Glycine metabolism in animals and humans: implications for nutrition and health

Postruminal choline supply during negative nutrient balance alters components of hepatic mTOR signaling and plasma amino acids in lactating Holstein cows

Choline requirements for dairy cattle are unknown. However, enhanced postruminal supply of choline may increase flux through the methionine cycle to spare Met for other functions such as protein synthesis and phosphatidylcholine (PC) synthesis during periods of negative nutrient balance (NNB). The objective was to investigate the effects of postruminal choline supply during a feed restriction-induced NNB on hepatic abundance and phosphorylation of mTOR (mechanistic target of rapamycin)-related signaling proteins, hepatic lipidome and plasma AA. Ten primiparous rumen-cannulated Holstein cows (158 ± 24 DIM) were used in a replicated 5 × 5 Latin square design with 4 d of treatment and 10 d of recovery (14 d/period). Treatments were unrestricted intake with abomasal infusion of water, restricted intake (R; 60% of net energy for lactation requirements to induce NNB) with abomasal infusion of water (R0) or restriction plus abomasal infusion of 6.25, 12.5, or 25 g/d choline ion. Liver tissue was collected via biopsy on d 5 after infusions ended and used for Western blot analysis to measure proteins involved in mTOR signaling and untargeted lipidomics. Blood was collected on d 1 to 5 for plasma AA analysis. Statistical contrasts for protein and AA data were A0 versus R0 (CONT1), R0 versus the average of choline dose (CONT2) and tests of linear and quadratic effects of choline dose. Analysis of lipidomic data were performed with the web-based metabolomic processing tool MetaboAnalyst 5.0. Ratios of p-RPS6KB1:tRPS6KB1, p-EEF2:tEEF2, and p-EIF2:tEIF2 were greater with R (CONT1). Among those, supply of choline led to decreases in p-EEF2:tEEF2 (CONT2), p-EIF2:tEIF2 and tended to decrease p-EIF4BP1:tEIF4BP1. However, the effect was quadratic only for p-EEF2:tEEF2 and p-EIF2A:tEIF2A, reaching a nadir at 6.25 to 12.5 g/d choline ion. The ratio of p-RPS6KB1:tRPS6KB1 was not affected by supply of choline and was close to 2-fold greater at 25 g/d choline versus A0. Plasma Met concentration decreased with R (CONT1), but increased linearly with choline. Restriction also increased plasma 3-methyl-histidine (CONT1). The partial least squares discriminant analysis model of liver lipids distinguished treatments, with 13.4% of lipids being modified by treatment. One-way ANOVA identified 109 lipids with a false discovery rate ≤0.05. The largest group identified was PC species; all 35 detected decreased with R versus A0, but there were few differences among choline treatments. Overall, data suggested that dephosphorylation of EEF2 and EIF2A due to enhanced choline supply potentially helped maintain or increase protein synthesis during NNB. While activation of mTOR was not altered by choline, this idea of increased protein synthesis is partly supported by the increased circulating Met. However, enhanced postruminal choline had limited effects on the species of lipid produced during a period of NNB.

Glutathione and glutathione-dependent enzymes: From biochemistry to gerontology and successful aging

The tripeptide glutathione (GSH), namely γ-L-glutamyl-L-cysteinyl-glycine, is an ubiquitous low-molecular weight thiol nucleophile and reductant of utmost importance, representing the central redox agent of most aerobic organisms. GSH has vital functions involving also antioxidant protection, detoxification, redox homeostasis, cell signaling, iron metabolism/homeostasis, DNA synthesis, gene expression, cysteine/protein metabolism, and cell proliferation/differentiation or death including apoptosis and ferroptosis. Various functions of GSH are exerted in concert with GSH-dependent enzymes. Indeed, although GSH has direct scavenging antioxidant effects, its antioxidant function is substantially accomplished by glutathione peroxidase-catalyzed reactions with reductive removal of H2O2, organic peroxides such as lipid hydroperoxides, and peroxynitrite; to this antioxidant activity also contribute peroxiredoxins, enzymes further involved in redox signaling and chaperone activity. Moreover, the detoxifying function of GSH is basically exerted in conjunction with glutathione transferases, which have also antioxidant properties. GSH is synthesized in the cytosol by the ATP-dependent enzymes glutamate cysteine ligase (GCL), which catalyzes ligation of cysteine and glutamate forming γ-glutamylcysteine (γ-GC), and glutathione synthase, which adds glycine to γ-GC resulting in GSH formation; GCL is rate-limiting for GSH synthesis, as is the precursor amino acid cysteine, which may be supplemented as N-acetylcysteine (NAC), a therapeutically available compound. After its cell export, GSH is degraded extracellularly by the membrane-anchored ectoenzyme γ-glutamyl transferase, a process occurring, as GSH synthesis and export, in the γ-glutamyl cycle. GSH degradation occurs also intracellularly by the cytoplasmic enzymatic ChaC family of γ-glutamyl cyclotransferase. Synthesis and degradation of GSH, together with its export, translocation to cell organelles, utilization for multiple essential functions, and regeneration from glutathione disulfide by glutathione reductase, are relevant to GSH homeostasis and metabolism. Notably, GSH levels decline during aging, an alteration generally related to impaired GSH biosynthesis and leading to cell dysfunction. However, there is evidence of enhanced GSH levels in elderly subjects with excellent physical and mental health status, suggesting that heightened GSH may be a marker and even a causative factor of increased healthspan and lifespan. Such aspects, and much more including GSH-boosting substances administrable to humans, are considered in this state-of-the-art review, which deals with GSH and GSH-dependent enzymes from biochemistry to gerontology, focusing attention also on lifespan/healthspan extension and successful aging; the significance of GSH levels in aging is considered also in relation to therapeutic possibilities and supplementation strategies, based on the use of various compounds including NAC-glycine, aimed at increasing GSH and related defenses to improve health status and counteract aging processes in humans.

Systemic perturbations in amino acids/amino acid derivatives and tryptophan pathway metabolites associated with murine influenza A virus infection

BACKGROUND

Influenza A virus (IAV) is the only influenza virus causing flu pandemics (i.e., global epidemics of flu disease). Influenza (the flu) is a highly contagious disease that can be deadly, especially in high-risk groups. Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness and in about 290,000 to 650,000 respiratory deaths. We intend to reveal the effect of IAV infection on the host's metabolism, immune response, and neurotoxicity by using a mouse IAV infection model.

METHODS

51 metabolites of murine blood plasma (33 amino acids/amino acid derivatives (AADs) and 18 metabolites of the tryptophan pathway) were analyzed by using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry with Electrospray Ionization at the acute (7 days post-infection (dpi)), resolution (14 dpi), and recovery (21 dpi) stages of the virus infection in comparison with controls.

RESULTS

Among the 33 biogenic amino acids/AADs, the levels of five amino acids/AADs (1-methylhistidine, 5-oxoproline, α-aminobutyric acid, glutamine, and taurine) increased by 7 dpi, whereas the levels of ten amino acids/AADs (4-hydroxyproline, alanine, arginine, asparagine, cysteine, citrulline, glycine, methionine, proline, and tyrosine) decreased. By 14 dpi, the levels of one AAD (3-methylhistidine) increased, whereas the levels of five amino acids/AADs (α-aminobutyric acid, aminoadipic acid, methionine, threonine, valine) decreased. Among the 18 metabolites from the tryptophan pathway, the levels of kynurenine, quinolinic acid, hydroxykynurenine increased by 7 dpi, whereas the levels of indole-3-acetic acid and nicotinamide riboside decreased.

CONCLUSIONS

Our data may facilitate understanding the molecular mechanisms of host responses to IAV infection and provide a basis for discovering potential new mechanistic, diagnostic, and prognostic biomarkers and therapeutic targets for IAV infection.

Effects of soda water on blood lipid and metabolic profiling of urine in hyperlipidemia rats using UPLC/Triple-TOF MS

The effects of a natural soda water (Shi Han Quan, SHQ) on hyperlipidemia and the changes of urine metabolic profiling by metabolomics techniques were investigate. Thirty six Wistar rats weighing 160-200 g were divided into control group, hyperlipidemia (HL) group, and hyperlipidemia + SHQ water (SHQ) group. The metabolites in urine were determined using ultra high performance liquid chromatography-triple-time of flight-mass spectrometry (UPLC/Triple-TOF MS). At the end of 1 month and 3 months, the total glyceride (TG) level was significantly lower in SHQ group compared to HL group. There was no significantly difference in total cholesterol (TC) levels in HL group compared with SHQ group. The results showed that dinking SHQ water can improve the TG, but with no effects on TC. After drinking SHQ water for 3 months, the rats in different groups could be classified into different clusters according to the metabolites in urine. Total 15 important metabolites were found and correlated with disturbance of amino acid, phospholipid, fatty acid and vitamin metabolism, which suggested the changes of metabolism in the body and possible mechanism by which SHQ improved the TG. These findings provide a new insight for the prevention and control of hyperlipidemia.

Effects of caloric restriction and ketogenic diet on renal fibrosis after ischemia/reperfusion injury

The beneficial effects of caloric restriction (CR) and a ketogenic diet (KD) have been previously shown when performed prior to kidney injury. We investigated the effects of CR and KD on fibrosis development after unilateral kidney ischemia/reperfusion (UIR). Post-treatment with CR significantly (p < 0.05) affected blood glucose (2-fold decrease), ketone bodies (3-fold increase), lactate (1.5-fold decrease), and lipids (1.4-fold decrease). In the kidney, CR improved succinate dehydrogenase and malate dehydrogenase activity by 2-fold each, but worsened fibrosis progression. Similar results were shown for the KD, which restored the post-UIR impaired activities of succinate dehydrogenase, malate dehydrogenase, and α-ketoglutarate dehydrogenase (which was decreased 2-fold) but had no effect on fibrosis progression. Thus, our study shows that the use of CR or KD after UIR did not reduce the development of fibrosis, as shown by hydroxyproline content, western-blotting, and RT-PCR, whereas it caused significant metabolic changes in kidney tissue after UIR.

