Increasing cellular glucose uptake is a fundamental concept in treatment of type 2 diabetes, whereas nutritive calorie restriction increases life expectancy. We show here that increased glucose availability decreases Caenorhabditis elegans life span, while impaired glucose metabolism extends life expectancy by inducing mitochondrial respiration. The histone deacetylase Sir2.1 is found here to be dispensable for this phenotype, whereas disruption of aak-2, a homolog of AMP-dependent kinase (AMPK), abolishes extension of life span due to impaired glycolysis. Reduced glucose availability promotes formation of reactive oxygen species (ROS), induces catalase activity, and increases oxidative stress resistance and survival rates, altogether providing direct evidence for a hitherto hypothetical concept named mitochondrial hormesis or "mitohormesis." Accordingly, treatment of nematodes with different antioxidants and vitamins prevents extension of life span. In summary, these data indicate that glucose restriction promotes mitochondrial metabolism, causing increased ROS formation and cumulating in hormetic extension of life span, questioning current treatments of type 2 diabetes as well as the widespread use of antioxidant supplements.

Ageing has been defined as a global decline in physiological function depending on both environmental and genetic factors. Here we identify gene transcripts that are similarly regulated during physiological ageing in nematodes, zebrafish and mice. We observe the strongest extension of lifespan when impairing expression of the branched-chain amino acid transferase-1 (bcat-1) gene in C. elegans, which leads to excessive levels of branched-chain amino acids (BCAAs). We further show that BCAAs reduce a LET-363/mTOR-dependent neuro-endocrine signal, which we identify as DAF-7/TGFβ, and that impacts lifespan depending on its related receptors, DAF-1 and DAF-4, as well as ultimately on DAF-16/FoxO and HSF-1 in a cell-non-autonomous manner. The transcription factor HLH-15 controls and epistatically synergizes with BCAT-1 to modulate physiological ageing. Lastly and consistent with previous findings in rodents, nutritional supplementation of BCAAs extends nematodal lifespan. Taken together, BCAAs act as periphery-derived metabokines that induce a central neuro-endocrine response, culminating in extended healthspan.

The AMP-activated protein kinase (AMPK) regulates cellular energy homeostasis by sensing the metabolic status of the cell. AMPK is regulated by phosphorylation and dephosphorylation as a result of changing AMP/ATP levels and by removal of inhibitory ubiquitin residues by USP10. In this context, we identified the GID-complex, an evolutionarily conserved ubiquitin-ligase-complex (E3), as a negative regulator of AMPK activity. Our data show that the GID-complex targets AMPK for ubiquitination thereby altering its activity. Cells depleted of GID-subunits mimic a state of starvation as shown by increased AMPK activity and macroautophagic/autophagic flux as well as reduced MTOR activation. Consistently, gid-genes knockdown in C. elegans results in increased organismal lifespan. This study may contribute to understand metabolic disorders such as type 2 diabetes mellitus and morbid obesity and implements alternative therapeutic approaches to alter AMPK activity.

The redox environment in cells and organisms is set by low-molecular mass and protein-bound thiols, with glutathione (GSH) representing a major intracellular redox buffer. Subtle thiol oxidation elicits signal transduction processes and adaptive responses to cope with stressors, whereas highly oxidizing conditions may provoke cell death. We here tested how thiol depletion affects life span, stress resistance and stress signaling in the model organism Caenorhabditis elegans. Diethyl maleate (DEM), an α,β-unsaturated carbonyl compound that conjugates to GSH and other thiols, decreased C. elegans life span at a concentration of 1 mM. In contrast, low and moderate doses of DEM (10–100 µM) increased mean and maximum life span and improved resistance against oxidative stress. DEM-induced life span extension was not detectable in worms deficient in either the FoxO orthologue, DAF-16, or the Nrf2 orthologue, SKN-1, pointing to a collaborative role of the two transcription factors in life span extension induced by thiol depletion. Cytoprotective target genes of DAF-16 and SKN-1 were upregulated after at least 3 days of exposure to 100 µM DEM, but not 1 mM DEM, whereas only 1 mM DEM caused upregulation of egl-1, a gene controlled by a p53-orthologue, CEP-1. In order to test whether depletion of GSH may elicit effects similar to DEM, we suppressed GSH biosynthesis in worms by attenuating γ-glutamylcysteine synthetase (gcs-1) expression through RNAi. The decline in GSH levels elicited by gcs-1 knockdown starting at young adult stage did not impair viability, but increased both stress resistance and life expectancy of the worms. In contrast, gcs-1 knockdown commencing right after hatching impaired nematode stress resistance and rendered young adult worms prone to vulval ruptures during egg-laying. Thus, modest decrease in GSH levels in young adult worms may promote stress resistance and life span, whereas depletion of GSH is detrimental to freshly hatched and developing worms.

