Use of ornithine alpha-ketoglutarate in clinical nutrition of elderly patients.
Explore the source record for details and available documents.
Aged↗
Biomedical subjects
C Aussel
Publications and source records attributed to C Aussel.
Inhibition of phosphatidylserine synthesis in Jurkat T cells by hydrogen peroxide.
Incubation of Jurkat cells in the presence of H2O2 either directly added to the culture medium or generated with glucose oxidase, menadione or the couple xanthine/xanthine oxidase induced a marked decrease of phosphatidylserine synthesis in the absence of changes in the synthesis of phosphatidylcholine and phosphatidylethanolamine. Concentration dependent response curves indicated that H2O2 induced inhibition of phosphatidylserine synthesis with an IC(50)=5 microM while both induction of tyrosine phosphorylation of proteins and Ca(2+) signals were obtained with an EC(50)=300 microM. The tyrosine kinase and Ca(2+) independent mechanism was confirmed by comparing the H2O2-induced and the CD3-induced inhibition of phosphatidylserine synthesis using several Jurkat clones differing in the expression of cell surface receptors such as CD3/TCR and CD45 and protein tyrosine kinase such as p72syk, ZAP-70 and p56lck. While CD3-induced inhibition of phosphatidylserine synthesis necessitates protein tyrosine phosphorylation and Ca(2+) signals, H2O2 provoked its effect in all the clones studied independently of the presence or absence of the proteins previously shown to be key elements in T cell signal transduction. Conversely, the antioxidant molecule, butylated hydroxanisole, generates an increased PtdSer synthesis, suggesting that the synthesis of this phospholipid is regulated by the redox status of the cells.
Antioxidants↗
Role of two conserved cytoplasmic threonine residues (T410 and T412) in CD5 signaling.
CD5 is a transmembrane coreceptor that modulates activation and differentiation signals mediated by the Ag-specific receptor present on both T and B1a lymphocytes. CD5 lacks intrinsic catalytic activity, and its immunomodulatory properties result from intracellular interactions mediated by the CD5 cytoplasmic tail. The nature of these interactions is currently a matter of investigation. Here, we present a selective mutagenesis analysis of two conserved threonine residues (T410 and T412) located at the membrane-proximal cytoplasmic region of CD5. These residues are contained within consensus phosphorylation motifs for protein kinase C and are shown here to be critical for in vivo protein kinase C-mediated phosphorylation of CD5. Functional studies revealed that the integrity of T410 and T412 is also critical for CD5-mediated phosphatidylcholine-specific phospholipase C (PC-PLC) activation and phorbol ester-mediated inhibition of Ab-induced internalization of CD5. These results strongly argue in favor of a role for T410 and T412 in the signaling mediated by CD5.
Amino Acid Substitution↗
Regulation of phosphatidylserine exposure at the cell surface by the serine--base exchange enzyme system during CD95-induced apoptosis.
Early in the apoptotic process, CD95 induces a translocation of phosphatidylserine (PtdSer) from the inner to the outer leaflet of the cellular plasma membrane. In mammalian cells, PtdSer is only synthesized through a calcium-dependent exchange of the polar head group of pre-existing phospholipids, either phosphatidylcholine or phosphatidylethanolamine, by a serine. Using a pharmacological approach, we examined the influence of PtdSer synthesis on CD95-induced PtdSer exposure at the surface of Jurkat cells. We found that CD3/TCR triggering or thapsigargin treatment of Jurkat cells was accompanied both by a decreased PtdSer synthesis and by a strong reduction of CD95-induced PtdSer at the cell surface, as monitored by fluorescence-activated cell sorting (FACS) analysis of annexin V-fluorescein isothiocyanate (FITC)-labeled cells. PtdSer synthesis through the serine-base exchange enzyme system thus appeared as one of the mechanisms implicated in the recently discovered CD3/TCR-induced down-regulation of CD95-induced apoptosis. Conversely, increasing the activity of the serine-base exchange enzyme system with different drugs, either the K+ channel blocker quinine, the cationic amphiphil stearylamine, or three different calmodulin antagonists, chlorpromazine, trifluoperazine, and N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W7), resulted in an increased appearance of PtdSer at the surface of CD95-treated cells. Both PtdSer synthesis and CD95-induced annexin V-FITC reactivity were abrogated in ATP-depleted cells. Also, modifying the membrane potential with valinomycin (hyperpolarization) or either gramicidin or KCl (depolarization) demonstrated a strong relationship between PtdSer synthesis and annexin V-FITC reactivity in CD95-treated cells. Together, our results indicate that CD95-induced exposure of PtdSer at the cell surface could be regulated by the activity of the serine-base exchange enzyme system.
