Leucine

The process of dark-induced senescence in plants is relatively poorly understood, but a functional electron-transfer flavoprotein/electron-transfer flavoprotein:ubiquinone oxidoreductase (ETF/ETFQO) complex, which supports respiration during carbon starvation, has recently been identified. Here, we studied the responses of Arabidopsis thaliana mutants deficient in the expression of isovaleryl-CoA dehydrogenase and 2-hydroxyglutarate dehydrogenase to extended darkness and other environmental stresses. Evaluations of the mutant phenotypes following carbon starvation induced by extended darkness identify similarities to those exhibited by mutants of the ETF/ETFQO complex. Metabolic profiling and isotope tracer experimentation revealed that isovaleryl-CoA dehydrogenase is involved in degradation of the branched-chain amino acids, phytol, and Lys, while 2-hydroxyglutarate dehydrogenase is involved exclusively in Lys degradation. These results suggest that isovaleryl-CoA dehydrogenase is ...

There is evidence that changes in branched-chain amino acid (BCAA) levels may correlate with the efficacy of therapeutic interventions for affecting improvement in metabolic control. The objective of this study was to evaluate whether serum concentrations of BCAAs (leucine, isoleucine, valine) could mediate in insulin sensitivity and glucose tolerance after continuous positive airway pressure (CPAP) treatment in patients with obstructive sleep apnea (OSA). A prospective randomized controlled trial of OSA patients with morbid obesity was conducted. Eighty patients were randomized into two groups: 38 received conservative treatment and 42 received CPAP treatment for 12 weeks. Plasma levels of BCAA, glucose tolerance and insulin resistance were evaluated at baseline and after treatment. After treatment, significant decreases of leucine levels were observed in both groups when compared with baseline levels (P < 0.005). With respect to patients with normal glucose tolerance (NGT), pat...

All patients were assessed clinically at Agia Sofia Hospital in Athens. They belonged to three unrelated families from different regions of Greece. Their parents were healthy and nonconsanguineous. All pregnancies and perinatal periods were uneventful. Their ...

... VIROLOGY 71, 134-142 (1976) Cellular Pools of Viral Proteins in 3T3 Cells Chronically Infected with Moloney-Murine Leukemia Virus JES FORCHHAMMER, BJ RN A ... NOMUBA, S., FISCHINGER, PJ, MATTERN, CFT, PEEPLES, PT, BASSIN, RH, and FRIEDMAN, GP (1972). ...

The unimolecular chemistry of [Cu(II)AA(AA – H)]+ complexes, composed of an intact and a deprotonated amino acid (AA) ligand, have been probed in the gas phase by tandem and multistage mass spectrometry in an electrospray ionization quadrupole ion trap mass spectrometer. The amino acids examined include Gly, Ala, Val, Leu, Ile, t-Leu and Phe. Upon collisionally-activated dissociation (CAD), the [Cu(II)AA(AA – H)]+ complexes undergo decarboxylation with simultaneous reduction of Cu(II) to Cu(I); during this process, a radical site is created at the α-carbon of the decarboxylated ligand (H2N1 – •CαH – CβH2 – R; R = side chain substituent). The radical site is able to move along the backbone of the decarboxylated amino acid to form two new radicals (HN1• – CαH2 – CβH2–R and H2N1 – CαH2 – •CβH – R). From the complexes of Gly and t-Leu, only Cα and N1 radicals can be formed. The whole radical ligand can be lost to form [Cu(I)AA]+ from these three isomeric radicals. Alternatively, further...

Protein intake is essential to maximally stimulate muscle protein synthesis, and the amino acid leucine seems to possess a superior effect on muscle protein synthesis compared to other amino acids. Native whey has higher leucine content and thus a potentially greater anabolic effect on muscle than regular whey (WPC-80). This study compared the acute anabolic effects of ingesting 2 × 20 g of native whey protein, WPC-80 or milk protein after a resistance exercise session. 24 young resistance trained men and women took part in this double blind, randomized, partial crossover, controlled study. Participants received either WPC-80 and native whey ( = 10), in a crossover design, or milk ( = 12). Supplements were ingested immediately (20 g) and two hours after (20 g) a bout of heavy-load lower body resistance exercise. Blood samples and muscle biopsies were collected to measure plasma concentrations of amino acids by gas-chromatography mass spectrometry, muscle phosphorylation of p70S6K, 4...

