Dietary Methionine Restriction Research Articles

Dietary Methionine Restriction Signals to the Brain Through Fibroblast Growth Factor 21 to Regulate Energy Balance and Remodeling of Adipose Tissue.

Restricting dietary methionine to 0.17% in mice increases energy expenditure (EE), reduces fat deposition, and improves metabolic health by increasing hepatic fibroblast growth factor 21 (FGF21). The goal of this study was to compare each of these responses in mice with the coreceptor for FGF21 deleted in either adipose tissue or the brain. Methionine-restriction (MR) diets were fed to age-matched cohorts of mice with the coreceptor for FGF21 deleted in either adipose tissue or the brain. The physiological and transcriptional responses to MR were compared in the respective cohorts. Tissue-specific deletion of the FGF21 coreceptor in adipose tissue did not abrogate the ability of dietary MR to increase EE and reduce fat deposition. Tissue-specific deletion of the FGF21 coreceptor from the brain produced mice that were unable to respond to the effects of MR on EE or the remodeling of adipose tissue. The increase in FGF21 produced by dietary MR acts primarily in the brain to produce its physiological effects on energy balance. In contrast, the effects of MR on hepatic gene expression were intact in both models, supporting a mechanism that directly links detection of reduced methionine in the liver to transcriptional mechanisms that alter gene expression in the liver.

Dietary methionine restriction attenuates renal ischaemia/reperfusion-induced myocardial injury by activating the CSE/H2S/ERS pathway in diabetic mice.

Methionine restrictive diet may alleviate ischaemia/reperfusion (I/R)‐induced myocardial injury, but its underlying mechanism remains unclear. HE staining was performed to evaluate the myocardial injury caused by I/R and the effect of methionine‐restricted diet (MRD) in I/R mice. IHC and Western blot were carried out to analyse the expression of CSE, CHOP and active caspase3 in I/R mice and hypoxia/reoxygenation (H/R) cells. TUNEL assay and flow cytometry were used to assess the apoptotic status of I/R mice and H/R cells. MTT was performed to analyse the proliferation of H/R cells. H2S assay was used to evaluate the concentration of H2S in the myocardial tissues and peripheral blood of I/R mice. I/R‐induced mediated myocardial injury and apoptosis were partially reversed by methionine‐restricted diet (MRD) via the down‐regulation of CSE expression and up‐regulation of CHOP and active caspase3 expression. The decreased H2S concentration in myocardial tissues and peripheral blood of I/R mice was increased by MRD. Accordingly, in a cellular model of I/R injury established with H9C2 cells, cell proliferation was inhibited, cell apoptosis was increased, and the expressions of CSE, CHOP and active caspase3 were dysregulated, whereas NaHS treatment alleviated the effect of I/R injury in H9C2 cells in a dose‐dependent manner. This study provided a deep insight into the mechanism underlying the role of MRD in I/R‐induced myocardial injury.

Mechanism of Activation of Mechanistic Target of Rapamycin Complex 1 by Methionine.

Nutrients are closely involved in the regulation of lifespan and metabolic health. Cellular activities, such as the regulation of metabolism, growth, and aging, are mediated by a network of nutrients and nutrient-sensing pathways. Among the nutrient-sensing pathways, the mechanistic target of rapamycin complex 1 (mTORC1) acts as the central regulator of cellular functions, which include autophagy. Autophagy plays a significant role in the removal of protein aggregates and damaged or excess organelles, including mitochondria, to maintain intracellular homeostasis, which is involved in lifespan extension and cardiometabolic health. Moreover, dietary methionine restriction may have a beneficial effect on lifespan extension and metabolic health. In contrast, methionine may activate mTORC1 and suppress autophagy. As the mechanism of methionine sensing on mTORC1, SAMTOR was identified as a sensor of S-adenosyl methionine (SAM), a metabolite of methionine, in the cytoplasm. Conversely, methionine may activate the mTORC1 signaling pathway through the activation of phosphatase 2A (PP2A) because of increased methylation in response to intracellular SAM levels. In this review, we summarized the recent findings regarding the mechanism via which methionine activates mTORC1.

