Amino Acid Deficiency Research Articles

Magnetic resonance spin-spin relaxation time estimation in a rat model of fatty liver disease.

To compare mono- and bi-exponential relaxation model equations to discriminate between normal and fatty liver disease. Six rats on a choline deficient amino acid modified (CDAA) diet and six on normal chow were studied. Multiple spin echo images with increasing echo times (TEs) were collected at 9.4T. Pixel-wise T2 maps were generated using mono-exponential decay function to calculate T2M , and a bi-exponential to calculate, short T2 component (T2S ), long T2 component (T2L ), and fractions of these components (ρS , ρL ), respectively. Statistical F-tests and Akaike's information criterion (AIC) were used to assess the relative performance of the two models. F-test and AIC showed that in the CDAA group, T2 bi-exponential model described the signal of T2 weighted imaging of the liver better than the mono-exponential model. Controls were best described by the mono-exponential model. Mean values for T2M , T2L , T2S , ρS , ρL were 31.2 ± 0.7 ms, 72.8 ± 3.3 ms, 8.2 ± 0.6 ms,71.2 ± 2.1%, 30.4 ± 1.3%, respectively, in CDAA rats, compared with 18.8 ± 0.5 ms, 32.3 ± 0.7 ms, 9.2 ± 1.8 ms, 79 ± 2%, 21.0 ± 1.1% in controls. In the fatty liver of CDAA rats we have shown that T2 weighted images fit the bi-exponential model better than mono-exponential decays thus providing a better description of the data. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:468-476.

Dietary Methionine Restriction Regulates Liver Protein Synthesis and Gene Expression Independently of Eukaryotic Initiation Factor 2 Phosphorylation in Mice

Background: The phosphorylation of eukaryotic initiation factor 2 (p-eIF2) during dietary amino acid insufficiency reduces protein synthesis and alters gene expression via the integrated stress response (ISR).Objective: We explored whether a Met-restricted (MR) diet activates the ISR to reduce body fat and regulate protein balance.Methods: Male and female mice aged 3-6 mo with either whole-body deletion of general control nonderepressible 2 (Gcn2) or liver-specific deletion of protein kinase R-like endoplasmic reticulum kinase (Perk) alongside wild-type or floxed control mice were fed an obesogenic diet sufficient in Met (0.86%) or an MR (0.12% Met) diet for ≤5 wk. Ala enrichment with deuterium was measured to calculate protein synthesis rates. The guanine nucleotide exchange factor activity of eIF2B was measured alongside p-eIF2 and hepatic mRNA expression levels at 2 d and 5 wk. Metabolic phenotyping was conducted at 4 wk, and body composition was measured throughout. Results were evaluated with the use of ANOVA (P < 0.05).Results: Feeding an MR diet for 2 d did not increase hepatic p-eIF2 or reduce eIF2B activity in wild-type or Gcn2-/- mice, yet many genes transcriptionally regulated by the ISR were altered in both strains in the same direction and amplitude. Feeding an MR diet for 5 wk increased p-eIF2 and reduced eIF2B activity in wild-type but not Gcn2-/- mice, yet ISR-regulated genes altered in both strains similarly. Furthermore, the MR diet reduced mixed and cytosolic but not mitochondrial protein synthesis in both the liver and skeletal muscle regardless of Gcn2 status. Despite the similarities between strains, the MR diet did not increase energy expenditure or reduce body fat in Gcn2-/- mice. Finally, feeding the MR diet to mice with Perk deleted in the liver increased hepatic p-eIF2 and altered body composition similar to floxed controls.Conclusions: Hepatic activation of the ISR resulting from an MR diet does not require p-eIF2. Gcn2 status influences body fat loss but not protein balance when Met is restricted.

Activation of the Amino Acid Response Pathway Blunts the Effects of Cardiac Stress.

