A Novel Concept of Amino Acid Supplementation to Improve the Growth of Young Malnourished Male Rats

True Digestibility of Tryptophan in Plant and Animal Protein

BACKGROUND

Protein quality, evaluated using Digestible Indispensable Amino Acid Score (DIAAS), requires ileal digestibility values of individual indispensable amino acids (IAAs) in each protein. However, true tryptophan (Trp) digestibility has rarely been quantified in humans.

OBJECTIVE

To measure the true Trp digestibility and DIAAS of 2H-intrinsically labeled plant and animal protein sources in humans, using the dual isotope tracer technique.

METHODS

The true Trp digestibility of 2H intrinsically labeled plant proteins such as whole mung bean (n = 6) and dehulled mung bean (n = 6), chickpea (n = 5), and yellow pea (n = 5), and protein from animal source foods such as egg white (n = 6), whole egg (n = 6), chicken meat (n = 6), and goat milk (n = 7) was determined against the known digestibility of U-13C spirulina whole cell protein as reference, except for goat milk protein that was measured against free crystalline 13C-Trp as reference. Banked samples from earlier studies conducted to determine true IAA digestibility of different protein sources were used for the analysis. DIAAS was calculated for each test protein using digestibility corrected IAA scores (mg IAA/g of protein) in comparison with the IAA requirement score for adults.

RESULTS

The true Trp digestibility of whole mung bean, dehulled mung bean, chickpea, yellow pea, egg white, whole egg, chicken meat, and goat milk were 67.6 ± 3.7%, 74.5 ± 4.4%, 72.6 ± 2.3%, 72.5 ± 2.2%, 89.7 ± 2.5%, 91.4 ± 2.6%, 95.9 ± 2.2%, and 92.8 ± 2.9%, respectively. The true Trp digestibility of plant protein sources was significantly lower than that of animal protein sources (P < 0.05). Trp was not a limiting IAA in all the tested proteins.

CONCLUSION

The true Trp digestibility determined in this study ranged from 67.6 ± 3.7% to 95.9 ± 2.2% for whole mung bean and chicken meat, respectively, and adds to the database of individual true IAA digestibility of different protein sources.

TRIAL REGISTRATION NUMBER

This study was registered in Clinical Trials Registry of India (CTRI) with registration numbers CTRI/2017/11/010468, CTRI/2020/04/024512, and CTRI/2018/03/012265.

Immunomodulatory Mechanisms of Tea Leaf Polysaccharide in Mice with Cyclophosphamide-Induced Immunosuppression Based on Gut Flora and Metabolomics

Tea polysaccharides (TPSs) are receiving increasing attention because of their diverse pharmacological and biological activities. Here, we explored the immunoregulatory mechanisms of TPSs from fresh tea leaves in a mouse model of cyclophosphamide (CTX)-induced immunosuppression in terms of gut microbiota and metabolites. We observed that TPSs significantly increased the body weight and alleviated CTX-induced thymus atrophy in the immunosuppressed mice; they also increased the plasma levels of immunoglobulins A and M, interleukin (IL) 1β, IL-6, inducible nitric oxide synthase, and tumor necrosis factor α. Furthermore, we conducted 16S rDNA sequencing of cecal contents, resulting in the acquisition of 5008 high-quality bacterial 16S rDNA gene reads from the sequencing of mouse fecal samples. By analyzing the data, we found that TPSs regulated the gut microbiota structure and diversity and alleviated the CTX-induced dysregulation of gut microbiota. The colonic contents of mice were subjected to analysis using the UPLC-Q-TOF/MS/MS technique for the purpose of untargeted metabolomics. In the course of our metabolite identification analysis, we identified a total of 2685 metabolites in positive ion mode and 1655 metabolites in negative ion mode. The analysis of these metabolites indicated that TPSs improved CTX-induced metabolic disorders by regulating the levels of metabolites related to tryptophan, arginine, and proline metabolism. In conclusion, TPSs can alleviate CTX-induced immunosuppression by regulating the structural composition of gut microbiota, indicating the applicability of TPSs as novel innate immune modulators in health foods or medicines.

