Methionine restriction on lipid metabolism and its possible mechanisms

Lipid droplets and fatty acid-induced lipotoxicity: in a nutshell

Lipid droplets (LDs) are fat storage organelles that are conserved from bacteria to humans. LDs are broken down to supply cells with fatty acids (FAs) that can be used as an energy source or membrane synthesis. An overload of FAs disrupts cellular functions and causes lipotoxicity. Thus, by acting as hubs for storing excess fat, LDs prevent lipotoxicity and preserve cellular homeostasis. LD synthesis and turnover have to be precisely regulated to maintain a balanced lipid distribution and allow for cellular adaptation during stress. Here, we discuss how prolonged exposure to excess lipids affects cellular functions, and the roles of LDs in buffering cellular stress focusing on lipotoxicity.

Metabolomics revealed more deleterious toxicity induced by the combined exposure of ammonia and nitrite on Ruditapes philippinarum compared to single exposure

NH3-N and NO2-N always co-exist in the aquatic environment, but there is not a clear opinion on their joint toxicities to the molluscs. Presently, clams Ruditapes philippinarum were challenged by environmental concentrations of NH3-N and NO2-N, singly or in combination, and analyzed by metabolomics approaches, enzyme assays and transmission electron microscope (TEM) observation. Results showed that some same KEGG pathways with different enriched-metabolites were detected in the three exposed groups within one day, and completely different profiles of metabolites were found in the rest of the exposure period. The combined exposure induced heavier and more lasting toxicities to the clams compared with their single exposure. ACP activity and the number of secondary lysosomes were significantly increased after the combined exposure. The present study shed light on the joint-toxicity mechanism of NH3-N and NO2-N, and provided fundamental data for the toxicity research on inorganic nitrogen.

Rumen-protected methionine supplementation alters lipid profile of preimplantation embryo and endometrial tissue of Holstein cows

Our objective is to evaluate the effects of feeding rumen-protected Met (RPM) throughout the transition period and early lactation on the lipid profile of the preimplantation embryos and the endometrial tissue of Holstein cows. Treatments consisted of feeding a total mixed ration with top-dressed RPM (Smartamine® M, Adisseo, Alpharetta, GA, United States; MET; n = 11; RPM at a rate of 0.08% of DM: Lys:Met = 2.8:1) or not (CON; n = 9, Lys:Met = 3.5:1). Endometrial biopsies were performed at 15, 30, and 73 days in milk (DIM). Prior to the endometrial biopsy at 73 DIM, preimplantation embryos were harvested via flushing. Endometrial lipid profiles were analyzed using multiple reaction monitoring-profiling and lipid profiles of embryos were acquired using matrix assisted laser desorption/ionization mass spectrometry. Relative intensities levels were used for principal component analysis. Embryos from cows in MET had greater concentration of polyunsaturated lipids than embryos from cows in CON. The endometrial tissue samples from cows in MET had lesser concentrations of unsaturated and monounsaturated lipids at 15 DIM, and greater concentration of saturated, unsaturated (specifically diacylglycerol), and monounsaturated (primarily ceramides) lipids at 30 DIM than the endometrial tissue samples from cows in CON. In conclusion, feeding RPM during the transition period and early lactation altered specific lipid classes and lipid unsaturation level of preimplantation embryos and endometrial tissue.

Enhancing bovine immune, antioxidant and anti-inflammatory responses with vitamins, rumen-protected amino acids, and trace minerals to prevent periparturient mastitis

Mastitis, the inflammatory condition of mammary glands, has been closely associated with immune suppression and imbalances between antioxidants and free radicals in cattle. During the periparturient period, dairy cows experience negative energy balance (NEB) due to metabolic stress, leading to elevated oxidative stress and compromised immunity. The resulting abnormal regulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with increased non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) are the key factors associated with suppressed immunity thereby increases susceptibility of dairy cattle to infections, including mastitis. Metabolic diseases such as ketosis and hypocalcemia indirectly contribute to mastitis vulnerability, exacerbated by compromised immune function and exposure to physical injuries. Oxidative stress, arising from disrupted balance between ROS generation and antioxidant availability during pregnancy and calving, further contributes to mastitis susceptibility. Metabolic stress, marked by excessive lipid mobilization, exacerbates immune depression and oxidative stress. These factors collectively compromise animal health, productive efficiency, and udder health during periparturient phases. Numerous studies have investigated nutrition-based strategies to counter these challenges. Specifically, amino acids, trace minerals, and vitamins have emerged as crucial contributors to udder health. This review comprehensively examines their roles in promoting udder health during the periparturient phase. Trace minerals like copper, selenium, and calcium, as well as vitamins; have demonstrated significant impacts on immune regulation and antioxidant defense. Vitamin B12 and vitamin E have shown promise in improving metabolic function and reducing oxidative stress followed by enhanced immunity. Additionally, amino acids play a pivotal role in maintaining cellular oxidative balance through their involvement in vital biosynthesis pathways. In conclusion, addressing periparturient mastitis requires a holistic understanding of the interplay between metabolic stress, immune regulation, and oxidative balance. The supplementation of essential amino acids, trace minerals, and vitamins emerges as a promising avenue to enhance udder health and overall productivity during this critical phase. This comprehensive review underscores the potential of nutritional interventions in mitigating periparturient bovine mastitis and lays the foundation for future research in this domain.

Old-age-induced obesity reversed by a methionine-deficient diet or oral administration of recombinant methioninase-producing Escherichia coli in C57BL/6 mice

Obesity increases with aging. Methionine restriction affects lipid metabolism and can prevent obesity in mice. In the present study we observed C57BL/6 mice to double their body weight from 4 to 48 weeks of age and become obese. We evaluated the efficacy of oral administration of recombinant-methioninase (rMETase)-producing E. coli (E. coli JM109-rMETase) or a methionine-deficient diet to reverse old-age-induced obesity in C57BL/6 mice. Fifteen C57BL/6 male mice aged 12-18 months with old-age-induced obesity were divided into three groups. Group 1 was given a normal diet supplemented with non-recombinant E. coli JM109 cells orally by gavage twice daily; Group 2 was given a normal diet supplemented with recombinant E. coli JM109-rMETase cells by gavage twice daily; and Group 3 was given a methionine-deficient diet without treatment. The administration of E. coli JM109-rMETase or a methionine-deficient diet reduced the blood methionine level and reversed old-age-induced obesity with significant weight loss by 14 days. There was a negative correlation between methionine levels and negative body weight change. Although the degree of efficacy was higher in the methionine-deficient diet group than in the E. coli JM109-rMETase group, the present findings suggested that oral administration of E. coli JM109-rMETase, as well as a methionine-deficient diet, are effective in reversing old-age-induced obesity. In conclusion, the present study provides evidence that restricting methionine by either a low-methionine diet or E. coli JM109-rMETase has clinical potential to treat old-age-induced obesity.

