Amino Acids (v.47, #4)

Amino acid challenge and depletion techniques in human functional neuroimaging studies: an overview by C. S. Biskup; T. Gaber; K. Helmbold; S. Bubenzer-Busch; F. D. Zepf (651-683).
Imbalances of neurotransmitter systems, particularly serotonin (5-HT) and dopamine (DA), are known to play an essential role in many neuropsychiatric disorders. The transient manipulation of such systems through the alteration of their amino acid precursors is a well-known research tool. Among these methods are alterations of tryptophan, the essential amino acid (AA) precursor of 5-HT, as well as manipulations of tyrosine and phenylalanine, the AA precursors of DA, which can be metabolized into norepinephrine and subsequently into epinephrine. These systems can be loaded by applying a large dose of these AAs or depleted by applying an amino acid mixture lacking the respective AAs serving as precursors. Functional neuroimaging has given insights into differential brain activation patterns and functions depending on the tasks performed, pharmacological treatments or specific disorders. Such research has shed light on the function of many brain areas as well as their interactions. The combination of AA challenge approaches with neuroimaging techniques has been subject of numerous studies. Overall, the studies conducted in this particular field of research have shown that AA challenge techniques are valid and effective research tools that allow the investigation of serotonergic and dopaminergic systems without causing serious side effects or long-term damage to the subjects. In this review, we will present an overview of the results obtained so far and discuss the implications of these findings as well as open questions that remain to be answered.
Keywords: Amino acids; fMRI; PET; Tryptophan; Tyrosine; Phenylalanine

Citrulline and nitrogen homeostasis: an overview by C. Breuillard; L. Cynober; C. Moinard (685-691).
Citrulline (Cit) is a non-essential amino acid whose metabolic properties were largely ignored until the last decade when it began to emerge as a highly promising nutrient with many regulatory properties, with a key role in nitrogen homeostasis. Because Cit is not taken up by the liver, its synthesis from arginine, glutamine, ornithine and proline in the intestine prevents the hepatic uptake of the two first amino acids which activate the urea cycle and so prevents amino acid catabolism. This sparing effect may have positive spin-off for muscle via increased protein synthesis, protein content and functionality. However, the mechanisms of action of Cit are not fully known, even if preliminary data suggest an implication of mTOR pathway. Further exploration is needed to gain a complete overview of the role of Cit in the control of nitrogen homeostasis.
Keywords: Citrulline; Amino acids; Protein turnover; Muscle; Liver

Human intestine luminal ACE2 and amino acid transporter expression increased by ACE-inhibitors by Raphael N. Vuille-dit-Bille; Simone M. Camargo; Luca Emmenegger; Tom Sasse; Eva Kummer; Julia Jando; Qeumars M. Hamie; Chantal F. Meier; Schirin Hunziker; Zsofia Forras-Kaufmann; Sena Kuyumcu; Mark Fox; Werner Schwizer; Michael Fried; Maja Lindenmeyer; Oliver Götze; François Verrey (693-705).
Sodium-dependent neutral amino acid transporter B0AT1 (SLC6A19) and imino acid (proline) transporter SIT1 (SLC6A20) are expressed at the luminal membrane of small intestine enterocytes and proximal tubule kidney cells where they exert key functions for amino acid (re)absorption as documented by their role in Hartnup disorder and iminoglycinuria, respectively. Expression of B0AT1 was shown in rodent intestine to depend on the presence of the carboxypeptidase angiotensin-converting enzyme 2 (ACE2). This enzyme belongs to the renin-angiotensin system and its expression is induced by treatment with ACE-inhibitors (ACEIs) or angiotensin II AT1 receptor blockers (ARBs) in many rodent tissues. We show here in the Xenopus laevis oocyte expression system that human ACE2 also functionally interacts with SIT1. To investigate in human intestine the potential effect of ACEIs or ARBs on ACE2, we analysed intestinal biopsies taken during routine gastroduodenoscopy and ileocolonoscopy from 46 patients of which 9 were under ACEI and 13 ARB treatment. Analysis of transcript expression by real-time PCR and of proteins by immunofluorescence showed a co-localization of SIT1 and B0AT1 with ACE2 in the brush-border membrane of human small intestine enterocytes and a distinct axial expression pattern of the tested gene products along the intestine. Patients treated with ACEIs displayed in comparison with untreated controls increased intestinal mRNA levels of ACE2, peptide transporter PEPT1 (SLC15A1) and AA transporters B0AT1 and PAT1 (SLC36A1). This study unravels in human intestine the localization and distribution of intestinal transporters involved in amino acid absorption and suggests that ACEIs impact on their expression.
Keywords: B0AT1; SIT1; ACE2; Intestine

