Deficiency in the Essential Amino Acids l-Isoleucine, l-Leucine and l-Histidine and Clinical Measures as Predictors of Moderate Depression in Elderly Women: A Discriminant Analysis Study.

Increases in depression are common in some elderly women. Elderly women often show moderate depressive symptoms, while others display minimal depressive symptoms. These discrepancies have produced contradictory and inconclusive outcomes, which have not been explained entirely by deficits in neurotransmitter precursors. Deficiency in some amino acids have been implicated in major depression, but its role in non-clinical elderly women is not well known. An analysis of essential amino acids, depression and the use of discriminant analysis can help to clarify the variation in depressive symptoms exhibited by some elderly women. The aim was to investigate the relationship of essential amino acids with affective, cognitive and comorbidity measures in elderly women without major depression nor severe mood disorders or psychosis, specifically thirty-six with moderate depressive symptoms and seventy-one with minimal depressive symptoms. The plasma concentrations of nineteen amino acids, Beck Depression Inventory (BDI) scores, Geriatric Depression Scale (GDS) scores, global cognitive scores and comorbidities were submitted to stepwise discriminant analysis to identify predictor variables. Seven predictors arose as important for belong to the group based on amino acid concentrations, with the moderate depressive symptoms group characterized by higher BDI, GDS and cognitive scores; fewer comorbidities; and lower levels of l-histidine, l-isoleucine and l-leucine. These findings suggest that elderly women classified as having moderate depressive symptoms displayed a deficiency in essential amino acids involved in metabolism, protein synthesis, inflammation and neurotransmission.

De novo histidine biosynthesis protects Mycobacterium tuberculosis from host IFN-γ mediated histidine starvation.

Intracellular pathogens including Mycobacterium tuberculosis (Mtb) have evolved with strategies to uptake amino acids from host cells to fulfil their metabolic requirements. However, Mtb also possesses de novo biosynthesis pathways for all the amino acids. This raises a pertinent question- how does Mtb meet its histidine requirements within an in vivo infection setting? Here, we present a mechanism in which the host, by up-regulating its histidine catabolizing enzymes through interferon gamma (IFN-γ) mediated signalling, exerts an immune response directed at starving the bacillus of intracellular free histidine. However, the wild-type Mtb evades this host immune response by biosynthesizing histidine de novo, whereas a histidine auxotroph fails to multiply. Notably, in an IFN-γ-/- mouse model, the auxotroph exhibits a similar extent of virulence as that of the wild-type. The results augment the current understanding of host-Mtb interactions and highlight the essentiality of Mtb histidine biosynthesis for its pathogenesis.

Diphthamide-deficiency syndrome: a novel human developmental disorder and ribosomopathy.

We describe a novel type of ribosomopathy that is defined by deficiency in diphthamidylation of translation elongation factor 2. The ribosomopathy was identified by correlating phenotypes and biochemical properties of previously described patients with diphthamide biosynthesis gene 1 (DPH1) deficiencies with a new patient that carried inactivating mutations in both alleles of the human diphthamide biosynthesis gene 2 (DPH2). The human DPH1 syndrome is an autosomal recessive disorder associated with developmental delay, abnormal head circumference (microcephaly or macrocephaly), short stature, and congenital heart disease. It is defined by variants with reduced functionality of the DPH1 gene observed so far predominantly in consanguineous homozygous patients carrying identical mutant alleles of DPH1. Here we report a child with a very similar phenotype carrying biallelic variants of the human DPH2. The gene products DPH1 and DPH2 are components of a heterodimeric enzyme complex that mediates the first step of the posttranslational diphthamide modification on the nonredundant eukaryotic translation elongation factor 2 (eEF2). Diphthamide deficiency was shown to reduce the accuracy of ribosomal protein biosynthesis. Both DPH2 variants described here severely impair diphthamide biosynthesis as demonstrated in human and yeast cells. This is the first report of a patient carrying compound heterozygous DPH2 loss-of-function variants with a DPH1 syndrome-like phenotype and implicates diphthamide deficiency as the root cause of this patient's clinical phenotype as well as of DPH1-syndrome. These findings define "diphthamide-deficiency syndrome" as a special ribosomopathy due to reduced functionality of components of the cellular machinery for eEF2-diphthamide synthesis.

