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OBJECTIVES. The goal of the study was to determine whether reactive oxygen species (ROS) mediates cytomegalovirus (CMV)–induced labyrinthitis. STUDY DESIGN. Murine model of CMV infection. SETTING. University of Utah laboratory. SUBJECTS AND METHODS. Nrf2 knockout mice were inoculated with murine CMV. Auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs) were then performed on these and uninfected controls. BALB/c mice were inoculated with murine CMV to determine whether a marker for ROS production, dihydroethidium (DHE), is expressed 7 days after inoculation. Finally, 2 antioxidants—D-methionine and ACE-Mg (vitamins A, C, and E with magnesium)—were administered 1 hour before and after infection in inoculated mice for 14 days. Temporal bones were harvested at postnatal day 10 for DHE detection. ABR and DPOAE testing was done at postnatal day 30. Scanning electron microscopy was also performed at postnatal day 30 to evaluate outer hair cell integrity. RESULTS. Nrf2-infected mice had worse hearing than uninfected mice (P < .001). A statistically significant increase in DHE fluorescence was detected in BALB/c-infected mice as compared with uninfected mice 7 days after inoculation. D-methionine- and ACE-Mg-treated mice demonstrated an attenuation of the DHE fluorescence and a significant improvement in ABR and DPOAE thresholds when compared with untreated infected controls (P

Objective: This exploratory Phase 2 clinical trial is the first determining safety and efficacy of oral D-methionine (D-met) in reducing cisplatin-induced ototoxicity.Design: Randomised parallel do...

Objective Determine if D-methionine (D-met) rescue prevents temporary threshold shift (TTS) from steady-state or impulse noise and determine D-met's impact on serum and cochlear antioxidant levels. Design D-met at 50, 100 or 200 mg/kg/doses were administered 0, 6 and 18 hours-post noise. ABRs at baseline and 24 hours post-noise measured TTS. Serum (SOD, CAT, GR, GPx) and cochlear (GSH, GSSG) antioxidant levels measured physiological influence. Three control groups, with impulse or steady-state or without noise, were saline-injected. Study sample Ten Chinchillas/group. Results D-met rescue did not significantly reduce TTS or impact serum CAT, SOD, GPx or GR levels vs. noise-exposed control groups, but TTS was greater in all groups relative to no-noise controls. D-met significantly elevated CAT at 50 mg/kg vs. steady-state controls and SOD at 200 mg/kg vs. impulse noise controls. D-met significantly reduced cochlear GSH/GSSG ratios in the 100 mg/kg D-met group vs. impulse noise controls. Conclusions While D-met rescue has reduced permanent threshold shift in previous studies, it did not reduce TTS in this study. However, D-met rescue did alter selective serum and cochlear oxidative state changes 24 hours post-noise relative to controls. Results demonstrate TTS studies do not always predict PTS protection in otoprotectant experimental designs.

Objective To study the effects of D-methionine in a mouse model of noise-induced hearing loss (NIHL). Methods We investigated changes in auditory function and microscopic cochlear structure in a mouse model of NIHL, and carried out 4-hydroxynonenal (4-HNE) immunostaining and terminal deoxynucleotidyl transferase dUTP nick-end labeling, and examined expression levels of connexins 26 and 30 by western blot. Results The auditory brainstem response threshold was significantly increased by noise exposure. Noise exposure also damaged the inner and particularly the outer hair cells in the cochlear basement membrane, while histochemistry demonstrated only scattered loss of hair cells in the basement membrane in mice treated with D-methionine before or after noise exposure. D-methionine inhibited apoptosis in the cochlear basement membrane, stria vascularis, and spiral ligament. 4-HNE expression in the basement membrane, stria vascularis, and spiral collateral ligament was increased by noise exposure, but this increase was attenuated by D-methionine. Connexin 26 and connexin 30 expression levels were reduced by noise exposure, and this effect was similarly attenuated by D-methionine administered either before or after noise exposure. Conclusion D-methionine administered before or after noise exposure could rescue NIHL by protecting cochlear morphology, inhibiting apoptosis, and maintaining connexin 26 and 30 expression.

Porphyromonas gingivalis biofilms are implicated in the pathology of peri-implantitis and periodontitis. In this study, D-arginine (R), D-methionine (M), D-histidine (H), and a mixture of these D-amino acids (D-AAs) were investigated as an effective therapeutic strategy against P. gingivalis biofilms. The bacterial growth activity and minimum inhibitory concentrations were determined for each D-AA, along with the effects of the D-AAs mixture on biofilm development, morphology, structure, extracellular polysaccharides (EPS), cytotoxicity towards commensals, and bacterial structure. The D-AA mixture delayed the proliferation of P. gingivalis, changed its membrane structure, and decreased biofilm thickness and integrity, as compared with individual D-AAs. The EPS content increased with the concentration of D-AAs. The present study shows that a 4 mM RMH, triple D-AA mixture, enhanced deleterious effects on P. gingivalis biofilms without any cytotoxicity compared with individual D-AAs, thus providing a new strategy for the treatment of peri-implantitis and periodontitis.

