin (mTOR). Inhibitors of mTOR complex 1 (mTORC1) reduced atherosclerosis in preclinical studies, but side effects including insulin resistance and dyslipidemia limit their clinical use in this context. Therefore, we investigated PRAS40, a cell type-specific endogenous modulator of mTORC1, as alternative target. Indeed, we previously found PRAS40 gene therapy to improve metabolic profile; however, its function in endothelial cells and its role in atherosclerosis remain unknown. Here we show that PRAS40 negatively regulates endothelial mTORC1 and pro-inflammatory signaling. Knockdown of PRAS40 in endothelial cells promoted TNFα-induced mTORC1 signaling, proliferation, upregulation of inflammatory markers and monocyte recruitment. In contrast, PRAS40-overexpression blocked mTORC1 and all measures of pro-inflammatory signaling. These effects were mimicked by pharmacological mTORC1-inhibition with torin1. In an in vivo model of atherogenic remodeling, mice with induced endothelium-specific PRAS40 deficiency showed enhanced endothelial pro-inflammatory activation as well as increased neointimal hyperplasia and atherosclerotic lesion formation. These data indicate that PRAS40 suppresses atherosclerosis via inhibition of endothelial mTORC1-mediated pro-inflammatory signaling. In conjunction with its favourable effects on metabolic homeostasis, this renders PRAS40 a potential target for the treatment of atherosclerosis.

Cardiovascular morbidity and mortality is increased post-liver transplantation even in recipients with no pre-existing risk factors

BACKGROUND/AIMS

Post-liver transplant (LT) metabolic syndrome (PTMS) and cardiovascular (CVS) mortality are becoming increasingly prevalent following sustained improvements in post-LT survival. We investigated the prevalence and predictors of PTMS and CVS complications in a cohort of consecutive LT recipients.

METHODS

We reviewed prospectively collected data of patients (n = 928) who underwent LT (1995-2013) and survived at least 1-year post-LT or died before that due to a major CVS complication.

RESULTS

Median follow-up was 85 months (IQR = 106). The prevalence of PTMS was 22.4% and it developed de novo in 183 recipients (19.7%). A total of 187 (20.2%) patients developed at least one CVS event post-LT within a median of 49 months (IQR = 85). Overall mortality rate was 22.6% (n = 210). Causes of death were CVS events (n = 45, 21.4%), malignancies (21%), liver-related deaths (20%) and infections (6.7%). Independent predictors of major CVS events were: documented CVS disease pre-LT (Hazard Ratio (HR) = 3.330; 95% CI = 1.620-6.840), DM (HR = 1.120; 95% CI 1.030-1.220), hypertension (HR = 1.140; 95% CI 1.030-1.270), dyslipidaemia (HR = 1.140; 95% CI 1.050-1.240) and creatinine levels at 1 year (HR = 1.010; 95% CI = 1.005-1.013). Among LT recipients without pre-LT CVS disease or MS components (n = 432), 85 recipients developed ≥1 CVS events (19.7%) with independent predictors being DM (HR = 1.150; 95% CI = 1.010-1.320), creatinine levels at 1 year (HR = 1.020; 95% CI = 1.010-1.030) and hypertension (HR = 1.190; 95% CI = 1.040-1.360).

CONCLUSIONS

Post-LT patients are at increased risk of CVS morbidity even in the absence of pre-existing metabolic risk factors. Renal sparing immunosuppressive protocols might reduce CVS events post-LT.

mTOR Inhibition and Cardiovascular Diseases: Dyslipidemia and Atherosclerosis

Inhibitors of the mechanistic target of rapamycin (mTOR) have unique antiatherosclerotic effects, such as depletion of plaque macrophages, induction of autophagy, and activation of cholesterol efflux. However, a common side effect of their use is dyslipidemia, a well-known risk factor for atherosclerosis. Indeed, mTOR inhibitors prevent lipid storage, increase low-density lipoprotein cholesterol levels, and activate lipolysis. Although the net effect of mTOR inhibition seems favorable, the use of cholesterol lowering drugs to manage dyslipidemia remains the most recommended strategy.

De-novo nonalcoholic steatohepatitis is associated with long-term increased mortality in liver transplant recipients

OBJECTIVE

Patients who have undergone transplantation often develop metabolic syndrome (MetS) and de-novo nonalcoholic fatty liver disease (NAFLD). Our aim was to evaluate the impact of metabolic disease on cardiovascular and neoplastic risk and survival.

