Effect of low doses of atorvastatin on the urinary peptide profile of kidney transplant patients

Anti-Inflammatory Effect of Atorvastatin on the Kidney Graft of Living Donor Transplants

Background

Recent studies have demonstrated that statins have anti-inflammatory and immunomodulatory properties, which could be considered beneficial in kidney transplantations. This study assesses the anti-inflammatory effect of atorvastatin on the kidney grafts of living donor transplants.

Material/Methods

In a randomized clinical trial, kidney donors were divided into 2 groups. The study group constituted 24 donors who received 40 mg atorvastatin, and 24 donors who received a placebo control, 4 weeks prior to transplantation. Serum C-reactive protein (CRP) levels were measured before and after atorvastatin administration. CRP and renal function of kidney recipients were measured at baseline and 1, 6, and 24 hours after transplantation.

Results

After 4 weeks of treatment, the CRP level was 5.62±3.82 mg/dL in the control group and 3.27±0.62 mg/dL in the study group (P=0.007). Upon reperfusion, CRP levels in recipients at 1 hour were, 5.8±3.9 and 3.8±1.0 mg/dL, respectively (P=0.04). Twenty-four hours after the kidney transplantations, serum creatinine levels were 2.5±1.5 mg/dL in the study group and 3.7±2.4 mg/dL in the control group (P=0.04).

Conclusions

Our study suggests that the use of atorvastatin prior to allograft procurement of kidney transplant, reduces the acute kidney inflammatory burden profile, and promotes an improved kidney function recovery following transplantation.

Technological advances and proteomic applications in drug discovery and target deconvolution: identification of the pleiotropic effects of statins

Proteomic-based techniques provide a powerful tool for identifying the full spectrum of protein targets of a drug, elucidating its mechanism(s) of action, and identifying biomarkers of its efficacy and safety. Herein, we outline the technological advancements in the field, and illustrate the contribution of proteomics to the definition of the pharmacological profile of statins, which represent the cornerstone of the prevention and treatment of cardiovascular diseases (CVDs). Statins act by inhibiting 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase, thus reducing cholesterol biosynthesis and consequently enhancing the clearance of low-density lipoproteins from the blood; however, HMG-CoA reductase inhibition can result in a multitude of additional effects beyond lipid lowering, known as 'pleiotropic effects'. The case of statins highlights the unique contribution of proteomics to the target profiling of a drug molecule.

Effect of Statins on the Progression of Coronary Calcification in Kidney Transplant Recipients

Background

Coronary calcification (CAC) is highly prevalent in kidney transplant recipients (KTRs) and has been associated with cardiovascular morbidity and mortality. Some studies have shown a reduction in CAC progression with statin therapy in the general and chronic kidney disease (CKD) populations.

Objectives and Methods

The aim of the present study was to evaluate the effect of statins on CAC progression in incident kidney transplant recipients. Patients were randomly assigned to the statin (n = 61, 10 mg daily) and control group (n = 59). CAC and biochemical analyses were performed at baseline and 12 months.

Results

At baseline, CAC was observed in 30% and 21% of patients in the statin and control groups, respectively (p = 0.39). The calcium score at baseline and its absolute and relative changes over 12 months of follow up were similar among the groups. In the statin group, total cholesterol (p < 0.001), low density lipoprotein cholesterol (p < 0.001) and triglycerides (p = 0.005) decreased, and the estimated glomerular function rate increased (p<0.001) significantly. CRP levels remained stable (p = 0.52) in the statin group but increased in the control group (p = 0.01). In the multivariate model, there was no difference in CAC progression between the groups (group effect p = 0.034; time-effect p = 0.23; interaction p = 0.74). Similar results were obtained when only patients with ≥ 10AU calcium score (calcified) were analyzed (group effect p = 0.051; time-effect p = 0.58; interaction p = 0.99).

Conclusion

Although statins reduce the levels of cholesterol, triglycerides, inflammation and improve graft function, the dose adopted in the current study did not delay CAC progression within 12 months of follow up.

Trial Registration

Brazilian Clinical Trials Registry RBR-32RFMB

High-Throughput Proteomic Approaches to the Elucidation of Potential Biomarkers of Chronic Allograft Injury (CAI)

