PPARγ Alleviates Sepsis-Induced Liver Injury by Inhibiting Hepatocyte Pyroptosis via Inhibition of the ROS/TXNIP/NLRP3 Signaling Pathway.

Sepsis is a systemic inflammatory response syndrome caused by a dysregulated host response to infection. Peroxisome proliferator-activated receptor gamma (PPARγ) exerts anti-inflammatory and antioxidative properties. To investigate the potential effects of PPARγ on sepsis-induced liver injury and determine the related mechanisms, C57BL/6 male mice were subjected to cecal ligation and puncture (CLP) to create a sepsis model which was treated with GW1929 or GW9662 to upregulate or downregulate the expression of PPARγ. We found that upregulation of PPARγ decreased the serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBIL), and liver pathological damage and improved the 5-day survival rate. Increased expression of PPARγ also decreased sepsis-induced reactive oxygen species (ROS) by promoting the expression of Nrf2. In addition, upregulated PPARγ inhibited the expression of the TXNIP/NLRP3 signaling pathway by reducing ROS-induced injury in the liver during sepsis, which further reduced NLRP3-mediated pyroptosis and the inflammatory response. The role of PPARγ was further examined in in vitro experiments, where lipopolysaccharide- (LPS-) treated HepG2 and Hep3B cells were incubated with GW1929 or GW9662 to upregulate or downregulate the expression of PPARγ. We found that upregulated PPARγ ameliorated LDH release and improved cell viability. Our results indicated that increased expression of PPARγ reduced ROS levels and inhibited the TXNIP/NLRP3 signaling pathway, resulting in decreased pyroptosis and reduced liver dysfunction during sepsis.

Casein Glycomacropeptide: An Alternative Protein Substitute in Tyrosinemia Type I.

Tyrosinemia type I (HTI) is treated with nitisinone, a tyrosine (Tyr) and phenylalanine (Phe)-restricted diet, and supplemented with a Tyr/Phe-free protein substitute (PS). Casein glycomacropeptide (CGMP), a bioactive peptide, is an alternative protein source to traditional amino acids (L-AA). CGMP contains residual Tyr and Phe and requires supplementation with tryptophan, histidine, methionine, leucine, cysteine and arginine. AIMS: a 2-part study assessed: (1) the tolerance and acceptability of a low Tyr/Phe CGMP-based PS over 28 days, and (2) its long-term impact on metabolic control and growth over 12 months. METHODS: 11 children with HTI were recruited and given a low Tyr/Phe CGMP to supply all or part of their PS intake. At enrolment, weeks 1 and 4, caregivers completed a questionnaire on gastrointestinal symptoms, acceptability and ease of PS use. In study part 1, blood Tyr and Phe were assessed weekly; in part 2, weekly to fortnightly. In parts 1 and 2, weight and height were assessed at the study start and end. RESULTS: Nine of eleven children (82%), median age 15 years (range 8.6-17.7), took low Tyr/Phe CGMP PS over 28 days; it was continued for 12 months in n = 5 children. It was well accepted by 67% (n = 6/9), tolerated by 100% (n = 9/9) and improved gastrointestinal symptoms in 2 children. The median daily dose of protein equivalent from protein substitute was 60 g/day (range 45-60 g) with a median of 20 g/day (range 15 to 30 g) from natural protein. In part 2 (n = 5), a trend for improved blood Tyr was observed: 12 months pre-study, median Tyr was 490 µmol/L (range 200-600) and Phe 50 µmol/L (range 30-100); in the 12 months taking low Tyr/Phe CGMP PS, median Tyr was 430 µmol/L (range 270-940) and Phe 40 µmol/L (range 20-70). Normal height, weight and BMI z scores were maintained over 12 months. CONCLUSIONS: In HTI children, CGMP was well tolerated, with no deterioration in metabolic control or growth when studied over 12 months. The efficacy of CGMP in HTI needs further investigation to evaluate the longer-term impact on blood Phe concentrations and its potential influence on gut microflora.

