Acute changes in blood glucose do not alter blood glutathione synthesis in adolescents with poorly controlled type 1 diabetes mellitus

Depletion of blood glutathione (GSH), a key antioxidant, is associated with type 1 diabetes mellitus (T1D) and contributes to the pathophysiology of diabetes complications. The aim of the current study was to determine whether acute normalization of blood glucose would restore GSH kinetics in adolescents with poorly controlled T1D. Ten 16.9 ± 1.5-year-old (SE) adolescents who had had T1D for 8.5 ± 1.9 years and were free of complications but were in poor control (hemoglobin A(1c), 9.2% ± 0.5%) received two 5-hour intravenous infusions of L-[3,3-(2)H(2)]cysteine in the postabsorptive state on 2 separate days after blood glucose had been maintained overnight at 246 ± 24 mg/dL (hyperglycemia) or 118 ± 23 mg/dL (euglycemia) using intravenous insulin infusion. Blood GSH fractional synthesis rates were determined by mass spectrometry from (2)H(2)-cysteine incorporation into GSH. Neither blood GSH (551 ± 169 vs 541 ± 232 μmol/L, P = .629) nor GSH fractional synthesis rate (84% ± 30% vs 82% ± 33% d(-1), P = .965) was altered by the short-term change in glycemic control. This finding suggests that, in adolescents with poorly controlled T1D, either (a) blood glucose per se does not regulate GSH metabolism or (b) GSH may only respond to sustained, more chronic changes in blood glucose level.

Cysteine and obesity: consistency of the evidence across epidemiologic, animal and cellular studies

PURPOSE OF REVIEW

The concentrations of several plasma amino acids increase in obesity. Notably, plasma total concentrations of the sulphur amino acid cysteine (tCys) are linearly associated with fat mass in large population studies. Animal and cellular experiments support the concept that cysteine may be obesogenic. Here we review experimental and epidemiologic findings linking cysteine and related compounds with fat regulation and obesity.

RECENT FINDINGS

tCys, and to a lesser extent cystathionine, are the only plasma sulphur amino acids consistently associated with human obesity, whereas glutathione is inversely associated with BMI. Supplementing cyste(i)ne in rodents decreases energy expenditure and promotes adiposity, whereas defects of cysteine-synthesizing enzymes decrease body weight. In adipocytes, cysteine inhibits lipolysis and promotes lipogenesis via H2O2 production. Unlike most plasma amino acids, tCys levels do not decrease with gastric bypass-induced weight loss, further supporting the concept that elevated cysteine may be a cause, not a consequence of obesity. Although cysteine products (glutathione, taurine and H2S) are altered in obesity, they do not appear to explain cysteine's effects on body weight.

SUMMARY

Cellular, animal and epidemiologic data are consistent with the view that cysteine is obesogenic. Targeted research linking in-vitro and in-vivo findings is needed to elucidate mechanisms involved.

Cystathionine beta-synthase deficiency causes fat loss in mice

Cystathionine beta synthase (CBS) is the rate-limiting enzyme responsible for the de novo synthesis of cysteine. Patients with CBS deficiency have greatly elevated plasma total homocysteine (tHcy), decreased levels of plasma total cysteine (tCys), and often a marfanoid appearance characterized by thinness and low body-mass index (BMI). Here, we characterize the growth and body mass characteristics of CBS deficient TgI278T Cbs^−/− mice and show that these animals have significantly decreased fat mass and tCys compared to heterozygous sibling mice. The decrease in fat mass is accompanied by a 34% decrease in liver glutathione (GSH) along with a significant decrease in liver mRNA and protein for the critical fat biosynthesizing enzyme Stearoyl CoA desaturase-1 (Scd-1). Because plasma tCys has been positively associated with fat mass in humans, we tested the hypothesis that decreased tCys in TgI278T Cbs^−/− mice was the cause of the lean phenotype by placing the animals on water supplemented with N-acetyl cysteine (NAC) from birth to 240 days of age. Although NAC treatment in TgI278T Cbs^−/− mice caused significant increase in serum tCys and liver GSH, there was no increase in body fat content or in liver Scd-1 levels. Our results show that lack of CBS activity causes loss of fat mass, and that this effect appears to be independent of low serum tCys.