Test D-methionine (D-met) as an otoprotectant from kanamycin-induced ototoxicity and determine the lowest maximally protective D-met dose.Auditory brainstem responses (ABR) were measured at 4, 8, 14, and 20 kHz at baseline and two, four, and six weeks after kanamycin and D-met administration initiation. ABR threshold shifts assessed auditory function. Following six-week ABR testing, animals were decapitated and cochleae collected for outer hair cell (OHC) quantification.Eight groups of 10 male pigmented guinea pigs were administered a subcutaneous kanamycin (250 mg/kg/dose) injection once per day and an intraperitoneal D-met injection (0 (saline), 120, 180, 240, 300, 360, 420, or 480 mg/kg/day) twice per day for 23 days.Significant ABR threshold shift reductions and increased OHC counts (p ≤ 0.01) were measured at multiple D-met-dosed groups starting at two-week ABR assessments. A 300 mg/kg/day optimal otoprotective D-met dose provided 34-41 dB ABR threshold shift reductions and OHC protection. Lesser, but significant, D-met otoprotection was measured at lower and higher D-met doses.D-met significantly reduced ABR threshold shifts and increased OHC percentages compared to kanamycin-treated controls. Results may be clinically significant particularly for multidrug-resistant tuberculosis patients who frequently suffer from kanamycin-induced hearing loss in developing countries.

A N-balance study was conducted to compare the effect of D-methionine (D-Met) or L-methionine (L-Met) supplementation on N balance, gut morphology and antioxidant status of weaned pigs. Fifty-six weaned barrows (10.5 ± 1.2 kg initial BW) were allotted to 7 diets in 2 blocks. A Met-deficient basal diet (BD; 0.24% standardized ileal digestible (SID) Met) but adequate in other AA, was supplemented with 3 graded levels (0.036, 0.072, and 0.108%) of D-Met or L-Met. After a 7-d adaptation, feces and urine were collected quantitatively for 5 d to determine N balance. At the completion of the experiment, blood samples were collected from all pigs. Pigs fed the BD and pigs fed the highest level of SID Met (0.34%) of both Met sources were euthanized and tissue samples from liver, kidney, muscle (longissimus dorsi), duodenal and jejunal mucosa were collected. N retention as % of N intake increased (P < 0.001; 67, 72, 73, 74, 71, 74, 74%, respectively) by graded supplemental level of D-Met or L-Met. However, there was no interaction between Met source and supplemental level for all N-balance metrics. Using a slope-ratio regression, the bioavailability of D-Met relative to L-Met was 100.1% (95% confidence intervals: 85-116%) based on N retention (% of N intake). Villus height and crypt depth in the duodenum and jejunum were not affected by Met sources. Pigs fed the D-Met diet had a greater (P < 0.05) total glutathione concentration in liver (4.9 vs. 1.5 µM) vs. BD. However, total antioxidant capacity and concentration of thiobarbituric acid-reactive substances in liver, muscle or plasma samples were not different among treatments. Supplementation with D-Met increased glutathione peroxidase activity in kidney (878 vs. 413 and 229 mU/mL; P < 0.05) compared with BD or L-Met diet, however, activity of glutathione reductase in liver and kidney were not affected by treatments. These data indicate that D-Met and L-Met are equally efficient to support N retention, intestinal morphology and oxidative status in weaned pigs.

Title ofthe paper: The efficiency of utilization of intestinal digestible indispensable amino aeids in growing bulls There are problems to determine the efficiency of protein deposition of intestinal absorbed amino aeids, because it cannot be exeluded that the amount of single or some indispensable amino acid (IAA) can influence the growing Performance of the animal. The dependence of amino acid gain on the flux of essential absorbable amino aeids into the duodenum was studied in growing bulls to calculate the utilization rate of these amino aeids. Four growing bulls (Schwarzbuntes Milchrind, BW: 240–310 kg) with duodenal T-type cannulas were fed diets varying in crude protein content. Energy level was 11,2 MJ ME/kg DM. The efficiency for the different absorbable IAA was decreased with increasing nutritional level. This is in contrast with the constant utilization factor ofthe protein evaluation system (AfB, 1995; 1997). The efficiency of utilization of apparently digestible IAA for protein retention was highest for His and Met and amounted to 33 (He), 34 (Phe and Thr), 38 (Lys and Val), 41 (Leu), 52 (Met) und 76 (His) %, respectively. The intersection ofthe regression curve (AA-deposition against apparently digestible AA) with the abscissae resulted in the maintenance requirement of absorbable amino acid. For growing bulls (BW: 300 kg) a value of 4,7 g/d histidine and 4,2 g/d methionine was determined, but more investigations are necessary in this field.

