The coexistence of diabetic retinopathy and diabetic nephropathy is associated with worse kidney outcomes

Background

Up to 50-60% of patients with diabetes have non-diabetic kidney disease (NDKD) on kidney biopsy. Diabetic retinopathy (DR) is a microvascular complication of diabetes frequently associated with diabetic nephropathy (DN). The objective of the current study was to investigate the kidney outcomes and survival in patients with biopsy diagnoses of DN and NDKD according to the presence of DR.

Methods

We conducted an observational, multicentre and retrospective study of the pathological findings of renal biopsies from 832 consecutive patients with diabetes from 2002 to 2014 from 18 nephrology departments. The association of DR with kidney replacement therapy (KRT) or survival was assessed by Kaplan-Meier and Cox regression analyses.

Results

Of 832 patients with diabetes and renal biopsy, 768 had a retinal examination and 221/768 (22.6%) had DR. During a follow-up of 10 years, 288/760 (37.9%) patients with follow-up data needed KRT and 157/760 (20.7%) died. The incidence of KRT was higher among patients with DN (alone or with NDKD) and DR [103/175 (58.9%)] than among patients without DR [88/216 (40.7%), P < .0001]. The incidence of KRT was also higher among patients with only NDKD and DR than among those without DR [18/46 (39.1%) versus 79/331 (23.9%), P < .0001]. In multivariate analysis, DR or DN were independent risk factors for KRT {hazard ratio [HR] 2.48 [confidence interval (CI) 1.85-3.31], P < .001}. DN (with or without DR) was also identified as an independent risk factor for mortality [HR 1.81 (CI 1.26-2.62), P = .001].

Conclusions

DR is associated with a higher risk of progression to kidney failure in patients with histological DN and in patients with NDKD.

A new oral model of free fatty acid kinetics to assess lipolysis in subjects with and without type 2 diabetes

Assessing free fatty acids (FFAs) kinetics and the role of insulin and glucose on FFA lipolysis and disposal may improve our understanding of the pathogenesis of type 2 diabetes (T2D). Some models have been proposed to describe FFA kinetics during an intravenous glucose tolerance test and only one during an oral glucose tolerance test. Here, we propose a model of FFA kinetics during a meal tolerance test and use it to assess possible differences in postprandial lipolysis in individuals with type 2 diabetes (T2D) and individuals with obesity without type 2 diabetes (ND). We studied 18 obese ND and 16 T2D undergoing three meal tolerance tests (MTT) on three occasions (breakfast, lunch, and dinner). We used plasma glucose, insulin, and FFA concentrations collected at breakfast to test a battery of models and selected the best one based on physiological plausibility, ability to fit the data, precision of parameter estimates, and the Akaike parsimony criterion. The best model assumes that the postprandial suppression of FFA lipolysis is proportional to the above basal insulin, while FFA disposal is proportional to FFA concentration. It was used to compare FFA kinetics in ND and T2D along the day. The maximum lipolysis suppression occurred significantly earlier in ND than T2D (39 ± 6 min vs. 102 ± 13 min, 36 ± 4 min vs. 78 ± 11 min, and 38 ± 6 min vs. 84 ± 13 min, P < 0.01, at breakfast, lunch, and dinner, respectively), making lipolysis significantly lower in ND than T2D. This is mainly attributable to the lower insulin concentration in the second group. This novel FFA model allows to assess lipolysis and insulin antilipolytic effect in postprandial conditions.NEW & NOTEWORTHY In this study, we propose a new mathematical model able to quantify postprandial FFA kinetics and adipose tissue insulin sensitivity in both subjects with obesity without type 2 diabetes (ND) and subjects with type 2 diabetes (T2D). Results show that the slower postprandial suppression of lipolysis in T2D contributes to the higher free fatty acid (FFA) concentration that, in turn, may contribute to hyperglycemia.

Mass Transfer Coefficient: Comparison between Methods

The mass transfer area coefficient (MTC) is the best parameter for solute transport evaluation in continuous ambulatory peritoneal dialysis (CAPD) patients.

We compared three simplified MTC methods (calculated according Garred, Krediet, or Lindholm) and the peritoneal equilibration test (PET) (Twardowskl) to complex MTC (MTCX) (Randerson and farrell) for urea and creatinine, by means of 29 tests performed In 24 stable CAPD patients.

There were no significant differences (paired t-test) between MTCX and each of the simplified MTC, except for creatinine MTC calculated by Krediet's method, which was significantly different (MTCX: 9.36.:1:.4.32, K-MTC: 10.48.:1:.4.55, p<0.05).

