Lipid metabolism in renal transplant patients receiving tacrolimus/sirolimus combination therapy

Brothers in Arms: ABCA1- and ABCG1-Mediated Cholesterol Efflux as Promising Targets in Cardiovascular Disease Treatment

Atherosclerosis is a leading cause of cardiovascular disease worldwide, and hypercholesterolemia is a major risk factor. Preventive treatments mainly focus on the effective reduction of low-density lipoprotein cholesterol, but their therapeutic value is limited by the inability to completely normalize atherosclerotic risk, probably due to the disease complexity and multifactorial pathogenesis. Consequently, high-density lipoprotein cholesterol gained much interest, as it appeared to be cardioprotective due to its major role in reverse cholesterol transport (RCT). RCT facilitates removal of cholesterol from peripheral tissues, including atherosclerotic plaques, and its subsequent hepatic clearance into bile. Therefore, RCT is expected to limit plaque formation and progression. Cellular cholesterol efflux is initiated and propagated by the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Their expression and function are expected to be rate-limiting for cholesterol efflux, which makes them interesting targets to stimulate RCT and lower atherosclerotic risk. This systematic review discusses the molecular mechanisms relevant for RCT and ABCA1 and ABCG1 function, followed by a critical overview of potential pharmacological strategies with small molecules to enhance cellular cholesterol efflux and RCT. These strategies include regulation of ABCA1 and ABCG1 expression, degradation, and mRNA stability. Various small molecules have been demonstrated to increase RCT, but the underlying mechanisms are often not completely understood and are rather unspecific, potentially causing adverse effects. Better understanding of these mechanisms could enable the development of safer drugs to increase RCT and provide more insight into its relation with atherosclerotic risk. SIGNIFICANCE STATEMENT: Hypercholesterolemia is an important risk factor of atherosclerosis, which is a leading pathological mechanism underlying cardiovascular disease. Cholesterol is removed from atherosclerotic plaques and subsequently cleared by the liver into bile. This transport is mediated by high-density lipoprotein particles, to which cholesterol is transferred via ATP-binding cassette transporters ABCA1 and ABCG1. Small-molecule pharmacological strategies stimulating these transporters may provide promising options for cardiovascular disease treatment.

Target of rapamycin inhibitors (TOR-I; sirolimus and everolimus) for primary immunosuppression in kidney transplant recipients

BACKGROUND

Kidney transplantation is the therapy of choice for many patients with end-stage kidney disease (ESKD) with an improvement in survival rates and satisfactory short term graft survival. However, there has been little improvement in long-term survival. The place of target of rapamycin inhibitors (TOR-I) (sirolimus, everolimus), which have different modes of action from other commonly used immunosuppressive agents, in kidney transplantation remains uncertain. This is an update of a review first published in 2006.

OBJECTIVES

To evaluate the short and long-term benefits and harms of TOR-I (sirolimus and everolimus) when used in primary immunosuppressive regimens for kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 20 September 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs in which drug regimens, containing TOR-I commenced within seven days of transplant, were compared to alternative drug regimens, were included without age restriction, dosage or language of report.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed study eligibility, risk of bias, and extracted data. Results were reported as risk ratios (RR) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) with 95% CI for continuous outcomes. Statistical analyses were performed using the random-effects model. The certainty of the evidence was assessed using GRADE MAIN RESULTS: Seventy studies (17,462 randomised participants) were included; eight studies included two comparisons to provide 78 comparisons. Outcomes were reported at six months to three years post transplant. Risk of bias was judged to be low for sequence generation in 25 studies, for allocation concealment in 23 studies, performance bias in four studies, detection bias in 65 studies, attrition bias in 45 studies, selective reporting bias in 48 studies, and for other potential bias in three studies. Risk of bias was judged to be at high risk of bias for sequence generation in two studies, allocation concealment in two studies, performance bias in 61 studies, detection bias in one study, attrition bias in four studies, for selective reporting bias in 11 studies and for other potential risk of bias in 46 studies. Compared with CNI and antimetabolite, TOR-I with antimetabolite probably makes little or no difference to death (RR 1.31, 95% CI 0.87 to 1.98; 19 studies) or malignancies (RR 0.86, 95% CI 0.50 to 1.48; 10 studies); probably increases graft loss censored for death (RR 1.32, 95% CI 0.96 to 1.81; 15 studies), biopsy-proven acute rejection (RR 1.60, 95% CI 1.25 to 2.04; 15 studies), need to change treatment (RR 2.42, 95% CI 1.88 to 3.11; 14 studies) and wound complications (RR 2.56, 95% CI 1.94 to 3.36; 12 studies) (moderate certainty evidence); but reduces CMV infection (RR 0.43, 95% CI 0.29 to 0.63; 13 studies) (high certainty evidence). Compared with antimetabolites and CNI, TOR-I with CNI probably makes little or no difference to death (RR 1.06, 95% CI 0.84 to 1.33; 31 studies), graft loss censored for death (RR 1.09, 95% CI 0.82 to 1.45; 26 studies), biopsy-proven acute rejection (RR 0.95, 95% CI 0.81 to 1.12; 24 studies); and malignancies (RR 0.83, 95% CI 0.64 to 1.07; 17 studies); probably increases the need to change treatment (RR 1.56, 95% CI 1.28 to 1.90; 25 studies), and wound complications (RR 1.56, 95% CI 1.28 to 1.91; 17 studies); but probably reduces CMV infection (RR 0.44, 95% CI 0.34 to 0.58; 25 studies) (moderate certainty evidence). Lower dose TOR-I and standard dose CNI compared with higher dose TOR-I and reduced dose CNI probably makes little or no difference to death (RR 1.07, 95% CI 0.64 to 1.78; 9 studies), graft loss censored for death (RR 1.09, 95% CI 0.54 to 2.20; 8 studies), biopsy-proven acute rejection (RR 0.87, 95% CI 0.67 to 1.13; 8 studies), and CMV infection (RR 1.42, 95% CI 0.78 to 2.60; 5 studies) (moderate certainty evidence); and may make little or no difference to wound complications (RR 0.95, 95% CI 0.53 to 1.71; 3 studies), malignancies (RR 1.04, 95% CI 0.36 to 3.04; 7 studies), and the need to change treatments (RR 1.18, 95% CI 0.58 to 2.42; 5 studies) (low certainty evidence). Lower dose of TOR-I compared with higher doses probably makes little or no difference to death (RR 0.84, 95% CI 0.67 to 1.06; 13 studies), graft loss censored for death (RR 0.92, 95% CI 0.71 to 1.19; 12 studies), biopsy-proven acute rejection (RR 1.26, 95% CI 1.10 to 1.43; 11 studies), CMV infection (RR 0.87, 95% CI 0.63 to 1.21; 9 studies), wound complications (RR 0.92, 95% CI 0.66 to 1.29; 7 studies), and malignancy (RR 0.84, 95% CI 0.54 to 1.32; 10 studies) (moderate certainty evidence); and may make little or no difference to the need to change treatments (RR 0.91, 95% CI 0.78 to 1.05; 10 studies) (low certainty evidence). It is uncertain whether sirolimus and everolimus differ in their effects on kidney function and lipid levels because the certainty of the evidence is very low based on a single small study with only three months of follow-up.