Histidine and arginine modulate intestinal cell restitution via transforming growth factor-ß1.

Intestinal wound healing depends on the precise balance of restitution, proliferation, and differentiation of intestinal epithelial cells (IECs). In a previous study, we revealed that IEC proliferation was suppressed under histidine deficiency. However, the role of histidine in cell restitution is poorly understood. Meanwhile, addition of arginine to basal medium enhanced IEC restitution after wounding. However, there are no reports on whether histidine or arginine deficiency influences IEC restitution. We examined the roles of histidine and arginine in IEC restitution using the rat intestinal epithelial cell-6 (IEC-6) cell line. In the present study, the cell restitution in medium lacking histidine (ΔHis) or arginine (ΔArg) was most greatly decreased among media lacking each of the 20 intravital amino acids, compared with that in medium containing all 20 intravital amino acids (Full). TGF-ß1 is a known repair factor for cell restitution. The TGF-ß1 extracellular concentration and Tgf-ß1 mRNA level were decreased in ΔHis or ΔArg. Supplementation of 10 µM histidine to ΔHis or 50 µM arginine to ΔArg recovered the decreases in both cell restitution and TGF-ß1 extracellular concentration. Phosphorylation of Smad2, a signaling molecule for the TGF-ß pathway, was decreased in ΔHis or ΔArg. Additionally, the phosphorylation of mammalian target of rapamycin, p70 ribosomal protein S6 kinase and extracellular signal-regulated kinase were decreased in ΔHis or ΔArg. The present findings suggested that deletion of histidine or arginine led to a decrease in IEC restitution through a decrease in TGF-ß1. We revealed that histidine and arginine play important roles in IEC restitution.

Amino acid transporter SLC38A3 promotes metastasis of non-small cell lung cancer cells by activating PDK1.

BACKGROUND: Tumor metastasis is a finely-tuned pathological process coupled to metabolic reprogramming that includes both glutamine and glucose. The solute carrier SLC38A3, a member of amino acid/polyamine/organocation (APC) superfamily, is an l-glutamine transporter. It is not clear whether SLC38A3 involves the metastasis of NSCLC (non small cell lung cancer). METHODS: The scratch test and transwell assay were used to determine the ability of NSCLC to migrate. Cellular amino acids content was determined by mass spectrometry. The cellular response to glutamine/histidine deficiency was evaluated in A549 cells. The expression of SLC38A3 was assayed in clinical NSCLC and paratumor tissues by histoimmunochemistry staining. A nude mouse model of NSCLC metastasis was developed by tail vein injection of tumor cells. RESULTS: SLC38A3 was upregulated in metastatic NSCLC cells and its expression was correlated with prognosis of NSCLC patients. SLC38A3 overexpression promoted epithelial - mesenchymal transition (EMT) and migration of HCC827 and A549 human lung adenocarcinoma cells, and accelerated tumor metastasis in mice. We found that SLC38A3 decreased the cellular concentrations of glutamine and histidine, and the deficiency of glutamine or histidine activated PDK1/AKT signaling that in turn, triggered NSCLC metastasis. CONCLUSIONS: SLC38A3 activated PDK1/AKT signaling and promoted metastasis of NSCLC through regulating glutamine and histidine transport, suggesting SLC38A3 as a potential therapeutic target for treatment of NSCLC.

Histidine deficiency has a negative effect on lactational performance of dairy cows.

