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Amino Acids (Journal)

Current research reports and chronological list of recent articles..




The international scientific journal Amino Acids publishes contributions from all fields of amino acid and protein research: analysis, separation, synthesis, biosynthesis, cross linking amino acids, racemization/enantiomers, modification of amino acids as phosphorylation, methylation, acetylation, glycosylation and nonenzymatic glycosylation, new roles for amino acids in physiology and pathophysiology, biology, amino acid analogues and derivatives, polyamines, radiated amino acids, peptides, stable isotopes and isotopes of amino acids. Applications in medicine, food chemistry, nutrition, gastroenterology, nephrology, neurochemistry, pharmacology, excitatory amino acids are just some of the topics covered.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

To search this web page for specific words type "Ctrl" + "F" on your keyboard (Command + "F" on a Mac). Then: type the word you are searching for in the window that pops up!

Additional research articles see Current Chemistry Research Articles. A magazine with similar content (amino acids) is:

 - Journal of Amino Acids (Hindawi).



Amino Acids (Journal) - Abstracts



Synthetic peptide-labelled micelles for active targeting of cells overexpressing EGF receptors

Abstract

The goal of nanomedicine is to transport drugs to pathological tissues, reducing side effects while increasing targeting and efficacy. Aggregates grafted by bioactive molecules act as the active targeting agents. Among bioactive molecules, peptides, which are able to recognize overexpressed receptors on cancer cell membranes, appear to be very promising. The aim of this study was to formulate analog peptide-labeled micelles enabled to potentially deliver highly hydrophobic drugs to cancer cells overexpressing epidermal growth factor (EGF) receptor (EGFR). The selected synthetic peptide sequences were anchored to a hydrophobic moiety, aiming to obtain amphiphilic peptide molecules. Mixed micelles were formulated with Pluronic® F127. These micelles were fully characterized by physico-chemical methods, estimating the critical micellar concentration (CMC) by fluorescence. Their sizes were established by dynamic light scattering (DLS) analysis. Then, micelles were also tested in vitro for their binding capacity to human hepatocellular carcinoma (HCC) cell lines overexpressing EGFR.


Datum: 25.06.2019


Components of the GABAergic signaling in the peripheral cholinergic synapses of vertebrates: a review

Abstract

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system. Since the 1970s, many studies have focused on the role of GABA in the mammalian peripheral nervous system, and particularly in the cholinergic synapses. In this review, we present current findings for the cholinergic neurons of vegetative ganglia as well as for the neurons innervating smooth and striated muscles. Synaptic contacts formed by these neurons contain GABA and the enzyme, glutamic acid decarboxylase, which catalyzes the synthesis of GABA from glutamate. Newly formed GABA is released in the cholinergic synapses and mostly all the peripheral cholinergic synaptic contacts contain iono- and metabotropic GABA receptors. Although the underlying molecular mechanism of the release is not well understood, still, it is speculated that GABA is released by a vesicular and/or non-vesicular way via reversal of the GABA transporter. We also review the signaling role of GABA in the peripheral cholinergic synapses by modulating acetylcholine release, but its exact physiological function remains to be elucidated.


Datum: 24.06.2019


Hydration of serine–metal cation complexes: implication for the role of water in the origin of homochirality on the Earth

Abstract

It may be taken for granted that the processes that occurred in water were of crucial importance for the origin of life. Therefore, it is quite likely that water was also important with respect to the origin of homochirality. Here, it is shown, using electrospray ionization mass spectrometry, that the efficiency of hydration of homochiral serine–metal cation complexes is different from that of heterochiral serine–metal cation complexes. The differences in the efficiency of hydration of homo and heterochiral metal cation–amino acid complexes could lead to the amplification of formation of homochiral peptides in water solution from which life emerged.