Alfalfa leaf meal as a new protein feedstuff improves meat quality by modulating lipid metabolism and antioxidant capacity of finishing pigs

The effects of alfalfa leaf meal (ALM) on the meat quality of finishing pigs are largely unknown. Here, we investigated the effects of ALM diet on meat quality by replacing 0%, 25%, 50%, and 75% of soybean meal in the diet of finishing pigs, respectively. The findings showed that 25% ALM diet increased the IMF, cooked meat rate, a* and antioxidant capacity of longissimus dorsi (LD), improved amino acid composition, increased MUFA content, and increased LD lipid synthesis and mRNA expression of antioxidation-related genes. At the same time, ALM diet altered serum lipid metabolism (TG, FFA). Correlation analysis showed that antioxidant capacity was positively correlated with meat quality. In addition, metabolomic analysis of LD showed that the main metabolites of 25% ALM diet altered stachydrine and l-carnitine were associated with meat quality and antioxidant capacity. In conclusion, ALM replacing 25% soybean meal diet can improve the meat quality of pigs.

Glycine and N-Acetylcysteine (GlyNAC) Combined with Body Weight Support Treadmill Training Improved Spinal Cord and Skeletal Muscle Structure and Function in Rats with Spinal Cord Injury

Skeletal muscle atrophy is a frequent complication after spinal cord injury (SCI) and can influence the recovery of motor function and metabolism in affected patients. Delaying skeletal muscle atrophy can promote functional recovery in SCI rats. In the present study, we investigated whether a combination of body weight support treadmill training (BWSTT) and glycine and N-acetylcysteine (GlyNAC) could exert neuroprotective effects, promote motor function recovery, and delay skeletal muscle atrophy in rats with SCI, and we assessed the therapeutic effects of the double intervention from both a structural and functional viewpoint. We found that, after SCI, rats given GlyNAC alone showed an improvement in Basso-Beattie-Bresnahan (BBB) scores, gait symmetry, and results in the open field test, indicative of improved motor function, while GlyNAC combined with BWSTT was more effective than either treatment alone at ameliorating voluntary motor function in injured rats. Meanwhile, the results of the skeletal muscle myofiber cross-sectional area (CSA), hindlimb grip strength, and acetylcholinesterase (AChE) immunostaining analysis demonstrated that GlyNAC improved the structure and function of the skeletal muscle in rats with SCI and delayed the atrophication of skeletal muscle.

The Toxicity Differences of Fluralaner against the Red Imported Fire Ant (Solenopsis invicta) at Different Developmental Stages

The red imported fire ant (RIFA), Solenopsis invicta, is an invasive pest that causes damage to agricultural and ecological environments worldwide. Fluralaner is a new isoxazoline pesticide with the potential to become a control agent against RIFA. However, it is not clear whether S. invicta responds the same way to fluralaner at different reproductive stages. The present study firstly evaluated the toxicity of fluralaner to S. invicta at different developmental stages, finding that fourth instar larvae (LD50, 1744.23 mg/kg) and worker ants (LD50, 8.62 mg/kg) were differently susceptible to fluralaner, while the mortality rate of fourth instar larvae was significantly lower at the same concentration of 10 mg/L (5.56 ± 3.14%) than that of worker ants (62.22 ± 3.14%), demonstrating a greater tolerance to fluralaner. Subsequently, the metabolic responses of worker and larval ants to fluralaner stress (10 mg/L) were investigated using non-targeted metabolomics, which indicated that the amount of differential metabolites and the KEGG metabolic pathways enriched were different between workers and larvae when exposed to the same dose (10 mg/L) of fluralaner. Differential metabolites of larvae and worker ants under fluralaner stress were mainly concentrated in organic acids and their derivatives, lipids and lipid-like molecules, nucleosides, nucleotides, and analogues, combined with the enriched metabolic pathways, revealed that the differential metabolic responses of larvae and worker ants were mainly in energy metabolism, detoxification metabolism, and neurotransmitter ligands. Workers consumed more substrates in the arginine synthesis pathway (l-glutamic acid, l-aspartic acid, and fumaric acid) to provide energy for the detoxification (glutathione) of pesticides when exposed to fluralaner stress, and the high accumulation of l-aspartic acid induced excitotoxicity in the worker ants. Larval ants consumed more arachidonic acid to synthesize PG D2, and changes in the metabolism of antioxidants such as catechins, hesperidin, and l-ascorbic acid suggested that larvae were more capable of scavenging the ROS response than worker ants. The results of non-targeted metabolomics successfully revealed differences in the sensitivity of larvae and workers to fluralaner agents, providing insights into the fluralaner control of Solenopsis invicta.

Variation in Acetyl-CoA Carboxylase Beta Gene and Its Effect on Carcass and Meat Traits in Gannan Yaks

Acetyl-CoA carboxylase beta (ACACB) is a functional candidate gene that impacts fat deposition. In the present study, we sequenced exon 37-intron 37, exon 46-intron 46, and intron 47 of yak ACACB using hybrid pool sequencing to search for variants and genotyped the gene in 593 Gannan yaks via Kompetitive allele-specific polymerase chain (KASP) reaction to determine the effect of ACACB variants on carcass and meat quality traits. Seven single nucleotide polymorphisms were detected in three regions. Eight effective haplotypes and ten diplotypes were constructed. Among them, a missense variation g.50421 A > G was identified in exon 37 of ACACB, resulting in an amino acid shift from serine to glycine. Correlation analysis revealed that this variation was associated with the cooking loss rate and yak carcass weight (p = 0.024 and 0.012, respectively). The presence of haplotypes H5 and H6 decreased Warner-Bratzler shear force (p = 0.049 and 0.006, respectively), whereas that of haplotypes H3 and H4 increased cooking loss rate and eye muscle area (p = 0.004 and 0.034, respectively). Moreover, the presence of haplotype H8 decreased the drip loss rate (p = 0.019). The presence of one and two copies of haplotypes H1 and H8 decreased the drip loss rate (p = 0.028 and 0.004, respectively). However, haplotype H1 did not decrease hot carcass weight (p = 0.011), whereas H3 increased the cooking loss rate (p = 0.007). The presence of one and two copies of haplotype H6 decreased Warner-Bratzler shear force (p = 0.014). The findings of the present study suggest that genetic variations in ACACB can be a preferable biomarker for improving yak meat quality.

Ascertaining the Influence of Lacto-Fermentation on Changes in Bovine Colostrum Amino and Fatty Acid Profiles

The aim of this study was to collect samples of bovine colostrum (BCOL) from different sources (agricultural companies A, B, C, D and E) in Lithuania and to ascertain the influence of lacto-fermentation with Lactiplantibacillus plantarum strain 135 and Lacticaseibacillus paracasei strain 244 on the changes in bovine colostrum amino (AA), biogenic amine (BA), and fatty acid (FA) profiles. It was established that the source of the bovine colostrum, the used LAB, and their interaction had significant effects (p < 0.05) on AA contents; lactic acid bacteria (LAB) used for fermentation was a significant factor for aspartic acid, threonine, glycine, alanine, methionine, phenylalanine, lysine, histidine, and tyrosine; and these factor's interaction is significant on most of the detected AA concentrations. Total BA content showed significant correlations with glutamic acid, serine, aspartic acid, valine, methionine, phenylalanine, histidine, and gamma amino-butyric acid content in bovine colostrum. Despite the differences in individual FA contents in bovine colostrum, significant differences were not found in total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids. Finally, the utilization of bovine colostrum proved to be challenging because of the variability on its composition. These results suggest that processing bovine colostrum into value-added formulations for human consumption requires the adjustment of its composition since the primary production stage. Consequently, animal rearing should be considered in the employed bovine colostrum processing technologies.

Causal relationships of circulating amino acids with cardiovascular disease: a trans-ancestry Mendelian randomization analysis

BACKGROUND

Epidemiological studies demonstrated that multiple amino acids (AAs) were associated with cardiovascular diseases (CVDs), but whether these associations were causal remains unclear. This study aims to investigate the causal relationships between circulating levels of 20 AAs and 10 CVDs in European and East Asian populations by Mendelian randomization (MR).

METHODS

This MR study utilized single-nucleotide polymorphisms that were significantly associated with AAs as instrumental variables. Summary-level data for AAs and CVDs were obtained from public genome-wide association studies. The causal effects were primarily estimated by inverse variance weighting with multiplicative random effect method. Sensitivity analyses, including weighted median, weighted mode, and MR Egger regression, were used to test the robustness of our results.

RESULTS

In the European population, alanine and serine were inversely associated with angina pectoris (AP) and chronic heart failure, respectively. With each unit increase of leucine, the risk of ischemic stroke increased by 10%. Moreover, tyrosine was positively associated with AP and deep vein thrombosis. In the East Asian population, each unit increase in glycine was associated with 4.1% and 9.0% decreased risks of coronary artery disease (CAD) and myocardial infarction (MI), respectively. A unit increase in serine was associated with 13.1%, 12.6% and 15.5% decreased risks of AP, CAD and MI, respectively. Sensitivity analyses supported the robustness of our results.

CONCLUSIONS

This MR study demonstrated significant causal effects of circulating levels of AAs on CVDs, indicating the potential use of AAs as biomarkers or as therapeutic targets for CVD in clinical scenarios.

Effects of Glycine Supplementation in Drinking Water on the Growth Performance, Intestinal Development, and Genes Expression in the Jejunum of Chicks

Glycine, the most basic amino acid found in nature, is considered an essential amino acid for chicks. However, the precise understanding of high concentrations of glycine's significance in promoting the growth performance of chicks, as well as its impact on intestinal development, re-mains limited. Consequently, the objective of this study was to investigate the effects of glycine supplementation in drinking water on growth performance, intestine morphology, and development in newly hatched chicks. In this study, 200 newly born chicks were selected and pro-vided with a supplementation of 0.5%, 1%, and 2% glycine in their drinking water during their first week of life. The results revealed that glycine supplementation in drinking water could significantly increase the average daily gain of chicks from days 7 to 14. Furthermore, a significant difference was observed between the group supplemented with 1% glycine and the control group. Concurrently, this glycine supplementation increased the villus height and the ratio of the villus height to crypt depth in jejunum on both day 7 and day 14. Glycine supplementation in drinking water significantly affected the mRNA expression level of the ZO-1, GCLM, and rBAT genes in jejunum, which may have certain effects on the mucosal immune defense, cellular antioxidant stress capacity, and amino acid absorption. Overall, the findings of this study indicate that glycine supplementation in drinking water can enhance the growth performance of chicks and promote their intestine development.

