A porcine animal model to mimic the restart of enteral nutrition (refeeding-model)

With the aim towards establishing an animal model of total parenteral nutrition (TPN), 12 piglets aged 9 weeks (mean body weight 21 kg) were surgically provided with central venous catheters. Six piglets were nourished parenterally with the objective to reach a 14-d period of TPN; the other six piglets served as control and were fed normally. Only one animal from each group could be monitored over the whole period. Nine piglets were euthanised on d 13 and one on d 12. No animal showed fever or signs of septicaemia during the study. The levels of Ca, Mg, Na and P in the blood were within the normal range as were those for blood glucose and plasma creatinine. Symptoms of the TPN included: transient diarrhoea, occasional appearance of faecal blood and occasional absence of defecation. A reduced small intestine length and altered mucosal morphology and function were observed. One animal showed bile stasis at the end of the study. All TPN animals showed a remarkably high level of blood urea early in the morning. The intestinal symptoms observed may resemble the human situation during TPN. However, due to the fast growth rate, pigs aged 9 weeks have higher nutrient requirements per kg body weight. Consequently, the osmolality of the nutrient solution was necessarily high. Whether the significantly higher blood urea observed in the TPN group reflected a catabolic metabolism during the starving period at night-time could not be conclusively shown. Alternatively, it could reflect a slower growth rate and a resulting quantitative excess of amino acids (AA), or could have been the consequence of a suboptimal AA composition. A permanent infusion would be favourable in order not to overcharge the capacity for glucose uptake and amino acid metabolism during the infusion.     

Human branched-chain L-amino acid aminotransferase: Activity and subcellular localization in cultured skin fibroblasts

Summary Assay conditions for measurement of human skin fibroblast branched-chain L-amino acid aminotransferase activity were established and applied to studies on subcellular distribution and kinetic properties of the enzyme. Digitonin fractionation of cultured cells revealed that the aminotransferase activity was mainly (at least about 95%) associated with mitochondrial citrate synthase activity. As tested with L-leucine, activity of the enzyme against amino group acceptors (forward reaction) was in the order 2-oxoglutarate branched-chain > straight-chain 2-oxo acids (C₃-C₈). With 4-methyl-2-oxopentanoate, activity against amino group donors (reverse reaction) was in the order L-glutamate branched-chain > straight-chain (C₂-C₆) and other L-amino acids. The data suggest that, in human fibroblasts, isoenzyme type I resides within the mitochondrial space. Possible implications for the metabolism of branched-chain compounds are discussed.     

Plasma arginine correlations in trauma and sepsis

Summary. Arginine (ARG) is an amino acid (AA) with unique properties and with a key-role in the metabolic, immune and reparative response to trauma and sepsis. This study has been performed to characterize the correlations between plasma levels of ARG, of other AA and of multiple metabolic variables in trauma and sepsis. Two-hundred and sixty-three plasma amino-acidograms with a large series of additional biochemical and blood variables were obtained consecutively in 9 trauma patients who developed sepsis, undergoing total parenteral nutrition with dextrose, fat and a mixed AA solution containing 10.4% arginine. ARG was low soon after trauma, then it increased with increasing distance from trauma and with the development of sepsis. ARG was also directly related to the AA infusion rate (AAIR) and for any given AAIR, was lower after trauma than after the development of sepsis. ARG was also related directly to the plasma levels of most of the other AA, the best correlation being that with lysine (r² = 0.81, p < 0.001). These correlations were often shifted downwards (showing lower ARG for any given level of the other AA) in measurements performed after trauma, compared to those performed after development of sepsis; this effect was more pronounced for the correlations with branched chain AA. Correlations between ARG and non-AA variables were not particularly relevant. The best simultaneous correlates of ARG, among variables involved in plasma ARG availability, were citrulline level, AAIR and urinary 3-methylhistidine excretion (accounting for the effect of endogenous proteolysis) (multiple r² = 0.70, p < 0.001). Plasma ornithine (ORN), the AA more specifically linked to ARG metabolism, correlated with AAIR better than ARG and, for any given AAIR, was lower after trauma than after the development of sepsis. Correlations of ORN with other AA levels were poorer than those found for ARG, however ORN was directly related to white blood cell and platelet count, fibrinogen, transferrin, cholesterol and many AA clearances. These data show that changes in ARG in trauma and sepsis are correlated with changes in other AA and, within these correlations, reconfirm a tendency to lower ARG in trauma compared to sepsis. The strong correlation with lysine warrants a deeper assessment of the practical implications of interdependency between these two AA. The data also suggest that changes in plasma ORN in trauma and sepsis may reflect adequacy of AA substrate to support acute-phase and other synthetic processes.     

