Sirolimus affects cardiomyocytes to reduce left ventricular mass in heart transplant recipients

An Unusual Presentation of Apical Hypertrophic Cardiomyopathy in an Orthotopic Heart Transplant Recipient

In this case study, we present the evaluation of an orthotopic heart transplant (OHT) patient who presented with persistent shortness of breath and dizziness upon standing. The investigation uncovered the presence of progressive hypertrophic cardiomyopathy (HCM) in the transplanted heart, a condition first detected 11 years after the transplantation. Utilizing echocardiography with global longitudinal strain (GLS), we determined that the HCM likely originated from genetic predominance inherited from the heart donor rather than hypertensive disease. This finding highlights the significance of genetic factors in post-transplant complications and warrants further investigation into the long-term effects of heart transplantation on recipient health.

Cardiovascular Outcomes in De Novo Kidney Transplant Recipients Receiving Everolimus and Reduced Calcineurin Inhibitor or Standard Triple Therapy: 24-month Post Hoc Analysis From TRANSFORM Study

BACKGROUND

The comparative impact of everolimus (EVR)-based regimens versus standard of care (mycophenolic acid+standard calcineurin inhibitor [MPA+sCNI]) on cardiovascular outcomes in de novo kidney transplant recipients (KTRs) is poorly understood. The incidence of major adverse cardiac events (MACEs) in KTRs receiving EVR+reduced CNI (rCNI) or MPA+sCNI from the TRANSplant eFficacy and safety Outcomes with an eveRolimus-based regiMen study was evaluated.

METHODS

The incidence of MACE was determined for all randomized patients receiving at least 1 dose of the study drug. Factors associated with MACEs were determined by logistic regression. Risk of MACE out to 3 y post-study was calculated using the Patient Outcome in Renal Transplantation equation.

RESULTS

MACE occurred in 81 of 1014 (8.0%; EVR+rCNI) versus 89 of 1012 (8.8%; MPA+sCNI) KTRs (risk ratio, 0.91 [95% confidence interval [CI], 0.68-1.21]). The incidence of circulatory death, myocardial infarction, revascularization, or angina was similar between the arms. Incidence of MACE was similar between EVR+rCNI and MPA+sCNI arms with a higher incidence in prespecified risk groups: older age, pretransplant diabetes (15.1% versus 15.9%), statin use (8.5% versus 10.8%), and low estimated glomerular filtration rate (Month 2 estimated glomerular filtration rate <30 versus >60 mL/min/1.73 m 2 ; odds ratio, 2.23 [95% CI, 1.02-4.86]; P = 0.044), respectively. Predicted risk of MACE within 3 y of follow-up did not differ between the treatment arms.

CONCLUSIONS

Cardiovascular morbidity and mortality were similar between de novo KTRs receiving EVR+rCNI and MPA+sCNI. EVR+rCNI is a viable alternative to the current standard of care in KTRs.

Hypertrophic Cardiomyopathy After Heart Transplantation: A Single-Center Case Series

We present 3 heart transplant recipients who developed hypertrophic cardiomyopathy years after transplantation. In all 3 cases, the diagnosis was initially made based on echocardiography and confirmed using cardiac magnetic resonance imaging. (Level of Difficulty: Advanced.).

Management of cardiac diseases in liver transplant recipients: Comprehensive review and multidisciplinary practice-based recommendations

Cardiac diseases are one of the most common causes of morbidity and mortality following liver transplantation (LT). Prior studies have shown that cardiac diseases affect close to one-third of liver transplant recipients (LTRs) long term and that their incidence has been on the rise. This rise is expected to continue as more patients with advanced age and/or non-alcoholic steatohepatitis undergo LT. In view of the increasing disease burden, a multidisciplinary initiative was developed to critically review the existing literature (between January 1, 1990 and March 17, 2021) surrounding epidemiology, risk assessment, and risk mitigation of coronary heart disease, arrhythmia, heart failure, and valvular heart disease and formulate practice-based recommendations accordingly. In this review, the expert panel emphasizes the importance of optimizing management of metabolic syndrome and its components in LTRs and highlights the cardioprotective potential for the newer diabetes medications (e.g., sodium glucose transporter-2 inhibitors) in this high-risk population. Tailoring the multidisciplinary management of cardiac diseases in LTRs to the cardiometabolic risk profile of the individual patient is critical. The review also outlines numerous knowledge gaps to pave the road for future research in this sphere with the ultimate goal of improving clinical outcomes.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

Novel Immunosuppression in Solid Organ Transplantation

Solid organ transplantation and survival has improved tremendously in the last few decades, much of the success has been attributed to the advancements in immunosuppression. While steroids are being replaced and much of the immunosuppressive strategies focus on steroid free regimens, novel agents have introduced in the induction, maintenance, and treatment of acute rejection phase. MTOR inhibitors have helped with the renal sparing side effect from the calcineurin inhibitors, newer agents such as rituximab have decreased the incidence of donor-specific antibodies which led to decreased incidence of acute rejection reactions. In this chapter we discuss the newer therapies directed specifically for solid organ transplantation.

Cardiovascular Effects of Autologous Bone Marrow-Derived Mesenchymal Stromal Cell Therapy With Early Tacrolimus Withdrawal in Renal Transplant Recipients: An Analysis of the Randomized TRITON Study

Background After renal transplantation, there is a need of immunosuppressive regimens that effectively prevent allograft rejection while minimizing cardiovascular complications. This substudy of the TRITON trial evaluated the cardiovascular effects of autologous bone marrow-derived mesenchymal stromal cells (MSCs) in renal transplant recipients. Methods and Results Renal transplant recipients were randomized to MSC therapy, infused at weeks 6 and 7 after transplantation, with withdrawal at week 8 of tacrolimus or standard tacrolimus dose. Fifty-four patients (MSC group=27; control group=27) underwent transthoracic echocardiography at weeks 4 and 24 after transplantation and were included in this substudy. Changes in clinical and echocardiographic variables were compared. The MSC group showed a benefit in blood pressure control, assessed by a significant interaction between changes in diastolic blood pressure and the treatment group (P=0.005), and a higher proportion of patients achieving the predefined blood pressure target of <140/90 mm Hg compared with the control group (59.3% versus 29.6%, P=0.03). A significant reduction in left ventricular mass index was observed in the MSC group, whereas there were no changes in the control group (P=0.002). The proportion of patients with left ventricular hypertrophy decreased at 24 weeks in the MSC group (33.3% versus 70.4%, P=0.006), whereas no changes were noted in the control group (63.0% versus 48.1%, P=0.29). Additionally, MSC therapy prevented progressive left ventricular diastolic dysfunction, as demonstrated by changes in mitral deceleration time and tricuspid regurgitant jet velocity. Conclusions MSC strategy is associated with improved blood pressure control, regression of left ventricular hypertrophy, and prevention of progressive diastolic dysfunction at 24 weeks after transplantation. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03398681.