Likewise, there was an acceptable correlation between complex MTC and each of the simplified methods including the PET.

However, a more detailed study of the MTC's categorizations shows poor agreement with complex MTC categorization. Better results are obtained by PET categorization, which reaches good likelihood ratios either for positive or negative events.

We conclude that simplified MTC or the dialysatelplasma ratio at 240 minutes for urea and creatinine has an acceptable correlation with complex MTC and can be useful in clinical practice.

There is poor agreement between solute transport categorizations of simplified MTC and complex MTC. There Is a better coincidence between the PET ( DIP at 240 minutes) and complex MTC categorizations.

Risk factors for non-diabetic renal disease in diabetic patients

Background

Diabetic patients with kidney disease have a high prevalence of non-diabetic renal disease (NDRD). Renal and patient survival regarding the diagnosis of diabetic nephropathy (DN) or NDRD have not been widely studied. The aim of our study is to evaluate the prevalence of NDRD in patients with diabetes and to determine the capacity of clinical and analytical data in the prediction of NDRD. In addition, we will study renal and patient prognosis according to the renal biopsy findings in patients with diabetes.

Methods

Retrospective multicentre observational study of renal biopsies performed in patients with diabetes from 2002 to 2014.

Results

In total, 832 patients were included: 621 men (74.6%), mean age of 61.7 ± 12.8 years, creatinine was 2.8 ± 2.2 mg/dL and proteinuria 2.7 (interquartile range: 1.2–5.4) g/24 h. About 39.5% (n = 329) of patients had DN, 49.6% (n = 413) NDRD and 10.8% (n = 90) mixed forms. The most frequent NDRD was nephroangiosclerosis (NAS) (n = 87, 9.3%). In the multivariate logistic regression analysis, older age [odds ratio (OR) = 1.03, 95% CI: 1.02–1.05, P < 0.001], microhaematuria (OR = 1.51, 95% CI: 1.03–2.21, P = 0.033) and absence of diabetic retinopathy (DR) (OR = 0.28, 95% CI: 0.19–0.42, P < 0.001) were independently associated with NDRD. Kaplan–Meier analysis showed that patients with DN or mixed forms presented worse renal prognosis than NDRD (P < 0.001) and higher mortality (P = 0.029). In multivariate Cox analyses, older age (P < 0.001), higher serum creatinine (P < 0.001), higher proteinuria (P < 0.001), DR (P = 0.007) and DN (P < 0.001) were independent risk factors for renal replacement therapy. In addition, older age (P < 0.001), peripheral vascular disease (P = 0.002), higher creatinine (P = 0.01) and DN (P = 0.015) were independent risk factors for mortality.

Conclusions

The most frequent cause of NDRD is NAS. Elderly patients with microhaematuria and the absence of DR are the ones at risk for NDRD. Patients with DN presented worse renal prognosis and higher mortality than those with NDRD. These results suggest that in some patients with diabetes, kidney biopsy may be useful for an accurate renal diagnosis and subsequently treatment and prognosis.

Molecular profile of urine extracellular vesicles from normo-functional kidneys reveal minimal differences between living and deceased donors

BACKGROUND

Kidney transplantation (KTx) is the best therapeutic approach for chronic kidney diseases leading to irreversible kidney failure. Considering the origin of the graft, several studies have reported differences between living (LD) and deceased donors (DD) in graft and patient survival. These differences seem to be related to multiple factors including, donor age and time of cold ischemia among others. Many of transplanted organs come from old-aged DDs, in which pre-transplant biopsy is recommended. However, kidney biopsy has several limitations, and there is a need to develop alternatives to assess the status of a kidney before transplantation. As the analysis of urinary extracellular vesicles (uEVs) rendered promising results as non-invasive biomarkers of kidney-related pathologies, this pilot study aimed to investigate whether profiling uEVs of LDs and DDs may be of help to assess the quality of the kidney before nephrectomy.

METHODS

uEVs from 5 living donors and 7 deceased donors were isolated by size-exclusion chromatography, and their protein and miRNA content were analysed by liquid chromatography followed by mass spectrometry and next generation sequencing, respectively. Then, hierarchical clustering and venn diagrams were done with Perseus software and InteractiVenn tool. Specific EVs data bases were also used for Gene Ontology analysis.