The role of glutamine in the immune system and in intestinal function in catabolic states

Summary Glutamine is designated a non-essential amino acid: however, evidence is accumulating that glutamine becomes essential when catabolic conditions prevail.It has been established that glutamine is an important fuel for lymphocytes and macrophages, even when resting. Plasma and muscle glutamine concentrations are decreased after trauma such as burns, major surgery, and in sepsis. The effectiveness of the immune system is decreased after trauma: this may be due, in part, to the decrease in plasma glutamine concentrations.Most studies on sepsis in humans have shown plasma glutamine concentrations to bedecreased: this may be due to an increased rate of utilization of glutamine by lymphocytes and macrophages during proliferation or phagocytosis. In contrast, several studies on rats showincreased plasma glutamine levels in sepsis. A species difference in the way in which glutamine is metabolised could be the main reason for the conflicting results. Other contributory factors could be diurnal variation and timing of sample collection.A substantial amount of dietary glutamine is taken up by intestinal cells. When the supply of glutamine via the diet is decreased, glutamine is taken up from the circulation by the intestine. In total parenteral nutrition (TPN) sepsis can sometimes occur because the gut is rested, leading to villous atrophy and increased gut mucosal barrier permeability. There is now a move towards the use of enteral nutrition in preference to TPN. Provision of exogenous glutamine has had beneficial effects in humans and animals, particularly in improving intestinal function. The safety and efficacy of glutamine administration to humans is discussed in detail.     

Plasma and Red Blood Cell Fatty Acids in Peroxisomal Disorders

The demonstration of abnormal levels of fatty acids or plasmalogens in plasma or red blood cells is key to the diagnosis of peroxisomal disorders. We report the levels of 62 fatty acids and plasmalogens in patients with X-linked adrenoleukodystrophy (X-ALD), Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), both at baseline and after dietary interventions. Lorenzo's Oil therapy in X-ALD normalizes the levels of saturated very long chain fatty acids in plasma, but leads to reduced levels of omega 6 and other omega 3 fatty acids, and requires monitoring and appropriate dietary supplements. Patients with ZS, NALD and IRD have reduced levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) which can be normalized by the oral administration of microencapsulated DHA and AA.     

The effects of starvation and refeeding on plasma amino acid levels in carp, Cyprinus carpio L., 1758

Plasma amino acid (AA) levels of carp, Cyprinus carpio L., 1758, were analysed after various periods of starvation as well as after 12 days of refeeding. The levels were compared to control groups, which had been previously fasted for 24 h. A positive correlation between dietary and plasma essential amino acid (EAA) concentrations was observed in all of the control groups.
The effect of starvation on the dynamics of AA concentration was different according to the period of starvation. Fasting already produced a decrease of total α-AA levels at 2 days, and these low levels were maintained until 5 and 8 days. These short periods of fasting affected the levels of EAA (especially branched-chain AA) more than those of non-essential amino acids (NEAA). The only AA that increased was Ala, which rose at 5 days of starvation, surpassing the levels of the control group. These high levels were maintained until 19 days of starvation.
A different situation was observed at 19 days, when an important increase of total α-AA levels was produced, the branched-chain AA being the most notable among EAA and Glu/Gln among NEAA. Later, at 50 days of starvation, total α-AA, EAA (except Leu and Ile) and NEAA decreased.
After 50 days of starvation, 12 days of refeeding did not modify the levels of EAA and NEAA, and their concentrations were lower than those of the control group, which presented an increase of total AA at this time. The differences observed on the changes of individual AA levels are discussed.     