BackgroundThe amino acid response (AAR) is an evolutionarily conserved protective mechanism activated by amino acid deficiency through a key kinase, general control nonderepressible 2. In addition to mobilizing amino acids, the AAR broadly affects gene and protein expression in a variety of pathways and elicits antifibrotic, autophagic, and anti‐inflammatory activities. However, little is known regarding its role in cardiac stress. Our aim was to investigate the effects of halofuginone, a prolyl‐tRNA synthetase inhibitor, on the AAR pathway in cardiac fibroblasts, cardiomyocytes, and in mouse models of cardiac stress and failure.Methods and ResultsConsistent with its ability to inhibit prolyl‐tRNA synthetase, halofuginone elicited a general control nonderepressible 2–dependent activation of the AAR pathway in cardiac fibroblasts as evidenced by activation of known AAR target genes, broad regulation of the transcriptome and proteome, and reversal by l‐proline supplementation. Halofuginone was examined in 3 mouse models of cardiac stress: angiotensin II/phenylephrine, transverse aortic constriction, and acute ischemia reperfusion injury. It activated the AAR pathway in the heart, improved survival, pulmonary congestion, left ventricle remodeling/fibrosis, and left ventricular function, and rescued ischemic myocardium. In human cardiac fibroblasts, halofuginone profoundly reduced collagen deposition in a general control nonderepressible 2–dependent manner and suppressed the extracellular matrix proteome. In human induced pluripotent stem cell–derived cardiomyocytes, halofuginone blocked gene expression associated with endothelin‐1‐mediated activation of pathologic hypertrophy and restored autophagy in a general control nonderepressible 2/eIF2α‐dependent manner.ConclusionsHalofuginone activated the AAR pathway in the heart and attenuated the structural and functional effects of cardiac stress.

Effects of dietary essential amino acid deficiencies on the growth performance and humoral immune response in silvery-black porgy (Sparidentex hasta) juveniles

A 6-week feeding trial was conducted for determining the effects of dietary essential amino acids (EAA) deficiencies on growth performance and non-specific immune responses in silvery-black porgy juveniles (4.7 ± 0.1 g initial weight). Eleven isoproteic (ca. 47%) diets were formulated including a control diet containing the optimum quantity of EAA, and ten EAA-deficient diets. All diets contained 36% fish meal and 18.5% crystalline EAA and non-essential amino acids (NEAA) as the main source of dietary proteins. All the EAA and NEAA incorporated in the crystalline amino acids mixture of the control diet simulated the amino acids profile of the fish meal. The other 10 EAA-deficient diets were formulated by the deletion of each of the 10 EAA (crystalline form) from the control diet and replaced by a mixture of NEAA for the adjustment of dietary nitrogen contents. At the end of the experiment, fish fed with threonine-deficient diet showed the lowest survival rate (p < .05), whereas growth performance decreased in fish fed all EAA-deficient diets, although the reduction in body growth varied depending on the EAA considered. Plasma total protein decreased in all experimental groups except for fish fed the phenylalanine-deficient diet. Fish fed with arginine- and lysine-deficient diets had the lowest plasma C3, C4, lysozyme, total immunoglobulin and total superoxide dismutase activity (p < .05). Present results indicated that lysine, methionine and threonine were the most limiting EAA in terms of growth performance; however, arginine, threonine and lysine were the most limiting EAA for innate immunity responses in silvery-black porgy juveniles.

Use of L- arginine in the treatment of comorbid pathology in neurological patients

Amino acids are the structural chemical units that make up proteins. The special importance of amino acids is that some of them - precursors of neurotransmitters which are necessary for normal functioning of the brain. The absence one of essential amino acid suspend the formation of protein. Correction of deficiency of essential amino acids and replacement carried out by different drugs. Recently, interest in preparations that contain arginine significantly increased. This interest caused by the importance of L- arginine in the body functioning, as L- Arginine is a precursor of nitric oxide (NO). Arginine (Valagyn) is a common post-translational modification of proteins tsytoplazmatycheskyh that has a unique transcriptional regulatory pathways. L-arginine showed a protective effect in ischemia / reperfusion injury, which can be widely used in various diseases of the cardio-sudinnoyi system and metabolic disorders

ATP-driven and AMPK-independent autophagy in an early branching eukaryotic parasite