Acidic Microenvironment Aggravates the Severity of Hepatic Ischemia/Reperfusion Injury by Modulating M1-Polarization Through Regulating PPAR-γ Signal.

Hepatic injury induced by ischemia and reperfusion (HIRI) is a major clinical problem after liver resection or transplantation. The polarization of macrophages plays an important role in regulating the severity of hepatic ischemia/reperfusion injury. Recent evidence had indicated that the ischemia induces an acidic microenvironment by causing increased anaerobic glycolysis and accumulation of lactic acid. We hypothesize that the acidic microenvironment might cause the imbalance of intrahepatic immunity which aggravated HIRI. The hepatic ischemia/reperfusion injury model was established to investigate the effect of the acidic microenvironment to liver injury. Liposomes were used to deplete macrophages in vivo. Macrophages were cultured under low pH conditions to analyze the polarization of macrophages in vitro. Activation of the PPAR-γ signal was determined by Western blot. PPAR-γ agonist GW1929 was administrated to functionally test the role of PPAR-γ in regulating macrophage-mediated effects in the acidic microenvironment during HIRI. We demonstrate that acidic microenvironment aggravated HIRI while NaHCO3 reduced liver injury through neutralizing the acid, besides, liposome abolished the protective ability of NaHCO3 through depleting the macrophages. In vivo and vitro experiment showed that acidic microenvironment markedly promoted M1 polarization but inhibited M2 polarization of macrophage. Furthermore, the mechanistic study proved that the PPAR-γ signal was suppressed during the polarization of macrophages under pH = 6.5 culture media. The addition of PPAR-γ agonist GW1929 inhibited M1 polarization under acidic environment and reduced HIRI. Our results indicate that acidic microenvironment is a key regulator in HIRI which promoted M1 polarization of macrophages through regulating PPAR-γ. Conversely, PPAR-γ activation reduced liver injury, which provides a novel therapeutic concept to prevent HIRI.

Real-World Safety and Effectiveness Evidence of a Microcrystalline Tyrosine-Associated Mite Allergoid in Children and Adolescents with Allergic Rhinitis

Evidence regarding allergen immunotherapy (AIT) in pediatric population is scarce. We have assessed safety and effectiveness of subcutaneous AIT with a microcrystalline tyrosine (MCT)-associated mite allergoid, Acarovac Plus®, in children and adolescents with allergic rhinitis (AR), with and without asthma, in the real-world setting. This was a retrospective, multicenter study including children and adolescents aged 5 years to 17 years with AR, with and without asthma, and sensitized to mites, receiving AIT with Acarovac Plus® during ≥6 months. Primary and secondary objectives were safety and effectiveness, respectively. Effectiveness variables were assessed during 12 months before and after AIT and included unscheduled visits to the healthcare center and emergency room admissions, rhinitis and asthma symptoms according to ARIA and GEMA classifications, respectively, medication use, and patients’ and physicians’ disease perception graded on a visual analog scale (VAS). All 79 patients included had a mean (SD) age of 12.7 (3.3) years. Two patients experienced systemic adverse reactions (none severe). Unscheduled visits to the healthcare center and emergency room admissions decreased (mean (SD) 3.02 [2.48] and 0.63 [1.35] vs. 1.08 [1.38] and 0.09 [0.38], before and after treatment, p < 0.001 and p = 0.001, respectively). After AIT, rhinitis and asthma classification changed (p < 0.0001 for all classifications), showing improvements in symptoms and a significant decrease in rhinitis and use of medication for asthma and VAS scores grading patients’ and physicians’ disease perception (p < 0.001). In conclusion, these results show that AIT with an MCT-associated mite allergoid appears safe and effective in children and adolescents with AR treated in the real-world setting (AU)

Effects of Tyrosine and Tryptophan Supplements on the Vital Indicators in Mice Differently Prone to Diet-Induced Obesity.

