Methionine as a double-edged sword in health and disease: Current perspective and future challenges

L-methionine promotes CD8+ T cells killing hepatocellular carcinoma by inhibiting NR1I2/PCSK9 signaling

BACKGROUND

Liver cancer has consistently high incidence and mortality rates among malignant tumors. PCSK9, a target for hypercholesterolemia therapy, has recently been identified as an inhibitor of anti-tumor immunity, and targeting PCSK9 effectively inhibits tumor progression. However, small molecule inhibitors are lacking due to its flat protein structure.

METHODS

PCSK9 transcription inhibitor screening was conducted using a PCSK9 promoter-driven td-Tomato plasmid. Quantitative real-time PCR and immunoblotting were employed to assess the effect of L-methionine on PCSK9 expression in HCC cell lines. Co-culture experiments were performed to evaluate the impact of L-methionine on CD8+ T cell-mediated killing of liver cancer cells. RNA sequencing, CUT&Tag, gene editing, and luciferase reporter assays were utilized to identify the transcription factor regulating PCSK9. Additionally, liver cancer xenograft and spontaneous liver cancer mouse models were used to evaluate the anti-cancer efficacy of L-methionine.

RESULTS

Our study identified L-methionine, an essential amino acid, as a transcriptional inhibitor of PCSK9. The optimal dose of L-methionine to inhibit PCSK9 expression and enhance CD8+ T cell-mediated killing of liver cancer cells in vitro is 50 μM. Furthermore, intraperitoneal injection of 5 mg/kg/day of L-methionine significantly inhibited tumor growth in both liver cancer xenograft and spontaneous liver cancer mouse models. Mechanistically, we identified NR1I2 as a key transcription factor for PCSK9 and their crucial binding site was TGCACCCTGACAC. L-methionine inhibits PCSK9 transcription by downregulating NR1I2.

CONCLUSIONS

This work demonstrates that L-methionine promotes CD8+ T cell-mediated killing of hepatocellular carcinoma by inhibiting NR1I2/PCSK9 signaling. Our study introduces a novel and convenient approach to inhibit PCSK9 and provides a theoretical basis for the rational supplementation of L-methionine in liver cancer patients.

Role of the sulfur-containing amino acid-ROS axis in cancer chemotherapeutic drug resistance

Chemotherapeutic drug resistance remains a major barrier to effective cancer treatment. Drug resistance could be driven in part by adaptive redox remodeling of cancer cells. Paradoxically, drug-resistant malignancies exhibit elevated reactive oxygen species (ROS), as well as amplified antioxidant defenses, which enable cancer cell survival under therapeutic stress. Central to this adaptation is glutathione (GSH), the predominant cellular antioxidant, whose synthesis relies on sulfur-containing amino acids (SAAs) - methionine and cysteine. This review delineates the metabolic interplay between methionine and cysteine in the transsulfuration pathway, highlighting their roles as precursors in GSH biosynthesis. We systematically summarize the key enzymes that drive GSH production and their contributions to resistance against platinum-based drugs and other chemotherapeutics. In addition to GSH synthesis, we summarize the roles of GSH antioxidant systems, including glutathione peroxidases (GPXs), peroxiredoxins (PRDXs), and thioredoxins (TRXs), which are critical in chemotherapeutic drug resistance through ROS scavenging. Recent advances reveal that targeting these enzymes, by pharmacologically inhibiting transsulfuration enzymes or disrupting GSH-dependent antioxidant cascades, can sensitize resistant cancer cells to ROS-mediated therapies. These findings not only clarify the mechanistic links between SAA metabolism and redox adaptation but also provide practical approaches to overcome chemotherapeutic drug resistance. By analyzing metabolic and redox vulnerabilities, this review highlights the therapeutic potential to restore chemosensitivity, offering new options in precision oncology medicine.

The Use of [11C]C-Methionine in Diagnostics of Endocrine Disorders with Focus on Pituitary and Parathyroid Glands

The rapid development of nuclear medicine offers vast opportunities for diagnosing neoplasms, particularly in endocrinology. The use of the [11C]C-methionine radiotracer is currently limited due to its physical properties and the complex production process. However, studies conducted so far have demonstrated its utility in PET imaging, helping to detect lesions that often remain elusive with other modalities. This systematic review focuses on [11C]C-methionine in diagnosing hyperparathyroidism and pituitary tumors, highlighting its high effectiveness, which can be crucial in diagnosis. Despite some disadvantages, it should be considered when available, especially when other modalities or radiotracers fail.

Disrupted methionine cycle triggers muscle atrophy in cancer cachexia through epigenetic regulation of REDD1

The essential amino acid methionine plays a pivotal role in one-carbon metabolism, facilitating the production of S-adenosylmethionine (SAM), a critical supplier for DNA methylation and thereby a modulator of gene expression. Here, we report that the methionine cycle is disrupted in skeletal muscle during cancer cachexia, leading to endoplasmic reticulum stress and DNA hypomethylation-induced expression of the DNA damage inducible transcript 4 (Ddit4) gene, encoding the regulated in development and DNA damage response 1 (REDD1) protein. Targeting DNA methylation by depletion or pharmacological inhibition of DNA methyltransferase 3A (DNMT3A) exacerbates cachexia, while restoring DNMT3A expression or REDD1 knockout alleviates cancer cachexia-induced skeletal muscle atrophy in mice. Methionine supplementation restores DNA methylation of the Ddit4 promoter in a DNMT3A-dependent manner, thereby inhibiting activating transcription factor 4 (ATF4)-mediated Ddit4 transcription. Thus, with the identification of the methionine/SAM-DNMT3A/DNA hypomethylation-Ddit4/REDD1 axis, our study provides molecular insights into an epigenetic mechanism underlying cancer cachexia, and it suggests nutrient supplementation as a promising therapeutic strategy to prevent or reverse cachectic muscle atrophy.

