Luminal alkalinization attenuates proteinuria-induced oxidative damage in proximal tubular cells

Clinical efficacy of beraprost sodium in treating chronic kidney disease: A six-month prospective study

Objective

To investigate the clinical efficacy of beraprost sodium (BPS) in the treatment of chronic kidney disease (CKD).

Methods

In this single-centre, prospective, controlled, single-blind study, 252 patients diagnosed with CKD and treated at the Affiliated Hospital of Xuzhou Medical University were enrolled from September 2018 to June 2021. All participants were randomised into three groups: the control, BPS 40 μg, and BPS 20 μg groups. Both treatment groups were administered conventional therapy for 6 months. Renal function in the three groups was measured and compared 3 and 6 months post-treatment.

Results

1. Renal function in the BPS 20 μg and BPS 40 μg groups was better than that in the control group after 3 and 6 months of treatment. 2. After 3 months of treatment, the levels of serum creatinine (P = 0.043), cystatin C (P = 0.039), and 24 h urinary total protein (P = 0.041) in the BPS 40 μg group were significantly lower than those in the BPS 20 μg group, the eGFR (P = 0.046) level was higher than that in the BPS 20 μg group, and the index improvement rate was better than that in the BPS 20 μg group (P < 0.05). 3. After 6 months of treatment, the improvement in renal function in the BPS 20 μg group was close to that in the BPS 40 μg group (P > 0.05).

Conclusion

BPS improved renal function, reduced urinary protein levels, and delayed CKD progression. The clinical efficacy of BPS in the 40 μg group was faster than that in the BPS 20 μg group. The long-term use of BPS is effective in patients with CKD.

Increased risk of chronic kidney disease in uric acid stone formers with high neutrophil-to-lymphocyte ratio

Urolithiasis is associated with an increased risk of chronic kidney disease (CKD), irrespective of stone compositions. Chronic inflammation is an important factor for CKD progression. Neutrophil-to-lymphocyte ratio (NLR) has been recognized as a reliable biomarker of inflammation, yet its use in predicting renal deterioration in patients with urolithiasis remains limited. We aimed to explore whether the combination of stone composition and NLR could be useful as a predictor for CKD risk. A total of 336 stone formers with at least one stone submission for analysis were enrolled in the retrospective study. Stones were classified into uric acid and calcium groups. Renal functions were assessed at least one month after stone treatment. Uric acid stone formers had significantly lower estimated glomerular filtration rate (eGFR) compared with calcium stone formers (p < 0.001). NLR was significantly higher in uric acid stone formers (p = 0.005), and a significantly negative correlation (p < 0.001) between NLR and eGFR had been observed only in uric acid stone group. Univariate and multivariate logistic regression analyses showed that higher proportion of uric acid stone composition and higher NLR were both significantly associated with CKD risks. A nomogram integrating independent predictors was generated for CKD prediction, yielding an AUC of 0.811 (0.764-0.858). In conclusion, our study demonstrated that stone formers with higher proportion of uric acid composition and higher NLR levels were associated with higher CKD risk.

Comparison potassium sodium hydrogen citrate with sodium bicarbonate in urine alkalization: a prospective crossover-controlled trial

PURPOSE

Excessive alkalization will increase the incidence of nephrolithiasis. Sodium bicarbonate (NaHCO₃) and potassium sodium hydrogen citrate (PSHC) are commonly used drugs for urinary alkalization. We designed a trial to compare PSHC with NaHCO₃ in the urine alkalization for the Chinese healthy participants and to explore the effects of PSHC and NaHCO₃ on circadian rhythms of urine pH value.

METHOD

This study was a prospective, crossover, randomized, controlled trial, in which a total of 34 healthy volunteers participated in two study phases and took PSHC and NaHCO₃ at the maintenance dose, respectively.