In the environment bacteria share their habitat with a great diversity of organisms, from microbes to humans, animals and plants. In these complex communities, the production of extracellular effectors is a common strategy to control the biodiversity by interfering with the growth and/or viability of nearby microbes. One of such effectors relies on the production and release of extracellular D-amino acids which regulate diverse cellular processes such as cell wall biogenesis, biofilm integrity, and spore germination. Non-canonical D-amino acids are mainly produced by broad spectrum racemases (Bsr). Bsr's promiscuity allows it to generate high concentrations of D-amino acids in environments with variable compositions of L-amino acids. However, it was not clear until recent whether these molecules exhibit divergent functions. Here we review the distinctive biological roles of D-amino acids, their mechanisms of action and their modulatory properties of the biodiversity of complex eco-systems.

In this work the vibrational properties of d -methionine crystal submitted to high pressure were investigated through Raman spectroscopy. The measurements covered the pressure range from 0.0 to 7.0 GPa. From the analysis of the spectra we were able to identify two reversible pressure induced phase transitions: the first at 2.0 GPa and the second at 2.5 GPa. The three phases are characterized by different number of peaks associated with the rocking of ( C O 2 − ) and with the stretching of CSC, among others. A comparison between the behavior of d -methionine and l -methionine under high pressure is furnished as well as a discussion about the symmetries of the crystal in the two high pressure phases.

The objective of this study was to compare the effects of two isoforms of methionine (Met) supplementation, L-Met or D-Met, on transcriptome expression in broiler chickens under acute heat stress. A total of 240 one-day-old chicks were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement: thermo-neutral vs. acute heat-stress and L-Met vs. D-Met supplementation. On day 14, the heat-stressed group was exposed to 32°C for 6 h, while the others remained at 25ºC. Six chicks per treatment were randomly selected and harvested to isolate total RNA from the blood, ileum, and liver tissues. Two RNA samples from each tissue of the same treatment group were randomly selected and pooled with equal amount. A total of 1.87 billion of raw reads were obtained from 36 samples (four treatments × three tissues × three composited replicates) using the Illumina HiSeq 4000 platform. The reads, mapped to the reference genome build (Gallus_gallus-5.0), were used to identify differentially expressed genes (DEG, false-discovery rate < 0.05) using DESeq2. Functional enrichment of DEG was tested using DAVID. A total of 38, 71, and 16 genes were differentially expressed in response to the interaction between heat stress and Met isoforms in the blood, ileum, and liver, respectively. These DEGs were functionally enriched for regulation of cholesterol homeostasis, gluconeogenesis, and bile acid synthesis. Unlike the L-Met group, IL4I1, SERPIN1, and CSRP2, related to immune response, neuroprotection, cell proliferation, and dedifferentiation, were all increased by heat stress in the D-Met group. The expression of PCK1, CYP7A1, SORCS1, related to abnormally increased blood glucose by heat stress, were also changed in the D-Met. Compared to D-Met, L-Met supplementation appeared to reduce abnormal cellular and physiological responses by heat stress in broilers.

3 Abstract: A study was conducted to evaluate an herbal methionine replacement product in diets for young broiler chicks. A corn-soybean meal diet that was complete in all respects but methionine was prepared and divided into three aliquots. One was supplemented with 0.30% DL methionine and another was supplemented with the herbal methionine replacement product. Each of these was then blended with the unsupplemented basal diet to provide diets with 0, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30% of either DL methionine or the herbal methionine replacement product. Each diet was fed to twelve pens of five male broiler type chicks each in electrically heated battery brooders. The diets and tap water were provided for ad libitum feeding from day of hatch to 18 d of age. Analysis of the diets indicated that the methionine activity of the diets with DL methionine was close to expected values but no apparent increase in analyze d methionine activity in diets supplemented with the herbal methionine replacement product. Body weight gain and feed conversion of birds fed the diets with DL methionine were significantly superior to that of birds fed the diets with the herbal methionine replacement product. No significant differences were observed between birds fed the two products for weight of digestive or immune organs when expressed as a percentage of body weight. These data suggest that the herbal methionine replacement product is not suitable for use as a methionine source in diets for young broiler chicks.