Background: The “leucine trigger” hypothesis was originally conceived to explain the post-prandial regulation of muscle protein synthesis (MPS). This hypothesis implicates the magnitude (amplitude and rate) of post-prandial increase in blood leucine concentrations for regulation of the magnitude of MPS response to an ingested protein source. Recent evidence from experimental studies has challenged this theory, with reports of a disconnect between blood leucine concentration profiles and post-prandial rates of MPS in response to protein ingestion.

Aim: The primary aim of this systematic review was to qualitatively evaluate the leucine trigger hypothesis to explain the post-prandial regulation of MPS in response to ingested protein at rest and post-exercise in young and older adults. We hypothesized that experimental support for the leucine trigger hypothesis will depend on age, exercise status (rest vs. post-exercise), and type of ingested protein (i.e., isolated proteins vs. protein-rich whole food sources).

Methods: This qualitative systematic review extracted data from studies that combined measurements of post-prandial blood leucine concentrations and rates of MPS following ingested protein at rest and following exercise in young and older adults. Data relating to blood leucine concentration profiles and post-prandial MPS rates were extracted from all studies, and reported as providing sufficient or insufficient evidence for the leucine trigger hypothesis.

Results: Overall, 16 of the 29 eligible studies provided sufficient evidence to support the leucine trigger hypothesis for explaining divergent post-prandial rates of MPS in response to different ingested protein sources. Of these 16 studies, 13 were conducted in older adults (eight of which conducted measurements post-exercise) and 14 studies included the administration of isolated proteins.

Conclusion: This systematic review underscores the merits of the leucine trigger hypothesis for the explanation of the regulation of MPS. However, our data indicate that the leucine trigger hypothesis confers most application in regulating the post-prandial response of MPS to ingested proteins in older adults. Consistent with our hypothesis, we provide data to support the idea that the leucine trigger hypothesis is more relevant within the context of ingesting isolated protein sources rather than protein-rich whole foods. Future mechanistic studies are warranted to understand the complex series of modulatory factors beyond blood leucine concentration profiles within a food matrix that regulate post-prandial rates of MPS.

Leucine tracer has been widely used for examining whole-body protein turnover in humans, but has not been evaluated as an indicator to be used in the indicator amino acid oxidation (IAAO) method. The goal of this study was to determine whether the L-[1-(13C)]leucine isotope is an acceptable indicator by comparing it with an established tracer, L-[1-(13C)]lysine. Healthy men (n = 7; 29.9 +/- 4.8 y old) were fed in random order a diet with 7 graded intakes of phenylalanine without tyrosine. In the first study (n = 5), subjects were administered an excess leucine intake of 65 mg/(kg.d), and in the second study (n = 5), they were given the mean requirement of 45 mg/(kg.d) to determine whether leucine intake affected the pattern of response. Previous IAAO studies using lysine and phenylalanine demonstrated a clear pattern in 13CO2 production, i.e., increasing test amino acid intake resulted in a linear decrease to plateau, with a readily discernable breakpoint indicating the requirement....

Dysregulated anabolic responses to nutrition/exercise may contribute to sarcopenia; however, these characteristics are poorly defined in female populations. We determined the effects of two-feeding regimes in older women (66±2.5y N=8/group): bolus-whey protein (WP-20 g) or novel low-dose leucine-enriched essential amino acids (EAA) (LEAA-3g [40% leucine]). Using (13)C6-Phenylalanine infusions, we quantified muscle (MPS) and albumin (APS) protein synthesis at baseline and both in response to feeding (FED) and feeding-plus-exercise (FED-EX; RE: 6×8 knee-extensions at 75%-1RM). We also quantified plasma insulin/AA concentrations, whole-leg (LBF)/muscle microvascular blood-flow (MBF), and muscle anabolic signaling by phospho-immunoblotting. Plasma insulinemia and EAA-aemia were markedly greater after WP than LEAA (P<0.001). Neither LEAA nor WP modified LBF in response to FED or FED-EX, while MBF increased to a similar extent in both groups, only after FED-EX (P<0.05). In response ...

Adsorption of colicin B to a sensitive strain of Escherichia coli results in rapid cessation of deoxyribonucleic acid, ribonucleic acid, and protein synthesis. Some classes of mutants insensitive to colicin B hyperexcrete a colicin inhibitor into their growth medium. This inhibitor functions by preventing adsorption of colicin B and does not rescue cells to which colicin has already adsorbed. The inhibitor is insensitive to nucleases, proteolytic enzymes, and lysozyme and is not extracted into organic solvents. The inhibitory material has a low molecular weight, which rules out identification as lipopolysaccharide, although purified lipopolysaccharide has some inhibitory activity. Evidence is presented that the inhibitor is enterochelin, an iron chelator which is the cyclic trimer of 2,3-dihydroxybenzoylserine. Enterochelin does not inhibit colicin M, a colicin that is produced by many strains colicinogenic for colicin B.