Plasma amino acid signatures define types of pediatric diabetes

BACKGROUND & AIMS

Metabolic biomarkers with pathophysiological relevance is lacking in pediatric diabetes. We aimed to identify novel metabolic biomarkers in pediatric type 1 (T1D) and type 2 diabetes (T2D). We hypothesized that (1) targeted plasma metabolomics, focused on plasma amino acid concentrations, could identify distinctively altered patterns in children with T1D or T2D, and (2) there are specific changes in concentrations of metabolites related to branch chain amino acids (BCAA) and arginine metabolism in children with T2D.

METHODS

In a pilot study, we enrolled children with T1D (n = 15) and T2D (n = 13), and healthy controls (n = 15). Fasting plasma amino acid concentrations were measured by ultra-performance liquid chromatography, and compared between the groups after adjustment for confounding factors.

RESULTS

The mean age (SD) of participants was 16.4 (0.9) years. There were no group differences in age, gender, race/ethnicity, or 24-h protein intake. Mean BMI percentile was higher in the T2D than the T1D group or controls (p < 0.001). The T2D group had lower arginine, citrulline, glutamine, glycine, phenylalanine, methionine, threonine, asparagine and symmetric dimethylarginine (SDMA) but higher aspartate than controls, after adjusting for BMI percentiles (all p < 0.05). Children with T2D also had lower glycine but higher ornithine, proline, leucine, isoleucine, valine, total BCAA, lysine and tyrosine than those with T1D after adjusting for confounding factors (all p < 0.05). Children with T1D had lower phenylalanine, methionine, threonine, glutamine, tyrosine, asymmetric dimethylarginine (ADMA) and SDMA than controls (all p < 0.05).

CONCLUSIONS

Children with T2D and T1D have distinct fasting plasma amino acid signatures that suggest varying pathogenic mechanisms and could serve as biomarkers for these conditions.

Biodegradable Piezoelectric Polymers: Recent Advancements in Materials and Applications

Recent materials, microfabrication, and biotechnology improvements have introduced numerous exciting bioelectronic devices based on piezoelectric materials. There is an intriguing evolution from conventional unrecyclable materials to biodegradable, green, and biocompatible functional materials. As a fundamental electromechanical coupling material in numerous applications, novel piezoelectric materials with a feature of degradability and desired electrical and mechanical properties are being developed for future wearable and implantable bioelectronics. These bioelectronics can be easily integrated with biological systems for applications, including sensing physiological signals, diagnosing medical problems, opening the blood-brain barrier, and stimulating healing or tissue growth. Therefore, the generation of piezoelectricity from natural and synthetic bioresorbable polymers has drawn great attention in the research field. Herein, the significant and recent advancements in biodegradable piezoelectric materials, including natural and synthetic polymers, their principles, advanced applications, and challenges for medical uses, are reviewed thoroughly. The degradation methods of these piezoelectric materials through in vitro and in vivo studies are also investigated. These improvements in biodegradable piezoelectric materials and microsystems could enable new applications in the biomedical field. In the end, potential research opportunities regarding the practical applications are pointed out that might be significant for new materials research.

Synthesis of glycine from 4-hydroxyproline in tissues of neonatal pigs with intrauterine growth restriction

This study tested the hypothesis that the synthesis of glycine from 4-hydroxyproline (an abundant amino acid in milk and neonatal blood) was impaired in tissues of piglets with intrauterine growth restriction (IUGR), thereby contributing to a severe glycine deficiency in these compromised neonates. At 0, 7, 14, and 21 days of age, IUGR piglets were euthanized, and tissues (liver, small intestine, kidney, pancreas, stomach, skeletal muscle, and heart) were obtained for metabolic studies, as well as the determination of enzymatic activities, cell-specific localization, and expression of mRNAs for glycine-synthetic enzymes. The results indicated relatively low enzymatic activities for 4-hydroxyproline oxidase (OH-POX), proline oxidase, serine hydroxymethyltransferase, threonine dehydrogenase (TDH), alanine: glyoxylate transaminase, and 4-hydroxy-2-oxoglutarate aldolase in the kidneys and liver from 0- to 21-day-old IUGR pigs, in the pancreas of 7- to 21-day-old IUGR pigs, and in the small intestine and skeletal muscle (except TDH) of 21-day-old IUGR pigs. Accordingly, the rates of conversion of 4-hydroxyproline into glycine were relatively low in tissues of IUGR piglets. The expression of mRNAs for glycine-synthetic enzymes followed the patterns of enzymatic activities and was also low. Immunohistochemical analyses revealed the relatively low abundance of OH-POX protein in the liver, kidney, and small intestine of IUGR piglets, and the lack of OH-POX zonation in their livers. These novel results provide a metabolic basis to explain why the endogenous synthesis of glycine is insufficient for optimum growth of IUGR piglets and have important implications for improving the nutrition and health of other mammalian neonates including humans with IUGR.

Preserved Ratio Impaired Spirometry, Metabolomics, and the Risk of Type 2 Diabetes

CONTEXT

Whether baseline preserved ratio impaired spirometry (PRISm) is associated with the risk of developing type 2 diabetes (T2D) and if this association could be mediated by circulating metabolites remains to be elucidated.

OBJECTIVE

To measure the prospective association of PRISm with T2D and potential metabolic mediators thereof.

METHODS

This study used data from the UK Biobank and included 72 683 individuals without diabetes at baseline. PRISm was defined as the predicted forced expiratory volume in 1 second (FEV1) <80% and the FEV1/forced vital capacity ratio ≥0.70. Cox proportional hazards modeling was performed to assess the longitudinal relation between baseline PRISm and incident T2D. Mediation analysis was used to explore the mediation effects of circulating metabolites in the path from PRISm to T2D.

RESULTS

During a median follow-up of 12.06 years, 2513 participants developed T2D. Individuals who had PRISm (N = 8394) were 47% (95% CI, 33%-63%) more likely to develop T2D compared with those who had normal spirometry (N = 64 289). A total of 121 metabolites showed statistically significant mediation effects in the path from PRISm to T2D (false discovery rate <0.05). Glycoprotein acetyls, cholesteryl esters in large high-density lipoprotein (HDL), degree of unsaturation, cholesterol in large HDL, and cholesteryl esters in very large HDL were the top 5 metabolic markers, with mediation proportions (95% CI) being 11.91% (8.76%-16.58%), 11.04% (7.34%-15.55%), 10.36% (7.34%-14.71%), 9.87% (6.78%-14.09%), and 9.51% (6.33%-14.05%), respectively. A total of 11 principal components that explained 95% variance of the metabolic signatures accounted for 25.47% (20.83%-32.19%) of the relation between PRISm and T2D.

CONCLUSIONS

Our study revealed the association of PRISm with T2D risk and the potential roles of circulating metabolites in mediating this association.

Yin/Yang associated differential responses to Psoralea corylifolia Linn. In rat models: an integrated metabolomics and transcriptomics study

ETHNOPHARMACOLOGICAL RELEVANCE

Psoralea corylifolia Linn. (BGZ) is a commonly used traditional Chinese medicine (TCM) for the treatment of kidney-yang deficiency syndrome (Yangsyn) with good curative effect and security. However, BGZ was also reported to induce liver injury in recent years. According to TCM theory, taking BGZ may induce a series of adverse reactions in patients with kidney-yin deficiency syndrome (Yinsyn), which suggests that BGZ-induced liver damage may be related to its unreasonable clinical use.

AIM OF THE STUDY

Liver injury caused by TCM is a rare but potentially serious adverse drug reaction, and the identification of predisposed individuals for drug-induced liver injury (DILI) remains challenging. The study aimed to investigate the differential responses to BGZ in Yangsyn and Yinsyn rat models and identify the corresponding characteristic biomarkers.

MATERIALS AND METHODS

The corresponding animal models of Yangsyn and Yinsyn were induced by hydrocortisone and thyroxine + reserpine respectively. Body weight, organ index, serum biochemistry, and Hematoxylin and Eosin (HE) staining were used to evaluate the liver toxicity effect of BGZ on rats with Yangsyn and Yinsyn. Transcriptomics and metabonomics were used to screen the representative biomarkers (including metabolites and differentially expressed genes (DEGs)) changed by BGZ in Yangsyn and Yinsyn rats, respectively.

RESULTS

The level changes of liver organ index, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), suggested that BGZ has liver-protective and liver-damaging effects on Yangsyn and Yinsyn rats, respectively, and the results also were confirmed by the pathological changes of liver tissue. The results showed that 102 DEGs and 27 metabolites were significantly regulated related to BGZ's protective effect on Yangsyn, which is mainly associated with the glycerophospholipid metabolism, arachidonic acid metabolism, pantothenate, and coenzyme A (CoA) biosynthesis pathways. While 28 DEGs and 31 metabolites, related to the pathway of pantothenate and CoA biosynthesis, were significantly regulated for the BGZ-induced liver injury in Yinsyn. Furthermore, 4 DEGs (aldehyde dehydrogenase 1 family member B1 (Aldh1b1), solute carrier family 25 member 25 (Slc25a25), Pim-3 proto-oncogene, serine/threonine kinase (Pim3), out at first homolog (Oaf)) and 4 metabolites (phosphatidate, phosphatidylcholine, N-Acetylleucine, biliverdin) in the Yangsyn group and 1 DEG [galectin 5 (Lgals5)] and 1 metabolite (5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate) in Yinsyn group were significantly correlated to the ALT and AST levels of BGZ treated and untreated groups (receiver operating characteristic (ROC) ≥ 0.9).

CONCLUSIONS

Yinsyn and Yangsyn are the predisposed syndromes for BGZ to exert liver damage and liver protection respectively, which are mainly related to the regulation of amino acid metabolism, lipid metabolism, energy metabolism, and metabolism of cofactors and vitamins. The results further suggest that attention should be paid to the selection of predisposed populations when using drugs related to the regulation of energy metabolism, and the Yinsyn/Yangsyn animal models based on the theory of TCM syndromes may be a feasible method for identifying the susceptible population to receive TCM.