Rumen-protected forms of Met contain an equimolar mixture of the D- and L-isomers. Only L-Met can be directly used for protein synthesis, but it is unclear how much of the D-isomer can be transformed into L-Met in ruminants. Four lactating dairy cows, with an average milk yield of 32.4 kg/d, received a basal diet (12.5% crude protein, supplying 1,718 g/d of metabolizable protein) in 12 equal meals per day plus an abomasal infusion of amino acids (590 g/d, casein profile without Met). They were used in 3 consecutive studies to determine utilization of D-Met. First, the cows each received portal vein infusions for d of 5, 10, or 15 g/d of DL-Met in a Youden square. On the last day of each period, 6 arterial samples were collected at 45-min intervals. Concentrations of L- and D-Met were determined on a chiral column by gas chromatography-mass spectrometry. Portal infusion of 5, 10, and 15 g/d of DL-Met increased plasma total Met concentrations (19.7, 25.0, and 34.4±0.6 μM) and the proportion of Met as D (19.4, 30.5, and 37.3±0.7%). The fractional removal of D-Met was 6 to 7 times lower than the fractional removal of L-Met, with mean half-lives of 52 versus 8 min, respectively. Second, the same cows were infused for 8 h with L[methyl-(2)H(3)]Met at 1.3 mmol/h; at 2 h, cows received a bolus injection i.v. of D-[1-(13)C]Met (6.8 mmol), and arterial samples were collected after 10, 20, 30, 40, 60, 90, 120, 150, 180, 240, 300, 360, 420, and 480 min. Expressed relative to L-[(12)C]Met; that is, as tracer:tracee ratios, enrichments of plasma D-[1-(13)C]Met and L-[1-(13)C]Met averaged 1.77±0.14 and 0.144±0.026, respectively, 10 min after the bolus injection and declined exponentially thereafter. A minimum of 75±3% of the D-[1-(13)C]Met was transformed into L-[1-(13)C]Met. Third, the cows received, in a crossover design, an abomasal infusion for D of either DL-Met or L-Met (1g/d) and, on the last day of each experimental period, blood samples were collected simultaneously from arterial, portal, hepatic, and mammary vessels. Arterial total Met concentrations were higher with DL- versus L-Met infusions (37.4 vs. 25.4±0.5 μM), with 37.1±5.0% as D-Met. The mammary gland did not extract any D-Met. Hepatic removal of D-Met was observed, but was numerically lower than the fractional extraction of L-Met. In conclusion, much of the D-Met is transformed into L-Met by the dairy cow but at a slow rate. No uptake of D-Met occurs across the mammary gland but L-Met synthesized from the D-isomer elsewhere in the body can be utilized for milk protein synthesis.

Despite efforts at public health awareness and stringent industrial standards for hearing protection, noise-induced hearing loss (NIHL) remains a formidable public health concern. Although many antioxidants have proven to be beneficial in the laboratory for prevention of permanent NIHL, low-dose combinations of compounds with different biochemical mechanisms of action may allow long-term administration with fewer side effects and equal efficacy. The mixture of D-methionine and N-acetyl-L-cysteine administered at levels less than 10% of standard dosing has not been previously reported.Twenty-six female adult Chinchilla laniger were placed in 4 study groups, consisting of (1) a group receiving combination 12.5 mg/kg each D-methionine and N-acetyl-L-cysteine (DMET/NAC group), (2) a group receiving 12.5 mg/kg D-methionine (DMET-only group), (3) a group receiving 12.5 mg/kg N-acetyl-L-cysteine (NAC-only group), and (4) saline controls.Laboratory.All groups received twice-daily intraperitoneal injections 2 days prior to noise exposure, 1 hour before and after exposure on day 3, and for 2 days subsequently, totaling 10 doses of 125 mg/kg for each antioxidant over 5 days.Although NAC-only animals paralleled saline control recovery during 3 weeks, the DMET-only group revealed gradual improvement with statistically significant recovery in the middle frequencies. The DMET/NAC group showed significant improvement at most frequencies compared with controls (P.001 and P.05).Significant recovery of hearing was observed following continuous noise exposure with either DMET only or a combination of low-dose DMET/NAC, demonstrating a considerably lower dose of antioxidants required than previously reported for hearing recovery following acoustic trauma.