RESULTS

Next generation sequencing revealed that uEVs from DDs contained less miRNAs than LDs, but most of the DD-expressed miRNAs were shared with LDs (96%). Only miR-326 (targeting the apoptotic-related Bcl2) was found significantly over-represented in LD. Focusing on the protein content, we detected a low intra-group correlation in both types of donors. Despite these differences, hierarchical clustering of either miRNA or protein data could not identify a differential profile between LDs and DDs. Of note, 90% of transplanted patients had a functional graft after a year from KTx.

CONCLUSIONS

In this pilot study we found that, in normo-functional grafts, minor differences in uEVs profile could not discriminate between LDs and DDs.

Efficacy of mycophenolate treatment in adults with steroid-dependent/frequently relapsing idiopathic nephrotic syndrome

BACKGROUND

This study assessed the efficacy of therapy with mycophenolate (MF) and reduced doses of steroids in adults with steroid-dependent/frequently relapsing idiopathic nephrotic syndrome (SD/FR-INS).

METHODS

Twenty-nine nephrotic patients (including 16 males and 13 females; mean age: 40 years, range: 18-74) were treated. Starting doses of MF were 2000 mg/day for mofetil MF (1500 mg/day in one patient) or 1440 mg/day for sodium MF. The initial prednisone (PDN) dose was 10 mg/day in 14 patients, 5 mg/day in two patients and no steroids in one patient. In the remaining 12 patients, moderate initial doses of PDN were administered (mean: 23.7 mg/day, range: 15-40), tapering to 10 mg/day after 1 month.

RESULTS

Nephrotic syndrome remission was achieved in 27/29 cases (93.1%) (25 complete, 2 partial). Two patients showed resistance to the prescribed schedule. The first cycle of MF therapy was concluded in 20 patients after a mean (range) of 16.9 months (12-49). Maintenance of remission was observed in 11 of these 20 cases (55%) after a mean follow-up of 32.8 months (12-108). In nine patients with nephrotic syndrome relapse after tapering of MF (MF dependency), the same MF-PDN schedule was restarted, leading again to remission in all nine. The remaining seven MF-sensitive patients are still receiving their first therapeutic cycle. To date, the mean time under therapy in the 27 MF-sensitive patients is 38 months (4-216). Regarding complications, only minor digestive disorders and a slight decrease in blood haemoglobin levels were observed in a few patients.

CONCLUSIONS

MF plus reduced doses of PDN is an effective and well-tolerated therapy for adult SD/FR-INS. Though MF dependence is observed, its low toxicity could allow long periods of therapy if it is required to maintain nephrotic syndrome remission.

Prevalence, evolution, and related risk factors of kidney disease among Spanish HIV-infected individuals

Prevalence of kidney disease (KD) is increasing among human immunodeficiency virus (HIV)-infected population. Different factors have been related, varying on different published series.The objectives were to study prevalence of KD in those patients, its evolution, and associated risk factors.An observational cohort study of 1596 HIV-positive patients with cross-sectional data collection in 2008 and 2010 was conducted. We obtained clinical and laboratory markers, and registered previous or current treatment with tenofovir (TDF) and indinavir (IDV). The sample was divided according to estimated glomerular filtration rate (eGFR) by modification of diet in renal disease (MDRD) equation. Group 1: eGFR ≤60 mL/min/1.73 m; group 2: eGFR >60 mL/min/1.73 m.Among the patients, 76.4% were men, mean age (SD) 45 ± 9 years, time since diagnose of HIV 14 ± 7 years, and 47.2% of the patients received previous treatment with TDF and 39.1% with IDV. In 2008, eGFR ≤60: 4.9% (91.4% of them in chronic kidney disease [CKD] stage 3, eGFR 59-30 mL/min); this group was older, presented higher fibrinogen levels, and more patients were treated previously with TDF and IDV. In 2010, eGFR ≤60: 3.9% (87.1% stage 3 CKD). The 2.4% of cohort showed renal improvement and 1.3% decline of renal function over time. The absence of hypertension and treatment with TDF were associated with improvement in eGFR. Increased age, elevated fibrinogen, decreased albumin, diabetes mellitus, hyperTG, and worse virological control were risk factors for renal impairment.The HIV-positive patients in our area have a CKD prevalence of 4% to 5% (90% stage 3 CKD) associated with ageing, inflammation, worse immune control of HIV, TDF treatment, and metabolic syndrome.