Adenosine Triphosphate↗
System A neutral amino acid transporter regulation by interleukin-1beta in human osteoarthritic synovial cells: evidence for involvement of prostaglandin E(2) as a second messenger.
We studied the long-terms effects of interleukin-1beta (IL-1beta; 3 to 6 h) on alpha-(methylamino) isobutyric acid (MeAIB), a nonmetabolizable amino acid transported by system A. We found that IL-1beta induced a large decrease in MeAIB uptake by human osteoarthritic synovial cells and a concomitant increase in prostaglandin E(2) (PGE(2)) synthesis. Therefore, we investigated whether PGE(2) acts as a mediator for the long-term action of IL-1beta. We found that exogenous PGE(2) inhibited MeAIB uptake, and that AH6809, a PGE(2) receptor antagonist, inhibited IL-1beta-mediated MeAIB uptake. To identify the enzymes involved in the IL-1beta-mediated synthesis of PGE(2) that inhibits MeAIB uptake, we studied the expression of secreted (s) and cytosolic (c) phospholipase A(2) (PLA(2)). Because both were expressed, we selected a broad spectrum of inhibitors to determine which of the two PLA(2)s was involved. We used AACOCF3, a cPLA(2) inhibitor, and dithiothreitol (DTT) and bromophenacyl bromide (BPB), which are sPLA(2) inhibitors. Our results suggest that the PLA(2) involved in the IL-1beta-mediated synthesis of PGE(2) was sPLA(2). We also showed the expression of cyclooxygenase (COX)-2 and its partial involvement using a potent selective COX-2 inhibitor, L-745337. These findings provide insight into the mechanisms underlying the IL-1beta-mediated regulation of transport system A. The Il-1beta-induced inhibition of MeAIB uptake in human osteoarthritic synovial cells thus seems to be essentially mediated by PGE(2) production via the activation of sPLA(2) and the partial activation of COX-2.
Amino Acid Transport Systems↗
Inhibition of phosphatidylserine synthesis during Jurkat T cell activation. The phosphatase inhibitor, sodium ortho-vanadate bypasses the CD3/T cell receptor-induced second messenger signaling pathway.
Sodium ortho-vanadate (Na3VO4), an inhibitor of protein tyrosine phosphatase, induces a rapid (15 min) and strong inhibition of phosphatidylserine synthesis with an IC50 = 100 microM. The mode of action of Na3VO4 was compared to that of CD3 mAbs. It was found that Na3VO4 bypasses the major CD3-induced T cell activation signals including protein tyrosine phosphorylation, p56lck activation and the generation of second messengers including inositol phosphates and its subsequent Ca2+ mobilization as well as diacylglycerol production. These facts were confirmed by using a panel of Jurkat clones that differs by the expression of either tyrosine kinases involved in the CD3-induced T cell activation pathway such as p56lck, p72syk and ZAP-70 or some cell surface receptors such as the CD3/TCR complex or the CD45 phosphatase.
Antibodies, Monoclonal↗
Branched-chain keto-acids and pyruvate in blood: measurement by HPLC with fluorimetric detection and changes in older subjects.
