The effect of uremic toxin cyanate (OCN–) on anaerobic sulfur metabolism and prooxidative processes in the rat kidney: a protective role of lipoate

Role of 3-Mercaptopyruvate Sulfurtransferase (3-MST) in Physiology and Disease

3-mercaptopyruvate sulfurtransferase (3-MST) plays the important role of producing hydrogen sulfide. Conserved from bacteria to Mammalia, this enzyme is localized in mitochondria as well as the cytoplasm. 3-MST mediates the reaction of 3-mercaptopyruvate with dihydrolipoic acid and thioredoxin to produce hydrogen sulfide. Hydrogen sulfide is also produced through cystathionine beta-synthase and cystathionine gamma-lyase, along with 3-MST, and is known to alleviate a variety of illnesses such as cancer, heart disease, and neurological conditions. The importance of cystathionine beta-synthase and cystathionine gamma-lyase in hydrogen sulfide biogenesis is well-described, but documentation of the 3-MST pathway is limited. This account compiles the current state of knowledge about the role of 3-MST in physiology and pathology. Attempts at targeting the 3-MST pathway for therapeutic benefit are discussed, highlighting the potential of 3-MST as a therapeutic target.

Cyanate improves insulin sensitivity and hepatic steatosis in normal and high fat-fed mice: Anorexic and antioxidative effects

Obesity is an important contributing factor to progression of chronic kidney disease. Cyanate, known as uremic toxin, is an electrophile produced spontaneously from urea or by myeloperoxidase-catalyzed oxidation of thiocyanate. Herein, we explored metabolic effects of cyanate in normal chow diet (NCD)- and high fat diet (HFD)-fed mice. Mice were treated with cyanate (1 mg/mL in drinking water) and fed NCD or HFD. Peritoneal glucose tolerance test (PGTT) and insulin tolerance test (ITT) were performed. Blood urea nitrogen (BUN) and creatinine concentrations were determined. Kidney and liver tissues were analyzed for reactive oxygen species (ROS) and lipid accumulations. Human albumin was carbamylated and evaluated for ROS scavenging activities. Contrary to our expectations, we found that cyanate treatment improved increased insulin sensitivity and alleviated hepatic steatosis in NCD- and HFD-fed mice. PGTT and ITT revealed faster and immediate glucose clearance in cyanate-treated NCD- and HFD-fed mice. Histological analysis of kidney and serum levels of BUN and creatinine showed no significant differences between cyanate-treated and control mice groups. Cyanate treatment reduced appetite and body weight in both NCD- and HFD-fed mice groups. Cyanate also decreased lipid peroxidation levels in the sera and the kidney, attenuated ROS levels in the kidney, which lead us to the findings that cAlb significantly reduced ROS levels compared to Alb in Caki-1 kidney and human umbilical vein endothelial cells. The results in this study may indicate that cyanate improves insulin sensitivity and hepatic steatosis possibly via exerting anorexic and antioxidative effects.

Protein carbamylation in kidney disease: pathogenesis and clinical implications

Carbamylation describes a nonenzymatic posttranslational protein modification mediated by cyanate, a dissociation product of urea. When kidney function declines and urea accumulates, the burden of carbamylation naturally increases. Free amino acids may protect proteins from carbamylation, and protein carbamylation has been shown to increase in uremic patients with amino acid deficiencies. Carbamylation reactions are capable of altering the structure and functional properties of certain proteins and have been implicated directly in the underlying mechanisms of various disease conditions. A broad range of studies has demonstrated how the irreversible binding of urea-derived cyanate to proteins in the human body causes inappropriate cellular responses leading to adverse outcomes such as accelerated atherosclerosis and inflammation. Given carbamylation's relationship to urea and the evidence that it contributes to disease pathogenesis, measurements of carbamylated proteins may serve as useful quantitative biomarkers of time-averaged urea concentrations while also offering risk assessment in patients with kidney disease. Moreover, the link between carbamylated proteins and disease pathophysiology creates an enticing therapeutic target for reducing the rate of carbamylation. This article reviews the biochemistry of the carbamylation reaction, its role in specific diseases, and the potential diagnostic and therapeutic implications of these findings based on recent advances.

The effect of lipoate on anaerobic cysteine metabolism in erythrocytes of patients treated with peritoneal dialysis

BACKGROUND

The studies aimed to evaluate the changes in cysteine sulfur metabolism in erythrocytes of end-stage renal failure (ESRF) patients treated with continuous ambulatory peritoneal dialysis (CAPD) caused by a one-month lipoate (LA) supplementation at a daily dose of 600 mg.

METHODS

The level of sulfane sulfur and activity of sulfurtransferases were determined in erythrocytes of CAPD patients and in the control group.

RESULTS

The sulfane sulfur level in erythrocytes of CAPD patients did not differ compared with healthy volunteers but LA supplementation increased the reactive sulfur concentration. LA elevated also cystathionase activity.

CONCLUSIONS

LA supplementation in ESRF patients treated with CAPD increases the sulfane sulfur level which indicates the augmentation of its antioxidant and regulatory properties.