Depletion of Branched-Chain Aminotransferase 2 (BCAT2) Enzyme Impairs Myoblast 3 Survival and Myotube Formation

Much is known about the positive effects of branched-chain amino acids (BCAA) in regulating muscle protein metabolism. Comparatively much less is known about the effects of these amino acids and their metabolites in regulating myotube formation. Using cultured myoblasts, we showed that although leucine is required for myotube formation, this requirement is easily met by α-ketoisocaproic acid, the ketoacid of leucine. We then demonstrated increases in the expression of the first two enzymes in the catabolism of the three BCAA, branched-chain amino transferase (BCAT2) and branched-chain α-ketoacid dehydrogenase (BCKD), with ~3× increase in BCKD protein expression (p < .05) during differentiation. Furthermore, depletion of BCAT2 abolished myoblast differentiation, as indicated by reduction in the levels of myosin heavy chain-1, troponin and myogenin. Supplementation of incubation medium with branched-chain α-ketoacids or related metabolites derivable from BCAT2 functions did not rescue the defects. However, co-depletion of BCKD kinase partially rescued the defects. Collectively, our data indicate a requirement for BCAA catabolism during myotube formation and that this requirement for BCAT2 likely goes beyond the need for this enzyme to generate the α-ketoacids of the BCAA.York University Librarie

Correlation Between Branched Chain Amino Acids to Tyrosine Ratio and Child Pugh Score in Liver Cirrhosis Patients

Background: The determination of branched chain amino acids (BCAA) to tyrosine ratio (BTR) was available in making differentiation of chronic hepatitis from liver cirrhosis, because there was a strong association between BTR and staging (fibrosis) scores. Branched chain amino acids to tyrosine ratio have a correlation with Fischer ratio and the examination is easier because it can be done by enzymatic assay. Materials and Methods: To evaluate the correlation between BTR and Child-Pugh score, we examined the amino gram of 52 liver cirrhosis patients consisted of 26 Child-Pugh A, 19 Child-Pugh B, and 7 Child-Pugh C. The examination of amino gram was done by High Pressure Liquid Chromatograph (HPLC) analyzer. Branched chain amino acids to tyrosine ratio were compared to Child-Pugh score, albumin, ammonia level, number connection test to Fischer ratio. Results: Significant differences in BTR among Child-Pugh A, B, C were observed (Child-Pugh A 7.75 + 1.2; Child Pugh B 6.0 + 1.23 and Child Pugh C 4.38 + 3.14 (p = 0.000)). Branched chain amino acids to tyrosine ratio had a weak correlation with albumin (r = 0.292; p = 0.036), ammonia level (r = 0.376; p = 0.006) and strong correlation with Fischer ratio (r = 0.818; p = 0.000). There was no significant correlation between BTR and number connection test. Conclusion: These results showed that the determination of the molar ratio of branched chain amino acids to tyrosine well reflected the severity of liver cirrhosis and it can be used as a substitute of Fischer ratio

C5H9N Isomers: Pointers to Possible Branched Chain Interstellar Molecules

The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the ISM and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will firmly establish this link. In the light of this, we have considered C5H9N isomeric group in which the next higher member of the alkyl cyanide and other branched chain isomers belong. High-level quantum chemical calculations have been employed in estimating accurate energies of these isomers. From the results, the only isomer of the group that has been astronomically searched, n-butyl cyanide is not the most stable isomer and therefore, which might explain why its search could only yield upper limits of its column density without a successful detection. Rather, the two most stable isomers of the group are the branched chain isomers, tert-butylnitrile and isobutyl cyanide. Based on the rotational constants of these isomers, it is found that the expected intensity of tert-butylnitrile is the maximum among this isomeric group. Thus, this is proposed as the most probable candidate for astronomical observation. A simple LTE (Local thermodynamic equilibrium) modelling has also been carried out to check the possibility of detecting tert-butyl cyanide in the millimetre-wave region.Comment: 16 pages, 1 figur

Linear Rheological Response of a Series of Densely Branched Brush Polymers

We have examined the linear rheological responses of a series of welldefined, dense, regularly branched brush polymers. These narrow molecular weight distribution brush polymers had polynorobornene backbones with degrees of polymerization (DP) of 200, 400, and 800 and polylactide side chains with molecular weight of 1.4 kDa, 4.4 kDa, and 8.7 kDa. The master curves for these brush polymers were obtained by time temperature superposition (TTS) of the dynamic moduli over the range from the glassy region to the terminal flow region. Similar to other long chain branched polymers, these densely branched brush polymers show a sequence of relaxation. Subsequent to the glassy relaxation, two different relaxation processes can be observed for samples with the high molecular weight (4.4 and 8.7 kDa) side chains, corresponding to the relaxation of the side chains and the brush polymer backbone. Influenced by the large volume fraction of high molecular weight side chains, these brush polymers are unentangled. The lowest plateau observed in the dynamic response is not the rubbery entanglement plateau but is instead associated with the steady state recoverable compliance. Side chain properties affect the rheological responses of these densely branched brush polymers and determine their glassy behaviors

Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide

The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Our astrochemical model indicates that both isomers are produced within or upon dust grain ice mantles through the addition of molecular radicals, albeit via differing reaction pathways. The production of iso-propyl cyanide appears to require the addition of a functional group to a non-terminal carbon in the chain. Its detection therefore bodes well for the presence in the ISM of amino acids, for which such side-chain structure is a key characteristic.Comment: This is the author's version of the work. It is posted here by permission of the AAAS for non-commercial use. The definitive version was published in Science 345, 1584 (2014), doi:10.1126/science.125667

