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Amino acids not only play a vital role in the synthesis of biological molecules such as proteins in cancer malignant cells, they are also essential metabolites for immune cell activation and antitumor effects in the tumor microenvironment. The abnormal changes in amino acid metabolism are closely related to the occurrence and development of tumors and immunity. Intestinal microorganisms play an essential role in amino acid metabolism, and tryptophan and its intestinal microbial metabolites are typical representatives. However, it is known that the cyclic amino acid profile is affected by specific cancer types, so relevant studies mainly focus on one type of cancer and rarely study different cancer forms at the same time. The objective of this study was to examine the PFAA profile of five cancer patients and the characteristics of tryptophan intestinal microbial metabolites to determine whether there are general amino acid changes across tumors. Plasma samples were collected from esophageal (n = 53), lung (n = 73), colorectal (n = 94), gastric (n = 55), breast cancer (n = 25), and healthy control (HC) (n = 139) subjects. PFAA profile and tryptophan metabolites were measured, and their perioperative changes were examined using high-performance liquid chromatography. Univariate analysis revealed significant differences between cancer patients and HC. Furthermore, multivariate analysis discriminated cancer patients from HC. Regression diagnosis models were established for each cancer group using differential amino acids from univariate analysis. Receiver-operating characteristic analysis was applied to evaluate these diagnosis models. Finally, GABA, arginine, tryptophan, taurine, glutamic acid, and melatonin showed common alterations across all types of cancer patients. Metabolic pathway analysis shows that the most significant enrichment pathways were tryptophan, arginine, and proline metabolism. This study provides evidence that common alterations of the metabolites mentioned above suggest their role in the pathogenesis of each cancer patient. It was suggested that multivariate models based on PFAA profiles and tryptophan metabolites might be applicable in the screening of cancer patients.

In this study, dried longan pulp (DLP) was subjected to fermentation using selected strains of lactic acid bacteria (Lactobacillus plantarum subsp. Plantarum and Leuconostoc mesenteroides). We then studied changes in the free and bound phytochemical profile, antioxidant activity, free amino acid, and organic acid composition. Fermentation exhibited a 17.4% and 5.7% increase in the amount of free and total phenolic contents of DLP. Phenolic composition determined by HPLC revealed significant changes due to fermentation that were primarily in the contents of gallic acid, vanillic acid, 4-methylcatechol and p-coumaric acid, resulting in a 37.9% and 25.7% increase in free gallic acid and 4-methylcatechol, respectively. Fermentation was also found to enhance the ferric reducing antioxidant power of both free and total and the oxygen radical absorbance capacity of free phenolic fraction by 18.3%, 11.8%, and 37.4%, respectively. In addition, fermentation was observed to reduce the contents of free amino acids with bitter taste (phenylalanine, tyrosine and leucine), and increase amino acids (taurine, aspartic acid, cysteine, cysteine thiazoline and γ-amino-butyric acid) having antioxidant potential. Therefore, this study provides basis for the production of fermented longan-based functional products with improved antioxidant activity.

Background The levels of free amino acids (FAAs) and the timing of bud flush (TBF) are among the the most economic traits of tea plants ( Camellia sinensis ). Investigating the genetic variation characteristics of FAAs and their potential associations with TBF is critical for the breeding of new tea cultivars with high economic value. Methods In this study, we utilized the ‘Emei Wenchun’ (♀) × ‘Chuanmu 217’ (♂) filial 1 (F 1 ) genetic population ( n  = 208) and measured their FAA contents in the “one bud and two leaves” samples across two spring seasons and one summer season using high-performance liquid chromatography combined with the Waters AccQ-Tag method. The sprouting index (SPI) was observed over two springs to quantify the TBF trait. A genetic map previously constructed based on the same population was employed for quantitative trait loci (QTL) mapping. Results A total of 16 FAAs were measured, and the average total FAA contents were 28.1 and 25.4 mg/g (dry weight) in the two spring seasons and 14.29 mg/g in the summer season. Within the population, the coefficients of variation ( CV ) for the FAAs ranged from 23 to 41% within each season, and the correlation coefficients ( r ) varied from 0.15 to 0.35 across seasons. ANOVA analyses revealed that 13 out of the 16 FAAs exhibited significant genetic variation, with the estimated broad-sense heritability ( h 2 ) ranging between 10.33% and 57.10%. Interestingly, three FAAs and the total FAA contents showed significant positive correlations ( r  = 0.21–0.34, P  < 0.01) with the SPI trait in both spring seasons. QTL mapping identified 13 FAA-associated QTLs distributed across eight linkage groups. Conclusion Within the F 1 population, the FAAs exhibited considerable variation across seasons, their heritabilities were generally low (most ≤ 50%). There was a weak but significant positive correlation between FAAs and TBF. Additionally, 13 FAA-associated QTLs were identified. The results of this study enhance our understanding of the genetic variation characteristics of FAAs and provide insights for breeding tea cultivars with both higher FAAs and earlier TBF.