Effect of recombinant human interleukin 1β (rhIL-1β) on amino acid flux in the isolated perfused rat liver

Summary We studied the effect of recombinant human IL-1 (rhIL-1) on hepatic amino acid (AA) flux in the isolated perfused rat liver model. Two experimental groups were used — a control group (n = 5) and a rhIL-1-treated group (n = 5). IL-1 was added to the perfusate in two successive boluses of 0.1µg and 0.9µg, respectively 35 min (final concentration 0.67 ng/ml) and 60 min (6 ng/ml) after beginning the perfusion. In the IL-1 treated group, a reduction in flux was observed for only three AA, alanine, phenylalanine and serine. Glucose and urea production in the IL-1-treated group was slightly but not-significantly lower than in the controls.rhIL-1 thus has only minor direct effects on AA flux and gluconeogenesis in the liver and cannot therefore be held responsible for the increase in hepatic amino acid uptake during stress.     

富含谷氨酰胺和支链氨基酸的肠外制剂对创伤大鼠的效用

研究普通氨基酸注射液 (17AA)与富含谷氨酰胺及支链氨基酸注射液 (2 0AA)对创伤大鼠的营养效用。以Wistar大鼠为创伤模型 ,分别输注两种配方的氨基酸注射液 ,以日立L - 85 0 0氨基酸自动分析仪测定动物血浆游离氨基酸 ,并测定创伤处海绵内羟脯氨酸含量。结果显示创伤后大鼠血浆牛磺酸、谷氨酸、谷氨酰胺和支链氨基酸含量较术前下降 ,但 2 0AA组血浆氨基酸恢复优于 17AA组 ,创伤处海绵内羟脯氨酸含量 2 0AA组显著高于 17AA组 (1.2 9± 0 .2 1vs 0 .83± 0 .16mg/块海绵 ,P <0 .0 5 )。提示 ,创伤后给予富含谷氨酰胺和支链氨基酸的营养制剂能提高血浆氨基酸浓度并有利于创伤的恢复     

Individual day-to-day variations in plasma amino acid levels in healthy persons

Summary Fasting plasma levels of the large neutral amino acids (LNAA;l-forms) andl-tryptophan (TRP) ratios were determined in thirteen healthy volunteers (7 males, 6 females) on five consecutive mornings, and the same procedure was repeated for each individual three months later. We found characteristic overall ranges for the parameters studied, and, in addition to certain differences between the sexes, considerable inter- and intraindividual daily variations. Although the individuals showed statistically identifiable mean levels that, in the majority of subjects, were maintained over a period of three months, it is concluded that the degree of intraindividual variability does not allow us to regard a single value as characteristic for a given individual. This should be borne in mind in particular in follow-up studies of plasma LNAA in patients with, for example, depressive disorders.     

The relationship between plasma cholesterol,amino acids and acute phase proteins in sepsis

Summary. The purpose of the study was to correlate degree of hypocholesterolemia to changes in plasma levels of amino acids and other metabolic variables in severely injured septic patients. Measurements included plasma cholesterol, full amino-acidograms, acute phase proteins, complementary variables and blood cell counts. The Fischer plasma molar amino acid ratio (leucine+isoleucine+valine)/(phenylalanine+tyrosine) was calculated. Plasma cholesterol for all measurements (n=145) was 3.1±1.1mmol/L and, upon entry in the study, it was correlated inversely with sepsis severity score (p<0.05). Along the clinical course, changes in cholesterol were clearly paralleled by opposite changes in C-reactive protein, which was the best correlate of cholesterol (r²=0.70, p<0.0001). Furthermore cholesterol was inversely related to phenylalanine, fibrinogen, lactate and white blood cell count, and directly to the Fischer molar amino acid ratio, cystathionine, methionine, glycine and transferrin (r² between 0.36 and 0.15, p<0.0001 for all). Within this pattern of correlations, cholesterol was also directly related to alkaline phosphatase, which accounted for the effect of cholestasis, when present. For any given value of the other variables, cholesterol increased significantly with increase in alkaline phosphatase (p<0.0001). C-reactive protein (CRP, mg/dl) and alkaline phosphatase (ALKPH, U/L) together in the same regression explained 79% of the variability of cholesterol (CHOL, mmol/L): CHOL=5.90–0.74[Log_eCRP]+0.004[ALKPH]; multiple r²=0.79, p<0.0001. Inclusion in this regression of other variables did not increase the r². By using only amino acid variables, the best fit was provided by a regression including the Fischer ratio and cystathionine, which explained 55% of the variability of cholesterol (multiple r²=0.55 p<0.0001), and this result was not improved by the inclusion of other amino acids. These data show that severity of hypocholesterolemia in sepsis is quantifiably related to changes in plasma amino acids, and to severity of acute phase response and metabolic decompensation. More study is needed to understand whether hypocholesterolemia in sepsis has only diagnostic or prognostic implications, or that it may also contribute actively to worsening of the disease.     