L-lysine dietary supplementation for childhood and adolescent growth: Promises and precautions

BACKGROUND

L-lysine (lysine) is an essential amino acid that plays a vital role in human nutrition. It serves as a key component in protein synthesis and fulfills critical roles in various physiological activities. For decades, lysine supplements have been extensively used to promote the growth and development of children, particularly in developing countries where cereal-based diets are everyday staples.

AIM OF THE REVIEW

This review aims to provide an overview of the overall effectiveness of lysine supplements concerning the growth of children and adolescents. Additionally, it addresses the potential precautions that should be considered when using lysine supplements in this context.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Receiving lysine oral supplements and lysine-fortified cereal diets were observed to enhance nitrogen retention and improve anthropometric measurements such as height, weight, Z-scores, body mass index, and skinfold thickness. Furthermore, lysine positively influenced the children's developmental quotient and various serological biochemical parameters, such as hormones, immunological indicators, proteins, bone metabolic indicators, and red blood cell parameters. These supplements are generally considered clinically safe, with no reported toxicity where the related side effects are limited to subjective gastrointestinal tract symptoms. It is essential to be cautious about excessive intake of lysine, as it can lead to an imbalance of amino acids, thereby potentially suppressing its intended benefits. When used with appropriate precautions, lysine can serve as a safe supplement with promising benefits for the growth of children and adolescents. Nevertheless, further contemporary research studies on lysine supplementation would be insightful and valuable in better understanding its optimal use, potential benefits, and safety in promoting growth.

Tryptophan oxidation in young children with environmental enteric dysfunction classified by the lactulose rhamnose ratio

BACKGROUND

In young children, associations between linear growth faltering, environmental enteric dysfunction (EED), and the plasma kynurenine (Kyn)/tryptophan (Trp) ratio (KTR) have led to the proposal that higher Trp catabolism in response to intestinal/systemic inflammation limits Trp availability for protein synthesis, resulting in impaired growth.

OBJECTIVES

We sought to estimate the Trp oxidation rate and the Trp conversion rate to Kyn in young children with and without EED.

METHODS

Children aged 18-24 mo, from urban slums, were assigned to EED (n = 19) or no-EED (n = 26) groups on the basis of a urinary lactulose/rhamnose ratio (LRR) cutoff based on mean + 2 SDs of LRR (≥0.068) in normal age- and sex-matched, high-socioeconomic status children. Plasma KTR and fecal biomarkers of EED were measured. Trp oxidation in the fed state was measured using 13C1-Trp in an oral plateau feeding protocol.

RESULTS

The median (quartile 1, quartile 3) fasted KTR was 0.089 (0.066, 0.110) in children with EED compared with 0.070 (0.050, 0.093) in children with no EED (P = 0.077). However, there was no difference in fed-state Trp oxidation [median (quartile 1, quartile 3) 3.1 (1.3, 5.8) compared with 3.9 (1.8, 6.0) µmol/kg FFM/h, respectively, P = 0.617] or Trp availability for protein synthesis [42.6 (36.5, 45.7) compared with 42.5 (37.9, 46.9) µmol/kg FFM/h, respectively, P = 0.868] between the groups. In contrast, the median (quartile 1, quartile 3) fractional synthesis rates of Kyn [12.5 (5.4, 20.0) compared with 21.3 (16.1, 24.7) %pool/h, P = 0.005] and the fraction of Ala derived from Trp [0.007 (0.005, 0.015) compared with 0.012 (0.008, 0.018), P = 0.037], respectively, in the plasma compartment were significantly slower in the EED group. Fecal biomarkers of EED did not differ between the groups.

CONCLUSIONS

The static plasma KTR value is not a good indicator of the dynamic Trp flux down its oxidative pathway. In a poor sanitary environment, children without EED actually have a faster Kyn synthesis rate, which might be beneficial, because of the cytoprotective and anti-inflammatory functions of downstream metabolites. This study was registered in the Clinical Trials Registry of India as CTRI/2017/02/007921.

