Erythrocytic glutathione and plasma cysteine status of human immunodeficient patients.

Both deficient and normal blood levels of glutathione (GSH) and cysteine (Cys) have been reported in HIV patients, a discrepancy that has been attributed to different methodologies. The goal of this study was to apply our analytical method to this problem. Blood samples from HIV patients and healthy subjects were collected, immediately stabilized, and quantified using high performance liquid chromatography with dual electrochemical detection. The results showed that the erythrocytic GSH levels were the same in healthy subjects and in HIV patients regardless of their CD4 lymphocyte level. Only those with the lowest CD4 level plus opportunistic infections had supranormal [corrected] GSH concentrations (P < 0.001). GSH plus glutathione disulfide (GSSG) levels also were normal in patients. However, the Cys contents were higher in patients than in controls (P < 0.05). These findings demonstrated that HIV patients have normal erythrocytic GSH concentrations and supranormal Cys levels.

Blood glutathione and cysteine concentrations in twin children.

Glutathione and cysteine are major antioxidants in blood that are associated with health and longevity. To ensure their measurement, careful attention to avoid auto-oxidation is necessary to stabilize the samples. Since no report of these compounds has been reported in children, our goal was to determine their levels of reduced and oxidized glutathione (GSH and GSSG) and cysteine (Cys and CSSC), To this end, 140 healthy children, ages 2 to 9 years from the Louisville Twin Study were studied. Blood samples were collected and analyzed for GSH, GSSG, Cys, and CSSC by our HPLC dual electrochemical method. The results showed that GSH and total GSH (GSH + GSSG) levels for monozygotic (MZ) twins were significantly higher (P < 0.001) than levels for dizygotic (DZ) twins. However, the opposite occurred for Cys and total Cys (Cys + CSSC) in that the levels were significantly higher for DZ twins than for MZ twins. (P < 0.005-0.013). In spite of this marked difference in zygosity, the within-pair correlations for twin pairs used for estimating heritability suggested that there was a major environmental influence for total GSH and total Cys. Finally. GSH levels were significantly lower for young (2-9 years) children than adults (P < 0.001).

Glutathione monoethyl ester protects against glutathione deficiencies due to aging and acetaminophen in mice.

Our previous results indicated that glutathione (GSH) and/or cysteine (Cys) deficiency occurs in many aging tissues and also after acetaminophen (APAP) administration. The aim of this study was to investigate whether GSH monoethyl ester (GSH-OEt) can correct these deficiencies. Mice of different ages (3-31 months) through the life span were sacrificed 2 h after i.p. injection of GSH-OEt (10 mmol/kg). In separate experiments, old mice (30-31 months) received the same dose of ester 30 min before the administration of APAP (375 mg/kg) or buthionine sulfoximine (BSO, 4 mmol/kg), an inhibitor of GSH synthesis. Liver and kidney samples were analyzed for GSH and Cys by HPLC. The hepatic GSH and renal cortical GSH and Cys concentrations were about 30% lower in old mice (30-31 months) compared to mature mice (12 months). GSH-OEt corrected these aging-related decreases. APAP decreased both hepatic and renal cortical GSH and Cys concentrations in old mice, but GSH-OEt prevented these decreases. GSH-OEt also prevented the BSO-induced decreases in hepatic and renal GSH concentrations. The results demonstrated that GSH-OEt protected against GSH deficiency due to biological aging as well as APAP-induced decreases in old mice.

Blood glutathione and cysteine changes in cardiovascular disease.

The need to investigate aminothiols such as glutathione (GSH), cysteine (Cys), and homocysteine (Hcy) in blood is stimulated by the current interest in hyperhomocysteinemia as a risk factor for atherosclerosis. Our current goal was to determine whether various cardiovascular (CV) diseases altered levels of GSH and Cys in blood and the relationships between these two thiols. Blood samples from 96 patients with atherosclerosis and other CV diseases were analyzed and compared with those from 33 control subjects. In CV patients, GSH levels were normal, but free plasma Cys was significantly higher (P < .0001). In patients with atherosclerosis, bound plasma Cys was 21% higher than that in control subjects (P < .0001), and in patients with other CV diseases it was 14% higher (P = .023). Also, in patients with CV diseases, correlations of free GSH with free Cys (P < .007) and total GSH and Cys with age (P < .04) differed from that in control subjects. There were no differences related to functional disability or duration of disease. A key finding was that these abnormal levels of plasma Cys occurred in both atherosclerotic and non-atherosclerotic CV diseases. These results indicate that high levels of oxidized and bound Cys in CV patients create an oxidative environment that may increase susceptibility to vascular damage.

Blood glutathione decreases in chronic diseases.