BACKGROUND: Measurement of keto-acids is important in various clinical situations. The aim of the present work was to develop a rapid HPLC method for the determination of keto-acids in human serum and to assess the concentrations of these acids in young adults and institutionalized elderly adults. This method was applied to the determination of blood keto-acid concentrations of young adults and institutionalized elderly people, divided into age groups METHODS: Four keto-acids (alpha-ketoisocaproate, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, and pyruvate) were derivatized with o-phenylenediamine to give fluorescent derivatives. After the sample preparation step (75 min to prepare 20 samples), the derivatives were separated chromatographically on a reversed-phase column using a binary gradient. RESULTS: The fluorometric detection of the four keto-acids was rapid, <12 min. The method is repeatable and reproducible: the CVs were <6% and <11%, respectively, for each of the keto-acids. We found no significant difference between males and females. Concentrations of the branched-chain keto-acids decreased after age 60 years, especially alpha-ketoisocaproate, which decreased approximately 40%. CONCLUSIONS: The proposed method allows rapid and reliable measurement of keto-acids. The data demonstrate that changes in branched-chain keto-acids concentrations in serum occur with age.
Adult↗
Prostaglandin B(2) delivers a co-stimulatory signal leading to T cell activation.
Most of the data accumulated to date on the immunoregulatory effects of prostaglandins (PG) on T cell activation stem from the archetypal inhibitory effect of PGE(2). In this study we provide instead, the first evidence that exogenous PGB(2), a catabolic metabolite of PGE(2), synergizes with signals delivered by T cell receptor (TCR) engagement to induce interleukin-2 (IL-2) production and IL-2 receptor (IL-2R) alpha-expression in Jurkat cells. Accordingly, PGB(2) enhances the proliferation of anti-CD3-activated peripheral blood lymphocytes (PBL). In terms of cellular signaling, we present evidence that PGB(2) activates tyrosine kinase activities and efficiently increases c-fos mRNA expression and nuclear factor-kappa B (NF-kappa B) translocation to the nucleus. Owing to these features, PGB(2) appears as a new lipid mediator capable of delivering an ancillary signal leading to T lymphocyte activation.
Antigens, CD↗
Regulation of phosphatidylserine synthesis in Jurkat T cell clones: caffeine bypasses CD3/TCR-induced protein tyrosine kinases and calcium signals.
Phosphatidylserine synthesis as measured by the incorporation of [(3)H]serine into phosphatidylserine (PtdSer) through the serine-base exchange enzyme system (serine-BEES) is markedly inhibited in Jurkat cells treated with caffeine. The caffeine-induced inhibition was compared to that observed in cells treated with either CD3 mAb or thapsigargin. While CD3- and thapsigargin-induced inhibition was related to the release of Ca(2+) from the endoplasmic reticulum (ER), a process that deprives the serine-BEES of its major cofactor, caffeine modified PtdSer synthesis in the absence of decreased Ca(2+) content of ER. Using Jurkat clones differing by the expression of cell surface markers or protein tyrosine kinases implicated in the CD3/TCR signal transmission pathway, we have shown that CD3 mAb-induced inhibition of PtdSer synthesis necessitates the expression of both the CD3/TCR and the protein tyrosine phosphatase CD45 at the cell surface as well as the presence of p56(lck) and ZAP-70 protein tyrosine kinases. By contrast, thapsigargin, a blocker of the Ca(2+)-ATPase of the ER, known for its Ca(2+) releasing properties, inhibited PtdSer synthesis in all the Jurkat clones tested, indicating that this compound bypasses the CD3/TCR-induced signals. Despite its lack of effect on Ca(2+) release from ER and on protein tyrosine phosphorylations, caffeine inhibited PtdSer synthesis in all the Jurkat clones. The use of several cAMP-inducing drugs and of others xanthine derivatives indicated that caffeine modify PtdSer synthesis either by a direct action on the serine-BEES or by a modification of the structure of the phospholipids used as substrate by the enzyme.
Antibodies, Monoclonal↗
A Na(+)-dependent system A and ASC-independent amino acid transport system stimulated by glucagon in rat hepatocytes.