A 10-wk randomized complete block design experiment with 24 Holstein cows was conducted to investigate the long-term effects of feeding a His-deficient diet on lactational performance of dairy cows. Cows were blocked by days in milk, milk yield, and parity, and randomly assigned to 1 of the following 2 treatments: (1) His-adequate diet [HAD; providing +166 g/d over metabolizable protein (MP) requirements, according to the National Research Council (2001) and digestible His (dHis) supply of 68 g/d, or 2.5% of MP requirements] and (2) His-deficient diet (HDD; +37 g/d over MP requirements and dHis supply of 49 g/d, or 1.9% of MP requirements). Both HAD and HDD were supplemented with rumen-protected (RP) Met and Lys supplying digestible Met and digestible Lys at 2.4 and 2.4% and 7.2 and 7.1% of MP requirements, respectively. At the end of the 10-wk experiment, HDD was supplemented with RPHis (HDD+RPHis; total dHis supply of 61 g/d, or 2.4% of MP requirements) for an additional 9 d. Dry matter intake (DMI; 25.4 and 27.1 kg/d, standard error of the mean = 0.41), yields of milk (37.6 and 40.5 kg/d, standard error of the mean = 0.62), protein and lactose, energy-corrected milk, and milk and plasma urea-N were decreased by HDD compared with HAD. Feed and energy-corrected milk feed efficiencies, milk fat, protein and lactose concentrations, body weight, and body condition score of the cows were not affected by treatment. Apparent total-tract digestibility of dry and organic matter, crude protein, and neutral detergent fiber, and excretion of urinary N and urea-N were decreased by HDD compared with HAD. Concentration of plasma leptin tended to be decreased for HDD compared with HAD. Plasma concentrations of EAA (His, Leu, Lys, Val) and carnosine decreased and total EAA tended to be decreased in cows fed HDD compared with HAD. Muscle concentrations of free His, Leu, and Val decreased and Gly and ß-alanine tended to be increased by HDD compared with HAD. Cows fed HDD had a lower blood hemoglobin concentration than cows fed HAD. At the end of the 10-wk study, the 9-d supplementation of HDD with RPHis (i.e., HDD+RPHis) increased DMI and plasma His, and tended to increase energy-corrected milk yield and plasma carnosine, compared with HDD. In conclusion, feeding a diet deficient in dHis supplying adequate MP, digestible Met, and digestible Lys affected negatively lactational performance of dairy cows. These results confirm our previous findings that low dietary His supply can impair DMI, yields of milk and milk protein, and blood hemoglobin in dairy cows.

Translation-dependent bioassay for amino acid quantification using auxotrophic microbes as biocatalysts of protein synthesis.

Bioassay for amino acid quantification is an important technology for a variety of fields, which allows for easy, inexpensive, and high-throughput analyses. Here, we describe a novel translation-dependent bioassay for the quantification of amino acids. For this, the gene encoding firefly luciferase was introduced into Lactococcus lactis auxotrophic to Glu, His, Ile, Leu, Pro, Val, and Arg. After a preculture where luciferase expression was repressed, the cells were mixed with analytes, synthetic medium, and an inducer for luciferase expression. Luminescence response to the target amino acid appeared just after mixing, and linear standard curves for these amino acids were obtained during 15-60-min incubation periods. The rapid quantification of amino acids has neither been reported in previous works on bioassays nor is it theoretically feasible with conventional methods, which require incubation times of more than 4 h to allow for the growth of the microbe used. In contrast, our assay was shown to depend on protein translation, rather than on cell growth. Furthermore, replacement of the luciferase gene with that of the green fluorescent protein (GFP) or ß-galactosidase allowed for fluorescent and colorimetric detection of the amino acids, respectively. Significantly, when a Gln-auxotrophic Escherichia coli mutant was created and transformed by a luciferase expression plasmid, a linear standard curve for Gln was observed in 15 min. These results demonstrate that this methodology can provide versatile bioassays by adopting various combinations of marker genes and host strains according to the analytes and experimental circumstances.

Changes in integrity of the gill during histidine deficiency or excess due to depression of cellular anti-oxidative ability, induction of apoptosis, inflammation and impair of cell-cell tight junctions related to Nrf2, TOR and NF-κB signaling in fish.