Zinc or copper deficiency and salinity are known soil problems and often occur simultaneously in agriculture soils. Plants undergo various changes in physiological and biochemical processes to respond to high salt in the growing medium. There is lack of information on the relation of exogenous application of Zn and Cu with important salinity tolerance mechanisms in plants. Therefore, the present study was conducted to determine the effect of foliar Zn and Cu on two maize cultivars (salt-tolerant cv. Yousafwala Hybrid and salt-sensitive cv. Hybrid 1898). Salinity caused a significant reduction in water and turgor potentials, stomatal conductance, and transpiration and photosynthetic rate, while increase in glycine betaine, proline, total soluble sugars, and total free amino acids was evident in plants under saline regimes. Furthermore, there was significant decline in P, N, Ca, K, Mn, Fe, Zn, and Cu and increase in Na and Cl contents in plants fed with NaCl salinity. Nitrate reductase activity was lower in salt-stressed plants. However, foliar application of Zn and Cu circumvented salinity effect on water relations, photosynthesis, and nutrition and this was attributed to the better antioxidant system and enhanced accumulation of glycine betaine, proline, total free amino acids, and sugars. The results of the present study suggested that Zn application was superior to Cu for mediating plant defense responses under salinity.

Taurine, an amino acid-like compound, acts as an osmostress protectant in many marine metazoans and algae and is released via various processes into the oceanic dissolved organic matter pool. Taurine transporters are widespread among members of the marine prokaryotic community, tentatively indicating that taurine might be an important substrate for prokaryotes in the ocean. In this study, we determined prokaryotic taurine assimilation and respiration throughout the water column along two transects in the North Atlantic off the Iberian Peninsula. Taurine assimilation efficiency decreased from the epipelagic waters from 55 ± 14% to 27 ± 20% in the bathypelagic layers (means of both transects). Members of the ubiquitous alphaproteobacterial SAR11 clade accounted for a large fraction of cells taking up taurine, especially in surface waters. Archaea (Thaumarchaeota + Euryarchaeota) were also able to take up taurine in the upper water column, but to a lower extent than Bacteria. The contribution of taurine assimilation to the heterotrophic prokaryotic carbon biomass production ranged from 21% in the epipelagic layer to 16% in the bathypelagic layer. Hence, we conclude that dissolved free taurine is a significant carbon and energy source for prokaryotes throughout the oceanic water column being utilized with similar efficiencies as dissolved free amino acids.

Nonvolatile taste active compounds, including free amino acids (FAAs), 5′-nucleotides, betaine, soluble sugars, trimethylamine oxide and organic acids of wild and cultured mud crab Scylla paramamosain were examined. The main taste in mud crab (MC) is derived from the FAAs, 5′-nucleotides, betaine, and organic acids, based on the fact that these compounds have a taste activity value (TAV) > 1. Wild MCs had a higher content of total FAAs, 5′-nucleotides, betaine, and organic acids in meat compared with cultured animals. However, no differences in the taste active compound levels were observed in the gonads of wild and cultured MCs, with betaine being the exception (wild crab > cultured crab). The total concentrations of FAAs in MC ranged from 12.71 to 36.94 mg/g. Monosodium glutamate (MSG)-like FAAs were primarily contributed by glutamic acid, and ranged from 0.71 to 0.93 mg/g. The concentrations of 5′-nucleotides were 1.10–2.24 mg/g, in which 5′-inosine monophosphate (IMP) and 5′-adenosine monophosphate (AMP) were the predominant TAVs (TAV > 1). The total concentrations of organic acids in MC were 2.41–11.10 mg/g, in which lactic and succinic acid in meat, and citric acid and succinic acid in female gonads were the main organic acids. The gonads were observed to have higher concentrations of 5′-nucleotides and organic acids compared with crab meat, with the equivalent umami concentration in gonads being higher than that in crab meat. In conclusion, wild MCs contained more active-taste nonvolatile flavor components relative to those detected in cultured MCs.

The gut bacteria can provide nutrition for the host, and regulate host physiological functions and host behavior. In this study, we specifically examined the important roles of free amino acids in the gut microbiota-host interaction. Bumblebees were treated with different concentrations of antibiotics (ampicillin combined with low/high concentrations of tetracycline). Then the effect of antibiotic treatments on the host body weight, gut microbiota, and the free amino acid profiles in the hindgut, hemolymph and brain of bees was evaluated. The results showed that antibiotic treatments resulted in a significant decrease in the host body weight at 11 days of age, the total bacterial load and the abundance of Bifidobacterium bohemicum and Gilliamella apicola in the bumblebee’s hindgut. Additionally, the higher the concentration of antibiotics (tetracycline), the greater their impact on the body weight and intestinal microbiota of bumblebees. Further, we found that antibiotic treatments caused changes of free amino acids in different tissues, especially in the hindgut and hemolymph, including particularly the decrease of several types of essential amino acids and branched-chain amino acids. Our results suggest that the gut microbiota may modulate the host growth via specific essential amino acids and branched-chain amino acids, which further reveals the crucial roles of free amino acids in the gut microbiota-host interplay.