Conclusion: The findings from this study extend the use of the local application of D-methionine (D-met) to protect against acoustic trauma and demonstrate that D-met slowly diffuses from the perilymph. Objectives: The objectives of the study were to determine the effect of D-met on auditory function and morphology after acoustic trauma and to measure the concentration of D-met in perilymph. Methods: Auditory thresholds were determine before, immediately after, and 24 h after acoustic trauma. Cochleae were analyzed using immunocytochemistry for c-Fos, TUJI, and cytochrome c. The concentration of D-met was determined from perilymph. Results: Protection against acoustic trauma (immediately and 24 h post trauma) on auditory brainstem thresholds was found at a time when the concentration of D-met in perilymph showed a fivefold increase above basal levels. The local application of D-met to the guinea pig cochlea results in elevated D-met concentrations that are maintained in the perilymph for at least...

Background: There are close links between chemotherapy-induced intestinal mucositis and microbiota dysbiosis. Previous studies indicated that D-methionine was an excellent candidate for a chemopreventive agent. Here, we investigated the effects of D-methionine on cisplatin-induced mucositis. Materials and methods: Male Wistar rats (176–200 g, 6 weeks old) were given cisplatin (5 mg/kg) and treated with D-methionine (300 mg/kg). Histopathological, digestive enzymes activity, oxidative/antioxidant status, proinflammatory/anti-inflammatory cytokines in intestinal tissues were measured. Next-generation sequencing technologies were also performed to investigate the gut microbial ecology. Results: D-methionine administration increased villus length and crypt depth and improved digestive enzyme (leucine aminopeptidase, sucrose and alkaline phosphatase) activities in the brush-border membrane of cisplatin-treated rats ( p < 0.05). Furthermore, D-methionine significantly attenuated oxidative stress and inflammatory reaction and increased interleukin-10 levels in cisplatin-induced intestinal mucositis ( p < 0.05). Cisplatin administration resulted in high relative abundances of Deferribacteres and Proteobacteria and a low diversity of the microbiota when compared with control groups, D-methionine only and cisplatin plus D-methionine. Cisplatin markedly increased comparative abundances of Bacteroides caccae, Escherichia coli, Mucispirillum schaedleri, Bacteroides uniformis and Desulfovibrio C21-c20, while Lactobacillus was almost completely depleted, compared with the control group. There were higher abundances of Lactobacillus, Lachnospiraceae, and Clostridium butyrium in cisplatin plus D-methionine rats than in cisplatin rats. D-methionine treatment alone significantly increased the number of Lactobacillus reuteri. Conclusion: D-methionine protects against cisplatin-induced intestinal damage through antioxidative and anti-inflammatory effects. By enhancing growth of beneficial bacteria (Lachnospiraceae and Lactobacillus), D-methionine attenuates gut microbiome imbalance caused by cisplatin and maintains gut homeostasis.

D: -Amino acids are now recognized to be widely present in mammals. In rats, exogenously administered D: -methionine is almost converted into the L: -enantiomer via 2-oxo-4-methylthiobutylic acid as an intermediate. D: -Amino acid oxidase is associated with conversion of D: -methionine into the 2-oxo acid. Since D: -amino acid oxidase is present at the highest activity in the kidney compared to other organ, kidney injury is suggested to cause accumulation of D: -methionine. The purpose of the present study is to assess the role of kidney in the elimination of D: -methionine and metabolic conversion into L: -methionine in rats using a stable isotope methodology. After a bolus i.v. administration of D: -[²H₃)]methionine to 5/6-nephrectomized rats, plasma concentrations of D: -[²H₃]methionine, L: -[²H₃]methionine, and endogenous L: -methionine were determined by a stereoselective GC-MS method. Renal mass reduction slowed down the elimination of D: -[²H₃]methionine. The clearance values of conversion of D: -[²H₃]methionine into the L: -enantiomer in 5/6-nephrectomized rats were one-sixth of those in sham-operated rats. The elimination behavior of D: -[²H₃]methionine observed in rats demonstrated that kidney was the principal organ responsible for chiral inversion of D: -methionine.

Creatine serves as an energy-storing molecule in muscle, and in mammals it can be synthesized in the liver from guanidinoacetic acid (GAA). With this study, we evaluated whether GAA supplementation would lead to creatine production in cattle similarly to other species. Because the synthesis of creatine from GAA requires the use of a methyl group, we also evaluated the effect of supplementing methionine, as a methyl group donor, on the synthesis of creatine. Supplemental GAA did increase plasma concentrations of creatine. Also, blood concentrations of arginine, a precursor to GAA, were increased by GAA supplementation, suggesting that arginine use for GAA synthesis was spared by GAA provision. Plasma homocysteine, a marker that is inversely related to methyl group status, was not affected by GAA supplementation when heifers received 12 g/d methionine; however, it was increased by 30 or 40 grams per day of GAA supplementation when methionine was not supplemented. Results suggest that post-ruminal GAA supplementation increases creatine supply to cattle and spares arginine utilization. Moreover, GAA supplementation induced a methyl group deficiency that was resolved with methionine supplementation.

