Amino Acids L-leucine Research Articles

Formation of Key Aroma Compounds During 30 Weeks of Ripening in Gouda-Type Cheese Produced from Pasteurized and Raw Milk.

Gouda-type cheeses were produced on a pilot-scale from raw milk (RM-G) and pasteurized milk (PM-G). Sixteen key aroma compounds previously characterized by the sensomics approach were quantitated in the unripened cheeses and at five different ripening stages (4, 7, 11, 19, and 30 weeks) by means of stable isotope dilution assays. Different trends were observed in the formation of the key aroma compounds. Short-chain free fatty acids and ethyl butanoate as well as ethyl hexanoate continuously increased during ripening but to a greater extent in RM-G. Branched-chain fatty acids such as 3-methylbutanoic acid were also continuously formed and reached a 60-fold concentration after 30 weeks, in particular in PM-G. 3-Methylbutanal and butane-2,3-dione reached a maximum concentration after 7 weeks and decreased with longer ripening. Lactones were high in the unripened cheeses and increased only slightly during ripening. Recent results have shown that free amino acids were released during ripening. The aroma compounds 3-methylbutanal, 3-methyl-1-butanol, and 3-methylbutanoic acid are suggested to be formed by microbial enzymes degrading the amino acid l-leucine following the Ehrlich pathway. To gain insight into the quantitative formation of each of the three aroma compounds, the conversion of the labeled precursors (13C6)-l-leucine and (2H3)-2-keto-4-methylpentanoic acid into the isotopically labeled aroma compounds was studied. By applying the CAMOLA approach (defined mixture of labeled and unlabeled precursor), l-leucine was confirmed as the only precursor of the three aroma compounds in the cheese with the preferential formation of 3-methylbutanoic acid.

Volatile Organic Compounds (VOCs) Produced by Levilactobacillus brevis WLP672 Fermentation in Defined Media Supplemented with Different Amino Acids.

Fermentation by lactic acid bacteria (LAB) is a promising approach to meet the increasing demand for meat or dairy plant-based analogues with realistic flavours. However, a detailed understanding of the impact of the substrate, fermentation conditions, and bacterial strains on the volatile organic compounds (VOCs) produced during fermentation is lacking. As a first step, the current study used a defined medium (DM) supplemented with the amino acids L-leucine (Leu), L-isoleucine (Ile), L-phenylalanine (Phe), L-threonine (Thr), L-methionine (Met), or L-glutamic acid (Glu) separately or combined to determine their impact on the VOCs produced by Levilactobacillus brevis WLP672 (LB672). VOCs were measured using headspace solid-phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS). VOCs associated with the specific amino acids added included: benzaldehyde, phenylethyl alcohol, and benzyl alcohol with added Phe; methanethiol, methional, and dimethyl disulphide with added Met; 3-methyl butanol with added Leu; and 2-methyl butanol with added Ile. This research demonstrated that fermentation by LB672 of a DM supplemented with different amino acids separately or combined resulted in the formation of a range of dairy- and meat-related VOCs and provides information on how plant-based fermentations could be manipulated to generate desirable flavours.

The Quality of Lokan Rendang Oil Substitued Red Palm Oil Olein

Rendang is a typical Minangkabau cuisine in West Sumatra, which is usually made with beef and other protein resources such as Lokan, which contains amino acids L-leucine and L-isoleucine. It is made with coconut milk that produces oil during cooking. The oil can be substituted with Red Palm Oil Olein (RPOO), which contains nutrients essential for the body as antioxidants. This study aims to determine the effect of RPOO substitution in Lokan rendang on color properties, vitamin A content, antioxidant activity, and organoleptic. The experimental design in this research was a Completely Randomized Design (CRD) with one factor and five treatment levels. The treatment factor was RPOO substitution with 0, 25, 50, 75, and 100% Lokan rendang oil. The result showed that RPOO substitution significantly affected the antioxidant and organoleptic activity (taste, aroma, and overall) of rendang Lokan. The greater the substituted RPOO, the greater the vitamin A content in Lokan rendang.