Associated long-term effects of decabromodiphenyl ethane on the gut microbial profiles and metabolic homeostasis in Sprague-Dawley rat offspring

Decabromodiphenyl ethane (DBDPE) as a widely used brominated flame retardant is harmful to human health due to its toxicity, including cardiovascular toxicity, reproductive toxicity, and hepatotoxicity. However, the knowledge of the long-term effects and structural and metabolic function influence on gut microbiota from DBDPE exposure remains limited. This study was mainly aimed at the gut microbiome and fecal metabolome of female rats and their offspring exposed to DBDPE in early life. 16S rRNA gene sequencing demonstrated that maternal DBDPE exposure could increase the α-diversity of gut microbiota in immature offspring while decreasing the abundance of Bifidobacterium, Clostridium, Muribaculum, Escherichia, and Lactobacillus in adult offspring. The nonmetric multidimensional scaling showed a consistency in the alternation of β-diversity between pregnant rats and their adult offspring. Furthermore, the short-chain fatty acids produced by gut microbiota dramatically increased in adult offspring after maternal DBDPE exposure, revealing that DBDPE treatment disrupted the gut microbial compositions and altered the gut community's metabolic functions. Untargeted metabolomics identified 41 differential metabolites and seven metabolic pathways between adult offspring from various groups. Targeted metabolomic showed that maternal high dose DBDPE exposure obviously decreased the level of glutathione, taurine, and l-carnitine in their adult offspring, which verified the correlation between weight loss and amino acid metabolites. An interesting link between some gut bacteria (especially the Firmicutes) and fecal metabolites demonstrated the shifts in gut microbiota may drive the metabolic process of fecal metabolites. The current findings provide new insight into long-term effects on human health.

Overview of the effect of rumen-protected limiting amino acids (methionine and lysine) and choline on the immunity, antioxidative, and inflammatory status of periparturient ruminants

Overproduction of reactive oxygen species (ROS) is a well-known phenomenon experienced by ruminants, especially during the transition from late gestation to successful lactation. This overproduction of ROS may lead to oxidative stress (OS), which compromises the immune and anti-inflammatory systems of animals, thus predisposing them to health issues. Besides, during the periparturient period, metabolic stress is developed due to a negative energy balance, which is followed by excessive fat mobilization and poor production performance. Excessive lipolysis causes immune suppression, abnormal regulation of inflammation, and enhanced oxidative stress. Indeed, OS plays a key role in regulating the metabolic activity of various organs and the productivity of farm animals. For example, rapid fetal growth and the production of large amounts of colostrum and milk, as well as an increase in both maternal and fetal metabolism, result in increased ROS production and an increased need for micronutrients, including antioxidants, during the last trimester of pregnancy and at the start of lactation. Oxidative stress is generally neutralized by the natural antioxidant system in the body. However, in some special phases, such as the periparturient period, the animal's natural antioxidant system is unable to cope with the situation. The effect of rumen-protected limiting amino acids and choline on the regulation of immunity, antioxidative, and anti-inflammatory status and milk production performance, has been widely studied in ruminants. Thus, in the current review, we gathered and interpreted the data on this topic, especially during the perinatal and lactational stages.

Effects of essential oil extracted from Artemisia argyi leaf on lipid metabolism and gut microbiota in high-fat diet-fed mice

Artemisia argyi leaf is a well-known species in traditional Chinese medicine, and its essential oil (AAEO) has been identified to exert various physiological activities. The aim of this study was to investigate the effects of AAEO on lipid metabolism and the potential microbial role in high-fat diet (HFD)-fed mice. A total of 50 male mice were assigned to five groups for feeding with a control diet (Con), a high-fat diet (HFD), and the HFD plus the low (LEO), medium (MEO), and high (HEO) doses of AAEO. The results demonstrated that dietary HFD markedly increased the body weight gain compared with the control mice (p < 0.05), while mice in the HEO group showed a lower body weight compared to the HFD group (p < 0.05). The weight of fatty tissues and serum lipid indexes (TBA, HDL, and LDL levels) were increased in response to dietary HFD, while there was no significant difference in AAEO-treated mice (p < 0.05). The jejunal villus height was dramatically decreased in HFD-fed mice compared with the control mice, while HEO resulted in a dramatically higher villus height than that in the HFD group (p < 0.05). Microbial α-diversity was not changed in this study, but β-diversity indicated that microbial compositions differed in control, HFD, and EO subjects. At the genus level, the relative abundance of Bacteroides was greater (p < 0.05) in the feces of the Con group when compared to the HFD and EO groups. On the contrary, the abundance of Muribaculum was lower in the Con group compared to the HFD and EO groups (p < 0.05). Although the Muribaculum in the EO group was lower than that in the HFD group, there was no statistically notable difference between the HFD and EO groups (p > 0.05). Simultaneously, the relative abundance of Alistipes (p < 0.05) and Rikenella (p < 0.05) was also dramatically higher in the Con group than in the HFD and EO groups. The abundance of norank_f__norank_o__Clostridia_UCG-014 was lower in the HFD or EO group than in the Con group (p < 0.05). In conclusion, the results suggested that HEO could affect body weight and lipid metabolism without gut microbes in ICR mice, and it was beneficial for the structure of the jejunal epithelial tissue.

Screening, characterization and anti-cancer application of purified intracellular MGL

L-methionine-γ-lyase (MGL) producing bacterial isolates were screened from soil samples that further characterized as 'Klebsiella oxytoca BLM-1' by biochemical and 16S rDNA sequencing. Intracellular MGL obtained from K. oxytoca BLM-1 by sonication was purified by Octyl-Sepharose and Sephadex G-200 column chromatography. MALDI-TOF-MS analysis of protein band (Mr ~ 63 kDa) confirmed the PLP-dependence and structural similarity with MGL enzyme. Purified MGL (1.1 μg) exhibited the maximum activity in potassium phosphate buffer (80 mM; with L-met 20 mM pH 7.0) at 37 °C. That further enhanced in the presence of NaCl (2 mM), Tween-80 (1.0 %; v/v) and EDTA (5 mM). K_m and V_max for purified MGL by using L-met as substrate was found to be 5.32 mM and 0.386 U/mL/min. The purified MGL showed PLP dependence and the half-life was 365.59 min. The MGL was effective against breast cancer (MCF7), gastric adenocarcinoma and human glioblastoma (U87MG) cancer cell lines with IC₅₀ values of purified MGL 0.041 U/mL, 0.008 U/mL and 0.009 U/mL, respectively. The U87MG, greatly affected by MGL treatment, when cultured in DMEM medium (10 mL) with PLP, homocysteine and 10 % FCS as compared to control/untransformed mouse spleen cells.

Branched-Chain and Aromatic Amino Acids Related to Visceral Adipose Tissue Impact Metabolic Health Risk Markers

CONTEXT

Visceral (VAT) and subcutaneous adipose tissue (SAT) function as endocrine organs capable of influencing metabolic health across adiposity levels.

OBJECTIVE

We aimed to investigate whether metabolites associated with VAT and SAT impact metabolic health through metabolite concentrations.

METHODS

Analyses are based on 1790 participants from the population-based Rhineland Study. We assessed plasma levels of methionine (Met), branched-chain amino acids (BCAA), aromatic amino acids (AAA), and their metabolic downstream metabolites with liquid chromatography-mass spectrometry. VAT and SAT volumes were assessed by magnetic resonance imaging (MRI). Metabolically healthy and unhealthy phenotypes were defined using Wildman criteria.