AUTHORS' CONCLUSIONS

In studies with follow-up to three years, TOR-I with an antimetabolite increases the risk of graft loss and acute rejection compared with CNI and an antimetabolite. TOR-I with CNI potentially offers an alternative to an antimetabolite with CNI as rates of graft loss and acute rejection are similar between interventions and TOR-I regimens are associated with a reduced risk of CMV infections. Wound complications and the need to change immunosuppressive medications are higher with TOR-I regimens. While further new studies are not required, longer-term follow-up data from participants in existing methodologically robust RCTs are needed to determine how useful immunosuppressive regimens, which include TOR-I, are in maintaining kidney transplant function and survival beyond three years.

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.

Cyclosporine, tacrolimus and sirolimus retain their distinct toxicity profiles despite low doses in the Symphony study

BACKGROUND

Reducing side effects of immunosuppressive regimens has become a priority in transplantation medicine because of the large number of patients and grafts that succumb to infection in the short term and cardiovascular disease in the long term. The Symphony study was a 12-month prospective, randomized, open-label, multi-centre, four parallel arm study that aimed to evaluate the safety and efficacy of low-dose immunosuppressive regimens compared with a standard-dose regimen in renal transplant recipients. This sub-analysis focuses on specific toxicities observed with the low-dose regimens.

METHODS

Adult patients (n = 1645) scheduled to undergo renal transplantation received low-dose cyclosporine (CsA), tacrolimus (Tac) or sirolimus (SRL) in addition to daclizumab induction or standard-dose cyclosporine without induction. All patients received mycophenolate mofetil and corticosteroids. We evaluated the incidence of adverse events (AEs), tested specific group differences and assessed the relationship of selected AEs with drug levels.

RESULTS

The four arms had similar incidences of AEs, but serious AEs were more common with low-dose SRL and led to more discontinuations. Infections were the most common AEs, with the highest incidence in the standard-dose CsA group, in particular, cytomegalovirus (CMV) infections. Low-dose Tac had the most reports of new-onset diabetes, leucopenia and diarrhoea. Low-dose SRL negatively influenced triglycerides, wound healing, lymphocele and anaemia. We found only weak relationships between specific AEs and drug levels.

CONCLUSIONS

Despite the low doses, CsA, Tac and SRL retained distinct and different toxicity profiles. These findings may be of relevance for tailoring specific immunosuppressive regimens to patients with particular needs.

Dyslipidemia can be controlled in diabetic as well as nondiabetic recipients after kidney transplant

BACKGROUND

Patients with diabetes have been reported to have greater dyslipidemia after kidney transplant (KTX). Because postKTX management of diabetes has changed markedly since those reports, we hypothesized that lipids can be controlled as well in diabetic as in nondiabetic recipients.

