Substitution of high-dose sucrose with fructose in high-fat diets resulted in higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine and phenylalanine, and higher urine concentrations of arginine and citrulline.

High fructose intake has been shown to increase circulating alanine transaminase in humans, which could reflect damage to the liver by fructose but could also be linked to higher level of transamination of amino acids in liver. Therefore, we hypothesized that a diet with high content of fructose would affect the amino acid composition in rat plasma and urine differently from a diet with high sucrose content. Because high intake of sucrose and fructose is often accompanied with high intake of saturated fat in the Western-style diet, we wanted to compare the effects of high fructose/sucrose in diets with normal or high content of coconut oil on individual free amino acids plasma and urine. Male Wistar rats were fed diets with normal (10 wt%) or high (40 wt%) content of sucrose or fructose, with normal or high fat content (7 or 22 wt%) and 20 wt% protein (casein). Rats fed high-fructose high-fat diet had higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine, and phenylalanine and higher urine concentrations of arginine and citrulline when compared to rats fed high-sucrose high-fat diet. Substituting normal content of sucrose with fructose in the diets had little impact on amino acids in plasma and urine. Serum concentrations of alanine transaminase, aspartate transaminase, and creatinine, and urine cystatin C and T cell immunoglobulin mucin-1 concentrations were comparable between the groups and within normal ranges. To conclude, substituting high-dose sucrose with high-dose fructose in high-fat diets affected amino acid compositions in plasma and urine.

Use of Human Induced Pluripotent Stem Cells and Kidney Organoids To Develop a Cysteamine/mTOR Inhibition Combination Therapy for Cystinosis.

BACKGROUND: Mutations in CTNS-a gene encoding the cystine transporter cystinosin-cause the rare, autosomal, recessive, lysosomal-storage disease cystinosis. Research has also implicated cystinosin in modulating the mTORC1 pathway, which serves as a core regulator of cellular metabolism, proliferation, survival, and autophagy. In its severest form, cystinosis is characterized by cystine accumulation, renal proximal tubule dysfunction, and kidney failure. Because treatment with the cystine-depleting drug cysteamine only slows disease progression, there is an urgent need for better treatments. METHODS: To address a lack of good human-based cell culture models for studying cystinosis, we generated the first human induced pluripotent stem cell (iPSC) and kidney organoid models of the disorder. We used a variety of techniques to examine hallmarks of cystinosis-including cystine accumulation, lysosome size, the autophagy pathway, and apoptosis-and performed RNA sequencing on isogenic lines to identify differentially expressed genes in the cystinosis models compared with controls. RESULTS: Compared with controls, these cystinosis models exhibit elevated cystine levels, increased apoptosis, and defective basal autophagy. Cysteamine treatment ameliorates this phenotype, except for abnormalities in apoptosis and basal autophagy. We found that treatment with everolimus, an inhibitor of the mTOR pathway, reduces the number of large lysosomes, decreases apoptosis, and activates autophagy, but it does not rescue the defect in cystine loading. However, dual treatment of cystinotic iPSCs or kidney organoids with cysteamine and everolimus corrects all of the observed phenotypic abnormalities. CONCLUSIONS: These observations suggest that combination therapy with a cystine-depleting drug such as cysteamine and an mTOR pathway inhibitor such as everolimus has potential to improve treatment of cystinosis.

Oxidative stress in critically ill ventilated adults: effects of vitamin D3 and associations with alveolar macrophage function.