ABSTRACTAutophagy is a catabolic cellular process required to maintain protein synthesis, energy production and other essential activities in starved cells. While the exact nutrient sensor(s) is yet to be identified, deprivation of amino acids, glucose, growth factor and other nutrients can serve as metabolic stimuli to initiate autophagy in higher eukaryotes. In the early-branching unicellular parasite Trypanosoma brucei, which can proliferate as procyclic form (PCF) in the tsetse fly or as bloodstream form (BSF) in animal hosts, autophagy is robustly triggered by amino acid deficiency but not by glucose depletion. Taking advantage of the clearly defined adenosine triphosphate (ATP) production pathways in T. brucei, we have shown that autophagic activity depends on the levels of cellular ATP production, using either glucose or proline as a carbon source. While autophagosome formation positively correlates with cellular ATP levels; perturbation of ATP production by removing carbon sources or genetic silencing of enzymes involved in ATP generation pathways, also inhibited autophagy. This obligate energy dependence and the lack of glucose starvation-induced autophagy in T. brucei may reflect an adaptation to its specialized, parasitic life style.

Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine.

Nonessential amino acids are synthesized de novo and therefore not diet dependent. In contrast, essential amino acids must be obtained through nutrition since they cannot be synthesized internally. Several nonessential amino acids may become essential under conditions of stress and catabolic states when the capacity of endogenous amino acid synthesis is exceeded. Arginine and glutamine are 2 such conditionally essential amino acids and are the focus of this review. Low arginine bioavailability plays a pivotal role in the pathogenesis of a growing number of varied diseases, including sickle cell disease, thalassemia, malaria, acute asthma, cystic fibrosis, pulmonary hypertension, cardiovascular disease, certain cancers, and trauma, among others. Catabolism of arginine by arginase enzymes is the most common cause of an acquired arginine deficiency syndrome, frequently contributing to endothelial dysfunction and/or T-cell dysfunction, depending on the clinical scenario and disease state. Glutamine, an arginine precursor, is one of the most abundant amino acids in the body and, like arginine, becomes deficient in several conditions of stress, including critical illness, trauma, infection, cancer, and gastrointestinal disorders. At-risk populations are discussed together with therapeutic options that target these specific acquired amino acid deficiencies.

The effect of amino acid deprivation on the transfer of iron through Caco-2 cell monolayers

Iron (Fe) metabolism is modified by many nutritional factors. Amino acids (AA) play a central role in various biological processes, such as protein synthesis and energy supply. However, the influence of AA status on iron metabolism has not been investigated. Here, we test whether AA alters iron metabolism in an intestinal cell model. Both Fe uptake and transfer across the cell monolayer were significantly increased by non-essential AA deficiency (both p<0.001) while only Fe transfer was increased by essential AA deficiency (p<0.0001). Both essential and non-essential AA deficiency decreased DMT1 (±IRE) exon1A mRNA expression (respectively p=0.0007 and p=0.006) and increased expression of ferritin heavy chain. DMT1+IRE (also expressing exon1A or 1B) mRNA levels were decreased by essential AA deficiency (p=0.012). The mRNA levels of total DMT1 were also decreased by essential, but not non-essential, AA deficiency (p=0.006). Hepcidin levels were increased significantly by non-essential amino acid deprivation (p=0.047). Protein levels of ferroportin and/or ferritin heavy chain were not altered by AA deficiency, suggesting that they had no effect on Fe efflux or storage in the cell, though iron content of ferritin could be increased. Our data demonstrate, for the first time, that AA status affects iron transport and the expression of genes related to iron metabolism in Caco-2 cells, although the changes observed are not sufficient to explain the alteration in iron transport. We hypothesise that the effect on Fe transfer is mediated through an increased movement across the cell layer, rather than transfer across the cell membranes.

Prevalence of Nutritional Deficiencies in Hair Loss among Indian Participants: Results of a Cross-sectional Study.