Methionine Restriction Regulates Cognitive Function in High-Fat Diet-Fed Mice: Roles of Diurnal Rhythms of SCFAs Producing- and Inflammation-Related Microbes.

Methionine restriction (MR) is known to potently alleviate inflammation and improve gut microbiome in obese mice. The gut microbiome exhibits diurnal rhythmicity in composition and function, and this, in turn, drives oscillations in host metabolism. High-fat diet (HFD) strongly altered microbiome diurnal rhythmicity, however, the role of microbiome diurnal rhythmicity in mediating the improvement effects of MR on obesity-related metabolic disorders remains unclear. 10-week-old male C57BL/6J mice are fed a low-fat diet or HFD for 4 weeks, followed with a full diet (0.86% methionine, w/w) or a methionine-restricted diet (0.17% methionine, w/w) for 8 weeks. Analyzing microbiome diurnal rhythmicity at six time points, the results show that HFD disrupts the cyclical fluctuations of the gut microbiome in mice. MR partially restores these cyclical fluctuations, which lead to time-specifically enhance the abundance of short-chain fatty acids producing bacteria, increases the acetate and butyric, and dampens the oscillation of inflammation-related Desulfovibrionales and Staphylococcaceae over the course of 1 day. Notably, MR, which protects against systemic inflammation, influences brain function and synaptic plasticity. MR could serve as a potential nutritional intervention for attenuating obesity-induced cognitive impairments by balancing the circadian rhythm in microbiome-gut-brain homeostasis.

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.

Hypermethioninemia Leads to Fatal Bleeding and Increased Mortality in a Transgenic I278T Mouse Model of Homocystinuria.

Severely elevated plasma homocysteine and methionine lead to thromboembolic events and strokes in homocystinuric (HCU) patients. Mouse models of HCU failed to exhibit prothrombotic phenotype, presumably due to lack of hypermethioninemia. We evaluated the impact of hypermethioninemia together with hyperhomocysteinemia on murine HCU phenotype and compared the efficacy of the current and novel therapies for HCU. High methionine intake decreased survival of I278T mice, which died from intestinal bleeding with hepatic and pancreatic failure. I278T mice on normal or increased methionine intake developed endothelial dysfunction, but paradoxically demonstrated delayed occlusion in an induced arterial thrombosis model. RNA-seq analysis suggested that expression of coagulation factor XI (FXI) is downregulated in livers of I278T mice. Indeed, plasma concentrations of FXI were decreased in I278T mice on normal diet and further reduced by increased methionine intake. Dietary methionine restriction normalized the observed phenotype. Similarly, treatment with OT-58, a novel enzyme therapy for HCU, corrected the phenotype in I278T mice regardless of their dietary methionine intake. Hypermethioninemia does not contribute to prothrombotic phenotype in murine HCU. Downregulation of FXI may contribute to the lack of prothrombotic tendency in I278T mice. Methionine restriction or treatment with OT-58 corrects vascular disease in the I278T mouse model of HCU.

Dietary Methionine Restriction Ameliorated Fat Accumulation, Systemic Inflammation, and Increased Energy Metabolism by Altering Gut Microbiota in Middle-Aged Mice Administered Different Fat Diets.

Diet greatly influences gut microbiota. Dietary methionine restriction (MR) prevents and ameliorates age-related or high-fat-induced diseases and prolongs life span. This study aimed to reveal the impact of MR on gut microbiota in middle-aged mice with low-, medium-, high-fat diets. C57BL/6J mice were randomly divided into six groups with different MR and fat-content diets. Multiple indicators of intestinal function, fat accumulation, energy consumption, and inflammation were measured. 16S rRNA gene sequencing was used to analyze cecal microbiota. Our results indicated that MR considerably reduced the concentrations of lipopolysaccharide (LPS) and increased short-chain fatty acids (SCFAs) by upregulating the abundance of Corynebacterium and SCFA-producing bacteria Bacteroides, Faecalibaculum, and Roseburia and downregulating the LPS-producing or proinflammatory bacteria Desulfovibrio and Escherichia-Shigella. The effect of MR on LPS and SCFAs further reduced fat accumulation and systemic inflammation, enhanced heat production, and mediated the LPS/LBP/CD14/ TLR4 pathway to strength the intestinal mucosal immunity barrier in middle-aged mice.