RESULTS

Metabolically unhealthy participants had higher concentrations of BCAA than metabolically healthy participants (P < 0.001). In metabolically unhealthy participants, VAT volumes were significantly associated with levels of L-isoleucine, L-leucine, indole-3-lactic acid, and indole-3-propionic acid (in log SD units: β = 0.16, P = 0.003; β = 0.12, P = 0.038; β = 0.11, P = 0.035 and β = -0.16, P = 0.010, respectively). Higher concentrations of certain BCAA and AAA-downstream metabolites significantly increased the odds of cardiometabolic risk markers. The relation between VAT volume and cardiometabolic risk markers was mediated by BCAA (indirect effects 3.7%-11%, P = 0.02 to < 0.0001), while the effect of VAT on systemic inflammation was mediated through higher kynurenine concentrations (indirect effect 6.4%, P < 0.0001).

CONCLUSION

Larger volumes of VAT in metabolically unhealthy individuals are associated with altered concentrations of circulating BCAA and AAA-downstream metabolites, increasing the odds of cardiometabolic risk markers. This suggests that these metabolites are involved in the mechanisms that underlie the relationship of abdominal VAT with metabolic health.

Dietary methionine deficiency stunts growth and increases fat deposition via suppression of fatty acids transportation and hepatic catabolism in Pekin ducks

Background

Although methionine (Met), the first-limiting dietary amino acid, has crucial roles in growth and regulation of lipid metabolism in ducks, mechanisms underlying are not well understood. Therefore, the objective was to use dietary Met deficiency to investigate the involvement of Met in lipid metabolism and fat accumulation of Pekin ducks.

Methods

A total of 150 male Pekin ducks (15-d-old, 558.5 ± 4.4 g) were allocated into 5 groups (6 replicates with 5 birds each) and fed corn and soybean meal-based diets containing 0.28%, 0.35%, 0.43%, 0.50%, and 0.58% Met, respectively, for 4 weeks. Met-deficient (Met-D, 0.28% Met) and Met-adequate (Met-A, 0.43% Met) groups were selected for subsequent molecular studies. Serum, liver, and abdominal fat samples were collected to assess the genes and proteins involved in lipid metabolism of Pekin ducks and hepatocytes were cultured in vivo for verification.

Results

Dietary Met deficiency caused growth depression and excess fat deposition that were ameliorated by feeding diets with adequate Met. Serum triglyceride and non-esterified fatty acid concentrations increased (P < 0.05), whereas serum concentrations of total cholesterol, low density lipoprotein cholesterol, total protein, and albumin decreased (P < 0.05) in Met-D ducks compared to those in Met-A ducks. Based on hepatic proteomics analyses, dietary Met deficiency suppressed expression of key proteins related to fatty acid transport, fatty acid oxidation, tricarboxylic acid cycle, glycolysis/gluconeogenesis, ketogenesis, and electron transport chain; selected key proteins had similar expression patterns verified by qRT-PCR and Western blotting, which indicated these processes were likely impaired. In vitro verification with hepatocyte models confirmed albumin expression was diminished by Met deficiency. Additionally, in abdominal fat, dietary Met deficiency increased adipocyte diameter and area (P < 0.05), and down-regulated (P < 0.05) of lipolytic genes and proteins, suggesting Met deficiency may suppress lipolysis in adipocyte.

Conclusion

Taken together, these data demonstrated that dietary Met deficiency in Pekin ducks resulted in stunted growth and excess fat deposition, which may be related to suppression of fatty acids transportation and hepatic catabolism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00709-z.

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.

Small Intestine Microbiome and Metabolome of High and Low Residual Feed Intake Angus Heifers

The gastrointestinal tract (GIT) contains complex microbial communities and plays an essential role in the overall health of the host. Previous studies of beef cattle feed efficiency have primarily concentrated on the ruminal microbiota because it plays a key role in energy production and nutrient supply in the host. Although the small intestine is the important site of post-ruminal digestion and absorption of nutrients, only a few studies have explored the relationship between the microbial populations in the small intestine and feed efficiency. Moreover, variations in GIT metabolites contribute to differences in feed efficiency. The objective of this study was to investigate relationships among bacterial populations of duodenum, jejunum, ileum; microbial metabolites; and RFI phenotype of beef cattle. We carried out by using Illumina MiSeq sequencing of the 16S rRNA V3-V4 region and liquid chromatography-mass spectrometry (LC–MS). In the duodenum, the relative abundances of Firmicutes ( p < 0.01), Lachnospiraceae, Ruminococcaceae, Family_XIII, Christensenellaceae, Christensenellaceae_R-7_group ( p < 0.05), and Lachnospiraceae_NK3A20_group ( p < 0.05) were higher in the low residual feed intake (LRFI) group compared with the high residual feed intake (HRFI) group, whereas the HRFI group had higher abundances of Proteobacteria and Acinetobacter ( p < 0.01). In the jejunum, the relative abundances of Lachnospiraceae and Lachnospiraceae_NK3A20_group were higher in the LRFI group ( p < 0.05). In the ileum, the relative abundances of Ruminococcaceae ( p < 0.01), Christensenellaceae, Christensenellaceae_R-7_group, and Ruminococcus_2 were also higher in the LRFI group ( p < 0.05). Moreover, the genera Lachnospiraceae_NK3A20_group, Christensenellaceae_R-7_group, and Ruminococcus_2 were negatively associated with RFI, while the genus Acinetobacter was positively associated with RFI. The metabolomics analysis revealed that the LRFI group significantly improved protein digestion and absorption, as well as glycerophospholipid metabolism in the duodenum, jejunum, ileum. The correlation between intestinal microorganisms and metabolites revealed that some microorganisms play an important role in amino acid metabolism, glycerophospholipid metabolism, nutrient digestion and absorption, and antioxidant enhancement. The present study provides a better understanding of the small intestinal microbiota and metabolites of beef cattle with different RFI phenotypes and the relationships among them, which are potentially important for the improvement of beef cattle feed efficiency.

Impacts of essential amino acids on energy balance

Background

Obesity develops due to an imbalance in energy homeostasis, wherein energy intake exceeds energy expenditure. Accumulating evidence shows that manipulations of dietary protein and their component amino acids affect the energy balance, resulting in changes in fat mass and body weight. Amino acids are not only the building blocks of proteins but also serve as signals regulating multiple biological pathways.

Scope of review

We present the currently available evidence regarding the effects of dietary alterations of a single essential amino acid (EAA) on energy balance and relevant signaling mechanisms at both central and peripheral levels. We summarize the association between EAAs and obesity in humans and the clinical use of modifying the dietary EAA composition for therapeutic intervention in obesity. Finally, similar mechanisms underlying diets varying in protein levels and diets altered of a single EAA are described. The current review would expand our understanding of the contribution of protein and amino acids to energy balance control, thus helping discover novel therapeutic approaches for obesity and related diseases.

Major Conclusions

Changes in circulating EAA levels, particularly increased branched-chain amino acids (BCAAs), have been reported in obese human and animal models. Alterations in dietary EAA intake result in improvements in fat and weight loss in rodents, and each has its distinct mechanism. For example, leucine deprivation increases energy expenditure, reduces food intake and fat mass, primarily through regulation of the general control nonderepressible 2 (GCN2) and mammalian target of rapamycin (mTOR) signaling. Methionine restriction by 80% decreases fat mass and body weight while developing hyperphagia, primarily through fibroblast growth factor 21 (FGF-21) signaling. Some effects of diets with different protein levels on energy homeostasis are mediated by similar mechanisms. However, reports on the effects and underlying mechanisms of dietary EAA imbalances on human body weight are few, and more investigations are needed in future.