PATIENTS AND METHODS

Data from patients who underwent transplantation between 2000 and 2005 in two Italian transplant centers were analyzed. Cox regression analysis was carried out for predictors of de-novo NAFLD and nonalcoholic steatohepatitis (NASH), cardiovascular events, de-novo extrahepatic cancers, and survival. Survival analysis was completed using the Kaplan-Meier method. A P value less than 0.05 was considered significant for all tests.

RESULTS

De-novo NAFLD was found in one-fifth of 194 patients. Patients with de-novo NAFLD fulfilled the criteria of MetS in 74.4% of cases, while patients without de-novo NAFLD in 29.8% (P=0.000). On multivariate analysis, MetS correlated independently with de-novo NAFLD and this emerged as an independent predictor of cardiovascular events and as a relevant risk factor for solid extrahepatic cancer. Data on smoking habits, which represent a consolidated risk factor for cardiovascular events and cancer in both the general population and patients who have undergone transplantation, are not available. In the subset of histologically proven NASH, it was the strongest predictor of long-term survival (hazard ratio=4.133, 95% confidence interval: 1.385-12.331, P=0.011).

CONCLUSION

Post-transplant NAFLD represented a strong risk factor for cardiovascular atherosclerotic disease and solid extrahepatic cancer, whereas de novo histologically proven NASH was an independent predictor of long-term mortality.

Conversion From Sirolimus to Everolimus in Long-Term Liver Graft Recipients

Immunosuppression by inhibition of the mechanistic target of rapamycin (mTOR) is a promising approach after liver transplantation. The mTOR inhibitor sirolimus was used in selected liver graft recipients despite safety concerns and lack of approval. Everolimus is another mTOR inhibitor approved after liver transplantation. It is currently unknown, whether conversion of sirolimus to everolimus is safe in long-term liver graft recipients. Long-term liver graft recipients treated with sirolimus were converted to everolimus. A systematical analysis of biochemical and clinical data before and after conversion was performed. Sixteen patients were included (female/male, 8/8). Median (range) age at conversion was 66 years (49-78 years), and patients were converted at a median (range) of 10.1 years (4.0-22.3 years) after liver transplantation. In the majority of patients, no dose adjustment was needed after conversion. No rejection and no cytomegalovirus replication episodes were observed. Furthermore, no differences were found with respect to kidney function, diabetes mellitus, or blood pressure before and after conversion. Bilirubin serum concentration was lower, whereas aspartate aminotransaminase, alanine aminotransferase, and triglycerides serum concentrations were higher after conversion to everolimus. Neither clinical- nor graft-associated significant complications were observed after conversion from sirolimus to everolimus in long-term liver graft recipients. Everolimus-based immunosuppression may be offered to patients after liver transplantation formerly treated with sirolimus.

Contribution of mammalian target of rapamycin in the pathophysiology of cirrhotic cardiomyopathy

AIM: To explore the role of mammalian target of rapamycin (mTOR) in the pathogenesis of cirrhotic cardiomyopathy and the potential of rapamycin to improve this pathologic condition.

METHODS: Male albino Wistar rats weighing 100-120 g were treated with tetrachloride carbon (CCl₄) for 8 wk to induce cirrhosis. Subsequently, animals were administered rapamycin (2 mg/kg per day). The QT_c intervals were calculated in a 5-min electrocardiogram. Then, the left ventricular papillary muscles were isolated to examine inotropic responsiveness to β-adrenergic stimulation using a standard organ bath equipped by Powerlab system. Phosphorylated-mTOR localization in left ventricles was immunohistochemically assessed, and ventricular tumor necrosis factor (TNF)-α was measured. Western blot was used to measure levels of ventricular phosphorylated-mTOR protein.

RESULTS: Cirrhosis was confirmed by hematoxylin and eosin staining of liver tissues, visual observation of lethargy, weight loss, jaundice, brown urine, ascites, liver stiffness, and a significant increase of spleen weight (P < 0.001). A significant prolongation in QT_c intervals occurred in cirrhotic rats exposed to CCl₄ (P < 0.001), while this prolongation was decreased with rapamycin treatment (P < 0.01). CCl₄-induced cirrhosis caused a significant decrease of contractile responsiveness to isoproterenol stimulation and a significant increase in cardiac TNF-α. These findings were correlated with data from western blot and immunohistochemical studies on phosphorylated-mTOR expression in left ventricles. Phosphorylated-mTOR was significantly enhanced in cirrhotic rats, especially in the endothelium, compared to controls. Rapamycin treatment significantly increased contractile force and myocardial localization of phosphorylated-mTOR and decreased cardiac TNF-α concentration compared to cirrhotic rats with no treatment.

