Valine May Be the First Limiting Branched-Chain Amino Acid in Egg Protein in Men

Greater plasma essential amino acids and lower 3-methylhistidine with higher protein intake during endurance training: a randomised control trial

Endurance exercise alters amino acid (AA) metabolism that necessitates greater AA intake in the post exercise recovery period to support recovery. Thus, daily AA ingestion during a period of endurance training may affect the metabolically active plasma free AA pool, which is otherwise maintained during periods of inadequate protein intake by the breakdown of skeletal muscle proteins. Nine endurance-trained males completed a 4-day running protocol (20 km, 5 km, 10 km and 20 km on days 1-4, respectively) on three occasions with a controlled diet providing different protein intakes [0.94(LOW), 1.20(MOD) or 1.83gprotein kgbody mass-1 day-1 (HIGH)]. Urine collected over 24 h on day-4 and plasma collected after an overnight fast on day-5 were analyzed for free AA (plasma) and 3-methylhistidine (3MH; plasma and urine), a marker of myofibrillar protein breakdown. There was an effect of protein intake (HIGH > MOD/LOW; P < 0.05) on fasted plasma essential AA, branched chain AA and 3MH but no effect on 24-h urinary 3-MH excretion. Consuming a previously determined optimal daily protein intake of 1.83 g kg-1 day-1 during endurance training maintains fasted plasma free AA and may attenuate myofibrillar protein catabolism, although this latter effect was not detected in 24-h urinary excretion. The maintenance of the metabolically active free plasma AA pool may support greater recovery from exercise and contribute to the previously determined greater whole-body net protein balance in this athletic population. TRN: NCT02801344 (June 15, 2016).

Determining ideal balance among branched-chain amino acids in medical formula for Propionic Acidemia: A proof of concept study in healthy children

BACKGROUND

Propionic Acidemia (PROP) is an inherited metabolic disorder, with defect in the enzyme propionyl-CoA carboxylase (PCC) which catalyzes catabolism of two of the branched-chain amino acids (BCAA), valine, isoleucine. Nutritional management in PROP depends on dietary protein restriction and consumption of medical formula depleted of the offending amino acids. Recently, concerns have been raised about medical formula due to imbalanced content of BCAA (high leucine - another BCAA, and no valine/isoleucine), which negatively impacts plasma concentrations of BCAA, and growth in children with PROP.

OBJECTIVES AND METHODS

To determine an optimal BCAA ratio at which total body protein synthesis is optimized in healthy children using the indicator amino acid oxidation method (oxidation of L-¹³C-Phenylalanine to ¹³CO₂). This was accomplished by reducing leucine intake gradually from the current high dose in medical formula, in order to compare protein synthesis, under different BCAA ratios.

RESULTS

A total of 8 healthy children were studied, completing 42 study days. Significant differences in F¹³CO₂ with different BCAA ratios were found. BCAA ratio (leucine: isoleucine: valine) 1:0:0 was associated with the highest F¹³CO₂ (low protein synthesis) compared to other ratios. By reducing leucine intake, and isoleucine and valine at minimum PROP recommendations, BCAA ratio between1:0.26:0.28 to 1:0.35:0.4 was associated with optimal protein synthesis.

CONCLUSION

BCAA ratio of 1:0:0, present in medical formula limited total body protein synthesis. A balanced BCAA ratio was found between 1:0.26:0.28 and 1:0.35:0.4 (leucine:isoleucine:valine). Future research is needed to test this optimal BCAA ratio for optimizing protein synthesis in patients with PROP.

SYNOPSIS

The article describes a proof-of-concept study done on healthy school-aged children testing different ratios of branched chain amino acid (BCAA, leucine:isoleucine:valine), in order to determine an optimal ratio at which total body protein synthesis is improved and has implications for dietary management of children with Propionic Acidemia (PROP).