RESULT

The average level of urine pH of PSHC participants in 24 h was significantly higher than that of NaHCO₃ (P < 0.001). The urine pH value of participants taking PSHC and NaHCO₃ or under physiological conditions showed significant variation in 24 h (P < 0.05) and fitted to a mathematical model (Fourier series). Under physiological conditions, the average urine pH value in the daytime was higher than that in the night, and reached the peak at about 10:00, 16:00, and 22:00. The peak of urine pH at 24 h after taking PSHC and NaHCO₃ was both higher than the baseline. The peak time of urine pH and the curve trend were similar, but the peak value in PSHC group was significantly higher than that in NaHCO₃ group.

CONCLUSIONS

There was a circadian rhythm of urine pH value under physiological conditions. PSHC was more effective in urinary alkalization than NaHCO₃ at the current maintenance oral dose and administration time without changing the rhythm of urine pH value.

CLINICAL TRIAL REGISTRATION

NCT04352153.

Association of acidic urine pH with impaired renal function in primary gout patients: a Chinese population-based cross-sectional study

Background

Patients with gout frequently have low urinary pH, which is associated with the nephrolithiasis. However, the specific distribution of urinary pH and potential relationship of acidic urine pH to broader manifestations of kidney disease in gout are still poorly understood.

Methods

A 2016–2020 population-based cross-sectional study was conducted among 3565 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University to investigate the association between low urinary pH and kidney disease. We studied patients that we defined to have “primary gout”, based on the absence of > stage 2 CKD. All subjects underwent 14 days of medication washout and 3-day standardized metabolic diet. We obtained general medical information, blood and urine biochemistries, and renal ultrasound examination on the day of the visit. The primary readouts were urine pH, eGFR, nephrolithiasis, renal cysts, microhematuria, and proteinuria. Patients were assigned into 5 subgroups (urine pH ≤5.0, 5.0 <pH≤ 5.5, 5.5 <pH< 6.2, 6.2 ≤pH≤ 6.9, and pH >6.9), aligning with the clinical significance of urine pH.

Results

Overall, the median urine pH and eGFR of all patients was 5.63 (IQR 5.37~6.09), and 98.32 (IQR 86.03~110.6), with acidic urine in 46.5% of patients. The prevalence of nephrolithiasis, microhematuria, and proteinuria were 16.9%, 49.5%, and 6.9%, respectively. By univariate analysis, eGFR was significantly associated with age, sex, duration of gout, tophus, body mass index, systolic blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, serum utare, hypertension, diabetes, and urine pH. On multivariable analysis, eGFR was associated with age, sex, diastolic blood pressure, serum uric acid, hypertension, diabetes, and urine pH. Acidic urine pH, especially urine pH < 5.0, was significantly associated with the prevalence of kidney disease, including > stage 1 CKD, nephrolithiasis, kidney cyst, and microhematuria. Patients with 6.2 ≤ urine pH ≤ 6.9 and SU ≤ 480 μmol/L had the highest eGFR with the lowest prevalence of nephrolithiasis, microhematuria, and proteinuria.

Conclusions

Approximately half of gout subjects had acidic urine pH. Urine pH < 5.0 was associated with significantly increased nephrolithiasis, renal cyst, microhematuria, and proteinuria. The results support prospective clinical investigation of urinary alkalinization in selected gout patients with acidic urine pH.

The efficacy and safety of citrate mixture vs sodium bicarbonate on urine alkalization in Chinese primary gout patients with benzbromarone: a prospective, randomized controlled study

Objectives

To compare the efficacy and safety of citrate mixture and sodium bicarbonate on urine alkalization in gout patients under benzbromarone treatment.

Methods

A prospective, randomized, parallel controlled trial was conducted among 200 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University. The participants were randomly divided into two groups (1:1), sodium bicarbonate group (3 g/day) and citrate mixture group (7 g/day). All patients were prescribed with 25 mg/day benzbromarone at initiation and maintained at a dose of 50 mg/day. Clinical and biochemical data were collected at each follow-up time point (baseline, weeks 2, 4, 8 and 12).