We have previously reported rescue from noise-induced auditory brainstem response (ABR) threshold shifts with d -methionine ( d -met) administration 1 h after noise exposure. The present study investigated further d -met rescue intervals at 3, 5 and 7 h post-noise exposure. Chinchillas laniger were exposed to a 6 h 105 dB sound pressure level (dB SPL) octave band noise (OBN) and then administered d -met i.p. starting 3, 5, or 7 h after noise exposure; controls received saline i.p. immediately after noise exposure. ABR assessments were performed at baseline and on post-exposure days 1 and 21. Outer hair cell (OHC) loss was measured in cochleae obtained at sacrifice 21 days post-exposure. Administration of d -met starting at any of the delay times of 3–7 h post-noise exposure significantly reduced day 21 ABR threshold shift at 2 and 4 kHz and OHC loss at all hair cell regions measured (2, 4, 6 and 8 kHz). ABR threshold shifts in the control group at 6 and 8 kHz were only 8 and 11 dB respectively allowing little opportunity to observe protection at those 2 frequencies.

In this study, the synthesis of template free zeolite Y and its recrystallization to two types of pure zeolite P and analcime in the presence of the amino acid d-methionine as structure-directing agent were investigated. The recrystallization occurred solely when specific heating cycles were applyed. A completely crystallized phase of zeolite Y for the mixture of zeolite P and analcime was observed in the presence of d-methionine at a concentration of 0.015 m . The effect of different Si/Al ratios (2.3–9.3), crystallization temperatures (40–160 °C), and crystallization times (28–96 hours) on the achievement of two different zeolite types were studied as well. Pure zeolite P was obtained during conventional heating to 100 °C for 42 hours, whereas pure analcime zeolite was achieved by heating the mixture to 160 °C for 96 hours. The products were characterized by X-ray diffraction, scanning electron microscopy, and IR spectroscopy.

Two rat growth assays were conducted using chemically defined diets to determine the efficacy of D-methionine (MET) relative to L-MET. Experiment 1 established the linear growth response region for weanling rats fed a MET-free diet supplemented with graded levels of L-MET. Growth was linear when rats were fed L-MET levels between 0.10 and 0.25%. In experiment 2, the efficacy of D-MET was determined using the slope-ratio technique. Graded levels of D- and L-MET were fed to weanling rats, resulting in growth in the linear portion of the growth curve as established in experiment 1. Efficacy of D-MET was 88.5% of L-MET. Evaluation of urinary MET excretion revealed that only about 0.1% of the D-MET ingested was excreted via the kidneys.

The effects of a D-methionine-containing solution (DMCS) on the nutritional status of AH109A hepatoma-bearing rats receiving total parenteral nutrition were studied. The DMCS solution inhibited the decrease of transferrin in the plasma of tumor-bearing rats when compared with the effect of an L-methionine-containing solution. The survival time was also significantly prolonged in the DMCS-treated rats. These results indicate that DMCS had a beneficial effect on the malnutrition induced in tumor-bearing rats and would be a useful amino acid solution for the nutritional support of cancer patients.

The effects of a nutrition therapy with D-methionine (Met)-containing solution were investigated in cell cultures of the AH109A cell line. The growth of AH109A hepatoma cells in culture media with D-Met-supplemented medium, L-Met-supplemented medium (control) and Met-free medium was compared. The D-Met-supplemented medium inhibited the cell growth to an extent similar to that manifested in the Met-free medium. The total free amino acid concentrations in the control medium decreased by approximately 40% on day 6 post-culture. However, the free amino acid concentrations in D-Met-supplemented and Met-free media did not change. Furthermore, alanine, which was not added to RPMI- 1640, was detected in the control medium on day 6 post-culture. These results suggest the possibility of application of D-Met-containing solution to cancer patients receiving total parenteral nutrition.

In the last few years we developed in our laboratory chromatographic methods for the chiral discrimination of amino acids, which allow to study the occurrence and the role of D-amino acids in nature. In the present paper we show that a methionine-auxotroph the eukaryotic yeast Kluyveromices lactis CBS 2359/152 is able to utilize D-methionine. Feeding yeast cells with either L-or D-methionine, we determined either enantiomer in the medium and inside the cells. We were able to demonstrate that D-methionine is uptaken and converted to the L-enantiomer.