BACKGROUND/OBJECTIVES: Disruptions in redox balance lead to oxidative stress, a promoter of morbidity in critical illness. This study aimed to: (1) characterize the plasma and alveolar thiol/disulfide redox pools, (2) examine their associations with alveolar macrophage phagocytosis, and (3) determine the effect of high dose vitamin D3 on plasma thiol/disulfide redox. SUBJECTS/METHODS: Subjects were 30 critically ill, ventilated adults in a double-blind randomized trial of high-dose (250 000 or 500 000 IU) vitamin D3 or placebo. Baseline bronchoalveolar lavage fluid (BALF) samples were analyzed for determination of alveolar phagocytosis index (PI) and for concentrations of glutathione (GSH), glutathione disulfide (GSSG), cysteine (Cys), cystine (CySS), and their respective redox potentials (EhGSSG and EhCySS). Plasma redox outcomes were assessed at baseline and days 7 and 14. RESULTS: Baseline plasma Cys was inversely associated with alveolar PI (ρ = -0.69, P = 0.003), and EhCySS was positively associated with PI (ρ = 0.61, P = 0.01). Over time, among all subjects there was an increase in plasma GSH levels and a decrease in EhGSSG (P < 0.01 for both), with no difference by treatment group. Vitamin D3 decreased oxidized plasma GSSG to a more normal state (P for group x time = 0.009). CONCLUSIONS: Oxidative stress indicators were positively associated with alveolar macrophage phagocytic function in acutely ill ventilated adults. High-dose vitamin D3 decreased plasma GSSG concentrations, which suggests that vitamin D can possibly improve the oxidative stress environment.

Methionine and Choline Supply during the Periparturient Period Alter Plasma Amino Acid and One-Carbon Metabolism Profiles to Various Extents: Potential Role in Hepatic Metabolism and Antioxidant Status.

The objective of this study was to profile plasma amino acids (AA) and derivatives of their metabolism during the periparturient period in response to supplemental rumen-protected methionine (MET) or rumen-protected choline (CHOL). Forty cows were fed from -21 through 30 days around parturition in a 2 × 2 factorial design a diet containing MET or CHOL. MET supply led to greater circulating methionine and proportion of methionine in the essential AA pool, total AA, and total sulfur-containing compounds. Lysine in total AA also was greater in these cows, indicating a better overall AA profile. Sulfur-containing compounds (cystathionine, cystine, homocystine, and taurine) were greater in MET-fed cows, indicating an enriched sulfur-containing compound pool due to enhanced transsulfuration activity. Circulating essential AA and total AA concentrations were greater in cows supplied MET due to greater lysine, arginine, tryptophan, threonine, proline, asparagine, alanine, and citrulline. In contrast, CHOL supply had no effect on essential AA or total AA, and only tryptophan and cystine were greater. Plasma 3-methylhistidine concentration was lower in response to CHOL supply, suggesting less tissue protein mobilization in these cows. Overall, the data revealed that enhanced periparturient supply of MET has positive effects on plasma AA profiles and overall antioxidant status.

The short-term effects of antioxidant and zinc supplements on oxidative stress biomarker levels in plasma: a pilot investigation.

PURPOSE: To determine if short-term Age-Related Eye Disease Study (AREDS) antioxidant and zinc supplementation affects biomarkers of oxidative stress, possibly serving as a predictor of their efficacy. DESIGN: Prospective interventional case series. METHODS: Nineteen subjects, 12 with intermediate or advanced age-related macular degeneration (AMD) (AREDS categories 3 or 4) and 7 non-AMD controls, were admitted to the Vanderbilt General Clinical Research Center and placed on a controlled diet for 7 days. Antioxidant and zinc supplements were stopped 2 weeks prior to study enrollment. Dietary supplementation with 500 mg vitamin C, 400 IU vitamin E, 15 mg ß-carotene, 80 mg zinc oxide, and 2 mg cupric oxide per day was instituted on study day 2. Blood was drawn on study days 2 and 7, and plasma concentrations of cysteine (Cys), cystine (CySS), glutathione (GSH), isoprostane (IsoP), and isofuran (IsoF) were determined. RESULTS: Short-term AREDS supplementation significantly lowered mean plasma levels of CySS in participants on a regulated diet (P = .034). No significant differences were observed for Cys, GSH, IsoP, or IsoF. There were no significant differences between AMD patients and controls. CONCLUSIONS: This pilot interventional study shows that a 5-day course of antioxidant and zinc supplements can modify plasma levels of CySS, suggesting that this oxidative stress biomarker could help predict how likely an individual is to benefit from AREDS supplementation. Further, CySS may be useful for the evaluation of new AMD therapies, particularly those hypothesized to affect redox status.

Simultaneous analysis of mercury and selenium species including chiral forms of selenomethionine in human urine and serum by HPLC column-switching coupled to ICP-MS.