Everolimus for the Prevention of Calcineurin-Inhibitor-Induced Left Ventricular Hypertrophy After Heart Transplantation (RADTAC Study)

OBJECTIVES

This study aimed to determine the safety and efficacy of combined low-dose everolimus and low-dose tacrolimus compared with standard-dose tacrolimus in attenuating left ventricular hypertrophy (LVH) after orthotopic heart transplantation (OHT).

BACKGROUND

Calcineurin inhibitors (CNIs) such as tactrolimus are important in preventing cardiac allograft rejection and reducing mortality after OHT. However CNIs are causatively linked to the development of LVH, and are associated with nephrotoxicity and vasculopathy. CNI-sparing agents such as everolimus have been hypothesized to inhibit adverse effects of CNIs.

METHODS

In this prospective, randomized, open-label study, OHT recipients were randomized at 12 weeks after OHT to a combination of low-dose everolimus and tacrolimus (the RADTAC group) or standard-dose tacrolimus (the TAC group), with both groups coadministered mycophenolate and prednisolone. The primary endpoint was LVH indexed as the change in left ventricular mass (ΔLVM) by cardiovascular magnetic resonance (CMR) imaging from 12 to 52 weeks. Secondary endpoints included CMR-based myocardial performance, T1 fibrosis mapping, blood pressure, and renal function. Safety endpoints included episodes of allograft rejection and infection.

RESULTS

Forty stable OHT recipients were randomized. Recipients in the RADTAC group had significantly lower tacrolimus levels compared with the TAC group (6.5 ± 3.5 μg/l vs. 8.6 ± 2.8 μg/l; p = 0.02). The mean everolimus level in the RADTAC group was 4.2 ± 1.7 μg/l. A significant reduction in LVM was observed in the RADTAC group compared with an increase in LVM in the TAC group (ΔLVM = -13.0 ± 16.8 g vs. 2.1 ± 8.4 g; p < 0.001). Significant differences were also noted in secondary endpoints measuring function and fibrosis (Δ circumferential strain = -2.9 ± 2.8 vs. 2.1 ± 2.3; p < 0.001; ΔT1 mapping values = -32.7 ± 51.3 ms vs. 26.3 ± 90.4 ms; p = 0.003). No significant differences were observed in blood pressure (Δ mean arterial pressure = 4.2 ± 18.8 mm Hg vs. 2.8 ± 13.8 mm Hg; p = 0.77), renal function (Δ creatinine = 3.1 ± 19.9 μmol/l vs. 9 ± 21.8 μmol/l; p = 0.31), frequency of rejection episodes (p = 0.69), or frequency of infections (p = 0.67) between groups.

CONCLUSIONS

The combination of low-dose everolimus and tacrolimus compared with standard-dose tacrolimus safely attenuates LVH in the first year after cardiac transplantation with an observed reduction in CMR-measured fibrosis and an improvement in myocardial strain.

Potential Effects of Immunosuppression on Oxidative Stress and Atherosclerosis in Kidney Transplant Recipients

Chronic kidney disease is a public health problem that, depending on the country, affects approximately 8-13% of the population, involving both males and females of all ages. Renal replacement therapy remains one of the most costly procedures. It is assumed that one of the factors influencing the course of chronic kidney disease might be oxidative stress. It is believed that the main mediators of oxidative stress are reactive oxygen species (ROS). Transiently increased concentrations of ROS play a significant role in maintaining an organism's homeostasis, as they are part of the redox-related signaling, and in the immune defense system, as they are produced in high amounts in inflammation. Systemic oxidative stress can significantly contribute to endothelial dysfunction along with exaggeration of atherosclerosis and development of cardiovascular disease, the leading cause of mortality in patients with kidney disease. Moreover, the progression of chronic kidney disease is strictly associated with the atherosclerotic process. Transplantation is the optimal method for renal replacement therapy. It improves better quality of life and prolongs survival compared with hemodialysis and peritoneal dialysis; however, even a successful transplantation does not correct the abnormalities found in chronic kidney disease. As transplantation reduces the concentration of uremic toxins, which are a factor of inflammation per se, both the procedure itself and the subsequent immunosuppressive treatment may be a factor that increases oxidative stress and hence vascular sclerosis and atherosclerotic cardiovascular disease. In the current work, we review the effect of several risk factors in kidney transplant recipients as well as immunosuppressive therapy on oxidative stress.

Impact of Sirolimus as a Primary Immunosuppressant on Myocardial Fibrosis and Diastolic Function Following Heart Transplantation

Background

Myocardial fibrosis is an important contributor for development of diastolic dysfunction. We investigated the impact of sirolimus as primary immunosuppression on diastolic dysfunction and fibrosis progression among heart transplantation recipients.

Methods and Results

In 100 heart transplantation recipients who were either treated with a calcineurin inhibitor (CNI) (n=51) or converted from CNI to sirolimus (n=49), diastolic function parameters were assessed using serial echocardiograms and right heart catheterizations. Myocardial fibrosis was quantified on serial myocardial biopsies. After 3 years, lateral e′ increased within the sirolimus group but decreased in the CNI group (0.02±0.04 versus −0.02±0.04 m/s delta change; P=0.003, respectively). Both pulmonary capillary wedge pressure and diastolic pulmonary artery pressure significantly decreased in the sirolimus group but remained unchanged in the CNI group (−1.50±2.59 versus 0.20±2.20 mm Hg/year; P=0.02; and −1.72±3.39 versus 0.82±2.59 mm Hg/year; P=0.005, respectively). A trend for increased percentage of fibrosis was seen in the sirolimus group (8.48±3.17 to 10.10±3.0%; P=0.07) as compared with marginally significant progression in the CNI group (8.76±3.87 to 10.56±4.34%; P=0.04). The percent change in fibrosis did not differ significantly between the groups (1.62±4.67 versus 1.80±5.31%, respectively; P=0.88).

Conclusions

Early conversion to sirolimus is associated with improvement in diastolic dysfunction and filling pressures as compared with CNI therapy. Whether this could be attributed to attenuation of myocardial fibrosis progression with sirolimus treatment warrants further investigation.