Muscle transcriptome analysis provides new insights into the growth gap between fast- and slow-growing Sinocyclocheilus grahami

Sinocyclocheilus grahami is an economically valuable and famous fish in Yunnan Province, China. However, given its slow growth (40 g/2 years) and large growth differences among individuals, its growth performance needs to be improved for sustainable future use, in which molecular breeding technology can play an important role. In the current study, we conducted muscle transcriptomic analysis to investigate the growth gaps among individuals and the mechanism underlying growth within 14 fast- and 14 slow-growth S. grahami. In total, 1,647 differentially expressed genes (DEGs) were obtained, including 947 up-regulated and 700 down-regulated DEGs in fast-growth group. Most DEGs were significantly enriched in ECM-receptor interaction, starch and sucrose metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, amino acids biosynthesis and metabolism, peroxisome, and PPAR signaling pathway. Some genes related to glycogen degradation, glucose transport, and glycolysis (e.g., adipoq, prkag1, slc2a1, agl, pygm, pgm1, pfkm, gapdh, aldoa, pgk1, pgam2, bpgm, and eno3) were up-regulated, while some genes related to fatty acid degradation and transport (e.g., acox1, acaa1, fabp1b.1, slc27a1, and slc27a2) and amino acid metabolism (e.g., agxt, shmt1, glula, and cth) were down-regulated in the fast-growth group. Weighted gene co-expression network analysis identified col1a1, col1a2, col5a1, col6a2, col10a1, col26a1, bglap, and krt15 as crucial genes for S. grahami growth. Several genes related to bone and muscle growth (e.g., bmp2, bmp3, tgfb1, tgfb2, gdf10, and myog) were also up-regulated in the fast-growth group. These results suggest that fast-growth fish may uptake adequate energy (e.g., glucose, fatty acid, and amino acids) from fodder, with excess energy substances used to synthesize collagen to accelerate bone and muscle growth after normal life activities are maintained. Moreover, energy uptake may be the root cause, while collagen synthesis may be the direct reason for the growth gap between fast- and slow-growth fish. Hence, improving food intake and collagen synthesis may be crucial for accelerating S. grahami growth, and further research is required to fully understand and confirm these associations.

Early-life differences in the gut microbiota composition and functionality of infants at elevated likelihood of developing autism spectrum disorder

Evidence from cross-sectional human studies, and preliminary microbial-based intervention studies, have implicated the microbiota-gut-brain axis in the neurobiology of autism spectrum disorder (ASD). Using a prospective longitudinal study design, we investigated the developmental profile of the fecal microbiota and metabolome in infants with (n = 16) and without (n = 19) a family history of ASD across the first 36 months of life. In addition, the general developmental levels of infants were evaluated using the Mullen Scales of Early Learning (MSEL) test at 5 and 36 months of age, and with ADOS-2 at 36 months of age. At 5 months of age, infants at elevated-likelihood of ASD (EL) harbored less Bifidobacterium and more Clostridium and Klebsiella species compared to the low-likelihood infants (LL). Untargeted metabolic profiling highlighted that LL infants excreted a greater amount of fecal γ-aminobutyric acid (GABA) at 5 months, which progressively declined with age. Similar age-dependent patterns were not observed in the EL group, with GABA being consistently low across all timepoints. Integrated microbiome-metabolome analysis showed a positive correlation between GABA and Bifidobacterium species and negative associations with Clostridium species. In vitro experiments supported these observations demonstrating that bifidobacteria can produce GABA while clostridia can consume it. At the behavioral level, there were no significant differences between the EL and LL groups at 5 months. However, at 36 months of age, the EL group had significantly lower MSEL and ADOS-2 scores compared to the LL group. Taken together, the present results reveal early life alterations in gut microbiota composition and functionality in infants at elevated-likelihood of ASD. These changes occur before any behavioral impairments can be detected, supporting a possible role for the gut microbiota in emerging behavioral variability later in life.

Glycine: The Smallest Anti-Inflammatory Micronutrient

Glycine is a non-essential amino acid with many functions and effects. Glycine can bind to specific receptors and transporters that are expressed in many types of cells throughout an organism to exert its effects. There have been many studies focused on the anti-inflammatory effects of glycine, including its abilities to decrease pro-inflammatory cytokines and the concentration of free fatty acids, to improve the insulin response, and to mediate other changes. However, the mechanism through which glycine acts is not clear. In this review, we emphasize that glycine exerts its anti-inflammatory effects throughout the modulation of the expression of nuclear factor kappa B (NF-κB) in many cells. Although glycine is a non-essential amino acid, we highlight how dietary glycine supplementation is important in avoiding the development of chronic inflammation.

Synthesis of glycine from 4-hydroxyproline in tissues of neonatal pigs

Glycine from sow's milk only meets 20% of the requirement of suckling piglets. However, how glycine is synthesized endogenously in neonates is not known. This study determined glycine synthesis from 4-hydroxyproline (an abundant amino acid in milk and neonatal blood) in tissues of sow-reared piglets with normal birth weights. Piglets were euthanized at 0, 7, 14 and 21 days of age, and their tissues were used to determine glycine synthesis from 0 to 5 mM 4-hydroxyproline, activities and mRNA expression of key glycine-synthetic enzymes, and their cell-specific localization. Activities of 4-hydroxyproline oxidase (OH-POX), proline oxidase (POX), serine hydroxymethyltransferase (SHMT), threonine dehydrogenase (TDH), alanine:glyoxylate transaminase (AGT), and 4-hydroxy-2-oxoglutarate aldolase (HOA) occurred in the kidneys and liver from all age groups of piglets, and in the pancreas of 7- to 21-day-old piglets. Activities of OH-POX and HOA were absent from the small intestine of newborn pigs but present in the small intestine of 7- to 21-day-old piglets and in the skeletal muscle of 14- to 21-day-old piglets. Between days 0 and 21 of age, the enzymatic activities of OH-POX, AGT, and HOA decreased in the liver and kidneys but increased in the pancreas and small intestine with age. The mRNA levels of these three enzymes changed in a manner similar to their enzymatic activities. In contrast to OH-POX, AGT, and HOA, the enzymatic activities of POX, SHMT, and TDH were present in the kidneys, liver, and intestine of all age groups of piglets. Glycine was synthesized from 0.1 to 5 mM 4-hydroxyproline in the liver and kidney from 0- to 21-day-old piglets, as well as the pancreas, small intestine, and skeletal muscle from 14- to 21-day-old piglets in a concentration-dependent manner. Collectively, our findings indicate that 4-hydroxyproline is used for the synthesis of glycine in tissues of piglets to compensate for the deficiency of glycine in milk.

The impact of age-related digestive disorders on in vitro digestibility of macronutrients and bioaccessibility of minor components of chia seeds

Gastrointestinal (GI) functions deteriorate with age, primarily affecting protein digestion. The consumption of chia seeds may be helpful for the elderly because they offer a vegetable-based source of proteins, healthy lipids, fibre and micronutrients. The impact of common age-related GI deterioration on chia seed digestibility was assessed using in vitro digestion models. The goal was to study the potential of chia seeds as part of the diet of seniors. Deterioration in the oral, gastric and intestinal stages of digestion was cumulatively assessed in three digestion models: E1 (deterioration in oral conditions), E2 (deterioration in oral and gastric conditions) and E3 (deterioration in oral, gastric and intestinal conditions). Less efficient chewing (E1) decreased proteolysis, lipolysis and antioxidant capacity (p < 0.05). In contrast, deterioration in gastric functions seemed to affect only total polyphenolic content. Finally, in the model simulating the greatest deterioration in digestive functions (E3), all measured variables were negatively affected (proteolysis, lipolysis, amino acid release, total phenolic content, antioxidant capacity and calcium). Calcium bioaccessibility fell by 24 % with a decrease in pancreatic enzymes and bile secretion (E3). Age-related reduced digestive function did not affect the ratio of essential to non-essential amino acids in the digested samples in any case. However, under suboptimal GI conditions (E3), amino acids such as valine, leucine and isoleucine, which are important for sarcopenia prevention in the elderly, fell by 39 %, 49 % and 44 %, respectively. These findings might be helpful for further in vitro studies of chia seeds as a possible food ingredient. They may also be useful for the development of more targeted nutrition strategies in the elderly.

Multi-omics analyses reveal relationships among polyphenol-rich oolong tea consumption, gut microbiota, and metabolic profile: A pilot study

Convincing evidence has suggested the health potentials of oolong tea (OT) on gut microbiota homeostasis; however, limited population-based studies exist regarding the effect of OT consumption on human gut microbial and metabolic profile. This pilot study explored gut microbial and metabolic changes in healthy adults with a 3-week oolong tea intake. Our findings showed that OT treatment significantly altered gut microbial diversity (Shannon index, 5.4±0.1 vs. 5.7±0.1 pre- and post-OT treatment), reorganized gut microbiota composition, enriched Bacteroides and Prevotella, decreased Megamonas, and improved gastrointestinal function. Also, gut microbes from overweight subjects with BMI >23.9 exhibited greater responses to OT treatment compared with normal-weight counterparts. Metabolomic analysis identified OT intake-induced 23 differential metabolites and 10 enriched metabolic pathways. This study may provide new insights into the association among OT intervention, host gut microbiome and metabolic profile, and improve the knowledge of clinical strategies and personalized nutrition.

Dietary protein reduction with stepwise addition of crystalline amino acids and the effect of considering a minimum glycine-serine content in broiler diets

Reducing the dependency on soybean meal (SBM) is necessary to improve the sustainability of the poultry industry. Moreover, the recommendations for minimum contents of dietary Gly+Ser require further research. Two parallel studies were executed to determine the effects of replacing SBM with crystalline amino acids (CAA) to meet the amino acid requirements and to determine whether a minimum content of Gly+Ser is necessary for broiler diets. In study 1, 1,860 one-day-old male chicks were fed a common starter phase diet (22.8% CP). During the grower-1, grower-2, and finisher phases, the control CP content was reduced (up to 2.1%) with the stepwise addition of CAA (treatments 1-5). Within each feeding phase, AME, standardized ileal digestible Lys, and the minimum Met, Thr, Val, Gly+Ser, Ile, Arg, and Trp to Lys ratios were similar. In study 2, 1,488 male chickens were used in a 2 × 2 factorial design with the Gly+Ser content and feed ingredients used as main factors. Performance was monitored during 41 d in both studies. Reduction in CP content linearly increased (P < 0.05) BW, ADG, and ADFI in the grower-1, grower-2, and finisher phases. When the overall FCR was adjusted considering the BW differences (FCRadj); FCRadj linearly decreased with the weighted average CP (WACP) content (P < 0.001). In the lowest CP treatment, estimated dietary N utilization efficiency was improved by 10%, and the overall N excretion was reduced by 16% compared with the control (P < 0.001). The overall SBM and soybean oil intakes were linearly reduced relative to WACP (-12.0 and -20.2% in control vs. treatment 5, respectively; P < 0.001). Formulating with a minimum Gly+Ser content in the starter phase improved the FCR (P < 0.05) only in the corn-SBM-based diet. In grower-1, increasing Gly+Ser content improved the FCR independent of the feed ingredients used (P < 0.05). Crystalline amino acids can be used to partially replace intact protein reducing the dependency on SBM. Young birds may not synthesize enough Gly endogenously and a minimum content should be provided in the early phases.