We started from 2(R)-hydroxy-4-(methylthio)butanoic acid ((R)-1), which was prepared from D-methionine or, more efficiently, by a novel lipase hydrolysis of racemic ethyl 2-hydroxy-4-(methylthio)butyrate (rac-2)

Methods of preventing or reducing hearing or balance loss and damage to ear cells in patients who have been exposed to toxic levels of noise are provided. These methods comprise administering an effective amount of a methionine protective agent, such as D-methionine, prior to, simultaneously with, or subsequently to exposure to noise. Combinations of these time periods can also be employed.

Metabolic pathways of l - and d -methionine-methyl- 14 C have been studied in a wide range of mosses. The natural l -isomer is metabolized by a deamination reaction in all the Bryophyta, whereas the unnatural d -isomer follows either a deamination pathway or conjugation pathway with acetic acid and with malonic acid, respectively. The phytochemical relationship of Bryophyta with lower and higher plants based on the different d -methionine metabolic pathways is discussed.

Total sulfur-containing amino acids have been found to be the first limiting amino acid in several foods in comparison with human amino acid requirements. Addition of methionine in appropriate amounts to these foods might be expected to improve protein value. Economically, DL-methionine would be preferable to L-methionine for this purpose. However, the comparative tuilization of L- DL-, and D-methionine is unclear. The objective of the current project was to compare the effectiveness of L-, DL-, and D-methionine supplementation of diets based on a food product known to be low in methionine value for human subjects. "Instant" oatmeal was fed to adult subjects to provide 4.0 g of nitrogen/day. In randomly arranged periods, these diets were supplemented with L-, DL-, or D-methionine at two levels (0.58 and 1.16 g of methionine/day). An unsupplemented diet was used in a control period. Diets were adequate in vitamins, minerals, and energy. Mean nitrogen balances of subjects while receiving the L-methionine supplements at the 0.58 and 1.16 g levels were minus0.10 and +0.06 g of nitrogen, respectively. At similar levels of DL-methionine supplementation, nitrogen balances were minus0.12 and minus0.15 g of nitrogen, respectively, and minus0.24 and minus0.18 g of nitrogen with D-methionine supplementation. The mean nitrogen balance when no supplement was used was minus0.22 g of nitrogen. Thus, D-methionine is seemingly poorly utilized by the human. Urinary methionine excretion data supported these results.

D-Methionine, present in some parenteral solutions, is poorly utilized by man. To evaluate some of the factors affecting utilization, methionine isomer excretion was measured in rats treated with two different parenteral regimens: total parenteral nutrition and protein sparing therapy. Within each regimen, nutrient solutions differing only in methionine isomer composition were compared. Eight rats on the total parenteral nutrition regimen were infused with a 33% glucose--2.8% amino acid solution at a rate providing 100% of energy requirement. Four rats received the parenteral sulution containing L-methionine, and four the solution containing DL-methionine. Eight additional rats on a protein sparing regimen were infused with an amino acid solution (8.5%) at a rate to provide 25% of energy requirement. Four rats were infused with a solution containing L-methionine, and four with a solution containing DL-methionine. Total methionine content of livers was not affected by differences in methionine isomer. Infusion of the solution containing DL-methionine significantly increased plasma methionine levels during protein sparing therapy, with the increase representing accumulation of the D-isomer. Rats receiving protein sparing therapy had significantly higher liver methionine levels than rats receiving total parenteral nutrition. Although rats infused with the solution containing DL-methionine had elevated plasma methionine levels during protein sparing therapy, urinary methionine losses were small, as were losses of methionine sulfoxide and alpha-keto-gamma-methiolbutyrate. In contrast to humans, adult rats utilized more than 99% of parenterally administered D- or L-methionine.

N-Acyl-methionine derivatives have been proposed as replacements for methionine in supplementing food products low in this amino acid. We studied the effects of N-acetyl-L-methionine, N-acetyl-D-methionine and L-methionine loads (2 mmol/kg body weight) on portal and vena caval plasma amino acid concentrations in young pigs (n = 4). L-Methionine loading significantly increased mean (+/- SD) portal and vena caval plasma methionine concentrations from baseline values of 6.44 +/- 1.03 and 6.63 +/- 0.99 mumol/100 ml, respectively, to mean peak values of 340 +/- 75.0 and 265 +/- 49.8 mumol/100 ml, respectively. N-Acetyl-L-methionine loading increased mean peak portal and vena caval plasma methionine concentrations to 291 +/- 85 and 220 +/- 51.6 mumol/100 ml, respectively. N-Acetyl-L-methionine could not be detected in either portal or vena caval plasma. In contrast, N-acetyl-D-methionine loading produced only a small rise in mean peak portal and vena caval plasma methionine concentrations (13.0 +/- 4.31 and 8.62 +/- 1.71 mumol/100 ml, respectively). Concentrations of N-acetyl-D-methionine increased from baseline values of 0 mumol/100 ml to mean peak values of 251 +/- 32.0 and 234 +/- 72.3 mumol/100 ml, respectively, in portal and vena caval plasma. These data explain the poor utilization of N-acetyl-D-methionine as a methionine source.

