Dietary Methionine Restriction Research Articles

Effect of different levels of dietary methionine restriction on relieving oxidative stress and behavioral deficits in middle-aged mice fed low-, medium-, or high-fat diet

• MR attenuated behavioral deficits in a dose-dependent manner in middle-aged mice. • The benefits of regulating oxidative stress and improving behavioral deficits of 60% MR (MR60) were more evident in high-fat-diet mice than those in low- or medium-fat-diet mice. • The mechanism of MR may be associated with an improvement of thyroid function. Dietary methionine restriction (MR) could prevent age-related diseases and extend lifespan. The present study compared the effects of different levels of MR on oxidative stress and behavioral deficits in middle-aged mice fed a diet with various contents of fat. C57BL/6J middle-aged male mice were divided into nine groups with various combinations of dietary fat (low, medium, and high) and MR (0%, 60%, and 80%). MR attenuated dietary fat-induced oxidative stress and anxiety; improved athletic ability, learning, memory, and cognitive ability in conjunction with an improved thyroid function in a dose-dependent manner. Moreover, the beneficial effect of MR60 was prominent in middle-aged mice fed a HF diet relative to the corresponding MR0 group. These results provide more information on the appropriate methionine content to design personalized nutritional diets.

Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence

CBS deficient individuals undergoing betaine supplementation without sufficient dietary methionine restriction can develop severe hypermethioninemia and brain edema. Brain edema has also been observed in individuals with severe hypermethioninemia without concomitant betaine supplementation. We systematically evaluated reports from 11 published and 4 unpublished patients with CBS deficiency and from additional four cases of encephalopathy in association with elevated methionine. We conclude that, while betaine supplementation does greatly exacerbate methionine accumulation, the primary agent causing brain edema is methionine rather than betaine. Clinical signs of increased intracranial pressure have not been seen in patients with plasma methionine levels below 559 μmol/L but occurred in one patient whose levels did not knowingly exceed 972 μmol/L at the time of manifestation. While levels below 500 μmol/L can be deemed safe it appears that brain edema can develop with plasma methionine levels close to 1000 μmol/L. Patients with CBS deficiency on betaine supplementation need to be regularly monitored for concordance with their dietary plan and for plasma methionine concentrations. Recurrent methionine levels above 500 μmol/L should alert clinicians to check for clinical signs and symptoms of brain edema and review dietary methionine intake. Levels approaching 1000 μmol/L do increase the risk of complications and levels exceeding 1000 μmol/L, despite best dietetic efforts, should be acutely addressed by reducing the prescribed betaine dose.

Oral Recombinant Methioninase Prevents Obesity in Mice on a High-fat Diet.

obesity is a world-wide recalcitrant problem leading to many diseases. Dietary methionine restriction (MR) has been shown to prevent obesity, but it is an onerous regimen. The present study aimed to determine the effects of oral recombinant methionase (o-rMETase), on preventing obesity in mice on a high-fat diet. Male C57BL/6J mice in the control group were fed a control diet (CD) (+6.5% fat) for 25 days, and others were fed a high-fat (HF) diet (+34.3% fat) for 25 days. Then, the mice were divided into three dietary groups: 1) HF + phosphate buffered saline (PBS) group; 2) HF + o-rMETase group; and 3) untreated non-HF group. The mice on the CD increased in body weight by 14% during experimental period of 25 days; in contrast the mice in the HF+PBS group increased by 33%; however, the mice on the HF+o-rMETase group increased only by 14% (p=0.02, HF+PBS vs HF+o-rMETase). The HF+ o-rMETase group had the same weight increase as untreated mice on a normal fat diet, demonstrating the potential for o-rMETase to eliminate the need for dieting to maintain normal body weight.

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.