Clinical and nutritional benefits of cysteine-enriched protein supplements

PURPOSE OF REVIEW

To review recently published research into the use of dietary cysteine and/or its derivatives as functional food supplements that will enhance antioxidant status and improve outcome in certain diseases.

RECENT FINDINGS

L-cysteine is now widely recognized as a conditionally essential or (indispensible) sulphur amino acid. It plays a key role in the metabolic pathways involving methionine, taurine and glutathione (GSH), and may help fight chronic inflammation by boosting antioxidant status. In stressed and inflammatory states, sulphur amino acid metabolism adapts to meet the increased requirements for cysteine as a rate-limiting substrate for GSH. Critically ill patients receiving enteral or parenteral nutrition, enriched with cysteine, exhibit decreased cysteine catabolism and improved GSH synthesis. The naturally occurring cysteine-rich proteins, whey or keratin, have the potential to be manufactured into high quality, high cysteine-containing functional foods for clinical investigation.

SUMMARY

Cysteine-rich proteins, such as keratin, may have advantages over the simple amino acid or its derivatives, as nutraceuticals, to safely and beneficially improve antioxidant status in health and disease.

A critical life-supporting role for cystathionine γ-lyase in the absence of dietary cysteine supply

This study examined the important relationship between cystathionine γ-lyase (CSE) functionality and cysteine supply for normal growth and life span. Mice with a targeted deletion of the CSE gene (CSE-KO) were fed a cysteine-limited diet and their growth and survival patterns as well as levels of cysteine, homocysteine, glutathione, and hydrogen sulfide (H2S) were measured. CSE-KO mice fed a cysteine-limited diet exhibited growth retardation; decreased levels of cysteine, glutathione, and H2S; and increased plasma homocysteine level. However, histological examinations of liver did not reveal any abnormality and plasma levels of aspartate aminotransferase, alanine aminotransferase, and albumin were normal in these animals. No CSE-KO mice survived after 12 weeks of feeding with the cysteine-limited diet. Supplementation of H2S to the CSE-KO mice failed to reverse the aforementioned abnormalities. On the other hand, supplementation of cysteine in the drinking water of the CSE-KO mice significantly increased plasma cysteine and glutathione levels. This eventually led to an increase in body weight and rescued the animals from death. In conclusion, CSE is critical for cysteine biosynthesis through the transsulfuration pathway and the combination of CSE deficiency and lack of dietary cysteine supply would threaten life sustainability.

Assessment of cassava toxicity in patients with tropical chronic pancreatitis

BACKGROUND AND AIM

There have been conflicting reports on the role of cassava ingestion in tropical pancreatitis (TCP). In this study we aimed to estimate cyanogens detoxifying enzyme rhodanese, thiocyanate and sulfur containing amino acids in cassava consumer as well as cassava non-consumer TCP patients and healthy controls and compare the same.

METHODS

Eighty-six TCP patients and 90 healthy controls were recruited. Serum rhodanese, thiocyanate, plasma amino acids, urinary inorganic sulfate/creatinine were measured.

RESULTS

There was significant reduction in serum rhodanese activity in both cassava consumer- and non-consumer TCP patients as compared to controls but no significant difference between cassava consumer- and non-consumer TCP patients was observed. Serum thiocyanate was significantly lower in cassava consumer TCP patients as compared to cassava consumer controls but not significantly different from cassava non-consumer TCP patients. Plasma methionine, cysteine and urinary inorganic sulfate / creatinine ratio was significantly lower in both cassava consumer and non-consumer TCP patients as compared to controls but were comparable among cassava consumers and non-consumers.

CONCLUSIONS

Significant reduction in rhodanese activity with concomitant decrease in sulfur containing amino acids and antioxidants such as glutathione suggests that TCP patients are at higher risk of defective detoxification of cyanogens. However there was no difference between cassava consumers and non-consumers. Low levels of sulfur amino acids may contribute to the development of pancreatitis.