Improving the acidic stability of Staphylococcus aureus α-acetolactate decarboxylase in Bacillus subtilis by changing basic residues to acidic residues by Xian Zhang; Zhiming Rao; Jingjing Li; Junping Zhou; Taowei Yang; Meijuan Xu; Teng Bao; Xiaojing Zhao (707-717).
The α-acetolactate decarboxylase (ALDC) can reduce diacetyl fleetly to promote mature beer. A safe strain Bacillus subtilis WB600 for high-yield production of ALDC was constructed with the ALDC gene saald from Staphylococcus aureus L3-15. SDS-PAGE analysis revealed that S. aureus α-acetolactate decarboxylase (SaALDC) was successfully expressed in recombinant B. siutilis strain. The enzyme SaALDC was purified using Ni-affinity chromatography and showed a maximum activity at 45 °C and pH 6.0. The values of K m and V max were 17.7 μM and 2.06 mM min−1, respectively. Due to the unstable property of SaALDC at low pH conditions that needed in brewing process, site-directed mutagenesis was proposed for improving the acidic stability of SaALDC. Homology comparative modeling analysis showed that the mutation (K52D) gave rise to the negative-electrostatic potential on the surface of protein while the numbers of hydrogen bonds between the mutation site (N43D) and the around residues increased. Taken together the effect of mutation N43D-K52D, recombinant SaALDCN43D-K52D showed dramatically improved acidic stability with prolonged half-life of 3.5 h (compared to the WT of 1.5 h) at pH 4.0. In a 5-L fermenter, the recombinant B. subtilis strain that could over-express SaALDCN43D-K52D exhibited a high yield of 135.8 U mL−1 of SaALDC activity, about 320 times higher comparing to 0.42 U mL−1 of S. aureus L3-15. This work proposed a  strategy for improving the acidic stability of SaALDC in the B. subtilis host.
Keywords: α-Acetolactate decarboxylase; Diacetyl; Acidic stability; Site-directed mutagenesis; Bacillus subtilis

Synthesis and preliminary biological evaluation of S-11C-methyl-d-cysteine as a new amino acid PET tracer for cancer imaging by Tingting Huang; Ganghua Tang; Hongliang Wang; Dahong Nie; Xiaolan Tang; Xiang Liang; Kongzhen Hu; Chang Yi; Baoguo Yao; Caihua Tang (719-727).
S-11C-methyl-l-cysteine (LMCYS) is an attractive amino acid tracer for clinical tumor positron emission tomography (PET) imaging. d-isomers of some radiolabeled amino acids are potential PET tracers for tumor imaging. In this work, S-11C-methyl-d-cysteine (DMCYS), a d-amino acid isomer of S-11C-methyl-cysteine for tumor imaging was developed and evaluated. DMCYS was prepared by 11C-methylation of the precursor d-cysteine, with an uncorrected radiochemical yield over 50 % from 11CH3I within a total synthesis time from 11CO2 about 12 min. In vitro competitive inhibition studies showed that DMCYS uptake was primarily transported through the Na+-independent system L, and also the Na+-dependent system B0,+ and system ASC, with almost no system A. In vitro incorporation experiments indicated that almost no protein incorporation was found in Hepa 1–6 hepatoma cell lines. Biodistribution studies demonstrated higher uptake of DMCYS in pancreas and liver at 5 min post-injection, relatively lower uptake in brain and muscle, and faster radioactivity clearance from most tissues than those of l-isomer during the entire observation time. In the PET imaging of S180 fibrosarcoma–bearing mice and turpentine-induced inflammatory model mice, 2-18F-fluoro-2-deoxy-d-glucose (FDG) exhibited significantly high accumulation in both tumor and inflammatory lesion with low tumor-to-inflammation ratio of 1.40, and LMCYS showed low tumor-to-inflammation ratio of 1.64 at 60 min post-injection. By contrast, DMCYS showed moderate accumulation in tumor and very low uptake in inflammatory lesion, leading to relatively higher tumor-to-inflammation ratio of 2.25 than 11C-methyl-l-methionine (MET) (1.85) at 60 min post-injection. Also, PET images of orthotopic transplanted glioma models demonstrated that low uptake of DMCYS in normal brain tissue and high uptake in brain glioma tissue were observed. The results suggest that DMCYS is a little better than the corresponding l-isomers as a potential PET tumor-detecting agent and is superior to MET and FDG in the differentiation of tumor from inflammation.
Keywords: Amino acid transporter; Tumor; PET imaging; S-11C-methyl-d-cysteine