FGF21, not GCN2, influences bone morphology due to dietary protein restrictions

BackgroundDietary protein restriction is emerging as an alternative approach to treat obesity and glucose intolerance because it markedly increases plasma fibroblast growth factor 21 (FGF21) concentrations. Similarly, dietary restriction of methionine is known to mimic metabolic effects of energy and protein restriction with FGF21 as a required mechanism. However, dietary protein has been shown to be required for normal bone growth, though there is conflicting evidence as to the influence of dietary protein restriction on bone remodeling. The purpose of the current study was to evaluate the effect of dietary protein and methionine restriction on bone in lean and obese mice, and clarify whether FGF21 and general control nonderepressible 2 (GCN2) kinase, that are part of a novel endocrine pathway implicated in the detection of protein restriction, influence the effect of dietary protein restriction on bone. MethodsAdult wild-type (WT) or Fgf21 KO mice were fed a normal protein (18 kcal%; CON) or low protein (4 kcal%; LP) diet for 2 or 27 weeks. In addition, adult WT or Gcn2 KO mice were fed a CON or LP diet for 27 weeks. Young New Zealand obese (NZO) mice were placed on high-fat diets that provided protein at control (16 kcal%; CON), low levels (4 kcal%) in a high-carbohydrate (LP/HC) or high-fat (LP/HF) regimen, or on high-fat diets (protein, 16 kcal%) that provided methionine at control (0.86%; CON-MR) or low levels (0.17%; MR) for up to 9 weeks. Long bones from the hind limbs of these mice were collected and evaluated with micro-computed tomography (μCT) for changes in trabecular and cortical architecture and mass. ResultsIn WT mice the 27-week LP diet significantly reduced cortical bone, and this effect was enhanced by deletion of Fgf21 but not Gcn2. This decrease in bone did not appear after 2 weeks on the LP diet. In addition, Fgf21 KO mice had significantly less bone than their WT counterparts. In obese NZO mice dietary protein and methionine restriction altered bone architecture. The changes were mediated by FGF21 due to methionine restriction in the presence of cystine, which did not increase plasma FGF21 levels and did not affect bone architecture. ConclusionsThis study provides direct evidence of a reduction in bone following long-term dietary protein restriction in a mouse model, effects that appear to be mediated by FGF21.

Extension of Cellular Lifespan by Methionine Restriction Involves Alterations in Central Carbon Metabolism and Is Mitophagy-Dependent.

Methionine restriction (MR) is one of only a few dietary manipulations known to robustly extend healthspan in mammals. For example, rodents fed a methionine-restricted diet are up to 45% longer-lived than control-fed animals. Tantalizingly, ongoing studies suggest that humans could enjoy similar benefits from this intervention. While the benefits of MR are likely due, at least in part, to improved cellular stress tolerance, it remains to be determined exactly how MR extends organismal healthspan. In previous work, we made use of the yeast chronological lifespan (CLS) assay to model the extension of cellular lifespan conferred by MR and explore the genetic requirements for this extension. In these studies, we demonstrated that both dietary MR (D-MR) and genetic MR (G-MR) (i.e., impairment of the cell’s methionine biosynthetic machinery) significantly extend the CLS of yeast. This extension was found to require the mitochondria-to-nucleus retrograde (RTG) stress signaling pathway, and was associated with a multitude of gene expression changes, a significant proportion of which was also dependent on RTG signaling. Here, we show work aimed at understanding how a subset of the observed expression changes are causally related to MR-dependent CLS extension. Specifically, we find that multiple autophagy-related genes are upregulated by MR, likely resulting in an increased autophagic capacity. Consistent with activated autophagy being important for the benefits of MR, we also find that loss of any of several core autophagy factors abrogates the extended CLS observed for methionine-restricted cells. In addition, epistasis analyses provide further evidence that autophagy activation underlies the benefits of MR to yeast. Strikingly, of the many types of selective autophagy known, our data clearly demonstrate that MR-mediated CLS extension requires only the autophagic recycling of mitochondria (i.e., mitophagy). Indeed, we find that functional mitochondria are required for the full benefit of MR to CLS. Finally, we observe substantial alterations in carbon metabolism for cells undergoing MR, and provide evidence that such changes are directly responsible for the extended lifespan of methionine-restricted yeast. In total, our data indicate that MR produces changes in carbon metabolism that, together with the oxidative metabolism of mitochondria, result in extended cellular lifespan.

Methionine restriction delays aging-related urogenital diseases in male Fischer 344 rats.

