Specific binding of L-tryptophan to serum albumin and its function in vivo

Kynurenine Pathway in Chronic Kidney Disease: What’s Old, What’s New, and What’s Next?

Impaired kidney function and increased inflammatory process occurring in the course of Chronic Kidney Disease (CKD) contribute to the development of complex amino-acid alterations. The essential amino-acid tryptophan (TRP) undergoes extensive metabolism along several pathways, resulting in the production of many biologically active compounds. The results of many studies have shown that its metabolism via the kynurenine pathway is potently increased in the course of CKD. Metabolites of this pathway exhibit differential, sometimes opposite, roles in several biological processes. Their accumulation in the course of CKD may induce oxidative cell damage which stimulates inflammatory processes. They can also modulate the activity of numerous cellular signaling pathways through activation of the aryl hydrocarbon receptor, leading to the disruption of homeostasis of various organs. As a result, they can contribute to the development of the systemic disorders accompanying the course of chronic renal failure. This review gathers and systematizes reports concerning the knowledge connecting the kynurenine pathway metabolites to systemic disorders accompanying the development of CKD.

Differential impact of endurance, strength, or combined training on quality of life and plasma serotonin in healthy older women

Aging is associated with a progressive decline in physical and neurophysiological functions, and some studies suggest that cerebral serotonin is decreased in older adults. These factors contribute to reduced ability to perform daily activities, influencing quality of life (QoL). Regular physical activity has demonstrated important benefits in reversing ageing effects; however, little is known whether different training protocols might induce differential effects on QoL. The aim of this study was to verify the effects of different types of training on QoL and its relation with plasma serotonin in healthy older women. Forty-eight older women were randomly assigned in four groups: Strength Training (ST), Endurance Training (ET), Combined Training (CT), and Control Group (CG) which was instructed not to engage in any physical exercise during the study time. Participants underwent 12 weeks of training twice a week. Plasma serotonin and a scoring system questionnaire SF-36 for evaluation of QoL were assessed at baseline and after the completion of training protocols. When comparing pre- and post-training periods all trained groups showed improvement in QoL, but the CT improved more domains. Plasma serotonin was significantly lower in the ST and in the CT groups in comparison with controls after the 12-week training. Significant correlations of plasma serotonin with physical functioning, role-physical, general health, vitality, and mental health were observed. CT resulted in higher amelioration in QoL, in comparison with ET or ST only. All training protocols induced significant reductions in peripheral serotonin levels, which were negatively correlated with improvements in QoL.

Systemic metabolism of tryptophan and its catabolites, kynurenine and 3-HAA, in mice with inflammatory arthritis

Tryptophan is an essential amino acid. The liver is primary organ involved the oxidative catabolism of tryptophan. However, in the immune system, tryptophan and its catabolites, kynurenine and 3-hydroxyanthranilic acid (3-HAA), play an anti-inflammatory role. Rheumatoid arthritis (RA) is an autoimmune disease. Collagen induced arthritis (CIA) is an animal model of RA. Therefore, it was of interest to measure concentration of tryptophan, kynurenine and 3-HAA in mice with CIA. Concentration of tryptophan and 3-HAA was measured with HPLC methods. Concentration of kynurenine was measured with colorimetric test. mRNA expression for the kynurenine pathway genes was assessed using qRT-PCR. It has been found that in sera from diseased mice concentration of tryptophan was not changed. Concentration of kynurenine and 3-HAA was decreased. Moreover, in the livers from mice with CIA, concentration of tryptophan and kynurenine was decreased. These observations coincided with decreased mRNA expression for Ido2 and Afm and increased mRNA expression for Kynureninase in the liver. It has been also shown that in CIA the concentration of 3-HAA was increased in the kidneys.

Identification and characterization of oxidized human serum albumin

Human serum albumin (HSA) exists in both reduced and oxidized forms, and the percentage of oxidized albumin increases in several diseases. However, little is known regarding the pathophysiological significance of oxidation due to poor characterization of the precise structural and functional properties of oxidized HSA. Here, we characterize both the structural and functional differences between reduced and oxidized HSA. Using LC-ESI-TOFMS and FTMS analysis, we determined that the major structural change in oxidized HSA in healthy human plasma is a disulfide-bonded cysteine at the thiol of Cys34 of reduced HSA. Based on this structural information, we prepared standard samples of purified HSA, e.g. nonoxidized (intact purified HSA which mainly exists in reduced form), mildly oxidized and highly oxidized HSA. Using these standards, we demonstrated several differences in functional properties of HSA including protease susceptibility, ligand-binding affinity and antioxidant activity. From these observations, we conclude that an increased level of oxidized HSA may impair HSA function in a number of pathological conditions.