Methyl donor ameliorates CCl4-induced liver fibrosis by inhibiting inflammation, and fibrosis through the downregulation of EGFR and DNMT-1 expression

Methyl donors regulate the one-carbon metabolism and have significant potential to reduce oxidative stress and inflammation. Therefore, this study aims to investigate the protective effect of methyl donors against CCl4-induced liver fibrosis. Liver fibrosis was induced in male Sprague Dawley rats using CCl4 at a dose of 1 ml/kg (twice a week for a 4-week, via intraperitoneal route). Subsequently, methyl donor treatments were given orally for the next six weeks while continuing CCl4 administration. After 10 weeks, biochemical, histopathology, immunohistochemistry, western blotting, and qRT-PCR were performed. Methyl donor treatment significantly ameliorated ALT, AST, ALP levels, and oxidative stress associated with CCl4-induced liver injury. The histopathological investigation also demonstrated the hepatoprotective effect of methyl donors against CCl4-induced liver fibrosis, showing reduced tissue damage, collagen deposition, and attenuating the expression of the COL1A1 gene. Further, methyl donors inhibited the CCl4-induced increase in DNMT-1 and NF-κB p65 expression with an upregulation of AMPK. Methyl donor downregulated the CCl4-induced increase in inflammatory and fibrosis related gene expression and inhibited the apoptosis with a downregulation of EGFR expression. Here, we provide the first evidence that methyl donor combinations prevent liver fibrosis by attenuating oxidative stress, inflammation, and fibrosis through DNMT-1 and EGFR downregulation.

Exploring the effects of dietary methionine supplementation on European seabass mucosal immune responses against Tenacibaculum maritimum

Introduction

Dietary methionine supplementation has been shown to enhance immunity and disease resistance in fish. However, excessive intake may lead to adverse effects. The present study aimed to evaluate the immune status of European seabass (Dicentrarchus labrax) fed increasing levels of dietary methionine supplementation and to investigate the early immune response to Tenacibaculum maritimum.

Methods

For this purpose, juvenile European seabass were fed one of three experimental diets containing methionine at 8.6 mg/g (CTRL), 18.5 mg/g (MET2), and 29.2 mg/g (MET3) for four weeks, followed by a bath challenge with T. maritimum.

Results

While higher methionine intake reduced hemoglobin levels, no other significant changes in the immune status were observed. However, after infection, fish fed higher methionine levels exhibited a dose-dependent decrease in the mRNA expression of some proinflammatory genes. Similarly, RNA sequencing analysis of skin tissue revealed an attenuated immune response in the MET2 group at 24 hours post-infection, with few proinflammatory genes upregulated, which intensified at 48 h, potentially due to advanced tissue colonization by T. maritimum. The MET3 group displayed the least pronounced immune response, along with the enrichment of some immune-related pathways among the downregulated transcripts. These findings, together with the lower mRNA expression of proinflammatory genes in the head kidney and the higher mortality rates observed in this group, suggest a potential impairment of the immune response.`.

Discussion

Overall, these findings indicate that dietary methionine supplementation may significantly influence both systemic and local immune responses in European seabass, highlighting the need for careful consideration when supplementing diets with methionine.

Methionine-driven methylation modification overcomes plasmid-mediated high-level tigecycline resistance

Tigecycline is a last-resort antibiotic to treat complicated infections caused by multidrug-resistant pathogens, while the emergence of plasmid-mediated tet(X) family severely compromises its clinical efficacy. Novel antimicrobial strategies not limited to new antibiotics in pharmaceutical pipeline are urgently needed. Herein, we reveal the metabolic disparities between tet(X)-negative and -positive E. coli, including distinct energy demand patterns under tigecycline exposure. In particular, the cysteine and methionine metabolism pathway is remarkably downregulated in tet(X)-positive bacteria. More importantly, we find that the addition of exogenous L-methionine (Met) effectively resensitizes tet(X)-positive pathogens to tigecycline. Our mechanistic analysis demonstrates that exogenous Met promotes intracellular tigecycline accumulation by upregulating bacterial proton motive force. Moreover, Met accelerates the conversion to S-adenosyl-L-methionine, an essential methyl donor, thereby enhancing 5mC methylation modification in the promoter region of tet(X4) gene and reducing its expression. Consistently, the potentiation of Met to tigecycline is abolished in tet(X4)-carrying E. coli Δdcm but restored in dcm-complementary bacteria, which encodes DNA-cytosine methyltransferase. In multiple animal models of infection, Met markedly potentiates the effectiveness of tigecycline against pathogenic E. coli and K. pneumoniae. Overall, this work highlights the therapeutic potential of Met in overcoming plasmid-mediated high-level tigecycline resistance, and provides a new paradigm to enhance antibiotic efficacy by harnessing cellular metabolic networks as well as epigenetic modifications.

Exhaled breath metabolites reveal postmenopausal gut-bone cross-talk and non-invasive markers for osteoporosis

BACKGROUND

Menopause driven decline in estrogen exposes women to risk of osteoporosis. Detection of early onset and silent progression are keys to prevent fractures and associated burdens.

METHODS

In a discovery cohort of 120 postmenopausal women, we combined repeated quantitative pulse-echo ultrasonography of bone, assessment of grip strength and serum bone markers with mass-spectrometric analysis of exhaled metabolites to find breath volatile markers and quantitative cutoff levels for osteoporosis. Obtained markers and cutoffs were validated in an independent cohort of 49 age-matched women with six months apart seasonal follow-ups.

RESULTS

Here, within the discovery cohort, concentrations of exhaled end-tidal dimethyl sulfide (DMS), allyl-methyl sulfide, butanethiol and butyric acid are increased (p ≤ 0.005) pronouncedly in subjects with bone mineral density (BMD) at high-risk of osteoporosis and fracture, when compared to subjects with normal BMD. Increased age and decreased grip strength are concomitant. All changes are reproduced during independent validation and seasonal follow-ups. Exhaled metabolite expressions remain age independent. Serum markers show random expressions without reproducibility. DMS exhalations differs between patients with recent, old and without fractures. Metabolite exhalations and BMDs are down-regulated during winter. ROC analysis in discovery cohort yields high classification accuracy of DMS with a cutoff for osteoporosis, which predicts subjects at high-risk within the independent validation cohort with >91% sensitivity and specificity.