P0920THE METHIONINE RESTRICTION DIET ATTENUATES CHRONIC KIDNEY PROGRESSION IN MICE

Abstract Background and Aims The clinical usefulness of protein-restricted diets is known to slow the progression of obesity, fatty liver, aging and cancer. Protein-restricted diet in chronic kidney disease is known to alleviate the deterioration of the renal function. The purpose of this study is to confirm whether the reduction in new function can be improved when methionine restricted (MR) diet is supplied in the chronic kidney disease (CKD) animal model and to study the its renoprotection mechanism. Method We used four-week-old C57L/B6 to make a CKD model by administration 0.025% adenine chow mixed with R3 diet for four weeks for the control group. For the MR diet group, we supplied the mixture of 0.025% adenine with methionine/Choline Deficient Diet. We measured serum blood urea nitrogen (BUN), serum creatinine, gut permeability, stool short chain fatty acid (SCFA), kidney α-SMA and renal pathology. This study was approved by Korea University Institutional Animal Care and Use Committee (KOREA-2019-0047). Results The principal coordinates analysis of the microbiome showed the two groups have distinctive component features. The stool SCFA, especially butyrate was increased in the MR diet group. However, gut permeability using FITC-dextran showed no significant change. The kidney α-SMA and MT stain area showed that the MR diet could improve renal fibrosis. The kidney inflammation including neutrophil and macrophage infiltration was also improved in histology analysis. The macrophage phenotype was more favorable to M2 type. Serum BUN and creatinine were significantly attenuated in the MR diet group. Conclusion In conclusion, the MR diet has a reno-protective effect in adenine induced CKD. The MR diet increased butyrate production and decreased renal inflammation and fibrosis. These results shed light on the role of protein restriction diet for CKD management in the real world.

1868-P: Implementation of Dietary Methionine Restriction Using Casein after Selective, Oxidative Deletion of Methionine

Restriction of methionine in rodent diets increases energy expenditure, limits weight gain, improves insulin sensitivity, and reduces hepatic and circulating lipids. Dietary methionine restriction (MR) is implemented using diets formulated from elemental amino acids (AA) that reduce methionine content to restricted levels of ∼0.17%. However, translational implementation of dietary MR with elemental AA-based diets is confounded by poor palatability. To solve this problem and restrict methionine using intact proteins, casein was subjected to mild oxidation to selectively reduce methionine. Diets were then formulated using oxidized casein, adding back methionine to produce a final concentration of 0.17%. The biological efficacy of dietary MR using the oxidized casein diet was compared to the standard elemental MR diet. Thirty-two, 5-week old male C57BL/6J mice were divided into two groups of 16, with one group receiving the Elemental Control (El Con) diet and the other receiving the Casein Control (Cas Con) diet for 10 days. Thereafter, 8 mice continued on the El Con diet and 8 mice were switched to the Elemental MR (El MR) diet. In similar fashion, 8 mice continued on the Cas Con diet and 8 mice were switched to the Oxidized Casein (Ox Cas) MR diet. Over the subsequent 8 weeks, the behavioral, metabolic, and endocrine responses to the 4 diets were assessed to evaluate the relative efficacy of the 2 approaches to restricting dietary methionine. The El MR diet produced the expected reductions in body weight, fat mass accumulation, fasting insulin, and hepatic and circulating triglycerides, while increasing energy expenditure, serum FGF-21 levels, and weight-specific food consumption. The Ox Cas MR diet produced increases and decreases in each of these variables that paralleled the effects of the El MR diet. Collectively, these findings demonstrate that dietary MR can be effectively implemented using casein after selective oxidative reduction of methionine. Disclosure H. Fang: None. K.P. Stone: None. L. Forney: None. L.C. Sims: None. T.W. Gettys: None. Funding Pennington Foundation

227-LB: Dietary Protein Restriction Induced–FGF21 Improves Metabolic Health during Aging