Background:Nutritional deficiencies are known to be associated with hair loss; however, the exact prevalence is not known.Aims:The aim of this study is to evaluate the prevalence of nutritional deficiencies in participants with hair loss.Materials and Methods:In this cross-sectional study, 100 enrolled participants were divided into telogen effluvium (TE), male-pattern hair loss (MPHL), and female-pattern hair loss (FPHL) based on the type of hair loss. All participants underwent laboratory estimation for micronutrients and amino acid levels.Results:Participants with hair loss showed varied amino acid and micronutrient deficiencies across all types of hair loss. Nutritional status did not vary much between the types of hair loss. Among the essential amino acids, histidine deficiency was seen in >90% of participants with androgenic alopecia and 77.78% of participants with TE while leucine deficiency was seen 98.15% of participants with TE and 100% with FPHL. Valine deficiency was also very common across alopecia subtypes. Among the nonessential amino acids, alanine deficiency was observed in 91.67% FPHL, 91.18% MPHL, and 90.74% TE. Cysteine deficiency was present in 55.58% and 50% of participants with MPHL and TE, respectively. A relatively higher proportion of participants with TE had iron deficiency compared to androgenic alopecia (P = 0.069). Zinc deficiency was seen in 11.76% of participants with MPHL while copper deficiency was seen in 29.41% and 31.48% of participants with MPHL and TE, respectively.Conclusion:Nutritional deficiency is a common problem in participants with hair loss irrespective of the type of alopecia. The findings of our study suggest need for identification and correction of nutritional deficiencies in patients with hair loss.

Calcium-Dependent Eukaryotic Initiation Factor 2α Phosphatase Restores Control to Anterior Piriform Cortex Neural Circuitry after Activation by Essential Amino Acid Deficiency

Essential (dietary-indispensable) amino acids (IAA)s are vital precursors for protein synthesis; they cannot be synthesized in metazoans but must be obtained from food to survive. In sensing a reduction of an IAA, the mammalian anterior piriform cortex (APC)Ɨ is rapidly activated. The initial behavioral response is an abrupt end to an IAA deficient meal about 20 min after meal onset. IAA depletion in the APC activates the conserved eukaryotic initiation factor 2α (eIF2α) kinase, GCN2, via uncharged tRNA. GCN2 kinase activity increases levels of phosphorylated eIF2α (P-eIF2α), which blocks global protein synthesis such that APC inhibitory elements with short half-lives cannot be replaced. This results in disinhibition of this highly sensitive brain area. Following APC activation, a reduction in P-eIF2α releases the blockade on protein synthesis to allow recovery of inhibition in the circuit and complete the homeostatic response, restoring control in the APC. A role for calcium (Ca2+) in regulating P-eIF2α was explored here using Ca2+ blockers with immunohistochemistry and electrophysiology in APC brain slices. The responses to IAA depletion in the APC were Ca2+ dependent, showing a role for Ca2+ in the system. Yet, the kinase activity of GCN2 was unaffected by intracellular Ca2+ chelation. Thus, control must be accomplished by phosphatase activity. We suggest that regulation of P-eIF2α, and neuronal stability in the APC, require the activity of a Ca2+-dependent subunit, protein phosphatase1, of the phosphatase acting on P-eIF2α. This would implicate the Ca2+/calmodlin dependent calcineurin, and the constitutive repressor of eIF2 phosphorylation (PPP1R15B/CReP) after GCN2 activation in the brain.

Ribosome Profiling Uncovers Selective mRNA Translation Associated with eIF2 Phosphorylation in Erythrocyte Progenitors

