Yu and Richardson et al. find that restriction of dietary isoleucine or valine promotes metabolic health in mice and that restriction of dietary isoleucine is required for the metabolic benefits of a low-protein diet. Furthermore, higher dietary isoleucine levels are associated with increased BMI in humans.

Obesity and diabetes are major challenges to global health, and there is an urgent need for interventions that promote weight loss. Dietary restriction of methionine promotes leanness and improves metabolic health in mice and humans. However, poor long-term adherence to this diet limits its translational potential. In this study, we develop a short-term methionine deprivation (MD) regimen that preferentially reduces fat mass, restoring normal body weight and glycemic control to diet-induced obese mice of both sexes. The benefits of MD do not accrue from calorie restriction, but instead result from increased energy expenditure. MD promotes increased energy expenditure in a sex-specific manner, inducing the fibroblast growth factor (Fgf)-21-uncoupling protein (Ucp)-1 axis only in males. Methionine is an agonist of the protein kinase mechanistic target of rapamycin complex (mTORC)-1, which has been proposed to play a key role in the metabolic response to amino acid-restricted diets. In our study, we used a mouse model of constitutive hepatic mTORC1 activity and demonstrate that suppression of hepatic mTORC1 signaling is not required for the metabolic effects of MD. Our study sheds new light on the mechanisms by which dietary methionine regulates metabolic health and demonstrates the translational potential of MD for the treatment of obesity and type 2 diabetes.-Yu, D., Yang, S. E., Miller, B. R., Wisinski, J. A., Sherman, D. S., Brinkman, J. A., Tomasiewicz, J. L., Cummings, N. E., Kimple, M. E., Cryns, V. L., Lamming, D. W. Short-term methionine deprivation improves metabolic health via sexually dimorphic, mTORC1-independent mechanisms.

SUMMARY Calorie restriction (CR) extends the healthspan and lifespan of diverse species. In mammals, a broadly conserved metabolic effect of CR is improved insulin sensitivity, which may mediate the beneficial effects of a CR diet. This model has been challenged by the identification of interventions that extend lifespan and healthspan, yet promote insulin resistance. These include rapamycin, which extends mouse lifespan yet induces insulin resistance by disrupting mTORC2 (mechanistic Target Of Rapamycin Complex 2). Here, we induce insulin resistance by genetically disrupting adipose mTORC2 via tissue-specific deletion of the mTORC2 component Rictor (AQ-RKO). Loss of adipose mTORC2 blunts the metabolic adaptation to CR, and prevents whole-body sensitization to insulin. Despite this, AQ-RKO mice subject to CR experience the same increase in fitness and lifespan on a CR diet as wild-type mice. We conclude that the CR-induced improvement in insulin sensitivity is dispensable for the effects of CR on fitness and longevity.

S-adenosylmethionine (SAM) is the methyl-donor substrate for DNA and histone methyltransferases that regulate cellular epigenetic states. This metabolism-epigenome link enables the sensitization of chromatin methylation to altered SAM abundance. However, a chromatin-wide understanding of the adaptive/responsive mechanisms that allow cells to actively protect epigenetic information during life-experienced fluctuations in SAM availability are unknown. We identified a robust response to SAM depletion that is highlighted by preferential cytoplasmic and nuclear de novo mono-methylation of H3 Lys 9 (H3K9) at the expense of global losses in histone di-and tri-methylation. Under SAM-depleted conditions, de novo H3K9 mono-methylation preserves heterochromatin stability and supports global epigenetic persistence upon metabolic recovery. This unique chromatin response was robust across the mouse lifespan and correlated with improved metabolic health, supporting a significant role for epigenetic adaptation to SAM depletion in vivo. Together, these studies provide the first evidence for active epigenetic adaptation and persistence to metabolic stress.

