Physical activity and exercise programs for kidney patients: an Italian survey of nephrology centres

BACKGROUND

Data on exercise activities in place, and on the interest for developing them in Nephrology Services in Italy is limited. To address this gap, we carried out this cross-sectional study to investigate the status of physical activity and exercise programs available in Italian Nephrology Centres. Additionally, research priorities on this topic were examined.

METHODS

We developed a 14-item electronic survey, which consisted of multiple-choice questions covering exercise training programs, physical assessment, barriers to exercise practice and to exercise programs, exercise and physical activity counselling practices, perceived exercise benefits, literature evidence, and research priorities. Data on the characteristics of the centres were also collected.

RESULTS

Sixty-two responses from Italian nephrology centres were collected. Ninety-three percent of the respondents were aware of the scientific evidence supporting the benefits of regular exercise programs for chronic kidney disease (CKD) patients. Additionally, in 75% of centres the nephrologists believed that physical activity counselling should be performed by the nephrologists. However, only 26% of centres provided exercise programs, mainly for dialysis patients, and 63% never or infrequently assessed physical activity in the context of patient management. Eighty-nine percent of centres reported barriers to implementing exercise programs, including lack of funding, institutional disinterest, patient refusal, and negative attitudes of the healthcare personnel. Forty-six research priorities related to exercise in CKD patients were suggested, with the majority focusing on impact of exercise programs and physical activity on cardiovascular, nutritional, and psychosocial outcomes.

CONCLUSION

This survey highlights the limited availability of exercise programs and physical activity evaluation in clinical practice in Italian Nephrology Centres. However, the survey also revealed a strong interest for counselling CKD patients on physical activity and implementing exercise prescriptions and interventions.

Childhood Obesity: Insight into Kidney Involvement

This review examines the impact of childhood obesity on the kidney from an epidemiological, pathogenetic, clinical, and pathological perspective, with the aim of providing pediatricians and nephrologists with the most current data on this topic. The prevalence of childhood obesity and chronic kidney disease (CKD) is steadily increasing worldwide, reaching epidemic proportions. While the impact of obesity in children with CKD is less pronounced than in adults, recent studies suggest a similar trend in the child population. This is likely due to the significant association between obesity and the two leading causes of end-stage renal disease (ESRD): diabetes mellitus (DM) and hypertension. Obesity is a complex, systemic disease that reflects interactions between environmental and genetic factors. A key mechanism of kidney damage is related to metabolic syndrome and insulin resistance. Therefore, we can speculate about an adipose tissue-kidney axis in which neurohormonal and immunological mechanisms exacerbate complications resulting from obesity. Adipose tissue, now recognized as an endocrine organ, secretes cytokines called adipokines that may induce adaptive or maladaptive responses in renal cells, leading to kidney fibrosis. The impact of obesity on kidney transplant-related outcomes for both donors and recipients is also significant, making stringent preventive measures critical in the pre- and post-transplant phases. The challenge lies in identifying renal involvement as early as possible, as it is often completely asymptomatic and not detectable through common markers of kidney function. Ongoing research into innovative technologies, such as proteomics and metabolomics, aims to identify new biomarkers and is constantly evolving. Many aspects of pediatric disease progression in the population of children with obesity still require clarification. However, the latest scientific evidence in the field of nephrology offers glimpses into various new perspectives, such as genetic factors, comorbidities, and novel biomarkers. Investigating these aspects early could potentially improve the prognosis of these young patients through new diagnostic and therapeutic strategies. Hence, the aim of this review is to provide a comprehensive exploration of the pathogenetic mechanisms and prevalent pathological patterns of kidney damage observed in children with obesity.

Hyperkalemia in CKD: an overview of available therapeutic strategies

Hyperkalemia (HK) is a life-threatening condition that often occurs in patients with chronic kidney disease (CKD). High serum potassium (sKsK) is responsible for a higher risk of end-stage renal disease, arrhythmias and mortality. This risk increases in patients that discontinue cardio-nephroprotective renin-angiotensin-aldosterone system inhibitor (RAASi) therapy after developing HK. Hence, the management of HK deserves the attention of the clinician in order to optimize the therapeutic strategies of chronic treatment of HK in the CKD patient. The adoption in clinical practice of the new hypokalaemic agents patiromer and sodium zirconium cyclosilicate (SZC) for the prevention and chronic treatment of HK could allow patients, suffering from heart failure and chronic renal failure, to continue to benefit from RAASi therapy. We have updated a narrative review of the clear variables, correct definition, epidemiology, pathogenesis, etiology and classifications for HK among non-dialysis CKD (ND CKD) patients. Furthermore, by describing the prognostic impact on mortality and on the progression of renal damage, we want to outline the strategies currently available for the control of potassium (K+) plasma levels.