This study firstly explored the possible effects of dietary histidine on structural integrity and the related signaling factor gene expression in the gills of fish. Young grass carp (Ctenopharyngodon idella) were fed with six diets containing gradual levels of histidine for 8 weeks. The results firstly demonstrated that histidine deficiency caused increases in reactive oxygen species (ROS) contents, and severe oxidative damage (lipid peroxidation and protein oxidation) in the gills of fish, which was partially due to the decreased glutathione (GSH) content and antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR)]. Further investigations indicated that histidine deficiency caused depressions of those antioxidant enzyme activities are related to the down-regulation of corresponding antioxidant enzyme genes and the related signaling factor Nrf2 mRNA levels. Meanwhile, histidine deficiency induced DNA fragmentation via up-regulation of caspase-3, caspase-8 and caspase-9 expressions that referring to the down-regulation of TOR and S6K mRNA levels. Furthermore, His deficiency down-regulated claudin-b, claudin-c, claudin-3, claudin-12, claudin-15, occludin and ZO-1 transcription in fish gills. These effects were partially related to the up-regulation of pro-inflammatory cytokines, interleukin 1ß (IL-1ß), interleukin 8 (IL-8), tumor necrosis factor-α (TNF-α) and related signaling factor nuclear factor κB P65 (NF-κB P65) mRNA levels, and the down-regulation of anti-inflammatory cytokines, interleukin 10 (IL-10), transforming growth factor ß1 (TGF-ß1) and related signaling factor IκBα mRNA levels. Excessive histidine exhibited negative effects that were similar to histidine deficiency, whereas the optimal histidine levels reversed those negative effects. Taken together, our results showed that histidine deficiency or excess impaired the structural integrity of fish gill by disrupted fish antioxidant defenses and regulating the expression of tight junction protein, cytokines, apoptosis, antioxidant enzymes, NF-κB p65, IκBα, TOR, Nrf2, Keap1 and apoptosis-related genes in the fish gills.

Loss of diphthamide pre-activates NF-κB and death receptor pathways and renders MCF7 cells hypersensitive to tumor necrosis factor.

The diphthamide on human eukaryotic translation elongation factor 2 (eEF2) is the target of ADP ribosylating diphtheria toxin (DT) and Pseudomonas exotoxin A (PE). This modification is synthesized by seven dipthamide biosynthesis proteins (DPH1-DPH7) and is conserved among eukaryotes and archaea. We generated MCF7 breast cancer cell line-derived DPH gene knockout (ko) cells to assess the impact of complete or partial inactivation on diphthamide synthesis and toxin sensitivity, and to address the biological consequence of diphthamide deficiency. Cells with heterozygous gene inactivation still contained predominantly diphthamide-modified eEF2 and were as sensitive to PE and DT as parent cells. Thus, DPH gene copy number reduction does not affect overall diphthamide synthesis and toxin sensitivity. Complete inactivation of DPH1, DPH2, DPH4, and DPH5 generated viable cells without diphthamide. DPH1ko, DPH2ko, and DPH4ko harbored unmodified eEF2 and DPH5ko ACP- (diphthine-precursor) modified eEF2. Loss of diphthamide prevented ADP ribosylation of eEF2, rendered cells resistant to PE and DT, but does not affect sensitivity toward other protein synthesis inhibitors, such as saporin or cycloheximide. Surprisingly, cells without diphthamide (independent of which the DPH gene compromised) were presensitized toward nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) and death-receptor pathways without crossing lethal thresholds. In consequence, loss of diphthamide rendered cells hypersensitive toward TNF-mediated apoptosis. This finding suggests a role of diphthamide in modulating NF-κB, death receptor, or apoptosis pathways.

Insufficient intake of L-histidine reduces brain histamine and causes anxiety-like behaviors in male mice.