Results

A total of 182 patients completed the 12-week urine alkalization study. The urine pH value of both groups increased significantly from the baseline to the final follow-up time point (sodium bicarbonate group, 5.50–6.00, P < 0.05; citrate mixture group, 5.53–5.93, P < 0.05). While the comparisons regarding urine pH between treatment groups showed no significant differences for each time point. The estimated glomerular filtration rate (eGFR) dropped significantly after 12 weeks’ trial in the sodium bicarbonate group (P < 0.01), while it was comparable between baseline and the last follow-up (P > 0.05) in the citrate mixture group. Results of urine analysis showed that the incident rate of occult blood in the sodium bicarbonate group was higher than that in the citrate mixture group (38 vs 24%, P < 0.05), accompanied by a similar occurrence of kidney stones. After 12-week follow-up, the frequency of twice gout flare in the citrate mixture group was significantly lower than that in sodium bicarbonate group (4 vs 12%, P = 0.037). No treatment-emergent adverse events occurred.

Conclusion

The efficacy of citrate mixture on urine alkalization is comparable to sodium bicarbonate under benzbromarone treatment without significant adverse events. Citrate mixture is superior to sodium bicarbonate in lowering the incidence of urine occult blood and the frequency of gout attacks.

Trial registration

Registered with ChiCTR (http://www.chictr.org.cn), No. ChiCTR1800018518.

Oxidative Stress Markers in Chronic Kidney Disease with Emphasis on Diabetic Nephropathy

Diabetes prevalence is increasing worldwide, especially through the increase of type 2 diabetes. Diabetic nephropathy occurs in up to 40% of diabetic patients and is the leading cause of end-stage renal disease. Various factors affect the development and progression of diabetic nephropathy. Hyperglycaemia increases free radical production, resulting in oxidative stress, which plays an important role in the pathogenesis of diabetic nephropathy. Free radicals have a short half-life and are difficult to measure. In contrast, oxidation products, including lipid peroxidation, protein oxidation, and nucleic acid oxidation, have longer lifetimes and are used to evaluate oxidative stress. In recent years, different oxidative stress biomarkers associated with diabetic nephropathy have been found. This review summarises current evidence of oxidative stress biomarkers in patients with diabetic nephropathy. Although some of them are promising, they cannot replace currently used clinical biomarkers (eGFR, proteinuria) in the development and progression of diabetic nephropathy.

Reno-protective effects of oral alkalizing agents in chronic kidney disease with aciduria: protocol for a randomized cohort study

Background

Aciduria caused by urinary excretion of acidic metabolic wastes produced in daily life is known to be augmented in patients with chronic kidney disease (CKD). To evaluate the reno-protective effect of oral alkalizing agents for the improvement of metabolic acidosis and neutralization of intratubular pH in the patients with mild stages of CKD. Also, to identify reno-protective surrogate markers in the serum and urine that can closely associate the effect of urine alkalization.

Methods

In this single-centered, open-labeled, randomized cohort study, patients with CKD stages G2, G3a and G3b, who visited and were treated at Tohoku University Hospital during the enrollment period were registered. We administered sodium bicarbonate or sodium-potassium citrate as the oral alkalinizing agents. A total of 150 patients with CKD will be randomly allocated into the following three groups: sodium bicarbonate, sodium-potassium citrate and standard therapy group without any alkalinizing agents. The data of performance status, venous blood test, spot urine test, venous blood-gas test, electrocardiogram, renal arterial ultrasonography and chest X-ray will be collected at 0, 6, 12 and 24 weeks (short-term study) from starting the interventions. These data will be also collected at 1 and 2 years (long-term study). The samples of plasma and serum and early-morning urine at every visit will be acquired for the analysis of renal function and surrogate uremic biomarkers.

The recruitment for this cohort study terminated in March, 2018, and the follow-up period for all the enrolled subjects will be terminated in December, 2020. The primary endpoint will be the development of originally-defined significant renal dysfunction or the occurrence of any cerebrovascular disease in the short-term study. The secondary endpoint will be the same endpoints as in the long-term study, or the patients with significant changes in the suggested the surrogate biomarkers.

Discussion

The findings of this study will address the importance of taking oral alkalizing agents in the patients with early stages of CKD, furthermore they could address any new surrogate biomarkers that can be useful from early stage CKD.

Trial registration

Registered Report Identifier: UMIN000010059 and jRCT021180043.

The trial registration number; 150.

Date of registration; 2013/02/26.