To keep circulating erythrocytes between narrow boundaries, the erythroid progenitor compartment has a large expansion capacity, that is tightly regulated by environmental factors. Erythropoietin (Epo), stem cell factor (SCF) and glucocorticoids (dexamethasone; Dex) can induce a large increase of erythroblasts both in vivo and in vitro. We previously observed that this cell increase depends on control of selective mRNA translation. Translation is regulated by the interplay of translation factors and transcript-specific domains in the 5'- or 3'UTR of the mRNA, including secondary structures, protein binding sequences and upstream open reading frames (uORFs). Two translation factors are rate limiting; the cap-binding eukaryotic Initiation Factor 4E (eIF4E), and the initiator tRNA-binding eIF2. Upon heme deficiency, ER stress, or lack of amino acids, eIF2 is phosphorylated by heme regulated kinase (HRI), PKR-like endoplasmic reticulum kinase (PERK), or GCN2, respectively. Phosphorylation reduces the availability of eIF2, which leads to global inhibition of translation. However, uORF containing transcripts are preferentially translated. Until recently uORFs could be predicted from the primary structure, but it was unknown whether they were translated, nor how translation affected protein synthesis. Ribosome footprinting is a novel technique that reveals at nucleotide reslution which mRNA sequences are translated. The aim of our study is to identify transcripts that are particularly sensitive to lack of iron or ER stress due to phosphorylation of eIF2, and to establish the role of uORFs in the regulation of translation.Phosphorylation of eIF2α was induced in erythroblasts by 2.5μg/ml tunicamycin (Tm) applied for 90 minutes. Cells were exposed for 7 minutes to Harringtonin (Ht) to detect start codons, or for 5 minutes to cycloheximide (CHX) to stall elongating ribosomes. Ribosome protected fragments were isolated, sequenced, and aligned to the genome adapted from a previously published strategy (E. de Klerk, 2015 NAR 43:4408). In parallel, we performed RNA-seq of these cells. Together the data give information on (i) start codon usage through the analysis of ribosome footprints in presence of Ht, and (ii) ribosome loading through comparison of ribosome footprints in presence of CHX with transcript abundance (RNAseq). Translation of the protein coding ORF of Atf4, and its targets Ddit3 (Chop) and Ppp1R15A (Gadd34) was upregulated by Tm, as expected. The ribosome protects a sequence that extends 12nt upstream of the exit(E) position of the translated codon. We detected a satisfactory footprint periodicity, but even at high RNaseI conditions a majority of footprints extends 13 nt upstream of the codon at the E position.Overall, we observed a general repression of mRNA translation with few hypersensitive transcripts, among which the RNA binding proteins Csde1 and Pabpc1. Both Csde1 and Pabpc1 are abundantly expressed in erythroblasts. Notably, Csde1 translation was also reduced in erythroblasts from DBA patients (Horos, 2014 Blood 119:262), and we recently found that Csde1 and Pabpc1 form a complex and act in concert.When we examined the role of uORFs in the effects of tunicamycin on mRNA translation, we observed that uORFs contribute to the regulation of some, but not all transcripts. When uORFs contribute, they start at both AUG and CUG start codons.In conclusion, we obtained insight into the changes in translation control induced by eIF2 phosphorylation. The results are important to understand recovery of peripheral erythrocytes after blood loss (blood donation), but may also give insight into impaired erythropoiesis in anemias such as β-thalassemia, in which oxidative stress plays a role. DisclosuresNo relevant conflicts of interest to declare.

Neuronutrient Amino-Acid Therapy Protects Against Reward Deficiency Syndrome: Dopaminergic Key to Homeostasis and Neuroplasticity.

Willuhn et al., observed that habitual cocaine use was correlated with reductions in D2/D3 receptors linked to decreased cue activation in occipital cortex and cerebellum. Dopamine agonist therapy maintains dopamine function and is a relapse prevention tactic focused on psychoactive drug and behavioral addictions. Medication Assisted Treatment (MAT) with emphasis on glutaminergic medications fails in the long-term treatment of Reward Deficiency Syndrome Behaviors (RDS). While the careful use of "dopamine antagonist-therapy" short-term is supported, the research-based concept of "dopamine agonist therapy" in long-term is proposed. Neurogenetics and epigenetics are important in understanding treatment response and clinical outcomes. The neuro-mechanisms involving "dopamine homeostasis" are key to understanding recovery from drug and non-drug addictive behaviors. For example, patients who carry the DRD2 A1 allele (30-40 less D2 receptors) should consider Neuronutriant-Amino-Acid therapy (KB220 variants) a prevention modality. DRD2 A1 allele carriers show amplified striatal function of L-amino acid decarboxylase, prior to dopamine biosynthesis. Another example is the effect of Acute Tyrosine Phenylalanine Depletion (ATPD) on decision-making and reward found carriers with amino-acid deficiency (ATPD). They experienced attenuated reward and reduced decision-making ability as quantified by Iowa Gambling Task (IGT). Future research should be directed at asking the question; Would "dopamine agonist therapy" using KB220 variants reduce methylation and increase acetyl groups to enhance DRD2 expression especially in DRD2 A1 allele carriers and lead to increased dopamine function and a reduction of drug and non-drug seeking behaviors?