Aging and obesity are risk factors linked to the impairment of both energy and glucose homeostasis. Conversely, reducing caloric intake or the intake of select macronutrients or amino acids, including dietary protein restriction (DPR) and methionine restriction, defends against the detrimental effects of aging and obesity. Our data demonstrate that DPR increases energy expenditure and improves glucose homeostasis, and that the metabolic hormone FGF-21 coordinates these adaptive responses to protein restriction in young mice. However, the role of FGF-21 in mediating the effects of DPR during aging remains unclear. C57BL6 mice were fed either a normal protein (NP) or a low protein diet (LP), beginning at either young (3-months) or middle (12-months) age. A separate group of middle-aged mice were fed either a high-fat (HFD) diet or a high-fat, low-protein (HFLP) diet. Bodyweight and food intake were assessed weekly in all groups. Energy expenditure and glucose tolerance were assessed at 12 and 20 months of age in young mice and 16 months of age in middle aged-mice. Serum collected at sacrifice was used to measure FGF-21 levels. LP diet increased energy expenditure and food intake, and reduced body weight gain, in both young and middle-aged mice (P<0.05), and HFLP-diet similarly reduced body weight gain relative to HFD-fed controls (P<0.05). Glucose tolerance was improved in LP-fed young mice, and in LP and HFLP fed middle-aged mice (P<0.05). Lastly, FGF-21 levels were increased in both young and middle-aged mice in response to LP-diet (P<0.05), and in response to HFLP in middle-aged mice (P<0.05). These data indicate that the interaction of age or diet-induced obesity does not blunt the effects of DPR to induce-FGF-21, reduce body weight gain, increase energy expenditure, or improve glucose homeostasis. Disclosure C.M. Hill: None. D. McDougal: None. C. Morrison: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK105032, F32DK115137); Pennington Biomedical/Louisiana Nutrition Obesity Center (P30DK072476)

Mechanisms of Action of Methionine Restriction and Fibroblast Growth Factor 21 (FGF21)

Abstract Objectives Many of the metabolic benefits of methionine restriction (MR) are mediated by FGF21. MR activates protein kinase R-like ER kinase (PERK) and nuclear respiratory factor 2 (NRF2) signaling pathways, which have also been tied to FGF21 production. Aim 1 is to elucidate the mechanism by which MR increases hepatic FGF21 production. FGF21 signaling in the brain is required for its metabolic effects. However, the neuronal circuits and mechanisms mediating FGF21’s metabolic effects remain unclear. Aim 2 is to determine the effects of FGF21 on neurons in the paraventricular nucleus (PVN). Methods Aim 1: HepG2 cells were treated with vehicle or NRF2 inhibitor (brusatol; 80 nM) for 4 h or PERK inhibitor (GSK2606414; 1 µM) for 2 h. Cells were then incubated in control or MR media for 16 h. FGF21 mRNA expression was measured. Aim 2: WT and Fgf21−/− mice were fed high-fat control or MR diets for 14 wk. 4 mice per group were perfused with formalin for immunohistochemistry. Patch-clamp study: Sympathetic, PVN neurons projecting to the rostral ventrolateral medulla were retrogradely-labeled and subsequently patched in acute hypothalamic slices and treated with vehicle or the FGF21 analog, LY2405319 (LY; 500 nM). Firing activity of PVN-RVLM neurons and the activity of GABAergic inhibitory inputs to these neurons were measured. Results Aim 1: MR increased FGF21 mRNA in HepG2 cells by 18-fold on average (P = 0.02). The ability of MR to increase FGF21 is abolished when cells are treated with the NRF2 inhibitor but is not affected by PERK inhibition. Aim 2: MR increased ERK phosphorylation in the PVN of WT, but not Fgf21−/− mice. LY either increased (33% of recorded neurons) or decreased (67% of recorded neurons) the firing activity of PVN-RVLM neurons suggesting that FGF21 effects may depend on their projecting targets. LY inhibited the frequency of GABA inhibitory postsynaptic current (IPSC) (42.02% decrease, P < 0.05). Conclusions In vitro analysis suggests that the ability of MR to increase FGF21 expression is dependent upon NRF2 activity, but independent of PERK. Our data support the hypothesis that FGF21 signals through the PVN modulating sympathetic-related PVN neuronal activity to produce its metabolic benefits. Funding Sources GSU Research Initiation Grant; Center for Neuroinflammation and Cardiometabolic Diseases (CNCD), GSU.