N-acetylcysteine in handgrip exercise: plasma thiols and adverse reactions

N-acetylcysteine (NAC) is a thiol donor with antioxidant properties that has potential use as an ergogenic aid. However, NAC is associated with adverse reactions that limit its use in humans.

PURPOSE

The authors evaluated NAC efficacy as a thiol donor before handgrip exercise, measuring changes in serum cysteine and glutathione status and recording adverse reactions in adult subjects across a range of doses.

METHODS

Healthy individuals ingested NAC capsules (9 ± 2 or 18 ± 4 mg/kg) or solution (0, 35, 70, or 140 mg/kg). Venous blood samples were collected and subjects answered a questionnaire about adverse reactions.

RESULTS

Low doses of NAC (capsules) did not affect plasma cysteine or glutathione or cause adverse reactions. Adverse reactions to NAC solution were predominantly mild and gastrointestinal (GI). Intensity of GI reactions to 140 mg/kg NAC was significantly higher than placebo (in a.u., 0.67 ± 0.16 vs. 0.07 ± 0.04; p < .05). Plasma cysteine concentration increased with NAC dose from 9.3 ± 0.7 μM (placebo) to 65.3 ± 6.7 μM (140 mg/kg); however, there was no difference (p > .05) in plasma cysteine for 70 mg/kg vs. 140 mg/kg. Similar increases were observed for the ratio of cysteine to total cysteine, which was directly related to handgrip exercise performance. Plasma glutathione was elevated and oxidized glutathione diminished (p < .05) with NAC 140 mg/kg vs. placebo.

CONCLUSION

NAC effects on plasma thiols are maximized by oral administration of 70 mg/kg, a dose that does not cause significant adverse reactions.

Total, free, and protein-bound thiols in plasma of peritoneal dialysis and predialysis patients

Thiol compounds such as glutathione, homocysteine, and cysteinyl-glycine are the natural reservoir of reductive capacity of the cells. Chronic renal failure is accompanied by disturbances in redox status of plasma thiols. The aim of the present study was to compare the changes in concentrations of different forms of thiols in plasma of terminal renal failure patients, nondialyzed and on peritoneal dialysis. Total concentrations of different redox forms of thiols were determined by high performance liquid chromatography. We observed that total concentration of glutathione in terminal renal failure patients decreased and total concentration of the remaining thiols in these patients significantly increased. Continuous ambulatory peritoneal dialysis had the following features in comparison with nondialyzed patients: (1) glutathione and cysteine concentration was restored and (2) free fraction of thiols rose, while protein-bound fraction dropped (except for homocysteine). Continuous ambulatory peritoneal dialysis corrects total concentration of glutathione and cysteine, in comparison with nondialyzed patients.

Cysteine/cystine redox signaling in cardiovascular disease

Extracellular thiol/disulfide redox environments are highly regulated in healthy individuals. The major thiol/disulfide redox couple in human plasma is cysteine (Cys) and its disulfide form, cystine (CySS). Oxidation of this redox couple, measured as a more positive steady-state redox potential (E(h)), is associated with risk factors for cardiovascular disease (CVD), including aging, smoking, obesity, and alcohol abuse. Rodent and vascular cell studies show that the extracellular redox state of Cys/CySS (E(h)CySS) can play a vital role in controlling CVD through proinflammatory signaling. This inflammatory signaling is regulated by cell-surface protein redox state and involves mitochondrial oxidation, nuclear factor-κB activation, and elevated expression of genes for monocyte recruitment to endothelial cells. Gene array and proteomics studies reveal the global nature of redox effects, and different cell types, e.g., endothelial cells, monocytes, fibroblasts, and epithelial cells, show cell-specific redox responses with different phenotypic traits, e.g., proliferation and apoptosis, which can contribute to CVD. The critical nature of the proinflammatory redox signaling and cell biology associated with E(h)CySS supports the use of plasma levels of Cys, CySS, and E(h)CySS as key indicators of vascular health. Plasma redox-state-based pharmacologic interventions to control or improve E(h)CySS may be effective in preventing CVD onset or progression.