L-histidine is one of the essential amino acids for humans, and it plays a critical role as a component of proteins. L-histidine is also important as a precursor of histamine. Brain histamine is synthesized from L-histidine in the presence of histidine decarboxylase, which is expressed in histamine neurons. In the present study, we aimed to elucidate the importance of dietary L-histidine as a precursor of brain histamine and the histaminergic nervous system. C57BL/6J male mice at 8 wk of age were assigned to 2 different diets for at least 2 wk: the control (Con) diet (5.08 g L-histidine/kg diet) or the low L-histidine diet (LHD) (1.28 g L-histidine/kg diet). We measured the histamine concentration in the brain areas of Con diet-fed mice (Con group) and LHD-fed mice (LHD group). The histamine concentration was significantly lower in the LHD group [Con group vs. LHD group: histamine in cortex (means ± SEs): 13.9 ± 1.25 vs. 9.36 ± 0.549 ng/g tissue; P = 0.002]. Our in vivo microdialysis assays revealed that histamine release stimulated by high K(+) from the hypothalamus in the LHD group was 60% of that in the Con group (P = 0.012). However, the concentrations of other monoamines and their metabolites were not changed by the LHD. The open-field tests showed that the LHD group spent a shorter amount of time in the central zone (87.6 ± 14.1 vs. 50.0 ± 6.03 s/10 min; P = 0.019), and the light/dark box tests demonstrated that the LHD group spent a shorter amount of time in the light box (198 ± 8.19 vs. 162 ± 14.1 s/10 min; P = 0.048), suggesting that the LHD induced anxiety-like behaviors. However, locomotor activity, memory functions, and social interaction did not differ between the 2 groups. The results of the present study demonstrated that insufficient intake of histidine reduced the brain histamine content, leading to anxiety-like behaviors in the mice.

Use of dietary feather meal to induce histidine deficiency or imbalance in dairy cows and effects on milk composition.

Removing His from a postruminal AA infusion decreases milk protein and increases milk fat content. Feather meal is an inexpensive protein source, high in rumen undegradable protein but low in His. The objective of our study was to investigate dietary feather meal as a method for creating a His deficiency or imbalance to alter milk composition. Four dietary treatments were fed for 4 wk each to 8 multiparous mid-lactation Holstein cows in a replicated 4 × 4 Latin square design. A standard-protein control diet (SP-C) was formulated to provide 3,100g/d of metabolizable protein (MP). Feather meal was added to the control diet either to replace the MP isonitrogenously (SP-FM) or to increase the MP supply to 3,484 g/d (HP-FM). As an isonitrogenous control for HP-FM, a high-protein diet (HP-C) was formulated with His-adequate protein sources to provide the same MP content as HP-FM. Dry matter intake tended to decrease when feather meal was fed. Predicted flows of digestible His, Met, and Lys, and plasma concentrations of these AA were reduced on both feather meal diets. Predicted flows of total digestible essential AA were not different between HP-FM and SP-C. We concluded that the DMI depression on HP-FM prevented an imbalance of excess AA over His, and created a deficiency of His, Met, and Lys compared with SP-C. Milk production decreased on the 2 feather meal treatments, partly explained by a tendency for DMI to decrease. Milk yield was lowest on SP-FM at 30.3 kg/d and highest on HP-C at 37.9 kg/d. Milk fat yield was not affected by diet but protein and lactose yields were both lower with feather meal. Protein yields were 860 and 998 g/d, whereas lactose yields were 1,384 and 1,561 g/d for SP-FM and HP-FM, respectively. This resulted in a higher fat content and lower protein percentage on FM diets. The ratio of solids-not-fat:fat in milk was lowest on SP-FM at 2.11 compared with 2.56 on SP-C. Adding feather meal to the diet by replacing MP isonitrogenously was more effective at lowering the solids-not-fat:fat ratio than increasing the MP content with an imbalanced protein source.

GCN2 kinase is a key regulator of fibrogenesis and acute and chronic liver injury induced by carbon tetrachloride in mice.

General control nonderepresible 2 (GCN2) is a highly conserved cytosolic kinase that modulates a complex response for coping with the stress owing to lack of amino acids. GCN2 has been recently shown to be involved in the regulation of metabolic balance and lipid degradation rate in the liver. We hypothesized that GCN2 could have a role in in hepatic fibrogenesis and in the response to acute or chronic liver injury. Activation of GCN2 in primary or immortalized human hepatic stellate cells by incubation with medium lacking the essential amino acid histidine correlated with decreased levels of collagen type I protein and mRNA, suggesting an antifibrogenic effect of GCN2. In vivo studies with Gcn2 knock-out mice (Gcn2(-/-)) showed increased susceptibility to both acute or chronic liver damage induced by CCl(4), as shown by higher alanine aminotransferase and aspartate aminotransferase activities, increased necrosis and higher inflammatory infiltrates compared with wild-type mice (WT). Chronic CCl(4) treatment increased deposition of interstitial collagen type I more in Gcn2(-/-) mice than in WT mice. Col1a1 and col1a2 mRNA levels also increased in CCl(4)-treated Gcn2(-/-) mice compared with WT mice. These results suggest that GCN2 is a key regulator of the fibrogenic response to liver injury.

