Cytotoxicity and mitochondrial dysfunction caused by the dietary supplement l-norvaline

Alterations in intestinal microbiota and metabolites in individuals with Down syndrome and their correlation with inflammation and behavior disorders in mice

The intestinal microbiota and fecal metabolome have been shown to play a vital role in human health, and can be affected by genetic and environmental factors. We found that individuals with Down syndrome (DS) had abnormal serum cytokine levels indicative of a pro-inflammatory environment. We investigated whether these individuals also had alterations in the intestinal microbiome. High-throughput sequencing of bacterial 16S rRNA gene in fecal samples from 17 individuals with DS and 23 non-DS volunteers revealed a significantly higher abundance of Prevotella, Escherichia/Shigella, Catenibacterium, and Allisonella in individuals with DS, which was positively associated with the levels of pro-inflammatory cytokines. GC-TOF-MS-based fecal metabolomics identified 35 biomarkers (21 up-regulated metabolites and 14 down-regulated metabolites) that were altered in the microbiome of individuals with DS. Metabolic pathway enrichment analyses of these biomarkers showed a characteristic pattern in DS that included changes in valine, leucine, and isoleucine biosynthesis and degradation; synthesis and degradation of ketone bodies; glyoxylate and dicarboxylate metabolism; tyrosine metabolism; lysine degradation; and the citrate cycle. Treatment of mice with fecal bacteria from individuals with DS or Prevotella copri significantly altered behaviors often seen in individuals with DS, such as depression-associated behavior and impairment of motor function. These studies suggest that changes in intestinal microbiota and the fecal metabolome are correlated with chronic inflammation and behavior disorders associated with DS.

L-norvaline affects the proliferation of breast cancer cells based on the microbiome and metabolome analysis

AIMS

The altered fecal metabolites and microbiota might be involved in the development of breast cancer. We aimed to investigate the effect of differential metabolites on the proliferative activity of breast cancer cells.

METHODS AND RESULTS

We collected fecal samples from 14 breast cancer patients and 14 healthy subjects. Untargeted metabolomics analysis, short-chain fatty acid (SCFA) targeted analysis, and 16S rDNA sequencing was performed. The gut metabolite composition of patients changed significantly. Levels of norvaline, glucuronate, and galacturonate were lower in the Cancer group than in the Control (p < 0.05). 4-Methylcatechol and guaiacol increased (p < 0.05). Acetic acid and butyric acid were lower in the Cancer group than in the Control group (p < 0.05). Isobutyric acid and pentanoic acid were higher in the Cancer group than in the Control (p < 0.05). In the genus, the abundance of Rothia and Actinomyces increased in the Cancer group, compared with the Control group (p < 0.05). The differential microbiotas were clearly associated with differential metabolites but weakly with SCFAs. The abundance of Rothia and Actinomyces was markedly positively correlated with 4-methylcatechol and guaiacol (p < 0.05) and negatively correlated with norvaline (p < 0.05). L-norvaline inhibited the content of Arg-1 in a concentration-dependent manner. Compared with the L-norvaline or doxorubicin hydrochloride (DOX) group, the proliferation abilities of 4T1 cells were the lowest in the L-norvaline combined with DOX (p < 0.05). The apoptosis rate increased (p < 0.05).

CONCLUSIONS

Fecal metabolites and microbiota were significantly altered in breast cancer. Levels of differential metabolites (i.e., Norvaline) were significantly correlated with the abundance of differential microbiota. L-norvaline combined with DOX could clearly inhibit the proliferation activity of breast cancer cells.

SIGNIFICANCE AND IMPACT OF STUDY

This might provide clues to uncover potential biomarkers for breast cancer diagnosis and treatment.

Acute hypoxia elevates arginase 2 and induces polyamine stress response in zebrafish via evolutionarily conserved mechanism