A Rare Complication of Ascariasis: A Case of Acute Interstitial Nephritis

Acute interstitial nephritis (AIN) due to helminths is a rare cause of acute kidney injury (AKI). Helminthiases often progresses insidiously, making diagnosis difficult. This was the case of a 72-year-old man, who presented with renal failure, itching and diarrhoea. Urinalysis revealed leukocyturia, microhaematuria and mild proteinuria. A full blood count revealed leucocytosis with eosinophilia. A stool parasitological examination revealed fertilised eggs of Ascaris lumbricoides. Tubulointerstitial nephropathy secondary to A. lumbricoides infection was suspected. A percutaneous renal biopsy was not performed since the patient refused the anti-platelet therapy discontinuation. Mebendazole, albendazole and prednisone therapy was administered. After worm eradiation and discharge, recovery from the parasitosis, absence of pruritus and eosinophilia, and progressive improvement of renal function were observed, strongly suggesting a causal relationship between Ascaris infection and AIN. Parasite infection should be considered in the differential diagnosis of unexplained renal failure because early diagnosis and treatment are necessary to avoid irreversible complications.

The Impact of Chronic Kidney Disease on Peripheral Artery Disease and Peripheral Revascularization

Chronic kidney disease (CKD) is a clinical condition characterized by high morbidity and mortality. Globally, CKD is also increasing in prevalence and incidence. The two principal kidney measures namely estimated glomerular filtration rate (eGFR) and albuminuria have been found to be predictors of renal and cardiovascular (CV) endpoints including peripheral artery disease (PAD). The prevalence of PAD was increased in CKD patients and, particularly, in patients with more severe CKD stages. Despite the fact that revascularization strategies are suitable in CKD patients in similar fashion to non-CKD patients, few CKD patients underwent these procedures. In fact, if it is true that revascularization improves prognosis in PAD patients irrespective of baseline eGFR, it was also demonstrated that CKD patients, who underwent revascularization, were at higher risk for amputations, mortality, re-intervention and perioperative complications. With the present review article, we have examined the association between CKD, PAD and peripheral revascularization highlighting data about epidemiology, pathophysiologic mechanisms, and results from previous observational and intervention studies. We have also examined the future perspectives and challenges of research around the association between CKD and PAD.

MO156THE ‘WITHIN-DAY’ VARIABILITY OF ALBUMINURIA INFLUENCES THE MONITORING OF NEPHROPROTECTIVE TREATMENT EFFECT

Background and Aims

Measurement of urine proteins, mainly through the 24-hour excretion or the albumin-to-creatinine ratio (ACR) has become crucial in current clinical practice in Nephrology. Besides being a biomarker of injury, albuminuria also exerts direct pro-inflammatory and pro-fibrotic effects on renal tubules. Hence, a large number of intervention studies have been aimed at lowering albuminuria levels in patients with Chronic Kidney Disease (CKD). However, albuminuria is a measure characterized by a random variability that has been evaluated in several mechanistic and experimental studies and may be influenced by several factors, such as posture, exercise and dietary factors. The aim of the present study was to evaluate the within-day variability, specifically in a cohort of CKD outpatients who were on Renin-Angiotensin-Aldosterone-System inhibitors (RAASi) therapy.

Method

We enrolled consecutive CKD patients referred to the Nephrology Unit at Magna Graecia University Hospital of Catanzaro between January 1st and March 30th 2020. Inclusion criteria were: age > 18 years, diagnosis of CKD from any cause, presence of albuminuria in the range 150-3500 mg/g at screening. Patients already treated with RAASi, patients with active malignancy/signs of glomerulonephritis requiring immunosuppressive therapies, were excluded. At screening visit, patients with increased albuminuria were started with an Angiotensin Converting Enzyme inhibitor (ACEi) or an Angiotensin II Receptor Blocker (ARB). A second ambulatory visit was scheduled 1 month after start of RAASi therapy. During this visit, patients were asked to stay in the Renal Unit for 12 hours. They collected urine void for ACR, protein-to-creatinine ratio (PCR) and urine creatinine (Ucreat) assessment at 8am,1pm and 6pm. For each patient, comparisons between ACR, PCR and Ucreat were assessed by Kruskal-Wallis test and Friedman post-hoc, using the Benjamini-Hochberg as adjustment method. Coefficients of variation (CV,standard deviation/mean) were also computed.