Evaluation of amino acid L-leucine as a kinetic promoter for CO2 sequestration as hydrate: A kinetic and morphological study

Carbon capture and sequestration (CCS) are widely recognized as the most effective technology for reducing CO2 emissions and mitigating global climate change. Hydrate-based CO2 sequestration (HBCS) has emerged as a promising technology for long-term and stable CO2 storage. There are growing interests in employing hydrophobic amino acids to enhance CO2 hydrate formation kinetics recently. However, there is still a lack of understanding of how amino acids promote CO2 hydrate effectively. In this study, we systematically investigate an environmental-benign kinetic promoter (L-leucine, L-Leu) varying from 0.05 to 2.00 wt% to enhance CO2 hydrate formation at an initial pressure of 5.5 MPa and temperature of 275.2 K. The results show that varying L-Leu concentration has limited effect on tind. The kickoff concentration of L-Leu in promoting CO2 hydrate kinetics is 0.30 wt%. 2.00 wt% L-Leu yields the optimal CO2 gas uptake of 62.17 ± 0.78 mmol/mol with CO2 partition in the hydrate phase of 66 %. CO2 hydrate forms a layer at the gas-liquid interface and turns to be porous at CL-Leu above 0.30 wt% followed by a significant wall-climbing growth with rapid CO2 gas uptake. L-Leu precipitation occurs at CL-Leu above 1.00 wt% and leads to a decrease in final CO2 gas uptake in repeated experiments at CL-Leu = 2.00 wt%. A mechanism of L-Leu in promoting CO2 hydrate kinetics by adsorption on the surface at CL-Leu above 1.00 wt% is proposed. L-Leu is evaluated to be effective in improving CO2 hydrate kinetics. These findings provide insights for a novel environmental-benign CO2 hydrate kinetic promoter in HBCS application, which requires rapid CO2 hydrate formation and high CO2 gas uptake.

The Impact of Nutrition on Muscle Health in Older Individuals

The Impact of Nutrition on Muscle Health in Older Individuals Abstract: The age-related change in the importance of nutrition for muscle health starts at the age of 50. Considering its effects on the mobility and physical independence of older people, the aging of the musculoskeletal system represents one of the greatest public health challenges and tasks for a demographically aging Switzerland. In particular sarcopenia, a pathological decrease in muscle strength, muscle mass and muscle function beyond the physiological age-related changes, correlates with a significantly increased risk of falls as well as increasing morbidity and mortality. Common chronic diseases related to old age not only promote additional muscle loss but also frailty, leading to an additional decline of the quality of life. General practitioners play a crucial role in the initial assessment of changing life circumstances and activity profiles of older people. Thanks to their medical care over many years they are able to identify functional impairments of their aging patients at an early stage and address them in time. This is important because the combination of a high-protein diet and exercise may be extremely effective for improving muscle health and function. Eating more proteins (taking into account the newly revised and increased daily protein requirement for healthy seniors of 1,0-1,2g/kg body weight (bw)) can significantly slow down age-related muscle loss. Depending on age and comorbidities, the daily protein requirement might be even higher (1,5 to 2,0g/kg bw). According to current studies, a minimal protein amount of 25-35g per main dish is recommended for optimal muscle growth stimulation among older individiuals. Thanks to their highly potent boosting power on myofibrillar protein synthesis rates the amino acid L-leucine and L-leucine-rich foods play an important role in elderly people's diet.

Three unrelated chemoreceptors provide Pectobacterium atrosepticum with a broad-spectrum amino acid sensing capability.