Datum: 20.06.2019


Synthesis, in vitro and cellular antioxidant activity evaluation of novel peptides derived from Saccharomyces cerevisiae protein hydrolysate: structure–function relationship

Abstract

The relationship between structure and function of primary antioxidant peptide, YR-10 (YGKPVAVPAR) was considered by synthesizing three analogues including YHR-10 (YGKHVAVHAR), GA-8 (GKPVAVPA) and PAR-3 (PAR). Antioxidant activity was determined through in vitro and cellular assays. Substitution of Pro with His in the structure of YR-10 led to significant (P < 0.05) higher ABTS radical scavenging and ferric reducing activity. Following in silico simulated gastrointestinal digestion, Tyr and Arg were omitted, respectively, from N and C-terminal positions and resulted in decreasing DPPH, ABTS radical scavenging, and ferric reducing activities. PAR-3 showed the best inhibitory activity on linoleic acid oxidation. Pretreatment of Caco-2 cells with YR-10, YHR-10, and GA-8 (1000 µM) before exposure to H2O2 (160 µM) resulted in 34.10%, 39.66% and 29.159% reduction in malondialdehyde and 53.52%, 17.02% and 24.71% reduction in protein carbonyl levels. The peptide pretreatment reduced catalase level in cells and PAR-3 exhibited the most protective effects on the viability of cells exposed to oxidative stress.


Datum: 17.06.2019


Epileptic seizures and oxidative stress in a mouse model over-expressing spermine oxidase

Abstract

Several studies have demonstrated high polyamine levels in brain diseases such as epilepsy. Epilepsy is the fourth most common neurological disorder and affects people of all ages. Excitotoxic stress has been associated with epilepsy and it is considered one of the main causes of neuronal degeneration and death. The transgenic mouse line Dach-SMOX, with CD1 background, specifically overexpressing spermine oxidase in brain cortex, has been proven to be highly susceptible to epileptic seizures and excitotoxic stress induced by kainic acid. In this study, we analysed the effect of spermine oxidase over-expression in a different epileptic model, pentylenetetrazole. Behavioural evaluations of transgenic mice compared to controls showed a higher susceptibility towards pentylentetrazole. High-performance liquid chromatography analysis of transgenic brain from treated mice revealed altered polyamine content. Immunoistochemical analysis indicated a rise of 8-oxo-7,8-dihydro-2′-deoxyguanosine, demonstrating an increase in oxidative damage, and an augmentation of system x c as a defence mechanism. This cascade of events can be initially linked to an increase in protein kinase C alpha, as shown by Western blot. This research points out the role of spermine oxidase, as a hydrogen peroxide producer, in the oxidative stress during epilepsy. Moreover, Dach-SMOX susceptibility demonstrated by two different epileptic models strongly indicates this transgenic mouse line as a potential animal model to study epilepsy.


Datum: 13.06.2019


Surfactin application for a short period (10/20 s) increases the surface wettability of sound dentin

Abstract

The aim of this study was to evaluate the effect of spreading the lipopeptide surfactin, for short time (10/20 s), on dentin wettability. Study groups were surfactin: 2.8; 1.4; 0.7; 0.35; and 0.175 mg/mL and a control group that received no treatment. Dentin discs (4 mm height) were prepared and polished with 600-grit SiC paper. Contact angle determinations were carried out after microbrush spreading of surfactin on dentin specimens for, respectively, 10 and 20 s. Excess liquid was removed, and after 60 s, the specimens were analyzed in a goniometer using the sessile drop method to measure the contact angle. Results were analyzed by two-way ANOVA (concentration × time) and t student, with α = 0.05. Lower contact angles were obtained for surfactin (0.7 mg/mL) spread for 10 s. However, no statistical difference was observed for surfactin (2.8 mg/mL) applied during 20 s. Higher contact angles were observed for surfactin (0.7 mg/mL) spread for 20 s. In conclusion, dentin wettability is dependent on spreading time and surfactin concentration.