Results

Final analysis included 43 patients (46.5% of males). Mean age was 59.6±16.7 years and median eGFR 41 [21-74] mL/min/1.73m2. A high cardiovascular (CV) risk profile was testified by the prevalence of type 2 diabetes (30.2%) and previous CV disease (34.8%). When patient characteristics were compared across ACR categories (<30, 30-300, >300 mg/g), systolic blood pressure was increased (p=0.020) and mean age decreased from 68.0 to 54.8 years on average (p=0.038). ACR values collected were 189 [38-759], 252 [51-1685] and 229 [56-1185] mg/g at 8am, 1pm and 6pm, respectively, with a CV of 24.6% (95%CI 12.4-39.1). 8am ACR was significantly different from 1pm ACR (p<0.001) and from 6pm ACR (p<0.001). 1 pm ACR was significantly different from 6pm ACR (p=0.002). Median PCR were 335 [115-932], 429 [146-1811] and 447 [151-1465] mg/g respectively at 8am, 1pm and 6pm, with CV being 17.8% (95%CI 9.0-26.6). 8am PCR differed significantly from 1pm and 6pm PCR (p<0.001 for both), while 1pm ACR was lower than 6pm ACR (p<0.001). Ucreat was 66 [53-103], 63 [47-96] and 69 [50-90] mg/dL respectively at 8am, 1pm and 6pm with no significant variation trend. Individual within-day ACR and PCR trends are depicted in the Figure .

Conclusion

The present analysis showed a significant individual within-day variability of albuminuria, measured as both ACR and PCR, suggesting that another parameter, in addition to those already known, may be responsible for the day-by-day albuminuria variation. Moreover, the absence of variability in Ucreat, namely the denominator of the ACR/PCR formula, suggests that the true variation is likely dependent on the urine protein values. Thus, albuminuria reduction in response to RAASi treatment should be carefully evaluated by measuring ACR/PCR preferentially at a similar time of the day for each patient. This would allow to avoid under- or overestimation of the actual treatment effect.

Darbepoetin alfa reduces cell death due to radiocontrast media in human renal proximal tubular cells

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Radiocontrast medium, sodium diatrizoate, reduces renal cell viability in vitro.

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Effect of darbepoetin on diatrizoate-treated cells was studied.

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Pre-treatment of renal cells with darbepoetin could reduce diatrizoate toxicity.

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Darbepoetin caused changes in the activation state of signaling molecules.

The hypersialylated erythropoiesis stimulating agent (ESA) darbepoetin alfa was developed for the treatment of anemia, and has also been reported to have other nonerythropoietic effects. This study outlines one such effect against the toxicity of the radiocontrast medium (RCM) sodium diatrizoate (NaD) in human renal proximal tubular (HK-2) cells in vitro. Using a standard cell viability assay, we observed that pre-incubation of HK-2 cells with darbepoetin (at concentrations of 0.25and 1.0 μg/mL) for 2.5 h prior to addition of NaD (75 mg I/mL, for 2 h) reduced the decrease in cell viability due to the RCM, assayed 22 h after removal of the NaD, whilst maintaining the cells incubated with darbepoetin. Western blot analysis showed that darbepoetin reduced the phosphorylation of c-Jun N-terminal kinases (JNK)1/2 over a period of 1 h incubation with NaD, but did not have an obvious effect on several other targets associated with cell death/survival. However, incubation of HK-2 cells with darbepoetin for a further 22 h after prior exposure to NaD (75 mg I/mL, for 2 h) and subsequent immunoblotting showed that darbepoetin: caused recovery of the activity (phosphorylation) of pro-proliferative/survival signalling molecules, such as Akt (Ser473), STAT (signal transducer and activator of transcription)3(Tyr705); decreased activation of the pro-apoptotic transcription factor FOXO3a by increasing its phosphorylation at Thr32; decreased phosphorylation (activation) of p38 Mitogen activated protein kinase; and reduced poly(ADP-ribose)polymerase (PARP)-1 cleavage. In summary, we present here a beneficial nonerythropoietic effect of darbepoetin alfa against radiocontrast-induced toxicity together with modulation of signalling molecules that play a crucial role in determining cell fate.