This review focuses on the role of OMICs technologies, concentrating in particular on proteomics, in biomarker discovery in chronic allograft injury (CAI). CAI is the second most prevalent cause of allograft dysfunction and loss in the first decade post-transplantation, after death with functioning graft (DWFG). The term CAI, sometimes referred to as chronic allograft nephropathy (CAN), describes the deterioration of renal allograft function and structure as a result of immunological processes (chronic antibody-mediated rejection), and other non-immunological factors such as calcineurin inhibitor (CNI) induced nephrotoxicity, hypertension and infection. Current methods for assessing allograft function are costly, insensitive and invasive; traditional kidney function measurements such as serum creatinine and glomerular filtration rate (GFR) display poor predictive abilities, while the current “gold-standard” involving histological diagnosis with a renal biopsy presents its own inherent risks to the overall health of the allograft. As early as two years post-transplantation, protocol biopsies have shown more than 50% of allograft recipients have mild CAN; ten years post-transplantation more than 50% of the allograft recipients have progressed to severe CAN which is associated with diminishing graft function. Thus, there is a growing medical requirement for minimally invasive biomarkers capable of identifying the early stages of the disease which would allow for timely intervention. Proteomics involves the study of the expression, localization, function and interaction of the proteome. Proteomic technologies may be powerful tools used to identify novel biomarkers which would predict CAI in susceptible individuals. In this paper we will review the use of proteomics in the elucidation of novel predictive biomarkers of CAI in clinical, animal and in vitro studies.

Uromodulin and α(1)-antitrypsin urinary peptide analysis to differentiate glomerular kidney diseases

BACKGROUND/AIMS

Glomerular kidney disease (GKD) is suspected in patients based on proteinuria, but its diagnosis relies primarily on renal biopsy. We used urine peptide profiling as a noninvasive means to link GKD-associated changes to each glomerular entity.

METHODS

Urinary peptide profiles of 60 biopsy-proven glomerular patients and 14 controls were analyzed by combining magnetic bead peptide enrichment, MALDI-TOF MS analysis, and ClinProTools v2.0 to select differential peptides. Tentative identification of the differential peptides was carried out by HPLC-MS/MS.

RESULTS

The HPLC-MS/MS results suggest that uromodulin (UMOD; m/z: 1682, 1898 and 1913) and α(1)-antitrypsin (A1AT; m/z: 1945, 2392 and 2505) are differentially expressed urinary peptides that distinguish between GKD patients and healthy subjects. Low UMOD and high A1AT peptide abundance was observed in 80-92% of patients with GKD. Proliferative forms of GKD were distinguished from nonproliferative forms, based on a combination of UMOD and A1AT peptides. Nonproliferative forms correlated with higher A1AT peptide levels - focal segmental glomerulosclerosis was linked more closely to high levels of the m/z 1945 peptide than minimal change disease.

CONCLUSION

We describe a workflow - urinary peptide profiling coupled with histological findings - that can be used to distinguish GKD accurately and noninvasively, particularly its nonproliferative forms.

Profiling the proteome in renal transplantation

Improved monitoring of transplanted solid organs is one of the next crucial steps leading to an increase in both patient and allograft survival. This can be facilitated through one or a set of surrogate biomarker molecules that accurately and precisely indicate the health status of the transplanted organ. Recent developments in the field of high throughput "omic" methods including genomics and proteomics have facilitated robust and comprehensive analysis of genes and proteins. This development has stimulated efforts in the identification of effective and clinically applicable gene and protein biomarkers in solid organ transplantation, including kidney transplantation. Some achievements have been made through proteomics in terms of profiling proteins and identification of potential biomarkers. However, the road to a successful biomarker discovery and its clinical implementation has proved to be challenging, requiring a number of key issues to be addressed. Such issues are: the lack of widely accepted protocols, difficulty in sample processing and transportation and a lack of collaborative efforts to achieve significant sample sizes in clinical studies. In this review using our area of expertise, we describe the current strategies used for proteomic-based biomarker discovery in renal transplantation, discuss inherent issues associated with these efforts and propose better strategies for successful biomarker discovery.

Effect of paricalcitol on the urinary peptidome of kidney transplant patients

BACKGROUND AND OBJECTIVE

Disorders in bone mineral metabolism are common after kidney transplantation, covering, among other pathologic conditions, secondary hyperparathyroidism. Paricalcitol, a selective vitamin D receptor activator, is indicated in the prevention and treatment of secondary hyperparathyroidism. Recent evidence suggests that paricalcitol is also associated, by mechanisms not yet clarified, with improved patient survival. To clarify these unknown mechanisms, the aim of this study was to determine whether 3 months of treatment with paricalcitol modified the urinary peptidome of kidney transplant patients.

METHODS

This prospective study included 42 stable kidney transplant patients, randomized in 2 groups: a group treated with 1 μg/d paricalcitol (n=25) and a control group that did not receive paricalcitol (n=17). Urine samples of all patients were collected at baseline and after 3 months. The proteomic approach was based on magnetic bead technology coupled to MALDI-TOF mass spectrometry.

RESULTS

Paricalcitol treatment produced significant changes in urinary peptidome of kidney transplant patients. Variations in urinary peptides were independent of the degree of proteinuria and of the decrease in parathyroid hormone levels.

CONCLUSIONS

With this preliminary study, we obtained a profile of urinary peptides in which changes occurred due to treatment with paricalcitol. The identification of proteins to which these peptides belong may improve our knowledge about the possible pleiotropic effects of paricalcitol.