A 6-month systems toxicology inhalation study in ApoE-/- mice demonstrates reduced cardiovascular effects of E-vapor aerosols compared with cigarette smoke

Smoking cigarettes is harmful to the cardiovascular system. Considerable attention has been paid to the reduced harm potential of alternative nicotine-containing inhalable products such as e-cigarettes. We investigated the effects of E-vapor aerosols or cigarette smoke (CS) on atherosclerosis progression, cardiovascular function, and molecular changes in the heart and aorta of female apolipoprotein E-deficient (ApoE^-/-) mice. The mice were exposed to aerosols from three different E-vapor formulations: 1) carrier (propylene glycol and vegetable glycerol), 2) base (carrier and nicotine), or 3) test (base and flavor) or to CS from 3R4F reference cigarettes for up to 6 mo. Concentrations of CS and base or test aerosols were matched at 35 µg nicotine/L. Exposure to CS, compared with sham-exposed fresh air controls, accelerated atherosclerotic plaque formation, whereas no such effect was seen for any of the three E-vapor aerosols. Molecular changes indicated disease mechanisms related to oxidative stress and inflammation in general, plus changes in calcium regulation, and altered cytoskeletal organization and microtubule dynamics in the left ventricle. While ejection fraction, fractional shortening, cardiac output, and isovolumic contraction time remained unchanged following E-vapor aerosols exposure, the nicotine-containing base and test aerosols caused an increase in isovolumic relaxation time similar to CS. A nicotine-related increase in pulse wave velocity and arterial stiffness was also observed, but it was significantly lower for base and test aerosols than for CS. These results demonstrate that in comparison with CS, E-vapor aerosols induce substantially lower biological responses associated with smoking-related cardiovascular diseases.NEW & NOTEWORTHY Analysis of key urinary oxidative stress markers and proinflammatory cytokines showed an absence of oxidative stress and inflammation in the animals exposed to E-vapor aerosols. Conversely, animals exposed to conventional cigarette smoke had high urinary levels of these markers. When compared with conventional cigarette smoke, E-vapor aerosols induced smaller atherosclerotic plaque surface area and volume. Systolic and diastolic cardiac function, as well as endothelial function, were further significantly less affected by electronic cigarette aerosols than conventional cigarette smoke. Molecular analysis demonstrated that E-vapor aerosols induce significantly smaller transcriptomic dysregulation in the heart and aorta compared with conventional cigarette smoke.

Blood Pressure in De Novo Heart Transplant Recipients Treated With Everolimus Compared With a Cyclosporine-based Regimen: Results From the Randomized SCHEDULE Trial

BACKGROUND

Systemic hypertension is prevalent in heart transplant recipients and has been partially attributed to treatment with calcineurin inhibitors (CNIs). SCandinavian HEart transplant De-novo stUdy with earLy calcineurin inhibitors avoidancE trial was the first randomized trial to study early withdrawal of CNIs in de novo heart transplant recipients, comparing an everolimus-based immunosuppressive regimen with conventional CNI-based treatment. As a prespecified secondary endpoint, blood pressure was repeatedly compared across treatment arms.

METHODS

The The SCandinavian HEart transplant De-novo stUdy with earLy calcineurin inhibitors avoidancE trial was a prospective, multicenter, randomized, controlled, parallel-group, open-label trial in de novo adult heart transplant recipients, undertaken at transplant centers in Scandinavia. Blood pressure was assessed with 24-hour ambulatory blood pressure monitoring up to 3 years after heart transplantation (HTx) in 83 patients.

RESULTS

Overall, systolic blood pressure fell with time, from 138 ± 15 mm Hg 2 weeks after HTx to 134 ± 11 mm Hg after 12 months and 132 ± 14 mm Hg after 36 months (P = 0.003). Diastolic blood pressure did not change over time. After 12 months, there was a numerically larger fall in systolic blood pressure in the everolimus arm (between-group difference 8 mm Hg; P = 0.053), and after 36 months, there was a significant between group difference of 13 mm Hg (P = 0.02) in favor of everolimus.

CONCLUSIONS

In this first, randomized trial with early CNI avoidance in de novo HTx recipients, we observed a modest fall in systolic blood pressure over the first 1 to 3 years after transplantation. The fall in systolic blood pressure was more pronounced in patients allocated to everolimus.

Hypertension: a new treatment for an old disease? Targeting the immune system

Arterial hypertension represents a serious public health problem, being a major cause of morbidity and mortality worldwide. The availability of many antihypertensive therapeutic strategies still fails to adequately treat around 20% of hypertensive patients, who are considered resistant to conventional treatment. In the pathogenesis of hypertension, immune system mechanisms are activated and both the innate and adaptive immune responses play a crucial role. However, what, when and how the immune system is triggered during hypertension development is still largely undefined. In this context, this review highlights scientific advances in the manipulation of the immune system in order to attenuate hypertension and end-organ damage. Here, we discuss the potential use of immunosuppressants and immunomodulators as pharmacological tools to control the activation of the immune system, by non-specific and specific mechanisms, to treat hypertension and improve end-organ damage. Nevertheless, more clinical trials should be performed with these drugs to establish their therapeutic efficacy, safety and risk-benefit ratio in hypertensive conditions. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Comparing everolimus-based immunosuppression with reduction or withdrawal of calcineurin inhibitor reduction from six months after heart transplantation: the randomized MANDELA study

In the 12-month, open-label MANDELA study, patients were randomized at month 6 after heart transplantation to (i) convert to calcineurin inhibitor (CNI)-free immunosuppression with everolimus (EVR), mycophenolic acid and steroids (CNI-free, n=71), or to (ii) continue reduced-exposure CNI, with EVR and steroids (EVR/redCNI, n=74). Tacrolimus was administered in 48.8% of EVR/redCNI patients and 52.6% of CNI-free patients at radomization. Both strategies improved and stabilized renal function based on the primary endpoint (estimated GFR at month 18 post-transplant post-randomization) with superiority of the CNI-free group versus EVR/redCNI : mean 64.1mL/min/1.73m2 versus 52.9mL/min/1.73m2 ; difference +11.3mL/min/1.73m2 (p<0.001). By month 18, estimated GFR had increased by ≥10mL/min/1.732 in 31.8% and 55.2% of EVR/redCNI and CNI-free patients, respectively, and by ≥25 mL/min/1.73m2 in 4.5% and 20.9%. Rates of biopsy-proven acute rejection (BPAR) were 6.8% and 21.1%; all cases were without hemodynamic compromise. BPAR was less frequent with EVR/redCNI versus the CNI-free regimen (p=0.015); 6/15 episodes in CNI-free patients occurred with EVR concentration <5ng/mL. Rates of adverse events and associated discontinuations were comparable EVR/redCNI from month 6 achieved stable renal function with infrequent BPAR. One-year renal function can be improved by early conversion to EVR-based CNI-free therapy but requires close EVR monitoring. This article is protected by copyright. All rights reserved.

Association Between Renal Dysfunction and Major Adverse Cardiac Events After Liver Transplantation: Evidence from an International Randomized Trial of Everolimus-Based Immunosuppression

Background

Prospective evidence is lacking regarding the association between renal dysfunction and cardiovascular events after liver transplantation.

Material/Methods

Data were analyzed post hoc regarding renal function and major adverse cardiac events in a two-year prospective trial of de novo liver transplant recipients randomized at 30 days post-transplant to (i) everolimus [EVR]/reduced tacrolimus [EVR/rTAC] (ii) EVR with tacrolimus discontinued [TAC Elimination] or (iii) standard tacrolimus [TAC Control].

