Essential Amino Acid Deficiency Research Articles

Essential amino acid infusions stimulate mammary expression of eukaryotic initiation factor 2Bε but milk protein yield is not increased during an imbalance

Essential amino acid (EAA) deficiencies and imbalances were created in lactating cows by using an infusion subtraction protocol to explore effects on milk protein yield and activity state of regulators of mRNA translation in the mammary glands. Six lactating cows on a diet of 11.2% protein were infused abomasally for 5d with saline, 563g/d of a complete EAA mix, or EAA without His, Met, Phe, or Trp in a 6×6 Latin square design. Infusion of complete and imbalanced EAA solutions increased mammalian target of rapamycin (mTOR) signaling in the mammary glands, as evidenced by higher ribosomal S6 kinase 1 (S6K1) phosphorylation compared with saline infusion. Total S6K1 abundance was decreased by imbalanced AA infusions. Except for the mixture lacking Phe, infusion of EAA, whether imbalanced or not, increased abundance of total eukaryotic initiation factor 2Bε (eIF2Bε). A correlation of 0.33 between phosphorylation state of S6K1 and total eIF2Bε abundance suggests that an mTOR-mediated upregulation of eIF2Bε translation occurred. Despite increased mTOR/eIF2Bε signaling, milk protein yields increased only with the complete EAA mixture compared with saline. Low plasma concentrations of His, Met, and Phe during their respective imbalances likely interfered with protein synthesis. Total abundance and phosphorylation state of eukaryotic initiation factor 2α were not responsible for the interference. Further study of eIF2Bε as a regulator of milk protein yield is warranted.

Effect of ultraviolet radiation, smoking and nutrition on hair.

Similar to the rest of the skin, the hair is exposed to noxious environmental factors. While ultraviolet radiation (UVR) and smoking are well appreciated as major factors contributing to the extrinsic aging of the skin, their effects on the condition of hair have only lately attracted the attention of the medical community. Terrestrial solar UVR ranges from approximately 290 to 400 nm; UV-B (290-315 nm) reaches only the upper dermis, while the penetration of UV-A (315-400 nm) into the dermis increases with wavelength. The two most important chronic effects of UVR on the skin and bald scalp are photocarcinogenesis and solar elastosis; however, the effects of UVR on hair have largely been ignored. As a consequence of increased leisure time and a growing popularity of outdoor activities and holidays in the sun, the awareness of sun protection of the skin has become important and should also apply to the hair. Besides being the single-most preventable cause of significant cardiovascular and pulmonary morbidity and an important cause of death, the association of tobacco smoking with various adverse effects on the skin and hair has also been recognized. Increasing public awareness of the association between smoking and hair loss seems to offer a good opportunity for the prevention or cessation of smoking, since the appearance of hair plays an important role in the overall physical appearance and self-perception of people. Finally, the quantity and quality of hair are closely related to the nutritional state of an individual. Normal supply, uptake, and transport of proteins, calories, trace elements, and vitamins are of fundamental importance in tissues with high biosynthetic activity, such as the hair follicle. In instances of protein and calorie malnutrition as well as essential amino acid, trace element, and vitamin deficiencies, hair growth and pigmentation may be impaired. Ultimately, important commercial interest lies in the question of whether increasing the content of an already adequate diet with specific amino acids, vitamins and/or trace elements may further promote hair growth. Unless the hair is impaired due to nutritional deficiency, there is only so much that nutrients can do to increase the size of individual hairs because hair thickness is largely genetic. Nevertheless, there are external factors that influence hair health to such a degree that micronutrients could boost hair that is suffering from these problems.

Evaluation of Amino Acid Changes and Crumb Hardness of Enriched Bread with Tench (<i>Tinca</i><i> </i><i>tinca</i><i> </i><i>L.</i>, 1758) Flesh in Turkey

The aim of the present study was to evaluate amino acid changes and crumb hardness of enriched bread with tench (Tinca tinca L., 1758) flesh. Bread was formulated with washed fish mince at the ratio of 5%, 10%, 15% and 20% and the amino acid changes and crumb hardness of breads were evaluated. Adding washed fish mince into bread resulted in a significant increase in the protein content. The amount of amino acids such as aspartic acid, glutamic acid, serine, glycine, threonine, arginine, tyrosine, cystine, phenylalanine, isoleucine, lysine, hydroxyproline and proline (p<0.05) also increased. Alanine and leucine amino acids were detectable in none of the breads. The crumb hardness value of breads also increased with the addition rate of fish flesh and over time (p<0.05). This study resulted in an alternative product (bread is rich in protein) that can be eaten without changing customs of bread consumption. This enriched bread can be helpful in solving health problems due to protein and essential amino acid deficiency.