Utilization of intravenously administered D-methionine was measured by morbidly obese subjects fed parenterally after elective gastric bypass surgery. Five patients were infused with a 25% glucose--4.25% amino acid solution containing DL-methionine, and four were treated with a 25% glucose--3.5% amino acid solution containing only L-methionine. Mean (+/- SD) total daily methionine excretion was 0.06 +/- 0.04 mmoles (of 28 +/- 4 mmoles infused) in patients treated with the L-methionine containing solution, and was 15.2 +/- 4.2 mmoles/day (of 45.2 +/- 5 mmoles DL-isomer infused) in patients treated with the DL-methionine containing solution. In these latter patients, 90 to 98% of the excreted methionine was the D-isomer. The data indicate 64 +/- 23% of infused D-methionine is excreted in the urine. Four patients excreted between 70 to 85% of infused D-methionine in the urine, but one patient excreted only 35 to 55%, suggesting better utilization. Plasma methionine levels were higher (9.9 +/- 1.9 mumoles/100 ml) in patients infused with solutions containing DL-methionine than those infused with the L-methionine solution (4.5 +/- 1.0 mumoles/100 ml). In the former case, 49% of plasma methionine was the D-isomer. The data indicate poor D-methionine utilization by postsurgical patients during total parenteral nutrition when given as DL-methionine in the presence of other amino acids and glucose.

IT HAS been reported by Gordon and Sizer (1955) that chickens do not utilize d -methionine as completely as l -methionine, and it was postulated that this is because d -methionine is metabolized primarily in the kidney tissue, and is partially lost by excretion. This view would appear to contradict the work of Fell et al. (1959) and Leveille et al. (1960) showing that the isomers of methionine are equivalent in the chicken as judged by both nutritional response and nitrogen retention, and of course by the original demonstration of the equal utilization of the optical isomers of methionine in the chick by Grau and Almquist (1943). Perhaps this apparent discrepancy is explicable in terms of an overloading of the capacity of the chick to transform d -amino acids to useful metabolites, similar to the effect demonstrated by Wretlind (1952) in rats. In that work, the isomers of methionine were found to be equivalent …

R. meliloti strains 107-1, 111 and 152 were adapted to D-methionine in three ways: a) consecutive transfer in the presence of increasing amounts of D-methionine, b) alternate transfer between D- and L-methionine-containing media followed by final cultivation in the presence of each isomer, c) alternate transfer between D-methionine and medium 79 followed by cultivation in medium 79 or in D-methionine-medium. At the end of the experiment efficiency of the strains was ascertained by a plant test.

Unlike other essential amino acids, l -methionine is not quantitatively assimilated by Streptococcus faecalis 9790. The present evidence indicates that when the organism grows in the presence of growth-limiting concentrations of l -methionine, approximately one molecule of five is metabolically converted to extracellular d -methionine. Through a non-metabolic process catalyzed by components of the medium, a significant fraction of this extracellular methionine undergoes oxidation to sulfoxide.

1. We obtained an unsymmetrical complexing sorbent containing D-methionine, which was attached to the macroreticulate polystyrene skeleton at theα-amino group. 2. The potentialities of using the obtained sorbent for the resolution of racemates were demonstrated.

Rats and chickens, unlike man, utilize D-methionine efficiently. We have studied urinary excretion of methionine isomers in young miniature pigs, adult rabbits, and adult dogs given D-methionine in an attempt to find an animal model that, like man, utilizes the D-isomer poorly. Six-week-old miniature pigs ingesting a protein-free diet were infused with 8.5% amino acid solutions differing only in methionine isomer content (L- vs DL-) to supply amino acid requirements. Each solution was infused for a 2- or 3-day period in a cross-over design. Plasma methionine levels were significantly higher (p = 0.01) during infusion of the solution providing DL-methionine, with 25% of total plasma methionine present as the D-configuration. However, urinary methionine excretion was similar with both solutions, with D-methionine utilization calculated as greater than 99%. Adult rabbits ingesting DL-methionine (0.14 g/100 g food) showed good utilization of D-methionine, excreting less than 1.3% D-isomer in the urine. Mixed breed dogs given 1.25 g D-methionine in their drinking water excreted less than 0.4% of ingested D-methionine in the urine. These data indicate that the pig, rabbit, and dog utilize D-methionine efficiently, behaving like the rat and chicken rather than man.