Effect of regular training on the myocardial and plasma concentrations of taurine andα-amino acids in thoroughbred horses

Summary Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 ± 1.2mol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 ± 0.9 and 7.7 ± 0.69mol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1mol/g wet weight (4.6 ± 0.25 and 1.7 ± 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 ±1.1mol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.     

The profile of free amino acids in latent fingerprint of healthy and beta-thalassemic volunteers

The aim of the present work is to apply a non-invasive test, using thumb fingerprint residue analysis, for detection of beta-thalassemia (β-Thal). The relative percentages of free amino acids (AA) in the latent fingerprint of β-Thal patients and healthy subjects were compared. The sample included 24 β-Thal patient and 24 healthy subjects, aged 5–10 years old. Twenty-three AA plus ammonia were analyzed by a sensitive high-performance liquid chromatographic method with fluorescence detection. The profile of AA was calculated based on the percentage of relative amount of each AA to serine (Ser) as it found to be the predominant peak. The statistical and chromatographic profiles of β-Thal patients were characterized by significant decrease of ornithine, lysine, and zero tyrosine, with significant increase of ammonia, and proline. Other amino acids that exist in low ratios were estimated statistically for significance changes. The relative percentages of each AA of healthy subjects were approximately constant. For this reason, these mentioned AA were assigned as major fingerprint markers of β-Thal.     

Targeted metabolomics reveals altered oxylipin profiles in plasma of mild cognitive impairment patients

Introduction and objective

Mild cognitive impairment (MCI) is considered to be a prodromal stage of Alzheimer’s disease (AD), which is the most common type of dementia. Although MCI is a common clinical manifestation in the elderly, the pathology and molecular mechanisms are not fully understood. Oxylipins are a major class of lipid-derived signaling mediators, which have been implicated in the pathology of MCI and AD. In this study, we investigated the changes of oxylipin profiles in plasma of MCI patients.

Methods

We performed a targeted liquid chromatography—mass spectrometry analysis to quantify 49 oxylipins and 4 polyunsaturated fatty acids in plasma samples of 60 clinically diagnosed MCI patients and 56 age- and gender-matched cognitively normal individuals.

Results

We found that the levels of linoleic acid (LA) and 7 oxylipins were significantly altered in MCI patients when compared to the controls. Notably, oxylipins synthesized through 5-lipoxygenase (5-LOX) and cytochrome P450 (CYP450) pathways of arachidonic acid (AA) or LA were elevated in MCI patients, which is in accordance with previously reports that oxylipins from the same pathways were increased in the brain tissues of AD and MCI patients, suggesting the potential correlations of oxylipin changes in 5-LOX and CYP450 pathways between the peripheral blood and the brain tissues in MCI and AD patients.

Conclusion

This study is the first report on plasma oxylipin profiles in MCI patients, and disease-relevant changes of oxylipins and oxylipin pathways were identified. The results represent potentially an efficient method to monitor certain oxylipin changes in the brain tissues of MCI or AD patients.