Recent advances in the study of prolamin storage protein organization and function.

Prolamin storage proteins are the main repository for nitrogen in the endosperm of cereal seeds. These stable proteins accumulate at massive levels due to the high level expression from extensively duplicated genes in endoreduplicated cells. Such abundant accumulation is achieved through efficient packaging in endoplasmic reticulum localized protein bodies in a process that is not completely understood. Prolamins are also a key determinant of hard kernel texture in the mature seed; an essential characteristic of cereal grains like maize. However, deficiencies of key essential amino acids in prolamins result in relatively poor grain protein quality. The inverse relationship between prolamin accumulation and protein quality has fueled an interest in understanding the role of prolamins and other proteins in endosperm maturation. This article reviews recent technological advances that have enabled dissection of overlapping and non-redundant roles of prolamins, particularly the maize zeins. This has come through molecular characterization of mutants first identified many decades ago, selective down-regulation of specific zein genes or entire zein gene families, and most recently through combining deletion mutagenesis with current methods in genome and transcriptome profiling. Works aimed at understanding prolamin deposition and function as well as creating novel variants with improved nutritional and digestibility characteristics, are reported.

Effects of essential amino acid deficiency: down-regulation of KCC2 and the GABAA receptor; disinhibition in the anterior piriform cortex

The anterior piriform cortex (APC) is activated by, and is the brain area most sensitive to, essential (indispensable) amino acid (IAA) deficiency. The APC is required for the rapid (20 min) behavioral rejection of IAA deficient diets and increased foraging, both crucial adaptive functions supporting IAA homeostasis in omnivores. The biochemical mechanisms signaling IAA deficiency in the APC block initiation of translation in protein synthesis via uncharged tRNA and the general amino acid control kinase, general control nonderepressing kinase 2. Yet, how inhibition of protein synthesis activates the APC is unknown. The neuronal K(+) Cl(-) cotransporter, neural potassium chloride co-transporter (KCC2), and GABAA receptors are essential inhibitory elements in the APC with short plasmalemmal half-lives that maintain control in this highly excitable circuitry. After a single IAA deficient meal both proteins were reduced (vs. basal diet controls) in western blots of APC (but not neocortex or cerebellum) and in immunohistochemistry of APC. Furthermore, electrophysiological analyses support loss of inhibitory elements such as the GABAA receptor in this model. As the crucial inhibitory function of the GABAA receptor depends on KCC2 and the Cl(-) transmembrane gradient it establishes, these results suggest that loss of such inhibitory elements contributes to disinhibition of the APC in IAA deficiency. The circuitry of the anterior piriform cortex (APC) is finely balanced between excitatory (glutamate, +) and inhibitory (GABA, -) transmission. GABAA receptors use Cl(-), requiring the neural potassium chloride co-transporter (KCC2). Both are rapidly turning-over proteins, dependent on protein synthesis for repletion. In IAA (indispensable amino acid) deficiency, within 20 min, blockade of protein synthesis prevents restoration of these inhibitors; they are diminished; disinhibition ensues. GCN2 = general control non-derepressing kinase 2, eIF2α = α-subunit of the eukaryotic initiation factor 2.

Clinical Practice Guidelines for Healthy Eating for the Prevention and Treatment of Metabolic and Endocrine Diseases in Adults: Cosponsored by the American Association of Clinical Endocrinologists/The American College of Endocrinology and the Obesity Society Executive Summary

J. Michael Gonzalez-Campoy, MD, PhD, FACE1; Sachiko T. St. Jeor, PhD, RD2; Kristin Castorino, DO3; Ayesha Ebrahim, MD, FACE4; Dan Hurley, MD, FACE5; Lois Jovanovic, MD, MACE6; Jeffrey I. Mechanick, MD, FACP, FACN, FACE, ECNU7; Steven M. Petak, MD, JD, MACE, FCLM8; Yi-Hao Yu, MD, PhD, FACE9; Kristina A. Harris10; Penny Kris-Etherton, PhD, RD11; Robert Kushner, MD12; Maureen Molini-Blandford, MPH, RD13; Quang T. Nguyen, DO14; Raymond Plodkowski, MD15; David B. Sarwer, PhD16; Karmella T. Thomas, RD17