CONCLUSIONS

Non-invasive analysis of exhaled DMS allowed more reliable classification of osteoporosis risk than conventional serum markers. We identified associations of exhaled organosulfur and short-chain fatty acids to bone metabolism in postmenopausal osteoporosis via a gut-bone axis.

Dietary methionine supplementation improves cognitive dysfunction associated with transsulfuration pathway upregulation in subacute aging mice

To explore the effects of methionine (Met) supplementation on cognitive dysfunction and the associated mechanisms in aging mice. The mice were administrated 0.15 g/kg/day D-galactose subcutaneously and fed a normal (0.86% Met) or a Met-supplemented diet (1.72% Met) for 11 weeks. Behavioral experiments were conducted, and we measured the plasma metabolite levels, hippocampal and plasma redox and inflammatory states, and hippocampal transsulfuration pathway-related parameters. Met supplementation prevented aging-induced anxiety and cognitive deficiencies, and normalized the plasma levels of multiple systemic metabolites (e.g., betaine, taurine, and choline). Furthermore, dietary Met supplementation abolished oxidative stress and inflammation, selectively modulated the expression of multiple cognition-related genes and proteins, and increased flux via the transsulfuration pathway in the hippocampi of aging mice, with significant increase in H2S and glutathione production. Our findings suggest that dietary Met supplementation prevented cognitive deficiencies in aging mice, probably because of increased flux via the transsulfuration pathway.

Improved metabolic stability in iNOS knockout mice with Lactobacillus supplementation

Oxidative and nitrosative stress play pivotal roles in normal physiological processes and the pathogenesis of metabolic disorders. Previous studies from our lab demonstrated insulin resistance (IR), and dyslipidemia in iNOS-/- mice, emphasizing the importance of maintaining optimal redox balance. These mice exhibited altered gut microbiota with decreased Lactobacillus. Therefore, we hypothesized that Lactobacillus supplementation could mitigate metabolic disturbances in iNOS-/- mice. To test this hypothesis, iNOS-/- mice and wild-type (WT) mice were divided into four groups: iNOS-/- with or without Lactobacillus supplementation, WT with or without Lactobacillus supplementation and glucose tolerance, insulin resistance, gluconeogenesis, lipids, gene expression related to glucose and lipid metabolism (qPCR), fecal gut microbiota (16S rRNA sequencing), and serum and caecum metabolomics (LC-MS) were monitored. IR and dyslipidemic iNOS-/- mice exhibited reduced microbial diversity, diminished presence of Lactobacillus, and altered serum metabolites, indicating metabolic dysregulation. Lactobacillus supplementation in iNOS-/- mice effectively reversed glucose intolerance, IR, dyslipidemia, and associated metabolic irregularities compared to WT. These improvements correlated with changes in gene expression related to fatty acid synthesis in liver and adipose tissue, lipid oxidation in liver, and lipid efflux in intestinal tissue as compared to untreated iNOS-/- mice. Despite the positive effects on metabolic markers, Lactobacillus supplementation did not reduce body weight or rectify disrupted energy balance, as evidenced by reduced VCO2 production, heat generation, and metabolic rates in iNOS-/- mice. The results suggest that Lactobacillus supplementation ameliorates metabolic disturbances but did not fully restore disrupted energy balance, highlighting complex interactions between the gut microbiome and metabolism.

Changes in the growth performance, serum biochemistry, rumen fermentation, rumen microbiota community, and intestinal development in weaned goats during rumen-protected methionine treatment

Rumen-protected methionine (RPM) such as coated methionine (CM) and 2-hydroxy-4-(methylthio)-butanoic acid isopropyl ester (HMBi) was usually used in dairy cows, but how RPM affects meat goats remains unclear. In this study, thirty weaned male Jianzhou Da'er goats were randomly assigned to one of three treatments: fed basal diet or basal diet supplemented with 0.12% CM or 0.22% HMBi, with the aim of examining their impact on growth performance, serum biochemistry, rumen fermentation, rumen microbiota, and intestinal development in meat goats. The findings indicate that HMBi supplementation led to an increase in body weight, feed intake, and feed-to-gain ratio, whereas CM only resulted in an increase in feed intake (all p < 0.05). Both CM and HMBi resulted in an increase in serum total cholesterol (TC), blood urea nitrogen (BUN), alkaline phosphatase (ALP), and aspartate aminotransferase (AST), albeit with a decrease in serum triglycerides (TG) and β-hydroxybutyric acid (BHB, all p < 0.05). Both CM and HMBi supplementation decreased the rumen butyric acid concentration (both p < 0.05). The 16S rRNA sequencing showed that HMBi supplementation significantly increased the total abundance of Bacteroidetes and Firmicutes. Both CM and HMBi supplements increased the abundance of Rikenella and Proteiniphilum but decreased the abundance of Eisenbergiella, Enterocloster, Massilioclostridium, Eubacterium, Angelakisella, Blastopirellula, Christensenella, and Pseudoruminococcus. CM supplementation specifically increased the abundance of Desulfobulbus, Sodaliphilus, and Coprococcus while decreasing the prevalence of Anaerocella, Mogibacterium, and Collinsella. The supplementation of HMBi significantly enhanced the abundance of Paraprevotella, Bacilliculturomica, Lachnoclostridium, Dysosmobacter, Barnesiella, and Paludibacter, while decreasing the abundance of Butyrivibrio and Pirellula. Moreover, the administration of both CM and HMBi supplementation resulted in an increase in the ammonia-producing and sulfate-reducing bacteria, whereas a decrease was observed in the ammonia-oxidating, health-associated, and disease-associated bacteria. Correlational analysis revealed that TG and BHB had a positive correlation with disease-associated and ammonia-oxidating bacteria, whereas they had a negative correlation with ammonia-producing bacteria. The serum BUN, ALP, and AST were positively correlated with ammonia-producing bacteria but were negatively correlated with ammonia-oxidating bacteria. Furthermore, both CM and HMBi supplementation improve the development of the small intestine, with HMBi having a better effect. In summary, this study indicates that both CM and HMBi supplementation improve lipid metabolism, nitrogen utilization, and intestinal development. The growth promotion effect of HMBi supplementation may be attributed to the increased abundance of volatile fatty acid-producing and nitrogen-utilizing bacteria and improved intestinal development.