Results

By month 24 post-transplant, 32/716 patients had experienced a first major cardiac event (4.5%): 4.1% (10/245), 2.2% (5/229) and 7.0% (17/242) of patients in the EVR/rTAC, TAC Elimination and TAC Control groups, respectively (p=0.043). The cumulative eGFR area under the curve (AUC) from randomization to month 24 was 119 706, 123 082, and 105 946 mL in the EVR/rTAC, TAC Elimination, and TAC Control groups, respectively, corresponding to a mean eGFR AUC of 82.4, 83.0, and 71.9 mL/min/1.73 m². Cox regression modeling showed that mean eGFR AUC was inversely associated with time to first major cardiac event: the hazard ratio per mL/min/1.73 m² was −0.0000015 [95% CI −0.00000078; −0.0000024] (p<0.001).

Conclusions

These findings confirm retrospective evidence that the risk of major cardiac events increases with deteriorating renal function after liver transplantation and demonstrate the need for careful cardiovascular risk management in patients with renal impairment. Immunosuppression based on everolimus with tacrolimus withdrawal, or to a lesser extent tacrolimus reduction, improves both renal function and the risk of major cardiac events compared to standard tacrolimus therapy in liver transplant recipients.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Rapamycin attenuates pathological hypertrophy caused by an absence of trabecular formation

Cardiac trabeculae are mesh-like muscular structures within ventricular walls. Subtle perturbations in trabeculation are associated with many congenital heart diseases (CHDs), and complete failure to form trabeculae leads to embryonic lethality. Despite the severe consequence of an absence of trabecular formation, the exact function of trabeculae remains unclear. Since ErbB2 signaling plays a direct and essential role in trabecular initiation, in this study, we utilized the erbb2 zebrafish mutant as a model to address the function of trabeculae in the heart. Intriguingly, we found that the trabeculae-deficient erbb2 mutant develops a hypertrophic-like (HL) phenotype that can be suppressed by inhibition of Target of Rapamycin (TOR) signaling in a similar fashion to adult mammalian hearts subjected to mechanical overload. Further, cell transplantation experiments demonstrated that erbb2 mutant cells in an otherwise wildtype heart did not undergo hypertrophy, indicating that erbb2 mutant HL phenotypes are due to a loss of trabeculae. Together, we propose that trabeculae serve to enhance contractility and that defects in this process lead to wall-stress induced hypertrophic remodeling.

Uric acid is an independent predictor of cardiac allograft vasculopathy after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a major complication after heart transplantation (HT). Uric acid (UA) may play a role in CAV due to its role in stimulating T-cell-mediated immunity. Sirolimus is associated with CAV attenuation through a number of mechanisms, including immune-mediated effects. We aimed to determine whether UA is an independent predictor of CAV and whether conversion to sirolimus as primary immunosuppression modulates UA levels.

METHODS

We retrospectively analyzed a cohort of 224 patients who underwent HT between 2004 and 2015 and had serial coronary intravascular ultrasound (IVUS) studies. Serum UA levels were measured at baseline and last follow-up IVUS in all participants. CAV progression was assessed by measuring the change in plaque volume (ΔPV) and plaque index (ratio of plaque volume to vessel volume [ΔPI]) between last follow-up and baseline IVUS after correction for time of follow-up.

RESULTS

Patients with high (≥7 mg/dl) compared with low (<7 mg/dl) UA had increased median ΔPV (0.33 [interquartile range 0.08 to 0.93] vs 0.07 [-0.17 to 0.38] mm³/mm/year; p < 0.001) and ΔPI (2.0% [0.31% to 3.9%] vs 0.33% [-1.2% to 2.0%]; p < 0.001). Elevated UA levels were associated with a significantly increased risk of developing significant CAV progression (ΔPV >0.50 mm³/mm) (hazard ratio 2.2, 95% confidence interval 1.1 to 4.6; p = 0.037). Sirolimus resulted in decreased UA levels (5.8 ± 1.4 vs 5.2 ± 1.5; p = 0.002) and patients converted to sirolimus and had low UA levels had the least CAV progression (p < 0.001). After adjustment for potential confounders, change in UA level was also an independent predictor of CAV progression.

CONCLUSIONS

UA is an independent predictor of CAV after HT. Sirolimus is associated with decreased UA levels and may explain one of the mechanisms by which sirolimus attenuates CAV progression.

Cardiovascular Parameters to 2 years After Kidney Transplantation Following Early Switch to Everolimus Without Calcineurin Inhibitor Therapy: An Analysis of the Randomized ELEVATE Study

BACKGROUND

Mammalian target of rapamycin inhibitors may confer cardioprotective advantages, but clinical data are limited.

METHODS

In the open-label ELEVATE trial, kidney transplant patients were randomized at 10 to 14 weeks after transplant to convert from calcineurin inhibitor (CNI) to everolimus or remain on standard CNI therapy. Prespecified end points included left ventricular mass index and, in a subpopulation of patients, arterial stiffness as measured by pulse wave velocity.

RESULTS

The mean change in left ventricular mass index from randomization was similar with everolimus versus CNI (month 24, -4.37 g/m versus -5.26 g/m; mean difference, 0.89 [p = 0.392]). At month 24, left ventricular hypertrophy was present in 41.7% versus 37.7% of everolimus and CNI patients, respectively. Mean pulse wave velocity remained stable with both everolimus (mean change from randomization to month 12, -0.24 m/s; month 24, -0.03 m/s) and CNI (month 12, 0.11 m/s; month 24, 0.16 m/s). The change in mean ambulatory nighttime blood pressure from randomization showed a benefit for diastolic pressure at month 12 (P = 0.039) but not at month 24. Major adverse cardiac events occurred in 1.1% and 4.2% of everolimus-treated and CNI-treated patients, respectively, by month 12 (P = 0.018) and 2.3% (8/353) and 4.5% by month 24 (P = 0.145).

CONCLUSIONS

Overall, these data do not suggest a clinically relevant effect on cardiac end points after early conversion from CNI to a CNI-free everolimus-based regimen.

Early Conversion From Calcineurin Inhibitor- to Everolimus-Based Therapy Following Kidney Transplantation: Results of the Randomized ELEVATE Trial

In a 24-month, multicenter, open-label, randomized trial, 715 de novo kidney transplant recipients were randomized at 10-14 weeks to convert to everolimus (n = 359) or remain on standard calcineurin inhibitor (CNI) therapy (n = 356; 231 tacrolimus; 125 cyclosporine), all with mycophenolic acid and steroids. The primary endpoint, change in estimated glomerular filtration rate (eGFR) from randomization to month 12, was similar for everolimus versus CNI: mean (standard error) 0.3(1.5) mL/min/1.73² versus -1.5(1.5) mL/min/1.73² (p = 0.116). Biopsy-proven acute rejection (BPAR) at month 12 was more frequent under everolimus versus CNI overall (9.7% vs. 4.8%, p = 0.014) and versus tacrolimus-treated patients (2.6%, p < 0.001) but similar to cyclosporine-treated patients (8.8%, p = 0.755). Reporting on de novo donor-specific antibodies (DSA) was limited but suggested more frequent anti-HLA Class I DSA under everolimus. Change in left ventricular mass index was similar. Discontinuation due to adverse events was more frequent with everolimus (23.6%) versus CNI (8.4%). In conclusion, conversion to everolimus at 10-14 weeks posttransplant was associated with renal function similar to that with standard therapy overall. Rates of BPAR were low in all groups, but lower with tacrolimus than everolimus.