Amino acids are important nutrients and also serve as signals for diverse signal transduction pathways. Bacteria use chemoreceptors to recognize amino acid attractants and to navigate their gradients. In Escherichia coli two likely paralogous chemoreceptors Tsr and Tar detect 9 amino acids, whereas in Pseudomonas aeruginosa the paralogous chemoreceptors PctA, PctB and PctC detect 18 amino acids. Here, we show that the phytobacterium Pectobacterium atrosepticum uses the three non-homologous chemoreceptors PacA, PacB and PacC to detect 19 proteinogenic and several non-proteinogenic amino acids. PacB recognizes 18 proteinogenic amino acids as well as 8 non-proteinogenic amino acids. PacB has a ligand preference for the three branched chain amino acids L-leucine, L-valine and L-isoleucine. PacA detects L-proline next to several quaternary amines. The third chemoreceptor, PacC, is an ortholog of E. coli Tsr and the only one of the 36 P. atrosepticum chemoreceptors that is encoded in the cluster of chemosensory pathway genes. Surprisingly, in contrast to Tsr, which primarily senses serine, PacC recognizes aspartate as the major chemoeffector but not serine. Our results demonstrate that bacteria use various strategies to sense a wide range of amino acids and that it takes more than one chemoreceptor to achieve this goal.

Improvement of solubility and dissolution rate of Biopharmaceutical Class II drug atorvastatin calcium by using an essential amino acid L-leucine

Background and objective: Atorvastatin calcium is an antihyperlipidemic agent that is characterized by low aqueous solubility and high membrane permeability. This study was designed to enhance the solubility and the dissolution rate of atorvastatin calcium in the water and physiological pH (pH 6.8) by using L-Leucine as solubilizing agent utilizing different solid dispersion methods. Methods: Solid dispersion masses were prepared by kneading method and solvent evaporation methods at different weight ratios (1:1, 1:2: and 1:4) of the drug to the carrier. Saturated solubility studies were carried out in aqueous media, and the in-vitro studies were performed in physiological pH Fourier transform infrared spectroscopy were used to detect any interaction between the drug and the carrier. Results: The kneading method increase the solubility of atorvastatin calcium by 1.27, 1.43, and 1.81 folds from kneading method 1, kneading method 2, and kneading method 3, respectively. The solubility of atorvastatin calcium in solvent evaporation 1, solvent evaporation 2, and solvent evaporation 4 was increased by 2.53, 2.66, and 3.1 folds (P = 0.002). Solvent evaporation 2 (1:2 ratio) was selected as the best formula in terms of dissolution profile because it has faster and complete drug release after 5 minutes when compared with solvent evaporation 1, kneading method 1, kneading method 2, and kneading method 3 and contain less amount of L-Leucine when compared with solvent evaporation 3. Fourier transform infrared studies indicated no chemical reaction between the drug and carrier. Conclusion: L-leucine significantly improved the solubility and dissolution profile of poorly water-soluble atorvastatin calcium.

A conserved strategy for inducing appendage regeneration in moon jellyfish, Drosophila, and mice.

Can limb regeneration be induced? Few have pursued this question, and an evolutionarily conserved strategy has yet to emerge. This study reports a strategy for inducing regenerative response in appendages, which works across three species that span the animal phylogeny. In Cnidaria, the frequency of appendage regeneration in the moon jellyfish Aurelia was increased by feeding with the amino acid L-leucine and the growth hormone insulin. In insects, the same strategy induced tibia regeneration in adult Drosophila. Finally, in mammals, L-leucine and sucrose administration induced digit regeneration in adult mice, including dramatically from mid-phalangeal amputation. The conserved effect of L-leucine and insulin/sugar suggests a key role for energetic parameters in regeneration induction. The simplicity by which nutrient supplementation can induce appendage regeneration provides a testable hypothesis across animals.

Performance of ion pairing chromatography and hydrophilic interaction liquid chromatography coupled to charged aerosol detection for the analysis of underivatized amino acids

