Changes in serum levels of creatol and methylguanidine in renal injury induced by lipid peroxide produced by vitamin E deficiency and GSH depletion in rats

Uremic toxins in acute kidney injury

Acute kidney injury (AKI) is a serious and frequent condition which may fully resolve but is associated with markedly increased mortality. Mortality in AKI is caused by nonrenal, distant organ failure. Renal recovery from AKI is often not achieved on account of new injuries in the repair phase. Uremic toxins may be the missing link between AKI and nonrenal organ failure, tubular and endothelial injury. Compared with chronic kidney disease (CKD), research of uremic toxins in AKI is in its infancy. This review presents the current knowledge on uremic toxins in AKI which is predominately derived from experimental studies. Most uremic toxins investigated have previously been identified in CKD. The review focuses on those uremic toxins with biologic effect on the respective nonrenal organs failing in AKI and on the renal tubule and the endothelium. These uremic toxins may insofar be specific mediators of pathophysiological processes in AKI.

First indications demonstrating the preventive effects of NZ-419, a novel intrinsic antioxidant, on the initiation and/or progression of chronic renal failure in rats

The concentration of NZ-419 (5-hydroxy-1-methylimidazolidine-2,4-dione), an intrinsic antioxidant, has been shown to increase in the sera of animals and patients with chronic renal failure (CRF). This is the first report that orally administered exogenous NZ-419 prevents the initiation and/or progression of CRF in rats using an adenine-loaded model. After 24 d of adenine loading, there was a ca. 90% decrease in creatinine clearance (C(Cr)) in the control rats. Treatment with NZ-419 from the beginning significantly inhibited the decrease in C(Cr) and also the increase in serum creatinine (sCr). Bio-markers for in vivo hydroxyl radicals, the serum methylguanidine (sMG) level, and sMG/sCr molar ratio, not only in serum but also in the urine, kidney, liver, and muscle indicated that NZ-419 inhibited the increase in oxidative stress induced by CRF in rats. An increase of guanidinosuccinic acid, an another bio-marker of oxidative stress, was also inhibited with NZ-419.

Urinary Excretion of Creatol, an In Vivo Biomarker of Hydroxyl Radical, in Patients with Chronic Renal Failure

Creatol (CTL) is a hydroxyl radical adduct of creatinine (Cr). The serum methylguanidine (MG) level and the MG/Cr molar ratio are reported to be biomarkers for oxidative stress. The aim of this study was to examine whether urinary excretion of CTL, another oxidative stress-related marker, is increased in patients with chronic renal failure (CRF). One hundred twenty-four non-dialyzed patients with chronic renal failure (serum Cr level, 1.3-10.0 mg/dL) were recruited from our hospitals. Urine and serum levels of CTL and MG were determined by high-performance liquid chromatography with the use of 9, 10- phenanthrenequinone as a fluorogenic reagent. The CTL/Cr and (CTL+MG)/Cr molar ratios in spot urine samples were also compared with those in 24-h urine samples. The urinary CTL/Cr and (CTL+MG)/Cr molar ratios increased with decreases in Cr clearance in patients with CRF. Correlations between serum and spot urine (CTL+MG)/Cr and between serum and spot urine CTL/Cr were quite similar to those in 24-h urine samples. CTL/Cr and (CTL+MG)/Cr molar ratios in both 24-h urine and spot urine samples appear to be useful indices of the severity of CRF.

Creatine and creatinine metabolism

The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis and degradation, species and tissue distribution of the enzymes and metabolites involved, and of the inherent implications for physiology and human pathology. Very recently, a series of new discoveries have been made that are bound to have distinguished implications for bioenergetics, physiology, human pathology, and clinical diagnosis and that suggest that deregulation of the creatine kinase (CK) system is associated with a variety of diseases. Disturbances of the CK system have been observed in muscle, brain, cardiac, and renal diseases as well as in cancer. On the other hand, Cr and Cr analogs such as cyclocreatine were found to have antitumor, antiviral, and antidiabetic effects and to protect tissues from hypoxic, ischemic, neurodegenerative, or muscle damage. Oral Cr ingestion is used in sports as an ergogenic aid, and some data suggest that Cr and creatinine may be precursors of food mutagens and uremic toxins. These findings are discussed in depth, the interrelationships are outlined, and all is put into a broader context to provide a more detailed understanding of the biological functions of Cr and of the CK system.