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Dietary Essential Amino Acids (EAA) alterations affect energy homeostasis via distinct mechanisms.

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Alterations in dietary EAA intake can reduce fat mass and body weight.

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Increased circulating BCAAs have been observed in obese human and animal models.

The optimum dietary methionine requirement of juvenile humpback grouper (Cromileptes altivelis): effects on growth, micromorphology, protein and lipid metabolism

An 8-week feeding trial was conducted to evaluate optimum dietary methionine (Met) requirement of juvenile humpback grouper (Cromileptes altivelis) and the influence of dietary methionine (Met) supplementations on growth, gut micromorphology, protein and lipid metabolism. Seven isoproteic (48.91%) and isolipidic diets (10%) were made to contain 0.70, 0.88, 1.04, 1.27 1.46, 1.61 and 1.76% of dry matter Met levels. Results showed that lower survival, weight gain (WG%), protein efficiency ratio (PER), protein productive value (PPV) but higher daily feed intake (DFI) and feed conversion ratio (FCR) were observed in the Met deficient groups (0.70 and 0.88%). Optimum dietary Met requirement for humpback grouper was found to be 1.07% through the straight-broken line analysis of WG% against Met. Fish fed Met deficient diets (0.70, 0.88%) exhibited lower mRNA levels of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor-I (IGF-1), target of rapamycin (TOR) as well as S6 kinase 1 (S6K1) than other dietary groups. Whereas, expression of genes related to general control nonderepressible (GCN2) kinase i.e., GCN2 and C/EBPβ enhancer-binding protein β was upregulated in fish fed low Met diets (P < 0.05). The mRNA expression of hepatic fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP-1) were higher in fish fed 0.70 and 0.88% dietary Met group and the lipolytic genes, hepatic peroxisome proliferator-activated receptor α (PPARα) and carnitine palmitoyl transferase-1 (CPT-1) showed an opposite variation tendency as FAS or SREBP1. Generally, the optimum Met requirement for humpback grouper was predicted to be 1.07% of dry matter.

Alterations and Correlations of the Gut Microbiome, Performance, Egg Quality, and Serum Biochemical Indexes in Laying Hens with Low-Protein Amino Acid-Deficient Diets

The present study was carried out to investigate the effects of methionine (Met), lysine (Lys), isoleucine (Ile), and threonine (Thr) deficiency in a low-protein diet on laying performance, egg quality, serum biochemical indices, and the gut microbiota in laying hens. A total of 300 Peking Pink laying hens, at 38 weeks of age, were randomly allocated to five dietary treatments, each of which included six replicates of ten hens. Hens were fed an amino acid-balanced diet (Met: 0.46%; Lys: 0.76%; Ile: 0.72%; Thr: 0.56%; positive control, PC), Met deficiency diet (Met-, 0.25%), Lys deficiency diet (Lys-, 0.56%), Ile deficiency diet (Ile-, 0.54%), and Thr deficiency diet (Thr-, 0.46%) for 12 weeks. Hens were housed in pairs in 45 × 45 × 45 cm wire cages with three ladders and three birds per cage. Feed and water were provided ad libitum during the entire experimental period. All data were analyzed using one-way ANOVA with Turkey's multiple range test. Here, compared to the PC group, final body weight (FBW), average daily gain (ADG), egg production (EP), egg weight (EW), average daily egg mass (EM), average daily feed intake (ADFI), and yield of abdominal fat (AFY) in the Met-group were lower, while EW and EM were higher in the Lys-group. The feed egg ratio (FER) was increased in the Met- and Lys-groups, and EW and AFY were decreased in the Ile-group compared to the controls. Meanwhile, ADG, EP, EM, and ADFI were lower in the Thr group than the PC group. The level of triglycerides (TGs) in the four groups was lower and the concentrations of uric acid (UA) in the Met-group were higher than those in the PC group. The shell color in the Thr group was lower than the PC group. Of note, amino acid deficiency altered the gut microbial structure (e.g., increasing the level of Parabacteroides and decreasing the abundance of Lactobacillus) in hens. The correlation analysis showed that amino acid deficiency-induced gut microbiota alteration is closely associated with the change in key parameters: FER, UA, AFY, EW, EM, TG, FBW, EP, and ADFI. Collectively, our results highlight the role of adequate amino acid ratio supplementation in the low-crude-protein diet structure for laying hens.

Sire-feed interactions for fattening performance and meat quality traits in growing-finishing pigs under a conventional and an organic feeding regimen

In a two-factorial feeding trial 120 growing-finishing pigs from eleven sires were fed on an organic (ORG) or a conventional (CON) diet. Diet ORG contained mainly oil press cakes and legume grains as protein source containing higher protein and crude fiber content along with slight deficiencies of limiting amino acids. Pigs were allocated to treatments balanced according to litter, sex and initial weight. Feed was offered ad libitum. Feed consumption, weight gain as well as carcass, meat and fat quality traits were recorded. ORG fed animals had lower weight gain, poorer feed conversion, lower loin muscle area, higher intramuscular fat content, higher ultimate pH (loin, ham), and a higher PUFA content in backfat. Despite for cook loss and dressing percentage, no sire-feed interactions were found. This indicates no need for a performance test, specifically designed for organic production. However, weight of the breeding values for the various traits and selection criteria should be adapted to the needs of organic production.

Effects of short-term methionine and cysteine restriction and enrichment with polyunsaturated fatty acids on oral glucose tolerance, plasma amino acids, fatty acids, lactate and pyruvate: results from a pilot study

Objective

In this 7-day pilot study we randomized healthy, normal-weight men and women to either a dietary intervention with methionine and cysteine restriction enriched in PUFA (Met/Cys_low + PUFA, n = 7) or with high contents of methionine, cysteine and SFA (Met/Cys_high + SFA, n = 7). The objective was to describe the short-term responses in oral glucose tolerance, amino acid profile, total fatty acid profile, pyruvate and lactate following a Met/Cys_low + PUFA diet vs. Met/Cys_high + SFA.

Results

The diet groups consisted of five women and two men, aged 20–38 years. After the 7-d intervention median pre- and post-oral glucose tolerance test (OGTT) glucose concentrations were 5 mmol/L and 4 mmol/L respectively in the Met/Cys_low + PUFA group. In the Met/Cys_high + SFA group, median pre- and post-OGTT glucose concentrations were 4.8 mmol/L and 4.65 mmol/L after the 7-d intervention. The responses in the amino acid profiles were similar in both groups during the intervention with the exception of serine. Fatty acids decreased from baseline to day 7 in both groups. Plasma lactate and pyruvate were similar for both groups with an increase to day 3 before approaching baseline values at day 7.

Trial registration

ClinicalTrials.gov: NCT02647970, registration date: January 6^th 2016.