Dual mechanism of brain injury and novel treatment strategy in maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited disorder of branched-chain amino acid metabolism presenting with lifethreatening cerebral oedema and dysmyelination in affected individuals. Treatment requires life-long dietary restriction and monitoring of branched-chain amino acids to avoid brain injury. Despite careful management, children commonly suffer metabolic decompensation in the context of catabolic stress associated with non-specific illness. The mechanisms underlying this decompensation and brain injury are poorly understood. Using recently developed mouse models of classic and intermediate maple syrup urine disease, we assessed biochemical, behavioural and neuropathological changes that occurred during encephalopathy in these mice. Here, we show that rapid brain leucine accumulation displaces other essential amino acids resulting in neurotransmitter depletion and disruption of normal brain growth and development. A novel approach of administering norleucine to heterozygous mothers of classic maple syrup urine disease pups reduced branched-chain amino acid accumulation in milk as well as blood and brain of these pups to enhance survival. Similarly, norleucine substantially delayed encephalopathy in intermediate maple syrup urine disease mice placed on a high protein diet that mimics the catabolic stress shown to cause encephalopathy in human maple syrup urine disease. Current findings suggest two converging mechanisms of brain injury in maple syrup urine disease including: (i) neurotransmitter deficiencies and growth restriction associated with branchedchain amino acid accumulation and (ii) energy deprivation through Krebs cycle disruption associated with branched-chain ketoacid accumulation. Both classic and intermediate models appear to be useful to study the mechanism of brain injury and potential treatment strategies for maple syrup urine disease. Norleucine should be further tested as a potential treatment to prevent encephalopathy in children with maple syrup urine disease during catabolic stress

Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluorinated alkylsulfonic and alkylcarboxylic acids

Organic carbon normalized soil and sediment-water partitioning (Koc) coefficients were estimated for all C1 through C8 perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acids (PFCA) congeners. The limited experimental Koc dataset for the straight chain C7 through C10 PFCAs and C8 and C10 PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning constants and used to predict Koc values for both branched and linear C1 through C8 isomers. All branched and linear congeners in this homologue range are expected to have Koc values&#x3e;1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase Koc values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in Koc values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimated Koc values from octanol-water partitioning constants suggests that equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes and warrants further study using other partitioning coefficients for which suitable experimental data is available

Creating and preserving multi-partite entanglement with spin chains

We show how multi-partite entanglement, such as of W-state form, can be created in branched spin chain systems. We also discuss the preservation of such entanglement, once created. The technique could be applied to actual spin chain systems, or to other physical systems such as strings of coupled quantum dots, molecules or atoms

Effect of branched-chain amino acid supplementation on the oxidized/reduced state of plasma albumin in rats with chronic liver disease

We examined whether continuous supplementation with branched-chain amino acids phosphorylates ribosomal protein S6, a downstream effector of mammalian target of rapamycin, and improves hypoalbuminemia of rats with chronic liver disease. Sprague-Dawley rats were fed a casein diet (control group) or a branched-chain amino acid-supplemented casein diet (branched-chain amino acid group) for 11 weeks with repeated injections of carbon tetrachloride. Throughout this experimental period, no significant difference in plasma albumin concentration was seen between groups. The percentage of reduced albumin within total plasma albumin gradually decreased in both control and branched-chain amino acid groups. After 11 weeks with supplementation, phosphorylation of ribosomal protein S6 was significantly increased in the liver of rats in the branched-chain amino acid group compared with the control group. Furthermore, the percentage of reduced albumin within total albumin was significantly higher in the branched-chain amino acid group than in the control group. These results indicate that continuous supplementation with branched-chain amino acids in rats with chronic liver disease induces phosphorylation of hepatic ribosomal protein S6 and attenuates decreases in the percentage of reduced albumin, although levels of plasma albumin are not increased

The Effect of Branched Chain Amino Acids and L-Ornithine L-Aspartate Combination as the Late Evening Snacks on Nutritional Status and Minimal Hepatic Encephalopathy in Liver Cirrhosis

Background:Minimal hepatic encephalopathy (MHE) in liver cirrhotic patients is critical manifestation of low grade hepatic encephalopaty (HE), is caused quality of life decrease and risk of deteriorating into distinct HE. The study was conducted to asses the effect of combination of branched-chain amino acids (BCAA) and L-ornithine L-aspartate (LOLA), which was given late evening, on nutritional status and degree of HE.Method: This single-blind randomized study was conducted on liver cirrhotic outpatients in hepatology clinic of Cipto Mangunkusumo Hospital period June 2011-June 2012. The study subjects were divided into two groups, group of late evening snack (LS) and day snack (DS). Each group was supplemented with combination of milk of BCAAs and LOLA (3.7 g/serving). Evaluation based on history, physical examination, laboratory tests and critical flicker frequency (CFF) was performed one month after the intervention. Data were statistically analyzed with SPSS 15.Results: Thirty-two patients whose the inclusion criteria were divided into 16 subjects for each group, LS and DS. After one month of the intervention, the average level of prealbumin for DS group was increased statistically significant (p &lt; 0.001), but not significant for LS group (p = 0.259). The increase of average body weight,mid-arm muscle circumference (MAMC) and CFF test result in both groups. There was no improvement on subject global assessment (SGA) score after one month intervention in both groups.Conclusion: This study proved that giving combination of BCAAs and LOLA may improve the condition of MHE, however for nutritional status can not be assessed