Aortic Aneurysms, Chronic Kidney Disease and Metalloproteinases

Metalloproteinases (MPs) are proteolytic enzymes involved in extracellular matrix deposition, regulation of cellular signals of inflammation, proliferation, and apoptosis. Metalloproteinases are classified into three families: Matrix-MPs (MMPs), A-Disintegrin-and-Metalloprotease (ADAMs), and the A-Disintegrin-and-Metalloproteinase-with-Thrombospondin-1-like-Domains (ADAMTS). Previous studies showed that MPs are involved in the development of aortic aneurysms (AA) and, concomitantly, in the onset of chronic kidney disease (CKD). CKD has been, per se, associated with an increased risk for AA. The aim of this review is to examine the pathways that may associate MPs with CKD and AA. Several MMPs, such as MMP-2, -8, -9, and TIMP-1 have been shown to damage the AA wall and to have a toxic effect on renal tubular cells, leading to fibrosis. Similarly, ADAM10 and 17 have been shown to degrade collagen in the AA wall and to worsen kidney function via pro-inflammatory stimuli, the impairment of the Renin-Angiotensin-Aldosterone System, and the degradation of structural proteins. Moreover, MMP-2 and -9 inhibitors reduced aneurysm growth and albuminuria in experimental and human studies. It would be important, in the future, to expand research on MPs from both a prognostic, namely, to refine risk stratification in CKD patients, and a predictive perspective, likely to improve prognosis in response to targeted treatments.

Precision Medicine and Precision Nursing: The Era of Biomarkers and Precision Health

Precision health, by means of the support of precision medicine and precision nursing, is able to support clinical decision making in order to tailor optimal health-care decisions, around the individual characteristics of patients. The operational arm of precision health is represented by the use of biomarkers that can give useful information about disease susceptibility, exposure, evolution and response to treatment. Omics, imaging and clinical biomarkers are actually studied for their ability to positively impact health-care management. In this article, we try to address the role of biomarkers in the context of modern medicine and nursing with the view of improving patients care.

Renal resistive index in chronic kidney disease patients: Possible determinants and risk profile

BACKGROUND

High ultrasound renal resistive index (RI) predicts poor cardiorenal outcomes in chronic kidney disease (CKD) and has recently emerged as a marker of nephroprotective drugs response. Thus, having a risk profile of CKD patients with abnormal RI may be relevant for the clinicians.

METHODS

Consecutive patients referred to our non-dialysis CKD clinic from 01/01/2016 to 01/12/2016, were evaluated by clinical and ultrasound analysis. Inclusion criteria were age >18 years and presence of CKD defined as estimated glomerular filtration rate (eGFR)<60 mL/min/1.73m2 and/or proteinuria>0.150g/24h. Renal artery stenosis, solitary kidney, acute kidney injury were the main exclusion criteria. RI value was the mean of three measures in segmental arteries in each kidney. Univariate analysis was performed to evaluate associations between continuous RI and clinical variables. Multivariate linear regression analysis, based on stepwise method with an elimination criterion of p<0.10, was used to assess the independent correlates of RI as continuous variable.

RESULTS

We studied 73 patients (69.9% men). Mean RI was 0.67±0.09. Frequencies of diabetes and cardiovascular disease (CVD) were 19.2% and 20.6% and median eGFR 54.1 [30.0-84.6] mL/min/1.73m2. From low (<0.65) to intermediate (0.65-0.70) to high (>0.70) RI categories, eGFR and haemoglobin levels were decreased while diabetes, cardiovascular disease (CVD), phosphate and smokers were higher. At univariate analysis, RI was significantly associated with age, presence of diabetes, CVD, serum phosphorus, eGFR, Urea and haemoglobin. Multi-adjusted stepwise regression analysis showed that lower eGFR levels (p<0.001), diabetes (p = 0.042), CVD (p = 0.009), smoking habit (p = 0.021) and higher serum phosphorus levels (p = 0.001) were associated with higher continuous RI. Serum phosphorus showed Area Under the Curves (AUC) values of 0.714 and 0.664 for discriminating RI cut-offs of 0.70 and 0.65.

CONCLUSIONS

This analysis suggests that RI is higher in CKD patients with CVD, diabetes, smoking habit and higher serum phosphorus, regardless of eGFR. Further studies are needed to verify whether higher RI indicates more complex pathway of intrarenal damage, besides and beyond kidney function.

The Association of Matrix Metalloproteinases with Chronic Kidney Disease and Peripheral Vascular Disease: A Light at the End of the Tunnel?