Living organisms repeatedly encounter stressful events and apply various strategies to survive. Polyamines are omnipresent bioactive molecules with multiple functions. Their transient synthesis, inducible by numerous stressful stimuli, is termed the polyamine stress response. Animals developed evolutionarily conserved strategies to cope with stresses. The urea cycle is an ancient attribute that deals with ammonia excess in terrestrial species. Remarkably, most fish retain the urea cycle genes fully expressed during the early stages of development and silenced in adult animals. Environmental challenges instigate urea synthesis in fish despite substantial energetic costs, which poses the question of the urea cycle's evolutionary significance. Arginase plays a critical role in oxidative stress-dependent reactions being the final urea cycle enzyme. Its unique subcellular localization, high inducibility, and several regulation levels provide a supreme ability to control the polyamine synthesis rate. Notably, oxidative stress instigates the arginase-1 activity in mammals. Arginase is also dysregulated in aging organisms' brain and muscle tissues, indicating its role in the pathogenesis of age-associated diseases. We designed a study to investigate the levels of the urea cycle and polyamine synthesis-related enzymes in a fish model of acute hypoxia. We evidence synchronized elevation of arginase-2 and ornithine decarboxylase following oxidative stress in adult fish and aging animals signifying the specific function of arginase-2 in fish. Moreover, we demonstrate oxidative stress-associated polyamine synthesis' induction and urea cycle' arrest in adult fish. The subcellular arginase localization found in the fish seems to correspond to its possible evolutionary roles.

Fluorimetric Analysis of Five Amino Acids in Chocolate: Development and Validation

Amino acids present ergogenic action, helping to increase, protect, and restore the muscular system of young athletes. Moreover, the encapsulation of five relevant amino acids in chocolate pellet form will appeal to them, facilitating their daily consumption. A reliable HPLC fluorimetric method was developed to detect and quantitatively determine L-Leucine, L-Isoleucine, L-Histidine, L-Valine, and β-Alanine in chocolate using aniline as an internal standard. Experimental design methodology was used to investigate and optimize the clean-up procedure of the samples. Therefore, three extraction techniques (solid-phase extraction (by two different SPE cartridges) and liquid–solid extraction (LSE)) were compared and evaluated. The LOQ values in chocolate varied from 24 to 118 ng/g (recovery 89.7–95.6%, %RSD < 2.5). Amino acids were pre-column derivatized with o-phthalaldehyde (OPA), while derivatization parameters were thoroughly investigated by experimental design methodology. The analysis was performed by HPLC-fluorescence (emission: λ = 455 nm, excitation: λ = 340 nm) method using a C₁₈ column and a mixture of phosphate buffer (pH = 2.8; 20 mM)-methanol as a mobile phase in gradient elution. The method was validated (r² > 0.999, %RSD < 2, LOD: 10 ng mL⁻¹ for histidine and leucine, 2 ng mL⁻¹ for alanine and valine, and 4 ng mL⁻¹ for Isoleucine) according to the International Conference on Harmonization guidelines.

Misincorporation Proteomics Technologies: A Review

Proteinopathies are diseases caused by factors that affect proteoform conformation. As such, a prevalent hypothesis is that the misincorporation of noncanonical amino acids into a proteoform results in detrimental structures. However, this hypothesis is missing proteomic evidence, specifically the detection of a noncanonical amino acid in a peptide sequence. This review aims to outline the current state of technology that can be used to investigate mistranslations and misincorporations whilst framing the pursuit as Misincorporation Proteomics (MiP). The current availability of technologies explored herein is mass spectrometry, sample enrichment/preparation, data analysis techniques, and the hyphenation of approaches. While many of these technologies show potential, our review reveals a need for further development and refinement of approaches is still required.

Supplementation with γ-glutamylcysteine (γ-GC) lessens oxidative stress, brain inflammation and amyloid pathology and improves spatial memory in a murine model of AD

INTRODUCTION

The accumulation of oxidative stress, neuroinflammation and abnormal aggregation of amyloid β-peptide (Aβ) have been shown to induce synaptic dysfunction and memory deficits in Alzheimer's disease (AD). Cellular depletion of the major endogenous antioxidant Glutathione (GSH) has been linked to cognitive decline and the development of AD pathology. Supplementation with γ-glutamylcysteine (γ-GC), the immediate precursor and the limiting substrate for GSH biosynthesis, can transiently augment cellular GSH levels by bypassing the regulation of GSH homeostasis.

METHODS

In the present study, we investigated the effect of dietary supplementation of γ-GC on oxidative stress and Aβ pathology in the brains of APP/PS1 mice. The APP/PS1 mice were fed γ-GC from 3 months of age with biomarkers of apoptosis and cell death, oxidative stress, neuroinflammation and Aβ load being assessed at 6 months of age.