Effect of Immunosuppressive Treatment on Carotid Atherosclerosis in Renal Transplant Recipients

BACKGROUND

The aim of this study was to compare the effect of immunosuppressive regimens using either mammalian target of rapamycin inhibitors (mTORi) or calcineurin inhibitors (CNI) on the risk of atherosclerosis in renal transplant patients.

MATERIALS AND METHODS

The study involved a group of 24 recipients treated with mTORi (mTORi group) and a group of 20 recipients treated with immunosuppressive regimen based on CNI (CNI group). Laboratory and clinical markers of cardiovascular risk in both groups were investigated. Carotid atherosclerosis was evaluated by measurement of the intima media thickness (IMT) of the common and internal carotid artery walls and detection of carotid plaques by a high-resolution ultrasonography. The study was performed 3-24 years after transplantation.

RESULTS

The mTORi group showed higher level of total cholesterol (242 vs 201 mg/dL; P < .004), low-density lipoprotein cholesterol (140 vs 116 mg/dL; P < .05), and triglycerides (226 vs 168 mg/dL; P < .01). Posttransplant diabetes developed in 34% of mTORi group compared with 25% in the CNI group. The mean of IMT (left and right) of common and internal carotid arteries was similar in both groups. Carotid plaques were detected in 46% of patients from the mTORi group and 25% from CNI group (P < .02). The presence of carotid plaques combined with an IMT of >0.9 mm were associated with male gender, mTORi treatment (P = .03), and cardiovascular events. The incidence of coronary heart disease was higher in mTORi group than in CNI group (53% vs 20%; P = .03).

CONCLUSIONS

There was not beneficial effect of immunosuppressive treatment with mTORi on carotid atherosclerosis in renal transplant patients.

Antianginal Therapy for Stable Ischemic Heart Disease

Chronic angina pectoris is associated with considerable morbidity and mortality, especially if treated suboptimally. For many patients, aggressive pharmacologic intervention is necessary in order to alleviate anginal symptoms. The optimal treatment of stable ischemic heart disease (SIHD) should be the prevention of angina and ischemia, with the goal of maximizing both quality and quantity of life. In addition to effective risk factor modification with lifestyle changes, intensive pharmacologic secondary prevention is the therapeutic cornerstone in managing patients with SIHD. Current guidelines recommend a multifaceted therapeutic approach with β-blockers as first-line treatment. Another important pharmacologic intervention for managing SIHD is nitrates. Nitrates can provide both relief of acute angina and can be used prophylactically before exposure to known triggers of myocardial ischemia to prevent angina. Additional therapeutic options include calcium channel blockers and ranolazine, an inhibitor of the late inward sodium current, that can be used alone or in addition to nitrates or β-blockers when these agents fail to alleviate symptoms. Ranolazine appears to be particularly effective for patients with microvascular angina and endothelial dysfunction. In addition, certain antianginal therapies are approved in Europe and have been shown to improve symptoms, including ivabradine, nicorandil, and trimetazidine; however, these have yet to be approved in the United States. Ultimately, there are several different medications available to the physician for managing the patient with SIHD having chronic angina, when either used alone or in combination. The purpose of this review is to highlight the most important therapeutic approaches to optimizing contemporary treatment in response to individual patient needs.

Oral sirolimus: A possible treatment for refractory angina pectoris in the elderly

Refractory angina pectoris (RAP) is a clinical problem, frequently encountered in the elderly, associated with high health-care costs. Until recently, the goal of RAP treatment aimed at improving the quality of life (QoL) because it was thought that mortality rates were not different between stable angina pectoris and RAP. Our purpose was at determining whether any mortality rate difference exists and whether any novel therapeutical solution might be translated into clinical practice. We therefore performed a literature review to assess current optimal treatment of RAP patients, including all studies involving the use of oral sirolimus and stents, although no consistent evidence was found for any specific treatment to improve survival, apart from minor QoL amelioration. A large mortality difference was seen between RAP and stable angina pectoris. On the other hand, therapeutic approaches to RAP patients showed frequent complications and several contraindications, depending on the procedure. We propose to inhibit instead of stimulating angiogenesis, by giving oral sirolimus, an immunosuppressive drug, thereby decreasing the atherosclerotic process and its evolution. Sirolimus was shown to decrease left ventricular mass (thus indirectly decreasing myocardial oxygen needs and consumption). It might stop and, in some cases, even enable regression of plaque progression. Sirolimus side effects are mild to moderate and wash-out rapidly at treatment discontinuation. Compared with current therapies sirolimus treatment is more health-care cost efficient. It should be important to design a trial in RAP patients powered to reduce mortality and QoL increase.

Everolimus Attenuates Myocardial Hypertrophy and Improves Diastolic Function in Heart Transplant Recipients

Everolimus (EVL), one of the mammalian targets of rapamycin, is a next generation immunosuppressant that may have accessory anti-proliferative effects in heart transplant (HTx) recipients. However, little is known about the clinical relationship between EVL and regression of cardiac hypertrophy. A total of 42 HTx recipients received EVL therapy at post-HTx 150 days on median and had been followed at our institute for > 1 year between 2008 and 2014 [EVL (+) group]. We also observed 18 patients without EVL from post-HTx 150 days for 1 year [EVL (-) group]. There were no significant differences in baseline variables between the two groups. Left ventricular mass index (LVMI) and the ratio of early transmitral filling velocity to the peak early diastolic mitral annular motion velocity (E/e') decreased significantly during 1-year EVL treatment compared with the EVL (-) group. There were no differences in blood pressure and medications between the 2 groups. Improvement of LVMI and the E/e' ratio was not associated with trough levels of calcineurin inhibitors or EVL, but correlated with each baseline value. In conclusion, this EVL-incorporated immunosuppressant regimen attenuated cardiac hypertrophy as well as diastolic dysfunction in HTx recipients.