Effect of two postharvest technologies on the micronutrient profile of cashew kernels from Mozambique

The economics involved in processing cashew nuts (Anacardium occidentale) might alter micronutrient profiles and concentrations. We analyzed and evaluated carotenoids, tocopherols, tocotrienols, minerals, fatty acids, and amino acids in (1) cashew kernels with testa recovered from nuts dried with and without the apple, and (2) testa-free industrial grade baby butts, splits, and white whole kernels using HPLC, ICP-OES, and GC-MS techniques. The results indicated that drying cashews with the respective apple slightly decreased the concentration of some carotenoids and total fatty and amino acids, but increased the concentration of iron, magnesium, and total tocotrienols compared with the conventionally (sun-) dried kernels. We also found high concentrations of carotenoids in the testa-containing kernels. Among the industrially processed kernel, baby butt grade was associated with lower content of β-carotene, total tocopherols, and tocotrienols, but with significantly higher concentrations in minerals, fatty acids, and amino acids than in white wholes and split grades. Conventional sun drying of cashew nuts revealed results similar to drying with apples regarding micronutrient concentrations. The high micronutrient content of industrial grade BB is reflected in widespread human consumption and better market value.

High-throughput sequencing analysis identified microRNAs associated with egg production in ducks ovaries

BACKGROUND

MicroRNAs (miRNAs) exist widely and are involved in multiple biological processes in ducks, whereas the regulatory mechanism of miRNAs in egg laying of ducks has remained unclear. This study aims to reveal key miRNAs involved in the regulation of egg production in duck ovaries.

METHODS

High-throughput sequencing was performed on four egg-type duck ovaries and four egg-meat-type duck ovaries at the start of the egg-laying stage. Quantitative reverse transcription PCR (qRT-PCR) validation was performed on differentially expressed miRNAs (DE miRNAs). Gene network of DEmiRNA-mRNA-pathway was constructed by Cytoscape.

RESULTS

A total of 251 know miRNAs and 1,972 novel miRNAs were obtained from whole clean reads. Among the known miRNAs, we identified 21 DEmiRNAs, including eight down-regulated and 13 up-regulated miRNAs in egg-type ducks compared with egg-meat-type ducks. Among the novel miRNAs, we identified 70 DEmiRNAs, including 58 down-regulated and 12 up-regulated in egg-type ducks compared with egg-meat-type ducks. The expression patterns of four miRNAs were verified by qRT-PCR. The DEmiRNAs were involved in the function of response to folic acid and the pathway of valine, leucine and isoleucine degradation. Specific target genes of DEmiRNAs enrichment was found in some egg-laying regulation pathways, such as dopaminergic synapse, ovarian steroidogenesis and oocyte meiosis. The DEmiRNA-mRNA-pathway network including three DEmiRNAs, nine mRNAs and 11 pathways. apl-miR-194-5p and apl-miR-215-5p may be potential key miRNAs in regulating egg laying.

CONCLUSIONS

This study provided miRNAs profiles in ducks about egg laying and establish a theoretical basis for subsequent selection or modification of duck phenotypes at the molecular level.

Leucine is not a good choice as an indicator amino acid for determining amino acid requirements in men

Leucine tracer has been widely used for examining whole-body protein turnover in humans, but has not been evaluated as an indicator to be used in the indicator amino acid oxidation (IAAO) method. The goal of this study was to determine whether the L-[1-(13C)]leucine isotope is an acceptable indicator by comparing it with an established tracer, L-[1-(13C)]lysine. Healthy men (n = 7; 29.9 +/- 4.8 y old) were fed in random order a diet with 7 graded intakes of phenylalanine without tyrosine. In the first study (n = 5), subjects were administered an excess leucine intake of 65 mg/(kg.d), and in the second study (n = 5), they were given the mean requirement of 45 mg/(kg.d) to determine whether leucine intake affected the pattern of response. Previous IAAO studies using lysine and phenylalanine demonstrated a clear pattern in 13CO2 production, i.e., increasing test amino acid intake resulted in a linear decrease to plateau, with a readily discernable breakpoint indicating the requirement. This pattern of production of 13CO2, indicates clear partitioning of the indicator amino acid between oxidation and protein synthesis. This was not observed with leucine at an intake of 65 mg/(kg.d). Conversely, at the lower leucine intake of 45 mg/(kg.d), a breakpoint was seen and a total aromatic amino acid requirement estimate that did not differ from that obtain using lysine as the indicator was obtained. In conclusion, leucine may be used as the indicator in the IAAO technique only when the daily intake leucine is given at its mean requirement level and the potential metabolic effects of other variables are taken into consideration.