: Chronic Kidney Disease (CKD) represents a risk factor for fatal and nonfatal cardiovascular (CV) events, including peripheral vascular disease (PVD). This occurs because CKD encompasses several factors that lead to poor prognoses, mainly due to a reduction of the estimated glomerular filtration rate (eGFR), the presence of proteinuria, and the uremic inflammatory milieu. The matrix metalloproteinases (MMPs) are a group of zinc-containing endopeptidases implicated in extracellular matrix (ECM) remodeling, a systemic process in tissue homeostasis. MMPs play an important role in cell differentiation, angiogenesis, inflammation, and vascular damage. Our aim was to review the published evidence regarding the association between MMPs, PVD, and CKD to find possible common pathophysiological mechanisms. MMPs favor ECM deposition through the glomeruli, and start the shedding of cellular junctions and epithelial-mesenchymal transition in the renal tubules. MMP-2 and -9 have also been associated with the presence of systemic vascular damage, since they exert a pro-inflammatory and proatherosclerotic actions. An imbalance of MMPs was found in the context of PVD, where MMPs are predictors of poor prognoses in patients who underwent lower extremity revascularization. MMP circulating levels are increased in both conditions, i.e., that of CKD and PVD. A possible pathogenic link between these conditions is represented by the enhanced production of transforming growth factor-β that worsens vascular calcifications and atherosclerosis and the development of proteinuria in patients with increased levels of MMPs. Proteinuria has been recognized as a marker of systemic vascular damage, and this may explain in part the increase in CV risk that is manifest in patients with CKD and PVD. In conclusion, MMPs can be considered a useful tool by which to stratify CV risk in patients with CKD and PVD. Further studies are needed to investigate the causal-relationships between MMPs, CKD, and PVD, and to optimize their prognostic and predictive (in response to treatments) roles.

Quercetin protects against radiocontrast medium toxicity in human renal proximal tubular cells

Radiocontrast media (RCM)-induced acute kidney injury (CI-AKI) is a major clinical problem whose pathophysiology is not well understood. Direct toxic effects on renal cells, possibly mediated by reactive oxygen species, have been postulated as contributing to CI-AKI. We investigated the effect of quercetin on human renal proximal tubular (HK-2) cells treated with the radiocontrast medium (RCM) sodium diatrizoate. Quercetin is the most widely studied flavonoid, and the most abundant flavonol present in foods. It has been suggested to have many health benefits, including angioprotective properties and anti-cancer effects. These beneficial effects have been attributed to its antioxidant properties and its ability to modulate cell signaling pathways. Incubation of HK-2 cells with 100 μM quercetin caused a decrease in cell viability and pre-treatment of HK-2 cells with 100 μM quercetin followed by incubation with 75 mgI/ml sodium diatrizoate for 2 hr caused a decrease in cell viability which was worse than in cells treated with diatrizoate alone. However, further incubation of the cells (for 22 hr) after removal of the diatrizoate and quercetin caused a recovery in cell viability in those cells previously treated with quercetin + diatrizoate and quercetin alone. Analysis of signaling molecules by Western blotting showed that in RCM-treated cells receiving initial pre-treatment with quercetin, followed by its removal, an increase in phosphorylation of Akt (Ser473), pSTAT3 (Tyr705), and FoxO3a (Thr32) as well as an induction of Pim-1 and decrease in PARP1 cleavage were observed. Quercetin may alleviate the longer-term toxic effects of RCM toxicity and its possible beneficial effects should be further investigated.

Update on the renal toxicity of iodinated contrast drugs used in clinical medicine

An important side effect of diagnostic contrast drugs is contrast-induced acute kidney injury (CI-AKI; a sudden decrease in renal function) occurring 48-72 hours after injection of a contrast drug that cannot be attributed to other causes. Its existence has recently been challenged, because of some retrospective studies in which the incidence of AKI was not different between subjects who received a contrast drug and those who did not, even using propensity score matching to prevent selection bias. For some authors, only patients with estimated glomerular filtration rate <30 mL/min/1.73 m2 are at significant risk of CI-AKI. Most agree that when renal function is normal, there is no CI-AKI risk. Many experimental studies, however, are in favor of the existence of CI-AKI. Contrast drugs have been shown to cause the following changes: renal vasoconstriction, resulting in a rise in intrarenal resistance (decrease in renal blood flow and glomerular filtration rate and medullary hypoxia); epithelial vacuolization and dilatation and necrosis of proximal tubules; potentiation of angiotensin II effects, reducing nitric oxide (NO) and causing direct constriction of descending vasa recta, leading to formation of reactive oxygen species in isolated descending vasa recta of rats microperfused with a solution of iodixanol; increasing active sodium reabsorption in the thick ascending limbs of Henle's loop (increasing O2 demand and consequently medullary hypoxia); direct cytotoxic effects on endothelial and tubular epithelial cells (decrease in release of NO in vasa recta); and reducing cell survival, due to decreased activation of Akt and ERK1/2, kinases involved in cell survival/proliferation. Prevention is mainly based on extracellular volume expansion, statins, and N-acetylcysteine; conflicting results have been obtained with nebivolol, furosemide, calcium-channel blockers, theophylline, and hemodialysis.