Oxidative Stress in the Pathogenesis and Evolution of Chronic Kidney Disease: Untangling Ariadne's Thread

Amplification of oxidative stress is present since the early stages of chronic kidney disease (CKD), holding a key position in the pathogenesis of renal failure. Induction of renal pro-oxidant enzymes with excess generation of reactive oxygen species (ROS) and accumulation of dityrosine-containing protein products produced during oxidative stress (advanced oxidation protein products—AOPPs) have been directly linked to podocyte damage, proteinuria, and the development of focal segmental glomerulosclerosis (FSGS) as well as tubulointerstitial fibrosis. Vascular oxidative stress is considered to play a critical role in CKD progression, and ROS are potential mediators of the impaired myogenic responses of afferent renal arterioles in CKD and impaired renal autoregulation. Both oxidative stress and inflammation are CKD hallmarks. Oxidative stress promotes inflammation via formation of proinflammatory oxidized lipids or AOPPs, whereas activation of nuclear factor κB transcription factor in the pro-oxidant milieu promotes the expression of proinflammatory cytokines and recruitment of proinflammatory cells. Accumulating evidence implicates oxidative stress in various clinical models of CKD, including diabetic nephropathy, IgA nephropathy, polycystic kidney disease as well as the cardiorenal syndrome. The scope of this review is to tackle the issue of oxidative stress in CKD in a holistic manner so as to provide a future framework for potential interventions.

High glucose level and angiotensin II type 1 receptor stimulation synergistically amplify oxidative stress in renal mesangial cells

Oxidative stress in renal mesangial cell causes diabetic glomerular changes. High glucose levels and angiotensin II (Ang II) are known to stimulate superoxide production in renal mesangial cells. However, it has been unclear whether Ang II stimulation and pre-conditioning with high glucose affects the same pathway of superoxide production in renal mesangial cells or not. In this study, we examined the levels of oxidative stress under Ang II stimulation in renal mesangial cells preincubated for six hours at various glucose levels. Intracellular levels of reactive oxidative species (ROS) were measured using dihydroethidium or 5′,6′-chloromethyl- 2′,7′ dichlorodihydro-fluorescein diacetate, which facilitates the detection of intracellular ROS under real-time fluorescent microscope. Ang II-induced elevated intracellular ROS levels were detected only when the cells were pre-incubated with high levels of glucose (13.5 mM, 27.8 mM), but was not detected under normal glucose condition (5.5 mM). Production of Ang II-induced intracellular ROS was higher under pre-treatment with 27.8 mM glucose compared to pretreatment with 13.5 mM glucose level. This ROS production in mesangial cells was induced within several minutes of the initiation of Ang II stimulation under high glucose levels. The production of intracellular ROS was significantly reduced in the presence of angiotensin II type1-receptor (AT1R) antagonist, whereas it was augmented in the presence of angiotensin II type2-receptor antagonist. In conclusion, Ang II-induced oxidative stress was augmented by high glucose levels and ROS levels were further alleviated in the presence of AT1R antagonists.

New Understanding on the Role of Proteinuria in Progression of Chronic Kidney Disease

Proteinuria is identified as an important marker and risk factor of progression in chronic kidney disease. However, the precise mechanism of action in the progress of chronic kidney disease is still unclear. Mesangial toxicity from specific filtered compounds such as albumin-bound fatty acids and transferrin/iron, tubular overload and hyperplasia, and induction of proinflammatory molecules such as MCP-1 and inflammatory cytokines are some of the proposed mechanisms. Reversing intraglomerular hypertension with protein restriction or antihypertensive therapy may be beneficial both by diminishing hemodynamic injury to the glomeruli and by reducing protein filtration. Therefore, understanding proteinuria and its role in renal tubular interstitial inflammation and fibrosis is of great significance for the study of renal protective therapy, such as antiproteinuric treatments, and delaying the progression of chronic renal disease.

