Immunosuppressive therapy and lipoprotein abnormalities after cardiac transplantation

Impaired cholesterol efflux capacity and vasculoprotective function of high-density lipoprotein in heart transplant recipients

BACKGROUND

High-density lipoprotein (HDL) metabolism is significantly altered in heart transplant recipients. We hypothesized that HDL function may be impaired in these patients.

METHODS

Fifty-two patients undergoing coronary angiography between 5 and 15 years after heart transplantation were recruited in this cross-sectional study. Cholesterol efflux capacity of apolipoprotein B-depleted plasma was analyzed using a validated assay. The vasculoprotective function of HDL was studied by means of an endothelial progenitor cell migration assay.

RESULTS

HDL cholesterol levels were similar in heart transplant patients compared with healthy controls. However, normalized cholesterol efflux and vasculoprotective function were reduced by 24.1% (p < 0.001) and 27.0% (p < 0.01), respectively, in heart transplant recipients compared with healthy controls. HDL function was similar in patients with and without cardiac allograft vasculopathy (CAV) and was not related to C-reactive protein (CRP) levels. An interaction effect (p = 0.0584) was observed between etiology of heart failure before transplantation and steroid use as factors of HDL cholesterol levels. Lower HDL cholesterol levels occurred in patients with prior ischemic cardiomyopathy who were not taking steroids. However, HDL function was independent of the etiology of heart failure before transplantation and steroid use. The percentage of patients with a CRP level ≥6 mg/liter was 3.92-fold (p < 0.01) higher in patients with CAV than in patients without CAV.

CONCLUSIONS

HDL function is impaired in heart transplant recipients, but it is unrelated to CAV status. The proportion of patients with a CRP level ≥6 mg/liter is prominently higher in CAV-positive patients.

Supratherapeutic Response to Ezetimibe Administered with Cyclosporine

OBJECTIVE:

To report the case of a patient who underwent orthotopic heart transplant (OHT) and demonstrated a supratherapeutic response to ezetimibe when administered with cyclosporine.

CASE SUMMARY:

Ezetimibe 10 mg/day was added to the lipid-lowering regimen (atorvastatin 40 mg/day) of a 64-year-old male patient after OHT to achieve a target low-density lipoprotein cholesterol (LDL-C) level ≤97 mg/dL, as recommended by national guidelines. After 2 months of ezetimibe, the patient's LDL-C level had decreased by 60% to 51 mg/dL. Subsequently, the dose of ezetimibe was reduced to 5 mg/day and, after another 2 months, a repeat lipid panel revealed LDL-C 57 mg/dL.

DISCUSSION:

Hyperlipidemia is a common problem among heart transplant recipients. Combination therapy using a statin plus ezetimibe appears to be an attractive option to achieve target lipid levels in this population. However, the manufacturer warns that ezetimibe should be administered cautiously in patients concomitantly receiving cyclosporine. Unpublished data suggest a pharmacokinetic interaction between ezetimibe and cyclosporine that results in a significant 2.3- to 12-fold increase in exposure to total ezetimibe. An objective causality assessment in this case revealed that this supratherapeutic LDL-C reduction was probably related to coadministration of ezetimibe and cyclosporine. A potential mechanism to explain this interaction might be an alteration in glucuronidation induced by cyclosporine.

CONCLUSIONS:

When ezetimibe is prescribed for patients concomitantly receiving cyclosporine, it should be initiated at a lower than recommended dose (≤5 mg/day) and titrated upward. Careful and consistent monitoring of patients on this combination is also advised.

Plasmapheresis in the treatment of posttransplant cardiomyopathy

After heart transplantation a number of factors such as pre- and postoperative hypoxia of the myocardium, myocardial failure of the early postoperative period, acute rejection episodes, cytomegalovirus infection, and finally the progressive atherosclerosis of the coronary arteries lead to the development of transplanted heart failure. Severe alterations of the myocardial function at this end stage of the process correspond to incurable cardiomyopathy. The target of plasmapheresis in this case is to decrease the extent of the disturbances in the lipoprotein contents and blood rheology for the improvement of the coronary perfusion of the transplanted heart. Nine patients with 3-7 year survival periods after heart transplantations underwent plasmapheresis twice a year using the Haemonetics PCS-plus machine. 2,100-2,700 ml of plasma was removed. Biochemical data, rheology and coagulation, and the concentration of Sandimmune (Sandoz Pharma Ltd., Basel, Switzerland) were controlled, and radionuclide scintigraphy of the myocardium, coronarographia, and transesophageal ultrasound investigations were completed for these patients. The result was the significant improvement of the coronary perfusion of the myocardium. The level of immunosuppression after the plasmapheresis procedures did not change and therefore did not demand any correction. Thus, we think that plasmapheresis can be an effective method of treatment of posttransplantation cardiomyopathy; the improvement of coronary perfusion decreases the extent of chronic ischemia. Further studies are necessary to answer the question as to whether it is possible to prolong the time before retransplantation with the help of plasmapheresis.

