Serum paraoxonase is known to prevent low-density lipoprotein oxidation and atherogenesis. Association of paraoxonase with the oxidative status and lipid profile in chronic renal failure (CRF) patients on conservative management and those on chronic maintenance hemodialysis was analyzed in the present study. Serum paraoxonase, protein thiols, lipid hydroperoxides, lipid profile, creatinine and albumin levels were estimated by spectrophotometric methods in CRF patients on conservative management, those on hemodialysis and in healthy controls. Total cholesterol, triglycerides, low-density lipoprotein cholesterol, lipid hydroperoxides and creatinine levels were higher and high-density lipoprotein cholesterol, protein thiols, albumin levels and paraoxonase activity were lower in patients than in healthy controls. Paraoxonase activity correlated positively with protein thiols and high-density lipoprotein cholesterol and negatively with low-density lipoprotein cholesterol and lipid hydroperoxides. In conclusion, paraoxonase activity is decreased in CRF patients particularly on chronic maintenance hemodialysis and correlates well with the oxidative stress markers.

Although considered useful in the diagnosis and prognosis of renal diseases, proteinuria can only be detected after significant renal paranchymal changes. There is considerable interest in the estimation of urinary peptides as an early marker of renal disease. In the current study, we have estimated urinary peptides in patients with different grades of proteinuria. Twenty-four hour urine samples were collected from 138 subjects and classified into three groups based on the urine protein excreted: group I (normoproteinuria, 0–150 mg/day, n = 37), group II (microproteinuria, 150–300 mg/day, n = 31), and group III (macroproteinuria, > 300 mg/day, n = 70). Urine proteins were determined using Bradford's method and urinary peptide levels were determined by subtracting Bradford's value from the Lowry value of the same sample. There was a significant decrease in the levels of urinary peptides in group III compared to group I (P < 0.01), however, there was no difference in peptides between groups I and II. The percentage of urinary peptides was decreased in both groups II and III compared to group I (P < 0.01), and there was a significant difference in % urinary peptide content in group II compared to group III (P < 0.01). On correlation, % urinary peptides correlated negatively with urinary proteins/g creatinine (r = - 0.782, P < 0.01) and positively with urinary peptides/g creatinine (r = 0.238, P < 0.01). Our data suggest that there is a marked decrease in urinary peptide levels with an increase in proteinuria. This may suggest impaired tubular protein reabsorption and degradation capacity of renal tubules.