Altered plasma levels of branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs) may predict the development of insulin resistance and other type 2 diabetes mellitus (T2DM) associated comorbidities. To elucidate the role of plasma free amino acids (PFAAs) profile as a biomarker for early detection of diabetic kidney disease, quantitative measurement of PFAAs profile was determined for 90 T2DM subjects, 30 were free of nephropathy, 30 with microalbuminuria, 30 with macroalbuminuria, and in addition to 30 healthy controls. The plasma levels of valine, leucine, isoleucine, phenylalanine, citrulline, and total BCAAs were significantly increased in diabetic normoalbuminuria group when compared to controls. However, the total BCAAs level was significantly decreased in diabetic patients with micro and macroalbuminuria. Other amino acid plasma levels as tyrosine, arginine, ornithine, glycine, and the total AAAs level were significantly decreased in all diabetic subgroups compared to controls. Significant positive correlations between total BCAAs, valine, leucine, isoleucine, serum insulin, glucose, and HOMA-IR values in the diabetic normoalbuminuria group were found. The use of altered PFAAs profile as a prognostic factor in T2DM patients at risk for microalbuminuria or macroalbuminuria might reduce or prevent the incidence of end-stage diabetic renal disease.

To prevent the progression of type 2 diabetes mellitus (T2DM), early detection and intervention are important. Several studies have already shown that the serum adiponectin level could be useful for evaluating the future risk of T2DM. Recently, plasma free amino acid (PFAA) concentrations have also emerged as potential biomarkers that predict the future onset of T2DM. In this study, we aimed to further characterise PFAA profiles by elucidating the association with the serum high molecular weight (HMW) adiponectin level in this cross-sectional study. A total of 1000 Japanese subjects who underwent medical check-ups were enrolled, and their plasma concentrations of 21 amino acids and clinical parameters were measured. The subjects without T2DM were divided into quartiles (Q1-4) by serum HMW adiponectin level, and the association with between PFAA concentrations was analysed. Concentrations of glutamate, alanine, proline, tyrosine, histidine, methionine, lysine, branched-chain amino acids (BCAAs) and tryptophan varied significantly according to the adiponectin quartile. Furthermore, serum adiponectin levels showed significant inverse correlations with these amino acids. The change in the PFAA profile in the group with the lowest adiponectin concentrations (Q1) was similar to that of T2DM patients. Although both adiponectin levels and PFAA concentrations are known to be altered by the accumulation of visceral fat and insulin resistance, the levels of glutamate, BCAA, lysine and tryptophan remain significantly associated with adiponectin level after adjustment for age, body mass index and homeostasis model assessment of insulin resistance, showing the direct association between PFAA concentrations and the serum HMW adiponectin level. Registration number: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) UMIN000029920, registered on Nov 13th 2017 (prospectively registered).

Sixty Duroc × Large White × Landrace pigs with an average initial body weight (BW) of 77.1 ± 1.3 kg were selected to investigate the effects of dietary supplementation with arginine (Arg) and/or glutamic acid (Glu) on free amino acid (FAA) profiles, expression of AA transporters, and growth-related genes in skeletal muscle. The animals were randomly assigned to one of five treatment groups (basic diet, iso-nitrogenous, Arg, Glu, and Arg + Glu groups). The results showed that plasma Glu concentration was lowest in the Arg + Glu group and highest in the Glu group (P < 0.05). In the longissimus dorsi (LD) muscle, the concentrations of histidine, Arg, and taurine in the Arg + Glu group were higher, and the concentrations of 3-methylhistidine was lower, than in the basic diet group (P < 0.05). The mRNA levels of ASC amino acid transporter-2 (ASCT2), L-type AA transporter 1, and sodium-coupled neutral amino acid transporter 2 in the LD muscle, as well as the mRNA levels of ASCT2 and proton-assisted amino acid transporter in the biceps femoris (BF) muscle, were higher in the Arg + Glu group compared to the basic diet group (P < 0.05). The mRNA levels of the muscle-specific RING finger-1 and muscle atrophy F-box genes in the LD muscle were downregulated in the Glu and Arg + Glu groups compared to the basic diet group (P < 0.05). Collectively, these findings suggest that dietary supplementation with both Arg and Glu increases intramuscular FAA concentrations and decreases the mRNA levels of genes involved in protein degradation in skeletal muscle.