CONCLUSION: In this study, we demonstrated a potential role for cardiac mTOR in the pathophysiology of cirrhotic cardiomyopathy. Rapamycin normalized the inotropic effect and altered phosphorylated-mTOR expression and myocardial localization in cirrhotic rats.

Incidence of cardiovascular and cerebrovascular events associated with sirolimus use after liver transplantation

BACKGROUND

Sirolimus (SRL) is an immunosuppressant often used in liver transplantation (LT) to mitigate renal insufficiency associated with calcineurin inhibitors. Sirolimus can cause hyperlipidemia, but its association with coronary artery disease (CAD) and cerebrovascular accidents (CVAs) is unclear. The purpose of this study was to assess the risk of CAD and CVAs with the use of SRL in LT recipients.

METHODS

We retrospectively reviewed all of our LT recipients from 2000 to 2011. Patients with multiorgan transplant, multiple liver transplants, everolimus therapy, or survival <3 months were excluded. The 803 remaining patients were divided into 3 groups: 1) 134 patients who received and tolerated SRL; 2) 604 patients who never received SRL; and 3) 65 patients who started but discontinued SRL. The primary outcome was the development of CAD or CVA beyond 4 months after transplantation with the use of time-dependent Kaplan-Meier analysis.

RESULTS

In group 1, there were 6 CAD and 2 CVA events; in group 2, 27 CAD and 16 CVA events; and in group 3, 10 CAD and 2 CVA events. The event-free survival for CAD/CVA at 1, 3, and 5 years was 100%, 98.1%, and 97.2% respectively for group 1; 99.7%, 98.4%, and 96.1% for group 2; and 92.3%, 92.3%, and 85.6% for group 3. On an unadjusted basis, compared with group 2, there was no difference in CAD/CVA rates in group 1 (hazard ratio [HR] 0.92; not significant), but there was an increase in group 3 (HR 2.94; P = .0019). However, on multivariate analysis, only age at transplantation (HR 1.06; P = .001) and diabetes before transplantation (P = .011) were associated with increased CAD/CVA risk.

CONCLUSIONS

Our analysis showed that patients receiving SRL after LT had no increased risk of CAD/CVA events compared with patients maintained on a calcineurin inhibitor. The risk of CAD/CVA should not be a factor in avoiding SRL.

A retrospective 15-year review: survival advantage after switching to sirolimus in hepatitis C virus infected liver graft recipients

BACKGROUND

The use of sirolimus-based immune suppression in liver transplantation, particularly in hepatitis C virus (HCV)-infected recipients, remains contentious. There is some evidence that sirolimus retards hepatic fibrosis, is renal sparing and may be of benefit in preventing hepatocellular carcinoma (HCC) recurrence. Sirolimus has not been adopted by many transplant centres because of persistent concerns regarding an increased risk of hepatic artery thrombosis, graft loss and death with de novo sirolimus.

AIM

To review the impact of switching to sirolimus monotherapy in HCV-infected liver recipients with respect to survival, graft loss and hepatic fibrosis.

METHODS

A retrospective review of 190 patients from a single centre undergoing first liver transplantation for HCV over 15 years. 113 patients were switched from calcineurin inhibitor (CNI)-based therapy to low-dose sirolimus monotherapy at a median of 15 months after transplantation for HCV-related fibrosis (72%), renal impairment (14%) or high-risk HCC (5%).

RESULTS

Patients switched to sirolimus had improved survival (P < 0.001) and slower progression to cirrhosis (P = 0.001). In patients with HCC (n = 91), sirolimus duration rather than strategy was an independent predictor of survival (P = 0.001) and extended time to HCC recurrence (33 vs. 16 months). Patients switched for renal dysfunction showed improvement in serum creatinine (140-108 μmol/L, P = 0.001). Those remaining on CNI-therapy were more likely to develop post-transplant diabetes (P = 0.03).

CONCLUSION

These data suggest selective switching to low-dose sirolimus monotherapy in HCV-positive liver recipients improves clinical outcome.

Immunosuppression: trends and tolerance?

Advances in pharmacologic immunosuppression are responsible for the excellent outcomes experienced by recipients of liver transplants. However, long-term follow-up of these patients reveals an increasing burden of morbidity and mortality that is attributable to these drugs. The authors summarize the agents used in contemporary liver transplantation immunosuppression protocols and discuss the emerging trend within the community to minimize or eliminate these agents from use. The authors present recently published data that may provide the foundation for immunosuppression minimization or tolerance induction in the future and review studies that have focused on the utility of biomarkers in guiding immunosuppression management.

Multiple indications for everolimus after liver transplantation in current clinical practice

AIM: To assess our experience with the use and management of everolimus-based regimens post-liver transplantation and to redefine the potential role of this drug in current clinical practice.