The wide applications of lithium intercalating complex metal oxides in energy storage devices call for a better understanding of their environmental impact at the end of their life cycle. In this study, we examine the biological impact of a panel of nanoscale lithium nickel manganese cobalt oxides (LixNiyMnzCo1−y−zO2, 0 < x, y, z < 1, abbreviated to NMCs) to a model Gram-positive bacterium, Bacillus subtilis, in terms of cellular respiration and growth. A highly sensitive single-cell gel electrophoresis method is also applied for the first time to understand the genotoxicity of these nanomaterials to bacterial cells. Results from these assays indicate that the free Ni and Co ions released from the incongruent dissolution of the NMC material in B. subtilis growth medium induced both hindered growth and cellular respiration. More remarkably, the DNA damage induced by the combination of the two ions in solution is comparable to that induced by the NMC material, which suggests that the free Ni and Co ions are responsible for the toxicity observed. A material redesign by enriching Mn is also presented. The combined approaches of evaluating their impact on bacterial growth, respiration, and DNA damage at a single-cell level, as well as other phenotypical changes allows us to probe the nanomaterials and bacterial cells from a mechanistic prospective, and provides a useful means to an understanding of bacterial response to new potential environmental stressors.

29S-adenosylmethionine (SAM) is the methyl-donor substrate for DNA and histone 30 methyltransferases that regulate cellular epigenetic states. This metabolism-epigenome link 31 enables the sensitization of chromatin methylation to altered SAM abundance. However, a 32 chromatin-wide understanding of the adaptive/responsive mechanisms that allow cells to 33 actively protect epigenetic information during life-experienced fluctuations in SAM availability 34 are unknown. We identified a robust response to SAM depletion that is highlighted by 35 preferential cytoplasmic and nuclear de novo mono-methylation of H3 Lys 9 (H3K9) at the 36 expense of global losses in histone di-and tri-methylation. Under SAM-depleted conditions, de 37 novo H3K9 mono-methylation preserves heterochromatin stability and supports global 38 epigenetic persistence upon metabolic recovery. This unique chromatin response was robust 39 across the mouse lifespan and correlated with improved metabolic health, supporting a 40 significant role for epigenetic adaptation to SAM depletion in vivo. Together, these studies 41 provide the first evidence for active epigenetic adaptation and persistence to metabolic stress. 42 43 44 persistence 109 responses to Met-restriction in both HCT116 cells and C57BL/6J liver (Figure 1D-1E). In 110 HCT116 cells, Met-restriction stimulated distinct biphasic changes in global PTM profiles (Figure 111 1D). Phase I (0 hr-45 min) was rapid and marked by a trending upregulation of H3K4me2/3, 112PTMs known to mark transcriptionally active promoters. Phase II (90 min-24 hrs) was 113 characterized by global decreases in di-and tri-histone methylation. Decreased levels of di-114 and tri-methylated peptides were accompanied by increases in acetylated and unmodified 115 peptide species. Similarly in C57BL/6J mice, histone PTM responses were marked by 116 significant decreases in histone di-and tri-methylation that essentially matched the patterns 117 found in HCT116 cells during the prolonged Phase II response ( Figure 1E and Figure S1E-S1J). 118Decreased higher state (di-and tri-) histone methylation both in vitro and in vivo highlights a 119 decreased methylation capacity resulting from prolonged Met and/or SAM depletion. Together, 120 these observations suggest perturbed methyl-donor metabolism is capable of stimulating 121 significant changes in histone, but not global 5mC, methylation abundance. Furthermore, 122 similarities between the metabolic and epigenetic responses to Met-restriction across both 123 systems support the use of in vitro Met-restriction as a model for mechanistic follow-up studies. 124 125 Decreased SAM Availability Drives Robust Histone Methylation Response 126 127 Dramatic reduction of intracellular Met and SAM correlated with onset of the in vitro 128 Phase I and II histone PTM changes, respectively (Figure 1D and Figure S1A-S1B). This 129 implies depletion of individual methyl-metabolites may be capable of stimulating distinct histone 130 modifying pathways. To determine if the global losses in di-and tr...