The charged aerosol detector (CAD) is frequently employed in liquid chromatography for the analysis of small polar and ionizable compounds such as amino acids and amino sugars, which provide a weak chromophore only. Separation of these compounds is achieved by means of ion pair chromatography (IPC), and, more recently, hydrophilic interaction chromatography (HILIC) techniques. However, as the CAD's response is highly dependent on the mobile phase composition, the substantial differences in the mobile phase composition of IPC and HILIC have a distinct impact on the detector's performance. This study was aimed at systematically comparing the performance of IPC and HILIC when coupled to the CAD. Therefore, the separation techniques characterized by their specific mobile phase compositions were evaluated for their influence on the CAD response and the signal-to-noise ratio (S/N) of the amino acids L-alanine, L-leucine, and L-phenylalanine applying the response surface methodology (RSM). The RSM results derived from flow injection analysis (FIA) indicated that the CAD response and thus the obtainable S/N are significantly higher in HILIC compared to IPC where the S/N decreased with the chain length of the applied ion-pairing reagent. In addition, an IPC and a HILIC method, respectively, were developed for the impurity profiling of the branched-chain amino acids (BCAAs) L-leucine, L-isoleucine, and L-valine. The beneficial effects of the HILIC conditions on the S/N observed under FIA conditions were partly offset by moderate column bleed effects when using an amide functionalized column, which facilitates the separation in the HILIC method. Satisfactory LOQs (3-10 ng on column) were obtained with both methods; however, the HILIC method was found to be slightly superior in terms of sensitivity and separation efficiency.

Volumetric and acoustic properties of amino acids L-Leucine and L-Serine in aqueous solution of ammonium dihydrogen phosphate (ADP) at different temperatures and concentrations

The physicochemical properties of amino acids like L-Leucine and L-Serine in aqueous solution of ammonium dihydrogen Phosphate (ADP) at different temperature analysed by volumetric and acoustic methods. By using density data, apparent molar volume Vϕ, partial molar volume Vϕ0 and standard partial molar volume of transfer ΔVϕ0 have been evaluated. From speed of sound data, apparent molar isentropic compression Kϕ,s apparent partial molar isentropic compression Kϕ,s0 and partial molar isentropic compression of transfer ΔKϕ,so have been calculated. The pair and triplet interaction coefficient have also been calculated. The results have been interpreted in terms of solute–solute and solvent–solvent interactions.

Enhancement of the extra-fine particle fraction of levofloxacin embedded in excipient matrix formulations for dry powder inhaler using response surface methodology

Extra-fine particle fraction (eFPF, the fraction of particles with aerodynamic size <2 µm) is an essential metric to evaluate the deep lung delivery of dry powder inhalers (DPIs). The product of spray-drying has the potential to be applied in DPI formulations regarding its controllable size. This study performed an eFPF enhancement of levofloxacin DPI formulations by optimizing the spray-drying process parameters such as inlet temperature, feed flow rate, and gas flow rate, using a design space compiled from response surfaces. A polysaccharide, phytoglycogen, was used as an excipient matrix to prepare DPI formulations containing the antibiotic levofloxacin hydrate and the amino acid L-leucine.The aerodynamic-related properties and the percentage yield of spray-dried particles were evaluated as target outcomes. The influence of process variables on the product outcomes was also summarized. The most critical factor controlling inhalation properties was gas flow rate, owing to its significant contributions (p<0.05), which is coherent to most articles of engineering. A design space was plotted using response surfaces to optimize process parameters. The performance of the design space was evaluated. Most responses of the optimized runs were within the 95% prediction interval. The design space was adopted to successfully fabricate levofloxacin-containing deep lung delivery inhalable particles (eFPF >5%). The usefulness of the design space in another drug was also studied. The predicted design space may support future studies that aim to prepare composite particles with fair alveolar inhalation performance for DPI formulations using a hydrophilic macromolecular polysaccharide excipient matrix and leucine.

Piezoelectricity in the proteinogenic amino acid L-leucine: A novel piezoactive bioelectret

Here, we report the growth of bioelectret crystal films of L-leucine on conductive substrates and detail the first quantitative measurements of the direct piezoelectric effect in this proteinogenic amino acid. Through extensive electromechanical characterisation, we demonstrate that L-leucine is a promising candidate material for use in non-toxic, biocompatible and biodegradable energy harvesting and sensing devices. The data presented here is among, if not the, largest set of quasi-static, longitudinal piezoelectric measurements on crystalline films of a proteinogenic amino acid to date. We substantiate these measurements using a combination of density functional theory calculations and optical microscopy. Our data provides a further example of the enormous unexploited potential of amino acids and similar biological materials in flexible energy harvesting applications. Their combination of sizeable piezoelectric strain constants and extremely low elastic and dielectric constants makes them ideal as biocompatible replacements for toxic, expensive inorganic piezoelectric materials.