Alkalinization with potassium bicarbonate improves glutathione status and protein kinetics in young volunteers during 21-day bed rest

BACKGROUND & AIMS

Physical inactivity is associated with lean body mass wasting, oxidative stress and pro-inflammatory changes of cell membrane lipids. Alkalinization may potentially counteract these alterations. We evaluated the effects of potassium bicarbonate supplementation on protein kinetics, glutathione status and pro- and anti-inflammatory polyunsaturated fatty acids (PUFA) in erythrocyte membranes in humans, during experimental bed rest.

METHODS

Healthy, young, male volunteers were investigated at the end of two 21-day bed rest periods, one with, and the other without, daily potassium bicarbonate supplementation (90 mmol × d^-1), according to a cross-over design. Oxidative stress in erythrocytes was evaluated by determining the ratio between reduced (GSH) and oxidized glutathione (GSSG). Glutathione turnover and phenylalanine kinetics, a marker of whole body protein metabolism, were determined by stable isotope infusions. Erythrocyte membranes PUFA composition was analyzed by gas-chromatography.

RESULTS

At the end of the two study periods, urinary pH was 10 ± 3% greater in subjects receiving potassium bicarbonate supplementation (7.23 ± 0.15 vs. 6.68 ± 0.11, p < 0.001). Alkalinization increased total glutathione concentrations by 5 ± 2% (p < 0.05) and decreased its rate of clearance by 38 ± 13% (p < 0.05), without significantly changing GSH-to-GSSG ratio. After alkalinization, net protein balance in the postabsorptive state improved significantly by 17 ± 5% (p < 0.05) as well as the sum of n-3 PUFA and the n-3-to-n-6 PUFA ratio in erythrocyte membranes (p < 0.05).

CONCLUSIONS

Alkalinization during long-term inactivity is associated with improved glutathione status, anti-inflammatory lipid pattern in cell membranes and reduction in protein catabolism at whole body level. This study suggests that, in clinical conditions characterized by inactivity, oxidative stress and inflammation, alkalinization could be a useful adjuvant therapeutic strategy.

Sphingolipids and Redox Signaling in Renal Regulation and Chronic Kidney Diseases

Significance: Sphingolipids play critical roles in the membrane biology and intracellular signaling events that influence cellular behavior and function. Our review focuses on the cellular mechanisms and functional relevance of the cross talk between sphingolipids and redox signaling, which may be critically implicated in the pathogenesis of different renal diseases. Recent Advances: Reactive oxygen species (ROS) and sphingolipids can regulate cellular redox homeostasis through the regulation of NADPH oxidase, mitochondrial integrity, nitric oxide synthase (NOS), and antioxidant enzymes. Over the last two decades, there have been significant advancements in the field of sphingolipid research, and it was in 2010 for the first time that sphingolipid receptor modulator was exploited as a therapeutic in humans. The cross talk of sphingolipids with redox signaling pathways becomes an important mechanism in the development of many different diseases such as renal diseases. Critical Issues: The critical issues to be addressed in this review are how sphingolipids interact with the redox signaling pathway to regulate renal function and even result in chronic kidney diseases. Ceramide, sphingosine, and sphingosine-1-phosphate (S1P) as main signaling sphingolipids are discussed in more detail. Future Directions: Although sphingolipids and ROS may mediate or modulate cellular responses to physiological and pathological stimuli, more translational studies and mechanistic pursuit in a tissue- or cell-specific way are needed to enhance our understanding of this important topic and to develop effective therapeutic strategies to treat diseases associated with redox signaling and sphingolipid cross talk. Antioxid. Redox Signal. 28, 1008-1026.

Urinary pH is a predictor of diabetes in men; a population based large scale cohort study

AIMS

Previous cross-sectional studies revealed that patients with type 2 diabetes were associated with low urine pH. However, the association between urinary pH and incident type 2 diabetes is still unclear. Thus, we investigated the association between urinary pH and incident type 2 diabetes.

METHODS

This is a 5-year observational study of 3119men. We divided participants into four groups according to quartile of urinary pH. Multivariate logistic regression analysis was performed to calculate adjusted odds ratios (ORs) and 95% CIs for incident type 2 diabetes. We adjusted for age, body mass index, smoking, exercise, alcohol consumption, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol levels and impaired fasting glycaemia.