RESULTS

Our data showed that supplementation with γ-GC lowered the levels of brain lipid peroxidation, protein carbonyls and apoptosis, increased both total GSH and the glutathione/glutathione disulphide (GSH/GSSG) ratio and replenished ATP and the activities of the antioxidant enzymes (superoxide dismutase (SOD), catalase, glutamine synthetase and glutathione peroxidase (GPX)), the latter being a key regulator of ferroptosis. Brain Aβ load was lower and acetylcholinesterase (AChE) activity was markedly improved compared to APP/PS1 mice fed a standard chow diet. Alteration in brain cytokine levels and matrix metalloproteinase enzymes MMP-2 and MMP-9 suggested that γ-GC may lower inflammation and enhance Aβ plaque clearance in vivo. Spatial memory was also improved by γ-GC as determined using the Morris water maze.

CONCLUSION

Our data collectively suggested that supplementation with γ-GC may represent a novel strategy for the treatment and/or prevention of cognitive impairment and neurodegeneration.

Arginase inhibition by (-)-Epicatechin reverses endothelial cell aging

Endothelial dysfunction (EnD) occurs with aging and endothelial nitric oxide (NO) production by NO synthase (NOS) can be impaired. Low NO levels have been linked to increased arginase (Ar) activity as Ar competes with NOS for L-arginine. The inhibition of Ar activity can reverse EnD and (-)-epicatechin (Epi) inhibits myocardial Ar activity. In this study, through in silico modeling we demonstrate that Epi interacts with Ar similarly to its inhibitor Norvaline (Norv). Using in vitro and in vivo models of aging, we examined Epi and Norv-inhibition of Ar activity and its endothelium-protective effects. Bovine coronary artery endothelial cells (BCAEC) were treated with Norv (10 μM), Epi (1 μM) or the combination (Epi + Norv) for 48 h. Ar activity increased in aged BCAEC, with decreased NO generation. Treatment decreased Ar activity to levels seen in young cells. Epi and Epi + Norv decreased nitrosylated Ar levels by ~25% in aged cells with lower oxidative stress (~25%) (dihydroethidium) levels. In aged cells, Epi and Epi + Norv restored the eNOS monomer/dimer ratio, protein expression levels and NO production to those of young cells. Furthermore, using 18 month old rats 15 days of treatment with either Epi (1 mg/kg), Norv (10 mg/kg) or combo, decreased hypertension and improved aorta vasorelaxation to acetylcholine, blood NO levels and tetra/dihydribiopterin ratios in cultured rat aortic endothelial cells. In conclusion, results provide evidence that inhibiting Ar with Epi reverses aged-related loss of eNOS function and improves vascular function through the modulation of Ar and eNOS protein levels and activity.

Reports of L-Norvaline Toxicity in Humans May Be Greatly Overstated

Recently, a study published in “Toxicology In Vitro” (Kate Samardzic and Kenneth J. Rodgers) was entitled: “Cytotoxicity and Mitochondrial Dysfunction Caused by the Dietary Supplement L-Norvaline”. The title may be greatly overstated, and here we provide several arguments showing that norvaline is not as toxic as reported.

Target identification and intervention strategies against amebiasis

Entamoeba histolytica is the etiological agent of amebiasis, which is an endemic parasitic disease in developing countries and is the cause of approximately 70,000 deaths annually. E. histolytica trophozoites usually reside in the colon as a non-pathogenic commensal in most infected individuals (90% of infected individuals are asymptomatic). For unknown reasons, these trophozoites can become virulent and invasive, cause amebic dysentery, and migrate to the liver where they cause hepatocellular damage. Amebiasis is usually treated either by amebicides which are classified as (a) luminal and are active against the luminal forms of the parasite, (b) tissue and are effective against those parasites that have invaded tissues, and (c) mixed and are effective against the luminal forms of the parasite and those forms which invaded the host's tissues. Of the amebicides, the luminal amebicide, metronidazole (MTZ), is the most widely used drug to treat amebiasis. Although well tolerated, concerns about its adverse effects and the possible emergence of MTZ-resistant strains of E. histolytica have led to the development of new therapeutic strategies against amebiasis. These strategies include improving the potency of existing amebicides, discovering new uses for approved drugs (repurposing of existing drugs), drug rediscovery, vaccination, drug targeting of essential E. histolytica components, and the use of probiotics and bioactive natural products. This review examines each of these strategies in the light of the current knowledge on the gut microbiota of patients with amebiasis.