The effects of glucagon on amino acid transport in rat hepatocytes are not fully understood. We examined the effect of this hormone on alanine, serine and cysteine preferring system (system ASC)-mediated amino acid transport in rat hepatocyte monolayers using 2-aminoisobutyric acid (AIB) and l -cysteine. Glucagon induced a time and protein synthesis-dependent stimulation of Na(+)-dependent alanine preferring system (system A)-independent AIB transport. The glucagon-induced increase in transport activity was not modified by substrate starvation and not related to changes in the intracellular pool of amino acids. Glucagon did not modify system ASC activity measured by l -cysteine. Therefore the transport activity of AIB independent of system A stimulated by glucagon cannot be attributed to system ASC. This suggests a Na(+)-dependent transport system in rat hepatocytes not identified until now.
Amino Acids↗
Is the L-arginine-nitric oxide pathway involved in endotoxemia-induced muscular hypercatabolism in rats?
We investigated the role of the nitric oxide (NO) synthase (NOS) pathway in muscular metabolism during endotoxemia in four groups of male Wistar rats. Two groups were injected with the lipopolysaccharide (LPS) of Escherichia coli (3 mg/kg), with one group treated using N(G)-nitro-L-arginine methylester ([L-NAME] 85 mg/kg/d) and the other not. The two control groups included one treated with L-NAME and the other not. After 24 hours of fasting, the rats were fed by controlled enteral nutrition and killed on day 3. The results showed that (1) NOS inhibition was detrimental during endotoxemia, increasing lethality from 20% to 80.5%, and (2) NOS inhibition did not modify the hypercatabolic state consecutive to endotoxemia, particularly at the muscular level (nitrogen balance, total-body and muscular weight loss, and muscular protein and glutamine concentrations). However, myofibrillar catabolism was delayed in the LPS-NAME group. In conclusion, NO production is of major importance for survival after an endotoxemic challenge, but contributes weakly to the metabolic response of muscle to injury.
Animals↗
Abnormalities in branched-chain amino acid metabolism in cirrhosis: influence of hormonal and nutritional factors and directions for future research.
Plasma branched-chain amino acid (BCAA) levels are decreased in patients with liver cirrhosis, owing to an increase in BCAA tissue uptake and/or catabolism and a decrease in BCAA production from proteins. Non-specific factors such as malnutrition worsen this picture. Studies of BCAA fluxes and protein turnover in cirrhotic patients have given conflicting results due to patient heterogeneity, differences in method and bias in the expression of results. In well compensated cirrhosis, muscle wasting is moderate and probably due more to decreased protein synthesis than to increased protein catabolism. Hyperinsulinemia has been suggested as the main cause of decreased BCAA levels, by increasing BCAA uptake in muscle and additionally in adipose tissue. However, as depletion of fat stores is frequent in cirrhosis, this effect is certainly quantitatively weak. Also, there is no correlation between state of hyperinsulinemia and decrease in BCAA levels. An effect of cytokines (IL1 and TNF) on muscle BCAA catabolism is a possibility. Until recently, the contribution of the liver to abnormal BCAA metabolism has been underestimated. In cirrhotic liver an increase in liver transamination of branched-chain keto acids (BCKAs) has been suggested and may result from inhibition of liver BCKA dehydrogenase. A modification of protein turnover in cirrhotic liver must be also considered. Lastly, the contribution of non-hepatocyte liver cells, which are activated in cirrhosis, remains to be assessed.
Amino Acids, Branched-Chain↗
Intestinal absorption and permeability in human immunodeficiency virus-infected patients.
BACKGROUND: Impaired intestinal function could account for diarrhoea and weight loss, which are common features of advanced human immunodeficiency virus (HIV) infection. METHODS: We assessed intestinal permeability to lactulose and mannitol and absorption of D-xylose in 96 HIV-infected patients (group I: asymptomatic subjects (CDC-A); group II: symptomatic subjects (CDC-B or C) without body weight loss and/or diarrhoea; group III: 25 acquired immunodeficiency syndrome (AIDS) patients (CDC-C) with severe body weight loss and/or diarrhoea) and 10 healthy subjects as controls. RESULTS: An incremental decrease in urinary D-xylose recoveries was observed, with all groups statistically different from each other. Impaired intestinal permeability was only found in patients of group III (statistically different from all other groups). CONCLUSIONS: These findings suggest a loss of intestinal functional absorptive surface as HIV disease progresses. This process may be present at the early stage of infection. Impaired intestinal permeability is observed later in AIDS patients when digestive signs are present, particularly diarrhoea.