Dietary methionine restriction (MR) has been found to enhance longevity across many species. We hypothesized that MR might enhance longevity in part by delaying or inhibiting age-related disease processes. To this end, male Fischer 344 rats were fed control (CF, 0.86% methionine) or MR (0.17% methionine) diets throughout their life until sacrifice at approximately 30 months of age, and histopathology was performed to identify the incidence and progression of two important aging-related pathologies, namely, chronic progressive nephropathy (CPN) and testicular tumorigenesis. Although kidney pathology was observed in 87% CF rats and CPN in 62% of CF animals, no evidence of kidney disease was observed in MR rats. Consistent with the absence of renal pathology, urinary albumin levels were lower in the MR group compared to controls throughout the study, with over a six-fold difference between the groups at 30 months of age. Biomarkers associated with renal disease, namely, clusterin, cystatin C, and β-2 microglobulin, were reduced following 18 months of MR. A reduction in testicular tumor incidence from 88% in CF to 22% in MR rats was also observed. These results suggest that MR may lead to metabolic and cellular changes providing protection against age-related diseases.

METABOLIC CONSEQUENCES OF METHIONINE REDOX IN METHIONINE RESTRICTION

While caloric restriction (CR) provides highly robust improvements to longevity and health, dietary restriction of the essential amino acid methionine can provide similar benefits including improved metabolic function and increased longevity. Despite these similarities between CR and methionine restriction (MR), there is growing evidence to suggest they may be mediated by different mechanisms that require further elucidation. The sulfur side-chain of methionine is highly prone to oxidation, even in vivo, with redox changes of these residues potentially altering protein function and interfering with its use as a substrate. An entire family of enzymes, methionine sulfoxide reductases, have evolved in aerobic organisms to regulate the redox status of methionine. We tested the role of methionine sulfoxide reductase A (MsrA) in the physiological and metabolic benefits of MR. After three months of MR, mice lacking MsrA (MsrA KO) showed significant loss of weight, including both fat and lean mass, in comparison to wild-type mice under MR. Both MsrA KO and wild-type mice responded to MR with improvements to both glucose and insulin tolerance. However, MR MsrA KO mice showed lower HbA1c and reduced leptin compared to MR wild-type mice. Overall, our results show mice lacking MsrA have a stronger response to MR suggesting that methionine redox may play an important role in some of the mechanisms responsible for these metabolic outcomes. Further studies clarify whether MsrA could also be a potential regulator of the longevity benefits of MR.

NOVEL METHIONINE-RELATED INTERVENTIONS THAT CONFER HEALTHSPAN BENEFITS TO YEAST AND RODENTS

Methionine restriction (MR) is one of only a few dietary manipulations known to robustly extend healthspan in mammals. Methionine-restricted rodents are up to 45% longer-lived than control-fed littermates and a number of studies suggest that humans may also benefit from MR. While a methionine-restricted human diet is technically feasible, compliance to such a regimen might not be practical or desirable. Therefore, an important goal is to identify and/or develop more facile dietary interventions, or preferably, pharmacological agents that mimic MR. Towards this end, we have made use of the yeast chronological lifespan and replicative lifespan assays, which serve as models of aging in quiescent and mitotic cells, respectively. Importantly, our lab and others have demonstrated that MR dramatically extends yeast lifespan. Here we show work aimed at developing novel MR-like interventions that extend yeast lifespan, as well as preliminary data demonstrating that such interventions significantly improve the healthspan of mice.

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 21days were randomly allotted to two treatments and fed either a methionine-restricted diet (0.25% methionine) or a control diet (0.48% methionine) for 4weeks. 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.

The effect of short-term methionine restriction on glutathione synthetic capacity and antioxidant responses at the whole tissue and mitochondrial level in the rat liver.

