Masaaki Nakayama

Impact of uremia, diabetes, and peritoneal dialysis itself on the pathogenesis of peritoneal sclerosis: a quantitative study of peritoneal membrane morphology.

BACKGROUND AND OBJECTIVESnPeritoneal interstitial fibrosis and hyalinizing vasculopathy were induced by peritoneal dialysis and other associated conditions (e.g., uremia). A quantitative method for peritoneal biopsy evaluation is required to investigate possible causative factors and severity of the peritoneal dialysis-related peritoneal alterations.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnPeritoneal biopsy specimens from 173 uremic (before peritoneal dialysis) and 80 peritoneal dialysis patients with or without impaired ultrafiltration capacity were evaluated by average peritoneal thickness of submesothelial compact zone measured at five randomly selected points of peritoneum and by lumen/vessel diameter ratio at postcapillary venule.nnnRESULTSnThe average peritoneal thickness was increased in uremic patients and progressively thickened as the duration of peritoneal dialysis prolonged. The lumen/vessel diameter ratio was lower in uremia than normal and progressively decreased as the duration of peritoneal dialysis prolonged. In pre-peritoneal dialysis peritoneum, patients with diabetes showed significant decrease in lumen/vessel diameter ratio compared with patients without diabetes. The average peritoneal thickness was significantly higher in patients with impaired ultrafiltration capacity than in patients with maintained ultrafiltration capacity; however, no significant difference was observed in the postcapillary venule thickness and lumen/vessel diameter ratio between the two groups.nnnCONCLUSIONSnThe average peritoneal thickness and lumen/vessel diameter ratio were useful morphologic parameters to quantify the severity of the peritoneal alterations in uremic and peritoneal dialysis patients. Uremia and diabetes had an impact on the pathogenesis of peritoneal sclerosis in pre-peritoneal dialysis peritoneum. Peritoneal dialysis treatment itself had a much stronger impact on the progression of peritoneal sclerosis.

Methylglyoxal contributes to the development of insulin resistance and salt sensitivity in Sprague-Dawley rats.

Objectives Methylglyoxal, a metabolite of the glycolysis pathway, may play an important role in the development of diabetes and hypertension, but the exact mechanism has not been fully elucidated. The present study was designed to investigate whether methylglyoxal could directly induce insulin resistance and salt sensitivity in Sprague–Dawley rats. Methods Rats were allocated to four groups: control (normal drinking water), 1% methylglyoxal in drinking water, 1% methylglyoxal plus N-acetyl cysteine (NAC) (800 mg/kg per day), a methylglyoxal scavenger, or TM2002 (100 mg/kg per day), an advanced glycation endproducts (AGEs) inhibitor. After 4-week treatment insulin resistance was evaluated by an euglycemic hyperinsulinemic glucose clamp technique. In another set of rats, either a high-salt diet (4%) alone, standard rat chow with 1% methylglyoxal in drinking water or high-salt diet plus methylglyoxal was given for 4 weeks. Immunohistochemistry was performed to measure nitrotyrosine and methylglyoxal-induced AGEs, Nϵ-carboxyethyl-lysine (CEL) in the kidney. Results Four-week treatment with NAC or TM2002 completely improved methylglyoxal-induced insulin resistance. Co-administration of methylglyoxal and high-salt diet significantly increased systolic blood pressure, urinary albumin excretion, urinary thiobarbituric acid-reactive substances excretion and the renal nitrotyrosine expression in the kidney (markers of oxidative stress) compared with methylglyoxal or high-salt diet alone. Renal CEL was significantly increased in methylglyoxal-treated rats compared with nonmethylglyoxal-treated rats. Conclusion These results indicate that methylglyoxal-induced insulin resistance and salt sensitivity at least in part by increasing oxidative stress and/or AGEs formation in Sprague–Dawley rats. The present study provides further evidence for methylglyoxal as one of the causative factors in the pathogenesis of insulin resistance and salt-sensitive hypertension.

Methylglyoxal Is a Predictor in Type 2 Diabetic Patients of Intima-Media Thickening and Elevation of Blood Pressure

We test whether plasma level of methylglyoxal (MG) is an independent risk factor predicting the progression of diabetic macroangiopathy or microangiopathy in type 2 diabetic patients. We measured in 50 type 2 diabetic patients plasma levels of MG and 3-deoxyglucosone (DG) using an electrospray ionization-liquid chromatography-mass spectrometry. We assessed the correlations between baseline levels of MG or DG and the percentage changes after 5 years of clinical parameters linked to diabetic macroangiopathy or microangiopathy, that is, intima-media thickness (IMT), systolic blood pressure (SBP), the amount of urinary albumin excretion (ACR), pulse wave velocity (PWV), and estimated glomerular filtration rate (eGFR). Multiple regression analysis was performed using the percentage changes in IMT, SBP, ACR, PWV, and eGFR over the 5-year period as the independent or objective variables and the values of MG, DG, glycohemoglobin A1c, body mass index, triglyceride, and diabetic duration at the baseline as the dependent variables. The values of IMT, PWV, SBP, and ACR all increase, but eGFR reduces with time during the 5-year period. Baseline level of MG correlates significantly with the percentage changes of IMT, SBP, ACR, PWV, and eGFR, whereas that of DG does only with ACR. A multiple regression analysis reveals that MG is an independent risk factor for the percentage changes of IMT, PWV, and SBP but not for those of ACR and eGFR. DG is an independent risk factor for the percentage change of ACR. MG is a predictor in type 2 diabetic patients of intima-media thickening, of increase of PWV, and of elevation of SBP.