METHODS

We compared lipid levels up to 2 years after KTX (n=192) between diabetic and nondiabetic recipients. The cohort was subdivided into nondiabetic (nonDM-K; n=123), type 2 (DM2-K; n=33), or type 1 diabetes after KTX (DM1-K; n=14), or type 1 after kidney-pancreas transplant (DM1-KP; n=22).

RESULTS

Mean age and body mass index of DM2-K were greater than the others (P<0.01), and diabetes groups had a higher pretransplant A1C than nonDM-K (P<0.001). After KTX, lipid levels were not higher in diabetic than in nondiabetic recipients, and did not increase in any group. Total and low-density lipoprotein cholesterol levels decreased in DM1-K (P<0.001), high-density lipoprotein levels decreased in DM1-KP (P=0.02), and triglyceride levels were unchanged after KTX for all groups. A1C improved in DM1-K and DM1-KP (P<0.0001). There was less improvement in lipid levels with tacrolimus-sirolimus immunosuppression than with other steroid-containing regimens (P<0.05).

CONCLUSIONS

Multiple mechanisms may contribute to better lipid levels in both groups as well as the lack of difference between diabetic and nondiabetic recipients compared with what has been reported previously: greater use of and more effective lipid-lowering agents, no significant weight gain, no difference in renal function between groups, and better control of glucose in the diabetic group. Thus, overall, lipids can be controlled as well in diabetic as in nondiabetic KTX recipients.

Comparison of sirolimus and everolimus in their effects on blood lipid profiles and haematological parameters in heart transplant recipients

The mTOR (mammalian target of rapamycin) inhibitors sirolimus (SRL) and everolimus (EVL) are potent immunosuppressive agents, which allow reducing the dose of the nephrotoxic calcineurin inhibitors cyclosporin and tacrolimus (TAC) in solid organ transplant recipients. However, there is evidence that mTOR inhibitors may lead to myelosuppression and dyslipidemia/hyperlipidemia. We therefore performed a retrospective analysis in heart transplant recipients with renal insufficiency, who received 3.0 mg/d SRL (SRL group; n = 28) or 1.5 mg/d EVL (EVL group; n = 27) each in combination with a reduced TAC dose for at least one yr. Fewer cardiac rejections, but a similar rate of infections occurred in the EVL group compared with the SRL group indicating that the administered EVL dose resulted in a potent immunosuppression. Serum triglyceride and total cholesterol concentrations rose significantly in the SRL group but not in the EVL group. In the SRL group only, the frequency of statin use increased significantly during follow-up. The EVL group showed a significant rise in HDL cholesterol levels during follow-up. There was a slight transient fall in haemoglobin concentrations in the SRL group but not in the EVL group. Leucocyte counts fell significantly in both study groups. However, no cases of leucopenia and also no cases of thrombopenia occurred. In summary, we could demonstrate that in heart transplant recipients with renal insufficiency the introduction of 1.5 mg/d EVL in combination with a reduced TAC dose is effective in preventing cardiac rejections and has less adverse effects on lipid metabolism than the usually prescribed SRL dose, whereas both therapy regimens are not associated with major haematological side-effects.

Application of rapamycin in liver transplant patients with acute kidney malfunction

AIM: To explore the preventive effect of rapamycin on acute allograft rejection and kidney function recovery in liver transplant patients with acute kidney malfunction.

METHODS: A total of 25 liver transplant patients with acute kidney malfunction received rapamycin treatment as preventive measures for acute allograft rejection. Both the rejection rate and the change of kidney function were monitored.

RESULTS: Of the 25 cases, 23 survived till today with the longest time of 34 mo. The 3-mo acute rejection rate was 4%, and the kidney function of the 23 patients recovered to the normal range within 3 mo. It took more time to recover for the patients with impaired kidney function (45 ± 19 d) than that for the ones with normal kidney function (24 ± 15 d) before operation (P < 0.01).

CONCLUSION: Rapamycin can prevent the occurrence of acute allograft rejection for liver transplant patients with acute kidney malfunction, while not affect the recovery of kidney function.

Conversion to Sirolimus in Pediatric Renal Transplantation Recipients

We retrospectively evaluated the efficacy and safety of sirolimus (SRL) in 16 pediatric renal transplant recipients, who were 9.4 +/- 4.1 years of age when they first received SRL. The indications for SRL therapy were rescue from steroid-resistant acute rejection (31.3%), neoplasia (31.3%), diabetes (12.5%), polyomavirus-associated nephropathy (6.3%), chronic allograft dysfunction (6.3%), calcineurin inhibitor nephrotoxicity (6.3%), and hemolytic uremic syndrome (6.3%). Mean follow-up after the switch to SRL was 17.7 +/- 15 months. The final immunosuppression was CNI + SRL + prednisone (PRED) in five patients, SRL + PRED in six, SRL + mycophenolate mofetil (MMF) + PRED in four, and SRL + MMF in one. The use of SRL in these selected pediatric renal recipients was successful, except when creatinine was high at the moment of conversion. Further studies are necessary to assess the beneficial outcomes versus adverse events among the pediatric transplant population receiving SRL for immunosuppression.