Weight Loss and Concomitant Adipose Autophagy in Methionine-Restricted Obese Mice is Not Dependent on Adiponectin or FGF21.

Identifying novel approaches to combat obesity is important to improve health span. It was hypothesized that methionine restriction (MR) will induce weight loss in obese mice by reducing adipose tissue mass caused by increased energy expenditure and reprogramming of adipose tissue homeostasis. The roles of adiponectin (ADIPOQ) and fibroblast growth factor 21 (FGF21) during weight loss in MR mice were also tested. Diet-induced obese (DIO) male C57BL/6J (wild type), Adipoq-deficient (Adipoqknockout [KO]), Fgf21-KO, and Adipoq-Fgf21 double-KO mice were used. Following a switch to high-fat control (DIO-CF, 60% fat/0.86% methionine) or MR (DIO-MR, 60% fat/0.12% methionine) diet, physiological parameters were measured, and inguinal and perigonadal adipose tissues were examined. Obese mice subjected to MR showed loss of body weight and adiposity, increased energy expenditure, and improved glucose tolerance that were independent of the actions of ADIPOQ and FGF21. MR induced reduction of circulating lipids, glucose, insulin, leptin, and insulin like growth factor 1 and increased β-hydroxybutyrate, ADIPOQ, and FGF21 concentrations. In fat, MR upregulated protein levels of adipose triglyceride lipase, apoptosis-inducing factor, lysosomal-associated membrane proteins 1 and 2, autophagy-related protein 5, beclin-1, and light chain 3B I and II. MR reduction of adipose tissue mass in obese mice is associated with elevated lipolysis, apoptosis, and autophagy and occurs independently of the actions of ADIPOQ and FGF21.

Understanding the Mechanism of Fibroblast Growth Factor 21 Action in the Paraventricular Nucleus of the Hypothalamus: A Promising Candidate in the Treatment of Obesity and Metabolic Diseases

Fibroblast Growth Factor 21 (FGF21), when administered pharmacologically reduces body weight, increases insulin sensitivity and energy expenditure, and induces browning of white adipose tissue (WAT). Research has shown that FGF21 signaling in the brain is required for the induction of these metabolic benefits, with the paraventricular nucleus of the hypothalamus (PVN) as a potential primary site of action. However, the neuronal circuits and precise mechanisms mediating FGF21’s metabolic effects remain incompletely understood. Further, the role of the sympathetic nervous system (SNS) in this process remains unclear. Here, we aimed to address these questions using dietary methionine restriction (MR) as a tool to stimulate endogenous FGF21 production in WT and FGF21 KO mice fed a control or a high‐fat diet. Dietary MR rapidly and persistently increases serum FGF21 concentration by up to 8‐fold (p<0.0001). We found that in WT mice, MR increased energy expenditure and thermogenic markers in iWAT and BAT, an indication of increased SNS output to these tissues in WT, but not FGF21 KO mice. Additionally, we observed increased ERK phosphorylation in the PVN of the WT but not FGF21 KO mice, supporting PVN neurons as a likely target mediating FGF21 actions. To further investigate the role of FGF21 in the PVN, we used whole‐cell patch clamp recordings in retrogradely‐labelled presympathetic PVN neurons projecting to the rostral ventrolateral medulla (RVLM), and measured the effects of the FGF21 analog LY2405319 (500nM) on the firing activity of PVN‐RVLM neurons. Recordings in current‐clamp mode showed that FGF21 either increased (33% of recorded neurons) or decreased (67% of recorded neurons) the firing activity of these neurons suggesting that FGF21 effects may depend on their projecting targets. Recordings in voltage‐clamp mode also showed that FGF21 significantly decreased the degree of activity of GABAergic inhibitory inputs into these neurons. Thus, LY2405319 inhibited the frequency of GABA inhibitory postsynaptic current (IPSC) (42.02% decrease, p< 0.05), suggesting that FGF21 effects on presympathetic neurons in the PVN could be mediated by direct and/or indirect actions, including modulation of local network activity, such as local GABAergic interneurons. Taken together, our data support the hypothesis that FGF21 signals through PVN neurons to increase SNS output to adipose tissue, resulting in increased energy expenditure, reduced body weight, and improved insulin sensitivity.