Dietary methionine restriction (MR) where methionine is the sole source of sulfur amino acid increases lifespan in diverse species. Methionine restricted rodents experience a decrease in glutathione (GSH), a major antioxidant, in several tissues, which is paradoxical to longevity interventions because tissues with low GSH might experience more oxidative damage. Liver plays a key role in GSH synthesis and here we examined how MR influences GSH metabolism in the liver. We also hypothesised that low GSH might be subsidized by compensatory pathway(s) in the liver. To investigate GSH synthesis and antioxidant responses, Fischer-344 rats were given either a MR diet or a control diet for 8 weeks. Based on γ-glutamylcysteine synthetase activity, GSH synthetic capacity did not respond to low dietary methionine availability. Tissue level protein and lipid oxidation markers do not support elevated oxidative damage, despite low GSH availability. Whole tissue and mitochondrial level responses to MR differed. Specifically, the activity of glutathione reductase and thioredoxin reductase increase in whole liver tissue which might offset the effects of declined GSH availability whereas mitochondrial GSH levels were unperturbed by MR. Moreover, enhanced proton leak in liver mitochondria by MR (4 week) presumably diminishes ROS production. Taken together, we suggest that the effect of low GSH in liver tissue is subsidized, at least in part, by increased antioxidant activity and possibly by enhanced mitochondrial proton leak.

Behavior, body composition, and vascular phenotype of homocystinuric mice on methionine-restricted diet or enzyme replacement therapy.

Classic homocystinuria (HCU) is an inherited disorder characterized by elevated homocysteine (Hcy) in plasma and tissues resulting from cystathionine β-synthase (CBS) deficiency. There is no cure, and patients are predominantly managed by methionine-restricted diet (MRD) to limit the production of Hcy. In this study, we used the I278T mouse model of HCU to evaluate the long-term impact of a novel enzyme replacement therapy [truncated human CBS C15S mutant modified with linear 20-kDa N-hydroxysuccinimide ester polyethylene glycol (OT-58)] on clinical end points relevant to human patients with HCU. In addition, we compared its efficacy on a background of either MRD or normal methionine intake [regular diet (REG)] to that of MRD alone. We found that, compared with untreated I278T mice, OT-58 treatment of I278T mice fed with the REG diet resulted in a 90% decrease in plasma Hcy concentrations and correction of learning/cognition, endothelial dysfunction, hemostasis, bone mineralization, and body composition. On background of the MRD, OT-58 performed equally well with plasma Hcy entirely normalized. The MRD alone decreased plasma Hcy by 67% and corrected the HCU phenotype in I278T mice. However, the MRD increased anxiety and reduced bone mineral content in both I278T mice and wild-type controls. This study shows that OT-58 is a highly efficacious novel treatment for HCU on the background of either normal or restricted methionine intake.-Majtan, T., Park, I., Cox, A., Branchford, B. R., di Paola, J., Bublil, E. M., Kraus, J. P. Behavior, body composition, and vascular phenotype of homocystinuric mice on methionine-restricted diet or enzyme replacement therapy.

Dietary methionine links nutrition and metabolism to the efficacy of cancer therapies

Nutrition exerts profound effects on health and dietary interventions are commonly used to treat diseases of metabolic etiology. Although cancer has a substantial metabolic component1, the principles that define whether nutrition may be used to influence tumour outcome are unclear2. Nevertheless, it is established that targeting metabolic pathways with pharmacological agents or radiation can sometimes lead to controlled therapeutic outcomes. In contrast, whether specific dietary interventions could influence the metabolic pathways that are targeted in standard cancer therapies is not known. We now show that dietary restriction of methionine (MR), an essential amino acid, and the reduction of which has anti-aging and anti-obesogenic properties, influences cancer outcome through controlled and reproducible changes to one-carbon metabolism. This pathway metabolizes methionine and further is the target of a host of cancer interventions involving chemotherapy and radiation. MR produced therapeutic responses in chemoresistant RAS-driven colorectal cancer patient derived xenografts (PDXs) and autochthonous KRASG12D+/−;TP53−/− -driven soft tissue sarcomas resistant to radiation. Metabolomics revealed the therapeutic mechanisms to occur through tumour cell autonomous effects on the flux through one-carbon metabolism that impacted redox and nucleotide metabolism, thus interacting with the antimetabolite or radiation intervention. Finally, in a controlled and tolerated feeding study in humans, MR resulted in similar effects on systemic metabolism as obtained in responsive mice. These findings provide evidence that a targeted dietary manipulation can affect specific tumour cell metabolism to mediate broad aspects of cancer outcome.