A novel bioactive haemodialysis system using dissolved dihydrogen (H2) produced by water electrolysis: a clinical trial

BACKGROUNDnChronic inflammation in haemodialysis (HD) patients indicates a poor prognosis. However, therapeutic approaches are limited. Hydrogen gas (H(2)) ameliorates oxidative and inflammatory injuries to organs in animal models. We developed an HD system using a dialysis solution with high levels of dissolved H(2) and examined the clinical effects.nnnMETHODSnDialysis solution with H(2) (average of 48 ppb) was produced by mixing dialysate concentrates and reverse osmosis water containing dissolved H(2) generated by a water electrolysis technique. Subjects comprised 21 stable patients on standard HD who were switched to the test HD for 6 months at three sessions a week.nnnRESULTSnDuring the study period, no adverse clinical signs or symptoms were observed. A significant decrease in systolic blood pressure (SBP) before and after dialysis was observed during the study, and a significant number of patients achieved SBP <140 mmHg after HD (baseline, 21%; 6 months, 62%; P < 0.05). Changes in dialysis parameters were minimal, while significant decreases in levels of plasma monocyte chemoattractant protein 1 (P < 0.01) and myeloperoxidase (P < 0.05) were identified.nnnCONCLUSIONSnAdding H(2) to haemodialysis solutions ameliorated inflammatory reactions and improved BP control. This system could offer a novel therapeutic option for control of uraemia.

Different clinical outcomes for cardiovascular events and mortality in chronic kidney disease according to underlying renal disease: the Gonryo study

PurposeChronic kidney disease (CKD) can result from a wide variety of diseases, but whether clinical outcomes differ in the same CKD stages according to the underlying renal disease remains unclear. Clarification of this issue is important for stratifying risk of cardiovascular disease (CVD) and death in patients before dialysis.Patients and methodsThe study comprised 2,692 patients recruited from 11 outpatient nephrology clinics, classified by underlying disease of primary renal disease (PRD) (nxa0=xa01,306), hypertensive nephropathy (HN) (nxa0=xa0458), diabetic nephropathy (DN) (nxa0=xa0283), or other nephropathies (ON) (nxa0=xa0645). Risks of events such as ischemic heart disease, congestive heart failure, stroke, and all-cause mortality within 12xa0months were examined by logistic regression analysis in each group.ResultDuring the 12-months’ observation from recruitment, 200 cases were lost to follow-up, and 113 cases were introduced to chronic dialysis therapy. A total of 69 CVD events occurred (stroke in 27 cases), and 24 patients died. In total, increased odds ratios (OR) for the events by CKD stage (cf. CKD1xa0+xa02: unadjusted) were CKD3, 1.29 [95% confidence interval (CI), 0.70–2.17]; CKD4, 2.73 (1.55–4.83); and CKD5, 4.66 (2.63–8.23). Regarding events in respective groups, no significant differences were seen by CKD stage except for the group with HN, but significant differences were seen by underlying diseases (cf. PRD: adjusted for confounding factors, including estimated glomerular filtration rate): HN, 2.57 (1.09–6.04); DN, 12.21 (3.90–38.20); and ON, 4.14 (1.93–8.89).ConclusionRisk of CVD and mortality due to CKD needs to be stratified according to the underlying renal diseases.

Methylglyoxal augments intracellular oxidative stress in human aortic endothelial cells

Abstract Methylglyoxal (MGO) is a non-enzymatic metabolite in the glycolytic pathway and its concentration in blood and tissues is elevated in diabetes and renal failure. MGO induces tissue injuries via ROS; however, the mechanism remains to be clarified. The present study examined the harmful actions of MGO. Human aortic endothelial cells were assessed under real-time fluorescent microscopy with continuous superfusion. Increases in intracellular ROS were measured with fluorescent indicator, 5-(and-6)-chloromethyl-2’,7’-dichlorodihydrofluorescein diacetate acetyl ester (DCFH-DA). The addition of MGO rapidly increased the ROS in a dose-dependent manner. The increment of DCF was entirely abolished by pre-treatment with superoxide anion scavenger and membrane-permeable catalase, indicating that MGO induces superoxide production. The increment was completely inhibited by 2-thenoyltrifluoroacetone or carbonyl cyanide 3-chlorophenylhydrazone and partially inhibited by N-methyl-L-arginine. These data suggest that MGO stimulates superoxide production from mitochondria and partially stimulates nitric oxide synthase in human endothelial cells.