Previously a high blood glutathione level was correlated with long life span in the mouse and rat and in healthy elderly human beings. This raised the question of whether low glutathione levels occur in unhealthy subjects. To this end, 74 consecutive patients newly admitted to the hospital, with ages ranging from 21 to 89 years and diagnosed with chronic diseases, were studied along with 32 healthy control subjects. Blood samples were analyzed for reduced (GSH) and oxidized (GSSG) glutathione with a high-performance liquid chromatography-dual electrochemical method. The data were integrated with the clinical diagnoses and statistically analyzed. Marked total glutathione decreases from the control levels occurred in over 36% of the patients with chronic diseases including cancer and genitourinary, gastrointestinal, cardiovascular, and musculoskeletal diseases (P < .001). The deficit was due to low GSH concentrations and not to GSSG, which was the same as that in the control subjects. The conclusion is that a decrease in GSH is a risk factor for chronic diseases that may be used to monitor the severity and progress of the diseases. Future work is necessary to elucidate the mechanism of action.

The role of glutathione in p-aminophenol-induced nephrotoxicity in the mouse.

p-Aminophenol (PAP) produces nephrotoxicity in rats through a mechanism presumably involving oxidation and conjugation with glutathione (GSH). Recently it was found that PAP also causes nephrotoxicity in mice as evidenced by elevated blood urea nitrogen (BUN) and serum creatinine levels. The objective of this study was to further investigate the mechanism and elucidate the role of GSH in PAP-induced nephrotoxicity in the mouse. Male C57BL/6 mice injected i.p. with various doses of PAP were sacrificed at 12 hr for measurement of BUN and serum creatinine levels and determination of the extent of renal cortical nonprotein sulfhydryl (NPSH) and GSH depletion. PAP depleted renal cortical NPSH content in a dose- and time-dependent manner. Depletion of NPSH in mouse kidney did not occur at PAP doses below 600 mg/kg. Buthionine sulfoximine, an inhibitor of GSH synthesis, decreased nephrotoxicity. Ascorbate, a reducing agent, prevented PAP-induced nephrotoxicity and attenuated renal cortical NPSH depletion. However, acivicin and aminooxyacetic acid, inhibitors of gamma-glutamyltranspeptidase and beta-lyase, respectively, did not prevent toxicity in the mouse. Piperonyl butoxide, an inhibitor of cytochrome P-450 enzymes, enhanced nephrotoxicity and renal cysteine depletion but not GSH depletion. The results suggest that PAP-induced nephrotoxicity in the mouse may involve oxidation and formation of a GSH conjugate.

What can we conclude from the randomized controlled trials of fecal occult blood test screening?

The results of three published randomized controlled trials of fecal occult blood testing (FOBT) provide unequivocal proof of the principle that screening reduces mortality from colorectal cancer (CRC). However, several interesting questions remain in interpreting and applying the results of the clinical trials, including: how well does FOBT screening work (i.e. how much can CRC mortality be reduced), how does it work, when is it worthwhile and worthwhile doing, and how can technique be optimized? The answers to these questions have important practical and clinical implications.

Screening for colorectal cancer with the fecal occult blood test: a background paper. American College of Physicians.

PURPOSE: Screening for colorectal cancer with fecal occult blood tests or sigmoidoscopy can reduce mortality rates. If occult blood testing is done, clinicians must decide how to interpret the results and plan further management. If the results are positive, a decision must be made about evaluating the colon. This report provides information that can be used to perform fecal occult blood tests, interpret the results of those tests, and plan patient management. DATA SOURCES: The MEDLINE database was searched for data relevant to optimizing the technique of fecal occult blood testing. Studies were also identified from the bibliographies of published articles about test performance and the interpretation of test results, particularly sensitivity, specificity, and the probability of colorectal cancer after a positive test result. STUDY SELECTION AND DATA EXTRACTION: Studies were selected and data were extracted on the basis of the authors' combined judgment. DATA SYNTHESIS: When used for screening, fecal occult blood tests have positive results about 1% to 16% of the time, depending on such factors as the age of the person being tested, whether the sample is rehydrated, and whether the test is used for initial screening or for rescreening. When the colons of persons who have positive test results are evaluated, the rate of finding any colorectal cancer is about 2% to 17% and the rate for early colorectal cancer (Dukes stage A or B) is about 2% to 14%. CONCLUSIONS: These results suggest that, in general, persons who have positive results on a fecal occult blood test should have a full colonic examination. More research is needed to understand and improve the sensitivity and specificity of the fecal occult blood test.

Differential distribution of free and bound glutathione and cyst(e)ine in human blood.

The redox status of free and bound glutathione (GSH) and cyst(e)ine (Cys) is altered by oxidative stress, drugs, and disease. Most studies measure only their free forms and not the bound forms, which may have a crucial protective role. For this reason, we determined free and bound, reduced and oxidized GSH and Cys in whole blood, red cells, and plasma of human blood from healthy adults. Distinct compartments of GSH and Cys were found. In whole blood, > 99% GSH was in red cells, of which 16% was bound. GSH values were the same for red cells in whole blood or in cells isolated from the same samples. Only 0.5% of GSH was in plasma, all of which was bound. In contrast, 97% of Cys was in plasma and only 3% in red cells. This was a remarkable separation of these closely related metabolites in the same tissue. In plasma, 60% of Cys was bound. Also, strong correlations were shown of bound vs free Cys and also vs free plus bound Cys. The bound Cys was more constant and suggested that it is a metabolic reserve. Our findings demonstrate the occurrence of significant bound forms of GSH and Cys and have implications for future studies in disease and toxicology.