MAT2A inhibition combats metabolic and transcriptional reprogramming in cancer

Metabolic and transcriptional reprogramming are crucial hallmarks of carcinogenesis that present exploitable vulnerabilities for the development of targeted anticancer therapies. Through controlling the balance of the cellular methionine (MET) metabolite pool, MET adenosyl transferase 2 alpha (MAT2A) regulates crucial steps during metabolism and the epigenetic control of transcription. The aberrant function of MAT2A has been shown to drive malignant transformation through metabolic addiction, transcriptional rewiring, and immune modulation of the tumor microenvironment (TME). Moreover, MAT2A sustains the survival of 5'-methylthioadenosine phosphorylase (MTAP)-deficient tumors, conferring synthetic lethality to cancers with MTAP loss, a genetic alteration that occurs in ∼15% of all cancers. Thus, the pharmacological inhibition of MAT2A is emerging as a desirable therapeutic strategy to combat tumor growth. Here, we review the latest insights into MAT2A biology, focusing on its roles in both metabolic addiction and gene expression modulation in the TME, outline the current landscape of MAT2A inhibitors, and highlight the most recent clinical developments and opportunities for MAT2A inhibition as a novel anti-tumor therapy.

Metabolic Pathways Affected in Patients Undergoing Hemodialysis and Their Relationship with Inflammation

Worldwide, 3.9 million individuals rely on kidney replacement therapy. They experience heightened susceptibility to cardiovascular diseases and mortality, alongside an increased risk of infections and malignancies, with inflammation being key to explaining this intensified risk. This study utilized semi-targeted metabolomics to explore novel metabolic pathways related to inflammation in this population. We collected pre- and post-session blood samples of patients who had already undergone one year of chronic hemodialysis and used liquid chromatography and high-resolution mass spectrometry to perform a metabolomic analysis. Afterwards, we employed both univariate (Mann-Whitney test) and multivariate (logistic regression with LASSO regularization) to identify metabolites associated with inflammation. In the univariate analysis, indole-3-acetaldehyde, 2-ketobutyric acid, and urocanic acid showed statistically significant decreases in median concentrations in the presence of inflammation. In the multivariate analysis, metabolites positively associated with inflammation included allantoin, taurodeoxycholic acid, norepinephrine, pyroglutamic acid, and L-hydroorotic acid. Conversely, metabolites showing negative associations with inflammation included benzoic acid, indole-3-acetaldehyde, methionine, citrulline, alphaketoglutarate, n-acetyl-ornithine, and 3-4-dihydroxibenzeneacetic acid. Non-inflamed patients exhibit preserved autophagy and reduced mitochondrial dysfunction. Understanding inflammation in this group hinges on the metabolism of arginine and the urea cycle. Additionally, the microbiota, particularly uricase-producing bacteria and those metabolizing tryptophan, play critical roles.

Simultaneous determination of total homocysteine, methionine, methylmalonic acid and 2-methylcitric acid in dried blood spots by ultra-performance liquid chromatography-tandem mass spectrometry

Homocysteine, methionine, methylmalonic acid and 2-methylcitric acid are clinically relevant markers in the methionine, propionate, and cobalamin metabolism. This study aimed to develop and validate an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for simultaneously determining total homocysteine, methionine, methylmalonic acid and 2-methylcitric acid in dried blood spots. Three 3.2 mm discs were punched from each calibrator, quality control, and sample dried blood spot into a 96-well U-plate. Each sample was spiked with internal standards and extracted. Then the supernatant was transferred to another 96-well U-plate. After nitrogen drying, the dried residues were reconstituted, centrifuged, and the resulting supernatant was transferred to another 96-well plate for analysis. The method was performed using UPLC-MS/MS within 3 min, validated according to guidance documents, and applied to 72 samples from confirmed patients with methionine, propionate, and cobalamin metabolism disorders. The UPLC-MS/MS method provided satisfactory separation of the four analytes. The R2 values were ≥ 0.9937 for all analytes. The recoveries ranged from 94.17 to 114.29 %, and the coefficients of variation for intraday and interday precision were 0.19 % to 5.23 % and 1.02 % to 6.89 %, respectively. No significant carry-over was detected for the four analytes, and most of confirmed samples exhibited biomarker patterns characteristic of the relevant disorders. A simple and fast UPLC-MS/MS method was successfully developed, validated, and applied to clinical samples for the simultaneous determination of total homocysteine, methionine, methylmalonic acid, and 2-methylcitric acid in dried blood spots.