     

Plasma free amino acid profiles and nutrition proteins in chronic renal failure; effect of dialysis treatment

Summary A well preserved nutritional status is beneficial in chronically uremic patients for slowing the pace of deterioration of renal function, and delaying the need for dialysis therapy. The purpose of this study was to assess the nutritional profile of 10 patients in a steady state of advanced CRF, and of 15 patients with terminal renal failure immediately prior to their first hemodialysis session (J0), and 7, 14, 45, 60, days post start of dialysis. Patients were 18 to 65 years old with total plasma proteins 60g/1. Plasma concentrations of amino acids, nutrition proteins, apolipoproteins A1, and B were evaluated. Non inflammatory reaction was evaluated by determination of alpha-1-acid glycoprotein, and C reactive protein. The data (mean ± 1 SD) were compared with mean values of 15 healthy individuals.     

L-Tyrosine oxidative metabolism byStreptomyces aureofaciens

Summary L-Tyrosine metabolism found in normal mammalian system via homogentisic acid was investigated inStreptomyces aureofaciens S-834 as L-tyrosine was shown to possess the stimulatory role in the production of chlortetracycline antibiotic. L-Tyrosine as well as the substrates of the intermediary oxidative enzymes-p-hydroxyphenylpyruvate (p-HPPA) hydroxylase and homogentisate (HGA) oxygenase were incubated with the washed, resting cells of the culture and by adding sodium diethyldithiocarbamate and,-dipyridyl, the specific inhibitors of these enzymes to the culture, the oxidative intermediates-p-HPPA and HGA were blocked from further utilisation and were accumulated and isolated by extraction with the appropriate solvent system. The intermediates consisted of keto acids and aromatic phenolic acids were separated by adsorption and elution on silica gel and sephadex gel columns. p-HPPA and acetoacetate (AA) were identified as keto acids by obtaining their 2,4-dinitrophenylhydrazone derivatives. HGA as well as p-HPPA were identified as phenolic acids along with HGA lactone using diazotized reagents. These investigations helped to establish L-tyrosine oxidative pathway inStreptomyces aureofaciens via p-HPPA, HGA and AA leading to the biosynthesis of chlortetracycline antibiotic.     

Neutrophils as a source of branched-chain,aromatic and positively charged free amino acids

Neutrophils release branched-chain (valine, isoleucine, leucine), aromatic (tyrosine, phenylalanine) and positively charged free amino acids (arginine, ornithine, lysine, hydroxylysine, histidine) when adhere and spread onto fibronectin. In the presence of agents that impair cell spreading or adhesion (cytochalasin D, fMLP, nonadhesive substrate), neutrophils release the same amino acids, except for a sharp decrease in hydroxylysine and an increase in phenylalanine, indicating their special connection with cell adhesion. Plasma of patients with diabetes is characterized by an increased content of branched-chain and aromatic amino acids and a reduced ratio of arginine/ornithine compared to healthy human plasma. Our data showed that the secretion of neutrophils, regardless of their adhesion state, can contribute to this shift in the amino acid content.

Abbreviations: BCAAs: branched-chain amino acids; Е2: 17β-estradiol; LPS: lipopolysaccharide from Salmonella enterica serovar Typhimurium; fMLP: N-formylmethionyl-leucyl-phenylalanine.     

Effects of branched-chain amino acids on plasma amino acids in amyotrophic lateral sclerosis

Summary Although the cause of amyotrophic lateral sclerosis (ALS) remains unknown, biological findings suggest that the excitatory amino acid glutamate contributes to the pathogenesis of ALS. In previous studies of ALS, the therapeutic effect of the branched-chain amino acids (BCAAs) leucine, valine and isoleucine has been evaluated. The present study aimed at investigating the acute effect of BCAAs on plasma glutamate levels in ALS patients. Following two oral doses of BCAAs, significantly increased plasma levels were seen for valine (500%), isoleucine (1,377%) and leucine (927%), however the plasma level of glutamate was not affected. The plasma level of several other amino acids (tryptophan, tyrosine, phenylalanine and methionine) were found decreased after oral BCAAs, which may indicate a diminution in the rate of degradation of muscle protein and/or an increase in tissue disposal of amino acids.     

