Preventing cardiovascular outcome in patients with renal impairment: is there a role for lipid-lowering therapy?

Upregulation of transglutaminase and ε (γ-glutamyl)-lysine in the Fisher-Lewis rat model of chronic allograft nephropathy

BACKGROUND

Tissue transglutaminase (TG2), a cross-linking enzyme, modulates deposition of extracellular matrix protein in renal fibrosis. This study aimed to examine TG2 and its cross-link product ε(γ-glutamyl)-lysine in the Fisher-Lewis rat renal transplantation (RTx) model of chronic allograft nephropathy (CAN).

MATERIALS AND METHODS

Left renal grafts from male Fisher and Lewis were transplanted into Lewis rats, generating allografts and isografts, respectively. Blood pressure, renal function, and proteinuria were monitored for up to 52 weeks. At termination, CAN was assessed in the renal tissue by light and electron microscopy, TG2 and ε(γ-glutamyl)-lysine by immunofluorescence, and the urinary ε(γ-glutamyl)-lysine by high performance liquid chromatography.

RESULTS

Compared to the isograft, the allografts were hypertensive, proteinuric, and uraemic and developed CAN. Extracellular TG2 (glomerulus: 64.55 ± 17.61 versus 2.11 ± 0.17, P < 0.001; interstitium: 13.72 ± 1.62 versus 3.19 ± 0.44, P < 0.001), ε(γ-glutamyl)-lysine (glomerulus: 21.74 ± 2.71 versus 1.98 ± 0.37, P < 0.01; interstitium: 37.96 ± 17.06 versus 0.42 ± 0.11, P < 0.05), TG2 enzyme activity (1.09 ± 0.13 versus 0.41 ± 0.03 nmol/h/mg protein, P < 0.05), TG2 mRNA (20-fold rise), and urinary ε(γ-glutamyl)-lysine (534.2 ± 198.4 nmol/24 h versus 57.2 ± 4.1 nmol/24 h, P < 0.05) levels were significantly elevated in the allografts and showed a positive linear correlation with tubulointerstitial fibrosis.

CONCLUSION

CAN was associated with upregulation of renal TG2 pathway, which has a potential for pharmacological intervention. The elevated urinary ε(γ-glutamyl)-lysine, measured for the first time in RTx, is a potential biomarker of CAN.

Statin therapy ameliorates renal allograft function

BACKGROUND

Statins have proven ability as antilipidemic agents and benefit cardiovascular survival in transplant recipients. The pleiotropic effects of statins on renal function in renal allograft recipients are still undetermined.

METHODS

Statin therapy was initiated according to guidelines for cardiovascular protection. Serum creatinine concentration and estimated glomerular filtration rate (eGFR) were analyzed before and after introduction of statins. The 73 patients who were retrospectively studied included those who were dialysis-dependent. Mean changes in eGFR and lipid profile were compared before and after commencing statins using chi(2) tests.

RESULTS

Mean serum creatinine concentration 18 months before starting statin therapy was 160.13 mumol/L, and 24 months after starting statin therapy was 172.22 mumol/L. Mean eGFR was 53.40 mL/min 18 months before starting statin therapy, and decreased to 49.43 mL/min after starting statin therapy. This represented a decline in renal function of 0.22 mL/min/mo over 18 months. The eGFR at 12 months after beginning statin therapy was 52.67 mL/min, and at 24 months was 49.06 mL/min. The rate of decline of eGFR after starting statin therapy was significantly lower: 0.02 mL/min/mo over 24 months (P < .001). Total cholesterol and low-density lipoprotein cholesterol concentrations were significantly decreased after starting statin therapy (P < .001). Four of 73 patients developed graft failure within 24 months.

CONCLUSION

Statin therapy in our setting was associated with a lower rate of decline in renal function in renal allograft recipients within 2 years of starting treatment.

Asymmetrical dimethylarginine is associated with renal and cardiovascular outcomes and all-cause mortality in renal transplant recipients

Increased plasma levels of asymmetric dimethylarginine (ADMA) are associated with endothelial dysfunction and predict the progression to dialysis and death in patients with chronic kidney disease. The effects of these increased ADMA levels in renal transplant recipients, however, are unknown. We used the data from ALERT, a randomized, double-blind, placebo-controlled study of the effect of fluvastatin on cardiovascular and renal outcomes in 2102 renal transplant recipients with stable graft function on enrollment. Patients who were initially randomized to fluvastatin or placebo in the 5- to 6-year trial were offered open-label fluvastatin in a 2-year extension of the original study. After adjustment for baseline values for established factors in this post hoc analysis, ADMA was found to be a significant risk factor for graft failure or doubling of serum creatinine (hazard ratio 2.78), major cardiac events (hazard ratio 2.61), cerebrovascular events (hazard ratio 6.63), and all-cause mortality (hazard ratio 4.87). In this trial extension, the number of end points increased with increasing quartiles of plasma ADMA levels. All end points were significantly increased in the fourth compared to the first quartile. Our study shows that elevated plasma levels of ADMA are associated with increased morbidity, mortality, and the deterioration of graft function in renal transplant recipients.

Comparison of predictive ability of lipoprotein components to that of traditional risk factors of coronary events in renal transplant recipients

OBJECTIVE

Risk factors for major adverse coronary events (MACE) in renal transplant recipients are often different from those of non-transplanted populations. We compared the predictive power of lipoprotein components (LC) to that of more traditional risk factors such as serum creatinine, diabetes and inflammation measured by C-reactive protein (CRP) in the assessment of lescol in renal transplantation (ALERT) trial population.

METHODS

From the 2102 randomized patients in ALERT we selected 1734 patients with a complete set of risk and adjustment factors used in the study. Cox regression analysis was used to estimate relationships between baseline values of risk factors and first occurrence of MACE. Chi square statistics, receiver operating characteristics (ROC) and net reclassification improvement (NRI) were used to compare the information value of different risk factors.

RESULTS

Atherogenic LC and especially non-high density cholesterol (nHDL-C) were as predictive as creatinine and nHDL-C was about as predictive as diabetes. CRP, body mass index, hypertension and glucose had less prediction ability than nHDL-C. The rank order of prediction was the same in the two treatment groups. By regression modelling the actual MACE risk reduction from 6 weeks onwards was well predicted from the difference in LC at 6 week.

CONCLUSION

LC and especially nHDL-C predicted MACE at least as good as creatinine. Diabetes was about equally good as nHDL-C to predict MACE occurrence. Inflammation had less prediction ability than the other factors. Treated levels of atherogenic LC predicted MACE risk reduction well.