We studied the effects of the addition of large neutral amino acids, such as tyrosine (Tyr) and tryptophan (Trp), in mice DBA/2J and tetrahybrid mice DBCB receiving a high-fat, high-carbohydrate diet (HFCD) for 65 days. The locomotor activity, anxiety, muscle tone, mass of internal organs, liver morphology, adipokines, cytokines, and biochemical indices of animals were assessed. The Tyr supplementation potentiated increased anxiety in EPM and contributed to a muscle tone increase, a decrease in the AST/ALT ratio, and an increase in protein anabolism in both mice strains. Tyr contributed to a decrease in liver fatty degeneration and ALT reduction only in DBCB that were sensitive to the development of obesity. The addition of Trp caused an increase in muscle tone and potentiated an increase in anxiety with age in animals of both genotypes. Trp had toxic effects on the livers of mice, which was manifested in increased fatty degeneration in DBCB, edema, and the appearance of micronuclei in DBA/2J. The main identified effects of Tyr on mice are considered in the light of its modulating effect on the dopamine neurotransmitter metabolism, while for the Trp supplement, effects were presumably associated with the synthesis of its toxic metabolites by representatives of the intestinal microflora.

Essential amino acid-enriched whey enhances post-exercise whole-body protein balance during energy deficit more than iso-nitrogenous whey or a mixed-macronutrient meal: a randomized, crossover study.

BACKGROUND: The effects of ingesting varying essential amino acid (EAA)/protein-containing food formats on protein kinetics during energy deficit are undetermined. Therefore, recommendations for EAA/protein food formats necessary to optimize both whole-body protein balance and muscle protein synthesis (MPS) during energy deficit are unknown. We measured protein kinetics after consuming iso-nitrogenous amounts of free-form essential amino acid-enriched whey (EAA + W; 34.7 g protein, 24 g EAA sourced from whey and free-form EAA), whey (WHEY; 34.7 g protein, 18.7 g EAA), or a mixed-macronutrient meal (MEAL; 34.7 g protein, 11.4 g EAA) after exercise during short-term energy deficit. METHODS: Ten adults (mean ± SD; 21 ± 4 y; 25.7 ± 1.7 kg/m2) completed a randomized, double-blind crossover study consisting of three, 5 d energy-deficit periods (- 30 ± 3% of total energy requirements), separated by 14 d. Whole-body protein synthesis (PS), breakdown (PB), and net balance (NET) were determined at rest and in response to combination exercise consisting of load carriage treadmill walking, deadlifts, and box step-ups at the end of each energy deficit using L-[2H5]-phenylalanine and L-[2H2]-tyrosine infusions. Treatments were ingested immediately post-exercise. Mixed-muscle protein synthesis (mixed-MPS) was measured during exercise through recovery. RESULTS: Change (Δ postabsorptive + exercise to postprandial + recovery [mean treatment difference (95%CI)]) in whole-body (g/180 min) PS was 15.8 (9.8, 21.9; P = 0.001) and 19.4 (14.8, 24.0; P = 0.001) greater for EAA + W than WHEY and MEAL, respectively, with no difference between WHEY and MEAL. ΔPB was - 6.3 (- 11.5, - 1.18; P = 0.02) greater for EAA + W than WHEY and - 7.7 (- 11.9, - 3.6; P = 0.002) greater for MEAL than WHEY, with no difference between EAA + W and MEAL. ΔNET was 22.1 (20.5, 23.8; P = 0.001) and 18.0 (16.5, 19.5; P = 0.00) greater for EAA + W than WHEY and MEAL, respectively, while ΔNET was 4.2 (2.7, 5.6; P = 0.001) greater for MEAL than WHEY. Mixed-MPS did not differ between treatments. CONCLUSIONS: While mixed-MPS was similar across treatments, combining free-form EAA with whey promotes greater whole-body net protein balance during energy deficit compared to iso-nitrogenous amounts of whey or a mixed-macronutrient meal. TRIAL REGISTRATION: ClinicalTrials.gov, Identifier no. NCT04004715 . Retrospectively registered 28 June 2019, first enrollment 6 June 2019.