Dietary methionine restriction improves the impairment of cardiac function in middle-aged obese mice

Dietary methionine restriction (MR) has been reported to extend lifespan, reduce obesity and decrease oxidative damage to mtDNA in the heart of rats, and increase endogenous hydrogen sulfide (H2S) production in the liver and blood. H2S has many potential benefits in the pathophysiology of the cardiovascular system. MR also increases the level of homocysteine (Hcy) in the liver and plasma, but elevated plasma Hcy is a risk factor for cardiovascular disease. Therefore, this study aimed to determine the effect of MR on cardiac function and metabolic status in obese middle-aged mice and its possible mechanisms. C57BL/6J mice (aged approximately 28 weeks) were divided into six dietary groups: CON (0.86% methionine + 4% fat), CMR40 (0.52% methionine + 4% fat), CMR80 (0.17% methionine + 4% fat), HFD (0.86% methionine + 24% fat), HMR40 (0.52% methionine + 24% fat) and HMR80 (0.17% methionine + 24% fat) for 15 consecutive weeks. Our results showed that 80% MR improves systolic dysfunction in middle-aged obese mice and enhances myocardial energy metabolism. 80% MR also reduces myocardial oxidative stress and improves inflammatory response. In addition, 80% MR increased mice Hcy levels and activated remethylation and transsulfur pathways of Hcy and promoted endogenous H2S production in the heart. 40% MR has the same trend, but is not significant. Moreover 40% MR at variance with 80% MR, did not decrease the body weight in both control and high-fat diet mice. These findings suggest that MR can improve myocardial energy metabolism, reduce heart inflammation and oxidative stress by increasing cardiac H2S production, and improve cardiac dysfunction in middle-aged obese mice.

Effects of Varying Dietary DL-Methionine Levels on Productive and Reproductive Performance, Egg Quality, and Blood Biochemical Parameters of Quail Breeders

Simple Summary

This study investigated the effects of different DL-methionine levels on quail breeders kept from 8–16 weeks of age. The results revealed that using DL-methionine at levels of 0.5 or 1.5 g/kg improved the liver and kidney functions, lipid profile, immunity and antioxidant parameters of quail breeders.

Abstract

The present study was carried out to study the effects of varying dietary DL-methionine (0, 0.5, 1.5, 2.5, and 3.5 g/kg) levels on the productive and reproductive performance, egg quality and blood biochemical parameters of quail breeders. In total, 150 mature Japanese quails at eight weeks of age were randomly allotted to five groups of 30 for each group. Each group included five replicates, each of six quails (four females and two males). The results showed that egg number, egg weight and egg mass were higher (p < 0.05) with the addition of all DL-methionine levels than that of the control group. Quails from the control group had a lower feed intake (p < 0.001) and a worse feed conversion ratio (FCR) than those from the DL-methionine-treated groups. Supplementation of DL-methionine up to 2.5 g/kg in quail diets increased fertility and hatchability percentages. Birds fed DL-methionine at 1.5 g/kg had the best egg production indices, better FCR and the highest values of fertility and hatchability. Egg weight, yolk %, Haugh unit, egg shape index and unit surface shell weight (USSW) were increased and eggshell % was decreased in quail supplemented with DL-methionine levels compared with the control quail (p < 0.05). Dietary DL-methionine levels did not affect (p > 0.05) the hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs) and packed cell volume (PCV) of quails. DL-methionine levels (0.5 and 2.5 g/kg) augmented lymphocytes and basophile (p < 0.05). Low DL-methionine levels (0.5 or 1.5 g/kg) improved liver enzymes and kidney functions. Dietary DL-methionine levels (except 3.5 g/kg) declined serum lactate dehydrogenase (LDH) and decreased lipid profile parameters (except high-density lipoprotein—HDL). Supplementation of DL-methionine at 0.5 and 1.5 g/kg increased immunoglobulin (IgG, IgM and IgA) and superoxide dismutase (SOD), total antioxidant capacity (TAC), catalase (CAT) and reduced glutathione (GSH) (p < 0.001) compared with the control. In conclusion, dietary supplementation of DL-methionine (1.5 g/kg) can enhance the reproductive performance and egg quality of quail breeders. DL-methionine use at levels of 0.5 or 1.5 g/kg improved the liver and kidney functions, lipid profile, immunity and antioxidant parameters of Japanese quail.

Metabolomic Analysis of SCD during Goose Follicular Development: Implications for Lipid Metabolism

Stearoyl-CoA desaturase (SCD) is known to be an important rate-limiting enzyme in the production of monounsaturated fatty acids (MUFAs). However, the role of this enzyme in goose follicular development is poorly understood. To investigate the metabolic mechanism of SCD during goose follicular development, we observed its expression patterns in vivo and in vitro using quantitative reverse-transcription (qRT)-PCR. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine a cellular model of SCD function in granulosa cells (GCs) via SCD overexpression and knockdown. qRT-PCR analysis showed that SCD was abundantly expressed in the GC layer, and was upregulated in preovulatory follicles. Peak expression was found in F1 and prehierarchal follicles with diameters of 4–6 mm and 8–10 mm, respectively. We further found that mRNA expression and corresponding enzyme activity occur in a time-dependent oscillation pattern in vitro, beginning on the first day of GC culture. By LC-MS/MS, we identified numerous changes in metabolite activation and developed an overview of multiple metabolic pathways, 10 of which were associated with lipid metabolism and enriched in both the overexpressed and knockdown groups. Finally, we confirmed cholesterol and pantothenol or pantothenate as potential metabolite biomarkers to study SCD-related lipid metabolism in goose GCs.

Methionine restriction alleviates high-fat diet-induced obesity: Involvement of diurnal metabolism of lipids and bile acids

Circadian misalignment induced by a high-fat diet (HFD) increases the risk of metabolic diseases. Methionine restriction (MR) is known to have the potential of alleviating obesity by improving insulin sensitivity. However, the role of the circadian clock in mediating the effects of MR on obesity-related metabolic disorders remains unclear. Ten-week-old male C57BL/6 J mice were fed with a low-fat diet (LFD) or a HFD for 4 wk., followed with a full diet (0.86% methionine, w/w) or a methionine-restricted diet (0.17% methionine, w/w) for 8 wk. Our results showed that MR attenuated insulin resistance triggered by HFD, especially at ZT12. Moreover, MR led to a time-specific enhancement of the expression of FGF21 and activated the AMPK/PGC-1α signaling. Notably, MR upregulated the cyclical levels of cholic acid (CA) and chenodeoxycholic acid (CDCA), and downregulated the cyclical level of deoxycholic acid (DCA) in the dark phase. MR restored the HFD-disrupted cyclical fluctuations of lipidolysis genes and BAs synthetic genes and improved the circulating lipid profile. Also, MR improved the expressions of clock-controlled genes (CCGs) in the liver and the brown adipose tissue throughout one day. In conclusion, MR exhibited the lipid-lowering effects on HFD-induced obesity and restored the diurnal metabolism of lipids and BAs, which could be partly explained by improving the expression of CCGs. These findings suggested that MR could be a potential nutritional intervention for attenuating obesity-induced metabolic misalignment.