N epsilon-(carboxymethyl)lysine in blood from maintenance hemodialysis patients may contribute to dialysis-related amyloidosis

BACKGROUND

Recent studies demonstrated not only that advanced glycation end product could be found in amyloid tissue from patient with dialysis related amyloidosis, but also that amyloid beta2-microglobulin was modified with N(epsilon)-(carboxymethyl)lysine (CML). We wanted to determine if CML could be a biomarker in these patients.

METHODS

To raise polyclonal anti-carboxymethyllysine antibody, human serum albumin was carboxymethylated by glyoxylic acid and was immunized to rabbits as antigen. Carboxymethyllysine-hemoglobin (CML-Hb) levels were measured by the dot blotting method using this antibody.

RESULTS

The levels of CML-Hb were 6.68 +/- 3.10 nmol CML/mg Hb in nondiabetic hemodialysis patients (N = 70), 6.39 +/- 3.43 nmol CML/mg Hb in diabetic hemodialysis patient (N = 21), and 3.13 +/- 0.88 nmol CML/mg Hb in 47 healthy volunteers. For clinical signs of dialysis-related amyloidosis, 70 nondiabetic hemodialysis patients were scored according Gejyo's criteria. The CML-Hb levels in patients with a high amyloid score as well as a low amyloid score were significantly higher than in patients with negative amyloid score (8.89 +/- 3.53 nmol CMLmg Hb, 7.28 +/- 2.32 nmol CML/mg Hb vs. 5.11 +/- 2.09 nmol CML/mg Hb, P < 0.001, P < 0.05). Furthermore, the CML-Hb levels correlated significantly with serum values of the methylguanidine over creatinine ratio and hyaluronate.

CONCLUSIONS

We suggest that CML-Hb is increased in blood from patients on maintenance hemodialysis and is thus a potential biomarker of oxidative damage in these patients. Moreover, CML-modification of protein may play a pathogenic role in the development of dialysis related amyloidosis.

Regenerative response in acute renal failure due to vitamin E deficiency and glutathione depletion in rats

In this study, we investigated some factors contributing to renal regeneration after acute renal failure (ARF) induced by vitamin E (VE) deficiency and glutathione (GSH) depletion. Acute renal failure was induced by feeding rats a vitamin E-deficient diet for 6 weeks and then injecting buthionine sulfoximine (BSO), a glutathione-depleting agent. The level of hepatocyte growth factor (HGF), a renotropic factor for regeneration in the kidney, showed a transient increase at 5 hr after the BSO treatment. Subsequently, renal ornithine decarboxylase (ODC) activity, a marker of G1 phase, and labeling index (LI) of proliferating cell nuclear antigen (PCNA), a marker of DNA synthesis (S phase), reached peaks at 10 and 53 hr after the injection, respectively. Thus, it appears that the increase in ornithine decarboxylase activity and subsequent elevation in proliferating cell nuclear antigen labeling index following the increase in the hepatocyte growth factor level in the kidneys are closely related to the renal regenerative response after acute renal failure.

Vitamin E may slow kidney failure owing to oxidative stress

Progression to kidney failure in a number of major renal diseases is now thought to be significantly worsened by oxidative stress at the biochemical level. Evidence is accumulating that the rate of deterioration could, in many cases, be slowed down to a more acceptable level by the simple expedient of dietary supplementation with the antioxidant, vitamin E. Evidence for the potential use of vitamin E as an adjunctive therapy to help prolong kidney function in conditions that are accelerated by oxidative stress is discussed.