Synthon Robustness and Structural Modularity of Copper(II) Two-Dimensional Coordination Polymers with Isomeric Amino Acids and 4,4′-Bipyridine

Reactions of copper(II) nitrate trihydrate with 4,4′-bipyridine (bipy) and isomeric amino acids (aa) l-leucine or l-isoleucine were investigated under different solution-based and mechanochemical s...

Temperature-Dependent Thermodynamic Properties of Amino Acids in Aqueous Imidazolium-Based Ionic Liquid

Molecular interactions of amino acids with ionic liquids are significant to study the molecular stability and physicochemical properties of amino acids. Mixtures of amino acids l-leucine and N-acetyl-l-leucine + (0.005, 0.010, 0.030, and 0.050 mol·kg–1) aqueous solution of ionic liquid (1-butyl-3-methylimidazolium chloride) at temperature T = (288.15, 298.15, 308.15, and 318.15 K) have been studied by density and speeds of sound measurements. Volumetric properties have been obtained by utilizing data of density. Volumetric properties include apparent molar volumes, partial molar volumes at infinite dilution, limiting partial molar volumes of transfer at infinite dilution, apparent molar expansibility, etc. Similarly, speeds of sound measurements are utilized to calculate corresponding parameters like apparent molar isentropic compression, Kϕ,s, apparent molar isentropic compression at infinite dilution, Kϕ,s0, and transfer compressibility at infinite dilution ΔKϕ,s0. Results confirmed the predominance of ...

Propriedades funcionais e terapêuticas do beta-hidroxi beta-metilbutirato (HMB): uma revisão integrativa

O betahidroxi-beta-metilbutirato (HMB) é um metabólito de cadeia ramificada do aminoácido L-Leucina, sintetizado no fígado e nas células musculares. Apresenta muitas propriedades funcionais, as quais se observam na sua atuação como agente terapêutico em algumas enfermidades, destacando àquelas com acentuado catabolismo proteico, está relacionado ao aumento da força e da massa muscular, portanto atua no tratamento da sarcopenia. Esse estudo é uma revisão de literatura do tipo integrativa, no qual utilizou-se as bases de dados PubMed, eduCAPES, ResearchGate com as palavras-chave “beta-hidroxi- beta-metilbutirato” ou “HMB”, “efeito anabólico do HMB”, “fontes dietéticas” e “propriedades do HMB”. Os resultados foram descritivos, os quais conduziram a pesquisa a dispor os efeitos e propriedades, destacando-se principalmente o seu efeito anabólico, aumento da força e redução da gordura corporal.

Safety and efficacy of l‐leucine produced by fermentation with Escherichia coli NITE BP‐02351 for all animal species

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on l‐leucine produced by fermentation with Escherichia coli NITE BP‐02351 when used as nutritional additive or as feed flavouring compound in feed and water for drinking for all animal species. The product under assessment is l‐leucine produced by fermentation with a genetically modified strain of E. coli (NITE BP‐02351). The production strain and its recombinant DNA were not detected in the final products. l‐Leucine, manufactured by fermentation with E. coli NITE BP‐02351, does not give rise to any safety concern to the production strain. The use of l‐leucine produced with E. coli NITE BP‐02351 is safe for the target species when used to supplement the diet in appropriate amounts. It is safe at the proposed use level of 25 mg/kg when used as flavouring compound for all animal species. The use of l‐leucine produced by fermentation with E. coli NITE BP‐02351 in animal nutrition raises no safety concerns for consumers of animal products. The additive is not irritating to the skin or eyes and is not a skin sensitiser. There is a risk for persons handling the additive from the exposure to endotoxins by inhalation. The use of l‐leucine produced by E. coli NITE BP‐02351 as feed additive does not represent a risk to the environment. The additive l‐leucine produced by E. coli NITE BP‐02351 is regarded as an effective source of the amino acid l‐leucine when used as nutritional additive. For the supplemental l‐leucine to be as efficacious in ruminants as in non‐ruminant species, it requires protection against degradation in the rumen. It is also considered efficacious as feed flavouring compound under the proposed conditions of use.