Abstract 1611: Caloric restriction potentiates the therapeutic benefit of androgen deprivation therapy and alters macrophage polarization when combined with PD1 inhibition in murine models of prostate cancer

Abstract Background: Data from epidemiological studies have linked dietary intake to the development of prostate cancer (CaP). We have previously shown that dietary protein restriction inhibits tumor growth by modulating PI3K/mTOR signaling in vivo. Additionally we have shown that dietary methionine restriction influence macrophage polarization which enhances the ability of the immune system to fight cancer. In this study we hypothesize that caloric restriction is capable of restricting tumor growth and potentiating the antitumor effect of androgen deprivation therapy (ADT) and PD1 inhibition. Methods: We utilized two prostate cancer models for our in vivo studies; castrate resistant LuCaP 23.1 AI prostate cancer model and MYC-Driven prostate cancer model in C57BL/6 mice. Caloric restriction was carried out by exposing mice to alternating fasting either as a single intervention (in LuCaP 23.1 model) or in combination with ADT (enzalutamide or surgical castration) or PD-1 inhibition in Myc-CaP model. Tumor sizes and weights were blindly assessed during the study and upon study termination respectively. IHC staining for both Ki-67 and mTOR phosphorylation was done to assess the impact of fasting+/- ADT on tumor growth and mTOR signaling. Macrophage polarization/distribution in tumors was assessed using immunofluorescence. Blood was collected at the end of the study for future comprehensive analysis of PBMCS. Results: In both models, alternating fasting was associated with significant decrease in tumor weight at the end of study in comparison to control group (*p<0.05). In Myc-CaP model, tumor weight was significantly decreased in combined fasting and enzalutamide/castration group in comparison to the control condition (**p<0.001) but was not significantly better than either intervention alone. Similarly, fasting potentiated the therapeutic benefit of PD-1 inhibition yet it was not significant. Combined fasting and ADT was associated with significant reduction in Ki-67 nuclear expression (****p<0.0001), however it was not significantly less than either agent alone. Combined fasting and ADT was associated with significant decrease in P-mTOR expression in comparison to control mice (****p<0.0001). Although we did not observe significant change in tumor weight with combined fasting and PD-1 inhibition; fasting potentiated the influence of PD-1 on macrophage polarization. M2 macrophages were significantly less in combined treatment compared to either single intervention alone (**p<0.01). Conclusions: Caloric restriction can hinder prostate cancer growth and potentiate the therapeutic effect of ADT. Our results provide basis for the translational use of dietary modification both as preventive measure as well as a therapeutic intervention that can improve the benefit of current standard treatments. Citation Format: May Elbanna, Justin Budka, Paige Dausinas, Remi Adelaiye-Ogala, Nur Damayanti, Ashley Orillion, Eri Banno, Luigi Fontana, Roberto Pili. Caloric restriction potentiates the therapeutic benefit of androgen deprivation therapy and alters macrophage polarization when combined with PD1 inhibition in murine models of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1611.

Dietary Methionine Restriction Reduces Inflammation Independent of FGF21 Action.

Methionine restriction (MR) decreases inflammation and improves markers of metabolic disease in rodents. MR also increases hepatic and circulating concentrations of fibroblast growth factor 21 (FGF21). Emerging evidence has suggested that FGF21 exerts anti-inflammatory effects. The purpose of this study was to determine the role of FGF21 in mediating the MR-induced reduction in inflammation. Wild-type and Fgf21-/- mice were fed a high-fat (HF) control or HF-MR diet for 8 weeks. In a separate experiment, mice were fed a HF diet (HFD) for 10 weeks. Vehicle or recombinant FGF21 (13.6 µg/d) was administered via osmotic minipump for an additional 2 weeks. Inflammation and metabolic parameters were measured. Fgf21-/- mice were more susceptible to HFD-induced inflammation, and MR reduced inflammation in white adipose tissue (WAT) and liver of Fgf21-/- mice. MR downregulated activity of signal transducer and activator of transcription 3 in WAT of both genotypes. FGF21 administration reduced hepatic lipids and blood glucose concentrations. However, there was little effect of FGF21 on inflammatory gene expression in liver or adipose tissue or circulating cytokines. MR reduces inflammation independent of FGF21 action. Endogenous FGF21 is important to protect against the development of HFD-induced inflammation in liver and WAT, yet administration of low-dose FGF21 has little effect on markers of inflammation.