17ß-Estradiol regulates mTORC2 sensitivity to rapamycin in adaptive cardiac remodeling

Adaptive cardiac remodeling is characterized by enhanced signaling of mTORC2 downstream kinase Akt. In females, 17ß-estradiol (E2), as well as Akt contribute essentially to sex-related premenopausal cardioprotection. Pharmacologic mTOR targeting with rapamycin is increasingly used for various clinical indications, yet burdened with clinical heterogeneity in therapy responses. The drug inhibits mTORC1 and less-so mTORC2. In male rodents, rapamycin decreases maladaptive cardiac hypertrophy whereas it leads to detrimental dilative cardiomyopathy in females. We hypothesized that mTOR inhibition could interfere with 17β-estradiol (E2)-mediated sexual dimorphism and adaptive cell growth and tested responses in murine female hearts and cultured female cardiomyocytes. Under physiological in vivo conditions, rapamycin compromised mTORC2 function only in female, but not in male murine hearts. In cultured female cardiomyocytes, rapamycin impaired simultaneously IGF-1 induced activation of both mTOR signaling branches, mTORC1 and mTORC2 only in presence of E2. Use of specific estrogen receptor (ER)α- and ERβ-agonists indicated involvement of both estrogen receptors (ER) in rapamycin effects on mTORC1 and mTORC2. Classical feedback mechanisms common in tumour cells with upregulation of PI3K signaling were not involved. E2 effect on Akt-pS473 downregulation by rapamycin was independent of ERK as shown by sequential mTOR and MEK-inhibition. Furthermore, regulatory mTORC2 complex defining component rictor phosphorylation at Ser1235, known to interfere with Akt-substrate binding to mTORC2, was not altered. Functionally, rapamycin significantly reduced trophic effect of E2 on cell size. In addition, cardiomyocytes with reduced Akt-pS473 under rapamycin treatment displayed decreased SERCA2A mRNA and protein expression suggesting negative functional consequences on cardiomyocyte contractility. Rictor silencing confirmed regulation of SERCA2A expression by mTORC2 in E2-cultured female cardiomyocytes. These data highlight a novel modulatory function of E2 on rapamycin effect on mTORC2 in female cardiomyocytes and regulation of SERCA2A expression by mTORC2. Conceivably, rapamycin abrogates the premenopausal “female advantage”.

Impact of caloric restriction on myocardial ischaemia/reperfusion injury and new therapeutic options to mimic its effects

Caloric restriction (CR) is the most reliable intervention to extend lifespan and prevent age-related disorders in various species from yeast to rodents. Short- and long-term CR confers cardio protection against ischaemia/reperfusion injury in young and even in aged rodents. A few human trials suggest that CR has the potential to mediate improvement of cardiac or vascular function and induce retardation of cardiac senescence also in humans. The underlying mechanisms are diverse and have not yet been clearly defined. Among the known mediators for the benefits of CR are NO, the AMP-activated PK, sirtuins and adiponectin. Mitochondria, which play a central role in such complex processes within the cell as apoptosis, ATP-production or oxidative stress, are centrally involved in many aspects of CR-induced protection against ischaemic injury. Here, we discuss the relevant literature regarding the protection against myocardial ischaemia/reperfusion injury conferred by CR. Furthermore, we will discuss drug targets to mimic CR and the possible role of calorie restriction in preserving cardiovascular function in humans.

mTOR inhibitors and dyslipidemia in transplant recipients: a cause for concern?

Post-transplant dyslipidemia is exacerbated by mammalian target of rapamycin (mTOR) inhibitors. Early clinical trials of mTOR inhibitors used fixed dosing with no concomitant reduction in calcineurin inhibitor (CNI) exposure, leading to concerns when consistent and marked dyslipidemia was observed. With use of modern concentration-controlled mTOR inhibitor regimens within CNI-free or reduced-exposure CNI regimens, however, the dyslipidemic effect persists but is less pronounced. Typically, total cholesterol levels are at the upper end of normal, or indicate borderline risk, in kidney and liver transplant recipients, and are lower in heart transplant patients under near-universal statin therapy. Of note, it is possible that mTOR inhibitors may offer a cardioprotective effect. Experimental evidence for delayed progression of atherosclerosis is consistent with evidence from heart transplantation that coronary artery intimal thickening and the incidence of cardiac allograft vasculopathy are reduced with everolimus versus cyclosporine therapy. Preliminary data also indicate that mTOR inhibitors may improve arterial stiffness, a predictor of cardiovascular events, and may reduce ventricular remodeling and decrease left ventricular mass through an anti-fibrotic effect. Post-transplant dyslipidemia under mTOR inhibitor therapy should be monitored and managed closely, but unless unresponsive to therapy should not be regarded as a barrier to its use.

Sirolimus Immunoprophylaxis and Renal Histological Changes in Long-Term Cardiac Transplant Recipients

Background: The effects of sirolimus (SIR), as a substitution for calcineurin inhibitor (CNI) immunoprophylaxis, on renal function in very-long-term cardiac transplant recipients have been a matter of controversy. Objective: To assess the impacts of SIR as a substitution for CNI on renal function up to 24 months in long-term cardiac recipients as well as the renal histological changes in patients with suspected CNI-induced nephrotoxicity. Methods: A total of 23 cardiac transplant recipients aged 57.7 ± 11.2 years, 91 months post–cardiac transplantation were recruited; 15 patients were randomized to CNI-free immune suppression with SIR, and 8 patients were allocated to continue their CNI regimens. Serum creatinine and calculated serum creatinine clearance were measured at prespecified time points up to 24 months. Renal structure and function were assessed by renal biopsies, renal ultrasound, and magnetic resonance imaging at baseline. Results: There were no significant changes in creatinine clearance during the course of the study in patients treated with SIR. However, SIR-treated patients exhibited a significant decrease in 24-hours and nighttime systolic and diastolic blood pressures. Typical findings of significant hypertensive renal disease were detected in 9 of the 11 (82%) patients. Features of chronic CNI toxicity were detected in 6 (55%) patients. Conclusions: There is a very high rate of hypertensive renal disease concomitantly with some degree of CNI toxicity in long-term cardiac transplant recipients with renal dysfunction. This very high rate of hypertension-related disease may limit the impact of SIR on improving renal function long term following cardiac transplantation.

Antibiotics acting as neuroprotectants via mechanisms independent of their anti-infective activities

This review considers available evidence that some antibiotics have ancillary neuroprotective effects. Notably, β-lactam antibiotics are believed to increase the expression of glutamate transporter GLT1, potentially relieving the neurological excitotoxicity that characterizes disorders like amyotrophic lateral sclerosis. Minocycline has shown promise in reducing the severity of a number of neurological diseases, including multiple sclerosis, most likely by reducing apoptosis and the expression of inflammatory mediators in the brain. Rapamycin inhibits the activity of a serine/threonine protein kinase that has a role in the pathogenesis of numerous neurologic diseases. Herein we examine the unique neuroprotective aspects of these drugs originally developed as anti-infective agents.