[HPLC determination of plasma/serum homocysteine and cysteine with UV detection and solid-phase extraction on a polymeric sorbent]

Isocratic HPLC determination of plasma/serum homocysteine and cysteine with separation on reversed-phase column and UV detection at 330 nm is proposed. The mobile phase consist of acetonitrile - 0.05 M citrate-phosphate buffer with pH 2.4 - isopropanol (15:85:1, v/v/v). Full separation of cysteine, cysteamine (IS), glutathione and homocysteine was achieved within less than 10 minutes. Reduction of thiols from disulfides was performed by 1,4-dithioerithreitol, and derivatization by with Ellman's reagent [5'5-dithiobis-(2-nitrobenzoic acid)]. After that plasma/serum, containing derivatives of thiols, is cleared and concentrated on cartridge packed with 10 mg of hypercross-linked polystyrene (Purosep-200). Elution from cartridge is made with water-organic solvent (without evaporation and concentration, but without dilution), as well as waterless solvents (with evaporation and concentration). Simplicity, reproducibility in combination with high cleanliness of extracts and sufficient sensitivity (0.4 ng for homocysteine, 2 ng for glutathione and 0.2 ng for cysteine and cysteamine at a signal/noise ratio > 3), make this method suitable for routine clinical application.

A voltammetric sensor for the simultaneous determination of L-cysteine and tryptophan using a p-aminophenol-multiwall carbon nanotube paste electrode

Two amino acids, L-cysteine and tryptophan, could be simultaneously determined in an aqueous solution (pH 6.0) using a carbon nanotube paste electrode (CNPE) modified with p-aminophenol as a mediator. The results indicate that the electrode is efficient in terms of its electrocatalytic activity for the oxidation of L-cysteine, leading to an overpotential reduced by more than 550 mV. Using differential pulse voltammetry, we could measure L-cysteine and tryptophan in one mixture independently from each other by a potential difference of about 600 mV. Electrochemical techniques are used to determine the diffusion coefficients, kinetic parameters such as electron transfer coefficient, and the rates of electro-oxidation of L-cysteine at the surface of the p-aminophenol-modified CNPE. The peak current is found to depend linearly on L-cysteine and tryptophan concentrations within the ranges of 0.5 - 100 µmol L(-1) L-cysteine and 10.0 - 300 µmol L(-1) tryptophan. The detection limits for L-cysteine and tryptophan are found to be 0.3 and 5.7 µmol L(-1), respectively. The proposed method is also used for the determination of L-cysteine and tryptophan in urine, river water, blood plasma, and serum samples using standard addition methods.

Change in plasma and erythrocyte thiol levels in children undergoing fasting studies for investigation of hypoglycaemia

INTRODUCTION

It is unclear how repeated episodes of HG cause brain injury, but oxidative stress has been suggested to play a role. Non-protein thiols (glutathione, GSH, and cysteine, CYSH) form an important antioxidant defence, and their redox state is dependent on intracellular energy supplies and reducing power which are possibly compromised during low blood glucose concentrations.

AIM OF STUDY

To study thiol status in children undergoing investigations for hypoglycaemia . We hypothesised that thiol metabolism, dependent on intracellular energy supplies and reducing power, might deteriorate during hypoglycaemic episodes.

MATERIAL AND METHODS

Seventeen children with suspected hypoglycaemic episodes underwent a diagnostic fast. We measured plasma and erythrocyte GSH and CYSH as well as activities of enzymes related to glutathione metabolism during and after the fast.

RESULTS

A positive correlation between plasma glucose and reduced (free) cysteine was observed, but plasma GSH levels did not change significantly. Hypoglycaemia was associated with a rise in erythrocyte total cysteine without changes in erythrocyte GSH.

CONCLUSION

Low blood glucose concentration is associated with changes in thiol status, which compromise the protection against oxidative stress. This further supports the hypothesis of oxidative stress being associated with hypoglycaemia.