Datum: 13.06.2019


Composition of polyamines and amino acids in plant-source foods for human consumption

Abstract

Dietary polyamines and amino acids (AAs) are crucial for human growth, development, reproduction, and health. However, the scientific literature shows large variations in polyamine and AA concentrations among major staple foods of plant origin, and there is a scarcity of information regarding their complete composition of AAs. To provide a much-needed database, we quantified polyamines, agmatine, and AAs in select plant-source foods. On the dry matter basis, total polyamines were most abundant in corn grains, followed by soybeans, sweet potatoes, pistachio nuts, potatoes, peanuts, wheat flour and white rice in descending order. Glutamine was the most abundant AA in pistachio nuts, wheat flour and white rice, arginine in peanuts, leucine in corn grains, glutamate in soybeans, and asparagine in potatoes and sweet potatoes. Glutamine was the second most abundant AA in corn grains, peanuts, potatoes, and soybeans, arginine in pistachio nuts, proline in wheat flour, and glutamate in sweet potatoes and white rice. Free AAs represented ≤ 3.1% of total AAs in corn grains, peanuts, pistachio nuts, soybeans, wheat flour and white rice, but 34.4% and 28.5% in potatoes and sweet potatoes, respectively. Asparagine accounted for 32.3%, 17.5%, and 19.4% of total free AAs in potatoes, sweet potatoes, and white rice, respectively. The content of histidine, glycine, lysine, tryptophan, methionine, cysteine, and threonine was relatively low in corn grains, potatoes, sweet potatoes, and white rice. All of the analyzed plant-source foods lacked taurine, creatine, carnosine and anserine (antioxidants that are abundant in meats and also present in milk), and contained little 4-hydroxyproline. Proper proportions of plant- and animal-source products are likely most desirable for optimizing human nutrition and health.


Datum: 13.06.2019


Investigation of the impact of PTMs on the protein backbone conformation

Abstract

Post-translational modifications (PTMs) are known to play a critical role in the regulation of protein functions. Their impact on protein structures and their link to disorder regions have already been spotted in the past decade. Nonetheless, the high diversity of PTM types and the multiple schemes of protein modifications (multiple PTMs, of different types, at different time, etc.) make difficult the direct confrontation of PTM annotations and protein structure data. Therefore, we analyzed the impact of the residue modifications on the protein structures at the local level. Thanks to a dedicated structure database, namely PTM-SD, a large screen of PTMs have been done and analyzed at local protein conformation levels using the structural alphabet protein blocks (PBs). We investigated the relation between PTMs and the backbone conformation of modified residues, of their local environment, and at the level of the complete protein structure. The two main PTM types (N-glycosylation and phosphorylation) have been studied in non-redundant datasets, and then four different proteins were focused, covering three types of PTMs: N-glycosylation in renin endopeptidase and liver carboxylesterase, phosphorylation in cyclin-dependent kinase 2 (CDK2), and methylation in actin. We observed that PTMs could either stabilize or destabilize the backbone structure, at a local and global scale, and that these effects depend on the PTM types.


Datum: 10.06.2019


Dietary supplementation with arginine and glutamic acid alters the expression of amino acid transporters in skeletal muscle of growing pigs

Abstract

Sixty Duroc × Large White × Landrace pigs with an average initial body weight (BW) of 77.1 ± 1.3 kg were selected to investigate the effects of dietary supplementation with arginine (Arg) and/or glutamic acid (Glu) on free amino acid (FAA) profiles, expression of AA transporters, and growth-related genes in skeletal muscle. The animals were randomly assigned to one of five treatment groups (basic diet, iso-nitrogenous, Arg, Glu, and Arg + Glu groups). The results showed that plasma Glu concentration was lowest in the Arg + Glu group and highest in the Glu group (P < 0.05). In the longissimus dorsi (LD) muscle, the concentrations of histidine, Arg, and taurine in the Arg + Glu group were higher, and the concentrations of 3-methylhistidine was lower, than in the basic diet group (P < 0.05). The mRNA levels of ASC amino acid transporter-2 (ASCT2), L-type AA transporter 1, and sodium-coupled neutral amino acid transporter 2 in the LD muscle, as well as the mRNA levels of ASCT2 and proton-assisted amino acid transporter in the biceps femoris (BF) muscle, were higher in the Arg + Glu group compared to the basic diet group (P < 0.05). The mRNA levels of the muscle-specific RING finger-1 and muscle atrophy F-box genes in the LD muscle were downregulated in the Glu and Arg + Glu groups compared to the basic diet group (P < 0.05). Collectively, these findings suggest that dietary supplementation with both Arg and Glu increases intramuscular FAA concentrations and decreases the mRNA levels of genes involved in protein degradation in skeletal muscle.