Obesity has become an increasing health problem in the United States and worldwide; effective interventions that promote weight loss are urgently needed. Dietary restriction of methionine promotes leanness and improves metabolic health in mice and humans. However, poor long‐term adherence to this diet limits its translational potential. To address this problem, we have developed short‐term methionine deprivation as a rapid and effective strategy to reduce adiposity and promote metabolic health.We examined the effects of a short‐term MD regimen on the metabolic health of C57BL/6J mice of both sexes, including 1) young mice raised on a chow diet; 2) young mice preconditioned with a Western high‐fat, high‐sucrose diet for 12 weeks; and 3) aged mice on a chow diet. We examined weight, body composition, glucose and insulin tolerance, food intake, activity and energy expenditure. We further examined hepatic steatosis and gene expression in multiple tissues. Using metabolomic and proteomic approaches, we also determined methionine metabolite levels and evaluated global histone post‐translational modification profiles in the liver. Finally, as dietary methionine is an agonist of the protein kinase mTORC1 (mechanistic Target of Rapamycin Complex 1), which is proposed to play a key role in the metabolic response to amino acid‐restricted diets, we examined the role of hepatic mTORC1 in the metabolic response to MD using a mouse model of constitutive hepatic mTORC1 activity.We find that a short‐term MD regimen preferentially reduces fat mass, restoring normal body weight and glycemic control to diet‐induced obese mice of both sexes. Additionally, we have examined the persistence of these metabolic changes in young and aged mice. We find that the benefits of MD do not accrue from calorie restriction, but instead result from increased energy expenditure. Intriguingly, MD promotes increased energy expenditure in both sexes, but induces the FGF21‐UCP1 axis only in males. We also observed sex‐specific effects of MD on lipid metabolism. The metabolic analysis revealed that MD significantly decreases levels of methionine as well as the methionine metabolite SAM (S‐adenosyl methionine) in the liver, and that accordingly, histone methylation in the liver is dramatically downregulated compared to control. Furthermore, using liver‐specific TSC1 knockout mice, which have constitutively active hepatic mTORC1, we determined that the metabolic effects of MD do not depend upon reduced hepatic mTORC1 signaling.Our study sheds new light on the mechanisms by which dietary methionine regulates metabolic health. In particular, our results suggest that sex‐dependent mechanisms may mediate the metabolic response to decreased dietary methionine, and that the FGF21‐UCP1 axis may be dispensable for the metabolic benefits of MD in females. Our results also demonstrate that the metabolic benefits of MD are not mediated by suppression of hepatic mTORC1 signaling. Our study clearly demonstrates the translational potential of MD or MD‐mimetics for the treatment of obesity and type 2 diabetes, diseases which are highly prevalent in the aged.Support or Funding InformationThis research was supported in part by grants from the NIH AG041765 (D.W.L.), AG050135 (D.W.L.), AG051974 (D.W.L.), GM059789‐15/P250VA (J.M.D), a New Investigator Program Award (D.W.L.) and a Collaborative Health Sciences Program Award (V.L.C.) from the Wisconsin Partnership Program, the V. Foundation for Cancer Research (V.L.C.), and a Glenn Foundation Award for Research in the Biological Mechanisms of Aging (D.W.L.), as well as startup funds from the UW‐Madison School of Medicine and Public Health and the UW‐Madison Department of Medicine (V.L.C. and D.W.L.). This research was conducted while D.W.L. was an AFAR Research Grant recipient from the American Federation for Aging Research. D.Y. is supported in part by a fellowship from the American Heart Association (17PRE33410983). S.A.H. is supported by a training grant from the NIH/NIDDK (T32DK007665). This work was supported using facilities and resources from the William S. Middleton Memorial Veterans Hospital. This work does not represent the views of the Department of Veterans Affairs or the United States Government.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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