Lipoprotein changes in children after liver transplantation: mild hypertriglyceridemia and a decrease in HDL3/HDL2 ratio

Hyperlipidemia is frequently observed in patients who undergo renal, cardiac, bone marrow, or liver transplantation, and its contribution to the long-term morbidity and survival of patients with organ transplants may be substantial. In the few studies that have focused on the pediatric age group, findings have been inconsistent. The lipoprotein profile of 10 children after liver transplantation was characterized and compared with those in normal population controls and 10 healthy siblings. Plasma triglyceride and cholesterol concentrations were determined, lipoprotein fractions (very-low-density lipoprotein [VLDL], low-density lipoprotein [LDL], and high-density lipoproteins [HDL2 and HDL3]) were isolated, their chemical compositions were analyzed (protein, phospholipids, triglycerides, free cholesterol, and cholesteryl ester), and the percent relative weight composition of the particles was calculated. Plasma triglyceride and VLDL cholesterol levels were higher post-liver transplantation (P < .05): triglycerides (mean +/- SD), 115.1 +/- 58.7 mg% versus 76.6 +/- 20.9 mg% in siblings and 60.0 +/- 25.0 mg% in normal population controls; very-low-density lipoprotein cholesterol (VLDL-C), 23.0 +/- 11.7 mg% versus 15.3 +/- 4.7 mg% and 13.0 +/- 8.0 mg%, respectively. Plasma triglyceride levels did not correlate with the length of the period after liver transplantation. Levels of LDL-C and total HDL-C and the relative weight composition of VLDL, LDL, HDL2, and HDL3 particles did not differ between post-liver transplantation children and controls. Posttransplantation, levels of HDL3, the normally predominant HDL subfraction, were decreased relative to HDL2 levels (HDL3, 1.3; HDL2, 2.3). Because this observed relative increase in larger cholesteryl ester-rich HDL particles (HDL2) may result from inhibition of cholesteryl ester-triglyceride transfer processes, cholesteryl ester transfer protein activity was assayed. Cholesteryl ester transfer protein activity did not differ between patients and controls. Thus, the lipoprotein changes observed in children post-liver transplantation are mild hypertriglyceridemia and a significant increase in HDL2 relative to HDL3. Because HDL2 is regarded as protective against atherosclerosis, this may be of clinical relevance.

Elevated high density lipoprotein concentrations in heart transplant recipients are related to impaired plasma cholesteryl ester transfer and hepatic lipase activity

Accelerated atherosclerosis is a major complication of heart transplantation, and is frequently associated with a dyslipoproteinemia characterized by a paradoxical increase in HDL-cholesterol concentration. To define this abnormality, the lipoprotein profiles of 25 heart transplant recipients (HTR) were analyzed and compared with those of 26 control subjects. HDL, as separated on the basis of density in 3 subfractions, were increased in concentration: HDL2: +51%, HDL3a: +29%, HDL3b: +32%. HDL2 and HDL3a displayed an enrichment in surface components, phospholipids, unesterified cholesterol and apo E, leading to an increased size compared with subfractions of similar density in the controls. The major steps of plasma HDL metabolism were investigated: cholesterol esterification (LCAT activity), cholesteryl ester transfer to apo B-containing lipoproteins (CETP) and the hepatic hydrolysis of HDL components (HL activity). We demonstrated a partial deficiency in CETP (-28%) and hepatic lipase (-36%) activities with normal LCAT activity. Correlations in total study population (HTR plus controls) evidenced negative associations between CETP activity and HDL3a concentrations and between HL activity and HDL2-cholesterol as a percent of total HDL-cholesterol. Therapeutic agents used in post transplantation treatment such as glucocorticoids and/or cyclosporine may be speculated thus to affect both CETP and HL activities and, by arresting the HDL cycle in a CE-saturated state, do decrease the efficiency of reverse cholesterol extraction at the site of the graft.

Factors influencing the development of hypercholesterolemia after cardiac transplantation

Although hypercholesterolemia is a frequent complication in cardiac transplant recipients, the exact mechanisms contributing to its development are not known. Cholesterol levels in 151 thoracic transplant patients treated with cyclosporine, azathioprine and prednisone were retrospectively examined to evaluate the factors influencing the heterogeneity of changes after the first year after transplantation in patients on a standard 3-drug immunosuppression regimen. Three groups were compared including ischemic heart transplant (n = 72), nonischemic heart transplant (n = 64) and heart-lung/lung transplant (n = 15) recipients. After the first year, 64 patients (43%) developed consistent hypercholesterolemia (greater than 240 mg/dl) for which pharmacologic treatment was initiated. Forty-eight patients (67%) in the ischemic heart transplant group required treatment, significantly (p less than 0.001) greater than both the nonischemic (n = 14; 22%) and heart-lung/lung transplant (n = 2; 13%) group. Univariate and forward stepwise multivariate regression analysis identified 4 factors that were all significantly and independently correlated with follow-up cholesterol including prednisone dose (p less than 0.001), baseline cholesterol (p less than 0.001), glucose (p less than 0.001) and weight gain (p less than 0.01). Changes in triglycerides in the 3 groups of patients were similar to changes in cholesterol. Furthermore, the increase in cholesterol in patients requiring treatment was primarily due to an increase in low-density lipoprotein cholesterol. These data demonstrate that hypercholesterolemia is common in heart transplant recipients treated with standard 3-drug immunosuppression and generally develops within the first 2 years after transplantation. However, this complication is not uniform and appears to be most strongly related to previous coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)