Oxidation of plasma cysteine/cystine and GSH/GSSG redox potentials by acetaminophen and sulfur amino acid insufficiency in humans

Variations in plasma sulfur amino acid (SAA) pools are associated with disease risks, but little information is available about the factors affecting plasma SAA pools. Drug metabolism by glutathione (GSH) and sulfate conjugation can, in principle, represent a quantitatively important burden on SAA supply. The present study was designed to determine whether therapeutic doses of acetaminophen (APAP) alter SAA metabolism in healthy human adults. A double-blind, crossover design incorporating four treatment periods with diets providing 100% of the recommended dietary allowance (RDA) for SAA without or with APAP (15 mg/kg) and 0% RDA for SAA without or with APAP, in randomized order. After a 3-day equilibration period, chemically defined diets with 100 or 0% RDA for SAA were given for 2 complete days. On day 3, APAP or placebo was given in two successive doses (6-h interval), and timed plasma samples were collected. With SAA intake at 100% RDA, APAP administration oxidized the plasma cysteine/cystine redox potential (E(h)CySS) but not the plasma GSH/GSSG redox potential (E(h)GSSG). The extent of oxidation caused by APAP was similar to that seen with 0% SAA and no APAP. However, APAP administration with 0% SAA did not cause further oxidation beyond APAP or 0% SAA alone. In contrast, an oxidation of the plasma E(h)GSSG was apparent for SAA insufficiency only with APAP. The results suggest a need to evaluate possible effects of APAP in association with SAA insufficiency as a contributing factor in disease risk.

An improved method for simultaneous analysis of aminothiols in human plasma by high-performance liquid chromatography with fluorescence detection

Altered levels of aminothiols in biological fluids are thought to be an important risk indicator for several diseases, and reliable methods for the accurate determination of aminothiols concentrations in plasma are thus required. In this paper ammonium 5-bromo-7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-BF) is proposed as a convenient fluorogenic derivatizating reagent for the determination of aminothiols (cysteine, cysteinylglycine, homocysteine and glutathione) by HPLC with fluorescence detection. The reactions of SBD-BF with aminothiols at room temperature are about three-times faster than those of ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (the most frequently employed reagent) at 60 degrees C. The derivatives of SBD-BF with cysteine, cysteinylglycine, homocysteine and glutathione are easily separated by HPLC and their calibration curves show excellent linearity over the range 0.05-20 micromol/L with excellent r(2) values for all analytes. SBD-BF reacts with thiols under mild conditions, i.e. at 25 degrees C over about 30 min, and is proposed as a suitable fluorogenic reagent for thiol derivatization to be introduced in analytical clinical chemistry. The detection limits of Cys, Cys-Gly, Hcy and GSH at a signal-to-noise ratio of 5 were 0.1 microM for Cys, 0.01 microM for Cys-Gly and Hcy, and 0.02 microM for GSH. Furthermore, validation parameters of the proposed method are quite satisfactory. As an application of this method the determination of thiol derivatives in human plasma was carried out on a number of samples.

Measuring the poise of thiol/disulfide couples in vivo

The reduction potentials (E(h)) for the redox couples GSH/GSSG and cysteine/cystine (Cys/CySS) in plasma are useful indicators of systemic oxidative stress and other medically relevant physiological states. This article describes a sensitive method for determining plasma levels of GSH, GSSG, Cys, and CySS used to calculate the in vivo E(h) values. The method uses iodoacetate to alkylate free thiols, derivatization with dansyl chloride to fluorescently tag amino groups, and HPLC and fluorescence to separate, detect, and quantify the molecules. Benefits of the method, such as sensitivity and dynamic range, are described, as are caveats, such as the importance of preventing red blood cell hemolysis and limitations in quantification of GSSG. General principles of redox chemistry and previous studies showing that the compounds are more oxidized than predicted from their standard reduction potentials are reviewed. The calculated in vivo E(h) is a convenient and informative way of summarizing the redox environment of plasma and is also useful for studies of cerebrospinal fluid, lymph, bronchoalveolar lavage fluid, human biopsies, and a broad range of in vitro cell culture conditions.