Efficacy of L-carnitine supplementation on frailty status and its biomarkers, nutritional status, and physical and cognitive function among prefrail older adults: a double-blind, randomized, placebo-controlled clinical trial.

BackgroundFrailty is a biological syndrome of decreased reserve and resistance to stressors due to decline in multiple physiological systems. Amino acid deficiency, including L-carnitine, has been proposed to be associated with its pathophysiology. Nevertheless, the efficacy of L-carnitine supplementation on frailty status has not been documented. Thus, this study aimed to determine the effect of 10-week L-carnitine supplement (1.5 g/day) on frailty status and its biomarkers and also physical function, cognition, and nutritional status among prefrail older adults in Klang Valley, Malaysia.MethodologyThis study is a randomized, double-blind, placebo-controlled clinical trial conducted among 50 prefrail subjects randomized into two groups (26 in L-carnitine group and 24 in placebo group). Outcome measures include frailty status using Fried criteria and Frailty Index accumulation of deficit, selected frailty biomarkers (interleukin-6, tumor necrosis factor-alpha, and insulin-like growth factor-1), physical function, cognitive function, nutritional status and biochemical profile.ResultsThe results indicated that the mean scores of Frailty Index score and hand grip test were significantly improved in subjects supplemented with L-carnitine (P<0.05 for both parameters) as compared to no change in the placebo group. Based on Fried criteria, four subjects (three from the L-carnitine group and one from the control group) transited from prefrail status to robust after the intervention.ConclusionL-carnitine supplementation has a favorable effect on the functional status and fatigue in prefrail older adults.

Mechanism of glyphosate control of Phelipanche aegyptiaca.

Despite its total reliance on its host plant, the holoparasite Phelipanche aegyptiaca suffers from a deficiency of aromatic amino acids upon exposure to glyphosate. The herbicide glyphosate inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), a key enzyme in the biosynthesis of aromatic amino acids. However, the functionality of the EPSPS pathway in the obligate root holoparasite Phelipanche aegyptiaca is not straightforward because of the parasite's total dependence on the host plant. Despite the importance of glyphosate as a means of controlling P. aegyptiaca, the mechanism of action of the herbicide in this parasite is not clearly understood. We characterized glyphosate control of P. aegyptiaca by using a glyphosate-resistant tomato (GRT) genotype as the host plant and evaluating the activity of EPSPS and the levels of free aromatic amino acids in the parasite. The viability of the parasite's tissues deteriorated within the first 40h after treatment (HAT) with glyphosate. In parallel, shikimate accumulation in the parasite was first detected at 24 HAT and increased over time. However, shikimate levels in the GRT host did not increase, indicating that the host was indeed glyphosate tolerant. Free phenylalanine and tyrosine levels decreased by 48 HAT in the parasite, indicating a deficiency of aromatic amino acids. The use of GRT as the host enabled us to observe, in an in situ experimental system, both endogenous EPSPS inhibition and a deficiency of aromatic amino acids in the parasite. We thus provided evidence for the presence of an active EPSPS and aromatic amino acid biosynthesis pathway in P. aegyptiaca and pinpointed this pathway as the target of glyphosate action in this parasite.

Reduction of carbamylated albumin by extended hemodialysis.