Chronic Gastritis Is Associated with a Decreased High-Density Lipid Level: Histological Features of Gastritis Based on the Updated Sydney System

Chronic gastritis could activate a systemic inflammatory response that could result in adverse lipid profiles. To determine the severity of chronic gastritis, Helicobacter pylori (HP), mononuclear cell (lymphocytes and plasma cells), and neutrophil scores were assessed on the basis of the updated Sydney system (USS), which is widely used for histological grading. The aim of this study was to assess the relationships between gastric histological features and lipid profile levels. This study included 15,322 males and 5929 females who underwent a health checkup and gastric biopsy at the Kangbuk Samsung Medical Center (KBSMC). We analyzed whether the HP, mononuclear cell, and neutrophil grades according to the USS were related to serum leukocyte count, unhealthy behaviors, and lipid profile levels. Gastritis with HP, neutrophils, or moderate to severe mononuclear cells was associated with an elevated serum leukocyte count. A high leukocyte count was related to increased low-density lipoproteins (LDL) and triglycerides/very-low-density lipoprotein (VLDL) and decreased high-density lipoproteins (HDL). In multivariate analyses, chronic gastritis with HP or moderate to severe mononuclear cells was significantly associated with decreased HDL in males, while mononuclear cells were significantly related to decreased HDL in females. Chronic gastritis was associated with an increased systemic inflammatory response, which was associated with unfavorable lipid profiles, especially low HDL levels.

Effects of dietary methionine and cysteine restriction on plasma biomarkers, serum fibroblast growth factor 21, and adipose tissue gene expression in women with overweight or obesity: a double-blind randomized controlled pilot study

Background

Dietary restriction of methionine and cysteine is a well-described model that improves metabolic health in rodents. To investigate the translational potential in humans, we evaluated the effects of dietary methionine and cysteine restriction on cardiometabolic risk factors, plasma and urinary amino acid profile, serum fibroblast growth factor 21 (FGF21), and subcutaneous adipose tissue gene expression in women with overweight and obesity in a double-blind randomized controlled pilot study.

Methods

Twenty women with overweight or obesity were allocated to a diet low (Met/Cys_-low, n = 7), medium (Met/Cys_-medium, n = 7) or high (Met/Cys_-high, n = 6) in methionine and cysteine for 7 days. The diets differed only by methionine and cysteine content. Blood and urine were collected at day 0, 1, 3 and 7 and subcutaneous adipose tissue biopsies were taken at day 0 and 7.

Results

Plasma methionine and cystathionine and urinary total cysteine decreased, whereas FGF21 increased in the Met/Cys_-low vs. Met/Cys_-high group. The Met/Cys_-low group had increased mRNA expression of lipogenic genes in adipose tissue including DGAT1. When we excluded one participant with high fasting insulin at baseline, the Met/Cys_-low group showed increased expression of ACAC, DGAT1, and tendencies for increased expression of FASN and SCD1 compared to the Met/Cys_-high group. The participants reported satisfactory compliance and that the diets were moderately easy to follow.

Conclusions

Our data suggest that dietary methionine and cysteine restriction may have beneficial effects on circulating biomarkers, including FGF21, and influence subcutaneous adipose tissue gene expression. These results will aid in the design and implementation of future large-scale dietary interventions with methionine and cysteine restriction.

Trial registration ClinicalTrials.gov Identifier: NCT03629392, registration date: 14/08/2018 https://clinicaltrials.gov/ct2/show/NCT03629392.

Association of sulfur amino acid consumption with cardiometabolic risk factors: Cross-sectional findings from NHANES III

BACKGROUND

An average adult American consumes sulfur amino acids (SAA) at levels far above the Estimated Average Requirement (EAR) and recent preclinical data suggest that higher levels of SAA intake may be associated with a variety of aging-related chronic diseases. However, there are little data regarding the relationship between SAA intake and chronic disease risk in humans. The aim of this study was to examine the associations between consumption of SAA and risk factors for cardiometabolic diseases.

METHODS

The sample included 11,576 adult participants of the Third National Examination and Nutritional Health Survey (NHANES III) Study (1988-1994). The primary outcome was cardiometabolic disease risk score (composite risk factor based on blood cholesterol, triglycerides, HDL, C-reactive protein (CRP), uric acid, glucose, blood urea nitrogen (BUN), glycated hemoglobin, insulin, and eGFR). Group differences in risk score by quintiles of energy-adjusted total SAA, methionine (Met), and cysteine (Cys) intake were determined by multiple linear regression after adjusting for age, sex, BMI, smoking, alcohol intake, and dietary factors. We further examined for associations between SAA intake and individual risk factors.

FINDINGS

Mean SAA consumption was > 2.5-fold higher than the EAR. After multivariable adjustment, higher intake of SAA, Met, and Cys were associated with significant increases in composite cardiometabolic disease risk scores, independent of protein intake, and with several individual risk factors including serum cholesterol, glucose, uric acid, BUN, and insulin and glycated hemoglobin (p < 0.01).

INTERPRETATION

Overall, our findings suggest that diets lower in SAA (close to the EAR) are associated with reduced risk for cardiometabolic diseases. Low SAA dietary patterns rely on plant-derived protein sources over meat derived foods. Given the high intake of SAA among most adults, our findings may have important public health implications for chronic disease prevention.

FUNDING

This study does not have any funding.

Methionine metabolism and methyltransferases in the regulation of aging and lifespan extension across species

Methionine restriction (MetR) extends lifespan across different species and exerts beneficial effects on metabolic health and inflammatory responses. In contrast, certain cancer cells exhibit methionine auxotrophy that can be exploited for therapeutic treatment, as decreasing dietary methionine selectively suppresses tumor growth. Thus, MetR represents an intervention that can extend lifespan with a complementary effect of delaying tumor growth. Beyond its function in protein synthesis, methionine feeds into complex metabolic pathways including the methionine cycle, the transsulfuration pathway, and polyamine biosynthesis. Manipulation of each of these branches extends lifespan; however, the interplay between MetR and these branches during regulation of lifespan is not well understood. In addition, a potential mechanism linking the activity of methionine metabolism and lifespan is regulation of production of the methyl donor S-adenosylmethionine, which, after transferring its methyl group, is converted to S-adenosylhomocysteine. Methylation regulates a wide range of processes, including those thought to be responsible for lifespan extension by MetR. Although the exact mechanisms of lifespan extension by MetR or methionine metabolism reprogramming are unknown, it may act via reducing the rate of translation, modifying gene expression, inducing a hormetic response, modulating autophagy, or inducing mitochondrial function, antioxidant defense, or other metabolic processes. Here, we review the mechanisms of lifespan extension by MetR and different branches of methionine metabolism in different species and the potential for exploiting the regulation of methyltransferases to delay aging.

Methionine restriction at the post-weanling period promotes muscle fiber transition in piglets and improves intramuscular fat content in growing-finishing pigs

The effects of methionine restriction on lipid metabolism in the liver and adipose tissue have been well determined, while its effects on the skeletal muscle have not been fully studied. The present study was conducted to explore whether methionine restriction in weanling piglets would affect skeletal muscle lipid content and fiber type and whether such changes would further affect the meat quality of growing-finishing pigs. A total of 28 crossbred healthy barrows weaned at the age of 21 days were randomly allotted to two treatments and fed either a methionine-restricted diet (0.25% methionine) or a control diet (0.48% methionine) for 4 weeks. After this period, the pigs were fed the same basal diet throughout the growing-finishing period. The results showed that methionine restriction during the post-weanling period of piglets enhanced lipid accumulation and promoted the formation of slow-twitch muscle fibers in the skeletal muscle, while it had no effects on growth performance. We hypothesized that such effects might be mediated by AMPK-PGC-1α signaling pathway. Furthermore, the effects of methionine restriction on the skeletal muscle of pigs at the post-weanling period had a subsequent effect on growing-finishing pigs, which showed a higher intramuscular fat content. Our results suggest that dietary methionine restriction in piglets at an early stage might be an alternative method for improving meat quality.