Sex-specific mTOR signaling determines sexual dimorphism in myocardial adaptation in normotensive DOCA-salt model

The deoxycorticosterone acetate (DOCA)-salt mouse model exhibits adverse cardiac remodeling in male mice and cardiac protection in female mice, even when blood pressure is normalized. We hypothesized that intact mammalian target of rapamycin (mTOR) signaling is necessary for cardiac protection in females. We first tested sex differences and intracellular signaling after mTOR targeting with rapamycin in wild-type mice. Radio-telemetric blood pressure was maintained at normal for 6 weeks. Rapamycin significantly reduced left ventricular hypertrophy, preserved ejection fraction, inhibited fibrosis, and maintained capillary structure in male mice. Decreased mTORC1 and increased mTORC2 activity were detected in rapamycin-treated male mice compared with vehicle controls. In contrast, female mice developed dilative left ventricular hypertrophy, cardiac fibrosis, and capillary loss similar to DOCA-salt females lacking the estrogen receptor β (ERβ(-/-)) that we described earlier. Because rapamycin downregulated ERβ in female mice, we next studied ERβ(-/-) normotensive DOCA-salt females. Vehicle-treated wild-type females maintained their high constitutive mTORC1 and mTORC2 in response to DOCA-salt. In contrast to males, both mTORCs were decreased by rapamycin, in particular mTORC2 by 60%. ERβ(-/-) DOCA-salt females showed similar mTORC1 and mTORC2 response patterns. We suggest that ERβ-dependent regulation involves sex-specific use of mTOR signaling branches. Maintenance of both mTORC1 and mTORC2 signaling seems to be essential for adaptive cardiac remodeling in females and supports a rationale for sex-specific therapeutic strategies in left ventricular hypertrophy.

Target of rapamycin (TOR)-based therapy for cardiomyopathy: evidence from zebrafish and human studies

Rapamycin is a U.S. Food and Drug Administration-approved drug for the prevention of immunorejection following organ transplantation. Pharmacological studies suggest a potential new application of rapamycin in attenuating cardiomyopathy, but the potential for this application is not yet supported by genetic studies of genes in target of rapamycin (TOR) signaling in rodents. Recently, supporting genetic evidence was presented in zebrafish using two adult cardiomyopathy models. By characterizing a heterozygous zebrafish target of rapamycin (ztor) mutant, the therapeutic effect of long-term TOR signaling inhibition was demonstrated. Dose- and stage-dependent functions of TOR signaling provide an explanation for the seemingly contradictory results obtained in genetic studies of TOR components in rodents. The results from the zebrafish studies, together with the supporting preliminary clinical studies, suggested that TOR signaling inhibition should be further pursued as a novel therapeutic strategy for cardiomyopathy. Future directions for developing TOR-based therapy include assessing the long-term benefits of rapamycin as a candidate drug for heart failure patients, defining the dynamic activity of TOR, exploring the impacts of TOR signaling manipulation in different models of cardiomyopathies, and elucidating the downstream signaling branches that confer the therapeutic effects of TOR signaling inhibition.

Cardiomyocyte death: mechanisms and translational implications

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Although treatments have improved, development of novel therapies for patients with CVD remains a major research goal. Apoptosis, necrosis, and autophagy occur in cardiac myocytes, and both gradual and acute cell death are hallmarks of cardiac pathology, including heart failure, myocardial infarction, and ischemia/reperfusion. Pharmacological and genetic inhibition of autophagy, apoptosis, or necrosis diminishes infarct size and improves cardiac function in these disorders. Here, we review recent progress in the fields of autophagy, apoptosis, and necrosis. In addition, we highlight the involvement of these mechanisms in cardiac pathology and discuss potential translational implications.

Neuromuscular ultrasonography: quantifying muscle and nerve measurements

Neuromuscular ultrasonography can be used both descriptively and quantitatively in the evaluation of patients with neuromuscular disorders. This article reviews the quantitative use of this technology, particularly measurements of the size and echogenicity of nerve and muscle, as a tool for assessing the severity, progression, and response of these tissues to therapeutic interventions. Neuromuscular ultrasonography has several features, including portability and noninvasiveness, that make it an attractive research tool for advancing the diagnosis and treatment of neuromuscular disorders.

Local application of rapamycin inhibits vein graft restenosis in rabbits

OBJECTIVE

The aim of this study was to investigate whether local application of rapamycin reduced neointimal formation in a rabbit model of venous disease.

METHODS

Each rabbit (n = 30; 2.5-3.5 kg) received a treated and a control graft. For the treated graft, 0.3 rapamycin mg was applied locally in Pluronic gel. The control graft received only the Pluronic gel. Grafts were harvested at 28 days for morphometric, immunohistochemical, and flow cytometry analysis.

RESULTS

In the control group, the intimal thickness was 63.72 ± 14.0 μm; in treated group, it was 77.76 ± 14.9 μm (P < .05). Immunohistochemically, proliferation cell nuclear antigen-positive cells were present in the control group and in the treatment group but not in normal external jugular veins. The control group showed much stronger expression than the treatment group (P < .05). Flow cytometry showed, among the control group, decreased G(0)G(1)-stage cells and increased S/G(2)M-stage cells. Among the treatment group, S/G(2)M stage cells were decreased compared with the control. The progression indexes of the control and treatment groups were 29.3 ± 7.15 and 20.1 ± 9.48, respectively, a remarkable decrease (P < .05). Proliferating cells in the control group were apparently inhibited by rapamycin. The treatment group showed positive staining for P27(kip1), but neither the control group nor the normal external jugular veins showed positive results (P < .05). The degree of reduction in intimal thickness and inhibition of proliferating cells in the treatment group correlated with the expression of P27(kip1).

CONCLUSIONS

We observed that perivascular application of rapamycin inhibited neointimal hyperplasia of vein grafts in a rabbit model, an effect that appeared to result from increased P27(kip1) expression.

Haploinsufficiency of target of rapamycin attenuates cardiomyopathies in adult zebrafish

RATIONALE

Although a cardioprotective function of target of rapamycin (TOR) signaling inhibition has been suggested by pharmacological studies using rapamycin, genetic evidences are still lacking. We explored adult zebrafish as a novel vertebrate model for dissecting signaling pathways in cardiomyopathy.

OBJECTIVE

We generated the second adult zebrafish cardiomyopathy model induced by doxorubicin. By genetically analyzing both the doxorubicin and our previous established anemia-induced cardiomyopathy models, we decipher the functions of TOR signaling in cardiomyopathies of different etiology.

METHODS AND RESULTS

Along the progression of both cardiomyopathy models, we detected dynamic TOR activity at different stages of pathogenesis as well as distinct effects of TOR signaling inhibition. Nevertheless, cardiac enlargement in both models can be effectively attenuated by inhibition of TOR signaling through short-term rapamycin treatment. To assess the long-term effects of TOR reduction, we used a zebrafish target of rapamycin (ztor) mutant identified from an insertional mutagenesis screen. We show that TOR haploinsufficiency in the ztor heterozygous fish improved cardiac function, prevented pathological remodeling events, and ultimately reduced mortality in both adult fish models of cardiomyopathy. Mechanistically, these cardioprotective effects are conveyed by the antihypertrophy, antiapoptosis, and proautophagy function of TOR signaling inhibition.

CONCLUSIONS

Our results prove adult zebrafish as a conserved novel vertebrate model for human cardiomyopathies. Moreover, we provide the first genetic evidence to demonstrate a long-term cardioprotective effect of TOR signaling inhibition on at least 2 cardiomyopathies of distinct etiology, despite dynamic TOR activities during their pathogenesis.