RESULTS

In the follow-up examination, 113men diagnosed as diabetes. The proportion of incident diabetes was 6.9% (case/N=22/318) in the lowest urinary pH group (urinary pH = 5.0), 3.4% (46/1366) in the second lowest group (urinary pH = 5.5), 3.5% (30/856) in the third lowest group (urinary pH = 6.0) and 2.6% (15/579) in the highest group (urinary pH≥6.5). The lowest urinary pH group was associated with the increased risk of incident diabetes compared to the other urinary pH groups (multivariate OR=1.91, 95% CI 1.05-3.36, p=0.033 for the second lowest, multivariate OR=1.99, 95% CI 1.05-3.71, p=0.036 for the third lowest and multivariate OR 2.69, 95% CI 1.30-5.72, p=0.008 for the highest urinary pH groups).

CONCLUSIONS

Low urine pH is an independent predictor of diabetes. We suggest that the urine pH can be an easy practical marker for diabetes.

Plasma levels of oxidative stress-responsive apoptosis inducing protein (ORAIP) in rats subjected to physicochemical oxidative stresses

Oxidative stress is known to play a pivotal role in the pathogenesis of various disorders including atherosclerosis, aging and especially ischaemia/reperfusion injury. It causes cell damage that leads to apoptosis. However, the precise mechanism has been uncertain. Recently, we identified an apoptosis-inducing humoral factor in a hypoxia/reoxygenated medium of cardiac myocytes. We named this novel post-translationally modified secreted form of eukaryotic translation initiation factor 5A (eIF5A) as oxidative stress-responsive apoptosis inducing protein (ORAIP). We developed a sandwich ELISA and confirmed that myocardial ischaemia/reperfusion markedly increased plasma levels of ORAIP. To investigate whether the role of ORAIP is common to various types of oxidative stress, we measured plasma ORAIP levels in rats subjected to three physicochemical models of oxidative stress including N2/O2 inhalation, cold/warm-stress (heat shock) and blood acidification. In all three models, plasma ORAIP levels significantly increased and reached a peak level at 10-30 min after stimulation, then decreased within 60 min. The (mean±S.E.M.) plasma ORAIP levels before and after (peak) stimulation were (16.4±9.6) and (55.2±34.2) ng/ml in N2/O2 inhalation, (14.1±12.4) and (34.3±14.6) ng/ml in cold/warm-stress, and (18.9±14.3) and (134.0±67.2) ng/ml in blood acidification study. These data strongly suggest that secretion of ORAIP in response to oxidative stress is universal mechanism and plays an essential role. ORAIP will be an important novel biomarker as well as a specific therapeutic target of these oxidative stress-induced cell injuries.

Antioxidant therapy improves non-thyroidal illness syndrome in uremic rats

BACKGROUND

The roles of antioxidant therapy on non-thyroidal illness syndrome (NTIS) in uremic rats is still unclear.

MATERIALS AND METHODS

Twenty-four Sprague-Dawley (SD) rats were randomly divided into blank, 5/6 nephrectomy (Nx), pyrrolidine dithiocarbamate (PDTC, 10 mg/100 g), sodium bicarbonate (SB, 0.1 g/100 g), N-acetylcysteine (NAC, 80 mg/100 g) and thyroid hormones (TH, levothyroxine 2 μg/100 g) groups. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), advanced oxidation protein products (AOPP), interleukin (IL)-1β, free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) were detected in the sixth week. The expressions of IL-1β and deiodinase type 1 (DIO1) were assessed by western blotting. The nuclear factor kappa B (NF-κB) inflammatory signal pathway was confirmed by electrophoretic mobility shift assay (EMSA).

RESULTS

Compared with 5/6 Nx group, PDTC and NAC significantly reduced the levels (p < 0.01, respectively) of serum MDA, AOPP, TSH, and elevated levels of serum SOD (p < 0.01, respectively) and FT3 (p = 0.016 and p < 0.01). Neither had significant effects on serum IL-1β content (p = 0.612 and p = 0.582). PDTC and NAC markedly decreased the protein expression of IL-1β (p < 0.01) and increased the protein expression of DIO1 (p < 0.01), respectively. Both had been considerably blunted NF-κB activity (p < 0.01).