Effects of Aging and Methionine Restriction on Rat Kidney Metabolome

Methionine restriction (MetR) in animal models extends maximum longevity and seems to promote renoprotection by attenuating kidney injury. MetR has also been proven to affect several metabolic pathways including lipid metabolism. However, there is a lack of studies about the effect of MetR at old age on the kidney metabolome. In view of this, a mass spectrometry-based high-throughput metabolomic and lipidomic profiling was undertaken of renal cortex samples of three groups of male rats-An 8-month-old Adult group, a 26-month-old Aged group, and a MetR group that also comprised of 26-month-old rats but were subjected to an 80% MetR diet for 7 weeks. Additionally, markers of mitochondrial stress and protein oxidative damage were analyzed by mass spectrometry. Our results showed minor changes during aging in the renal cortex metabolome, with less than 59 differential metabolites between the Adult and Aged groups, which represents about 4% of changes in the kidney metabolome. Among the compounds identified are glycerolipids and lipid species derived from arachidonic acid metabolism. MetR at old age preferentially induces lipid changes affecting glycerophospholipids, docosanoids, and eicosanoids. No significant differences were observed between the experimental groups in the markers of mitochondrial stress and tissue protein damage. More than rejuvenation, MetR seems to induce a metabolic reprogramming.

The effects of dietary methionine restriction on the function and metabolic reprogramming in the liver and brain - implications for longevity

Methionine is an essential sulphur-containing amino acid involved in protein synthesis, regulation of protein function and methylation reactions. Dietary methionine restriction (0.12-0.17% methionine in food) extends the life span of various animal species and delays the onset of aging-associated diseases and cancers. In the liver, methionine restriction attenuates steatosis and delays the development of non-alcoholic steatohepatitis due to antioxidative action and metabolic reprogramming. The limited intake of methionine stimulates the fatty acid oxidation in the liver and the export of lipoproteins as well as inhibits de novo lipogenesis. These effects are mediated by various signaling pathways and effector molecules, including sirtuins, growth hormone/insulin-like growth factor-1 axis, sterol regulatory element binding proteins, adenosine monophosphate-dependent kinase and general control nonderepressible 2 pathway. Additionally, methionine restriction stimulates the synthesis of fibroblast growth factor-21 in the liver, which increases the insulin sensitivity of peripheral tissues. In the brain, methionine restriction delays the onset of neurodegenerative diseases and increases the resistance to various forms of stress through antioxidative effects and alterations in lipid composition. This review aimed to summarize the morphological, functional and molecular changes in the liver and brain caused by the methionine restriction, with possible implications in the prolongation of maximal life span.

MetAP2 inhibition increases energy expenditure through direct action on brown adipocytes

Inhibitors of methionine aminopeptidase 2 (MetAP2) have been shown to reduce body weight in obese mice and humans. The target tissue and cellular mechanism of MetAP2 inhibitors, however, have not been extensively examined. Using compounds with diverse chemical scaffolds, we showed that MetAP2 inhibition decreases body weight and fat mass and increases lean mass in the obese mice but not in the lean mice. Obesity is associated with catecholamine resistance and blunted β-adrenergic receptor signaling activities, which could dampen lipolysis and energy expenditure resulting in weight gain. In the current study, we examined effect of MetAP2 inhibition on brown adipose tissue and brown adipocytes. Norepinephrine increases energy expenditure in brown adipose tissue by providing fatty acid substrate through lipolysis and by increasing expression of uncoupled protein-1 (UCP1). Metabolomic analysis shows that in response to MetAP2 inhibitor treatment, fatty acid metabolites in brown adipose tissue increase transiently and subsequently decrease to basal or below basal levels, suggesting an effect on fatty acid metabolism in this tissue. Treatment of brown adipocytes with MetAP2 inhibitors enhances norepinephrine-induced lipolysis and energy expenditure, and prolongs the activity of norepinephrine to increase ucp1 gene expression and energy expenditure in norepinephrine-desensitized brown adipocytes. In summary, we showed that the anti-obesity activity of MetAP2 inhibitors can be mediated, at least in part, through direct action on brown adipocytes by enhancing β-adrenergic-signaling-stimulated activities.

Dietary methionine increased the lipid accumulation in juvenile tiger puffer Takifugu rubripes

Methionine (Met) is one of the most important amino acids in fish feed. The effects of dietary Met on lipid deposition in fish varied a lot among different studies. The present study was aimed at investigating the effects of dietary Met supplementation on the lipid accumulation in tiger puffer, which have a unique lipid storage pattern. Crystalline L-Met was supplemented to a low-fishmeal control diet to obtain two experimental diets with a low (1.1% of dry weight, L-MET) or high Met level (1.6% of dry weight, H-MET). A 67-day feeding trial was conducted with juvenile tiger puffer (average initial weight, 13.83 g). Each diet was fed to triplicate tanks (30 fish in each tank). The results showed that the total lipid contents in whole-body and liver significantly increased with increasing dietary Met levels. The hepatosomatic index, weight gain, and total bile acid content in serum showed similar patterns in response to dietary Met treatments, while the lipid content in muscle was not affected. The hepatic contents of 18-carbon fatty acids were elevated by dietary Met supplementation. The Hepatic mRNA expression of lipogenetic gene such as FAS, GPAT, PPARγ, ACLY, and SCD1 was down-regulated, while the gene expression of lipolytic genes ACOX1 and HSL, as well as that of ApoB100, were up-regulated by increasing dietary Met levels. The hepatic lipidomics of experimental fish was also analyzed. In conclusion, increasing dietary Met levels (0.61%, 1.10%, and 1.60%) increased the hepatic lipid accumulation in tiger puffer. The mechanisms involved warrant further studies.

Dietary methionine restriction reduces hepatic steatosis and oxidative stress in high-fat-fed mice by promoting H2S production

Dietary methionine restriction reduces hepatic steatosis and oxidative stress in high-fat-fed mice by promoting H₂S production.

Metabolic Regulation of Methionine Restriction in Diabetes

Although the effects of dietary methionine restriction have been investigated in the physiology of aging and diseases related to oxidative stress, the relationship between methionine restriction (MR) and the development of metabolic disorders has not been explored extensively. This review summarizes studies of the possible involvement of dietary methionine restriction in improving insulin resistance, glucose homeostasis, oxidative stress, lipid metabolism, the pentose phosphate pathway (PPP), and inflammation, with an emphasis on the fibroblast growth factor 21 and protein phosphatase 2A signals and autophagy in diabetes. Diets deficient in methionine may be a useful nutritional strategy in patients with diabetes.