Branched-chain amino acid needs in children with mild-to-moderate chronic cholestatic liver disease

Protein-energy malnutrition is prevalent in children with chronic cholestatic liver disease. Supplementation of branched-chain amino acids (BCAA) in infants and children with chronic liver disease has been associated with significant improvement in growth and nitrogen balance, suggesting that BCAA requirements are increased in chronic liver disease. The goal of the present study was to determine the total BCAA requirement in children with mild-to-moderate chronic cholestatic (MCC) liver disease using indicator amino acid oxidation (IAAO). Total BCAA requirements were determined in 6 children (6.3 +/- 3.7 y, mean +/- SD) with MCC liver disease. Children were randomly assigned to receive 7 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as those present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. The total BCAA requirement was determined by measuring the oxidation of l-[1-13C] Phe to 13CO2 [F13CO2 in micromol/(kg x h)], after a primed, continuous oral administration of the tracer and using a 2-phase linear regression crossover regression analysis. The estimated mean requirement and the upper limit of the 95% CI for total BCAA establishing using the IAAO in children with MCC liver disease were 209 and 272 mg/(kg x d), respectively. Total BCAA estimated average requirements using the IAAO were significantly higher than mean requirements established previously for healthy children (P < 0.05).

Branched-chain amino acid requirements in healthy adult human subjects

There is now an expanding body of evidence to recommend, in the case of adult humans, the use of revised indispensable amino acid requirement values; these are approximately 2 to 3 times higher than the current international recommendations. The earlier methodologies for determining amino acid requirements, based on nitrogen balance, were criticized because of their design and the associated high energy intakes. The 1985 World Health Organization/Food & Agriculture Organization/United Nations University requirement for leucine has been demonstrated to be too low by short- and long-term (24-h) tracer-derived estimates of leucine oxidation and balance. The best values for leucine requirements come from 24-h direct amino acid oxidation (DAAO) and direct amino acid balance (DAAB) studies. Finally, we also collated all available data from studies on fed-state leucine oxidation with an adequate dietary adaptation period to assess the inflection on the leucine oxidation-leucine intake curve. The mean requirements for leucine, valine, and isoleucine are likely to be 40, 17-25, and 19 mg . kg(-1) . d(-1), respectively. This adds up to a total of approximately 84 mg . kg(-1) . d(-1), which is much lower than the lowest estimate of the total BCAA requirement of approximately 110 mg . kg(-1) . d(-1) made by the short-term indicator amino acid oxidation (IAAO) method, which determined the BCAA requirement from the pattern of oxidation of an indicator amino acid (phenylyalanine) at different levels of BCAA intake. An additional estimate of the leucine requirement was also made by a meta-analysis of all available 24-h DAAO/DAAB data from different studies. This resulted in a higher value for the leucine requirement than that obtained by the specific studies that utilized the 24-h DAAO/DAAB approach; however, even adding this value to the total BCAA requirement does not account for the difference in the total BCAA requirement estimates and the summed individual BCAA estimates.

Comparative nutrition and metabolism: explication of open questions with emphasis on protein and amino acids

The 20th century saw numerous important discoveries in the nutritional sciences. Nonetheless, many unresolved questions still remain. Fifteen questions dealing with amino acid nutrition and metabolism are posed in this review. The first six deal with the functionality of sulfur amino acids (methionine and cysteine) and related compounds. Other unresolved problems that are discussed include priorities of use for amino acids having multiple functions; interactions among lysine, niacin and tryptophan; amino acid contributions to requirements from gut biosynthesis; the potential for gluconeogenesis to divert amino acids away from protein synthesis; the unique nutritional and metabolic idiosyncrasies of feline species, with emphasis on arginine; controversies surrounding human amino acid requirements; and the potential for maternal diet to influence sex ratio of offspring.

The daily valine requirement of healthy adult Indians determined by the 24-h indicator amino acid balance approach

BACKGROUND

The 1985 FAO/WHO/UNU requirement for valine was set at 10 mg x kg(-1) x d(-1) on the basis of nitrogen balance studies carried out in Western subjects. It is likely that the requirement is higher, however, because the requirement of another branched-chain amino acid, leucine, was found to be about 3 times as high (40 mg x kg(-1) x d(-1)) as the 1985 FAO/WHO/UNU value (14 mg x kg(-1) x d(-1)).

OBJECTIVE

We assessed the valine requirement in healthy, well-nourished Indians by using 7 test valine intakes (5, 10, 15, 20, 25, 30, and 35 mg x kg(-1) x d(-1)) and the 24-h indicator amino acid oxidation (24-h IAAO) and balance (24-h IAAB) method, with phenylalanine as the indicator amino acid, while maintaining leucine intake at 40 mg x kg(-1) x d(-1).