The simultaneous speciation of elements is of great concern, especially in the study of the interactions of species in living organisms. Here we report a method based on the coupling of HPLC-ICP-MS that is capable of separating and analyzing different selenium and mercury species (Se-methylselenocysteine, selenite, selenate, L-selenomethionine, D-selenomethionine, methylmercury and inorganic mercury). The proposed method uses two different mobile phases that are suitable for selenium and mercury speciation and leads to a successful determination of all the species in less than 27 min with good efficiency and resolution. The method was efficiently applied for simultaneous speciation of mercury and selenium in urine and in serum, the latter from umbilical cord samples. Selenocystine has been successfully identified in the former sample. Detection limits obtained were between 0.30 and 2.46 ng. Recovery studies of samples spiked with all species were performed to check the reliability of the method, and satisfactory recoveries (93-110%) were obtained in all cases. The relative standard deviations (RSDs) for species with ten replicate determinations of 80 µg L(-1) were between 4.5 and 9.2%. The proposed method offers a deeper insight into selenium and mercury interactions in the human body.

Antioxidant micronutrients and biomarkers of oxidative stress and inflammation in colorectal adenoma patients: results from a randomized, controlled clinical trial.

Previous epidemiologic observational and experimental studies investigated the potential of antioxidant micronutrients to modulate cancer risk, but these studies produced inconsistent results. In this pilot, randomized, double-blind, placebo-controlled clinical trial (n = 47), we assessed the effects of an antioxidant micronutrient combination (800 mg dl-alpha-tocopherol acetate, 24 mg beta-carotene, 1.0 g vitamin C, 200 microg l-selenomethionine, 7.2 mg riboflavin, 80 mg niacin, 60 mg zinc, 5 mg manganese) given daily over 4 months on oxidative and inflammatory biomarkers in patients with a history of sporadic colorectal adenoma. Plasma tumor necrosis factor-alpha (TNF-alpha), interleukin-6, and F2-isoprostane concentrations were measured using ELISAs, and cystine (CySS) was measured using high-performance liquid chromatography. Plasma TNF-alpha concentration decreased in the active treatment group by 37% relative to the placebo group (P = 0.002), and CySS decreased by 19% (P = 0.03); however, interleukin-6 and F2-isoprostane concentrations decreased in antioxidant-treated nonsmokers but increased in smokers, although these findings were not statistically significant. The decreases of TNF-alpha and CySS were more pronounced in nonsmokers. These data suggest that (a) an antioxidant micronutrient cocktail can modulate biomarkers of oxidative stress and inflammation in humans and (b) the effects of antioxidant micronutrient supplementation on biomarkers of inflammation and oxidative stress may differ according to smoking status.

High-dose cysteine administration does not increase synthesis of the antioxidant glutathione preterm infants.

OBJECTIVE: Our aim was to evaluate whether administration of additional cysteine is safe and stimulates glutathione synthesis in preterm infants in early life. METHODS: We conducted a prospective, randomized, clinical trial with infants with birth weights of <1500 g (N = 20). The infants were assigned randomly to receive either a standard dose (45 mg/kg per day) or a high dose (81 mg/kg per day) of cysteine. Intakes of other amino acids were similar, providing a total protein intake of 2.4 g/kg per day in both groups. We recorded base requirements in the first 6 days of life. On postnatal day 2, we conducted a stable isotope study to determine glutathione concentrations and synthesis rates in erythrocytes. RESULTS: Base requirements were higher in the high-dose cysteine group on days 3, 4, and 5. Despite an 80% increase in cysteine intake, plasma cystine concentrations did not increase. Glutathione concentrations and synthesis rates did not increase with additional cysteine administration. CONCLUSIONS: Administration of a high dose of cysteine (81 mg/kg per day) to preterm infants seems clinically safe but does not stimulate glutathione synthesis, compared with a lower dose (45 mg/kg per day). Further research is required to determine whether there is significant benefit associated with cysteine supplementation.

A novel HPLC-UV/nano-TiO2-chemiluminescence system for the determination of selenocystine and selenomethionine.