High methionine intake alters gut microbiota and lipid profile and leads to liver steatosis in mice

Methionine is an important sulfur-containing amino acid. Health effects of both methionine restriction (MR) and methionine supplementation (MS) have been studied. This study aimed to investigate the impact of a high-methionine diet (HMD) (1.64% methionine) on both the gut and liver functions in mice through multi-omic analyses. Hepatic steatosis and compromised gut barrier function were observed in mice fed the HMD. RNA-sequencing (RNA-seq) analysis of liver gene expression patterns revealed the upregulation of lipid synthesis and degradation pathways, cholesterol metabolism and inflammation-related nucleotide-binding oligomerization domain (NOD)-like receptor signaling pathway. Metagenomic sequencing of cecal content demonstrated a shift in gut microbial composition with an increased abundance of opportunistic pathogens and gut microbial functions with up-regulated lipopolysaccharide (LPS) biosynthesis in mice fed HMD. Metabolomic study of cecal content showed an altered gut lipid profile and the level of bioactive lipids, including docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), palmitoylethanolamide (PEA), linoleoyl ethanolamide (LEA) and arachidonoyl ethanolamide (AEA), that carry anti-inflammatory effects significantly reduced in the gut of mice fed the HMD. Correlation analysis demonstrated that gut microbiota was highly associated with liver and gut functions and gut bioactive lipid content. In conclusion, this study suggested that the HMD exerted negative impacts on both the gut and liver, and an adequate amount of methionine intake should be carefully determined to ensure normal physiological function without causing adverse effects.

Novel homozygous ADK out-of-frame deletion causes adenosine kinase deficiency with rare phenotypes of sepsis, metabolites disruption and neutrophil dysfunction

Adenosine kinase deficiency (OMIM #614300) is a type of inborn errors of metabolism with multiorgan symptoms primarily neurological disorders, hepatic impairment, global developmental delay, and mild dysmorphism. The genetic causes of adenosine kinase deficiency are homozygous or compound heterozygous loss-of-function variants of ADK. To date, fewer than 25 cases of adenosine kinase deficiency have been reported worldwide and none have been reported in China. In this research, trio whole-exome sequencing (Trio-WES) identified a novel homozygous ADK (NM_001123.4) out-of-frame deletion, c.518_519delCA (p.Thr173Serfs*15), in a Chinese patient with rare phenotypes of sepsis, metabolites disruption and neutrophil dysfunction. This variant was dysfunctional, with marked reduction of ADK level in both the patient's peripheral blood and cells transfected with the corresponding variant. Additionally, metabolomics detected by high-throughput mass spectrometry showed disturbances in the methionine (Met) and energy pathway. RNA sequencing (RNA-seq) of the patient's peripheral blood suggested a defective anti-inflammatory response characterized by impaired neutrophil activation, migration, and degranulation, which might be the primary cause for the sepsis. To our knowledge, we identified the first Chinese patient of adenosine kinase deficiency with a novel homozygous out-of-frame deletion in ADK causing multiorgan disorders, metabolites disruption, rare phenotypes of sepsis, and neutrophil dysfunction. Our findings broaden the genetic spectrum and pathogenic mechanisms of adenosine kinase deficiency.

Amino acid restriction, aging, and longevity: an update

Various so-called dietary restriction paradigms have shown promise for extending health and life. All such paradigms rely on ad libitum (hereafter ad lib) feeding, something virtually never employed in animals whose long-term health we value, either as a control or, except for food restriction itself, for both control and treatment arms of the experiment. Even though the mechanism(s) remain only vaguely understood, compared to ad lib-fed animals a host of dietary manipulations, including calorie restriction, low protein, methionine, branched-chain amino acids, and even low isoleucine have demonstrable health benefits in laboratory species in a standard laboratory environment. The remaining challenge is to determine whether these health benefits remain in more realistic environments and how they interact with other health enhancing treatments such as exercise or emerging geroprotective drugs. Here we review the current state of the field of amino acid restriction on longevity of animal models and evaluate its translational potential.

Dietary cysteine and methionine promote peroxisome elevation and fat loss by induction of CG33474 expression in Drosophila adipose tissue

The high-protein diet (HPD) has emerged as a potent dietary approach to curb obesity. Peroxisome, a highly malleable organelle, adapts to nutritional changes to maintain homeostasis by remodeling its structure, composition, and quantity. However, the impact of HPD on peroxisomes and the underlying mechanism remains elusive. Using Drosophila melanogaster as a model system, we discovered that HPD specifically increases peroxisome levels within the adipose tissues. This HPD-induced peroxisome elevation is attributed to cysteine and methionine by triggering the expression of CG33474, a fly homolog of mammalian PEX11G. Both the overexpression of Drosophila CG33474 and human PEX11G result in increased peroxisome size. In addition, cysteine and methionine diets both reduce lipid contents, a process that depends on the presence of CG33474. Furthermore, CG33474 stimulates the breakdown of neutral lipids in a cell-autonomous manner. Moreover, the expression of CG33474 triggered by cysteine and methionine requires TOR signaling. Finally, we found that CG33474 promotes inter-organelle contacts between peroxisomes and lipid droplets (LDs), which might be a potential mechanism for CG33474-induced fat loss. In summary, our findings demonstrate that CG33474/PEX11G may serve as an essential molecular bridge linking HPD to peroxisome dynamics and lipid metabolism.

Longitudinal Profiling of Fasting Plasma Metabolome in Response to Weight-Loss Interventions in Patients with Morbid Obesity

It is well recognized that patients with severe obesity exhibit remarkable heterogeneity in response to different types of weight-loss interventions. Those who undergo Roux-en-Y gastric bypass (RYGB) usually exhibit more favorable glycemic outcomes than those who receive adjustable gastric banding (BAND) or intensive medical intervention (IMI). The molecular mechanisms behind these observations, however, remain largely unknown. To identify the plasma metabolites associated with differential glycemic outcomes induced by weight-loss intervention, we studied 75 patients with severe obesity (25 each in RYGB, BAND, or IMI). Using untargeted metabolomics, we repeatedly measured 364 metabolites in plasma samples at baseline and 1-year after intervention. Linear regression was used to examine whether baseline metabolites or changes in metabolites are associated with differential glycemic outcomes in response to different types of weight-loss intervention, adjusting for sex, baseline age, and BMI as well as weight loss. Network analyses were performed to identify differential metabolic pathways involved in the observed associations. After correction for multiple testing (q < 0.05), 33 (RYGB vs. IMI) and 28 (RYGB vs. BAND) baseline metabolites were associated with changes in fasting plasma glucose (FPG) or glycated hemoglobin (HbA1c). Longitudinal changes in 38 (RYGB vs. IMI) and 38 metabolites (RYGB vs. BAND) were significantly associated with changes in FPG or HbA1c. The identified metabolites are enriched in pathways involved in the biosynthesis of aminoacyl-tRNA and branched-chain amino acids. Weight-loss intervention evokes extensive changes in plasma metabolites, and the altered metabolome may underlie the differential glycemic outcomes in response to different types of weight-loss intervention, independent of weight loss itself.