Microbial metabolism of L-tyrosine protects against allergic airway inflammation.

The constituents of the gut microbiome are determined by the local habitat, which itself is shaped by immunological pressures, such as mucosal IgA. Using a mouse model of restricted antibody repertoire, we identified a role for antibody-microbe interactions in shaping a community of bacteria with an enhanced capacity to metabolize L-tyrosine. This model led to increased concentrations of p-cresol sulfate (PCS), which protected the host against allergic airway inflammation. PCS selectively reduced CCL20 production by airway epithelial cells due to an uncoupling of epidermal growth factor receptor (EGFR) and Toll-like receptor 4 (TLR4) signaling. Together, these data reveal a gut microbe-derived metabolite pathway that acts distally on the airway epithelium to reduce allergic airway responses, such as those underpinning asthma.

Phase II trial of SM-88, a cancer metabolism based therapy, in non-metastatic biochemical recurrent prostate cancer.

Background Androgen deprivation therapy (ADT) is a standard treatment for high-risk biochemically-recurrent, non-metastatic prostate cancer (BRPC) but is not curative and associated with toxicity. Racemetyrosine (SM-88) is an amino-acid analogue used with methoxsalen, phenytoin, and sirolimus (MPS) to enhance SM-88 activity. Method A phase 1b/2, open-label trial in BRPC and rising PSA. Patients were given daily SM-88 (230 mg BID), methoxsalen (10 mg), phenytoin (50 mg), and sirolimus (0.5 mg)). Outcome measures included changes in PSA, circulating tumor cells (CTCs) and imaging. Results 34 subjects were screened, 23 treated and 21 remained on study for ≥12 weeks. The median PSA was 6.4 ng/ml (range 1.7-80.1); doubling-time 6.2 months (range 1.4-36.6) and baseline testosterone 319.1 ng/ml (range 2.5-913.7). Median duration of therapy was 6.5 months (2.6-14.0). CTCs (median 48.5 cells/4 ml (range 15-268) at baseline) decreased a median of 65.3% in 18 of 19 patients. For patients who achieved an absolute CTC nadir count of <10 cells/4 ml (n = 10), disease control was 100% i.e. no metastases or PSA progression, while on trial (p = 0.005). PSA fell by ≥50% in 4.3% (1 subject). No patients developed metastatic disease while on treatment (metastases free survival =100%). There were no treatment-related adverse events (AEs) and quality of life was unchanged from baseline on the EORTC QLQ-C30 and QLQ-PR25. Testosterone levels rose slightly on SM-88 and were unrelated to efficacy or toxicity. Conclusions Use of SM-88 was associated with disease control while maintaining QOL. SM-88 may delay the need for ADT and the associated hormonal side effects. Larger trials are planned.Trial registration number, date of registration - NCT02796898, June 13, 2016.

MRI and 18FET-PET Predict Survival Benefit from Bevacizumab Plus Radiotherapy in Patients with Isocitrate Dehydrogenase Wild-type Glioblastoma: Results from the Randomized ARTE Trial.