The ischemic/nephrotoxic acute kidney injury and the use of renal biomarkers in clinical practice

The term Acute Renal Failure (ARF) has been replaced by the term Acute Kidney Injury (AKI). AKI indicates an abrupt (within 24-48h) decrease in Glomerular Filtraton Rate, due to renal damage, that causes fluid and metabolic waste retention and alteration of electrolyte and acid-base balance. The renal biomarkers of AKI are substances or processes that are indicators of normal or impaired function of the kidney. The most used renal biomarker is still serum creatinine that is inadequate for several reasons, one of which is its inability to differentiate between hemodynamic changes of renal function ("prerenal azotemia") from intrinsic renal failure or obstructive nephropathy. Cystatin C is no better in this respect. After the description of the pathophysiology of "prerenal azotemia" and of Acute Kidney Injury (AKI) due to ischemia or nephrotoxicity, the renal biomarkers are listed and described: urinary NAG, urinary and serum KIM-1, serum and urinary NGAL, urinary IL-18, urinary L-FABP, serum Midkine, urinary IGFBP7 and TIMP2, urinary α-GST and π-GST, urinary ɣGT and AP, urinary β₂M, urinary RBP, serum and urinary miRNA. All have been shown to appear much earlier than the rise of serum Creatinine. Some of them have been demonstrated to predict the clinical outcomes of AKI, such as the need for initiation of dialysis and mortality.

The potential use of biomarkers in predicting contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI) is a problem associated with the use of iodinated contrast media, causing kidney dysfunction in patients with preexisting renal failure. It accounts for 12% of all hospital-acquired kidney failure and increases the length of hospitalization, a situation that is worsening with increasing numbers of patients with comorbidities, including those requiring cardiovascular interventional procedures. So far, its diagnosis has relied upon the rise in creatinine levels, which is a late marker of kidney damage and is believed to be inadequate. Therefore, there is an urgent need for biomarkers that can detect CI-AKI sooner and more reliably. In recent years, many new biomarkers have been characterized for AKI, and these are discussed particularly with their use in known CI-AKI models and studies and include neutrophil gelatinase-associated lipocalin, cystatin C (Cys-C), kidney injury molecule-1, interleukin-18, N-acetyl-β-d-glucosaminidase, and L-type fatty acid-binding protein (L-FABP). The potential of miRNA and metabolomic technology is also mentioned. Early detection of CI-AKI may lead to early intervention and therefore improve patient outcome, and in future any one or a combination of several of these markers together with development in technology for their analysis may prove effective in this respect.

Acute kidney injury by radiographic contrast media: pathogenesis and prevention

It is well known that iodinated radiographic contrast media may cause kidney dysfunction, particularly in patients with preexisting renal impairment associated with diabetes. This dysfunction, when severe, will cause acute renal failure (ARF). We may define contrast-induced Acute Kidney Injury (AKI) as ARF occurring within 24-72 hrs after the intravascular injection of iodinated radiographic contrast media that cannot be attributed to other causes. The mechanisms underlying contrast media nephrotoxicity have not been fully elucidated and may be due to several factors, including renal ischaemia, particularly in the renal medulla, the formation of reactive oxygen species (ROS), reduction of nitric oxide (NO) production, and tubular epithelial and vascular endothelial injury. However, contrast-induced AKI can be prevented, but in order to do so, we need to know the risk factors. We have reviewed the risk factors for contrast-induced AKI and measures for its prevention, providing a long list of references enabling readers to deeply evaluate them both.

Differential activation of signaling pathways by low-osmolar and iso-osmolar radiocontrast agents in human renal tubular cells