Active oxygen species from the photocatalytic reaction in aqueous solution react with luminol to emit strong chemiluminescence (CL), and this can be inhibited by the UV decomposed-products of selenocystine (SeCys) or selenomethionine (SeMet). Based on this phenomenon, a novel hyphenated technique, HPLC-UV/nano-TiO(2)-CL, was established for the determination of SeCys and SeMet. The effects of pH, the UV irradiation time, the TiO(2) coated on the inner surface of the reaction tubing, and the Co(2+) catalyst concentration on the CL intensity and/or chromatographic resolution were systematically investigated. Under these optimized conditions, the inhibited CL intensity has a good linear relationship with the concentration of SeCys in the range of 0.04-10.6 microg mL(-1) or SeMet in the range of 0.05-12.4 microg mL(-1), with a limit of detection (S/N=3) of 6.4 microg L(-1) for SeCys or 12 microg L(-1) for SeMet. As an example, the method was preliminarily applied to the determination of the selenoamino acids in garlic and rabbit serum, with a recovery of 88-104%.

Urinary felinine excretion in intact male cats is increased by dietary cystine.

Felinine is a branched-chain sulfur amino acid present in the urine of certain Felidae, including domestic cats. The objective of the present study was to determine if additional cystine and/or dietary N would increase felinine and N-acetylfelinine excretion by intact male cats fed a low-protein(LP) diet. Feeding five adult intact male cats an LP diet (18.8% of metabolisable energy (ME) as protein) v. a high-protein diet (38.6% of ME as protein) resulted in a trend (P=0.08) for decreased urinary felinine and no change in N-acetylfelinine excretion. In a 23 d study, when the LP diet was supplemented with L-cystine at 9.3 g/kg DM, urinary felinine:creatinine ratio showed a linear two-fold (121 %) increase (P<0.01) from 0.24 (SEM 0.05) to 0.53 (SEM 0.13) after 10 d. Subsequent feeding of the LP diet resulted in a decrease in felinine excretion to base levels. Plasma gamma-glutamyl felinylglycine concentrations were consistent with the excretion of felinine. Supplementation of the LP diet with L-cystine (9.3 g/kg DM),dispensable amino acids and arginine to a second group (n 5) also resulted in a significant (P<0.01) but smaller (+72 %) increase in the daily felinine:creatinine ratio (0.25 (SEM 0.04) to 0.43 (SEM 0.05)). The degree of felinine N-acetylation within groups was unaffected by dietary addition and withdrawal of amino acids. The results indicate that felinine synthesis is regulated by cystine availability, and that arginine may be physiologically important in decreasing felinine biosynthesis in intact male cats.

Effects of long-term zinc supplementation on plasma thiol metabolites and redox status in patients with age-related macular degeneration.

PURPOSE: To determine the effects of zinc supplementation on plasma thiol metabolites and their redox status in a cohort of patients with age-related macular degeneration (AMD). DESIGN: Randomized clinical trial that evaluated the effects of high doses of zinc and antioxidants on plasma biomarkers of oxidative stress. METHODS: This was an ancillary study of the Age-Related Eye Disease Study (AREDS). Subjects with AMD were randomized to one of four treatment groups: (1) antioxidants (vitamin C, 500 mg; vitamin E, 400 IU; and beta carotene, 15 mg), (2) zinc (80 mg zinc oxide, 2 mg cupric oxide), (3) antioxidants plus zinc, or (4) placebo. At 20 and 80 months after randomization, blood specimens were collected and analyzed for glutathione (GSH), oxidized glutathione (GSSG), cysteine (Cys), and cystine (CySS). RESULTS: Although zinc supplementation had no apparent effect on plasma thiol/disulfide redox status at the first blood draw, the group of patients receiving zinc supplementation at the second blood draw had significantly less CySS compared with those not receiving zinc (54.9 vs 64.1 microM; P = .01). There was a time-dependent oxidation of the plasma GHS pool and was not affected by zinc supplementation. CONCLUSIONS: Because increased CySS level is associated with aging, oxidative stress, and age-related diseases, the apparent prevention of increased CySS by zinc supplementation warrants additional investigation.

Enhancement of antigen-specific immunoglobulin G production in mice by co-administration of L-cystine and L-theanine.