Metabolic responses to the deficiency of Lys, Arg, Met, or His in the mammary gland of lactating goats

To investigate lactational responses to the deficiency of individual essential amino acid (EAA), two successive 3×3 Latin square experiments were conducted in the present study with 3 lactating goats each. Animals were restricted fed a pelleted diet calculated to fulfill maintenance energy and protein requirements and the other required energy and protein were supplied through abomasal infusion of corn starch and an amino acid mixture mimic the profile of ruminal microbial protein. Deficiency of individual EAA was created by deleting it from the complete amino acid mixture. Treatments in experiment 1 were abomasal infusion of complete (C), Lys deleted (-L), and Arg deleted (-A) amino acid mixture, and those in experiment 2 were abomasal infusion of complete (C), Met deleted (-M), and His deleted (-H) amino acid mixture. Deletion of individual EAA from the complete AA mixture decreased milk yield by 39–49% and about halved milk protein yield. Milk fat content and yield were not affected. Milk fat to protein ratio numerically increased by 0.2–0.4 but was statistically insignificant (P>0.05). Deletion of individual EAA from the complete AA mixture tended to increase mammary blood flow (MBF), and the increases in the -A and -M treatments relative to that of complete AA mixture infusion were statistically significant (P<0.05). Except for Arg, arterial and venous concentrations of the deleted EAA decreased about 50% and that of Lys decreased even more than 60% (P<0.05). Mammary extraction efficiencies of all the deleted EAA were numerically increased but only that of Lys and His was significantly increased (P<0.05). Deletion of individual EAA from complete AA mixture had no significant effect of their respective mammary uptake (P>0.05) but changed the uptakes of some other measured AA (P<0.05). Deletion of Lys decreased the uptake of Thr; deletion of Arg increased that of Leu; deletion of Met increased that of Phe, Tyr, and Ser; and none of the AA uptakes was affected by deletion of His. Relative to that of complete AA mixture infusion, deleting Lys, Arg, Met, or His from the complete AA mixture numerically increased their respective mammary uptake to milk protein output ratio (U/O) by 29, 209, 100, and 82%, but only the increase of Met was statistically significant (P<0.05). For the other measured AA, deletion of Arg increased the U/O of Val, Ile, and Ser; deletion of Met increased that of Leu and Cys; deletion of His increased that of Met, Leu, Gly, and Cys (P<0.05). Influence of DMI on milk protein yield could be excluded in the present study as no feed refusal was observed. It was concluded that insufficiency of the deleted EAA as precursors for milk protein synthesis in the mammary gland was not the cause of depressed milk protein yield observed in the present study. Possible explanations for AA deficiency induced decreases in milk protein yield include depressed milk protein synthesis activities somehow incurred by the sharp decreases in blood concentrations of the deleted EAA and/or decreased conversion efficiencies of AA into milk protein in the mammary gland.

Detection of amino acid deprivation in the central nervous system

To understand the principles of amino acid deprivation sensing in the brain and its behavioral and metabolic outcomes with an emphasis on the current literature. Sensing essential amino acid (EAA) depletion occurs in the anterior piriform cortex (APC) via general control nonderepressible 2 (GCN2) binding to deacylated tRNA and subsequent glutamatergic signaling to influence behavior. Mapping of the APC output during EAA insufficiency shows axons projecting to the hypothalamus as well as other regions that are involved in feeding and locomotion. Whereas these neurocircuits are clearly important in regulating anorectic responses to an EAA-devoid diet, the propagating events and regulatory factors are still unclear. Recently, several groups examined signaling and gene expression in the arcuate nucleus and lateral hypothalamus during EAA deficiency. In these efforts, several gene products, including somatostatin, corticotrophin-releasing hormone, neuropeptide Y, agouti-related protein, and several novel targets were identified as factors involved in regulating the aversion to EAA-deficient diets. On a different note, marginal EAA deficiency in the form of methionine restriction promotes hyperphagia similar to low-protein diets, yet animals are leaner and live longer. The central mechanisms are unclear but involve sympathetic nervous signaling. How and why different degrees of EAA deficiency cause opposite changes in behavior and body composition require further study. Scientific inquiry into the central mechanism by which EAA insufficiency is sensed has identified the APC as the brain's initial EAA chemosensor. Beyond this, much remains uncertain. Future investigation into the signaling and gene expression events occurring in the hypothalamus and other brain regions is warranted.