Synthesis and Antimicrobial Activity of 4-S-Methyl-1,3,4-Oxadiazole Derivatives of Some Natural Amino Acids Bearing Secondary Quaternary Ammonium Salt Moieties

Secondary quaternary ammonium salts (QAS) derived from three natural amino acids (L-Leucine, L-Phenylalanine and L-Methionine) bearing 1,3,4-oxadiazole and acetic acid moieties have been synthesized and characterized by IR, 1 H and 13 C NMR. All the synthesized compounds were evaluated for their preliminary in vitro antibacterial and antifungal activity against different bacterial and fungal strains. All the synthesized compounds showed varying degrees of inhibition against the tested microorganisms. DOI: http://dx.doi.org/10.17807/orbital.v10i7.990

Leucine for the Treatment of Transfusion Dependence in Patients with Diamond Blackfan Anemia

▪Diamond Blackfan anemia (DBA) is a rare, inherited bone marrow failure syndrome characterized by anemia, congenital anomalies and a predisposition to cancer. The patients usually present during infancy or early childhood, but can also present in adulthood. In the majority of cases DBA is due to a mutation in a small or large ribosomal protein (RP) subunit leading to RP haploinsufficiency. The only treatments for the anemia of DBA are red cell transfusions (accompanied by iron chelation), oral corticosteroid therapy or stem cell transplantation. Pospisilova et al. (Haematologica 2007; 92(5):e66-67) reported one complete and two partial erythroid responses after the use of the branched chain amino acid L-leucine in 6 select patients. In skeletal muscle, leucine supplementation can upregulate components of the protein synthetic machinery, including ribosomal proteins, promoting protein translation. Mouse and fish models of DBA respond with amelioration of anemia to L-leucine. We therefore proposed to study the effect of L-leucine on transfusion dependence and growth in subjects with DBA.Methods: The primary objectives were to determine the feasibility of administering L-leucine in subjects with DBA who are red cell transfusion-dependent and to determine the efficacy of L-leucine to produce a hematologic and growth response. The secondary objective was to determine the safety profile of L-leucine. Twelve study sites were involved in this multi-center, Phase I/II study with an anticipated accrual of 50 subjects. A dose of 700 mg/M2 orally three times per day for 9 months was used. Inclusion criteria included age > 2 years, the diagnosis of DBA and transfusion dependence with adequate kidney and liver function. Response was evaluated at 9 months with Complete Response (CR) defined as no further transfusions required and Hb >9; Partial Response (PR): Hb < 9 gm/dL with an increase in reticulocyte count and transfusion interval; and No Response (NR): no change in transfusion needs, Hb or reticulocyte count . Growth percentiles were evaluated at baseline and at completion of 9 months of treatment and the growth velocity change was calculated.Results: The study opened July 2014 and closed February 2017; 55 subjects were consented; 12 were screen failures; 43 subjects were evaluable. There were 21 males; the median age was 9 years 1 month (2 years 5 months - 46 years 1 month). There were no untoward side effects experienced by any subject that were attributable to the L-leucine. Two subjects had an erythroid CR and 1 subject had a PR. The CRs occurred at 1 month and 3 months after start of L-leucine. The subject with PR had an elevated reticulocyte count but was not able to maintain a Hb >9 gm/dL without a transfusion and thus was not transfusion independent. Of the 30 subjects with growth potential who received L-leucine 10 experienced a positive growth velocity change at 9 months of therapy compared to baseline. At a median age of 7.5 years, the mean pre-leucine height percentile was 27 +/- 17.9 and the post-leucine height percentile was 35 +/- 19.9 (p <0.01). The mean weight percentile pre-leucine was 35.4 +/- 26.6 versus the post-Leucine weight percentile of 38.4 +/- 28.1.Conclusions: The administration of L-leucine is safe. L-leucine administration resulted in an erythroid response in 7% of subjects and an increased growth velocity in 33% of growing subjects. Based upon extrapolation from animal models, it is likely that this dose was suboptimal. We hypothesize that higher doses of L-leucine will lead to hematologic responses in more subjects who are transfusion dependent. The potential benefit of added growth in children with DBA may improve final adult height. DisclosuresGlader:Agios: Consultancy, Research Funding.