The Spectrum of Mutations of Homocystinuria in the MENA Region

Homocystinuria is an inborn error of metabolism due to the deficiency in cystathionine beta-synthase (CBS) enzyme activity. It leads to the elevation of both homocysteine and methionine levels in the blood and urine. Consequently, this build-up could lead to several complications such as nearsightedness, dislocated eye lenses, a variety of psychiatric and behavioral disorders, as well as vascular system complications. The prevalence of homocystinuria is around 1/200,000 births worldwide. However, its prevalence in the Gulf region, notably Qatar, is exceptionally high and reached 1:1800. To date, more than 191 pathogenic CBS mutations have been documented. The majority of these mutations were identified in Caucasians of European ancestry, whereas only a few mutations from African-Americans or Asians were reported. Approximately 87% of all CBS mutations are missense and do not target the CBS catalytic site, but rather result in unstable misfolded proteins lacking the normal biological function, designating them for degradation. The early detection of homocystinuria along with low protein and methionine-restricted diet is the best treatment approach for all types of homocystinuria patients. Yet, less than 50% of affected individuals show a significant reduction in plasma homocysteine levels after treatment. Patients who fail to lower the elevated homocysteine levels, through high protein-restricted diet or by B6 and folic acid supplements, are at higher risk for cardiovascular diseases, neurodegenerative diseases, neural tube defects, and other severe clinical complications. This review aims to examine the mutations spectrum of the CBS gene, the disease management, as well as the current and potential treatment approaches with a greater emphasis on studies reported in the Middle East and North Africa (MENA) region.

Disruption of hepatic one-carbon metabolism impairs mitochondrial function and enhances macrophage activity in methionine–choline-deficient mice

One-carbon metabolism is a collection of metabolic cycles that supports methylation and provides one-carbon bound folates for the de novo synthesis of purine and thymidine nucleotides. The methylation of phosphatidylethanolamine to form choline has been extensively studied in the context of fatty liver disease. However, the role of one-carbon metabolism in supporting nucleotide synthesis during liver damage has not been addressed. The objective of this study is to determine how the disruption of one-carbon metabolism influences nucleotide metabolism in the liver after dietary methionine and choline restriction. Mice (n=8) were fed a methionine–choline-deficient or control diet for 3 weeks. We treated mice with the compound alloxazine (0.5 mg/kg), a known adenosine receptor antagonist, every second day during the final week of feeding to probe the function of adenosine signaling during liver damage. We found that concentrations of several hepatic nucleotides were significantly lower in methionine- and choline-deficient mice vs. controls (adenine: 13.9±0.7 vs. 10.1±0.6, guanine: 1.8±0.1 vs. 1.4±0.1, thymidine: 0.0122±0.0027 vs. 0.0059±0.0027 nmol/mg dry tissue). Treatment of alloxazine caused a specific decrease in thymidine nucleotides, decrease in mitochondrial content in the liver and exacerbation of steatohepatitis as shown by the increased hepatic lipid content and altered macrophage morphology. This study demonstrates a role for one-carbon metabolism in supporting de novo nucleotide synthesis and mitochondrial function during liver damage.

Sex-Specific Effects of Dietary Methionine Restriction on the Intestinal Microbiome

Dietary methionine restriction is associated with improved health outcomes and an increase in lifespan in animal models. We have previously shown that an increase in dietary methionine induces alteration in the intestinal microbiome. The composition of the intestinal microbiota is a determinant of health and we, therefore, hypothesized that dietary methionine restriction would also induce changes in the murine microbiome. After one month on a methionine-restricted diet, five-month-old male and female C57BL/6 mice had decreased levels of serum methionine, without changes in body weight. We identified a decrease in the hepatic methylation status of animals fed a methionine-restricted diet compared to controls. This decrease was not associated with changes in DNA or protein methylation in the liver. In males, we saw an increase in families Bacteroidaceae and Verrucoccaceae (mostly A. mucinophila) and a decrease in Rumminococcaceae in animals fed a methionine-restricted diet compared to controls. In females, Bacteroidales family S24-7 was increased two-fold, while families Bacteroidaceae, Verrucoccaceae, Rumminococcaceae, and Rikenellaceae were decreased compared to controls. In summary, feeding a methionine-restricted diet for one month was associated with significant and sex-specific changes in the intestinal microbiome.