Adult↗
Intestinal permeability in liver cirrhosis: relationship with severe septic complications.
OBJECTIVES: Patients with liver cirrhosis are at high risk of severe septic complications such as spontaneous bacterial peritonitis (SBP) and bacteraemia. The aims of this study were to assess intestinal permeability in patients with liver cirrhosis and to search for a relationship between an impaired intestinal permeability and the occurrence of severe septic complications. METHODS: Intestinal permeability was assessed in a group of 80 cirrhotic patients (Child A, n = 13; Child B, n = 26; Child C, n = 41) and 28 healthy control subjects. A severe septic complication (bacteraemia and/or SBP) occurred in 16 patients, within 10 days before (n = 8 cases) or after (n = 8 cases) the test was performed. Lactulose (LAC) 10 g was given orally together with mannitol (MAN) 5 g, and urinary excretion rates were determined. RESULTS: Urinary mannitol excretion (MAN%) was lower while the LAC/MAN ratio was higher in patients than in control subjects (P < 0.001); these abnormalities were more marked in Child C patients (Child C patients vs control subjects: MAN%, 8.20 +/- 0.79 vs 14.59 +/- 0.58, P < 0.001; LAC/MAN, 0.066 +/- 0.026 vs 0.017 +/- 0.001, P < 0.02). When compared with non-infected patients, septic patients had a lower MAN% and an increased LAC/ MAN ratio (5.45 +/- 1.12 vs 9.83 +/- 0.87, P < 0.02; 0.130 +/- 0.063 vs 0.029 +/- 0.005, P < 0.02). CONCLUSION: Although the main mechanism involved in the decrease in MAN% is likely a reduction in area of the intestinal absorptive surface, these results argue in favour of an increased intestinal permeability in liver cirrhosis, especially in patients with severe infectious complications. The impairment of intestinal function barrier may contribute to severe septic complications in these patients.
Bacteremia↗
Human CD5 signaling and constitutive phosphorylation of C-terminal serine residues by casein kinase II.
CD5 is a lymphocyte surface glycoprotein with a long cytoplasmic domain suitable for phosphorylation and signal transduction, which is involved in the modulation of Ag-specific receptor-mediated activation and differentiation signals. In this study, we use Jurkat T cell transfectants of CD5 cytoplasmic tail mutants to reveal phosphorylation sites relevant to signal transduction. Our results show that casein kinase II (CKII) is responsible for the constitutive phosphorylation of CD5 molecules at a cluster of three serine residues located at the extreme C terminus (S458, S459, and S461). Furthermore, the yeast two-hybrid system demonstrates the specific association between the C-terminal regions of the CD5 cytoplasmic tail and the regulatory beta subunit of CKII. We demonstrate that CKII associates with and phosphorylates the C-terminal region of CD5, a conserved domain known to be relevant for the generation of second lipid messengers, and thereby enables at least one component of its signaling function.
Amino Acid Sequence↗
Effect of indinavir on HIV-related wasting.