PURPOSE: To explore a prognostic or predictive role of MRI and O-(2-18F-fluoroethyl)-L-tyrosine (18FET) PET parameters for outcome in the randomized multicenter trial ARTE that compared bevacizumab plus radiotherapy with radiotherpay alone in elderly patients with glioblastoma. PATIENTS AND METHODS: Patients with isocitrate dehydrogenase wild-type glioblastoma ages 65 years or older were included in this post hoc analysis. Tumor volumetric and apparent diffusion coefficient (ADC) analyses of serial MRI scans from 67 patients and serial 18FET-PET tumor-to-brain intensity ratios (TBRs) from 31 patients were analyzed blinded for treatment arm and outcome. Multivariate Cox regression analysis was done to account for established prognostic factors and treatment arm. RESULTS: Overall survival benefit from bevacizumab plus radiotherapy compared with radiotherapy alone was observed for larger pretreatment MRI contrast-enhancing tumor [HR per cm3 0.94; 95% confidence interval (CI), 0.89-0.99] and for higher ADC (HR 0.18; CI, 0.05-0.66). Higher 18FET-TBR on pretreatment PET scans was associated with inferior overall survival in both arms. Response assessed by standard MRI-based Response Assessment in Neuro-Oncology criteria was associated with overall survival in the bevacizumab plus radiotherapy arm by trend only (P = 0.09). High 18FET-TBR of noncontrast-enhancing tumor portions during bevacizumab therapy was associated with inferior overall survival on multivariate analysis (HR 5.97; CI, 1.16-30.8). CONCLUSIONS: Large pretreatment contrast-enhancing tumor mass and higher ADCs identify patients who may experience a survival benefit from bevacizumab plus radiotherapy. Persistent 18FET-PET signal of no longer contrast-enhancing tumor after concomitant bevacizumab plus radiotherapy suggests pseudoresponse and predicts poor outcome.

Dietary Aromatic Amino Acid Requirements During Early and Late Gestation in Healthy Pregnant Women.

BACKGROUND: Phenylalanine and tyrosine (referred to as total aromatic amino acids; TAAs) are essential for protein synthesis, and are precursors for important catecholamines. Current estimated average requirement (EAR) recommendations for TAA during pregnancy are 36 mg·kg-1·d-1, and has not been experimentally determined. OBJECTIVES: The aim was to determine TAA requirements (dietary phenylalanine in the absence of tyrosine) during early and late gestation using the indicator amino acid oxidation (IAAO, with L-[1-13C]leucine) technique. METHODS: Nineteen healthy pregnant women (age 22-38 y) were studied at a range of phenylalanine intakes (5 to 100 mg·kg-1·d-1) in early (13-19 wk) and/or late (33-39 wk) pregnancy for a total of 51 study days. Graded test intakes were provided as 8 hourly isonitrogenous and isocaloric meals. Breath samples were collected for 13C enrichment analysis on an isotope ratio mass spectrometer. A plasma sample was collected and analyzed for phenylalanine and tyrosine concentrations on an amino acid analyzer. The TAA requirement in early and late pregnancy was calculated using 2-phase linear regression crossover analysis that identified breakpoints in 13CO2 production (the requirement) in response to phenylalanine intakes. RESULTS: TAA requirement during early pregnancy was 44 mg·kg-1·d-1 (95% CI: 28.3, 58.8) and during late pregnancy was 50 mg·kg-1·d-1 (95% CI: 36.1, 63.1). In early and late pregnancy, plasma phenylalanine and tyrosine concentrations rose linearly in response to graded phenylalanine intakes. CONCLUSIONS: Our results suggest that the current EAR of 36 mg·kg-1·d-1 for TAAs is underestimated. When compared with results previously determined in nonpregnant adults, early pregnancy requirements were similar (43 compared with 44 mg·kg-1·d-1, respectively). During late pregnancy, a 14% higher TAA requirement was observed when compared with early pregnancy. The results from this study have potential implications for creating gestation stage-specific TAA recommendations.

A PPAR-α agonist protects the non-adrenergic, non-cholinergic inhibitory system of guinea pig trachea from the effect of inhaled ammonium persulphate: a pilot study.