Amino acids composition and protein quality evaluation of marine species and meals for feed formulations in cephalopods

The amino acid composition and protein levels of three species of cephalopods (Octopus vulgaris, Loligo gahi and Todarodes sagittatus), the natural diets of common octopus (O. vulgaris) and different kinds of meals were determined in order to optimise the content of these nutrients in artificial feeds. Arginine, leucine and lysine were the most abundant essential amino acids in cephalopods, while glutamate and aspartate represented the main non-essential amino acids. Arginine and leucine were the limiting amino acid in most samples, with maximum Chemical Score values for mussel (79–98 %), squid (84 %) and crustaceans (65–91 %); medium for fish (41–70 %); and minimum for meals (29–64 %). Mussel, squid, crustaceans and fish showed a high essential amino acid index according to Oser (OI: 88–99 %) suggesting a suitable amino acid balance. The protein from animal meals (fish and krill) covered all the essential amino acids except arginine and lysine in fish meal. The vegetable meal presented the worst amino acid balance (OI: 74–89 %) with several deficiencies in essential amino acids, including arginine, threonine, lysine and methionine. Supplementation with arginine or leucine and protein complementation of crustaceans and bivalves with fish or animal meal are proposed as alternatives for improving the performance of protein in feed for cephalopods.

FTO expression is regulated by availability of essential amino acids

Genome-wide association studies have revealed that single nucleotide polymorphisms in fat mass and obesity-associated transcript (FTO) are robustly associated with body mass index and obesity. Expression of Fto in the hypothalamic arcuate nucleus is bidirectionally regulated as a function of nutritional status; decreasing following a 48-h fast and increasing after 10-week exposure to a high-fat diet. Here, we utilize an in vitro approach to determine which nutrients could regulate FTO levels at a cellular level. Using mouse and human cell lines, we find that FTO levels are not influenced by serum starvation. We demonstrate, however, that both glucose and total amino-acid deprivation regulates FTO expression. In particular, we have found that FTO mRNA and protein levels are dramatically downregulated by total amino-acid deprivation in mouse hypothalamic N46 cells, mouse embryonic fibroblasts and in human HEK293 cells. The drop rate of Fto mRNA is faster than its rate of natural degradation, pointing to regulation at the transcriptional level, which is reversible upon amino-acid replacement. Strikingly, this downregulation was seen only with essential amino-acid deficiency and not nonessential amino acids. These data suggest that FTO might have a role in the sensing of essential amino-acid availability.

Incorporation of dietary nitrogen from fish meal and pea meal (Pisum sativum) in muscle tissue of Pacific white shrimp (Litopenaeus vannamei) fed low protein compound diets

Stable isotope analyses were applied to explore the relative dietary nitrogen contributions from fish meal and pea meal (Pisum sativum) to muscle tissue of Pacific white shrimp postlarvae (141 ± 31 mg) fed low protein diets having different proportions of both ingredients as the sole dietary protein sources. A negative control diet was formulated to contain 100% pea meal and six more isoproteic diets to have decreasing levels of pea meal-derived nitrogen: 95%, 85%, 70%, 55%, 40% and 0% of the initial level. Growth rates were negatively correlated to dietary pea protein inclusion due to progressive essential amino acid deficiencies (sulphur amino acids, threonine, lysine, histidine). The nitrogen turnover rate significantly increased in muscle tissue of shrimps fed diets having high levels of pea meal; however, contrary to observations from a previous study using soy protein, the relative contributions of dietary nitrogen from pea meal to shrimp muscle tissue were equal or higher than expected contributions established by the dietary formulations. Results highlight the effectiveness of stable isotope analysis in assessing the nutritional contributions of alternative ingredients for aquaculture feeds and the potential suitability of pea as a source of protein (provided the diets are nutritionally balanced)

Dietary Deficiency of Essential Amino Acids Rapidly Induces Cessation of the Rat Estrous Cycle