Datum: 07.06.2019


A high-affinity peptide substrate for G protein-coupled receptor kinase 2 (GRK2)

Abstract

We synthesized a previously identified β-tubulin-derived G protein-coupled receptor kinase 2 (GKR2) peptide (GR-11-1; DEMEFTEAESNMN) and its amino-terminal extension (GR-11-1-N; GEGMDEMEFTEAESNMN) and carboxyl-terminal extension (GR-11-1-C; DEMEFTEAESNMNDLVSEYQ) peptides with the aim of finding a high-affinity peptide substrate for GRK2. GR-11-1-C showed high affinity for GRK2, but very low affinity for GKR5. Its specificity and sensitivity for GKR2 were greater than those of GR-11-1 and GR-11-1-N. These findings should be useful in designing tools for probing GKR2-mediated intracellular signaling pathways, as well as GRK2-specific drugs.


Datum: 01.06.2019


A comprehensive toxicity evaluation of novel amino acid-modified magnetic ferrofluids for magnetic resonance imaging

Abstract

Stem cells have been widely exploited as remedial agents in regenerative medicine due to its tremendous potential in treatment of various debilitating diseases. In spite of this fact, there is need of a reliable, clinically applicable cell tracker for deciphering the homing and distribution of stem cells post-transplantation. Researchers have proposed the use of superparamagnetic magnetite (Fe3O4) nanoparticles for in vivo and in vitro tracking and imaging of stem cells. However, there is not much understanding of the chemical coatings on the nanoparticles, which is very important for the sustainability of stem cells in biological system. For any biomedical applications, the surface properties and the core structure of nanoparticles play a significant role. This study reports surface modification of magnetic Fe3O4 nanofluid with biocompatible amino acids viz., arginine and histidine to maintain colloidal stability at neutral pH, impart least disruption when encountered with the biological system and allow labeling with mesenchymal stem cells (MSCs). The size of amino acids-modified magnetic nanoferrofluid (AA@MNFs) was restricted to 15–25 nm for enhanced uptake in stem cells. In vitro cytotoxicity profile of stem cells labeled AA@MNFs was estimated using various assays like MTT, LDH and AO/EtBr followed by detailed pre-clinical toxicity assessment of AA@MNFs which illustrated least toxicity effects in major tissues of the animals. In vitro MRI scans of the stem cells labeled AA@MNFs confirmed the suitability of the reported ferrofluids for the use as MR contrast agents.


Datum: 01.06.2019


Asymmetric dimethylation and citrullination of proteinic arginine and homoarginine synthesis in human Helicobacter pylori infection