Radiocontrast media (RCM)-induced nephrotoxicity (CIN) is a major clinical problem accounting for 12% of all hospital-acquired cases of acute kidney injury (AKI). The pathophysiology of AKI due to RCM is not well understood, but direct toxic effects on renal cells have been postulated as contributing to CIN. It is believed that iso-osmolar RCM (IOCM) are less nephrotoxic than low-osmolar RCM (LOCM) but clinical data have been controversial. We have investigated the intracellular signaling pathways that may be affected by the LOCM iomeprol (IOM) and the IOCM iodixanol (IOD). Both IOM and IOD caused a dramatic decrease in phosphorylation of the kinase Akt at Ser473 and Thr308 in human renal tubular (HK-2) cells, with IOM having a greater effect; IOM also caused a greater decrease in cell viability. IOM also had a greater effect on phosphorylation of p38 MAP kinases, JNKs, and NF-kB (Ser276), and caused a marked decrease in the phosphorylation of forkhead box O3a (FOXO3a) and signal transducer and activator of transcription 3 (STAT3). However, IOD caused a greater decrease in the phosphorylation of mTOR (Ser2448) and phospho-ERK 1/2 while both RCM caused a similar decrease in the phosphorylation of phospho-p70S6 kinase (Ser371). In vivo studies showed that both IOM and IOD caused a significant decrease in both pAkt (Ser473) and pERK 1/2 in rat kidneys. Our study gives an insight into the possible mechanism of toxicity of RCM via their action on intracellular signaling pathways and may help in developing pharmacological interventions for their side-effects.

Molecular mechanisms of renal cellular nephrotoxicity due to radiocontrast media

Modern iodinated radiocontrast media are all based on the triiodinated benzene ring with various chemical modifications having been made over the last few decades in order to reduce their toxicity. However, CIN remains a problem especially in patients with pre-existing renal failure. In vitro studies have demonstrated that all RCM are cytotoxic. RCM administration in vivo may lead to a decrease in renal medullary oxygenation leading to the generation of reactive oxygen species that may cause harmful effects to renal tissue. In addition, endothelin and adenosine release and decreased nitric oxide levels may worsen the hypoxic milieu. In vitro cell culture studies together with sparse in vivo rat model data have shown that important cell signalling pathways are affected by RCM. In particular, the prosurvival and proproliferative kinases Akt and ERK1/2 have been shown to be dephosphorylated (deactivated), whilst proinflammatory/cell death molecules such as the p38 and JNK kinases and the transcription factor NF- κ B may be activated by RCM, accompanied by activation of apoptotic mediators such as caspases. Increasing our knowledge of the mechanisms of RCM action may help to develop future therapies for CIN.

Differential activation of signaling pathways involved in cell death, survival and inflammation by radiocontrast media in human renal proximal tubular cells

Radiocontrast media (RCM) are widely used in clinical medicine but may lead to radiocontrast-induced nephropathy (RCIN). The pathogenesis of acute renal failure secondary to RCM is not fully understood, but direct toxic effects are believed to be a major cause of RCIN. We have investigated the effect of different types of RCM on signaling pathways known to play a role in cell death, survival, and inflammation. HK-2 cells were incubated with sodium diatrizoate and iomeprol (IOM) at a concentration of 75 mg I/ml for 2 h. Both RCM caused an increase in phosphorylation of p38 mitogen-activated protein kinase (MAPK) (p38) and c-Jun N-terminal kinases (JNKs) and NF-κB (at Ser 276), with sodium diatrizoate having a more drastic effect. Although cell viability was reduced significantly by both RCM, in cells pretreated with IOM the cell viability recovered over a 22-h time period after removal of the RCM. However, viability of diatrizoate-treated cells rose at 5 h but then fell at 22 h after removal of the RCM. The decrease in cell viability in diatrizoate-treated cells corresponded with an increase in phosphorylation of JNKs, p38, and NF-κB and a decrease in phosphorylation of Akt, signal transducer and activator of transcription 3, and forkhead box O3a, as well as poly (ADP-ribose) polymerase and caspase-3 cleavage. The recovery in viability of IOM-treated cells corresponded most notably with an increase in STAT3 phosphorylation and induction of Pim-1 kinase. There was also an increase in interleukin-8 release by diatrizoate-treated cells indicating the possibility of proinflammatory effects of RCM. A knowledge of the signaling pathways by which RCM exert their cytotoxic actions may help in finding future therapies for RCIN.

Downregulation of cell survival signalling pathways and increased cell damage in hydrogen peroxide-treated human renal proximal tubular cells by alpha-erythropoietin

OBJECTIVE

Erythropoietin has been shown to have a protective effect in certain models of ischaemia-reperfusion, and in some cases the protection has been correlated with activation of signalling pathways known to play a role in cell survival and proliferation. We have studied whether erythropoietin would overcome direct toxic effects of hydrogen peroxide (H(2)O(2)) treatment to human renal proximal tubular (HK-2) cells.