Glutathione disulfide variability in normal human blood.

A prevailing opinion is that glutathione disulfide (GSSG) levels in human blood are very low, but many studies have reported variable results. Therefore, our objective was to determine valid processing conditions for GSSG measurement and apply them to normal human blood samples. Reproducibility and stability of GSSG were demonstrated in acid extracts of a single sample of fresh whole blood by repetitive measurements during a 6-h period in which the %CVs were < 10. In contrast, in normal subjects tested repeatedly over several years, GSSG values ranging from < 2 to 166 nmol per 10(10) red blood cells were obtained and the overall %CV was 46. Lower GSSG values were obtained in hemolysates and ultrafiltrates. Thus, these results indicate that blood GSSG concentrations differ due to biological variation using optimal processing conditions.

Glutathione and morbidity in a community-based sample of elderly.

This study examined the association of blood glutathione level, a potential marker of physiological/functional aging, with a number of biomedical/psychological traits in a subgroup (N = 33) of a representative sample of community-based elderly. Higher glutathione levels were associated with fewer number of illnesses (p < 0.05), higher levels of self-rated health (p < 0.01), lower cholesterol (p < 0.05), lower body mass index, and lower blood pressures. Subjects with diagnoses of arthritis, diabetes, or heart disease (as assessed by physicians) had at least marginally significant lower glutathione levels than those who were disease free. Glutathione, together with age and a measure of suppressed anger, accounted for 39% of the variance of an index of morbidity. Glutathione, by itself, accounted for 24% of the variance. To our knowledge, this is the first evidence of an association of higher glutathione levels with higher levels of physical health in a sample of community-based elderly. Further studies in large samples are needed to investigate glutathione as a potential overall health risk factor for morbidity among the elderly.

Fecal occult blood screening for colorectal cancer. Is mortality reduced by chance selection for screening colonoscopy?

Annual fecal occult blood test (FOBT) screening using rehydrated Hemoccult slides has been reported in the Minnesota Colon Cancer Control Study to reduce colorectal cancer mortality by about 33%. However, some of the benefit of FOBT screening may come from "chance" selection of persons for colonoscopic examination because of the high positivity rate of FOBT (about 10%) that may occur for reasons other than a bleeding cancer or polyp. To determine how much this mechanism could account for the benefit of FOBT screening, we used a simple mathematical model to simulate the course of a cohort of screened persons, incorporating published data including those from the Minnesota study. The results suggest that one third to one half of the mortality reduction observed from FOBT screening in the Minnesota study may be attributable to chance selection for colonoscopy. We conclude that annual FOBT screening with rehydration is a haphazard method for selecting persons for colonoscopy.

Insulin-like growth factor-I comparisons in healthy twin children.

Insulin-like growth factor-I (IGF-I) levels in plasma were measured in healthy twin children. The within-pair correlation for 43 monozygotic pairs was r = 0.91 (P < or = 0.0001), an association significantly higher than that for same sex dizygotic pairs (r = 0.40; P < or = 0.06). The high correlation for monozygotic twins indicated a marked genetic influence on IGF-I levels. After correction for age and sex, the correlation between IGF-I level and height was r = 0.38 (P < or = 0.0001). These findings provide clear evidence that IGF-I levels correlate with height, a growth characteristic known to be genetically controlled.

Low blood glutathione levels in healthy aging adults.

The objective of this investigation was to test the hypothesis that blood glutathione levels are lower in aging human subjects as previously found in blood and tissues of standard rodent models of aging. Thus a study was conducted with 39 men and 130 women, 20 to 94 years old, who were selected by the criteria of being ambulatory, healthy, and free from diabetes mellitus, thyroid disease, anemias, and cancer. The reference group was comprised of the 20- to 39-year-old subjects, whose blood glutathione levels were 547 +/- 53.5 micrograms/10(10) erythrocytes (mean +/- SD) for 40 individuals and defined the reference range (95% confidence limits) of 440 to 654. Based on the 440 micrograms/10(10) erythrocyte cutoff, the incidence of low blood glutathione content in the older subjects increased significantly, particularly in the 60- to 79-year-old group. Their glutathione levels were 452 +/- 86.8 micrograms/10(10) erythrocytes, 17% lower than the reference group (p < 0.001). These findings demonstrate an increased incidence of low glutathione levels in apparently healthy elderly subjects, who thus may be at risk because of a decreased capacity to maintain many metabolic and detoxification reactions mediated by glutathione.