OBJECTIVE: To study the effect of the protease inhibitor indinavir on body weight and body composition of subjects with HIV-related wasting. DESIGN: Prospective measurement of body weight in patients who had wasting and were treated with indinavir. A subgroup of 16 representative patients also underwent a metabolic study that included measurements of body composition (skinfolds and bioelectrical impedance) and food intake. Seven from this subgroup who did not have chronic diarrhoea also underwent indirect calorimetry for measurement of resting energy expenditure; the nine patients with wasting and chronic diarrhoea had measurements of faecal losses and intestinal permeability using the lactulose-mannitol test. SETTING: A tertiary care university hospital. PATIENTS: Two hundred and fourteen HIV-infected patients with wasting (less than 95% of usual body weight) had their body weight measured at day 0; 186 patients had a second body weight measurement within the first 100 days of treatment, and 160 patients were weighed a third time, at a median of 176 days. RESULTS: Body weight increased significantly (P < 0.0001) during treatment, whatever the degree of weight loss at baseline. After a median of 176 days on treatment, body weight had increased in 119 out of the 160 patients followed (74.4%; mean weight gain, 6.3+/-SD 3.8 kg; range, 1-18 kg), had not changed in 13 (8.1%) and had fallen in 28 (17.5%; mean weight loss, 4.2+/-3.0 kg; range, 1-12 kg), relative to baseline. Overall, 119 out of the 214 patients (55.6%) from the initial population gained weight. Fat mass, fat-free mass and body cell mass increased significantly in the 16 patients who underwent metabolic studies, together with energy, protein and lipid intake. In the patients with chronic diarrhoea, intestinal permeability improved but there was no change in intestinal losses. In patients who had wasting but not chronic diarrhoea, resting energy expenditure did not change significantly. Body weight changes correlated with changes in the CD4+ cell count (r = 0.882; P = 0.00001) and, to a lesser extent, with changes in the viral load (r = -0.466; P = 0.047). CONCLUSION: Indinavir significantly improved the nutritional status of these patients with HIV-related wasting.
Adult↗
CD95 (Fas/APO-1) induces an increased phosphatidylserine synthesis that precedes its externalization during programmed cell death.
CD95 (Fas, APO-1)-induced programmed cell death (apoptosis) in T cell lines is accompanied by a rapid flip-flop of phosphatidylserine (PtdSer). Externalization of this phospholipid has been previously recognized as one of the early detectable events of cells undergoing apoptosis. We show here that CD95 induces a rapid (detectable at time < 15 min), strong (2.5-fold) but transitory neosynthesis of PtdSer in the Jurkat cell line that precedes its externalization. PtdSer decarboxylation, a mitochondrial specific process, was strongly inhibited by CD95 suggesting that changes in mitochondrial activity take place in the early events of Fas-induced apoptosis and participate in the increased PtdSer synthesis observed. In cells undergoing apoptosis, newly synthesized PtdSer first exposed at the cell surface was in part shed with CD95-induced plasma membrane vesicles, a process that likely explains the transitory effect observed.
Antibodies, Monoclonal↗
Regulation of the serine-base exchange enzyme system by CD4: effects of monoclonal antibodies, jacalin, interleukin 16 and the HIV membrane protein gp120.
Phosphatidylserine (PtdSer) is synthesized by an exchange of the polar head group of phospholipids for a serine residue. The enzyme responsible for this reaction, the serine-base exchange enzyme system (serine-BEES) is inhibited during lymphocyte activation. We show here that triggering the CD4 cell surface molecule in several CD4+ T-cell lines regulates the serine-BEES activity, thus resulting in marked changes in PtdSer synthesis. CD4 ligands able to generate an activating signal in T-cells such as the lectin jacalin, down-regulate the synthesis of PtdSer. In contrast, monoclonal antibodies (mAbs) directed against the CD4 molecule, such as IOT4 and IOT4a, which have previously been described as generating an inhibitory signal to T-cells, induced an up-regulation of the serine-BEES and impaired CD3-induced inhibition of PtdSer synthesis. Similarly, the HIV-gp120 envelope glycoprotein, in both soluble and cross-linked forms, induces an increase in PtdSer synthesis. The protein tyrosine kinase p56lck participates in the regulation of serine-BEES activity because the effect of CD4 mAbs was additive to that of amino-hydroxyflavone, an inhibitor of p56lck. Also, CD4 mAbs were inactive in J Cam 1.6 cells or when the CD3 signals were bypassed by using thapsigargin. These results demonstrate that the CD4 surface molecule can transmit both activating and inhibiting intracellular signals depending on the CD4 ligand used. We suggest that PtdSer synthesis would be one of the intracellular signals that could explain the opposite effects of different CD4 ligands on T-cells.
Antibodies, Monoclonal↗