The objective of the present study was to evaluate the antibacterial properties of a plant secondary metabolite - caffeine. Caffeine is present in over 100 plant species. Antibacterial activity of caffeine was examined against the following plant-pathogenic bacteria: Ralstonia solanacearum (Rsol), Clavibacter michiganesis subsp. sepedonicus (Cms), Dickeya solani (Dsol), Pectobacterium atrosepticum (Pba), Pectobacterium carotovorum subsp. carotovorum (Pcc), Pseudomonas syringae pv. tomato (Pst), and Xanthomonas campestris subsp. campestris (Xcc). MIC and MBC values ranged from 5 to 20 mM and from 43 to 100 mM, respectively. Caffeine increased the bacterial generation time of all tested species and caused changes in cell morphology. The influence of caffeine on the synthesis of DNA, RNA and proteins was investigated in cultures of plant pathogenic bacteria with labelled precursors: [(3)H]thymidine, [(3)H]uridine or (14)C leucine, respectively. RNA biosynthesis was more affected than D...

Background Bronchial fibroblasts contribute to airway remodelling, including airway wall fibrosis. Transforming growth factor (TGF)-β1 plays a major role in this process. We previously revealed the importance of the mevalonate cascade in the fibrotic response of human airway smooth muscle cells. We now investigate mevalonate cascade-associated signaling in TGFβ1-induced fibronectin expression by bronchial fibroblasts from non-asthmatic and asthmatic subjects. Methods We used simvastatin (1-15 μM) to inhibit 3-hydroxy-3-methlyglutaryl-coenzyme A (HMG-CoA) reductase which converts HMG-CoA to mevalonate. Selective inhibitors of geranylgeranyl transferase-1 (GGT1; GGTI-286, 10 μM) and farnesyl transferase (FT; FTI-277, 10 μM) were used to determine whether GGT1 and FT contribute to TGFβ1-induced fibronectin expression. In addition, we studied the effects of co-incubation with simvastatin and mevalonate (1 mM), geranylgeranylpyrophosphate (30 μM) or farnesylpyrophosphate (30 μM). Results...

We report the map-based cloning of the leaf rust resistance gene Lr21, previously mapped to a generich region at the distal end of chromosome arm 1DS of bread wheat (Triticum aestivum L.). Molecular cloning of Lr21 was facilitated by diploid/polyploid shuttle mapping strategy. Cloning of Lr21 was confirmed by genetic transformation and by a stably inherited resistance phenotype in transgenic plants. Lr21 spans 4318 bp and encodes a 1080-amino-acid protein containing a conserved nucleotide-binding site (NBS) domain, 13 imperfect leucine-rich repeats (LRRs), and a unique 151-amino-acid sequence missing from known NBS-LRR proteins at the N terminus. Fine-structure genetic analysis at the Lr21 locus detected a noncrossover (recombination without exchange of flanking markers) within a 1415-bp region resulting from either a gene conversion tract of at least 191 bp or a double crossover. The successful map-based cloning approach as demonstrated here now opens the door for cloning of many c...

We sought to determine if decrements in the mass of fat-free body mass (FFM) and other lean tissue compartments, and related changes in protein metabolism, are appropriate for weight loss in obese older women. Subjects were 14 healthy weight-stable obese (BMI ≥30 ...

A rapid procedure for the recovery of Saccharomyces cerevisiae auxotrophs was developed by exploiting the protection of these mutants from thymineless death when a required metabolite was withheld. The method can be used for thymidine 5'-monophosphate-requiring auxotrophs or wild-type strains blocked in de novo synthesis of thymidylate by folate antagonists.

To determine the effect of glucose availability on glutamine metabolism, glutamine kinetics were assessed under conditions of hyperglycemia resulting from 1) intravenous infusion of 7.5% dextrose in healthy adults and 2) insulin deficiency in young adults with insulin-dependent diabetes mellitus (IDDM). Eight healthy adults and five young adults with IDDM were studied in the postabsorptive state by use of a primed continuous infusion ofd-[U-14C]glucose,l-[5,5,5-2H3]leucine, andl-[3,4-13C]glutamine. Whether resulting from insulin deficiency or dextrose infusion, the rise in plasma glucose was associated with increased glucose turnover (23.5 ± 0.7 vs. 12.9 ± 0.3 μmol · kg−1 · min−1, P < 0.01 and 20.9 ± 2.5 vs. 12.8 ± 0.4 μmol · kg−1 · min−1, P = 0.03, in health and IDDM, respectively). In both cases, high blood glucose failed to alter glutamine appearance rate (Ra) into plasma [298 ± 9 vs. 312 ± 14 μmol · kg−1 · h−1, not significant (NS) and 309 ± 23 vs 296 ± 26 μmol · kg−1 · h−1, ...