Alpha-lipoic acid induces elevated S-adenosylhomocysteine and depletes S-adenosylmethionine

Lipoic acid is a disulfhydryl-containing compound used in clinical medicine and in experimental models as an antioxidant. We developed a stable isotope dilution capillary gas chromatography/mass spectrometry assay for lipoic acid. We assayed a panel of the metabolites of transmethylation and transsulfuration 30 min after injecting 100 mg/kg lipoic acid in a rat model. Lipoic acid values rose 1000-fold in serum and 10-fold in liver. A methylated metabolite of lipoic acid was also detected but not quantitated. Lipoic acid injection caused a massive increase in serum S-adenosylhomocysteine and marked depletion of liver S-adenosylmethionine. Serum total cysteine was depleted but liver cysteine and glutathione were maintained. Serum total homocysteine doubled, with increases also in cystathionine, N,N-dimethylglycine, and alpha-aminobutyric acid. In contrast, after injection of 2-mercaptoethane sulfonic acid, serum total cysteine and homocysteine were markedly depleted and there were no effects on serum S-adenosylmethionine or S-adenosylhomocysteine. We conclude that large doses of lipoic acid displace sulfhydryls from binding sites, resulting in depletion of serum cysteine, but also pose a methylation burden with severe depletion of liver S-adenosylmethionine and massive release of S-adenosylhomocysteine. These changes may have previously unrecognized deleterious effects that should be investigated in both human disease and experimental models.

Factors that influence retinol-binding protein 4-transthyretin interaction are not altered in overweight subjects and overweight subjects with type 2 diabetes mellitus

Retinol-binding protein 4 (RBP4) is an adipokine bound in plasma to transthyretin (TTR), which prevents its glomerular filtration and subsequent catabolism in the kidney. Alterations of this interaction have been suggested to be implicated in the elevation of RBP4 that are thought to contribute to the development of insulin resistance associated with obesity and type 2 diabetes mellitus (T2DM). However, the factors linking RBP4 to TTR in humans are not clear. Therefore, this study evaluated parameters influencing the RBP4-TTR interaction and their relation to obesity and T2DM. The RBP4 and TTR levels were quantified in plasma of 16 lean controls, 28 overweight controls, and 14 overweight T2DM patients by enzyme-linked immunosorbent assay. Transthyretin isoforms involved in RBP4 binding were determined by linear matrix-assisted laser desorption/ionization-time of flight-mass spectrometry after RBP4 coimmunoprecipitation. Holo-RBP4 (retinol-bound) and apo-RBP4 (retinol-free) were assessed by immunoblotting using nondenaturating polyacrylamide gel electrophoresis. Plasma levels of both RBP4 and TTR did not differ among the groups of lean controls, overweight controls, and overweight T2DM subjects. Using RBP4 immunoprecipitation, 4 mass signals were observed for TTR representing native, S-cysteinylated, S-cysteinglycinylated, and S-glutathionylated TTR. No differences in peak intensity of TTR isoforms were observed among the groups. Moreover, no differences in the ratio of holo- and apo-RBP4 were evident. The results suggest that circulating RBP4 and TTR were not affected by human obesity or T2DM, which might be attributed to the absence of alterations of TTR isoforms and the ratio of holo- and apo-RBP4 that might modify the TTR-RBP4 interaction.

Homocysteine and cysteine concentrations are modified by recent exposure to environmental air pollution in São Paulo, Brazil

Millions of people worldwide are affected by anthropogenic air pollution derived from the combustion of fossil fuels. In this work, we tested the effects of fetal, lactation and post-weaning ambient air pollution exposure on total homocysteine (tHcy) concentrations and on a downstream pathway element, the plasma cysteine (Cys) concentration. Two similar exposure chambers (polluted and filtered chamber) were located near an area with heavy traffic in São Paulo, Brazil, and male Swiss mice were housed there from the pre-natal period until 3 months of age. Groups during fetal, lactation and adult periods of exposure were apportioned, and tHcy and Cys plasma concentrations were assessed when the animals were 3 months old. In our study, both the tHcy and Cys concentrations were decreased in groups that spent their final stage of life in polluted chambers, suggesting recent alterations in tHcy and Cys concentrations due to air pollution exposure. The possible relationship of these data with cardiovascular dysfunction is still a matter of controversy in animals; nevertheless, epigenetic mechanisms emerge as a possible issue to consider in the investigation of the link between air pollution and Hcy measurement.