Supplementation with both cystine and glutamic acid increases the synthesis of glutathione (GSH), which has a marked effect on immune cell function, as compared with supplementation with either amino acid alone in human macrophages in vitro. As dietary glutamic acid is metabolized during intestinal transport, oral administration of L-theanine (gamma-glutamylethylamide), which is metabolized to glutamic acid mainly in the liver, may act as a glutamic acid donor in vivo. The present study was performed to investigate the effects of oral administration of L-cystine and/or L-theanine on GSH levels and immune responses. Co-administration of L-cystine (200 mg/kg) and L-theanine (80 mg/kg) for 11 days before immunization significantly increased the levels of total GSH in the liver 6 hr after immunization as compared with the levels in control mice. To examine the effects of administration of L-cystine and/or L-theanine on the balance of T helper (Th) 1/Th2 cell responses, the serum ratios of the Th1 cytokine, interferon (IFN)-gamma, and the Th2 cytokine, interleukin IL-10, were investigated. At 24 hr after immunization, co-administration significantly increased the IL-10/IFN-gamma ratio compared with the ratios of the control and single-administration mice. Furthermore, co-administration before primary immunization significantly enhanced serum antigen-specific IgG levels. Taken together, these findings suggest that co-administration of L-cystine and L-theanine enhances antigen-specific IgG production partly through augmentation of GSH levels and Th2-mediated responses.

Thiol/disulfide redox status is oxidized in plasma and small intestinal and colonic mucosa of rats with inadequate sulfur amino acid intake.

Low molecular weight thiol/disulfide redox pools are dependent upon extracellular cysteine (Cys) availability. We determined whether dietary sulfur amino acid (SAA) deficiency induces oxidative stress in vivo, as determined by redox state of major thiol/disulfide couples in plasma [Cys/cystine (CySS)] and intestinal mucosa [glutathione (GSH)/glutathione disulfide (GSSG)]. Rats were fed isocaloric, isonitrogenous semipurified diets: either SAA-adequate (control), SAA-deficient, or SAA-supplemented, pair-fed to intake of the SAA-deficient group. Reference rats consumed standard rat food ad libitum. After 7 d, plasma and gut mucosal samples were analyzed for Cys, CySS, GSH and GSSG, and the redox potentials of Cys/CySS and GSH/GSSG were determined. Mean daily food intake in the pair-fed rats was similar (approximately one-half of reference-rat intake). Body weight decreased in all pair-fed groups, but rats fed the SAA-deficient diet lost significantly more body weight. Dietary SAA deficiency decreased GSH concentrations in both plasma and gut mucosa, increased plasma GSSG, and oxidized plasma and gut mucosal GSH/GSSG redox and plasma Cys/CySS redox. SAA supplementation resulted in a more reducing plasma Cys/CySS redox potential. Reference rats exhibited similar tissue and plasma GSH/GSSG redox as rats that ate semipurified SAA-adequate rat food, which provided similar net SAA intake. Our in vivo data show that inadequate dietary SAA intake oxidizes the thiol/disulfide redox status in rat-gut mucosa and plasma. Such oxidation of redox pools is associated with oxidative stress and the onset or progression of several pathological conditions. Thus, dietary SAA deficiency could contribute to the progression of disease by causing an oxidation of these components.

Antioxidant supplements prevent oxidation of cysteine/cystine redox in patients with age-related macular degeneration.

PURPOSE: Determine whether antioxidant supplements alter the plasma glutathione and/or cysteine redox potential in age-related macular degeneration (AMD) patients. DESIGN: This was an ancillary study to the Age-Related Eye Disease Study (AREDS), where subset of AREDS subjects at two sites were studied at two time points, an average of 1.7 and 6.7 years after enrollment. METHODS: Plasma glutathione (GSH), glutathione disulfide (GSSG), cysteine (Cys), and cystine (CySS) were measured by high-performance liquid chromatography, and redox potentials of GSH/GSSG (E(h) GSH) and Cys/CySS (E(h) Cys) were calculated. The means of the metabolites and redox potentials were compared by repeated-measures analysis of variance for subjects receiving antioxidants and those not receiving antioxidants. RESULTS: At the first blood draw, the means for the antioxidant group (n = 153) and no antioxidant group (n = 159) were not significantly different for any of the metabolites or redox potentials. At the second draw, the GSH parameters were not significantly different between the antioxidant (n = 37) and no antioxidant (n = 45) groups; however, mean Cys was significantly higher in the antioxidant group (9.5 vs 7.2 micromol/l, P = .008). Also, mean E(h) Cys was significantly more reduced in the antioxidant group (-74 vs -67.3 mV, P = .03). CONCLUSIONS: The AREDS antioxidant supplements reduced oxidation of E(h) Cys but had no effect on GSH. Because Cys is important for cell growth, apoptosis, and immune function, the beneficial effect of antioxidant supplementation on progression to advanced AMD may be partially explained by its effect on E(h) Cys and/or its effect on Cys availability.