Characterization and proteomic profile of extracellular vesicles from peritoneal dialysis efflux

Peritoneal Dialysis (PD) is considered the best option for a cost-effective mid-term dialysis in patients with Chronic Renal Failure. However, functional failure of the peritoneal membrane (PM) force many patients to stop PD treatment and start haemodialysis. Currently, PM functionality is monitored by the peritoneal equilibration test, a tedious technique that often show changes when the membrane damage is advanced. As in other pathologies, the identification and characterization of extracellular vesicles (EVs) in the peritoneal dialysis efflux (PDE) may represent a non-invasive alternative to identify biomarkers of membrane failure. Using size-exclusion chromatography, we isolated EVs from PDE in a group of patients. Vesicles were characterized by the presence of tetraspanin markers, nanoparticle tracking analysis profile, cryo-electron microscopy and mass spectrometry. Here, we report the isolation and characterization of PDE-EVs. Based on mass spectrometry, we have found a set of well-conserved proteins among patients. Interestingly, the peptide profile also revealed remarkable changes between newly enrolled and longer-treated PD patients. These results are the first step to the identification of PDE-EVs based new markers of PM damage, which could support clinicians in their decision-making in a non-invasive manner.

Environmental Impact of Alkyl Lead(IV) Derivatives: Perspective after Their Phase-out

The use of alkyl lead derivatives as antiknock agents in gasoline can be considered as one of the main pollution disasters of the 20th century because of both the global character of the pollution emitted and the seriousness of the impact on human health. Alkyl lead derivatives in themselves cannot be considered to be persistent pollutants because they readily degrade either before being released from the tailpipes or soon afterwards in the atmosphere. However, the inorganic lead they produced has been deposited in soils all over the planet, largely, but not exclusively in urban areas and along motorways, since the direct emission of lead into the atmosphere favored its dispersal over great distances: The signal of the massive use of alkyl lead derivatives has been found all over the world, including in remote sites such as polar areas. The short residence time of lead in the atmosphere implies that this compartment is highly responsive to changes in emissions. This was demonstrated when leaded gasoline was phased-out and is in striking contrast to the very long permanence of inorganic lead in soils, where resuspension is a permanent source of toxic lead.

Comparative differential proteomic analysis of minimal change disease and focal segmental glomerulosclerosis

Background

Minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS) are glomerular diseases characterized by nephrotic syndrome. Their diagnosis requires a renal biopsy, but it is an invasive procedure with potential complications. In a small biopsy sample, where only normal glomeruli are observed, FSGS cannot be differentiated from MCD. The correct diagnosis is crucial to an effective treatment, as MCD is normally responsive to steroid therapy, whereas FSGS is usually resistant.

The purpose of our study was to discover and validate novel early urinary biomarkers capable to differentiate between MCD and FSGS.

Methods

Forty-nine patients biopsy-diagnosed of MCD and primary FSGS were randomly subdivided into a training set (10 MCD, 11 FSGS) and a validation set (14 MCD, 14 FSGS). The urinary proteome of the training set was analyzed by two-dimensional differential gel electrophoresis coupled with mass spectrometry. The proteins identified were quantified by enzyme-linked immunosorbent assay in urine samples from the validation set.

Results

Urinary concentration of alpha-1 antitrypsin, transferrin, histatin-3 and 39S ribosomal protein L17 was decreased and calretinin was increased in FSGS compared to MCD. These proteins were used to build a decision tree capable to predict patient’s pathology.

Conclusions

This preliminary study suggests a group of urinary proteins as possible non-invasive biomarkers with potential value in the differential diagnosis of MCD and FSGS. These biomarkers would reduce the number of misdiagnoses, avoiding unnecessary or inadequate treatments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0452-6) contains supplementary material, which is available to authorized users.

Impact of protease inhibitors on the evolution of urinary markers: Subanalyses from an observational cross-sectional study