Urinary metabolomic biomarker candidates for skeletal muscle wasting in patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease that affects the joints, leading to chronic synovial inflammation and local tissue destruction. Extra-articular manifestations may also occur, such as changes in body composition. Skeletal muscle wasting is often observed in patients with RA, but methods for assessing loss of muscle mass are expensive and not widely available. Metabolomic analysis has shown great potential for identifying changes in the metabolite profile of patients with autoimmune diseases. In this setting, urine metabolomic profiling in patients with RA may be a useful tool to identify skeletal muscle wasting.

METHODS

Patients aged 40-70 years with RA have been recruited according to the 2010 ACR/EULAR classification criteria. Further, the Disease Activity Score in 28 joints using the C-reactive protein level (DAS28-CRP) determined the disease activity. The muscle mass was measured by Dual X-ray absorptiometry (DXA) to generate the appendicular lean mass index (ALMI) by summing the lean mass measurements for both arms and legs and dividing them by height squared (kg/height² ). Finally, urine metabolomic analysis by ¹ H nuclear magnetic resonance (¹ H-NMR) spectroscopy was performed and the metabolomics data set analysed using the BAYESIL and MetaboAnalyst software packages. Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were applied to the ¹ H-NMR data, followed by Spearman's correlation analysis. The combined receiver operating characteristic curve (ROC) was calculated, as well as the logistic regression analyses to establish a diagnostic model. The significance level at P < 0.05 was set for all analyses.

RESULTS

The total set of subjects investigated included 90 patients with RA. Most patients were women (86.7%), with a mean age of 56.5 ± 7.3 years old and a median DAS28-CRP of 3.0 (IQR 1.0-3.0). Fifteen metabolites were identified in the urine samples with high variable importance in projection (VIP scores) by MetaboAnalyst. Of these, dimethylglycine (r = 0.205; P = 0.053), oxoisovalerate (r = -0.203; P = 0.055), and isobutyric acid (r = -0.249; P = 0.018) were significantly correlated with ALMI. Based on the low muscle mass (ALMI ≤6.0 kg/m² for women and ≤8.1 kg/m² for men) a diagnostic model have been established with dimethylglycine (area under the curve [AUC] = 0.65), oxoisovalerate (AUC = 0.49), and isobutyric acid (AUC = 0.83) with significant sensitivity and specificity.

CONCLUSIONS

Isobutyric acid, oxoisovalerate, and dimethylglycine from urine samples were associated with low skeletal muscle mass in patients with RA. These findings suggest that this group of metabolites may be further tested as biomarkers for identification of skeletal muscle wasting.

Shared diagnostic genes and potential mechanism between PCOS and recurrent implantation failure revealed by integrated transcriptomic analysis and machine learning

Polycystic ovary syndrome (PCOS) is a complex endocrine metabolic disorder that affects 5-10% of women of reproductive age. The endometrium of women with PCOS has altered immune cells resulting in chronic low-grade inflammation, which attribute to recurrent implantation failure (RIF). In this study, we obtained three PCOS and RIF datasets respectively from the Gene Expression Omnibus (GEO) database. By analyzing differentially expressed genes (DEGs) and module genes using weighted gene co-expression networks (WGCNA), functional enrichment analysis, and three machine learning algorithms, we identified twelve diseases shared genes, and two diagnostic genes, including GLIPR1 and MAMLD1. PCOS and RIF validation datasets were assessed using the receiver operating characteristic (ROC) curve, and ideal area under the curve (AUC) values were obtained for each disease. Besides, we collected granulosa cells from healthy and PCOS infertile women, and endometrial tissues of healthy and RIF patients. RT-PCR was used to validate the reliability of GLIPR1 and MAMLD1. Furthermore, we performed gene set enrichment analysis (GSEA) and immune infiltration to explore the underlying mechanism of PCOS and RIF cooccurrence. Through the functional enrichment of twelve shared genes and two diagnostic genes, we found that both PCOS and RIF patients had disturbances in metabolites related to the TCA cycle, which eventually led to the massive activation of immune cells.

GlyNAC (Glycine and N-Acetylcysteine) Supplementation in Old Mice Improves Brain Glutathione Deficiency, Oxidative Stress, Glucose Uptake, Mitochondrial Dysfunction, Genomic Damage, Inflammation and Neurotrophic Factors to Reverse Age-Associated Cognitive Decline: Implications for Improving Brain Health in Aging

Cognitive decline frequently occurs with increasing age, but mechanisms contributing to age-associated cognitive decline (ACD) are not well understood and solutions are lacking. Understanding and reversing mechanisms contributing to ACD are important because increased age is identified as the single most important risk factor for dementia. We reported earlier that ACD in older humans is associated with glutathione (GSH) deficiency, oxidative stress (OxS), mitochondrial dysfunction, glucose dysmetabolism and inflammation, and that supplementing GlyNAC (glycine and N-acetylcysteine) improved these defects. To test whether these defects occur in the brain in association with ACD, and could be improved/reversed with GlyNAC supplementation, we studied young (20-week) and old (90-week) C57BL/6J mice. Old mice received either regular or GlyNAC supplemented diets for 8 weeks, while young mice received the regular diet. Cognition and brain outcomes (GSH, OxS, mitochondrial energetics, autophagy/mitophagy, glucose transporters, inflammation, genomic damage and neurotrophic factors) were measured. Compared to young mice, the old-control mice had significant cognitive impairment and multiple brain defects. GlyNAC supplementation improved/corrected the brain defects and reversed ACD. This study finds that naturally-occurring ACD is associated with multiple abnormalities in the brain, and provides proof-of-concept that GlyNAC supplementation corrects these defects and improves cognitive function in aging.

Effect of individual or combination of dietary betaine and glycine on productive performance, stress response, liver health, and intestinal barrier function in broiler chickens raised under heat stress conditions

The current experiment was conducted to investigate the effect of individual or combination of dietary betaine (Bet) and glycine (Gly) on productive performance, stress response, liver health, and intestinal barrier function in broiler chickens raised under heat stress (HS) conditions. A total of four hundred twenty 21-d-old Ross 308 broiler chickens were randomly allotted to 1 of 5 dietary treatments with 7 replicates. Birds in treatment 1 were raised under the thermoneutral condition (TN; 23 ± 0.6°C). Birds in other 4 treatment groups were subjected to a cyclic HS by exposing them to 32 ± 0.9°C for 8 h/d (from 09:00 to 17:00 h) and 28 ± 1.2°C for the remaining time for 14 d. Birds were fed a basal diet in TN condition (TN-C) and one group in HS conditions (HS-C), whereas other birds raised under HS conditions were fed the basal diet supplemented with 0.20% Bet (HS-Bet), 0.79% Gly (HS-Gly), or their combination (0.20% Bet + 0.79% Gly; HS-Bet+Gly). Results indicated that birds in HS-Bet, HS-Gly, or HS-Bet+Gly treatment had higher (P < 0.05) final BW and BW gain, but lower (P < 0.05) feed conversion ratio (FCR) than those in HS-C treatment. However, values for improved final BW, BW gain, and FCR by dietary treatments were lower (P < 0.05) than those measured in TN-C treatment. Under HS conditions, birds in HS-Bet, HS-Gly, or HS-Bet+Gly treatment had lower (P < 0.05) heterophil to lymphocyte ratio than those in HS-C treatment. Birds in HS-Gly or HS-Bet+Gly treatment had higher (P < 0.05) villus height and goblet cell number than birds in HS-C treatment. Intestinal permeability was higher (P < 0.05) in all HS-treatment groups than in TN-C treatment, but it was not affected by dietary treatment. In conclusion, individual supplementation of 0.20% Bet or 0.79% Gly in diets alleviates the negative effect of HS in broiler chickens. However, the synergistic effect of the combination of 0.20% Bet and 0.79% Gly in broiler diets seems lower than expected.

Appraising the Role of Astrocytes as Suppliers of Neuronal Glutathione Precursors

The metabolism and intercellular transfer of glutathione or its precursors may play an important role in cellular defense against oxidative stress, a common hallmark of neurodegeneration. In the 1990s, several studies in the Neurobiology field led to the widely accepted notion that astrocytes produce large amounts of glutathione that serve to feed neurons with precursors for glutathione synthesis. This assumption has important implications for health and disease since a reduction in this supply from astrocytes could compromise the capacity of neurons to cope with oxidative stress. However, at first glance, this shuttling would imply a large energy expenditure to get to the same point in a nearby cell. Thus, are there additional underlying reasons for this expensive mechanism? Are neurons unable to import and/or synthesize the three non-essential amino acids that are the glutathione building blocks? The rather oxidizing extracellular environment favors the presence of cysteine (Cys) as cystine (Cis), less favorable for neuronal import. Therefore, it has also been proposed that astrocytic GSH efflux could induce a change in the redox status of the extracellular space nearby the neurons, locally lowering the Cis/Cys ratio. This astrocytic glutathione release would also increase their demand for precursors, stimulating Cis uptake, which these cells can import, further impacting the local decline of the Cis/Cys ratio, in turn, contributing to a more reduced extracellular environment and subsequently favoring neuronal Cys import. Here, we revisit the experimental evidence that led to the accepted hypothesis of astrocytes acting as suppliers of neuronal glutathione precursors, considering recent data from the Human Protein Atlas. In addition, we highlight some potential drawbacks of this hypothesis, mainly supported by heterogeneous cellular models. Finally, we outline additional and more cost-efficient possibilities by which astrocytes could support neuronal glutathione levels, including its shuttling in extracellular vesicles.

Dietary threonine improves muscle nutritional value and muscle hardness associated with collagen synthesis in grass carp (Ctenopharyngodon idella)

To further explain the improvement effect of threonine (Thr) on the fillet quality of fish, a 9-week feeding experiment was conducted. After feeding graded levels of Thr (2.38, 5.38, 8.38, 11.38, 14.38 and 17.38 g/kg), the compositions of fillet hydrolyzed amino acid and fatty acid, and the muscle hardness associated with collagen biosynthesis were mainly analyzed in grass carp (Ctenopharyngodon idella). The results showed that Thr increased the pH value, changed the amino acids and fatty acid composition of fillets, especially essential amino acid (EAA), C22:6n3 (DHA) and C20:5n3 (EPA). Furthermore, this study revealed for the first time that the improvement of muscle hardness by Thr was associated with collagen biosynthesis, and the TGF-β1/Smads, LARP6a and Hsp47 regulate transcriptional processes, translation initiation and post-translational modifications in collagen biosynthesis, respectively. This study offered a basis for exploring the contribution of Thr in improving muscle quality in sub-adult grass carp.