FRET-based analysis of protein-nucleic acid interactions by genetically incorporating a fluorescent amino acid by Hyojin Park; Heejin Kang; Wooseok Ko; Wonkoo Lee; Kyubong Jo; Hyun Soo Lee (729-734).
Protein–nucleic acid interaction is an important process in many biological phenomena. In this study, a fluorescence resonance energy transfer (FRET)-based protein–DNA binding assay has been developed, in which a fluorescent amino acid is genetically incorporated into a DNA-binding protein. A coumarin-containing amino acid was incorporated into a DNA-binding protein, and the mutant protein specifically produced a FRET signal upon binding to its cognate DNA labeled with a fluorophore. The protein–DNA binding affinity was then measured under equilibrium conditions. This method is advantageous for studying protein-nucleic acid interactions, because it is performed under equilibrium conditions, technically easy, and applicable to any nucleic acid-binding protein.
Keywords: Protein–DNA interaction; Unnatural amino acids; Fluorescence resonance energy transfer

The goal of the study is to investigate the preventive effect of taurine against arsenite-induced arrest of neuronal differentiation in N2a cells. Our results revealed that taurine reinstated the neurite outgrowth in arsenite-treated N2a cells. Meanwhile, arsenite-induced oxidative stress and mitochondrial dysfunction as well as degradation of mitochondria DNA (mtDNA) were also inhibited by co-treatment of taurine. Since oxidative stress and mitochondrial dysfunction is closely associated with endoplasmic reticulum (ER) stress, we further examined indicators of ER stress, 78 kDa glucose-regulated protein (GRP78), and C/EBP-homologous protein (CHOP) protein expression. The results demonstrated that taurine significantly reduced arsenite-induced ER stress in N2a cells. In the parallel experiment, arsenite-induced disruption of intracellular calcium homeostasis was also ameliorated by taurine. The proven bio-function of taurine preserved a preventive effect against deleteriously cross-talking between oxidative stress, mitochondria, and ER. Overall, the results of the study suggested that taurine reinstated neuronal differentiation by inhibiting oxidative stress, ER stress, and mitochondrial dysfunction in arsenite-treated N2a cells.
Keywords: Arsenite; Neuronal differentiation; Taurine; ER stress; Oxidative stress

Leucine supplementation does not affect protein turnover and impairs the beneficial effects of endurance training on glucose homeostasis in healthy mice by José M. Costa Júnior; Morgana R. Rosa; André O. Protzek; Flávia M. de Paula; Sandra M. Ferreira; Luiz F. Rezende; Emerielle C. Vanzela; Cláudio C. Zoppi; Leonardo R. Silveira; Isis C. Kettelhut; Antonio C. Boschero; Camila A. M. de Oliveira; Everardo M. Carneiro (745-755).
Endurance exercise training as well as leucine supplementation modulates glucose homeostasis and protein turnover in mammals. Here, we analyze whether leucine supplementation alters the effects of endurance exercise on these parameters in healthy mice. Mice were distributed into sedentary (C) and exercise (T) groups. The exercise group performed a 12-week swimming protocol. Half of the C and T mice, designated as the CL and TL groups, were supplemented with leucine (1.5 % dissolved in the drinking water) throughout the experiment. As well known, endurance exercise training reduced body weight and the retroperitoneal fat pad, increased soleus mass, increased VO2max, decreased muscle proteolysis, and ameliorated peripheral insulin sensitivity. Leucine supplementation had no effect on any of these parameters and worsened glucose tolerance in both CL and TL mice. In the soleus muscle of the T group, AS-160Thr-642 (AKT substrate of 160 kDa) and AMPKThr-172 (AMP-Activated Protein Kinase) phosphorylation was increased by exercise in both basal and insulin-stimulated conditions, but it was reduced in TL mice with insulin stimulation compared with the T group. Akt phosphorylation was not affected by exercise but was lower in the CL group compared with the other groups. Leucine supplementation increased mTOR phosphorylation at basal conditions, whereas exercise reduced it in the presence of insulin, despite no alterations in protein synthesis. In trained groups, the total FoxO3a protein content and the mRNA for the specific isoforms E2 and E3 ligases were reduced. In conclusion, leucine supplementation did not potentiate the effects of endurance training on protein turnover, and it also reduced its positive effects on glucose homeostasis.
Keywords: Endurance exercise; Leucine supplementation; Skeletal muscle adaptations