Abstract

The importance of l-arginine (Arg) and relatives, including l-homoarginine (hArg) and asymmetric dimethylarginine (ADMA), in humans infected with Helicobacter pylori (Hp) is little understood. ADMA is produced by asymmetric dimethylation of the guanidine group of Arg residues in certain proteins and is released by proteolysis. High concentrations of circulating free ADMA are considered a risk factor for morbidity and mortality in adults. This risk is considered to arise from the inhibition of the synthesis of nitric oxide (NO), which is a potent vasodilator and inhibitor of platelet aggregation. In the present study, we quantified by stable isotope dilution gas chromatography–mass spectrometry (GC–MS) the concentration of free (f) and total (t) ADMA, Arg, hArg, lysine (Lys) and the sum of citrulline (Cit) and ornithine (Orn) (6 M HCl, 20 h, 110 °C) in serum samples of apparently healthy elderly subjects (n = 27; age, 31–105 years) who were tested for Hp infection. Nine subjects (5 males, 4 females) were found to be Hp seropositive (Hp+) and 18 subjects (8 males, 9 females) were found to be Hp seronegative (Hp‒). Proteinic (p) concentrations were determined by difference. fADMA (0.493 ± 0.068 vs 0.466 ± 0.081 µM, P = 0.382), pADMA (113 ± 73 vs 76 ± 59 nM, P = 0.169) and tADMA (0.606 ± 0.126 vs 0.543 ± 0.121 µM, P = 0.280) serum concentrations were found not to differ between the Hp+ and Hp− subjects. Serum concentrations of fArg (162 ± 30 vs 177 ± 36 µM, P = 0.471), fhArg (1.600 ± 0.638 vs 1.831 ± 0.742 µM, P = 0.554), and fLys (388 ± 170 vs 395 ± 149 µM, P = 0.700) also did not differ statistically between Hp+ and Hp− subjects. tArg (12.4 ± 1.49 vs 13.0 ± 1.33 mM, P = 0.190), tLys (23.0 ± 2.65 vs. 23.9 ± 2.66 mM, P = 0.456) and tCit + Orn (2.53 ± 0.76 vs 2.63 ± 0.85 mM, P = 0.817) did not differ between Hp+and Hp‒ subjects as well. phArg concentration was close to the limit of quantitation of the method (Hp+: 30 ± 210 nM; Hp−: 42 ± 205 nM), suggesting that hArg is virtually absent in serum proteins of the investigated subjects. pCit + Orn did not differ between infected and non-infected subjects. Our study suggests that Hp infection is not associated with elevated asymmetric dimethylation and citrullination of Arg proteins present in the serum or with the hArg synthesis from free Arg in elderly subjects. However, asymmetric Arg dimethylation was found to correlate inversely with Arg citrullination in Hp− (r2 = 0.408, P = 0.004) but not in Hp+ (r2 = 0.065, P = 0.506), with Arg citrullination decreasing and Arg asymmetric dimethylation increasing with subjects’ age.


Datum: 01.06.2019


Distinct associations between plasma osteoprotegerin, homoarginine and asymmetric dimethylarginine in chronic kidney disease male patients with coronary artery disease

Abstract

High plasma osteoprotegerin (OPG) and asymmetric dimethylarginine (ADMA) and low homoarginine (hArg) predict adverse renal and cardiovascular (CV) outcomes. In patients with chronic kidney disease and stable coronary artery disease, plasma OPG correlated with hArg (r = − 0.37, P = 0.03) and the hArg/ADMA molar ratio (r = − 0.46, P = 0.009), which was maintained upon adjustment for renal function. Elevated OPG levels and decreased hArg/ADMA ratios independently predicted 4-year composite CV and renal endpoints (CV death or progression to dialysis). Thus, high OPG and low hArg/ADMA ratio, albeit interrelated, appear to independently contribute to adverse clinical outcome.


Datum: 01.06.2019


The self-disproportionation of enantiomers (SDE) of amino acids and their derivatives

Abstract

This review covers the phenomenon of the self-disproportionation of enantiomers (SDE) of amino acids and their derivatives in all its guises from phase transformations (recrystallization, sublimation, and distillation), to the application of force fields, through to chromatography including HPLC, MPLC, gravity-driven column chromatography, and SEC. The relevance of the SDE phenomenon to amino acid research and to marketed pharmaceuticals is clear given the potential for alteration of the enantiomeric excess of a portion of a scalemic sample. In addition, the possible contribution of the SDE phenomenon to the genesis of prebiotic homochirality is considered.


Datum: 01.06.2019


Glycine protects partial liver grafts from Kupffer cell-dependent ischemia–reperfusion injury without negative effect on regeneration

Abstract

Donor preconditioning with glycine prevents Kupffer cell-dependent reperfusion injury to liver grafts. Partial liver grafts need to regenerate and grow in size after transplantation; however, glycine inactivates Kupffer cells, which are important for hepatic regeneration. Thus, this study was designed to evaluate the impact of donor preconditioning with glycine after partial liver transplantation (pLTx). PLTx was performed in 28 female Sprague–Dawley rats. Glycine (1.5 ml, 300 mM; i.v.) was given to 14 live donors before organ procurement. Liver enzymes and histology were investigated 8 h after reperfusion to index liver injury and leukocyte infiltration. Hepatic microperfusion and leukocyte–endothelium interaction were assessed using the in vivo fluorescence microscopy method. Ki-67 and TNF-α were detected by immunohistochemistry for regeneration and Kupffer cell activation. Glycine significantly increased survival from 0% in controls to 40%, while both liver enzyme levels and necrosis were decreased to about 50% of controls (p < 0.05). Sinusoidal blood flow increased by 40–80%, while leukocyte–endothelium interaction decreased to 30% of control values (p < 0.05). While Kupffer cell-derived TNF-α decreased to 70% of controls, there was no difference between groups in Ki-67 expression. Data presented here clearly demonstrate that glycine protects partial liver grafts from reperfusion injury without effects on regeneration.