Genetic and molecular understanding for the development of methionine-rich maize: a holistic approach

Maize (Zea mays) is the most important coarse cereal utilized as a major energy source for animal feed and humans. However, maize grains are deficient in methionine, an essential amino acid required for proper growth and development. Synthetic methionine has been used in animal feed, which is costlier and leads to adverse health effects on end-users. Bio-fortification of maize for methionine is, therefore, the most sustainable and environmental friendly approach. The zein proteins are responsible for methionine deposition in the form of δ-zein, which are major seed storage proteins of maize kernel. The present review summarizes various aspects of methionine including its importance and requirement for different subjects, its role in animal growth and performance, regulation of methionine content in maize and its utilization in human food. This review gives insight into improvement strategies including the selection of natural high-methionine mutants, molecular modulation of maize seed storage proteins and target key enzymes for sulphur metabolism and its flux towards the methionine synthesis, expression of synthetic genes, modifying gene codon and promoters employing genetic engineering approaches to enhance its expression. The compiled information on methionine and essential amino acids linked Quantitative Trait Loci in maize and orthologs cereals will give insight into the hotspot-linked genomic regions across the diverse range of maize germplasm through meta-QTL studies. The detailed information about candidate genes will provide the opportunity to target specific regions for gene editing to enhance methionine content in maize. Overall, this review will be helpful for researchers to design appropriate strategies to develop high-methionine maize.

Hyperhomocysteinaemia Promotes Doxorubicin-Induced Cardiotoxicity in Mice

Doxorubicin, a widely used chemotherapeutic drug in clinical oncology, causes a series of cardiac side effects referred to as doxorubicin-induced cardiotoxicity. Hyperhomocysteinaemia is an independent risk factor for multiple cardiovascular diseases. However, whether hyperhomocysteinaemia contributes to doxorubicin-induced cardiotoxicity is currently unknown. In this study, we explored the pathogenic effects of hyperhomocysteinaemia induced by dietary methionine supplementation (2% wt/wt in rodent chow) in a mouse model of doxorubicin-induced cardiotoxicity. Our data showed that methionine supplementation doubled serum homocysteine levels, inducing mild hyperhomocysteinaemia. Doxorubicin at a cumulative dosage of 25 mg/kg body weight led to significant weight loss and severe cardiac dysfunction, which were further exacerbated by methionine-induced mild hyperhomocysteinaemia. Doxorubicin-induced cardiac atrophy, cytoplasmic vacuolisation, myofibrillar disarray and loss, as well as cardiac fibrosis, were also exacerbated by methionine-induced mild hyperhomocysteinaemia. Additional folic acid supplementation (0.006% wt/wt) prevented methionine-induced hyperhomocysteinaemia and inhibited hyperhomocysteinaemia-aggravated cardiac dysfunction and cardiomyopathy. In particular, hyperhomocysteinaemia increased both serum and cardiac oxidative stress, which could all be inhibited by folic acid supplementation. Therefore, we demonstrated for the first time that hyperhomocysteinaemia could exacerbate doxorubicin-induced cardiotoxicity in mice, and the pathogenic effects of hyperhomocysteinaemia might at least partially correlate with increased oxidative stress and could be prevented by folic acid supplementation. Our study provides preliminary experimental evidence for the assessment of hyperhomocysteinaemia as a potential risk factor for chemotherapy-induced cardiotoxicity in cancer patients.

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance.

Association of amino acids and parameters of bone metabolism with endothelial dysfunction and vasculopathic changes in limited systemic sclerosis

Objectives

Pathways contributing to endothelial dysfunction in patients with limited cutaneous systemic sclerosis (lcSSc) are largely unknown. The aim of this study was to investigate potential associations of amino acids and parameters of bone metabolism with endothelial dysfunction and vasculopathy-related changes in patients with lcSSc and early-stage vasculopathy.

Methods

Amino acids, calciotropic parameters, including 25-hydroxyvitamin D and parathyroid hormone (PTH), and bone turnover parameters, including osteocalcin and N-terminal peptide of procollagen-3 (P3NP), were measured in 38 lcSSc patients and 38 controls. Endothelial dysfunction was assessed by biochemical parameters, pulse-wave analysis, flow-mediated and nitroglycerine-mediated dilation. Additionally, vasculopathy-related and SSc-specific clinical changes including capillaroscopic, skin, renal, pulmonary, gastrointestinal and periodontal parameters were recorded.

Results

No significant differences in amino acids, calciotropic and bone turnover parameters were observed between lcSSc patients and controls. In patients with lcSSc, several significant correlations were found between selected amino acids, parameters of endothelial dysfunction, vasculopathy-related and SSc-specific clinical changes (all with p < 0.05). In addition, significant correlations were observed between PTH and 25-hydroxyvitamin D with homoarginine, and between osteocalcin, PTH and P3NP with modified Rodnan skin score and selected periodontal parameters (all with p < 0.05). Vitamin D deficiency defined as 25-hydroxyvitamin D < 20 ng/ml was associated with the presence of puffy finger (p = 0.046) and early pattern (p = 0.040).