The ability to discriminate and respond to chemical signals from the environment is an almost universal prerequisite for survival. Here, we report that the scaffold protein Scribble is essential for odor-guided behavior in Drosophila. Previously, we identified a P-element insert line with generalized sexually dimorphic smell impairment, smi97B. We found that the transposon in this line is located between the predicted promoter region and the transcription initiation site of scrib. A deficiency in this region, Df(3R)Tl-X, and two scrib null alleles fail to complement the smell-impaired phenotype of smi97B. Wild-type behavior is restored by precise excision of the P element, scrib mRNA levels correspond with mutant and wild-type phenotypes, and introduction of a full-length scrib transgene in the smi97B mutant rescues the olfactory deficit. Expression of Scrib is widespread in olfactory organs and the central nervous system. Finally, alternative splicing of scrib generates transcripts...

The intake of approximately 70 g of alcohol impairs liver protein metabolism in healthy humans. To establish the threshold at which alcohol impairs hepatic protein metabolism in humans we compared the effects of 500 mL of water (control study), 300 (28.4 g ethanol) or 750 mL (71 g ethanol) of table wine on hepatic protein metabolism in three groups of healthy nonalcoholic volunteers. Hepatic protein metabolism was estimated (L-[1-14C]leucine infusion) by measuring the fractional secretory rates of albumin and fibrinogen during the overnight postabsorptive state (basal) and the subsequent administration of water or two different amounts of wine (300 or 750 mL) given with a liquid glucose-lipid-amino acid meal. During the meal, water did not affect fibrinogen fractional secretory rate and increased albumin fractional secretory rate by approximately 50% (P < 0.01). The 300 mL of wine increased albumin secretory rate by only approximately 20% (P < 0.01 vs. basal, P < 0.04 vs. w...

Background: The ELAC2 gene has been proposed to be a prostate cancer susceptibility gene and is being referred to as HPC2, in part because three case–control studies suggested that two common polymorphisms (Ser217Leu and Ala541Thr) are associated with risk. However, four subsequent larger studies have not confirmed this association. In five of the seven total studies, subject selection was influenced by prostate-specific antigen (PSA) levels. We examined the association and possible effect of subject selection in a larger study and a meta-analysis. Methods: In a population-based study in Australia, 825 case patients and 732 control subjects were genotyped for the Ser217Leu and Ala541Thr polymorphisms of ELAC2. Odds ratios (ORs) for prostate cancer were estimated by unconditional logistic and polytomous regression. A meta-analysis was conducted combining our data with those from seven published studies. The association of genotype with the logarithm of plasma PSA levels in control su...

Previous investigations have shown the efficacy of right-(RCPL) and left-(LCPL) circularly polarized light in promoting the asymmetric photolysis of racemic organic substrates and producing measurable enantiomeric excesses (e.e.s) when photolysis is incomplete. Synchrotron radiation, polychromatic and having out-of-plane components which are elliptically and ultimately circularly polarized, has been suggested as a universal source of RCPL and LCPL on a cosmic scale. The more prevalent right-(REPL) and left-(LEPL) elliptically polarized components have never been investigated for similar capabilities. The present study, using a 212.8 nm laser beam to mimic the synchtrotron radiation, explores the potential of REPL and LEPL in this context and finds a qualitative trend indicating that each induces asymmetric photolysis in the same sense as RCPL and LCPL, but to a lesser degree.

We recently showed that parenteral administration of amino acids to premature infants immediately after birth is safe and results in a positive nitrogen balance and increased whole-body protein synthesis. However, we did not determine organ-specific effects; albumin, produced by the liver, is an important protein, but its concentration is often low in premature neonates during the first few days after birth. The objective of the study was to test the hypothesis that the fractional and absolute albumin synthesis rates would increase with the administration of amino acids after birth, even at low nonprotein energy intake. Premature infants (<1500 g birth weight), who were on ventilation, received from birth onward either glucose only (control group, n = 7) or glucose and 2.4 g amino acid kg(-1) d(-1) (intervention group, n = 8). On postnatal day 2, all infants received a primed continuous infusion of [1-(13)C]leucine, and mass spectrometry techniques were used to determine the inco...