Reproductive functions are regulated by the sophisticated coordination between the neuronal and endocrine systems and are sustained by a proper nutritional environment. Female reproductive function is vulnerable to effects from dietary restrictions, suggesting a transient adaptation that prioritizes individual survival over reproduction until a possible future opportunity for satiation. This adaptation could also partially explain the existence of amenorrhea in women with anorexia nervosa. Because amino acid nutritional conditions other than caloric restriction uniquely alters amino acid metabolism and affect the hormonal levels of organisms, we hypothesized that the supply of essential amino acids in the diet plays a pivotal role in the maintenance of the female reproductive system. To test this hypothesis, we examined ovulatory cyclicity in female rats under diets that were deficient in threonine, lysine, tryptophan, methionine or valine. Ovulatory cyclicity was monitored by daily cytological evaluations of vaginal smears. After continuous feeding of the deficient diet, a persistent diestrus or anovulatory state was induced most quickly by the valine-deficient diet and most slowly by the lysine-deficient diet. A decline in the systemic insulin-like growth factor 1 level was associated with a dietary amino acid deficiency. Furthermore, a paired group of rats that were fed an isocaloric diet with balanced amino acids maintained normal estrous cyclicity. These disturbances of the estrous cycle by amino acid deficiency were quickly reversed by the consumption of a normal diet. The continuous anovulatory state in this study is not attributable to a decrease in caloric intake but to an imbalance in the dietary amino acid composition. With a shortage of well-balanced amino acid sources, reproduction becomes risky for both the mother and the fetus. It could be viewed as an adaptation to the diet, diverting resources away from reproduction and reallocating them to survival until well-balanced amino acid sources are found.

Apparent digestibility coefficients of several protein sources, and replacement of fishmeal by porcine meal in diets of Japanese seabass, Lateolabrax japonicus, are affected by dietary protein levels

A digestibility and a growth trial were conducted in this study respectively. Firstly, the apparent digestibility coefficients (ADC) of nutrients and energy in meat and bone meal, porcine meal (PM), hydrolysed feather meal, poultry by-products meal, fishmeal (FM), soybean meal and spray-dried blood meal were determined. In experiment 2, an 8-week growth trial was conducted to evaluate the effects of the substitution of FM by PM under the digestible ideal protein concept at two protein levels in the diets of Japanese seabass, Lateolabrax japonicus. A FM-based control diet (FM diet; FM: 320 g kg−1, crude protein: 434.9 g kg−1, crude lipid: 124.6 g kg−1) and three other diets were formulated to contain 115 g kg−1 PM and only 160 g kg−1 FM. Two diets were formulated on a crude protein basis without (PM diet) or with (PMA diet) essential amino acid (EAA) supplementation respectively. A low-protein diet was designed (LPMA diet, crude protein: 400.9 g kg−1, crude lipid: 96.3 g kg−1) with the same level of FM and PM but with the same digestible protein/ digestible energy and EAA profile as the FM diet. The results showed that nitrogen and total amino acid digestibility of the tested ingredients were ranged from 85.6% to 95.5% and from 87.6% to 95.5% respectively. Apparent digestibility coefficients of protein for FM and PM were 91.2% and 95.9% respectively. In the growth trial, the weight gain rate and feed conversion ratio of fish fed the PMA diet did not show a significant difference from those of the control group, but were significantly higher than those of the PM and LPMA groups (P<0.05). Growth was related linearly to lysine and methionine intakes. It was shown that PM could be utilized in the Japanese seabass diet up to 115 g kg−1 to replace about 160 g kg−1 of FM protein under an ideal protein profile. Essential amino acid deficiency (diet PM) or a lower protein level despite having an ideal amino acid profile (diet LPMA) could not support the optimal growth of Japanese seabass.

Nutritional quality and protein value of exotic almonds and nut from the Brazilian Savanna compared to peanut

The aim of this study was to determine the nutritional quality and protein value of the baru almond, pequi almond, and cerrado cashew nut compared to the peanut. We determined the proximate chemical composition, mineral content, and amino acid profile. A biological assay was carried out to assess the protein value, by net protein ratio (NPR), relative net protein ratio (RNPR), and protein digestibility-corrected amino acid score (PDCAAS) indexes. We found that the exotic almonds and the nut are rich in proteins (22.7–29.9g/100g), lipids (41.9–50.0g/100g), fibres (baru and pequi almonds, around 10.0g/100g), iron and zinc (4.3–7.4mg/100g). Baru almond's protein did not show deficiency in essential amino acids and lysine was the first limiting amino acid in the proteins of the pequi almond and cerrado cashew nut. The baru almond showed a RNPR of 86%, similar to that of the cerrado cashew nut (78%), but higher than that of the peanut (72%) and of the pequi almond (54%). The PDCAAS value of the baru almond (91%) was the highest and cerrado cashew nut and peanut presented similar values of this index (82%), which were higher than that of the pequi almond (55%). The baru almond has the highest protein quality, but the cerrado cashew nut and peanut are sources of good quality protein, too. We recommend the inclusion of these exotic foods in healthy diets and in food industry, and the baru almond and cerrado cashew nut as sources of complementary protein.