Conclusion

Selected amino acids may affect endothelial function and may be associated to vasculopathy-related and clinical changes in lcSSc patients, while the association with parameters of bone metabolism seems to be minor.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Dynamic changes in intestinal microbiota and metabolite composition of pre-weaned beef calves

Gut microbes and their metabolites are essential for maintaining host health and production. The intestinal microflora of pre-weaned calves gradually tends to mature with growth and development and has high plasticity, but few studies have explored the dynamic changes of intestinal microbiota and metabolites in pre-weaned beef calves. In this study, we tracked the dynamics of faecal microbiota in 13 new-born calves by 16S rRNA gene sequencing and analysed changes in faecal amino acid levels using metabolomics. Calves were divided into the relatively high average daily gain group (HA) and the relatively low average daily gain group (LA) for comparison. The results demonstrated that the alpha diversity of the faecal microbiota increased with calf growth and development. The abundance of Porphyromonadaceae bacterium DJF B175 increased in the HA group, while that of Lactobacillus reuteri decreased. The results of the LEfSe analysis showed that the microbiota of faeces of HA calves at eight weeks of age was enriched with P. bacterium DJF B175, while Escherichia coli and L. reuteri were enriched in the microbiota of faeces of LA calves. Besides, the total amino acid concentration decreased significantly in the eighth week compared with that in the first week (P < 0.05). Overall, even under the same management conditions, microorganisms and their metabolites interact to play different dynamic regulatory roles. Our results provide new insights into changes in the gut microbiota and metabolites of pre-weaned calves.

Metabolic Homeostasis of Amino Acids and Diabetic Kidney Disease

Diabetic kidney disease (DKD) occurs in 25-40% of patients with diabetes. Individuals with DKD are at a significant risk of progression to end-stage kidney disease morbidity and mortality. At present, although renal function-decline can be retarded by intensive glucose lowering and strict blood pressure control, these current treatments have shown no beneficial impact on preventing progression to kidney failure. Recently, in addition to control of blood sugar and pressure, a dietary approach has been recommended for management of DKD. Amino acids (AAs) are both biomarkers and causal factors of DKD progression. AA homeostasis contributes to renal hemodynamic response and glomerular hyperfiltration alteration in diabetic patients. This review discusses the links between progressive kidney dysfunction and the metabolic homeostasis of histidine, tryptophan, methionine, glutamine, tyrosine, and branched-chain AAs. In addition, we emphasize the regulation effects of special metabolites on DKD progression, with a focus on causality and potential mechanisms. This paper may offer an optimized protein diet strategy with concomitant management of AA homeostasis to reduce the risks of DKD in a setting of hyperglycemia.

Serum Metabolomic Profiling in Aging Mice Using Liquid Chromatography-Mass Spectrometry

BACKGROUND

The process of aging and metabolism are intricately linked, thus rendering the identification of reliable biomarkers related to metabolism crucial for delaying the aging process. However, research of reliable markers that reflect aging profiles based on machine learning is scarce.

METHODS

Serum samples were obtained from aged mice (18-month-old) and young mice (3-month-old). LC-MS was used to perform a comprehensive analysis of the serum metabolome and machine learning was used to screen potential aging-related biomarkers.

RESULTS

In total, aging mice were characterized by 54 different metabolites when compared to control mice with criteria: VIP ≥ 1, q-value < 0.05, and Fold-Change ≥ 1.2 or ≤0.83. These metabolites were mostly involved in fatty acid biosynthesis, cysteine and methionine metabolism, D-glutamine and D-glutamate metabolism, and the citrate cycle (TCA cycle). We merged the comprehensive analysis and four algorithms (LR, GNB, SVM, and RF) to screen aging-related biomarkers, leading to the recognition of oleic acid. In addition, five metabolites were identified as novel aging-related indicators, including oleic acid, citric acid, D-glutamine, trypophol, and L-methionine.

CONCLUSIONS

Changes in the metabolism of fatty acids and conjugates, organic acids, and amino acids were identified as metabolic dysregulation related to aging. This study revealed the metabolic profile of aging and provided insights into novel potential therapeutic targets for delaying the effects of aging.

Spotlight on liver macrophages for halting liver disease progression and injury

INTRODUCTION

Over the past two decades, understanding of hepatic macrophage biology has provided astounding details of their role in the progression and regression of liver diseases. The hepatic macrophages constitute resident macrophages, Kupffer cells, and circulating bone marrow monocyte-derived macrophages, which play a diverse role in liver injury and repair. Imbalance in the macrophage population leads to pathological consequences and is responsible for the initiation and progression of acute and chronic liver injuries. Further, distinct populations of hepatic macrophages and their high heterogeneity make their complex role enigmatic. The unique features of distinct phenotypes of macrophages have provided novel biomarkers for defining the stages of liver diseases. The distinct mechanisms of hepatic macrophages polarization and recruitment have been at the fore front of research. In addition, the secretome of hepatic macrophages and their immune regulation has provided clinically relevant therapeutic targets.

AREAS COVERED

Herein we have highlighted the current understanding in the area of hepatic macrophages, and their role in the progression of liver injury.

EXPERT OPINION

It is essential to ascertain the physiological and pathological role of evolutionarily conserved distinct macrophage phenotypes in different liver diseases before viable approaches may see a clinical translation.

L-Methionine supplementation attenuates high-fat fructose diet-induced non-alcoholic steatohepatitis by modulating lipid metabolism, fibrosis, and inflammation in rats

Recently, the protective effects of a methionine-rich diet on hepatic oxidative stress and fibrosis have been suggested but not adequately studied. We, therefore, hypothesized that L-methionine supplementation would ameliorate the progression of hepatic injury in a diet-induced non-alcoholic steatohepatitis (NASH) model and aimed to investigate the underlying mechanism. NASH was developed in male Sprague Dawley rats by feeding them with a high-fat-fructose diet (HFFrD) for 10 weeks. The results demonstrated that L-methionine supplementation to NASH rats for 16 weeks improved the glycemic, lipid, and liver function profiles in NASH rats. Histological analysis of liver tissue revealed a remarkable improvement in the three classical lesions of NASH: steatosis, inflammation, and ballooning. Besides, L-methionine supplementation ameliorated the HFFrD-induced enhanced lipogenesis and lipid peroxidation. An anti-inflammatory effect of L-methionine was also observed through the inhibition of the release of proinflammatory cytokines. Furthermore, the hepatic SIRT1/AMPK signaling pathway was associated with the beneficial effects of L-methionine. This study demonstrates that L-methionine supplementation in HFFrD-fed rats improves their liver pathology via regulation of lipogenesis, inflammation, and the SIRT1/AMPK pathway, thus encouraging its clinical evaluation for the treatment of NASH.