Cellular plasticity enables adaptation to unforeseen cell-cycle rewiring challenges.

The fundamental dynamics of the cell cycle, underlying cell growth and reproduction, were previously found to be robust under a wide range of environmental and internal perturbations. This property was commonly attributed to its network structure, which enables the coordinated interactions among hundreds of proteins. Despite significant advances in deciphering the components and autonomous interactions of this network, understanding the interfaces of the cell cycle with other major cellular processes is still lacking. To gain insight into these interfaces, we used the process of genome-rewiring in yeast by placing an essential metabolic gene HIS3 from the histidine biosynthesis pathway, under the exclusive regulation of different cell-cycle promoters. In a medium lacking histidine and under partial inhibition of the HIS3p, the rewired cells encountered an unforeseen multitasking challenge; the cell-cycle regulatory genes were required to regulate the essential histidine-pathway gene in concert with the other metabolic demands, while simultaneously driving the cell cycle through its proper temporal phases. We show here that chemostat cell populations with rewired cell-cycle promoters adapted within a short time to accommodate the inhibition of HIS3p and stabilized a new phenotypic state. Furthermore, a significant fraction of the population was able to adapt and grow into mature colonies on plates under such inhibiting conditions. The adapted state was shown to be stably inherited across generations. These adaptation dynamics were accompanied by a non-specific and irreproducible genome-wide transcriptional response. Adaptation of the cell-cycle attests to its multitasking capabilities and flexible interface with cellular metabolic processes and requirements. Similar adaptation features were found in our previous work when rewiring HIS3 to the GAL system and switching cells from galactose to glucose. Thus, at the basis of cellular plasticity is the emergence of a yet-unknown general, non-specific mechanism allowing fast inherited adaptation to unforeseen challenges.

Alterations in plasma amino acid levels in alcoholic chronic pancreatitis in Japanese.

AIMS: Our aim was to investigate plasma amino acid levels in chronic pancreatitis (CP) patients and examine their relationship with exocrine insufficiency. METHODS: Thirty-nine patients with alcoholic CP and 20 healthy controls were examined. CP patients were divided into an exocrine normal group (n = 28) and an exocrine insufficiency group (n = 11). Selected clinical and laboratory values were compared among the three groups, and the effect of an elemental diet was observed in 6 patients of the exocrine insufficiency group. RESULTS: Total amino acid concentration was significantly higher in the control group than in the exocrine normal group and exocrine insufficiency group (p = 0.032, p = 0.020). In the exocrine insufficiency group, significant reductions in the concentrations of serum histidine and methionine were found compared with the control group and exocrine normal group (histidine: p = 0.032, p = 0.045; methionine: p = 0.043, p = 0.049). In the exocrine normal group and exocrine insufficiency group, significant elevation in the concentration of serum glutamate was found compared with the control group (p = 0.036, p = 0.029). Elemental diet improved these amino acid concentrations. CONCLUSION: Patients with CP exhibit alterations in the levels of several amino acids, such as histidine, methionine, and glutamate. These amino acid deficiencies seem to correlate with exocrine insufficiency and be improved by an elemental diet.

Snf1 promotes phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 by activating Gcn2 and inhibiting phosphatases Glc7 and Sit4.