Mitochondrial DNA Supplementation of Oocytes Has Downstream Effects on the Transcriptional Profiles of Sus scrofa Adult Tissues with High mtDNA Copy Number

Oocytes can be supplemented with extra copies of mitochondrial DNA (mtDNA) to enhance developmental outcome. Pigs generated through supplementation with mtDNA derived from either sister (autologous) or third-party (heterologous) oocytes have been shown to exhibit only minor differences in growth, physiological and biochemical assessments, and health and well-being do not appear affected. However, it remains to be determined whether changes in gene expression identified during preimplantation development persisted and affected the gene expression of adult tissues indicative of high mtDNA copy number. It is also unknown if autologous and heterologous mtDNA supplementation resulted in different patterns of gene expression. Our transcriptome analyses revealed that genes involved in immune response and glyoxylate metabolism were commonly affected in brain, heart and liver tissues by mtDNA supplementation. The source of mtDNA influenced the expression of genes associated with oxidative phosphorylation (OXPHOS), suggesting a link between the use of third-party mtDNA and OXPHOS. We observed a significant difference in parental allele-specific imprinted gene expression in mtDNA-supplemented-derived pigs, with shifts to biallelic expression with no effect on expression levels. Overall, mtDNA supplementation influences the expression of genes in important biological processes in adult tissues. Consequently, it is important to determine the effect of these changes on animal development and health.

Terminalia bellirica ethanol extract ameliorates nonalcoholic fatty liver disease in mice by amending the intestinal microbiota and faecal metabolites

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia bellirica (Gaertn.) Roxb. (TB) is a traditional Tibetan medicine used to treat hepatobiliary diseases. However, modern pharmacological evidence of the activities and potential mechanisms of TB against nonalcoholic fatty liver disease (NAFLD) are still unknown.

AIM OF THE STUDY

This study aimed to evaluate the anti-NAFLD effect of ethanol extract of TB (ETB) and investigate whether its ameliorative effects are associated with the regulation of intestinal microecology.

MATERIALS AND METHODS

In this study, the curative effects of ETB on NAFLD were evaluated in mice fed a choline-deficient, L-amino acid defined, high fat diet (CDAHFD). Biochemical markers and hepatic histological alterations were detected. Gut microbiota and faecal metabolites were analyzed by 16S rRNA gene sequencing and liquid chromatograph mass spectrometer (LC‒MS) profiling.

RESULTS

The results showed that oral treatment with middle- and high-dose ETB significantly improved features of NAFLD, reducing the levels of TG, LDL-C, ALT and AST, and increasing the level of HDL-C. Liver histopathologic examination demonstrated that ETB attenuated lipid accumulation and hepatocellular necrosis. ETB treatment restored the structural disturbances of gut microbiota induced by CDAHFD, reduced the levels of Intestinimonas, Lachnoclostridium, and Lachnospirace-ae_FCS020_group, and increased Akkermansia and Bifidobacterium. Moreover, untargeted metabolomics analysis revealed that ETB could restore the disrupted taurine and hypotaurine metabolism, glycine, serine and threonine metabolism, and glutathione metabolism of the intestinal bacterial community in NAFLD mice.

CONCLUSIONS

ETB was effective in ameliorating the NAFLD, possibly by remodelling the gut microbiota composition and modulating the faecal metabolism metabolites of the host, highlighting the potential of TB as a resource for the development of anti-NAFLD drugs.

Abundance of Amino Acid Transporters and mTOR Pathway Components in the Gastrointestinal Tract of Lactating Holstein Cows

Data from non-ruminants indicate that amino acid (AA) transport into cells can regulate mTOR pathway activity and protein synthesis. Whether mTOR is expressed in the ruminant gastrointestinal tract (GIT) and how it may be related to AA transporters and the AA concentrations in the tissue is unknown. Ruminal papillae and the epithelia of the duodenum, jejunum, and ileum collected at slaughter from eight clinically healthy Holstein in mid-lactation were used. Metabolites and RNA were extracted from tissue for liquid chromatography–mass spectrometry and RT-qPCR analysis. The glycine and asparagine concentrations in the rumen were greater than those in the intestine (p < 0.05), but the concentrations of other AAs were greater in the small intestine than those in the rumen. Among the 20 AAs identified, the concentrations of glutamate, alanine, and glycine were the greatest. The mRNA abundances of AKT1 and MTOR were greater in the small intestine than those in the rumen (p < 0.05). Similarly, the SLC1A1, SLC6A6, SLC7A8, SLC38A1, SLC38A7, and SLC43A2 mRNA abundances were greater (p < 0.05) in the small intestine than those in the rumen. The mRNA abundances of SLC1A5, SLC3A2, and SLC7A5 were greater in the rumen than those in the small intestine (p < 0.05). Overall, the present study provides fundamental data on the relationship between mTOR pathway components and the transport of AAs in different sections of the gastrointestinal tract.

Glycine and aging: Evidence and mechanisms

The restriction of calories, branched-chain amino acids, and methionine have all been shown to extend lifespan in model organisms. Recently, glycine was shown to significantly boost longevity in genetically heterogenous mice. This simple amino acid similarly extends lifespan in rats and improves health in mammalian models of age-related disease. While compelling data indicate that glycine is a pro-longevity molecule, divergent mechanisms may underlie its effects on aging. Glycine is abundant in collagen, a building block for glutathione, a precursor to creatine, and an acceptor for the enzyme Glycine N-methyltransferase (GNMT). A review of the literature strongly implicates GNMT, which clears methionine from the body by taking a methyl group from S-adenosyl-L-methionine and methylating glycine to form sarcosine. In flies, Gnmt is required for reduced insulin/insulin-like growth factor 1 signaling and caloric restriction to fully extend lifespan. The geroprotector spermidine requires Gnmt to upregulate autophagy genes and boost longevity. Moreover, the overexpression of Gnmt is sufficient to extend lifespan and reduce methionine levels. Sarcosine, or methylglycine, declines with age in multiple species and is capable of inducing autophagy both in vitro and in vivo. Taken all together, existing evidence suggests that glycine prolongs life by mimicking methionine restriction and activating autophagy.

Transcriptome analysis reveals effects of leukemogenic SHP2 mutations in biosynthesis of amino acids signaling

Gain-of-function mutations of SHP2, especially D61Y and E76K, lead to the development of neoplasms in hematopoietic cells. Previously, we found that SHP2-D61Y and -E76K confer HCD-57 cells cytokine-independent survival and proliferation via activation of MAPK pathway. Metabolic reprogramming is likely to be involved in leukemogenesis led by mutant SHP2. However, detailed pathways or key genes of altered metabolisms are unknown in leukemia cells expressing mutant SHP2. In this study, we performed transcriptome analysis to identify dysregulated metabolic pathways and key genes using HCD-57 transformed by mutant SHP2. A total of 2443 and 2273 significant differentially expressed genes (DEGs) were identified in HCD-57 expressing SHP2-D61Y and -E76K compared with parental cells as the control, respectively. Gene ontology (GO) and Reactome enrichment analysis showed that a large proportion of DEGs were involved in the metabolism process. Kyoto Encyclopedia of Gene and Genome (KEGG) pathway enrichment analysis showed that DEGs were the mostly enriched in glutathione metabolism and biosynthesis of amino acids in metabolic pathways. Gene Set Enrichment Analysis (GSEA) revealed that the expression of mutant SHP2 led to a significant activation of biosynthesis of amino acids pathway in HCD-57 expressing mutant SHP2 compared with the control. Particularly, we found that ASNS, PHGDH, PSAT1, and SHMT2 involved in the biosynthesis of asparagine, serine, and glycine were remarkably up-regulated. Together, these transcriptome profiling data provided new insights into the metabolic mechanisms underlying mutant SHP2-driven leukemogenesis.

Prediction of Busulfan Clearance by Predose Plasma Metabolomic Profiling

Intravenous busulfan doses are often personalized to a target plasma exposure (targeted busulfan) using an individual's busulfan clearance (BuCL). We evaluated whether BuCL could be predicted by a predose plasma panel of 841 endogenous metabolomic compounds (EMCs). In this prospective cohort of 132 hematopoietic cell transplantation (HCT) patients, all had samples collected immediately before busulfan administration (preBU) and 96 had samples collected 2 weeks before busulfan (2-week-preBU). BuCL was significantly associated with 37 EMCs after univariate linear regression analysis and controlling for false discovery (< 0.05) in the 132 preBU samples. In parallel, with preBU samples, we included all 841 EMCs in a least absolute shrinkage and selection operator-penalized regression which selected 13 EMCs as predominantly associated with BuCL. Then, we constructed a prediction model by estimating coefficients for these 13 EMCs, along with sex, using ordinary least-squares. When the resulting linear prediction model was applied to the 2-week-preBU samples, it explained 40% of the variation in BuCL (adjusted R²  = 0.40). Pathway enrichment analysis revealed 18 pathways associated with BuCL. Lysine degradation followed by steroid biosynthesis, which aligned with the univariate analysis, were the top two pathways. BuCL can be predicted before busulfan administration with a linear regression model of 13 EMCs. This pharmacometabolomics method should be prioritized over use of a busulfan test dose or pharmacogenomics to guide busulfan dosing. These results highlight the potential of pharmacometabolomics as a precision medicine tool to improve or replace pharmacokinetics to personalize busulfan doses.

Causal effects of maternal circulating amino acids on offspring birthweight: a Mendelian randomisation study

BACKGROUND

Amino acids are key to protein synthesis, energy metabolism, cell signaling and gene expression; however, the contribution of specific maternal amino acids to fetal growth is unclear.