SUMMARY: Aim of the study. Inhaled ammonium persulphate (AP) reduces non adrenergic, non cholinergic (NANC) relaxation in the guinea pig trachea, as a part of its inflammatory effects. Peroxisome Proliferator-Activated Receptor (PPAR) stimulation has shown anti-inflammatory properties. This study aimed at evaluating whether the PPAR-α agonist WY 14643 can prevent the reduction in NANC relaxation caused by inhaled AP in the guinea pig trachea. Materials and Methods. Four groups of ten male guinea pigs were treated for three weeks with inhaled AP (10 mg/m3, 30 min per day, group A), saline (group B), AP and WY 14643 (0.36 µM/die, per os, group C), and AP, WY 14643 and the PPAR-α antagonist GW 6471 (0.36 µM/die, per os, group D). NANC relaxations to electrical field stimulation (EFS) at 3 Hz were evaluated in whole tracheal segments as intraluminal pressure changes. Results. The tracheal NANC relaxations were reduced by 90.3% in group A, as compared to group B. In group C, they were reduced by only 22.2%. In group D, they were reduced by 92.6 %. PPAR-α receptors were detected in inhibitory nerve fibers within the trachea as shown by immonohistochemical analysis. Conclusions. The PPAR-α agonist WY 14643 protects the NANC inhibitory system of the guinea pig trachea from the effect of inhaled ammonium persulphate and its protective effect is antagonized by GW 6471. PPAR-α might be exploited.

Tyrosine supplement ameliorates murine aGVHD by modulation of gut microbiome and metabolome.

BACKGROUND: Microbial communities and their metabolic components in the gut are of vital importance for immune homeostasis and have an influence on the susceptibility of the host to a number of immune-mediated diseases like acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, little is known about the functional connections between microbiome and metabolome in aGVHD due to the complexity of the gastrointestinal environment. METHOD: Initially, gut microbiota and fecal metabolic phenotype in aGVHD murine models were unleashed by performing 16S ribosomal DNA gene sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS)-based metabolomics. FINDINGS: The group with aGVHD experienced a significant drop in Lachnospiraceae_unclassified but an increase in the relative abundance of Clostridium XI, Clostridium XIVa and Enterococcus. Meanwhile, a lower content of tyrosine was observed in the gut of aGVHD mice. The correlation analysis revealed that tyrosine-related metabolites were inversely correlated with Clostridium XIVa, besides, Blautia and Enterococcus also displayed the negative tendency in aGVHD condition. Apart from exploring the importance and function of tyrosine, different tyrosine diets were offered to mice during transplantation. Additional tyrosine supplements can improve overall survival, ameliorate symptoms at the early stage of aGVHD and change the structure and composition of gut microbiota and fecal metabolic phenotype. In addition, aGVHD mice deprived from tyrosine displayed worse manifestations than the vehicle diet group. INTERPRETATION: The results demonstrated the roles and mechanisms of gut microbiota, indispensable metabolites and tyrosine in the progression of aGVHD, which can be an underlying biomarker for aGVHD diagnosis and treatment. FUNDING: This research was funded by the International Cooperation and Exchange Program (81520108002), the National Key R&D Program of China, Stem Cell and Translation Research (2018YFA0109300), National Natural Science Foundation of China (81670169, 81670148, 81870080 and 91949115) and Natural Science Foundation of Zhejiang Province (LQ19H080006).

First-in-human phase I study of JPH203, an L-type amino acid transporter 1 inhibitor, in patients with advanced solid tumors.

This open-label first-in-human study evaluated JPH203, which is a novel selective L-type amino acid transporter 1 inhibitor. We also evaluated the association between the N-acetyltransferase 2 phenotype and outcomes. Japanese patients with advanced solid tumors received daily intravenous JPH203 treatment for 7 days, followed by a 21-day rest period, at escalating doses of 12-85 mg/m2. Dose-limiting toxicities were evaluated during the first cycle using a 3 + 3 design. The study enrolled 17 patients, although grade 3 liver dysfunction was detected in one of six patients receiving 60 mg/m2 and in the first patient to receive 85 mg/m2. Further enrollment was terminated and the maximum tolerated dose was defined as 60 mg/m2. The AUC∞ increased between 12 mg/m2 and 25 mg/m2, although no differences were observed at 25-40 mg/m2. Partial response was observed for one patient with biliary tract cancer (BTC) at the 12 mg/m2 dose, and disease control was achieved by 3 of 6 patients at the 12 mg/m2 and 25 mg/m2 dose levels. Based on these results, we recommend a phase II dose of 25 mg/m2. The disease control rate for BTC was 60%. Two patients with grade 3 liver dysfunction had the rapid N-acetyltransferase 2 phenotype, and disease control was more common for the non-rapid phenotype (50% vs. 12.5%). It appears that JPH203 was well-tolerated and provided promising activity against BTC. The N-acetyltransferase 2 phenotype might help predict the safety and efficacy of JPH203. Clinical trial registration: UMIN000016546.