301-LB: Effects of Amino Acid Restriction on Development of Type 2 Diabetes in NZO Mice by FGF21 Secretion

Dietary protein restriction (PR) is emerging as an alternative approach to treat obesity and glucose intolerance since it increases plasma fibroblast growth factor 21 (FGF-21) levels. Also, dietary methionine restriction (MR) is known to mimic the metabolic effects of PR by increasing FGF-21 and inducing beneficial effects. Therefore, we tested in New Zealand Obese (NZO) mice, a model of polygenic obesity and type 2 diabetes, whether a moderate PR or a MR protects against diabetes. Moreover, we investigated whether a decreased methionine intake caused by vegetarian and vegan diets modulates plasma FGF-21 in humans. NZO mice were placed on high-fat diets that provided protein at control (18 gm%), low levels (4 gm%), or on high-fat diets (protein, 18 gm%) that provided methionine at control (0.86 gm%) or low levels (0.17 gm%) for up to 9 weeks. Changes in glucose homeostasis and energy expenditure were assessed. Among humans, plasma FGF-21 levels were investigated by comparing vegetarians and vegans to omnivores, and the effect of short-term vegetarian diet on FGF-21 induction was evaluated. PR prevented the onset of hyperglycemia only when protein was substituted by fat. When protein was substituted by carbohydrates, mice developed hyperglycemia two weeks later than the control, despite elevated plasma FGF-21 levels and increased energy expenditure. MR elevated plasma FGF-21 levels and prevented the onset of hyperglycemia. Human plasma FGF-21 levels were higher in vegans and vegetarians compared to omnivores. Interestingly, already a short-term switch to a vegetarian diet increased plasma FGF-21 in omnivores. Thus, restriction of dietary protein and methionine elevates plasma FGF-21 levels, which protect from hyperglycemia, an effect compromised by high dietary carbohydrates in NZO mice. Patients at high risk of developing type 2 diabetes may benefit from dietary changes in favor of methionine restriction, via increased circulating levels of FGF-21, without protein and calorie restriction. Disclosure T. Castaño-Martinez: None. W. Jonas: None. D. Weber: None. C. Weikert: None. T. Laeger: None. Funding Deutsche Forschungsgemeinschaft

Methionine Restriction Alleviates Aging-related Cognitive Dysfunction via Stimulating FGF21-driven Mitochondrial Biogenesis (P14-026-19)

ObjectivesModerate dietary methionine restriction (MR) extends life span in various animal models and delays the onset of aging-associated pathologies. However, the neuroprotective effects and underlying mechanism of MR on age and age-related diseases still remain to be investigated. Notably, fibroblast growth factor-21 (FGF21), a MR responding hormone mostly generated from liver, plays a critical role in neuronal mitochondrial function. Here, we aimed to reveal the neuroprotective effects of MR and the mediating role of FGF21 in aging mice model. MethodsMale C57BL/6 mice (2-, 12-, and 15- month-old) were treated with control methionine diet (0.86% methionine) and methionine restriction diet (0.17% methionine) for 3 months. Adeno-associated virus was employed to build FGF21 knockdown mice model. Behavioral tests, synapse ultrastructure detection, and amino acid metabolomics were performed to evaluate cognitive function, neuron damage and signaling pathway activation. ResultsIn behavioral tests, we found that MR significantly improved aging-induced decreased in spatial memory and cognitive function. Meanwhile, MR ameliorated neuronal damage and synapses structure damages in aging mice hippocampus. Moreover, MR significantly improved the mRNA expression of mitochondrial biogenesis and dynamics related genes such as COX2/fis1/pink1/binp1/drp1 in aging mice brain. MR also altered plasma amino acid metabolic phenotype-related glutathione synthesis, energy metabolism, and nervous system function. Furthermore, we found that MR could significant increase FGF21 level in both liver and serum of aging mice. Knockdown of FGF21 dramatically diminished the benefits of MR on cognitive impairments. ConclusionsThese results showed that MR mitigated aging-induced memory impairment and synapses structure damages via activating FGF21 signaling pathway. The study suggest that this dietary restriction might be plausible therapeutic intervention for aging and other neurodegenerative diseases such AD and PD. Funding SourcesThis work was financially supported by the National Key Research and Development Program of China, National Natural Science Foundation of China. Supporting Tables, Images and/or Graphs▪