METHODS

We explored the effect of maternal circulating amino acids on fetal growth, proxied by birthweight, using two-sample Mendelian randomisation (MR) and summary data from a genome-wide association study (GWAS) of serum amino acids levels (sample 1, n = 86,507) and a maternal GWAS of offspring birthweight in UK Biobank and Early Growth Genetics Consortium, adjusting for fetal genotype effects (sample 2, n = 406,063 with maternal and/or fetal genotype effect estimates). A total of 106 independent single nucleotide polymorphisms robustly associated with 19 amino acids (p < 4.9 × 10-10) were used as genetic instrumental variables (IV). Wald ratio and inverse variance weighted methods were used in MR main analysis. A series of sensitivity analyses were performed to explore IV assumption violations.

FINDINGS

Our results provide evidence that maternal circulating glutamine (59 g offspring birthweight increase per standard deviation increase in maternal amino acid level, 95% CI: 7, 110) and serine (27 g, 95% CI: 9, 46) raise, while leucine (-59 g, 95% CI: -106, -11) and phenylalanine (-25 g, 95% CI: -47, -4) lower offspring birthweight. These findings are supported by sensitivity analyses.

INTERPRETATION

Our findings strengthen evidence for key roles of maternal circulating amino acids during pregnancy in healthy fetal growth.

FUNDING

A full list of funding bodies that contributed to this study can be found under Acknowledgments.

A new technique to study nutrient flow in host-parasite systems by carbon stable isotope analysis of amino acids and glucose

Stable isotope analysis of individual compounds is emerging as a powerful tool to study nutrient origin and conversion in host-parasite systems. We measured the carbon isotope composition of amino acids and glucose in the cestode Schistocephalus solidus and in liver and muscle tissues of its second intermediate host, the three-spined stickleback (Gasterosteus aculeatus), over the course of 90 days in a controlled infection experiment. Similar linear regressions of δ¹³C values over time and low trophic fractionation of essential amino acids indicate that the parasite assimilates nutrients from sources closely connected to the liver metabolism of its host. Biosynthesis of glucose in the parasite might occur from the glucogenic precursors alanine, asparagine and glutamine and with an isotope fractionation of - 2 to - 3 ‰ from enzymatic reactions, while trophic fractionation of glycine, serine and threonine could be interpreted as extensive nutrient conversion to fuel parasitic growth through one-carbon metabolism. Trophic fractionation of amino acids between sticklebacks and their diets was slightly increased in infected compared to uninfected individuals, which could be caused by increased (immune-) metabolic activities due to parasitic infection. Our results show that compound-specific stable isotope analysis has unique opportunities to study host and parasite physiology.

Glycine homeostasis requires reverse SHMT flux

The folate-dependent enzyme serine hydroxymethyltransferase (SHMT) reversibly converts serine into glycine and a tetrahydrofolate-bound one-carbon unit. Such one-carbon unit production plays a critical role in development, the immune system, and cancer. Here we show that the whole-body SHMT flux acts to net consume rather than produce glycine. Pharmacological inhibition of whole-body SHMT1/2 and genetic knockout of liver SHMT2 elevated circulating glycine levels up to eight-fold. Stable isotope tracing revealed that the liver converts glycine to serine, which is then converted by serine dehydratase into pyruvate and burned in the tricarboxylic acid cycle. In response to diets deficient in serine and glycine, de novo biosynthetic flux was unaltered but SHMT2- and serine dehydratase-mediated catabolic flux was lower. Thus, glucose-derived serine synthesis does not respond to systemic demand. Instead, circulating serine and glycine homeostasis is maintained through variable consumption, with liver SHMT2 as a major glycine-consuming enzyme.

Preparing Patients for Cosmetic Surgery and Aesthetic Procedures: Ensuring an Optimal Nutritional Status for Successful Results

Aesthetic and cosmetic medical practices have attracted considerable consumer attention globally. However, possible complications vary and range from mild, self-resolving ecchymoses or edema to more persistent complications. The aim of this review is to identify the nutritional deficits or excesses associated with the major complications of reconstructive surgery, aesthetic surgery, and mini-invasive aesthetic procedures. An additional goal is to provide a bundle of actions for professionals working in the industry in order to reduce the risks of aesthetic procedures and improve the clinical outcomes. Granulomas, hypertrophic scars and keloids, seromas, infections and xerosis, hyperpigmentation, petechiae, livedo reticularis, slower wound healing, and other poor outcomes are frequently associated with nutritional deficiencies. Nutritional status can markedly affect wound healing and tissue repair following surgical interventions, as well as the outcomes of aesthetic and cosmetic medical practices. Professionals working in this industry, therefore, need to consider the nutritional aspects of their patients to obtain the best results.

Dietary glycine supplementation improves the growth performance of 110- to 240-g (phase II) hybrid striped bass (Morone saxatilis ♀× Morone chrysops ♂) fed soybean meal-based diets

We recently reported that supplementing glycine to soybean meal (SBM)-based diets is necessary for optimum growth of 5- to 40-g (phase I) hybrid striped bass (HSB). The present study tested the hypothesis that supplementing glycine to SBM-based diets may enhance the growth of 110- to 240-g (phase II) HSB. HSB (the initial body weight of approximately 110 g) were fed an SBM (58%)-based diet supplemented with 0%, 1%, or 2% of glycine, with l-alanine serving as the isonitrogenous control. There were four tanks per dietary group, with four fish per tank. The fish were fed their respective diets to apparent satiation twice daily. The feed intake and body weight of fish were recorded daily and every 2 wk, respectively. At the end of the 56-d feeding trial, plasma and tissue samples were collected to determine amino acid concentrations and histological alterations, and tissues were used to measure the oxidation of l-glutamate, l-glutamine, l-aspartate, and glycine. Results showed that dietary supplementation with 1% and 2% glycine dose-dependently increased (P < 0.05) the concentration of glycine in the plasma of HSB by 48% and 99%, respectively. Compared with the 0%-glycine group, dietary supplementation with 1% glycine did not affect (P > 0.05) the feed intake of HSB but increased (P < 0.05) their final body weight, weight gain, and gain:feed ratio during the whole period by 13%, 29%, and 21%, respectively. Compared with the 1% glycine group, dietary supplementation with 2% glycine increased (P < 0.05) the feed intake, final body weight, and weight gain of HSB by 13%, 7%, and 14%, respectively. Compared with the 0%-glycine group, fish fed with the 1%-glycine and 2%-glycine diets had a greater (P < 0.05) villus height in the proximal intestine, when compared with the 0%-glycine group. Collectively, these results indicated that SBM-based diets did not provide sufficient glycine for phase II HSB (110 to 240 g) and that dietary glycine supplementation is essential for their optimum growth and intestinal structure.

One-carbon metabolism and related pathways in ruminal and small intestinal epithelium of lactating dairy cows

Physiological and environmental stresses such as the transition into lactation and heat load contribute to gastrointestinal tract (GIT) dysfunction. The nonruminant gastrointestinal tract has mechanisms to cope with pro-oxidant and pro-inflammatory stressors arising from the gut lumen or within intestinal cells. One-carbon metabolism (OCM) contributes to anti-oxidant capacity via the production of glutathione (GSH) and taurine, and the synthesis of phospholipid, creatine, and the osmolyte glycinebetaine among others. A multipronged approach was used to assess the biological relevance of OCM and closely-related pathways on GIT function in dairy cows. Ruminal papillae (Rum) and scrapings from duodenum (Duo), jejunum (Jej), and ileum (Ile) were collected at slaughter from eight multiparous Holstein cows averaging 128 ± 12 d in milk and producing 39 ± 5 kg/d. A MIXED model ANOVA with preplanned orthogonal contrasts was used for statistical analysis. Methionine adenosyl transferase 1 activity (MAT) was ~10-fold greater (P < 0.01) and cystathionine β-synthase activity doubled in Rum vs. small intestine. Total glutathione peroxidase (GPX) activity was greatest (P = 0.03) in Ile, but similar to Rum. Activity and mRNA abundance of betaine-homocysteine S-methyltransferase were undetectable. There was a 2.5-fold greater protein abundance of GPX1 (P < 0.01) and a ~2-fold greater abundance of GPX3 (P < 0.01) in Rum vs. small intestine. Among the various amino acids (AA) with roles in OCM or closely-related pathways (e.g. creatine synthesis), concentrations of arginine, aspartate, glutamine, methionine, and serine were lower (P < 0.01) in Rum vs. small intestine. Unlike AA, concentrations of OCM-related intermediates S-5'-adenosyl-homocysteine (SAH), glycinebetaine, carnitine, creatine (CRE), and cysteinesulfinic acid were greater (P < 0.01) while taurine was lower in Rum vs. small intestine. Intermediates of the folate cycle were undetectable. The fact that S-adenosylmethionine (SAM) was undetectable while MAT activity and SAH were greater in Rum suggested that availability of SAM (a methyl donor) is a key determinant of flux through the folate and methionine cycles in the GIT. Except for adenosine, concentrations of glutamate, glycine, α-ketoglutarate, hypotaurine, and GSH were lowest in Ile. Together, the data underscored unique differences in activity of one-carbon metabolism and related pathways across sections of the GIT.

Dietary glycine supplementation enhances the growth performance of hybrid striped bass (Morone saxatilis ♀× Morone chrysops ♂) fed soybean meal-based diets

This study was conducted to test the hypothesis that supplementing 1% and 2% glycine to soybean meal (SBM)-based diets can improve the growth performance of juvenile hybrid striped bass (HSB). The basal diets contained 15% fishmeal and 58% SBM (DM basis). Alanine was used as the isonitrogenous control in different diets. All diets contained 44% crude protein and 10% lipids (DM basis). There were four tanks (15 fish per tank) per dietary group, with the mean of the initial body weight (BW) of fish being 5.3 g. Fish were fed to apparent satiation twice daily, and their BW was recorded every 2 wk. The trial lasted for 8 wk. Results indicated that the BW, weight gain, protein efficiency ratio, and retention of dietary lipids in fish were enhanced (P < 0.05) by dietary supplementation with 1% or 2% glycine. In addition, dietary supplementation with glycine did not affect (P > 0.05) the feed intake of fish but increased (P < 0.05) the retention of dietary nitrogen, most amino acids, and phosphorus in the body, compared to the 0% glycine group. Dietary supplementation with 1% and 2% glycine dose-dependently augmented (P < 0.05) the villus height of the proximal intestine and reduced the submucosal thickness of the gut, while preventing submucosal and lamina propria hemorrhages. Compared with the 0% glycine group, dietary supplementation with 1% or 2% glycine decreased (P < 0.05) the proportion of skeletal-muscle fibers with diameters of 40 to 60 µm but increased (P < 0.05) the proportion of skeletal-muscle fibers with diameters of 80 to 100 µm and > 100 µm. Collectively, these findings indicate that glycine in SBM-based diets is inadequate for maximum growth of juvenile HSB and that dietary supplementation with 1% or 2% glycine is required to improve their weight gain and feed efficiency. Glycine is a conditionally essential amino acid for this fish.