CONCLUSIONS

In uremic rat model, PDTC and NAC can effectively improve oxidative stress level and NTIS. In terms of improving oxidative stress level, NAC is probably superior to PDTC.

Chelation of dietary iron prevents iron accumulation and macrophage infiltration in the type I diabetic kidney

We previously reported that the functional deletion of p21, a cyclin-dependent kinase inhibitor, in mice attenuated renal cell senescence in streptozotocin (STZ)-induced type 1 diabetic mice. In the present study, we investigated the effect of iron chelation on renal cell senescence and inflammation in the type 1 diabetic kidney. STZ-treated mice showed increase in iron accumulation, tubular cell senescence and macrophage infiltration at week 28 in the kidney. Administering deferasirox, which removes only dietary iron, significantly attenuated iron accumulation in proximal tubules and the number of infiltrating F4/80-positive cells without effecting blood glucose, hematocrit or hemoglobin levels. In contrast however, deferasirox did not influence renal cell senescence. The lack of p21 decreased the renal tubular iron accumulation and did not change tubular cell senescence. Interestingly, the STZ-treated animals showed an increase in p16, another cyclin-dependent kinase inhibitor. The results suggest that type 1 diabetes increases renal tubular iron accumulation and macrophage infiltration through a p21-dependent mechanism, and that the chelation of dietary iron attenuates these responses.

Lower urinary pH is useful for predicting renovascular disorder onset in patients with diabetes

BACKGROUND AND OBJECTIVES

A lower urinary pH (UpH) is closely linked to diabetes. However, its relation to diabetic renovascular damage is unclear. This study aimed to identify the relationship between UpH and the exacerbation of diabetic renovascular disorders.

METHODS

This is a 10-year observational study targeting 400 outpatients with diabetes who registered in 2003. We investigated the relationship between UpH in 2003 and renovascular damage from 2003 to 2013.

RESULTS

A total of 350 participants were eligible for the analysis. During their 10-year outpatient treatment, a decrease was seen in glycated hemoglobin levels, blood pressure, and estimated glomerular filtration rates (eGFRs), and an increase was seen in their urinary albumin-creatinine ratios (ACRs), uric acid (UA) levels, and intima-media thickness (IMT). UpH negatively correlated with urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), body mass index, UA, and ACR, and positively correlated with eGFR. The results of a multiple regression analysis showed that the independent risk factors for UpH were 8-OHdG, UA, eGFR, and ACR. UpH also negatively correlated with the percent change in IMT (%IMT), the percent change in pulse wave velocity (%PWV), and the change in log ACR (Δlog ACR), and positively correlated with the percent change in eGFR. A multiple regression analysis revealed that UpH was an independent risk factor for the %IMT, %PWV and Δlog ACR. Obese patients with low UpH values frequently suffered from sleep apnea syndrome.

CONCLUSIONS

These results suggest that UpH is a useful marker for predicting the onset of renovascular disorder in patients with diabetes.

Progression of renal injury toward interstitial inflammation and glomerular sclerosis is dependent on abnormal protein filtration

Chronic proteinuric renal diseases, independent from the type of the initial insult, have in common a loss of selectivity of the glomerular barrier to protein filtration. Glomerular sclerosis is the progressive lesion affecting the glomerular capillary wall, the primary site at which the protein filtration is abnormally enhanced by disease. Dysfunction of podocytes, that serve to maintain the intact barrier, is a central event in lesion development. However, glomerular injury is signalled to tubular and interstitial structures largely in advance of nephron destruction. Glomerular ultrafiltration of excessive amounts of plasma-derived proteins and associated factors incites tubulointerstitial damage and might amplify an inherent susceptibility of the kidney to become dysfunctional in several disease conditions. Thus, noxious substances in the proteinuric ultrafiltrate promote apoptotic responses and multiple changes in the phenotype of tubule cells with generation of inflammatory and fibrogenic mediators. The severity of tubular interstitial damage has long been recognized to be highly correlated to the degree of deterioration of renal failure even better than glomerular lesions. This review focuses on pathways of tubular injury and apoptosis that in turn promote nephron-by-nephron degeneration and interstitial fibrosis during proteinuria contributing to multifaceted processes of kidney scarring and function loss.