Effect of thiol antioxidant on body fat and insulin reactivity.

Insulin signaling is enhanced by moderate concentrations of reactive oxygen species (ROS) and suppressed by persistent exposure to ROS. Diabetic patients show abnormally high ROS levels and a decrease in insulin reactivity which is ameliorated by antioxidants, such as N-acetylcysteine (NAC). A similar effect of NAC has not been reported for non-diabetic subjects. We now show that the insulin receptor (IR) kinase is inhibited in cell culture by physiologic concentrations of cysteine. In two double-blind trials involving a total of 140 non-diabetic subjects we found furthermore that NAC increased the HOMA-R index (derived from the fasting insulin and glucose concentrations) in smokers and obese patients, but not in nonobese non-smokers. In obese patients NAC also caused a decrease in glucose tolerance and body fat mass. Simultaneous treatment with creatine, a metabolite utilized by skeletal muscle and brain for the interconversion of ADP and ATP, reversed the NAC-mediated increase in HOMA-R index and the decrease in glucose tolerance without preventing the decrease in body fat. As the obese and hyperlipidemic patients had lower plasma thiol concentrations than the normolipidemic subjects, our results suggest that low thiol levels facilitate the development of obesity. Supplementation of thiols plus creatine may reduce body fat without compromising glucose tolerance.

Diet-induced hyperhomocysteinemia exacerbates neointima formation in rat carotid arteries after balloon injury.

BACKGROUND: Increasing evidence indicates that elevated plasma homocysteine levels are associated with an increased risk of atherosclerosis and endothelial dysfunction, although little specific information on the mechanisms responsible for the atherogenic effects of homocysteine or on the in vivo contribution made by hyperhomocysteinemia to atherosclerosis is currently available. Because homocysteine is known to exert a direct inhibitory effect on endothelial cell growth in vitro, we hypothesized that this effect contributes to the progression of atherosclerotic lesions initiated by endothelial damage caused by mechanical injury. METHODS AND RESULTS: We prepared diet-induced hyperhomocysteinemic rats in which neointima formation after balloon injury to the common carotid artery was assessed. Moderate hyperhomocysteinemia (plasma homocysteine levels 3- to 4-fold higher than control) significantly exacerbated neointima formation. Oral administration of folate, which had a homocysteine-lowering effect, diminished neointima formation induced by moderate hyperhomocysteinemia. Furthermore, the attenuation of reendothelialization was shown in diet-induced hyperhomocysteinemic rats with Evans blue staining. CONCLUSIONS: Diet-induced hyperhomocysteinemia, even mild to moderate, exacerbates neointima formation after denuding injury, making hyperhomocysteinemia a likely risk factor for postangioplasty restenosis. It may be mediated through an inhibitory effect of homocysteine on reendothelialization. Homocysteine lowering with folate supplementation can effectively ameliorate the detrimental effects of moderate hyperhomocysteinemia. Clinical trials would seem to be warranted.

A tale of two homocysteines--and two hemodialysis units.