Kidney injury (defined as the presence of albuminuria, proteinuria, glycosuria [without hyperglycemia], hematuria, and/or renal hypophosphatemia) is an emerging problem in human immunodeficiency virus (HIV)-infected patients, although few data are available on the role of protease inhibitors (PIs) in this condition.To determine the time to kidney injury in a cohort of HIV-infected patients receiving a PI-containing regimen.We report the results of a subanalysis of a published cross-sectional study. The subanalysis included only patients receiving PI-containing regimens for more than 6 months (377 of the overall 970 patients). We determined associated factors and constructed receiver operating characteristic curves to estimate time to kidney injury depending on the PI used.The percentage of patients with kidney injury was 27.7% for darunavir, 27.9% for lopinavir, and 30% for atazanavir. Time to kidney injury was as follows: 229 days for atazanavir/ritonavir (area under the curve [AUC], 0.639; sensitivity, 0.89; specificity, 0.41); 332 days for atazanavir/ritonavir plus tenofovir (AUC, 0.603; sensitivity, 0.75; and specificity, 0.29); 318 days for nonboosted atazanavir (AUC, 0.581; sensitivity, 0.89; and specificity, 0.29); 478 days for lopinavir/ritonavir (AUC, 0.566; sensitivity, 0.864; and specificity, 0.44); 1339 days for lopinavir/ritonavir plus tenofovir (AUC, 0.667; sensitivity, 0.86; and specificity, 0.77); 283 days for darunavir/ritonavir (AUC, 0.523; sensitivity, 0.80; and specificity, 0.261); and 286 days for darunavir/ritonavir plus tenofovir (AUC, 0.446; sensitivity, 0.789; and specificity, 0.245). The use of lopinavir/ritonavir without tenofovir was a protective factor (odds ratio = 1.772; 95%CI, 1.070-2.93; P = 0.026).For all PIs, the percentage of patients with kidney injury exceeded 27%, irrespective of tenofovir use. The longest time to kidney injury was recorded with lopinavir/ritonavir. These results demonstrate the need for renal monitoring, including urine samples, in patients receiving a PI-based regimen, even when tenofovir is not used concomitantly.

Nodular Arteriolar Hyalinosis as Histopathologic Hallmark of Calcineurin Inhibitor Nephrotoxicity: Does It Always Have the Same Meaning?

INTRODUCTION

Nodular arteriolar hyalinosis (NAH) is a typical, although not specific, histological finding of calcineurin inhibitor toxicity (CNIT). The objective of our study was to assess the reason why some patients showing strong NAH in renal graft biopsies who underwent calcineurin inhibitor (CNI) withdrawal presented very poor outcome whereas others improved graft function.

MATERIAL AND METHODS

We performed 207 renal graft biopsies between January 2011 and May 2014 due to clinical criteria. In 13 patients CNI withdrawal was performed, and the major histopathological finding was severe NAH. The results after this action were analyzed.

RESULTS

We selected 2 groups: good outcome and poor outcome. Eight patients showed good results including stabilization or improvement of graft function. Five patients presented poor results requiring chronic hemodialysis. C4d staining was negative in all biopsy specimens, and peritubular capillaritis was not observed. To identify potential prognostic markers we retrospectively reviewed biopsy samples looking for minor or nonspecific features, especially inflammation scores both global and on fibrotic areas as per Banff classification. Mean serum creatinine level at time of biopsy and mean arteriolar hyalinosis score did not show significant differences between both groups. In contrast, the poor results group presented a higher mean global inflammation score compared with the good results patients.

CONCLUSIONS

NAH is not a risk factor for poor renal graft outcome by itself. Other histopathologic findings, usually considered as secondary markers, like the inflammation score, should be considered before deciding CNI withdrawal.

Late Onset of Cholesterol Embolism Leading to Graft Failure After Renal Transplantation: Report of Two Cases

Cholesterol-crystal embolization (CE) usually presents as an acute or subacute multisystemic disease. When affecting native kidneys prognosis is poor, often leading to chronic kidney disease. Presentation in renal allografts is a rare condition although probably underdiagnosed. If renal CE originates from the recipient, allograft survival is usually good, whereas if the donor is the origin, graft dysfunction and subsequent graft loss are common. Associated risk factors are common to native and transplanted kidneys. We report 2 renal graft recipients of different cadaveric donors, both male and 68 years old, diagnosed with CE in renal grafts at 19 and 72 months after transplantation, respectively. They presented previous risk factors for CE, including severe atherosclerosis. They presented insidious and asymptomatic impairment of renal function initially. Renal graft biopsy specimens showed CE in the interlobular arteries. Potential triggers for CE were suspended and high doses of steroids were started. However, progressive decline in renal function and requirement of chronic dialysis occurred within the first year after diagnosis in both cases. Herein we discuss the causal or incidental role of CE in the graft failure of these cases, highlighting the serious outcome despite the recipient origin of the CE and the initiation of treatment.

Early intensive treatment improves outcomes in patients with glomerular hyperfiltration and type 2 diabetes

BACKGROUND AND OBJECTIVE

Approximately 24-40% of patients with type 2 diabetes mellitus (T2DM) develop kidney damage. Our objective was to evaluate the long-term evolution of renal function using isotopic determination of GFR and urinary albumin excretion (UAE) in patients with T2DM undergoing intensive treatment for renal and cardiovascular risk factors.