Methionine restriction prevents onset of type 2 diabetes in NZO mice

Dietary methionine restriction (MR) is well known to reduce body weight by increasing energy expenditure (EE) and insulin sensitivity. An elevated concentration of circulating fibroblast growth factor 21 (FGF21) has been implicated as a potential underlying mechanism. The aims of our study were to test whether dietary MR in the context of a high-fat regimen protects against type 2 diabetes in mice and to investigate whether vegan and vegetarian diets, which have naturally low methionine levels, modulate circulating FGF21 in humans. New Zealand obese (NZO) mice, a model for polygenic obesity and type 2 diabetes, were placed on isocaloric high-fat diets (protein, 16 kcal%; carbohydrate, 52 kcal%; fat, 32 kcal%) that provided methionine at control (Con; 0.86% methionine) or low levels (0.17%) for 9 wk. Markers of glucose homeostasis and insulin sensitivity were analyzed. Among humans, low methionine intake and circulating FGF21 levels were investigated by comparing a vegan and a vegetarian diet to an omnivore diet and evaluating the effect of a short-term vegetarian diet on FGF21 induction. In comparison with the Con group, MR led to elevated plasma FGF21 levels and prevented the onset of hyperglycemia in NZO mice. MR-fed mice exhibited increased insulin sensitivity, higher plasma adiponectin levels, increased EE, and up-regulated expression of thermogenic genes in subcutaneous white adipose tissue. Food intake and fat mass did not change. Plasma FGF21 levels were markedly higher in vegan humans compared with omnivores, and circulating FGF21 levels increased significantly in omnivores after 4 d on a vegetarian diet. These data suggest that MR induces FGF21 and protects NZO mice from high-fat diet–induced glucose intolerance and type 2 diabetes. The normoglycemic phenotype in vegans and vegetarians may be caused by induced FGF21. MR akin to vegan and vegetarian diets in humans may offer metabolic benefits via increased circulating levels of FGF21 and merits further investigation.—Castaño-Martinez, T., Schumacher, F., Schumacher, S., Kochlik, B., Weber, D., Grune, T., Biemann, R., McCann, A., Abraham, K., Weikert, C., Kleuser, B., Schürmann, A., Laeger, T. Methionine restriction prevents onset of type 2 diabetes in NZO mice.

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.

Methionine Restriction Diet Improves Metabolic Function in Obese C57BL/6 Female Mice via AMPK/SIRT1/PGC1α Pathway

Methionine restriction has been proven to reverse age and obesity related metabolic diseases. Basically, MR regulates energy homeostasis in the whole body contributing to enhanced insulin sensitivity and improved redox status. There is no studies until now that comprehensively focus on the impact of MR on reproduction performance. The aim of this work was to investigate the reproductive system response of female obese model toward MR and clarify the possible mechanism. Females C57BL/6 were subjected to control diet (CON, 0.86% methionine + 4% fat), High Fat Diet (HFD, 0.86% methionine + 20% fat), High fat methionine Restricted diet (MR, 0.17% methionine + 20% fat). HFD showed impaired reproduction performance characteristic by impaired conception ability and lactation difficulties. MR improved oxidative stress, metabolic parameters, mammary and ovarian morphology. MR enhanced ovulation, lactation, and especially regulated metabolism efficiency via AMPK/SIRT1/PGC1. This study is the first to suggest that MR can ameliorate reproductive disorders induced by obesity.