Apoptosis and Pharmacological Therapies for Targeting Thereof for Cancer Therapeutics

Apoptosis is an evolutionarily conserved sequential process of cell death to maintain a homeostatic balance between cell formation and cell death. It is a vital process for normal eukaryotic development as it contributes to the renewal of cells and tissues. Further, it plays a crucial role in the elimination of unnecessary cells through phagocytosis and prevents undesirable immune responses. Apoptosis is regulated by a complex signaling mechanism, which is driven by interactions among several protein families such as caspases, inhibitors of apoptosis proteins, B-cell lymphoma 2 (BCL-2) family proteins, and several other proteases such as perforins and granzyme. The signaling pathway consists of both pro-apoptotic and pro-survival members, which stabilize the selection of cellular survival or death. However, any aberration in this pathway can lead to abnormal cell proliferation, ultimately leading to the development of cancer, autoimmune disorders, etc. This review aims to elaborate on apoptotic signaling pathways and mechanisms, interacting members involved in signaling, and how apoptosis is associated with carcinogenesis, along with insights into targeting apoptosis for disease resolution.

Ameliorative effect of cerium oxide nanoparticles against Freund's complete adjuvant-induced arthritis

Aim: To assess the mechanistic effects of cerium oxide nanoparticles (CONPs) on Freund's complete adjuvant (FCA)-induced rheumatoid arthritis in rats. Methods: CONPs were characterized and evaluated in vitro (RAW 264.7 macrophages) and in vivo (FCA-induced rheumatoid arthritis model). Results:In vitro treatment with CONPs significantly reduced lipopolysaccharide-induced oxidative stress (as evident from dichlorodihydrofluorescein diacetate staining), diminished mitochondrial stress (as observed with tetraethylbenzimidazolylcarbocyanine iodide staining) and reduced superoxide radicals. In vivo, CONPs exhibited anti-rheumatoid arthritis activity, as evident from results of paw volume, x-ray, clinical scoring, levels of cytokines (IL-17, IL-1β, TNF-α and TGF-β1) and histology. Conclusion: We provide preclinical proof that CONPs may be a novel futuristic nanoparticle-based approach for therapy of rheumatoid arthritis.

Gene therapy: Comprehensive overview and therapeutic applications

Gene therapy is the product of man's quest to eliminate diseases. Gene therapy has three facets namely, gene silencing using siRNA, shRNA and miRNA, gene replacement where the desired gene in the form of plasmids and viral vectors, are directly administered and finally gene editing based therapy where mutations are modified using specific nucleases such as zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered regulatory interspaced short tandem repeats (CRISPR)/CRISPR-associated protein (Cas)-associated nucleases. Transfer of gene is either through transformation where under specific conditions the gene is directly taken up by the bacterial cells, transduction where a bacteriophage is used to transfer the genetic material and lastly transfection that involves forceful delivery of gene using either viral or non-viral vectors. The non-viral transfection methods are subdivided into physical, chemical and biological. The physical methods include electroporation, biolistic, microinjection, laser, elevated temperature, ultrasound and hydrodynamic gene transfer. The chemical methods utilize calcium- phosphate, DAE-dextran, liposomes and nanoparticles for transfection. The biological methods are increasingly using viruses for gene transfer, these viruses could either integrate within the genome of the host cell conferring a stable gene expression, whereas few other non-integrating viruses are episomal and their expression is diluted proportional to the cell division. So far, gene therapy has been wielded in a plethora of diseases. However, coherent and innocuous delivery of genes is among the major hurdles in the use of this promising therapy. Hence this review aims to highlight the current options available for gene transfer along with the advantages and limitations of every method.

L-Methionine prevents β-cell damage by modulating the expression of Arx, MafA and regulation of FOXO1 in type 1 diabetic rats

L-Methionine (L-Met) is an essential sulphur-containing amino acid having a vital role in various key cellular processes. Here we investigated the effect of L-Met on streptozotocin-induced β-cell damage model of diabetes mellitus in Sprague Dawley rats. At the end of study biochemical parameters, immunoblotting, qRT-PCR and ChIP-qPCR are performed. L-Met was administered orally (250 and 500 mg/kg/day) to diabetic animals for 8 weeks improved plasma glucose and insulin levels. Pancreas immunohistochemistry showed significant increase in insulin expression, decrease in glucagon and Bax expression. Interestingly, L-Met inhibited the expression of Arx; upregulated MafA and FOXO1 which play a critical role in the maintenance of β-cell identity. Our data also showed a decrease in H3K27me3 and an increase in H3K4me3 ("bivalent domain" alteration) in diabetic rats and these recovered by L-Met. Furthermore, the chromatin-immunoprecipitation assay showed a decreased enrichment of H3K27me3 on the promoter of the FOXO1 gene in diabetic rats and L-Met prevents this decrease. Our results showed the first evidence of the involvement of H3K27me3 in regulating the expression of the FOXO1 gene and the prevention of β-cell injury by L-Met treatment. In conclusion, we report the involvement of L-Met in the modulation of α-cell identity marker (Arx), β-cell identity marker (MafA) and regulation of FOXO1 by histone methylation marks for the first time. We are of the opinion that this employed as a novel therapeutic approach for mitigating diabetes-induced β-cell death.