Association of Kidney Dysfunction with Silent Lacunar Infarcts and White Matter Hyperintensity in the General Population: The Ohasama Study

Background: No previous study has investigated the association of kidney dysfunction with silent lacunar infarcts and white-matter hyperintensity (WMH) independent of ambulatory blood pressure (BP). Methods: A cross-sectional study involving 1,008 participants (mean age 66 years) from a general population of Ohasama, Japan, was conducted. Calculated creatinine clearance (CCr) was estimated using the Cockcroft-Gault equation. In continuous and categorical analyses, the association between CCr and the prevalence of silent lacunar infarcts and WMH was investigated. Silent lacunar infarcts and WMH were detected on MRI. Multiple logistic regression analysis adjusted for 24-hour ambulatory BP, sex, age, body mass index, smoking and drinking status, antihypertensive medication, and histories of hypercholesterolemia, diabetes mellitus and heart disease was performed. Results: On univariate analysis, decreased CCr (continuous variable) and CCr <60 ml/min/1.73 m2 (categorical variable) were significantly associated with lacunar infarcts and WMH. After adjustment, each 1-standard-deviation decrease in CCr (odds ratio = 1.22; p = 0.036) and CCr <60 ml/min/1.73 m2 (odds ratio = 1.68; p = 0.007) was significantly associated with a high prevalence of lacunar infarcts. Even when 24-hour ambulatory BP was within the normal range (<130/80 mm Hg), CCr <60 ml/min/1.73 m2 was associated with a high prevalence of lacunar infarcts (odds ratio = 1.62; p = 0.047). CCr <60 ml/min/1.73 m2 and 24-hour ambulatory BP had additive effects on lacunar infarcts. After the same adjustment, the association between CCr and WMH was not significant. Conclusions: CCr is closely associated with lacunar infarcts, suggesting that kidney dysfunction in the elderly is an independent risk factor or predictor for silent lacunar infarcts.

Polymorphonuclear leukocyte injury by methylglyoxal and hydrogen peroxide: a possible pathological role for enhanced oxidative stress in chronic kidney disease

BACKGROUNDnAccelerated burst of polymorphonuclear leukocytes (PMNs) may be involved in the primary pathology of enhanced oxidative stress in patients with chronic kidney disease (CKD); however, the precise mechanism remains unknown. Methylglyoxal (MGO), an alpha-oxoaldehyde reportedly elevated in CKD, could induce apoptosis in several cell lines, and generates radicals by the reaction with hydrogen peroxide (H(2)O(2)). Thus, we tested if a high MGO of uraemic milieu could play a role in PMN injury by interaction with H(2)O(2).nnnMETHODnCellular viability of PMNs, isolated from healthy volunteers, was tested by ATP chemiluminescence levels under MGO and/or H(2)O(2), or 4-beta phorbol 12-beta-myristate 13-alpha-acetate (PMA). Superoxide anion (O(2)(-)) generation and apoptosis were measured by the reduction of ferricytochrome C and fluorocytometric analysis, respectively. Plasma MGO levels were measured by mass spectometry in 29 CKD patients.nnnRESULTSnAt low levels of MGO (1-10 microM) and H(2)O(2) (12.5 microM), no differences were found in cellular viability as compared to controls, whereas their combination significantly decreased PMN viability. PMA stimulation enhanced cellular injury of MGO by a function of MGO levels and preincubation with 5,5-dimethyl-1-pyrroline-N-oxide (free radical trap agent) attenuated it. MGO suppressed O(2)(-) generation by PMA, while it accelerated apoptotic ratios in PMNs. Significant increases of plasma MGO and C-reactive protein levels were found by a function of CKD stage, and clinical level of MGO could induce PMN injury in combination with H(2)O(2).nnnCONCLUSIONnThese results indicate the combinatory effect of MGO and H(2)O(2) on PMN oxidative injury, and this pathology may be linked to enhanced oxidative stress in CKD.

Characteristic effects of methylglyoxal and its degraded product formate on viability of human histiocytes: a possible detoxification pathway of methylglyoxal.

Methylglyoxal (MGO) is a toxic and highly reactive alpha-oxoaldehyde, elevated in the states of various diseases underlying enhanced oxidative stress. Furthermore, MGO has been reported to generate another aldehyde, formic acid (FA). In this sense, investigating the biological property of FA is crucially important. The present study examined the effects of MGO and FA on cell viability using the U937 human histiocytic cell line. FA showed a dose-dependent increase in cell viability at the concentrations of MGO in which cell viability decreased. The mechanism of the increase by FA involved the presence of endogenous hydrogen peroxide (H₂O₂) and tetrahydrofolate in the folate pathway, whereas that of the decrease in cell viability by MGO involved interaction with H₂O₂ and oxidative damage. These findings suggest that FA production by MGO degradation may play a role in attenuation of oxidative cellular injury caused by MGO. We hypothesize that FA generation pathway constitutes a detoxification system for MGO.