DESIGN

Eighteen healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods supplying valine intakes that were equally placed on either side of a putative mean valine requirement of 20 mg x kg(-1) x d(-1). Twenty-four-hour IAAO and 24-h IAAB were measured on day 7 by use of a 24-h [13C]phenylalanine tracer infusion. The breakpoint in the relation between these values and the valine intake was determined.

RESULTS

Two-phase linear regression of daily phenylalanine oxidation or balance against valine intake estimated a breakpoint in the response curve at a valine intake of 17 mg x kg(-1) x d(-1) (95% Fieller's CI: 11, > 35 and 11, 28 mg x kg(-1) x d(-1), respectively).

CONCLUSION

From the 24-h IAAO/IAAB approach, a mean valine requirement of 17 mg x kg(-1) x d(-1) is proposed for healthy, well-nourished Indian adults.

Tolerance for branched-chain amino acids in experimental animals and humans

There is no good evidence for establishing branched-chain amino acid (BCAA) tolerance levels for humans. With pigs, chicks, and rats, data are available concerning excessive intake levels of BCAA, but most of the information is for growing animals instead of for adults. Estimates of maintenance requirements for (high-quality) protein and BCAA in pigs weighing between 43 and 140 kg are 350 mg . kg(-1) . d(-1) for protein and 28.7 mg . kg(-1) . d(-1) for total BCAA. In contrast, human adult maintenance requirement estimates are much higher, i.e., 660 mg . kg(-1) . d(-1) for good quality protein and a range of 68 to 144 mg . kg(-1) . d(-1) for total BCAA. The human maintenance BCAA requirement estimates range from 10.3 to 22% of the maintenance protein requirement. Whole-body protein of 45-kg pigs contains 14.2 g BCAA/100 g protein, but the maintenance requirement (based on nitrogen balance) for total BCAA is only 8.2% of the total maintenance protein requirement. Conversely, sulfur amino acid (methionine + cysteine), threonine, and tryptophan maintenance requirements of pigs as a percentage of the maintenance protein requirement are much higher than whole-body protein levels of these amino acids. This suggests that the efficiency of using absorbed amino acids of dietary origin or of reusing endogenous amino acids arising from body protein catabolism may vary considerably among the indispensable amino acids. Additionally, work with pigs points to the conclusion that whole-body amino acid concentrations are poor predictors of both maintenance requirements and ideal amino acid profiles. Based on studies with young experimental animals, a rather large dietary excess (above requirement) of an individual BCAA is well tolerated when consumed in diets containing surfeit levels of protein and the other 2 BCAA.

Parenteral and enteral routes of feeding in neonatal piglets require different ratios of branched-chain amino acids

The requirements for total branched-chain amino acids (BCAA), isoleucine, leucine and valine, in neonatal piglets receiving parenteral and enteral nutrition was determined recently. The optimum ratio among BCAA during different routes of feeding is not yet known. In this study, the ratio of BCAA during parenteral and enteral feeding was tested using the indicator amino acid oxidation (IAAO) technique. Male Yorkshire piglets (n=24) received amino acid-based diets containing adequate nutrients for 5 d. Phenylalanine oxidation and kinetics were determined from a 4-h primed, constant infusion of L-[1-14C]-phenylalanine on d 6 and 8. On d 6, all piglets received a BCAA diet which met 75% of the total BCAA requirement, based on our previous research, with a ratio of 1:1.8:1.2 of isoleucine/leucine/valine. On d 8, the piglets were randomly assigned to receive one of the 3 test diets supplemented with isoleucine (+isoleucine), leucine (+leucine) or valine (+valine) to meet 100% of requirement, with the remaining two BCAA at 75% of requirement. The difference in phenylalanine oxidation (% of dose) between d 6 and 8 was used as an indicator of BCAA adequacy. In enterally fed piglets, the change in the percentage of the dose oxidized was minimal for all 3 test diets (mean=1.15%). In parenterally fed piglets, the difference in phenylalanine oxidation (% of dose) between d 6 and 8 was +isoleucine (12.6%), +leucine (2%) and +valine (6.6%). The ratio of 1:1.8:1.2 of isoleucine/leucine/valine is appropriate for enteral feeding, but during parenteral feeding, isoleucine was first limiting and valine was second limiting.