Datum: 01.06.2019


Diversity of advanced glycation end products in the bovine milk proteome

Abstract

Milk processing relies on thermal treatments warranting microbiologically safe products with extended shelf life. However, elevated temperatures favor also Maillard reactions yielding the structurally diverse advanced glycation end products (AGEs). AGEs may alter protein functions and immunogenicity and also decrease the nutritional value of milk products. Furthermore, dietary AGEs contribute to the circulating AGE pool with potentially harmful effects. Here, 14 types of protein-derived AGEs present in raw milk or produced during processing/storage of regular and lactose-free milk products were identified by nanoRP-UPLC-ESI–MS/MS. In total, 132 peptides (118 modification sites in 62 proteins) were modified by at least one studied AGE. Amide-AGEs were the most abundant group with formyllysine being the main type. Most lysine- and arginine-derived AGEs and their modification sites have not been reported before. The number of AGE modification sites increased with the harsher processing conditions of regular milk, but remained stable during storage. This was further supported by quantitative data.


Datum: 01.06.2019


Plasma ADMA, urinary ADMA excretion, and late mortality in renal transplant recipients

Abstract

Cardiovascular disease (CVD) is the leading cause of death in renal transplant recipients (RTR). Elevated plasma asymmetric dimethylarginine (pADMA), an endogenous nitric oxide synthase inhibitor produced from the turnover of methylated arginine moieties in proteins, is a risk factor for CVD and mortality. It is unknown how urinary ADMA excretion (uADMA), one of the main ADMA elimination routes, is associated with long-term survival. Furthermore, the association of pADMA and uADMA with markers for turnover of arginine-methylated proteins is unknown. We analyzed ADMA using a validated GC–MS/MS method in plasma and 24-h urine samples of 685 RTR, included ≥ 1 year after transplantation. We also analyzed urine symmetric dimethylarginine (uSDMA) using the same method. Urinary creatinine and urea excretions were used as markers for turnover of muscle protein and amino acids, respectively. We applied Cox regression analyses to study associations of pADMA, uADMA, and uSDMA with all-cause and CVD mortality. Mean pADMA was 0.61 ± 0.12 µM, uADMA was 31 ± 13 µmol/24 h, and uSDMA was 52 ± 19 µmol/24 h. Over median follow-up of 5.4 [4.9–6.1] years, 147 RTR died, of which 58 (39%) from CVD. High pADMA was associated with high all-cause mortality (HR per SD [95% CI]: 1.45 [1.26–1.67], P < 0.001), while high uADMA was associated with low all-cause and CVD mortality (HR per SD [95% CI]: 0.57 [0.47–0.69], P < 0.001, and 0.55 [0.40–0.74], P < 0.001, respectively). The associations were independent of adjustment for potential confounders. Creatinine excretion was associated with both pADMA (st. β:− 0.21, P = 0.003) and uADMA (st. β: 0.49, P < 0.001), and urea excretion was associated with uADMA (st. β: 0.56, P < 0.001). Associations of uSDMA with outcomes and with creatinine excretion and urea excretion were comparable to those of uADMA. The associations of pADMA, uADMA and uSDMA with mortality were strongly affected by adjustment for creatinine excretion and urea excretion. We found for the first time that high uADMA and high uSDMA are associated with less risk of all-cause and CVD mortality. The links of uADMA and uSDMA with markers of muscle protein and amino acid turnover may serve to further understand ADMA and SDMA homeostasis and their clinical implications.