PATIENTS AND METHODS

This was a single-center, prospective study of 201 patients with T2DM and UAE who initiated intensive treatment. They were followed for 17.2±6.5 years. Patients were divided into three groups, according to renal function: 167(85.6%) had stable renal function, 16(8.2%) had creatinine levels that doubled and 12(6.2%) began renal replacement therapy (RRT). We performed periodic isotopic determinations of GFR using (125)I-iothalamate.

RESULTS

There were significant differences between the three groups with respect to age, duration of T2DM at baseline, years of follow-up in the study and systolic blood pressure, serum creatinine, isotopic GFR, and UAE at baseline. Renal function evolution slopes were -1.55mL/min/1.73m(2)/year in patients with stable creatinine, -2.49mL/min/1.73m(2)/year in those with doubled creatinine, and -8.16mL/min/1.73m(2)/year in those requiring RRT. We also found that differences in renal events were determined by delayed initiation of intensive treatment.

CONCLUSION

Patients with glomerular hyperfiltration who were undergoing treatment with renin angiotensin aldosterone system blockers exhibited a better evolution in renal function, possibly because these patients initiated intensive treatment earlier. Although diabetic nephropathy is associated with classic risk factors, early initiation of intensive treatment should be a priority in order to prevent worsening renal function.

High prevalence of signs of renal damage despite normal renal function in a cohort of HIV-infected patients: evaluation of associated factors

Renal disorders are an emerging problem in HIV-infected patients. We performed a cross-sectional study of the first 1000 HIV-infected patients attended at our HIV unit who agreed to participate. We determined the frequency of renal alterations and its related risk factors. Summary statistics and logistic regression were applied. The study sample comprised 970 patients with complete data. Most were white (94%) and men (76%). Median (IQR) age was 48 (42-53) years. Hypertension was diagnosed in 19%, dyslipidemia in 27%, and diabetes mellitus in 3%. According to the Chronic Kidney Disease Epidemiology Collaboration (CKD EPI) equation, 29 patients (3%) had an eGFR<60 ml/min/1.73 m(2); 18 of them (62%) presented altered albumin/creatinine and protein/creatinine (UPC or UAC) ratios. Of the patients with eGFR>60 mL/min, it was present in 293 (30%), 38 of whom (7.1%) had UPC>300 mg/g. Increased risk of renal abnormalities was correlated with hypertension (OR, 1.821 [95%CI, 1.292;2.564]; p=0.001), age (OR, 1.015 [95%CI, 1.001;1.030], per one year; p=0.040), and use of tenofovir disoproxil fumarate (TDF) plus protease inhibitor (PI), (OR, 1.401 [95%CI, 1.078;1.821]; p=0.012). Current CD4 cell count was a protective factor (OR, 0.9995 [95%CI, 0.9991;0.9999], per one cell; p=0.035). A considerable proportion of patients presented altered UPC or UAC ratios, despite having an eGFR>60 mL/min. CD4 cell count was a protective factor; age, hypertension, and use of TDF plus PIs were risk factors for renal abnormalities. Based on our results, screen of renal abnormalities should be considered in all HIV-infected patients to detect these alterations early.

Evaluation of protease inhibitors containing tubes for MS-based plasma peptide profiling studies

BACKGROUND

Peptide profiling of biological fluids is a promising tool for biomarker discovery. Blood is an ideal entity for proteomic studies but it is subjected to a proteolytic activity that sets up just at the moment of phlebotomy. Intending to prevent this proteolytic activity, tubes containing protease inhibitors (PI) have been developed. In this study, we evaluated the effect on plasma peptide profile of using tubes containing PI and the evolution of this effect over time.

METHODS

Blood samples from ten subjects were drawn into conventional tubes containing ethylenediaminetetraacetic acid (EDTA) and tubes containing PI. Samples were processed at time "zero" and after 1, 2, 4, and 8 hr. Plasma peptide profiles were analyzed by magnetic bead based technology coupled to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry readout.

RESULTS

When comparing plasma peptide profile of blood samples collected into tubes containing PI with samples collected into conventional EDTA tubes, differences in the area of 13 peaks were detected at time "zero"; after 8 hr these differences tended to disappear. Moreover, bradykinin and C3- and C4-derived peptides were produced promptly after blood extraction when samples were collected into conventional EDTA tubes, and the use of PI prevented their generation.

CONCLUSION

Considering that time taken to process blood samples affects their peptide profile and a decrease in PI's effect occurs over time, it may be concluded that the use of tubes containing PI for blood collection may be advantageous in the context of research, but may have some limitations regarding clinical practice.