Simple and eco-friendly biosynthesis approach was developed to synthesize silver nanoparticles (SNPs) and gold nanoparticles (GNPs) using Ficus racemosa latex as reducing agent. The presence of sunlight is utilized with latex and achieved the nanoparticles whose average size was in the range of 50–120 nm for SNPs and 20–50 nm for GNPs. The synthesized nanoparticles were characterized by UV/Visible absorption spectroscopy, X-ray diffraction, and field emission—scanning electron microscopy techniques toget understand the obtained nanoparticles. The pH-dependent binding studies of SNPs and GNPs with four amino acids, namely l-lysine, l-arginine, l-glutamine and glycin have been reported.
Keywords: Silver and gold nanoparticles; Ficus racemosa latex; Amino acids; Association constant

Unaccustomed high-intensity eccentric exercise (ECC) can provoke muscle damage including several days of muscle force loss. Post-exercise dietary supplementation may provide a strategy to accelerate rate of force regain by affecting mechanisms related to muscle protein turnover. The aim of the current study was to investigate if protein signaling mechanisms involved in muscle protein turnover would be differentially affected by supplementation with either whey protein hydrolysate and carbohydrate (WPH+CHO) versus isocaloric carbohydrate (CHO) after muscle-damaging ECC. Twenty-four young healthy participants received either WPH+CHO (n = 12) or CHO supplements (n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to, at 3 h and at 24, 48, 96 and/or 168 h post-exercise, muscle strength, muscle soreness, and Akt-mTOR and FOXO signaling proteins, were measured in an ECC exercising leg and in the contralateral non-exercise control leg (CON). After ECC, muscle force decreased by 23–27 % at 24 h post-exercise, which was followed by gradual, although not full recovery at 168 h post-exercise, with no differences between supplement groups. Phosphorylation of mTOR, p70S6K and rpS6 increased and phosphorylation of FOXO1 and FOXO3 decreased in the ECC leg, with no differences between supplement groups. Phosphorylation changes were also observed for rpS6, FOXO1 and FOXO3a in the CON leg, suggesting occurrence of remote tissue effects. In conclusion, divergent dietary supplementation types did not produce differences in signaling for muscle turnover during recovery from muscle-damaging exercise.
Keywords: Whey protein; Eccentric exercise; Recovery; mTOR signaling; MuRF1; FOXO1/3A signaling

A direct method for the synthesis of orthogonally protected furyl- and thienyl- amino acids by Alex S. Hudson; Laurent Caron; Neil Colgin; Steven L. Cobb (779-785).
The synthesis of unnatural amino acids plays a key part in expanding the potential application of peptide-based drugs and in the total synthesis of peptide natural products. Herein, we report a direct method for the synthesis of orthogonally protected 5-membered heteroaromatic amino acids.
Keywords: Heteroaromatic amino acids; Negishi cross-coupling; Furyl-alanine; Thienyl-alanine

Difficult peptides are a constant challenge in solid-phase peptide synthesis. In particular, hydroxyl amino acids such as serine can cause severe breakdowns in coupling yields even several amino acids after the insertion of the critical amino acid. This paper investigates several methods of improving synthesis yields of difficult peptides including the use of different resins, activators and the incorporation of a structure-breaking pseudoproline dipeptide building block both alone and in combination with each other.
Keywords: Difficult peptides; Pseudoproline dipeptides; Fmoc solid-phase synthesis; ChemMatrix resin