Potential role for nonesterified fatty acids in β-adrenoceptor-induced increases in brain tryptophan

We tested the hypothesis that beta2- and beta3-adrenergic receptor-mediated increases in brain tryptophan are due to the liberation of fatty acids, which in turn displace tryptophan from its albumin-binding site and thus facilitate its entry into the brain. Male CD-1 mice were injected with subtype-selective beta-adrenergic agonists 1h before brain samples were collected for analysis of tryptophan content by HPLC with electrochemical detection, and blood samples were collected for analysis of total and free tryptophan and nonesterified fatty acid (NEFA) concentrations. The beta2-selective agonist, clenbuterol (0.1 mg/kg), increased concentrations of tryptophan in all brain regions studied and decreased plasma total tryptophan, but had no effect on plasma free tryptophan or NEFAs. The beta3-selective agonists, BRL 37344 (0.2 mg/kg) or CL 316243 (0.01 mg/kg), increased brain tryptophan, plasma NEFAs and free tryptophan. Pretreatment with nicotinic acid (500 mg/kg), an inhibitor of lipolysis, almost completely prevented the increase in plasma free tryptophan and NEFAs, and attenuated the increase in brain tryptophan induced by CL 316243. These results suggest that beta2- and beta3-adrenergic agonists increase brain tryptophan by a mechanism other than the liberation of NEFAs. Nonetheless, beta3-adrenergic agonists appear to increase brain tryptophan by a mechanism that may depend partially on elevations of plasma NEFAs.

Contribution of serum albumin to the transport of orally administered L-tryptophan into liver of rats with L-tryptophan depletion

The role of serum albumin in the transport of orally administered L-tryptophan (Trp) into rat tissues was examined using analbuminemic and Sprague-Dawley (SD) rats with and without alpha-methyl-DL-tryptophan (AMT)-induced Trp depletion. Trp was orally administered to rats 16 h after AMT or 0.85% NaCl administration, when liver tryptophan 2,3-dioxygenase and protein synthetic activities in AMT-treated rats were similar to those of 0.85% NaCl-treated rats. After oral Trp administration, regardless of the presence or absence of Trp depletion, free serum Trp concentrations were similar in the analbuminemic and SD rats, while total serum Trp concentrations were lower in analbuminemic rats than in SD rats. Although liver, brain, and muscle Trp concentrations after oral Trp administration under Trp depletion were lower in analbuminemic rats than in SD rats, the ratio of the liver Trp concentration in analbuminemic rats to that in SD rats was smaller than that of the brain or muscle Trp concentration. These results suggest that variations in serum albumin levels could affect the transport of orally administered Trp into the liver of rats with Trp depletion.

Binding of (+)- and (-)-isomers and racemate of etomoxir to human serum albumin and effect of stearic acid and stanozolol

Binding of (+)- and (-)-isomers and the racemate of sodium 2[6-(4-chlorophenoxy)-hexyl]-oxiran-2-carboxylate dihydrat (etomoxir) to the human serum albumin (HSA) was studied by the gel filtration method. The experimental results are presented graphically using the method of Scatchard. Measurements revealed the following data on the binding: (a) for either of the isomers there are two independent and nonequivalent classes of binding sites on the HSA molecule; (b) the binding constants calculated for both isomers were of the same order of magnitude (K1/n approximately 20 x 10(5) L.mol-1 for the concentration range 3.48-4.0 x 10(-5) mol.L-1, and K2/n approximately 2 x 10(5) L.mol-1 for the concentration range 4.28-10 x 10(-5) mol.L-1, for the high and low affinity binding sites, respectively); (c) statistically significant difference (p < or = 0.05) between the low affinity binding constant estimated for the (+)-isomer K2 = 1.9 +/- 0.1 x 10(5) L.mol-1) compared with the constants evaluated for the (-)-isomer and racemic etomoxir (2.6 +/- 0.1 and 2.9 +/- 0.2 x 10(5) L.mol-1, respectively); and (d) both isomers are bound into a high extent to the HSA molecule (i.e., at a ligand concentration of 3.48 x 10(-5) mol.L-1, the percent of binding was approximately 95% for the compound tested. When plotting the percent binding (% Cb) against the total concentration (Ctot), a statistically significant difference (p < or = 0.05) was obtained between the slope of the straight line for the (+)-isomer and those for other two compounds.(ABSTRACT TRUNCATED AT 250 WORDS)