Soy Protein Alleviates Malnutrition in Weaning Rats by Regulating Gut Microbiota Composition and Serum Metabolites

Dietary intervention with plant protein is one of the main methods that is used to lessen the symptoms of malnutrition. Supplementary soy protein to undernourished weaning rats for 6 weeks significantly increased their body weight gain. After the intervention, the level of total short-chain fatty acids (SCFAs) was restored to 1,512.7 μg/g, while the level was only 637.1 μg/g in the 7% protein group. The amino acids (valine, isoleucine, phenylalanine, and tryptophan) increased in the colon, and vitamin B₆ metabolism was significantly influenced in undernourished rats. The tryptophan and glycine-serine-threonine pathways were elevated, leading to an increase in the level of tryptophan and 5-hydroxytryptophan (5-HTP) in the serum. In addition, the relative abundance of Lachnospiraceae_NK4A136_group and Lactobacillus increased, while Enterococcus and Streptococcus decreased compared to undernourished rats. Overall, soy protein improved the growth of rats with malnutrition in early life by regulating gut microbiota and metabolites in the colon and serum.

Animal Models of Undernutrition and Enteropathy as Tools for Assessment of Nutritional Intervention

: Undernutrition is a major public health problem leading to 1 in 5 of all deaths in children under 5 years. Undernutrition leads to growth stunting and/or wasting and is often associated with environmental enteric dysfunction (EED). EED mechanisms leading to growth failure include intestinal hyperpermeability, villus blunting, malabsorption and gut inflammation. As non-invasive methods for investigating gut function in undernourished children are limited, pre-clinical models are relevant to elucidating the pathophysiological processes involved in undernutrition and EED, and to identifying novel therapeutic strategies. In many published models, undernutrition was induced using protein or micronutrient deficient diets, but these experimental models were not associated with EED. Enteropathy models mainly used gastrointestinal injury triggers. These models are presented in this review. We found only a few studies investigating the combination of undernutrition and enteropathy. This highlights the need for further developments to establish an experimental model reproducing the impact of undernutrition and enteropathy on growth, intestinal hyperpermeability and inflammation, that could be suitable for preclinical evaluation of innovative therapeutic intervention.

Undernutrition and growth in the developing world

PURPOSE OF REVIEW

Despite targeted interventions, an estimated 150.8 million children under 5 years globally are still stunted, of which more than half live in Asia and more than one-third live in Africa. This review summarizes our current knowledge regarding how longitudinal bone growth is regulated by nutritional intake in the developing world. Dietary macronutrients and micronutrients necessary for growth are also briefly reviewed.

RECENT FINDINGS

Recent advances include investigations of nutritionally sensitive regulators of growth as well as prospective evaluations of the role of specific dietary components on growth in order to better assess their impact.

SUMMARY

Further investigation is required to understand how nutrition impacts growth, the mechanisms underlying stunting and to optimize therapeutic strategies for children who are at risk for growth attenuation or are stunted in low and middle-income countries (LMICs).

Induction of uterine hyperplasia after cafeteria diet exposure

Our aim was to evaluate whether chronic administration of CAF affects the uterus and induces the morphological and molecular changes associated with endometrial hyperplasia. Female Wistar rats exposed to CAF from weaning for 20 weeks displayed increased energy intake, body weight and fat depots, but did not develop metabolic syndrome. The adult uteri showed an increase in glandular volume fraction and stromal area. The epithelial proliferation rate and protein expression of oestrogen receptor alpha (ERα) were also increased. The CAF diet enhanced leptin serum levels and the long form of leptin receptor (Ob-Rb) mRNA expression in the uterus. No changes were detected in either insulin serum levels or those of insulin growth factor I (IGF-I) mRNA expression. However the levels of IGF-I receptor (IGF-IR) mRNA were lower in CAF-fed animals. Overall, the results indicate that our rat model of the CAF diet produces morphological and molecular changes associated with uterine hyperplasia and could predispose to endometrial carcinogenesis.