Cardiac allograft hypertrophy is associated with impaired exercise tolerance after heart transplantation

BACKGROUND

Exercise performance, an important aspect of quality of life, remains limited after heart transplantation (HTx). This study examines the effect of cardiac allograft remodeling on functional capacity after HTx.

METHODS

The total cohort of 117 HTx recipients, based on echocardiographic determination of left ventricle mass and relative wall thickness at 1 year after HTx, was divided into 3 groups: (1) NG, normal geometry; (2) CR, concentric remodeling; and (3) CH, concentric hypertrophy. Cardiopulmonary exercise testing was performed 5.03 ± 3.08 years after HTx in all patients. Patients with acute rejection or significant graft vasculopathy were excluded.

RESULTS

At 1 year post-HTx, 30% of patients had CH, 55% had CR and 15% had NG. Exercise tolerance, measured by maximum achieved metabolic equivalents (4.62 ± 1.44 vs 5.52 ± 0.96 kcal/kg/h), normalized peak Vo(2) (52 ± 14% vs 63 ± 12%) and Ve/Vco(2) (41 ± 17 vs 34 ± 6), was impaired in the CH group compared with the NG group. A peak Vo(2) ≤14 ml/kg/min was found in 6%, 22% and 48% of patients in the NG, CR and CH groups, respectively (p = 0.01). The CH pattern was associated with a 7.4-fold increase in relative risk for a peak Vo(2) ≤14 ml/kg/min compared with NG patients (95% confidence interval 1.1 to 51.9, p = 0.001). After multivariate analysis, a 1-year CH pattern was independently associated with a reduced normalized peak Vo(2) (p = 0.018) and an elevated Ve/Vco(2) (p = 0.035).

CONCLUSIONS

The presence of CH at 1 year after HTx is independently associated with decreased normalized peak Vo(2) and increased ventilatory response in stable heart transplant recipients. The identification of CH, a potentially reversible mechanism of impairment in exercise capacity after HTx, may have major clinical implications.

Regression of left ventricular hypertrophy in kidney transplant recipients: the potential role for inhibition of mammalian target of rapamycin

Left ventricular hypertrophy (LVH) contributes to elevated cardiac mortality with graft function in renal transplant recipients. Antihypertensive therapy, and especially angiotensin-converting enzyme (ACE) inhibitors, proved to be effective in regressing the LVH of renal transplant recipients, at least in part by interacting with immunosuppressive agents, thus raising the possibility that immunosuppressive therapy might affect changes in the left ventricular mass (LVM) of recipients. This review mainly focuses on the potential role of mammalian target of rapamycin (mTOR) inhibition to regress cardiac hypertrophy in both experimental models and in the clinical setting. We comment on the results of experimental studies conducted on animal models, which showed regression of cardiac hypertrophy by sirolimus (SRL). We also discuss clinical studies that show that conversion from calcineurin inhibitors to SRL is effective to achieve regression of LVH in both kidney and cardiac transplant recipients, mainly by reducing the true left ventricular wall hypertrophy.

Smooth muscle protein-22-mediated deletion of Tsc1 results in cardiac hypertrophy that is mTORC1-mediated and reversed by rapamycin

Constitutive activation of mammalian target of rapamycin complex 1 (mTORC1), a key kinase complex that regulates cell size and growth, is observed with inactivating mutations of either of the tuberous sclerosis complex (TSC) genes, Tsc1 and Tsc2. Tsc1 and Tsc2 are highly expressed in cardiovascular tissue but their functional role there is unknown. We generated a tissue-specific knock-out of Tsc1, using a conditional allele of Tsc1 and a cre recombinase allele regulated by the smooth muscle protein-22 (SM22) promoter (Tsc1c/cSM22cre+/-) to constitutively activate mTOR in cardiovascular tissue. Significant gene recombination (∼80%) occurred in the heart by embryonic day (E) 15, and reduction in Tsc1 expression with increased levels of phosphorylated S6 kinase (S6K) and S6 was observed, consistent with constitutive activation of mTORC1. Cardiac hypertrophy was evident by E15 with post-natal progression to heart weights of 142 ± 24 mg in Tsc1c/cSM22cre+/- mice versus 65 ± 14 mg in controls (P < 0.01). Median survival of Tsc1c/cSM22cre+/- mice was 24 days, with none surviving beyond 6 weeks. Pathologic and echocardiographic analysis revealed severe biventricular hypertrophy without evidence of fibrosis or myocyte disarray, and significant reduction in the left ventricular end-diastolic diameter (P < 0.001) and fractional index (P < 0.001). Inhibition of mTORC1 by rapamycin resulted in prolonged survival of Tsc1c/cSM22cre+/- mice, with regression of ventricular hypertrophy. These data support a critical role for the Tsc1/Tsc2-mTORC1-S6K axis in the normal development of cardiovascular tissue and also suggest possible therapeutic potential of rapamycin in cardiac disorders where pathologic mTORC1 activation occurs.

Mammalian target of rapamycin is a critical regulator of cardiac hypertrophy in spontaneously hypertensive rats

Evidence exists that protein kinase C and the mammalian target of rapamycin are important regulators of cardiac hypertrophy. We examined the contribution of these signaling kinases to cardiac growth in spontaneously hypertensive rats (SHRs). Systolic blood pressure was increased (P<0.001) at 10 weeks in SHRs versus Wistar-Kyoto controls (162+/-3 versus 128+/-1 mm Hg) and was further elevated (P<0.001) at 17 weeks in SHRs (184+/-7 mm Hg). Heart:body weight ratio was not different between groups at 10 weeks but was 22% greater (P<0.01) in SHRs versus Wistar-Kyoto controls at 17 weeks. At 10 weeks, activation of Akt and S6 ribosomal protein was greater (P<0.01) in SHRs but returned to normal by 17 weeks. In contrast, SHRs had protein kinase C activation only at 17 weeks. To determine whether mammalian target of rapamycin regulates the initial development of hypertrophy, rats were treated with rapamycin (2 mg/kg per day IP) or saline vehicle from 13 to 16 weeks of age. Rapamycin inhibited cardiac mammalian target of rapamycin in SHRs, as evidenced by reductions (P<0.001) in phosphorylation of S6 ribosomal protein and eukaryotic translation initiation factor-4E binding protein 1. Rapamycin treatment also reduced (P<0.001) heart weight and hypertrophy by 47% and 53%, respectively, in SHRs in spite of increased (P<0.001) systolic blood pressure versus untreated SHRs (213+/-8 versus 189+/-6 mm Hg). Atrial natriuretic peptide, brain natriuretic peptide, and cardiac function were unchanged between SHRs treated with rapamycin or vehicle. These data show that mammalian target of rapamycin is required for the development of cardiac hypertrophy evoked by rising blood pressure in SHRs.