Remnant nephron physiology and the progression of chronic kidney disease

In chronic kidney disease, ongoing failure of individual nephrons leads to the progressive loss of renal function. This process results in part from a cellular and molecular response to injury that represents an attempt to maintain homeostasis but instead initiates a program that damages the nephron. As nephrons are lost, compensation by the remaining nephrons exacerbates glomerular pathophysiology. The delivery of excessive amounts of biologically active molecules to the distal nephron and tubulointerstitium generates inflammation and cellular dedifferentiation. Energy requirements of hyperfunctioning nephrons exceed the metabolic substrate available to the renal tubule, and inadequacy of the local vascular supply promotes hypoxia/ischemia and consequent acidosis and reactive oxygen species generation. In this way, mechanisms activated to maintain biological balance ultimately lead to demise of the nephron.

Relationship between estimated glomerular filtration rate, albuminuria, and oxidant status in the Japanese population

Background

In the general population, reported levels of oxidative stress and antioxidant potential seem to vary. The aim of this study was to investigate the levels of oxidant status markers in relation to estimated glomerular filtration rate (eGFR) and albuminuria in Japanese population.

Methods

Data were analyzed from 8335 individuals who underwent a general health screening test. For the estimation of albuminuria, urinary albumin-to-creatinine ratio (UAER) was calculated. Oxidant status was determined by assessing derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP).

Results

After adjusting for age, high blood pressure, depressor agent use, CRP, smoking status, multivariate logistic regression analysis showed that the lowest eGFR quartile was associated negatively with the top d-ROM quartile in men (odds ratio 0.78 [95% CI 0.62-0.98, P = 0.034]) and the highest UAER was associated with the top d-ROM in men (odds ratio 1.68) [95% CI 1.35-2.10, P < 0.001]. In addition, both the first eGFR quartile and the fourth UAER quartile showed significant positive association with low BAP levels in men, but not in women.

Conclusions

Among men who underwent general health screening, lower eGFR and increased albuminuria was negatively and positively, respectively, associated with higher oxidative stress levels, whereas both conditions were positively associated with lower antioxidant potential levels.

Alkalizer administration improves renal function in hyperuricemia associated with obesity

We evaluated the combination effect of the alkalizer citrate with the xanthine oxidase inhibitor allopurinol on renal function and uric acid in patients with hyperuricemia associated with obesity and/or metabolic syndrome (MetS), who were extracted from among the subjects enrolled in a prospective randomized controlled study aimed at assessing the efficacy of such a combination for improving renal function. We also conducted a post hoc analysis to examine influences on lipid profiles.

Patients who consented to participate in the study were randomly allocated to receive either allopurinol alone (monotherapy) or in combination with a citrate preparation (combination therapy). The analysis population consisted of 31 obese patients with a body mass index greater than 25 kg/m² (monotherapy, 15 patients; combination therapy, 16 patients). The creatinine clearance rate (Ccr), serum uric acid levels, and lipid profiles were measured before and at 12 weeks after the start of treatment.

In the combination therapy group, Ccr increased significantly and serum uric acid levels decreased significantly in obese patients, while Ccr tended to increase and serum uric acid levels decreased, though not significantly, in patients with MetS-related clinical parameters. Overall, blood triglyceride levels tended to improve in the combination therapy group as compared with the monotherapy group.

Tubulointerstitial injury and the progression of chronic kidney disease

In chronic kidney disease (CKD), once injury from any number of disease processes reaches a threshold, there follows an apparently irreversible course toward decline in kidney function. The tubulointerstitium may play a key role in this common progression pathway. Direct injury, high metabolic demands, or stimuli from various other forms of renal dysfunction activate tubular cells. These, in turn, interact with interstitial tissue elements and inflammatory cells, causing further pathologic changes in the renal parenchyma. The tissue response to these changes thus generates a feed-forward loop of kidney injury and progressive loss of function. This article reviews the mechanisms of this negative cycle mediating CKD.