Urinary peptide profiling to differentiate between minimal change disease and focal segmental glomerulosclerosis

BACKGROUND

Minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS) are the main causes of primary idiopathic nephrotic syndrome in children and adults, with diagnosis being essential for the appropriate choice of therapy and requiring renal biopsy. However, the presence of only normal glomeruli on renal biopsy of FSGS patients may lead to the misclassification of these patients as having MCD. The aim of this study was to (i) compare the peptide profile of MCD and FSGS patients with that of a group of healthy subjects, (ii) generate and validate a class prediction model to classify MCD and FSGS patients and (ii) identify candidate biomarkers of these glomerular entities by analysis of the urinary peptidome.

METHODS

The urinary peptide profile was analyzed by magnetic bead-based technology combined with MALDI-TOF mass spectrometry in 44 patients diagnosed of MCD (n = 22) and FSGS (n = 22). The resulting spectra were compiled and analyzed using ClinProTools software.

RESULTS

A class prediction model was developed to differentiate MCD and FSGS patients. The validation of this model correctly classified 81.8% (9/11) of MCD patients and 72.7% (8/11) of FSGS patients. Moreover, the signal with m/z 1913.60, identified as a fragment of uromodulin, and the signal with m/z 2392.54, identified as a fragment of alpha-1-antitrypsin, showed higher and lower peak areas, respectively, in FSGS patients compared with MCD patients.

CONCLUSIONS

The simple, non-invasive technique described in the present study may be a useful tool to help clinicians by confirming diagnoses achieved by renal biopsy, thereby reducing misdiagnoses and avoiding the implementation of inappropriate therapies.

Effects of nebivolol and atenolol on central aortic pressure in hypertensive patients: a multicenter, randomized, double-blind study

INTRODUCTION

The main objective was to compare the mean change in augmentation index of hypertensive patients treated with nebivolol or atenolol.

METHODS

Multicenter, double-blind randomized study conducted in six Spanish centers. We enrolled outpatients between the ages of 40 and 65 years with mild or moderate essential hypertension (systolic blood pressure, SBP ≥ 140 mmHg to ≤ 179 mmHg and diastolic blood pressure, DBP ≥ 90 mmHg to ≤ 109 mmHg after a 2-week run-in placebo period). Patients received nebivolol 5 mg or atenolol 50 mg once daily. At week 3, atenolol could be titrated up to 100 mg qd for non-responders. Additionally, patients not achieving normal blood pressure after 6 weeks could be treated with 25 mg hydrochlorothiazide. Follow-up visits were at 3, 6 and 10 weeks.

RESULTS

The final study population of 138 patients (58% men; median age 52.6 years, range 40-67 years) was randomized into two groups of 69 patients each. Baseline characteristics of the two groups were similar. At the screening visit, 69% presented with mild hypertension. Nebivolol modified the mean augmentation index to a lesser extent than atenolol after 10 weeks (mean difference 3.1%, 95% CI 0.55-5.69; p = 0.027). A higher proportion of patients in the atenolol group required a diuretic. Reductions in central aortic pressure and peripheral arterial pressure were similar for both treatment groups.

CONCLUSIONS

The study confirms that nebivolol produces a less pronounced impact on augmentation index than atenolol.

Poor histological lesions in IgA nephropathy may be reflected in blood and urine peptide profiling

Background

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, leading to renal failure in 15% to 40% of cases. IgAN is diagnosed by renal biopsy, an invasive method that is not risk-free. We used blood and urine peptide profiles as a noninvasive method of linking IgAN-associated changes with histological lesions by Oxford classification.

Methods

We prospectively studied 19 patients with biopsy-proven IgAN and 14 healthy subjects from 2006 to 2009, excluding subjects with crescentic glomerulonephritis and collecting clinical and biochemical data at the time of diagnosis and during follow-up (24 months). Histological lesions were evaluated by Oxford classification. Proteomic analysis was performed by combining magnetic bead (MB) technology and mass spectrometry (MALDI-TOF MS) to obtain peptide profiles. Doubling of serum creatinine was considered a variable of poor renal prognosis.

Results

We identified 55 peptides—13 in serum, 26 in plasma, and 16 in urine—that differentiated IgAN patients from healthy subjects. A significant association was noted between serum/plasma and urine peptides and histological findings—ie, tubulointerstitial damage, segmental glomerulosclerosis, and endocapillary injury.