Functional properties of amino acids: improve health status and sustainability

The combination of increased genetic potential and changes in management strategies (i.e., antibiotic-free, no antibiotics ever, and every day feeding of replacement pullets) influences the nutritional needs of poultry. Traditionally, nutritionists have focused on meeting the amino acid needs for production performance and yield however, increasing specific amino acid concentrations can benefit gastrointestinal development and integrity, enhance immune response potential, influence behavior, and benefit sustainability. Commercialization of additional feed grade amino acids beyond methionine, lysine, and threonine, enables targeted increases to achieve these benefits. As such, this paper addresses the functional roles of amino acids in meeting poultry production, health, and sustainability goals.

The interplay between nonalcoholic fatty liver disease and atherosclerotic cardiovascular disease

Therapeutic approaches that lower circulating low-density lipoprotein (LDL)-cholesterol significantly reduced the burden of cardiovascular disease over the last decades. However, the persistent rise in the obesity epidemic is beginning to reverse this decline. Alongside obesity, the incidence of nonalcoholic fatty liver disease (NAFLD) has substantially increased in the last three decades. Currently, approximately one third of world population is affected by NAFLD. Notably, the presence of NAFLD and particularly its more severe form, nonalcoholic steatohepatitis (NASH), serves as an independent risk factor for atherosclerotic cardiovascular disease (ASCVD), thus, raising interest in the relationship between these two diseases. Importantly, ASCVD is the major cause of death in patients with NASH independent of traditional risk factors. Nevertheless, the pathophysiology linking NAFLD/NASH with ASCVD remains poorly understood. While dyslipidemia is a common risk factor underlying both diseases, therapies that lower circulating LDL-cholesterol are largely ineffective against NASH. While there are no approved pharmacological therapies for NASH, some of the most advanced drug candidates exacerbate atherogenic dyslipidemia, raising concerns regarding their adverse cardiovascular consequences. In this review, we address current gaps in our understanding of the mechanisms linking NAFLD/NASH and ASCVD, explore strategies to simultaneously model these diseases, evaluate emerging biomarkers that may be useful to diagnose the presence of both diseases, and discuss investigational approaches and ongoing clinical trials that potentially target both diseases.

Mechanism of skeletal muscle atrophy after spinal cord injury: A narrative review

Spinal cord injury leads to loss of innervation of skeletal muscle, decreased motor function, and significantly reduced load on skeletal muscle, resulting in atrophy. Factors such as braking, hormone level fluctuation, inflammation, and oxidative stress damage accelerate skeletal muscle atrophy. The atrophy process can result in skeletal muscle cell apoptosis, protein degradation, fat deposition, and other pathophysiological changes. Skeletal muscle atrophy not only hinders the recovery of motor function but is also closely related to many systemic dysfunctions, affecting the prognosis of patients with spinal cord injury. Extensive research on the mechanism of skeletal muscle atrophy and intervention at the molecular level has shown that inflammation and oxidative stress injury are the main mechanisms of skeletal muscle atrophy after spinal cord injury and that multiple pathways are involved. These may become targets of future clinical intervention. However, most of the experimental studies are still at the basic research stage and still have some limitations in clinical application, and most of the clinical treatments are focused on rehabilitation training, so how to develop more efficient interventions in clinical treatment still needs to be further explored. Therefore, this review focuses mainly on the mechanisms of skeletal muscle atrophy after spinal cord injury and summarizes the cytokines and signaling pathways associated with skeletal muscle atrophy in recent studies, hoping to provide new therapeutic ideas for future clinical work.

gldc Is Essential for Renal Progenitor Patterning during Kidney Development

The glycine cleavage system (GCS) is a complex located on the mitochondrial membrane that is responsible for regulating glycine levels and contributing one-carbon units to folate metabolism. Congenital mutations in GCS components, such as glycine decarboxylase (gldc), cause an elevation in glycine levels and the rare disease, nonketotic hyperglycinemia (NKH). NKH patients suffer from pleiotropic symptoms including seizures, lethargy, mental retardation, and early death. Therefore, it is imperative to fully elucidate the pathological effects of gldc dysfunction and glycine accumulation during development. Here, we describe a zebrafish model of gldc deficiency that recapitulates phenotypes seen in humans and mice. gldc deficient embryos displayed impaired fluid homeostasis suggesting renal abnormalities, as well as aberrant craniofacial morphology and neural development defects. Whole mount in situ hybridization (WISH) revealed that gldc transcripts were highly expressed in the embryonic kidney, as seen in mouse and human repository data, and that formation of several nephron segments was disrupted in gldc deficient embryos, including proximal and distal tubule populations. These kidney defects were caused by alterations in renal progenitor populations, revealing that the proper function of Gldc is essential for the patterning of this organ. Additionally, further analysis of the urogenital tract revealed altered collecting duct and cloaca morphology in gldc deficient embryos. Finally, to gain insight into the molecular mechanisms underlying these disruptions, we examined the effects of exogenous glycine treatment and observed analogous renal and cloacal defects. Taken together, these studies indicate for the first time that gldc function serves an essential role in regulating renal progenitor development by modulating glycine levels.

MOLECULAR MECHANISMS DEFINING APPLICATION OF GLYCINE AND ZINC COMBINATIONIN CORRECTION OF STRESS AND ANXIETY MAIN MANIFESTATIONS

The aim of the work was to carry out a systematic analysis of the molecular mechanisms that determine the possibility of a combined use of amino acid glycine and zinc compounds for the treatment of patients with manifestations of stress and anxiety.

Materials and methods. Information retrieval (Scopus, PubMed) and library (eLibrary) databases were used as research tools. In some cases, the ResearchGate application was applied for a semantic search. The analysis and generalization of references was carried out on the research topic, covering the period from 2000 to the present time.

Results. It has been shown that amino acid glycine, along with gamma-aminobutyric acid (GABA), is a key neurotransmitter that regulates physiological inhibition processes in the central nervous system (CNS) by increasing transmembrane conductance in specific pentameric ligand-gated ion channels. The introduction of zinc ions can potentiate the opening of these receptors by increasing their affinity for glycine, resulting in an inhibitory processes increase in CNS neurons. The replenishment of the glycine and zinc combined deficiency is an important element in the correction of a post-stress dysfunction of the central nervous system. A balanced intake of zinc and glycine is essential for most people who experience daily effects of multiple stresses and anxiety. This combination is especially useful for the people experiencing a state of chronic psycho-emotional stress and maladaptation, including those who have a difficulty in falling asleep.

Conclusion. A balanced maintenance of the zinc and glycine concentration in the body of a healthy person leads to the development of a stable anti-anxiety effect, which is accompanied by the normalization of the sleep-wake rhythm, which makes it possible to have a good rest without any loss of working efficiency after waking up.

Dietary glycine supplementation prevents heat stress-induced impairment of antioxidant status and intestinal barrier function in broilers

This study tested the hypothesis that glycine improves intestinal barrier function through regulating oxidative stress in broilers exposed to heat stress. A total of 300 twenty-one-day-old female Arbor Acres broilers (600 ± 2.5g) was randomly allocated to 5 treatments (6 replicate of 10 birds each). The 5 treatments were as follows: the control group (CON) was kept under thermoneutral condition (24 ± 1°C) and was fed a basal diet. Broilers fed a basal diet and reared under high ambient temperature (HT) were considered as the HT group (34 ± 1°C for 8 h/d). Broilers fed a basal diet supplemented with 0.5%, 1.0%, and 2.0% glycine and exposed to HT were regarded as the HT + glycine treatments. The results exhibited that heat stress reduced growth performance, serum total antioxidant capacity (T-AOC), and glutathione (GSH) concentration (P < 0.05); increased activity of serum catalase (CAT) and the contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) (P < 0.05). HT exposure led to downregulating the mRNA expression of NAD(P)H quinone dehydrogenase 1 (NQO1), Occludin, and zonula occludens-1 (ZO-1) (P < 0.05); enhanced the mRNA levels of Kelch-like ECH-associated protein 1 (Keap1), CAT, glutathione synthetase (GSS), and glutamate-cysteine ligase modifier subunit (GCLM) (P < 0.05); impaired the intestinal morphology (P < 0.05); and altered the diversity and community of gut microbiota (P < 0.05). The final body weight (FBW), ADFI, ADG, and gain-to-feed ratio (G: F) increased linearly or quadratically, and the antioxidant capacity was improved (P < 0.05) with glycine supplementation. Glycine treatment increased the villus height (VH), and villus height to crypt depth ratio (V/C) of the duodenum linearly or quadratically, and linearly increased the VH of jejunum and ileum. The mRNA expression of Occludin, and ZO-1 were increased linearly in the ileum mucosa of broilers subjected to HT. Collectively, these results demonstrated that glycine supplementation alleviates heat stress-induced dysfunction of antioxidant status and intestinal barrier in broilers.

Insights into diet-associated oxidative pathomechanisms in inflammatory bowel disease and protective effects of functional amino acids

There has been a substantial rise in the incidence and prevalence of clinical patients presenting with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. Accumulating evidence has corroborated the view that dietary factors (particularly diets with high levels of saturated fat or sugar) are involved in the development and progression of IBD, which is predominately associated with changes in the composition of the gut microbiota and an increase in the generation of reactive oxygen species. Notably, the ecological imbalance of the gut microbiome exacerbates oxidative stress and inflammatory responses, leading to perturbations of the intestinal redox balance and immunity, as well as mucosal integrity. Recent findings have revealed that functional amino acids, including L-glutamine, glycine, L-arginine, L-histidine, L-tryptophan, and hydroxyproline, are effectively implicated in the maintenance of intestinal redox and immune homeostasis. These amino acids and their metabolites have oxygen free-radical scavenging and inflammation-relieving properties, and they participate in modulation of the microbial community and the metabolites in the gut. The principal focus of this article is a review of recent advances in the oxidative pathomechanisms of IBD development and progression in relation to dietary factors, with a particular emphasis on the redox and signal transduction mechanisms of host cells in response to unbalanced diets and enterobacteria. In addition, an update on current understanding of the protective effects of functional amino acids against IBD, together with the underlying mechanisms for this protection, have been provided.