The influence of surface active l-leucine and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) in the improvement of aerosolization of pyrazinamide and moxifloxacin co-spray dried powders

Pharmacotherapy of tuberculosis is potentially more efficient when delivered by the inhaled route than by the current oral and/or parenteral routes due to the higher concentration of drug reaching the primary region of infection in the lungs. This study investigated the influence of the amino acid l-leucine alone and in combination with the phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), on the aerosolization behaviour of the anti-TB drugs, pyrazinamide and moxifloxacin HCl. Spray dried powders of pyrazinamide (P), moxifloxacin (M) alone and in combination with 10% l-leucine (PL and ML) and 10% DPPC (PLD and MLD) were produced. The particle sizes of all powders except P were in the inhalable size range (<5 µm) but differ in their morphology in presence of the excipients. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed the migration of surface active l-leucine and DPPC onto the surface of the particles during the spray drying process. The aerosolization from a dry powder inhaler, Aerolizer®, using a Next Generation Impactor revealed fine particle fraction (FPF) values for P, PL and PLD of 18.7 ± 3.4%, 53.0 ± 3.2% and 74.5 ± 5.3% respectively while FPF values for M, ML and MLD were 55.6 ± 3.3%, 74.7 ± 4.7% and 74.1 ± 1.3% respectively. In conclusion, the differences in the aerosolization behaviours of the pyrazinamide and moxifloxacin spray dried powders with and without excipients was a combination of difference in the surface morphology and surface composition.

Rapid sensing of l-leucine by human and murine hypothalamic neurons: Neurochemical and mechanistic insights

ObjectiveDietary proteins are sensed by hypothalamic neurons and strongly influence multiple aspects of metabolic health, including appetite, weight gain, and adiposity. However, little is known about the mechanisms by which hypothalamic neural circuits controlling behavior and metabolism sense protein availability. The aim of this study is to characterize how neurons from the mediobasal hypothalamus respond to a signal of protein availability: the amino acid l-leucine. MethodsWe used primary cultures of post-weaning murine mediobasal hypothalamic neurons, hypothalamic neurons derived from human induced pluripotent stem cells, and calcium imaging to characterize rapid neuronal responses to physiological changes in extracellular l-Leucine concentration. ResultsA neurochemically diverse subset of both mouse and human hypothalamic neurons responded rapidly to l-leucine. Consistent with l-leucine's anorexigenic role, we found that 25% of mouse MBH POMC neurons were activated by l-leucine. 10% of MBH NPY neurons were inhibited by l-leucine, and leucine rapidly reduced AGRP secretion, providing a mechanism for the rapid leucine-induced inhibition of foraging behavior in rodents. Surprisingly, none of the candidate mechanisms previously implicated in hypothalamic leucine sensing (KATP channels, mTORC1 signaling, amino-acid decarboxylation) were involved in the acute activity changes produced by l-leucine. Instead, our data indicate that leucine-induced neuronal activation involves a plasma membrane Ca2+ channel, whereas leucine-induced neuronal inhibition is mediated by inhibition of a store-operated Ca2+ current. ConclusionsA subset of neurons in the mediobasal hypothalamus rapidly respond to physiological changes in extracellular leucine concentration. Leucine can produce both increases and decreases in neuronal Ca2+ concentrations in a neurochemically-diverse group of neurons, including some POMC and NPY/AGRP neurons. Our data reveal that leucine can signal through novel mechanisms to rapidly affect neuronal activity.