Pharmacologic doses of folic acid are commonly used to reduce the hyperhomocysteinemia of end-stage renal disease (ESRD). Vitamin B12 acts at the same metabolic locus as folic acid, but information is lacking about the specific effects of high doses of this vitamin on homocysteine levels in renal failure. We therefore compared the plasma homocysteine concentrations of maintenance hemodialysis patients in two McGill University-affiliated urban tertiary-care medical centers that differed in the use of vitamin B12 and folic acid therapy. Patients in the first hemodialysis unit are routinely prescribed high-dose folic acid (HI-F, 6 mg/d), whereas those in the second unit receive high-dose vitamin B12 in the form of a monthly 1-mg intravenous injection, along with conventional oral folic acid (HI-B12, 1 mg/d). Predialysis homocysteine was 23.4 +/- 6.8 micromol/L (mean +/- SD) in the HI-F unit and 18.2 +/- 6.1 micromol/L in the HI-B12 unit (P < .002). Postdialysis homocysteine was 14.5 +/- 4.1 in the HI-F unit and 10.6 +/- 3.4 micromol/L in the HI-B12 unit (P = .0001). Multiple regression analysis indicated that high-dose parenteral vitamin B12 was associated with a lower homocysteine concentration even after controlling for the potential confounders of sex, serum urea, serum creatinine, urea reduction ratio, and plasma cysteine. Because this was a cross-sectional observational study, we cannot exclude the possibility that unidentified factors, rather than the different vitamin therapies, account for the different homocysteine levels in the two units. Careful prospective studies of the homocysteine-lowering effect of high-dose parenteral vitamin B12 in ESRD should be undertaken.

Nutritional therapy of chronic hepatitis by whey protein (non-heated).

In an open study the clinical efficacy of milk serum (whey) protein (Immunocal; cysteine content: 7.6-fold higher than that of casein) isolated from fresh milk and purified without heating was evaluated in 25 patients with chronic hepatitis B or C. Immunocal (12 g as protein) food (mousse) was given twice a day, in the morning and evening, for 12 weeks (test period). Casein (12 g as protein) food (mousse) was similarly given for two weeks prior to the start of the supplement with Immunocal food (induction period) and for four weeks after the end of the supplement with Immunocal food (follow-up period). Serum alanine aminotransferase (ALT) activity was reduced, and plasma glutathione (GSH) levels increased in six and five of eight patients with chronic hepatitis B, respectively, 12 weeks after the start of the supplement with Immunocal food. Serum lipid peroxide levels significantly decreased, and interleukin (IL)-2 levels and natural killer (NK) activity significantly increased. However, there were no significant Immunocal-related changes in 17 patients with chronic hepatitis C. These findings suggest that the long-term supplement with Immunocal alone may be effective for improving liver dysfunctions in patients with chronic hepatitis B.

[Protein status and antioxidant capability of residents in endemic and nonendemic areas of Keshan disease(KD)].

From a survey of residents in endemic and nonendemic areas of Keshan disease(KD), it was found that the plasma cystine, tryptophan and lysine as well as blood selenium content were lower, while the plasma lipid peroxide was higher in endemic areas than those in non-endemic areas. These results suggests that the selenium deficiency coexisting with cystine and tryptophan insufficiency decreases the antioxidant defense of the organism and may be one of the important factors for the development of KD. The role of sulfur-containing amino acid in antioxidant defense is discussed emphatically.

Role of cysteine and glutathione in HIV infection and other diseases associated with muscle wasting and immunological dysfunction.

The combination of abnormally low plasma cystine and glutamine levels, low natural killer (NK) cell activity, skeletal muscle wasting or muscle fatigue, and increased rates of urea production defines a complex of abnormalities that is tentatively called "low CG syndrome." These symptoms are found in patients with HIV infection, cancer, major injuries, sepsis, Crohn's disease, ulcerative colitis, chronic fatigue syndrome, and to some extent in overtrained athletes. The coincidence of these symptoms in diseases of different etiological origin suggests a causal relationship. The low NK cell activity in most cases is not life-threatening, but may be disastrous in HIV infection because it may compromise the initially stable balance between the immune system and virus, and trigger disease progression. This hypothesis is supported by the coincidence observed between the decrease of CD4+ T cells and a decrease in the plasma cystine level. In addition, recent studies revealed important clues about the role of cysteine and glutathione in the development of skeletal muscle wasting. Evidence suggests that 1) the cystine level is regulated primarily by the normal postabsorptive skeletal muscle protein catabolism, 2) the cystine level itself is a physiological regulator of nitrogen balance and body cell mass, 3) the cyst(e)ine-mediated regulatory circuit is compromised in various catabolic conditions, including old age, and 4) cysteine supplementation may be a useful therapy if combined with disease-specific treatments such as antiviral therapy in HIV infection.