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

BackgroundDietary 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.MethodsTwenty 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.ResultsPlasma 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.ConclusionsOur 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.

Sexually Dimorphic Effects of Dietary Methionine Restriction are Dependent on Age when the Diet is Introduced.

Restricting dietary methionine to 0.17% in male mice increases energy expenditure, reduces fat deposition, and improves metabolic health. The goal of this work was to compare each of these responses in postweaning male and female mice and in physically mature male and female mice. Methionine-restricted(MR) diets were fed to age-matched cohorts of male and female mice for 8 to 10 weeks beginning at 8 weeks of age or beginning at 4 months of age. The physiological and transcriptional responses to MR were compared in the respective cohorts. Dietary MR produced sexually dimorphic changes in body composition in young growing animals, with males preserving lean at the expense of fat and females preserving fat at the expense of lean. The effects of MR on energy balance were comparable between sexes when the diet was initiated after attainment of physical maturity (4 months), and metabolic and endocrine responses were also comparable between males and females after 8 weeks on the MR diet. The sexually dimorphic effects of MR are limited to nutrient partitioning between lean and fat tissue deposition in young, growing mice. Introduction of the diet after physical maturity produced comparable effects on growth and metabolic responses in male and female mice.

Methionine Metabolism Shapes T Helper Cell Responses through Regulation of Epigenetic Reprogramming

Epigenetic modifications on DNA and histones regulate gene expression by modulating chromatin accessibility to transcription machinery. Here we identify methionine as a key nutrient affecting epigenetic reprogramming in CD4+ T helper (Th) cells. Using metabolomics, we showed that methionine is rapidly taken up by activated Tcells and serves as the major substrate for biosynthesis of the universal methyl donor S-adenosyl-L-methionine (SAM). Methionine was required to maintain intracellular SAM pools in Tcells. Methionine restriction reduced histone H3K4 methylation (H3K4me3) at the promoter regions of key genes involved in Th17 cell proliferation and cytokine production. Applied to the mouse model of multiple sclerosis (experimental autoimmune encephalomyelitis), dietary methionine restriction reduced the expansion of pathogenic Th17 cells invivo, leading to reduced Tcell-mediated neuroinflammation and disease onset. Our data identify methionine as a key nutritional factor shaping Th cell proliferation and function in part through regulation of histone methylation.

Modulation of sulfur assimilation metabolic toxicity overcomes anemia and hemochromatosis in mice.

Sulfur assimilation is an essential metabolic pathway that regulates sulfation, amino acid metabolism, nucleotide hydrolysis, and organismal homeostasis. We recently reported that mice lacking bisphosphate 3'-nucleotidase (BPNT1), a key regulator of sulfur assimilation, develop iron-deficiency anemia (IDA) and anasarca. Here we demonstrate two approaches that successfully reduce metabolic toxicity caused by loss of BPNT1: 1) dietary methionine restriction and 2) overproduction of a key transcriptional regulator hypoxia inducible factor 2α (Hif-2a). Reduction of methionine in the diet reverses IDA in mice lacking BPNT1, through a mechanism of downregulation of sulfur assimilation metabolic toxicity. Gaining Hif-2a acts through a different mechanism by restoring iron homeostatic gene expression in BPNT1 deficient mouse intestinal organoids. Finally, as loss of BPNT1 impairs expression of known genetic modifiers of iron-overload, we demonstrate that intestinal-epithelium specific loss of BPNT1 attenuates hepatic iron accumulation in mice with homozygous C282Y mutations in homeostatic iron regulator (HFEC282Y), the most common cause of hemochromatosis in humans. Overall, our study uncovers genetic and dietary strategies to overcome anemia caused by defects in sulfur assimilation and identifies BPNT1 as a potential target for the treatment of hemochromatosis.