We also identified 3 peptides—corresponding to bradykinin, uromodulin, and alpha-1-antitrypsin—that were associated with severity of lesions, such as tubulointerstitial damage and segmental glomerulosclerosis.

Moreover, blood peptides with m/z 2953, 5337, 9287, and 9289 and urine peptides with m/z 1769, 1898, 1913, 1945, 2491, 2756, 2977, 3004, 3389, and 4752 correlated significantly with poor renal function.

Conclusions

In patients with IgAN, the use of noninvasive approaches, such as blood and urine proteomics, can provide valuable information beyond that of standard diagnostic techniques, allowing us to identify blood and urine peptide profiles that are associated with poor histological lesions in IgAN patients.

Metabolic syndrome in hemodialysis patients as a risk factor for new-onset diabetes mellitus after renal transplant: a prospective observational study

PURPOSE

Metabolic syndrome is a cluster of biochemical abnormalities including cardiovascular and diabetes risk factors. The development of diabetes mellitus after renal transplant represents a major posttransplant complication that may adversely affect graft/patient survival. The aim of this study was to assess the role of metabolic syndrome in patients on hemodialysis as a risk factor for the incidence of new-onset diabetes mellitus after renal transplant.

PATIENTS AND METHODS

This was a prospective observational epidemiologic study carried out in adult nondiabetic patients undergoing chronic hemodialysis and on the renal transplant waiting list between November 2008 and April 2009. Patients were followed up from Visit 1 (baseline) to 6 months after the renal transplant. The analysis of the role of metabolic syndrome in hemodialysis patients as a risk factor for the incidence of new-onset diabetes mellitus after renal transplant included the estimation of relative risk and its 95% confidence interval (CI).

RESULTS

A total of 383 evaluable patients were entered into the study (mean age, 52.7 years; male, 57.7%; Caucasian, 90.1%). The prevalence of metabolic syndrome on hemodialysis was 30.4% (95% CI, 25.8%-35.4%). Hypertension was the most prevalent criterion for metabolic syndrome (65.0%), followed by low levels of high-density lipoprotein cholesterol (52.7%), abdominal obesity (36.2%), hypertriglyceridemia (32.4%), and impaired glucose (8.9%). After the renal transplant, the prevalence of metabolic syndrome was still 25.8%. During the posttransplant period, the incidence of new-onset diabetes mellitus reached 13.0% (95% CI, 7.8%-20.6%) and patients with pretransplant metabolic syndrome were 2.6 times (95% CI, 1.043-6.608) more likely to develop new-onset diabetes mellitus after the renal transplant than those without metabolic syndrome.

CONCLUSION

The presence of metabolic syndrome in patients undergoing hemodialysis represents an independent risk factor for the incidence of new-onset diabetes mellitus after renal transplant.

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.

The formation of wrinkles in single-layer graphene sheets under nanoindentation

We investigate the formation of wrinkles and bulging in single-layer graphene sheets using an equivalent atomistic continuum nonlinear hyperelastic theory for nanoindentation and nanopressurization. We show that nonlinear geometrical effects play a key role in the development of wrinkles. Without abandoning the classical tension field membrane theory, we develop an enhanced model based upon the minimization of a relaxed energy functional in conjunction with nonlinear finite hyperelasticity. Formation of wrinkles are observed in rectangular graphene sheets due to the combination of induced membrane tension and edge effects under external pressure.

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

Statins are prescribed to reduce posttransplant dyslipidemia, which is frequent among kidney graft recipients. Their efficacy to reduce cholesterol levels has been accompanied by pleiotropic effects. Proteomics is the study of the expressed complement of proteins in tissues or biological fluids. It includes the identification of changes in proteins that occur in various states, eg, after drug administration. Our study objectives were: (1) to analyze the effect of atorvastatin (10 mg/d) on lipid profile, renal function, proteinuria, and inflammation parameters, such as C-reactive protein (CRP), and (2) to use proteomics to ascertain whether this treatment modified the patients' urinary peptide profiles seeking to understand the molecular actions of the drug. Urinary peptide profiles, lipids, renal function parameters (creatinine clearance), proteinuria, and CRP were determined in 39 patients at baseline and at 12 weeks after atorvastatin treatment (10 mg/d). The peptide fraction of each sample acquired using magnetic beads was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Our results showed that treatment with atorvastatin produced a significant reduction in lipid profile, but did not modify renal function (creatinine clearance), proteinuria, or CRP. The proteomic study showed that statin treatment did not produce significant changes in the urinary peptidome, although there was a tendency for some peptides to increase or decrease after the treatment.