Introduction Among conventional hemodialysis (CHD) patients, carbamylated serum albumin (C-Alb) correlates with urea and amino acid deficiencies and is associated with mortality. We postulated that reduction of C-Alb by intensive HD may correlate with improvements in protein metabolism and cardiac function. Methods One-year observational study of in-center nocturnal extended hemodialysis (EHD) patients and CHD control subjects. Thirty-three patients receiving 4-hour CHD who converted to 8-hour EHD were enrolled, along with 20 controls on CHD. Serum C-Alb, biochemistries, and cardiac MRI parameters were measured before and after 12 months of EHD. Findings EHD was associated with reduction of C-Alb (average EHD change -3.20 mmol/mol [95% CI -4.23, -2.17] compared to +0.21 [95% CI -1.11, 1.54] change in CHD controls, P < 0.001). EHD was also associated with increases in average essential amino acids (in standardized units) compared to CHD (+0.38 [0.08, 0.68 95%CI]) vs. -0.12 [-0.50, 0.27, 95% CI], P = 0.047). Subjects who reduced C-Alb more than 25% were found to have reduced left ventricular mass, increased urea reduction ratio, and increased serum albumin compared to nonresponders, and % change in C-Alb significantly correlated with % change in left ventricular mass. Discussion EHD was associated with reduction of C-Alb as compared to CHD, and reduction of C-Alb by EHD correlates with reduction of urea. Additional studies are needed to test whether reduction of C-Alb by EHD also correlates with improved clinical outcomes.

Monitoring amino acid deficiencies in cancer

The demand for building blocks in cancer cells differs greatly from the ones of a normal cell. In order for a cell to divide, it must duplicate its protein content, a process that requires large en...

Metabolic adaptation of skeletal muscle to hyperammonemia drives the beneficial effects of l-leucine in cirrhosis

Increased skeletal muscle ammonia uptake with loss of muscle mass adversely affects clinical outcomes in cirrhosis. Hyperammonemia causes reduced protein synthesis and sarcopenia but the cellular responses to impaired proteostasis and molecular mechanism of l-leucine induced adaptation to ammonia induced stress were determined. Response to activation of amino acid deficiency sensor, GCN2, in the skeletal muscle from cirrhotic patients and the portacaval anastomosis (PCA) rat were quantified. During hyperammonemia and l-leucine supplementation, protein synthesis, phosphorylation of eIF2α, mTORC1 signaling, l-leucine transport and response to l-leucine supplementation were quantified. Adaptation to cellular stress via ATF4 and its target GADD34 were also determined. Activation of the eIF2α kinase GCN2 and impaired mTORC1 signaling were observed in skeletal muscle from cirrhotic patients and PCA rats. Ammonia activated GCN2 mediated eIF2α phosphorylation (eIF2α-P) and impaired mTORC1 signaling that inhibit protein synthesis in myotubes and MEFs. Adaptation to ammonia induced stress did not involve translational reprogramming by activation transcription factor 4 (ATF4) dependent induction of the eIF2α-P phosphatase subunit GADD34. Instead, ammonia increased expression of the leucine/glutamine exchanger SLC7A5, l-leucine uptake and intracellular l-leucine levels, the latter not being sufficient to rescue the inhibition of protein synthesis, due to potentially enhanced mitochondrial sequestration of l-leucine. l-leucine supplementation rescued protein synthesis inhibition caused by hyperammonemia. Response to hyperammonemia is reminiscent of the cellular response to amino acid starvation, but lacks the adaptive ATF4 dependent integrated stress response (ISR). Instead, hyperammonemia-induced l-leucine uptake was an adaptive response to the GCN2-mediated decreased protein synthesis. Sarcopenia or skeletal muscle loss is the most frequent complication in cirrhosis but there are no treatments because the cause(s) of muscle loss in liver disease are not known. Results from laboratory experiments in animals and muscle cells were validated in human patients with cirrhosis to show that ammonia plays a key role in causing muscle loss in patients with cirrhosis. We identified a novel stress response to ammonia in the muscle that decreases muscle protein content that can be reversed by supplementation with the amino acid l-leucine.

Basal endogenous losses of amino acids in protein nutrition research for swine and poultry