The modulation of NMDA receptors and l-arginine/nitric oxide pathway is implicated in the anti-immobility effect of creatine in the tail suspension test by Mauricio P. Cunha; Francis L. Pazini; Fabiana K. Ludka; Julia M. Rosa; Ágatha Oliveira; Josiane Budni; Ana B. Ramos-Hryb; Vicente Lieberknecht; Luis E. B. Bettio; Maria D. Martín-de-Saavedra; Manuela G. López; Carla I. Tasca; Ana Lúcia S. Rodrigues (795-811).
The modulation of N-methyl-D-aspartate receptor (NMDAR) and l-arginine/nitric oxide (NO) pathway is a therapeutic strategy for treating depression and neurologic disorders that involves excitotoxicity. Literature data have reported that creatine exhibits antidepressant and neuroprotective effects, but the implication of NMDAR and l-arginine/nitric oxide (NO) pathway in these effects is not established. This study evaluated the influence of pharmacological agents that modulate NMDAR/l-arginine-NO pathway in the anti-immobility effect of creatine in the tail suspension test (TST) in mice. The NOx levels and cellular viability in hippocampal and cerebrocortical slices of creatine-treated mice were also evaluated. The anti-immobility effect of creatine (10 mg/kg, po) in the TST was abolished by NMDA (0.1 pmol/mouse, icv), d-serine (30 µg/mouse, icv, glycine-site NMDAR agonist), arcaine (1 mg/kg, ip, polyamine site NMDAR antagonist), l-arginine (750 mg/kg, ip, NO precursor), SNAP (25 μg/mouse, icv, NO donor), L-NAME (175 mg/kg, ip, non-selective NOS inhibitor) or 7-nitroindazole (50 mg/kg, ip, neuronal NOS inhibitor), but not by DNQX (2.5 µg/mouse, icv, AMPA receptor antagonist). The combined administration of sub-effective doses of creatine (0.01 mg/kg, po) and NMDAR antagonists MK-801 (0.001 mg/kg, po) or ketamine (0.1 mg/kg, ip) reduced immobility time in the TST. Creatine (10 mg/kg, po) increased cellular viability in hippocampal and cerebrocortical slices and enhanced hippocampal and cerebrocortical NO x levels, an effect potentiated by l-arginine or SNAP and abolished by 7-nitroindazole or L-NAME. In conclusion, the anti-immobility effect of creatine in the TST involves NMDAR inhibition and enhancement of NO levels accompanied by an increase in neural viability.
Keywords: Antidepressant; Cellular viability; Creatine; Nitric Oxide; NMDA; Tail suspension test

The purpose of this study was to examine whether the replacement of the positively-charged Lys or Arg linker with a neutral linker could reduce the renal uptake of Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (α-MSH) hybrid peptide. The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys3,4,10, D-Phe7, Arg11]α-MSH3-13 {(Arg11)CCMSH} through the neutral βAla or Ahx {aminohexanoic acid} linker (replacing the Lys or Arg linker) to generate novel RGD-βAla-(Arg11)CCMSH and RGD-Ahx-(Arg11)CCMSH hybrid peptides. The receptor-binding affinity and cytotoxicity of RGD-βAla-(Arg11)CCMSH and RGD-Ahx-(Arg11)CCMSH were determined in B16/F1 melanoma cells. The melanoma targeting and imaging properties of 99mTc-RGD-βAla-(Arg11)CCMSH and 99mTc-RGD-Ahx-(Arg11)CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The replacement of the Lys or Arg linker with the βAla or Ahx linker retained nanomolar receptor-binding affinities and remarkable cytotoxicity of RGD-βAla-(Arg11)CCMSH and RGD-Ahx-(Arg11)CCMSH. The receptor-binding affinities of RGD-βAla-(Arg11)CCMSH and RGD-Ahx-(Arg11)CCMSH were 0.8 ± 0.05 and 1.3 ± 0.1 nM. Three-hour incubation with 0.1 µM of RGD-βAla-(Arg11)CCMSH and RGD-Ahx-(Arg11)CCMSH decreased the survival percentages of B16/F1 cells by 71 and 67 % as compared to the untreated control cells 5 days post the treatment. The replacement of the Arg linker with the βAla or Ahx linker reduced the non-specific renal uptake of 99mTc-RGD-βAla-(Arg11)CCMSH and 99mTc-RGD-Ahx-(Arg11)CCMSH by 62 and 61 % at 2 h post-injection. 99mTc-RGD-βAla-(Arg11)CCMSH displayed higher melanoma uptake than 99mTc-RGD-Ahx-(Arg11)CCMSH at 0.5, 2, 4, and 24 h post-injection. Enhanced tumor to kidney uptake ratio of 99mTc-RGD-βAla-(Arg11)CCMSH warranted the further evaluation of 188Re-labeled RGD-βAla-(Arg11)CCMSH as a novel MC1 receptor-targeting therapeutic peptide for melanoma treatment in the future.
Keywords: Arg-Gly-Asp; Alpha-melanocyte stimulating hormone hybrid peptide; Melanoma imaging