MATERIALS AND METHODS

HK-2 cells were incubated with H(2)O(2) (2 mm) for 2 h with or without erythropoietin at concentrations of 100 and 400 U/ml, and cell viability/proliferation was assessed by chemical reduction of MTT. Changes in phosphorylation state of the kinases Akt, glycogen synthase kinase-3beta (GSK-3beta), mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) were also analysed.

RESULTS

Cells incubated with H(2)O(2) alone showed a significant decrease in viability, which did not significantly change by addition of erythropoietin at concentration of 100 U/ml, but was further reduced when concentration of erythropoietin was increased to 400 U/ml. Phosphorylation state of the kinases Akt, GSK-3beta, mTOR and ERK1/ERK2 of H(2)O(2)-treated HK-2 cells was slightly altered in the presence of erythropoietin at concentration of 100 U/ml, but was significantly less in the presence of erythropoietin at a concentration of 400 U/ml. Phosphorylation of forkhead transcription factor FKHRL1 was diminished in cells incubated with H(2)O(2) and erythropoietin at a concentration of 400 U/ml.

CONCLUSIONS

Erythropoietin, at high concentrations, may significantly increase cellular damage in HK-2 cells subjected to oxidative stress, which may be due in part to decrease in activation of important signalling pathways involved in cell survival and/or cell proliferation.

Prevalence and severity of anaemia in patients with type 2 diabetic nephropathy and different degrees of chronic renal insufficiency

BACKGROUND/AIM

Type 2 diabetes mellitus is the single most common cause of chronic kidney disease (CKD); however its real impact on renal anaemia has not been established. The aim of this study was to evaluate whether onset, severity, and prevalence of anaemia during the course of CKD is different between type 2 diabetic and non-diabetic patients.

METHODS

We enrolled 281 patients with: (1) type 2 diabetes and no CKD (n = 75); (2) type 2 diabetes plus CKD (n = 106), and (3) CKD without type 2 diabetes (n = 100). According to K/DOQI guidelines, the patients with renal insufficiency (i.e., those with a glomerular filtration rate <60 ml/min) were subgrouped into three tertiles of CKD: (1) stage 3 (creatinine clearance 60-30 ml/min); (2) stage 4 (creatinine clearance 29-15 ml/min), and (3) stage 5 (creatinine clearance <15 ml/min).

RESULTS

Anaemia was observed in 16% of the diabetic patients without CKD; it was more frequent in the diabetic patients with CKD than in the non-diabetic patients with CKD (61.7 vs. 52%, p < 0.05). The comparison among the tertiles showed that the prevalence of anaemia was significantly higher only in diabetic CKD patients of stages 4 and 5. The prevalence was higher in females independently of type 2 diabetes mellitus. In diabetics with a normal renal function, the haemoglobin levels were higher than in diabetics and non-diabetics with CKD, but the diabetics showed lower levels of haemoglobin than non-diabetics at stage 3 and stage 4 of CKD.

CONCLUSIONS

Diabetic patients with CKD of stages 4 and 5 have a higher prevalence of anaemia than non-diabetic patients with comparable glomerular filtration rate. A higher awareness of this risk will allow earlier diagnosis and treatment.

Radiocontrast media cause dephosphorylation of Akt and downstream signaling targets in human renal proximal tubular cells

Radiocontrast medium induced nephrotoxicity is a major clinical problem. There is considerable interest in reducing the incidence of acute renal failure due to the use of radiocontrast media (RCM). Reduction of renal blood flow and direct toxic effect on renal tubular epithelial cells have been postulated as major causes of RCM nephropathy. Understanding the molecular mechanisms by which RCM cause cell damage may allow the development of pharmacological therapy to prevent their nephrotoxicity. In this work we have investigated the signaling pathways that may be affected by RCM. The incubation of human renal tubular proximal cells with sodium diatrizoate, iopromide and iomeprol caused a marked dephosphorylation of the kinase Akt on Ser473 within 5min of incubation. RCM also caused a decrease in cell viability, which was substantially alleviated by transfecting the cells with a constitutively active form of Akt. Further downstream targets of Akt, including the Forkhead family of transcription factors FKHR and FKHRL1, were also dephosphorylated by RCM at Thr24 and Thr32, respectively. The P70S6 kinase was also dephosphorylated at Thr389 and Ser371 by RCM. However there was a more dramatic decrease in phosphorylation of the phosphorylated form of mammalian target of rapamycin (mTOR) and of the extracellular-signal regulated kinases (ERK) 1/2 caused by sodium diatrizoate than by iopromide. These results demonstrate the effect of RCM on some intracellular signaling pathways that may allow understanding of the mechanism of their toxicity and may allow the development of strategies to overcome their adverse effects.