In this review, the definition and terminology of amino acid (AA) digestibility and ileal endogenous losses of AA (IAAend) in poultry and swine nutrition are discussed. Compared with apparent (AID) and true (TID) ileal digestibility, standardised ileal digestibility (SID) of AA is recommended for the expression of digestible AA contents of feed ingredients and for describing nutritional requirements of poultry and swine. To determine the SID of AA, total ileal flow of AA should be corrected for basal IAAend. Therefore, the measurement of basal IAAend is of great importance for the accuracy of the SID estimation in feed ingredients. The techniques for measuring basal IAAend in poultry and swine include the use of a nitrogen-free diet (NFD), a highly digestible or enzyme hydrolyzed protein diet, and the regression method. The classic method for basal IAAend determination involves the feeding of a NFD to experimental animals and measuring the ileal AA flow. This IAAend output is considered as basal IAAend, and it is assumed that the excretion of basal IAAend depends only on DM intake, regardless of dietary composition. There are criticisms with the NFD method about the abnormal physiological state induced by severe AA deficiency. Although this AA deficiency may affect the estimate of basal IAAend for dispensable AA, especially proline and glycine because of the degradation of body protein, the NFD method is still the most widely used method for basal IAAend measurements. According to the definition of basal IAAend, the NFD should be the preferred methodology in SID determination, because the basal IAAend should be only related to dry matter intake. Additionally, the SID coefficients in feed ingredients generated by NFD method are considered to be additive in a complete diet. However, the results generated from NFD method can vary among studies due to the variance in the experimental animals and diet composition. To improve the accuracy of estimating the SID of AA in feed ingredients, it is suggested that a mandatory NFD be included in individual studies to generate basal IAAend for correcting total ileal amino acid flow in determining SID of AA. In addition, research is needed to investigate the standard diet formulation of NFD.

Une cause rare de neuropathie optique : le manioc

Cassava root is a staple food for almost 500 million people worldwide. Excessive consumption of it is a rare cause of optic neuropathy. Ten patients diagnosed with cassava root related optic neuropathy were included in this retrospective study. Diagnostic criteria were a bilateral optic neuropathy preceded by significant cassava root consumption. Differential diagnoses were excluded through a neuro-ophthalmic examination, blood tests and a brain MRI. All patients had visual field examination and OCT retinal nerve fiber layer (RNFL) analysis as well as an evaluation of their cassava consumption. All patients had a bilateral optic nerve head atrophy or pallor predominantly located into the temporal sector. Visual field defects consisted of a central or cecocentral scotoma for all patients. RNFL showed lower values only in the temporal sector. Mean duration of cassava consumption prior to the appearance of visual symptoms was 22.7±11.2 years with a mean of 2.57±0.53 cassava-based meals per week. Cassava related optic neuropathy is possibly due to its high cyanide content and enabled by a specific amino-acid deficiency. Cassava root chronic consumption is a rare, underappreciated cause of optic neuropathy and its exact mechanism is still uncertain.

Abstract B08: Altering cellular differentiation and energy metabolism by the mTORC1 inhibitor NPRL2

Abstract Nitrogen permease regulator-like 2 (NPRL2) is a component of an evolutionarily conserved complex that inhibits mTORC1 (mechanistic Target Of Rapamycin Complex 1) in response to amino acid insufficiency. The NPRL2 complex functions as a GTPase activating protein against the RAG proteins, which are located on the lysosomal surface and stimulate mTORC1 activity when bound to GTP. Since the loss of NPRL2 expression is frequently associated with different types of cancers, including renal and lung, our aim is to investigate the biological function of NPRL2 in vivo and determine how this pathway can contribute to cancer growth. Previous data from our lab show that NPRL2 is required for mouse viability and that its absence significantly compromises fetal liver hematopoiesis in embryos with defective lysosomal processing of vitamin B12 and methionine/SAM homeostasis contributing to the phenotype. Here we show that loss of NPRL2 in muscle alters the differentiation of fiber-types, leading to increased size and number of glycolytic muscle fibers in the mice. Consistent with this phenotype, the NPRL2 muscle specific knockout mice show a sprinting phenotype and increased glucose utilization. These findings demonstrate that NPRL2 is able to regulate cellular differentiation patterns potentially by altering cellular methylation and represents a genetic link between amino acid metabolism and carbohydrate utilization, two hallmarks that are frequently altered in cancer. Citation Format: Paul A. Dutchak, SandiJo Terpack, Benjamin P. Tu. Altering cellular differentiation and energy metabolism by the mTORC1 inhibitor NPRL2. [abstract]. In: Proceedings of the AACR Special Conference: Developmental Biology and Cancer; Nov 30-Dec 3, 2015; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(4_Suppl):Abstract nr B08.