Dark-induced senescence of barley leaves involves activation of plastid transglutaminases by E. Sobieszczuk-Nowicka; A. Zmienko; A. Samelak-Czajka; M. Łuczak; M. Pietrowska-Borek; R. Iorio; S. Del Duca; M. Figlerowicz; J. Legocka (825-838).
Transglutaminases (E.C. catalyze the post-translational modification of proteins by establishing ε-(γ-glutamyl) lysine isopeptide bonds and by the covalent conjugation of polyamines to endo-glutamyl residues of proteins. In light of the confirmed role of transglutaminases in animal cell apoptosis and only limited information on the role of these enzymes in plant senescence, we decided to investigate the activity of chloroplast transglutaminases (ChlTGases) and the fate of chloroplast-associated polyamines in Hordeum vulgare L. ‘Nagrad’ leaves, where the senescence process was induced by darkness (day 0) and continued until chloroplast degradation (day 12). Using an anti-TGase antibody, we detected on a subcellular level, the ChlTGases that were associated with destacked/degraded thylakoid membranes, and beginning on day 5, were also found in the stroma. Colorimetric and radiometric assays revealed during senescence an increase in ChlTGases enzymatic activity. The MS/MS identification of plastid proteins conjugated with exogenous polyamines had shown that the ChlTGases are engaged in the post-translational modification of proteins involved in photosystem organization, stress response, and oxidation processes. We also computationally identified the cDNA of Hv-Png1-like, a barley homologue of the Arabidopsis AtPng1 gene. Its mRNA level was raised from days 3 to 10, indicating that transcriptional regulation controls the activity of barley ChlTGases. Together, the presented results deepen our knowledge of the mechanisms of the events happened in dark-induced senescence of barley leaves that might be activation of plastid transglutaminases.
Keywords: Chloroplast; Leaf; Hv-Png1-like gene; Polyamines; Senescence; Transglutaminases

Betaine supplementation prevents fatty liver induced by a high-fat diet: effects on one-carbon metabolism by Rafael Deminice; Robin P. da Silva; Simon G. Lamarre; Karen B. Kelly; René L. Jacobs; Margaret E. Brosnan; John T. Brosnan (839-846).
The purpose of this study was to examine the effects of betaine supplementation on the regulation of one-carbon metabolism and liver lipid accumulation induced by a high-fat diet in rats. Rats were fed one of three different liquid diets: control diet, high-fat diet and high-fat diet supplemented with betaine. The control and high-fat liquid diets contained, respectively, 35 and 71 % of energy derived from fat. Betaine supplementation involved the addition of 1 % (g/L) to the diet. After three weeks on the high-fat diet the rats had increased total liver fat concentration, liver triglycerides, liver TBARS and plasma TNF-α. The high-fat diet decreased the hepatic S-adenosylmethionine concentration and the S-adenosylmethionine/S-adenosylhomocysteine ratio compared to the control as well as altering the expression of genes involved in one-carbon metabolism. Betaine supplementation substantially increased the hepatic S-adenosylmethionine concentration (~fourfold) and prevented fatty liver and hepatic injury induced by the high-fat diet. It was accompanied by the normalization of the gene expression of BHMT, GNMT and MGAT, which code for key enzymes of one-carbon metabolism related to liver fat accumulation. In conclusion, the regulation of the expression of MGAT by betaine supplementation provides an additional and novel mechanism by which betaine supplementation regulates lipid metabolism and prevents accumulation of fat in the liver.
Keywords: Betaine; Liver; High-fat diet; S-adenosylmethionine

Protein deficiency has been observed as a leading cause of malnutrition and child death in the tropics. The current study evaluated the protein quality of 49 important breadfruit cultivars (41 Artocarpus altilis and 8 hybrids of A. altilis × A. mariannensis). While significant differences were found between cultivars, all varieties contained a full spectrum of the essential amino acids and are especially rich in phenylalanine, leucine, isoleucine, and valine. The cultivar Ma’afala contained significantly higher total essential amino acid content than other varieties and higher-quality protein than staples such as corn, wheat, rice, soybean, potato, and pea.
Keywords: Breadfruit; Artocarpus altilis ; Protein quality; Essential amino acids