METHODS: From October 1988 to December 2012, 1023 liver transplantations were performed in 955 patients in our Unit. Seventy-four patients (7.74%) received immunosuppression with everolimus at some time post-transplantation. Demographic characteristics, everolimus indication, time elapsed from transplantation to the introduction of everolimus, doses and levels administered, efficacy, side effects, discontinuation and post-conversion survival were analyzed.

RESULTS: Mean age at the time of conversion to everolimus was 57.7 ± 10 years. Indications for conversion were: refractory rejection 31.1%, extended hepatocellular carcinoma in explanted liver 19%, post-transplant hepatocellular carcinoma recurrence 8.1%, de novo tumour 17.6%, renal insufficiency 8.1%, severe neurotoxicity 10.8%, and others 5.4%. Median time from transplantation to introduction of everolimus was 6 mo (range: 0.10-192). Mean follow-up post-conversion was 22 ± 19 mo (range: 0.50-74). The event for which the drug was indicated was resolved in 60.8% of patients, with the best results in cases of refractory rejection, renal insufficiency and neurotoxicity. Results in patients with cancer were similar to those of a historical cohort treated with other immunosuppressants. The main side effects were dyslipidemia and infections. Post-conversion acute rejection occurred in 14.9% of cases. The drug was discontinued in 28.4% of patients.

CONCLUSION: Everolimus at low doses in combination with tacrolimus is a safe immunosuppressant with multiple early and late indications post-liver transplantation.

Tacrolimus and sirolimus have distinct effects on insulin signaling in male and female rats

Although the contribution of the immunosuppressants tacrolimus (TAC) and sirolimus (SIR) to the development of posttransplant diabetes mellitus (PTDM) are being increasingly recognized, the mechanisms of immunosuppressant-induced hyperglycemia are unclear. SIR induces insulin resistance predominantly, but is associated with β-cell dysfunction in rodents. TAC affects islet function but is associated with worsening insulin sensitivity in a few, and improvement in some, clinical studies. We sought to clarify the contributions of TAC and SIR to insulin resistance and islet function. Four groups of male and female Sprague-Dawley rats received TAC, SIR, TAC and SIR, or control for 2 weeks. All rats were administered an oral glucose challenge at the end of treatment. Half the groups were sacrificed 10 minutes after administration of regular insulin whereas the other half did not receive insulin before sacrifice. Liver, pancreas, fat, and muscle were harvested subsequently. Quantification of Western blots revealed that SIR and TAC plus SIR suppressed the phospho-Akt (pAkt)-to-Akt ratios in liver, muscle, and fat compared with control, regardless of sex. TAC alone did not impair the pAkt-to-Akt ratios in any of the tissues in male and female rats. β-Cell mass was reduced significantly after TAC treatment in male rats. SIR did not affect β-cell mass, regardless of sex. Our study demonstrated very clearly that SIR impairs insulin signaling, without any effect on β-cell mass, and TAC does not impair insulin signaling but reduces β-cell mass. Our efforts are key to understanding the mechanisms of immunosuppressant-induced hyperglycemia and to tailoring treatments for PTDM.

De novo sirolimus and reduced-dose tacrolimus versus standard-dose tacrolimus after liver transplantation: the 2000-2003 phase II prospective randomized trial

We studied whether the use of sirolimus with reduced-dose tacrolimus, as compared to standard-dose tacrolimus, after liver transplantation is safe, tolerated and efficacious. In an international multicenter, open-label, active-controlled randomized trial (2000-2003), adult primary liver transplant recipients (n=222) were randomly assigned immediately after transplantation to conventional-dose tacrolimus (trough: 7-15 ng/mL) or sirolimus (loading dose: 15 mg, initial dose: 5 mg titrated to a trough of 4-11 ng/mL) and reduced-dose tacrolimus (trough: 3-7 ng/mL). The study was terminated after 21 months due to imbalance in adverse events. The 24-month cumulative incidence of graft loss (26.4% vs. 12.5%, p=0.009) and patient death (20% vs. 8%, p=0.010) was higher in subjects receiving sirolimus. A numerically higher rate of hepatic artery thrombosis/portal vein thrombosis was observed in the sirolimus arm (8% vs. 3%, p=0.065). The incidence of sepsis was higher in the sirolimus arm (20.4% vs. 7.2%, p=0.006). Rates of acute cellular rejection were similar between the two groups. Early use of sirolimus using a loading dose followed by maintenance doses and reduced-dose tacrolimus in de novo liver transplant recipients is associated with higher rates of graft loss, death and sepsis when compared to the use of conventional-dose tacrolimus alone.