Snf1 is the ortholog of mammalian AMP-activated kinase and is responsible for activation of glucose-repressed genes at low glucose levels in budding yeast. We show that Snf1 promotes the formation of phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha-P), a regulator of general and gene-specific translation, by stimulating the function of eIF2alpha kinase Gcn2 during histidine starvation of glucose-grown cells. Thus, eliminating Snf1 or mutating its activation loop lowers Gcn2 kinase activity, reducing the autophosphorylation of Thr-882 in the Gcn2 activation loop, and decreases eIF2alpha-P levels in starved cells. Consistently, eliminating Reg1, a negative regulator of Snf1, provokes Snf1-dependent hyperphosphorylation of both Thr-882 and eIF2alpha. Interestingly, Snf1 also promotes eIF2alpha phosphorylation in the nonpreferred carbon source galactose, but this occurs by inhibition of protein phosphatase 1alpha (PP1alpha; Glc7) and the PP2A-like enzyme Sit4, rather than activation of Gcn2. Both Glc7 and Sit4 physically interact with eIF2alpha in cell extracts, supporting their direct roles as eIF2alpha phosphatases. Our results show that Snf1 modulates the level of eIF2alpha phosphorylation by different mechanisms, depending on the kind of nutrient deprivation existing in cells.

Effects of L-histidine depletion and L-tyrosine/L-phenylalanine depletion on sensory and motor processes in healthy volunteers.

BACKGROUND AND PURPOSE: Animal studies show that histamine plays a role in cognitive functioning and that histamine H3-receptor antagonists, which increase histaminergic function through presynaptic receptors, improve cognitive performance in models of clinical cognitive deficits. In order to test such new drugs in humans, a model for cognitive impairments induced by low histaminergic functions would be useful. Studies with histamine H1-receptor antagonists have shown limitations as a model. Here we evaluated whether depletion of L-histidine, the precursor of histamine, was effective in altering measures associated with histamine in humans and the behavioural and electrophysiological (event-related-potentials) effects. EXPERIMENTAL APPROACH: Seventeen healthy volunteers completed a three-way, double-blind, crossover study with L-histidine depletion, L-tyrosine/L-phenylalanine depletion (active control) and placebo as treatments. Interactions with task manipulations in a choice reaction time task were studied. Task demands were increased using visual stimulus degradation and increased response complexity. In addition, subjective and objective measures of sedation and critical tracking task performance were assessed. KEY RESULTS: Measures of sedation and critical tracking task performance were not affected by treatment. L-histidine depletion was effective and enlarged the effect of response complexity as measured with the response-locked lateralized readiness potential onset latency. CONCLUSIONS AND IMPLICATIONS: L-histidine depletion affected response- but not stimulus-related processes, in contrast to the effects of H1-receptor antagonists which were previously found to affect primarily stimulus-related processes. L-histidine depletion is promising as a model for histamine-based cognitive impairment. However, these effects need to be confirmed by further studies.

High rate of deficiency in the amino acids tryptophan and histidine in people with wounds: implication for nutrient targeting in wound management--a pilot study.

BACKGROUND: Malnutrition resulting from inadequate protein, energy, or micronutrient intake has been identified as an independent risk factor for the development of pressure ulcers in older adult patients and is associated with increased morbidity and death. OBJECTIVE: To assess the relationship between albumin, the standard biochemical marker of nutritional adequacy, and amino acid status in people with wounds. METHODS: The authors performed tests for serum albumin, prealbumin, and amino acid profiles on 18 consecutive hospital patients with wounds and 7 patients without wounds. RESULTS: A low level of the essential amino acids tryptophan and histidine was a common finding in older people with wounds. Of the 18 consecutive wound cases, 16 (88.9%) were found to be deficient in tryptophan, histidine, or both. Moreover, levels were generally found to be lower than those in the group without wounds. The levels of all other amino acids were essentially normal for all patients. Finally, although serum albumin is often used as a surrogate marker of amino acid adequacy or nutritional status, clinically abnormal albumin had poor specificity (63.2%), poor sensitivity (60.7%), and low positive predictive value (70.8%) for the identification of a low tryptophan or histidine level. CONCLUSIONS: People with wounds are a relatively at-risk group and are likely to be overlooked in terms of micronutrient deficiencies, and these findings have important implications in terms of potential specific targeting of nutrient supplementation.

Consequences of low plasma histidine in chronic kidney disease patients: associations with inflammation, oxidative stress, and mortality.