Protein Requirements of Elderly Chinese Adults Are Higher than Current Recommendations.

BACKGROUND: Due to a lack of research data on the protein requirements of the elderly in China, the estimated average requirement (EAR) and the recommended nutrient intake (RNI) of protein in the elderly remain the same as those in young and middle-aged people at 0.98 g/(kg·d). OBJECTIVE: The objective of this study was to determine the protein requirements of healthy Chinese adults >65y old through use of the indicator amino acid oxidation (IAAO) method. METHODS: Seven healthy adult men and 7 healthy adult women participated in the study, with protein intakes ranging from 0.3 to 1.8 g/(kg·d). The diets were isocaloric and provided energy at a 1.5 resting energy expenditure. Protein was given based on the lactalbumin. Phenylalanine and tyrosine were added to protein doses of 0.3-1.5 g/kg according to the highest dose of protein content [1.8 g/(kg·d)]. Phenylalanine and tyrosine concentrations were kept constant at each protein dose. The mean protein requirement was determined by applying a nonlinear mixed-effects model analysis to the F13CO2, which identified a breakpoint in F13CO2 in response to graded amounts of protein. This trial was registered with the Chinese clinical trial registry as ChiCTR-BOC-17010930. RESULTS: Protein EAR and RNI for healthy elderly Chinese adults were determined to be 0.91 and 1.17 g/(kg·d), respectively, based on the indicator amino acid oxidation technique. CONCLUSIONS: The estimates of protein requirements for Chinese adults >65 y in the present study are 3.4% and 19.4% higher than the current estimated requirements, 0.88 g/(kg·d) for EAR and 0.98 g/(kg·d) for RNI.

Baseline-dependent effect of dopamine's precursor L-tyrosine on working memory gating but not updating.

Adaptive goal-directed behavior requires a dynamic balance between maintenance and updating within working memory (WM). This balance is controlled by an input-gating mechanism implemented by dopamine in the basal ganglia. Given that dopaminergic manipulations can modulate performance on WM-related tasks, it is important to gain mechanistic insight into whether such manipulations differentially affect updating (i.e., encoding and removal) and the closely-related gate opening/closing processes that respectively enable/prevent updating. To clarify this issue, 2.0 g of dopamine's precursor L-tyrosine was administered to healthy young adults (N = 45) in a double-blind, placebo-controlled, within-subjects study. WM processes were empirically distinguished using the reference-back paradigm, which isolates performance related to updating, gate opening, and gate closing. L-tyrosine had a selective, baseline-dependent effect only on gate opening, which was evidenced by markedly reduced variance across subjects in gate opening performance in the L-tyrosine compared with the placebo condition, whereas the whole-sample average performance did not differ between conditions. This indicates a pattern of results whereby low-performing subjects improved, whereas high-performing subjects were impaired on L-tyrosine. Importantly, this inverted U-shaped pattern was not explained by regression to the mean. These results are consistent with an inverted-U relationship between dopamine and WM, and they indicate that updating and gating are differentially affected by a dopaminergic manipulation. This highlights the importance of distinguishing these processes when studying WM, for example, in the context of WM deficits in disorders with a dopaminergic pathophysiology.