Autophagic-lysosomal pathway functions in the masseter and tongue muscles in the klotho mouse, a mouse model for aging

Klotho mutant (kl/kl) mice, a type of short-lived mouse models, display several aging-related phenotypes. To investigate whether the atrophy of skeletal muscles is induced in these mice via activation of the ubiquitin-proteasomal pathway and/or the autophagic-lysosomal pathway through an alteration of insulin/IGF-I signaling, we analyzed the activity of the two pathways for protein degradation and components of the insulin/IGF signaling pathway in their skeletal muscles. The masseter, tongue, and gastrocnemius muscles in kl/kl showed marked reductions in muscle weight and in myofiber diameter compared with +/+. The autophagic-lysosomal pathway in kl/kl was activated in the masseter and tongue, but not in the gastrocnemius, compared with that in +/+, whereas the ubiquitin-proteasomal pathway in these three muscles of kl/kl was not altered. No marked difference in the phosphorylation levels of insulin/IGF-I signaling components, such as insulin/IGF-I receptor, Akt, and FoxO in three muscles studied were found between kl/kl and +/+, but the phosphorylation levels of signaling component at the downstream of mTOR such as 4E-BP1 and p70 S6K were suppressed in the masseter and tongue of kl/kl compared with +/+. Deficiency of essential amino acids is reported to activate the autophagy-lysosomal pathway through the down-regulation of mTOR, not through IGF-Akt-FoxO. The masseter and tongue seem to be more actively moved than limb muscles in kl/kl, because they are essential for survival activities such as mastication, swallowing, and respiration. Thus, the deficiency of amino acid by the active movement of the masseter and tongue seems to stimulate the autophagic-lysosomal pathway via the down-regulation of mTOR signalling pathway.

The sensing of essential amino acid deficiency in the anterior piriform cortex, that requires the uncharged tRNA/GCN2 pathway, is sensitive to wortmannin but not rapamycin

Animals detect and reject their first essential/indispensable amino acid (IAA) deficient meal within 20 min; this IAA sensing requires an intact anterior piriform cortex (APC). In the biochemical responses to IAA deficiency in the APC we have shown that: uncharged tRNA is the primary sensor; IAA transport is increased; and signaling, including the extracellular-regulated kinase (ERK1/2), is activated. The mammalian target of rapamycin (mTOR) is a potential AA sensor and is regulated by AA transport. Previously, the inhibitors, rapamycin for mTOR, wortmannin for phosphoinositide 3 kinase (PI3K) and PD98059 for ERK, each blocked the upregulation of the System A transporter in IAA depleted APC neurons. Here we injected these same inhibitors into the APC and measured intake of an IAA deficient diet. Rapamycin had no effect on the rejection of the IAA deficient diet, but wortmannin increased ERK activation and intake of the deficient diet before 40 min and PD98059 acted after 40 min to increase the second meal. While the specific wortmannin target involved in blocking the behavioral response remains unclear, we conclude that mTOR is dispensable for sensing IAA deficiency in the APC, and that ERK is associated with the secondary learned responses to IAA deficient diets.

Escherichia coli, an Intestinal Microorganism, as a Biosensor for Quantification of Amino Acid Bioavailability

In animal diets optimal amino acid quantities and balance among amino acids is of great nutritional importance. Essential amino acid deficiencies have negative impacts on animal physiology, most often expressed in sub-optimal body weight gains. Over supplementation of diets with amino acids is costly and can increase the nitrogen emissions from animals. Although in vivo animal assays for quantification of amino acid bioavailability are well established, Escherichia coli-based bioassays are viable potential alternatives in terms of accuracy, cost, and time input. E. coli inhabits the gastrointestinal tract and although more abundant in colon, a relatively high titer of E. coli can also be isolated from the small intestine, where primary absorption of amino acids and peptides occur. After feed proteins are digested, liberated amino acids and small peptides are assimilated by both the small intestine and E. coli. The similar pattern of uptake is a necessary prerequisite to establish E. coli cells as accurate amino acid biosensors. In fact, amino acid transporters in both intestinal and E. coli cells are stereospecific, delivering only the respective biological l-forms. The presence of free amino- and carboxyl groups is critical for amino acid and dipeptide transport in both biological subjects. Di-, tri- and tetrapeptides can enter enterocytes; likewise only di-, tri- and tetrapeptides support E. coli growth. These similarities in addition to the well known bacterial genetics make E. coli an optimal bioassay microorganism for the assessment of nutritionally available amino acids in feeds.