Prediction of amino acid profiles in feed ingredients:: Genetic algorithm calibration of artificial neural networks

Linear regression (LR) has been used to predict the amino acid (AA) profiles of feed ingredients, given proximate analysis (PA) input. Artificial neural networks (ANN) have also been trained to predict AA levels, generally with better results. Past projects have indicated that ANN more effectively identified the complex relationship between nutrients and feed ingredients than did LR. It was shown that the maximum R² value, a measurement of the amount of variability explained by the model, was highest when a general regression neural network (GRNN) with iterative calibration (GRNNIT) was used to train the ANN. This was in comparison to LR, Ward backpropagation (WBP) or 3-layer backpropagation (3BP) architectures. The current study investigated the potential of a new, advanced method of calibration using the genetic algorithm (GA) to optimize GRNN smoothing values. Calibration of an ANN allows the neural network to generalize well and therefore provide good results on new data. A GRNN architecture (NeuroShell 2^® Software) with GA calibration (GRNNGA) was used to train an ANN to predict AA levels in maize, soya bean meal (SBM), meat and bone meal, fish meal and wheat, based on proximate analysis input. Within the GRNNGA architecture, ANN were trained with either an Euclidean or City Block distance metric and a (0,1), (−1,1), (logistic) or (tanh) input scale. Predictive performance was judged on the basis of the maximum R² value. In general, maximum R² values were higher when the GA calibration was used in comparison to LR. For example, the highest methionine (MET) R² value for SBM was 0.54 (LR), 0.81 (3BP), 0.87 (WBP), 0.92 (GRNNIT) and 0.98 (GRNNGA). Genetic algorithm calibration of GRNN architecture led to further improvements in ANN performance for AA level predictions in most of the cases studied. Exceptions were the TSAA level in SBM (0.94 with GRNNIT vs. 0.90 with GRNNGA) and the TRY level in maize (0.88 with GRNNIT vs. 0.61 with GRNNGA).     

Dietary branched-chain amino acids suppress the expression of pancreatic amylase mRNA in rats

Regulators for pancreatic amylase were examined. Rats were fed ad libitum a 20% amino acid (AA) mixture diet (Con), a 60% AA diet (HA), a branched-chain amino acid (BCAA)-rich diet (BC), or a diet supplemented with AA other than BCAA (OA) for 7 d, or fed the Con, HA, BC diets or diets supplemented with individual BCAA. Activity and mRNA levels of pancreatic amylase in the BC and HA groups were lower than those in the Con and OA groups. Leucine and isoleucine contributed to these effects of the BC diet. The mRNA levels correlated with individual pancreatic BCAA concentrations but not with plasma insulin level. In conclusion, dietary BCAA, especially leucine and isoleucine, may reduce amylase mRNA and activity in rats.     

Plasma amino acids in four models of experimental liver injury in rats

Summary We studied the plasma amino acid profiles in four models of hepatic injury in rats. In partially hepatectomized rats (65% of liver was removed) we observed significant increase of aromatic amino acids (AAA; i.e. tyrosine and phenylalanine), taurine, aspartate, threonine, serine, asparagine, methionine, ornithine and histidine. Branched-chain amino acids (BCAA; i.e. valine, leucine and isoleucine) concentrations were unchanged. In ischemic and carbon tetrachloride acute liver damage we observed extreme elevation of most of amino acids (BCAA included) and very low concentration of arginine. In carbon tetrachloride induced liver cirrhosis we observed increased levels of AAA, aspartate, asparagine, methionine, ornithine and histidine and decrease of BCAA, threonine and cystine. BCAA/AAA ratio decreased significantly in partially hepatectomized and cirrhotic rats and was unchanged in ischemic and acute carbon tetrachloride liver damage. We conclude that a high increase of most of amino acids is characteristic of fulminant hepatic necrosis; decreased BCAA/AAA ratio is characteristic of liver cirrhosis; and decrease of BCAA/AAA ratio may not be used as an indicator of the severity of hepatic parenchymal damage.Abbreviations BCAA branched-chain amino acids (i.e. valine, leucine and isoleucine) - AAA aromatic amino acids (i.e. tyrosine and phenylalanine)