BACKGROUND: Histidine is considered as an antiinflammatory and antioxidant factor. Histidine deficiency may contribute to an impaired nutritional state in patients with chronic kidney disease (CKD). OBJECTIVE: We aimed to investigate the consequences of plasma histidine deficiency in CKD patients. DESIGN: CKD patients (n = 325; 203 M) with a median age of 54 y (range: 19-70 y) were evaluated shortly before the beginning of renal replacement therapy. The median glomerular filtration rate was 6.4 mL/min (range: 0.8-14.5 mL/min). Nutritional status was assessed by subjective global assessment. Survival was followed for up to 60 mo; 101 patients died. RESULTS: Plasma histidine concentrations were significantly lower in CKD patients with history of cardiovascular disease, presence of plaques, protein-energy wasting, and inflammation. Plasma histidine was negatively associated with age, C-reactive protein, interleukin-6, leukocytes, thrombocytes, fibrinogen, hepatocyte growth factor, adhesion molecules, insulin-like growth factor-1, and 8-hydroxy-2'-deoxyguanosine and was positively associated with handgrip strength, hemoglobin, S-albumin and fetuin-A. A multivariate regression analysis showed that histidine concentrations were independently associated with hepatocyte growth factor, hemoglobin, and fetuin-A. In unadjusted analysis, a low histidine concentration was associated with all-cause mortality (log rank chi-square test = 8.9; P = 0.002). After adjustment for age, sex, cardiovascular disease, inflammation, diabetes mellitus, serum S-albumin, and amino acid supplementation, the association between low histidine and mortality remained significant (hazard ratio: 1.55; 95% CI: 1.02, 2.40; P < 0.05). CONCLUSION: Low plasma concentrations of histidine are associated with protein-energy wasting, inflammation, oxidative stress, and greater mortality in CKD patients.

Depiction of metabolome changes in histidine-starved Escherichia coli by CE-TOFMS.

Metabolic changes in response to histidine starvation were observed in histidine-auxotrophic Escherichia coli using a capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS)-based metabolomics technique. Prior to the analysis, we prepared an E. coli metabolome list of 727 metabolites reported in the literature. An improved method for metabolite extraction was developed, which resulted in higher extraction efficiency in phosphate-rich metabolites, e.g., ATP and GTP. Based on the results, 375 charged, hydrophilic intermediates in primary metabolisms were analysed simultaneously, providing quantitative data of 198 metabolites. We confirmed that the intracellular levels of intermediates in histidine biosynthesis are rapidly accumulated in response to a drop in histidine level under histidine-starved conditions. Simultaneously, disciplined responses were observed in the glycolysis, tricarboxylic acid cycle, and amino acid and nucleotide biosynthesis pathways as regulated by amino acid starvation.

Identification of the proteins required for biosynthesis of diphthamide, the target of bacterial ADP-ribosylating toxins on translation elongation factor 2.

Diphthamide, a posttranslational modification of translation elongation factor 2 that is conserved in all eukaryotes and archaebacteria and is the target of diphtheria toxin, is formed in yeast by the actions of five proteins, Dph1 to -5, and a still unidentified amidating enzyme. Dph2 and Dph5 were previously identified. Here, we report the identification of the remaining three yeast proteins (Dph1, -3, and -4) and show that all five Dph proteins have either functional (Dph1, -2, -3, and -5) or sequence (Dph4) homologs in mammals. We propose a unified nomenclature for these proteins (e.g., HsDph1 to -5 for the human proteins) and their genes based on the yeast nomenclature. We show that Dph1 and Dph2 are homologous in sequence but functionally independent. The human tumor suppressor gene OVCA1, previously identified as homologous to yeast DPH2, is shown to actually be HsDPH1. We show that HsDPH3 is the previously described human diphtheria toxin and Pseudomonas exotoxin A sensitivity required gene 1 and that DPH4 encodes a CSL zinc finger-containing DnaJ-like protein. Other features of these genes are also discussed. The physiological function of diphthamide and the basis of its ubiquity remain a mystery, but evidence is presented that Dph1 to -3 function in vivo as a protein complex in multiple cellular processes.