Characterization of the metabolites of GW1929 in rat by liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

RATIONALE: GW1929 is a potent PPAR-γ activator. To fully understand its mechanism of action, it is necessary to study the in vitro and in vivo metabolism. METHODS: For in vitro metabolism, GW1929 was incubated with rat hepatocytes at 37°C for 2 h. For in vivo metabolism, rats were orally administered with GW1929 at a single dose of 10 mg/kg and plasma, urinary and fecal samples were collected at defined time points. All the samples were analyzed by the developed ultra-high-performance liquid chromatography combined with tandem mass spectrometry. The structures of metabolites were proposed according to their accurate masses and product ions. RESULTS: A total of 17 metabolites, including seven glucuronide conjugates, were detected and structurally identified. M4 (hydroxylation), M13 (demethylation) and M14 (hydroxylation) were the most abundant metabolites. The metabolic pathways of GW1929 referred to hydroxylation, demethylation, deamination and glucuronidation. CONCLUSIONS: The present study provided new information on the in vitro and in vivo metabolic profiles of GW1929 which will be helpful for a better understanding of the mechanism of the elimination of GW1929.

Oral L-Tyrosine Supplementation Improves Core Temperature Maintenance in Older Adults.

INTRODUCTION: During cold exposure, an increase in sympathetic nerve activity evokes vasoconstriction (VC) of cutaneous vessels to minimize heat loss. In older adults, this reflex VC response is impaired thereby increasing their susceptibility to excess heat loss and hypothermia. Because L-tyrosine, the amino acid substrate necessary for catecholamine production, has been shown to augment reflex VC in age skin, we hypothesize that oral ingestion of L-tyrosine will attenuate the decline in core temperature (Tc) during whole-body cooling in older adults. METHODS: In a randomized, double-blind design, nine young (25 ± 3 yr) and nine older (72 ± 8 yr) participants ingested either 150 mg·kg of L-tyrosine or placebo before commencing 90 min of whole-body cooling to decrease skin temperature to approximately 29.5°C. Esophageal temperature and forearm laser Doppler flux (LDF) were measured continuously throughout the protocol to provide an index of Tc and skin blood flow, respectively. The change in esophageal temperature (ΔTES) was the difference in temperature at the end of cooling subtracted from baseline. Cutaneous vascular conductance (CVC) was calculated as CVC = LDF/mean arterial pressure and expressed as a percent change from baseline (%ΔCVCBASELINE). RESULTS: Oral tyrosine ingestion augmented the cutaneous VC response to cooling in older adults (placebo, 14.4 ± 2.0; tyrosine, 32.7% ± 1.7% ΔCVCBASELINE; P < 0.05). Additionally, tyrosine improved Tc maintenance throughout cooling in older adults (placebo, -0.29 ± 0.07; tyrosine, -0.07 ± 0.07 ΔTES; P < 0.05). Both the cutaneous VC and Tc during cooling were similar between young and older adults supplemented with tyrosine (P > 0.05). CONCLUSIONS: These results indicate that L-tyrosine supplementation improves Tc maintenance in response to acute cold exposure in an older population.

Inhibitory effect of isomaltodextrin on tyrosine metabolite production in rat gut microbiota.

We examined the effect of isomaltodextrin (IMD), a soluble dietary fiber, on production of putrefactive products by intestinal bacteria using a tyrosine load test to measure phenol production in IMD-treated rats. We observed a significant increase in phenol and p-cresol concentrations in rats administered with only tyrosine, but not for rats co-administered tyrosine and IMD. To elucidate the mechanism of this effect, we analyzed the intestinal microbiota in each group and found that although IMD had no direct effect on the proportion of bacteria known to produce phenols, it did alter the balance of intestinal microbiota. The results suggested that changes in the intestinal microbiota composition reduced the metabolic capacity for tyrosine and in turn suppressed production of phenol or p-cresol, putrefactive products in the intestine.