Datum: 01.06.2019


Modelling of protein turnover provides insight for metabolic demands on those specific amino acids utilised at disproportionately faster rates than other amino acids

Abstract

The nitrogen balance is regulated by factors such as diet, physical activity, age, pathogenic challenges, and climatic conditions. A paradigm was developed from published recommended rates of protein intake (g/kg/day) with corresponding rates of endogenous protein turnover and excretion, to extrapolate amino acid balances under various conditions. The average proportions of amino acids in the ingested proteins representing a well-balanced diet were used to assess intake and an average human composition profile from five major high-turnover proteins in the body to assess endogenous protein turnover. The amino acid excretion profiles for urine and sweat were constructed for males and females from published data. The model calculated the nitrogen balances for a range of amino acids to determine the amino acid requirements to support daily exertion. Histidine, serine, glycine, and ornithine were in negative balances in males and females and this potential deficit was greater in the higher body-mass ranges. Conversely, leucine, isoleucine, and valine were conserved during nitrogen flux and resulted in positive balances. The model was run under a scenario of high demand for the synthesis of IgG during a response to an infectious challenge which indicated that these were increased requirements for tyrosine, threonine, and valine. It was concluded that these amino acids represent points of limitation to anabolic metabolism by restriction of their supply at critical times of demand. This would especially occur under conditions of fitness training, maintaining intensive exercise regimes, facilitating responses to pathogenic challenge, or recovery from injury.


Datum: 01.06.2019


Central, but not systemic, thermoregulatory effects of leptin are impaired in rats with obesity: interactions with GABA B agonist and antagonist

Abstract

Leptin is an adipokine that regulates body weight by decreasing appetite and increasing energy expenditure. Besides the effects on food intake, leptin can regulate energy expenditure at least in part by modulating thermogenesis. Many of the effects of leptin are attributable to action in the central nervous system, particularly in the hypothalamus. Common forms of obesity are associated with increased leptin levels and a failure to suppress feeding and mediate weight loss in response to exogenous leptin. This apparent leptin ineffectiveness defines a state of so-called leptin resistance. We examined the effect of leptin on core body temperature in rats with normal weight and diet-induced obesity (DIO), as well as thermoregulatory interactions between leptin and GABAB-agonist and an antagonist. We found that leptin retains the ability to induce hyperthermic effect in rats with DIO. Additionally, temperature responses produced by GABAB agonist and antagonist are altered in a state of obesity and by administration of leptin. We evaluated whether the medial preoptic area of the anterior hypothalamus (MPA) still remains sensitive to leptin action during DIO. Using extracellular recordings of neurons and phospho-signal transducer and the activator of transcription 3 (pSTAT3) immunohistochemistry, we have provided strong evidence that leptin signaling in the MPA is impaired in obese rats. We believe that leptin resistance in the MPA may play a role in the pathogenesis of obesity and obesity-related disease states.


Datum: 28.05.2019


Branched-chain amino acid catabolism of Thermoanaerobacter strain AK85 and the influence of culture conditions on branched-chain alcohol formation

Abstract

The bioprocessing of amino acids to branched-chain fatty acids and alcohols is described using Thermoanaerobacter strain AK85. The amino acid utilization profile was evaluated without an electron scavenger, with thiosulfate, and in a co-culture with a methanogen. There was an emphasis on the production of branched-chain alcohols and fatty acids from the branched-chain amino acids, particularly the influence of culture conditions which was investigated using isoleucine, which revealed that the concentration of thiosulfate was of great importance for the branched-chain alcohols/fatty acid ratio produced. Kinetic studies show that branched-chain amino acid fermentation is relatively slow as compared to glucose metabolism with the concentrations of the branched-chain alcohol increasing over time. To understand the flow of electrons and to investigate if the branched-chain fatty acid was being converted to branched-chain alcohol, enzyme assays and fermentation studies using 13C-labeled leucine and 3-methyl-1-butyrate were performed which indeed suggest that carboxylic acid reduction is a source of branched-chain alcohols when Thermoanaerobacter strain AK85 was cultivated with thiosulfate as an electron scavenger.


Datum: 27.05.2019


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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