Molybdenum cofactor deficiency in a Malaysian child

Molybdenum cofactor deficiency is a rare autosomal recessive disorder with devastating neurological manifestations, characterised by neonatal-onset encephalopathy mimicking hypoxic-ischaemic insult, intractable seizure, and feeding and respiratory difficulties. It is often fatal in the early life. We report an affected 8-year-old boy, who presented with severe neurological manifestations since birth, but without clinically-significant seizure. Molybdenum cofactor deficiency must be included in the differential diagnosis of patients presenting with unexplained encephalopathy in the newborn period, and whose neuroimaging findings are consistent with hypoxic ischaemic encephalopathy. The classic laboratory hallmark of this disorder is low serum uric acid, positive urine sulphite dipstick test, and elevated urinary S-sulphocysteine, hypoxanthine and xanthine.

Nutrition intervention: a strategy against systemic inflammatory syndrome

BACKGROUND

Sepsis and septic shock syndrome are the leading causes of death in critically ill patients. Lipopolysaccharide (LPS) released by the colonic microorganisms may translocate across a compromised lumen, leading to upregulated reactive oxidative stress, inflammation, and sepsis. The authors examined an enteral formula high in cysteine (antioxidant precursor), omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and prebiotic fructooligosaccharides (FOS) against systemic inflammatory syndrome.

METHODS

Rats were allocated to (1) standard soy-based diet high in cysteine and crude fiber and devoid of EPA-DHA (CHOW); (2) whey-peptide-based liquid diet high in cysteine, EPA-DHA, and FOS (CYSPUFA); or (3) casein-based liquid isonitrogenous diet, low in cysteine and devoid of EPA-DHA-FOS (CASN). Liquid diets provided 25% and CHOW, 23% of calories as protein. After 6 days on diets, rats received an intraperitoneal injection of LPS or saline. Animals gained weight on their respective diets and lost weight after LPS administration. The CYSPUFA group lost considerably less weight (vs CASN or CHOW, P < .05). Inflammatory cytokines significantly increased by 4 hours and subsided 18 hours after assault. The CASN group showed elevated liver enzyme alanine aminotransferase release from damaged hepatocytes and developed severe hepatic pathology with low hematocrit. The CHOW group developed more severe hepatic lesions compared with those on liquid diets. Concentration of liver enzyme and pathology were improved in rats receiving CYSPUFA.

CONCLUSIONS

Data indicate that CYSPUFA, a diet rich in EPA-DHA-FOS, protects against LPS-induced systemic inflammatory responses and warrants clinical studies in critically ill patients.

The association of plasma cysteine and gamma-glutamyltransferase with BMI and obesity

We recently reported a strong positive association of plasma total cysteine (tCys) with fat mass in over 5,000 subjects. As gamma-glutamyltransferase (GGT) enzyme increases cysteine availability by catalyzing glutathione breakdown and is positively associated with BMI and adiposity, we hypothesized that GGT might explain the association of tCys with adiposity. To study whether the associations of tCys and serum GGT with BMI and obesity were interrelated we conducted a cross-sectional study using data from 1,550 subjects recruited from nine European countries in the COMAC project. Multiple linear and logistic regression models and concentration-response curves were used. In age and sex-adjusted analyses, tCys showed strong positive associations with BMI (partial r = 0.19, P < 0.001), and obesity (odds ratio (OR) for 4th vs. 1st tCys quartile: 2.8; 95% confidence interval: 1.6-5.0, P < 0.001), both of which remained robust after adjustment for GGT and other metabolic and lifestyle confounders. Serum GGT was also a positive predictor of BMI (partial r = 0.17, P < 0.001) and obesity (OR for 4th vs. 1st GGT quartile: 4.8; 95% confidence interval: 2.5-9.2, P < 0.001), independent of tCys. However, the associations of GGT with BMI and obesity were weakened by adjustment for obesity-related factors such as serum lipids and blood pressure. These results indicate that tCys is a strong positive predictor of BMI and obesity, independent of GGT and other obesity-related factors. We also suggest that the association of serum GGT with BMI and obesity is unrelated to the role of GGT in cysteine turnover. The potential link between cysteine and fat metabolism should be further evaluated.