Upstream regulators of apoptosis mediates methionine-induced changes of lipid metabolism

Although the role of methionine (Met), as precursor for l-carnitine synthesis, in the regulation of lipid metabolism has been explored. Met seems to have tissue- and species-specific regulatory effect on lipid metabolism, implying that the mechanisms in Met regulation of lipid metabolism is complex and may involve the upstream regulatory pathway of lipid metabolism. The present study was performed to determine the mechanism of apoptosis signaling pathways mediating Met-induced changes of hepatic lipid deposition and metabolism in fish, and compare the differences of the mechanisms between the fish and mammals. By iTRAQ-based quantitative proteome analyses, we found that both dietary Met deficiency and excess evoked apoptosis signaling pathways, increased hepatic lipid deposition and caused aberrant hepatic lipid metabolism of yellow catfish Pelteobagrus fulvidraco. Using primary hepatocytes from P. fulvidraco, inhibition of caspase by Z-VAD-FMK blocked the apoptotic signaling pathways with a concomitant reversal of Met deficiency- and excess-induced increase of lipid deposition, indicating that apoptosis involved the Met-mediated changes of hepatic lipid metabolism. Moreover, we explored the roles of three upstream apoptotic signaling pathways (PI3K/AKT-TOR pathway, cAMP/PKA/CREB pathway and LKB1/AMPK-FOXO pathway) influencing hepatic lipid metabolism of P. fulvidraco. The three upstream pathways participated in apoptosis mediating Met-induced changes of lipid metabolism in P. fulvidraco. At last, HepG2 cell line was used to compare the similarities of mechanisms in apoptosis mediating Met-induced changes of lipid metabolism between fish and mammals. Although several slight differences existed, apoptosis mediated the Met-induced changes of lipid metabolism between fish and mammals. The present study reveals novel apoptosis-relevant signal transduction axis which mediates the Met-induced changes of lipid metabolism, which will help understand the mechanistic link between apoptosis and lipid metabolism, and highlight the importance of the evolutionary conservative apoptosis signaling axis in regulating Met-induced changes of hepatic lipid metabolism.

Dietary methionine restriction regulated energy and protein homeostasis by improving thyroid function in high fat diet mice

Methionine-restricted diets (MRD) show an integrated series of beneficial health effects, including improving insulin sensitivity, limiting fat deposition, and decreasing oxidative stress, and inflammation responses. We aimed to explore the systemic responses to a MRD in mice fed with a high fat (HFD) and clarify the possible mechanism. Mice were fed with a control diet (0.86% methionine + 4% fat, CON), HFD (0.86% methionine + 20% fat), or MRD (0.17% methionine + 20% fat) for 22 consecutive weeks. HFD-fed mice showed widespread systemic metabolic disorders and thyroid dysfunction. A MRD significantly increased energy expenditure (e.g. fatty acid oxidation, glycolysis, and tricarboxylic acid cycle metabolism), regulated protein homeostasis, improved gut microbiota functions, prevented thyroid dysfunction, increased plasma thyroxine and triiodothyronine levels, decreased plasma thyroid stimulating hormone levels, increased type 2 deiodinase (DIO2) activity, and up-regulated mRNA and protein expression levels of DIO2 and thyroid hormone receptor α1 in the skeletal muscle. These results suggest that a MRD can improve the metabolic disorders induced by a HFD, and especially regulate energy and protein homeostasis likely through improved thyroid function. Thus, reducing methionine intake (e.g. through a vegan diet) may improve metabolic health in animals and humans.

Disease prevention and delayed aging by dietary sulfur amino acid restriction: translational implications

Sulfur amino acids (SAAs) play numerous critical roles in metabolism and overall health maintenance. Preclinical studies have demonstrated that SAA-restricted diets have many beneficial effects, including extending life span and preventing the development of a variety of diseases. Dietary sulfur amino acid restriction (SAAR) is characterized by chronic restrictions of methionine and cysteine but not calories and is associated with reductions in body weight, adiposity and oxidative stress, and metabolic changes in adipose tissue and liver resulting in enhanced insulin sensitivity and energy expenditure. SAAR-induced changes in blood biomarkers include reductions in insulin, insulin-like growth factor-1, glucose, and leptin and increases in adiponectin and fibroblast growth factor 21. On the basis of these preclinical data, SAAR may also have similar benefits in humans. While little is known of the translational significance of SAAR, its potential feasibility in humans is supported by findings of its effectiveness in rodents, even when initiated in adult animals. To date, there have been no controlled feeding studies of SAAR in humans; however, there have been numerous relevant epidemiologic and disease-based clinical investigations reported. Here, we summarize observations from these clinical investigations to provide insight into the potential effectiveness of SAAR for humans.

Serine prevented high-fat diet-induced oxidative stress by activating AMPK and epigenetically modulating the expression of glutathione synthesis-related genes

Serine deficiency has been observed in patients with nonalcoholic fatty liver disease (NAFLD). Whether serine supplementation has any beneficial effects on the prevention of NAFLD remains unknown. The present study was conducted to investigate the effects of serine supplementation on hepatic oxidative stress and steatosis and its related mechanisms. Forty male C57BL/6J mice (9week-old) were randomly assigned into four groups (n=10) and fed: i) a low-fat diet; ii) a low-fat diet supplemented with 1% (wt:vol) serine; iii) a high-fat (HF) diet; and iv) a HF diet supplemented with 1% serine, respectively. Palmitic acid (PA)-treated primary hepatocytes separated from adult mice were also used to study the effects of serine on oxidative stress. The results showed that serine supplementation increased glucose tolerance and insulin sensitivity, and protected mice from hepatic lipid accumulation, but did not significantly decreased HF diet-induced weight gain. In addition, serine supplementation protected glutathione (GSH) antioxidant system and prevented hypermethylation in the promoters of glutathione synthesis-related genes, while decreasing reactive oxygen species (ROS) in mice fed a HF diet. Moreover, we found that serine supplementation increased phosphorylation and S-glutathionylation of AMP-activated protein kinase α subunit (AMPKα), and decreased ROS, malondialdehyde and triglyceride contents in PA-treated primary hepatocytes. However, while AMPK activity or GSH synthesis was inhibited, the abovementioned effects of serine on PA-treated primary hepatocytes were not observed. Our results suggest that serine supplementation could prevent HF diet-induced oxidative stress and steatosis by epigenetically modulating the expression of glutathione synthesis-related genes and through AMPK activation.

Pleiotropic responses to methionine restriction

Methionine restriction (MR) extends lifespan across different species. The main responses of rodent models to MR are well-documented in adipose tissue (AT) and liver, which have reduced mass and improved insulin sensitivity, respectively. Recently, molecular mechanisms that improve healthspan have been identified in both organs during MR. In fat, MR induced a futile lipid cycle concomitant with beige AT accumulation, producing elevated energy expenditure. In liver, MR upregulated fibroblast growth factor 21 and improved glucose metabolism in aged mice and in response to a high-fat diet. Furthermore, MR also reduces mitochondrial oxidative stress in various organs such as liver, heart, kidneys, and brain. Other effects of MR have also been reported in such areas as cardiac function in response to hyperhomocysteinemia (HHcy), identification of molecular mechanisms in bone development, and enhanced epithelial tight junction. In addition, rodent models of cancer responded positively to MR, as has been reported in colon, prostate, and breast cancer studies. The beneficial effects of MR have also been documented in a number of invertebrate model organisms, including yeast, nematodes, and fruit flies. MR not only promotes extended longevity in these organisms, but in the case of yeast has also been shown to improve stress tolerance. In addition, expression analyses of yeast and Drosophila undergoing MR have identified multiple candidate mediators of the beneficial effects of MR in these models. In this review, we emphasize other in vivo effects of MR such as in cardiovascular function, bone development, epithelial tight junction, and cancer. We also discuss the effects of MR in invertebrates.