Adaptational modification of serine and threonine metabolism in the liver to essential amino acid deficiency in rats

It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient diet, but the underlying mechanisms including related gene expressions or serine and threonine concentrations in liver remained to be elucidated. We fed rats lysine or valine deficient diet for 4 weeks and examined the mRNA expressions of serine synthesising (3-phosphoglycerate dehydrogenase, PHGDH) and serine/threonine degrading enzymes (serine dehydratase, SDS) in the liver. Dietary deficiency induced marked elevation of hepatic serine and threonine levels associated with enhancement of PHGDH mRNA expression and repression of SDS mRNA expression. Increases in plasma serine and threonine levels due to essential amino acid deficiency in diet were caused by marked increases in hepatic serine and threonine levels. Proteolytic responses to the amino acid deficiency may be lessened by storing amino radicals as serine and inducing anorexia through elevation of threonine.

Effects of dietary essential amino acid deficiencies on immunological variables in broiler chickens.

Two experiments were conducted to determine the effects of essential amino acid deficiencies on several immunological variables in male broiler chickens. Essential amino acids were classified into five groups as follows: S-containing amino acids (SAA; methionine + cysteine), aromatic amino acids (AAA; phenylalanine + tyrosine), branched-chain amino acids (BCAA; isoleucine + leucine + valine), arginine plus lysine (Arg + Lys), and other essential amino acids (OEAA; glycine + serine + histidine + threonine + tryptophan). Chickens were fed ad libitum from 10 to 24 d of age on a control diet or amino-acid-deficient diets formulated to contain each amino acid group at 50% and 16% (Expt 1) at 50% (Expt 2) of the recommended requirements (National Research Council, 1984). Effects of feed consumption on immune responses were also considered by setting pair-feeding (Expt 1) or restricted-feeding (Expt 2) groups fed on the control diet. In Expt 1, changes in lymphoid organ weights varied with the type and degree of deficiency of amino acid groups, with BCAA deficiency markedly decreasing weights. The haemagglutinin titres against sheep erythrocytes did not change in any amino-acid-deficient chickens except that the titres were lower in chickens fed on the 50%- and 16%-BCAA diets as compared with their pair-fed counterparts. In Expt 2, the splenocyte proliferative response to concanavalin A was higher in the chickens fed on the BCAA- and Arg + Lys-deficient diets and lower in chickens fed on the SAA- and AAA-deficient diets than the control chickens, independent of feed consumption. These results suggest that the effects of specific amino acid deficiencies on immune responses cannot be generalized, and that BCAA have the greatest potential to modulate immune responses among the amino acids in chickens.

Necrolytic migratory erythema without glucagonoma in a patient with short bowel syndrome

Necrolytic migratory erythema (NME) is an uncommon inflammatory dermatosis with a distinctive clinical and histological appearance. It shows irregular erythema, bullae, erosion, crusts and pigmentation. While it is typically associated with glucagonoma, some cases of NME without glucagonoma have been reported. Herein, we report a case of necrolytic migratory erythema associated with malabsorption 30 years after ileocolectomy. She presented erosive erythema with scale or partly flaccid bullae on her intergluteal cleft, buttock and extremities. Her laboratory data revealed essential amino acid deficiency and a slightly decreased serum zinc level, while her plasma glucagon level was low. With diagnosis of non-glucagonoma-associated NME with malabsorption due to short-bowel syndrome, she was treated and improved by i.v. amino acid supplement. Histological findings of NME include necrotic changes of keratinocytes in the upper epidermis, proliferation of those in the lower epidermis and inflammatory cell infiltration of upper dermis. We also examined the expression pattern of epidermal keratins (K6, K10) and Ki-67, one of the markers of proliferative activity, to assess the proliferation and differentiation of keratinocytes in a NME lesion by immunostaining. The findings with these immunostainings support the characteristics of HE-staining, and suggest hyponutrition may induce changing differentiation/proliferation of keratinocytes.