Human selenium-binding protein 1 (SELENBP1) was originally identified as a protein binding selenium, most likely as selenite. SELENBP1 is associated with cellular redox and thiol homeostasis in several respects, including its established role as a methanethiol oxidase that is involved in degradation of methanethiol, a methionine catabolite, generating hydrogen sulfide (H2S) and hydrogen peroxide (H2O2). As both H2S and reactive oxygen species (such as H2O2) are major regulators of Caenorhabditis elegans lifespan and stress resistance, we hypothesized that a SELENBP1 ortholog in C. elegans would likely be involved in regulating these aspects.Here we characterize Y37A1B.5, a putative selenium-binding protein 1 ortholog in C. elegans with 52% primary structure identity to human SELENBP1. While conferring resistance to toxic concentrations of selenite, Y37A1B.5 also attenuates resistance to oxidative stress and lowers C. elegans lifespan: knockdown of Y37A1B.5 using RNA interference resulted in an approx. 10% increase of C. elegans lifespan and an enhanced resistance against the redox cycler paraquat, as well as enhanced motility. Analyses of transgenic reporter strains suggest hypodermal expression and cytoplasmic localization of Y37A1B.5, whose expression decreases with worm age. We identify the transcriptional coregulator MDT-15 and transcription factor EGL-27 as regulators of Y37A1B.5 levels and show that the lifespan extending effect elicited by downregulation of Y37A1B.5 is independent of known MDT-15 interacting factors, such as DAF-16 and NHR-49. In summary, Y37A1B.5 is an ortholog of SELENBP1 that shortens C. elegans lifespan and lowers resistance against oxidative stress, while allowing for a better survival under toxic selenite concentrations.

Diethyl maleate (DEM), a thiol-reactive α,β-unsaturated carbonyl compound, depletes glutathione (GSH) in exposed cells and was previously shown by us to elicit a stress response in Caenorhabditis elegans that, at lower concentrations, results in enhanced stress resistance and longer lifespan. This hormetic response was mediated through both the Nrf2 ortholog, SKN-1, and the forkhead box O (FOXO) family transcription factor DAF-16. As FOXO signaling is evolutionarily conserved, we analyzed here the effects of DEM exposure on FOXO in cultured human cells (HepG2, HEK293). DEM elicited nuclear accumulation of GFP-coupled wild-type human FOXO1, as well as of a cysteine-deficient FOXO1 mutant. Despite the nuclear accumulation of FOXO1, neither FOXO1 DNA binding nor FOXO target gene expression were stimulated, suggesting that DEM causes nuclear accumulation but not activation of FOXO1. FOXO1 nuclear exclusion elicited by insulin or xenobiotics such as arsenite or copper ions was attenuated by DEM, suggesting that DEM interfered with nuclear export. In addition, insulin-induced FOXO1 phosphorylation at Thr-24, which is associated with FOXO1 nuclear exclusion, was attenuated upon exposure to DEM. Different from FOXO-dependent expression of genes, Nrf2 target gene mRNAs were elevated upon exposure to DEM. These data suggest that, different from C. elegans, DEM elicits opposing effects on the two stress-responsive transcription factors, Nrf2 and FOXO1, in cultured human cells.

Background: The essential trace element and micronutrient selenium exerts most of its biological actions through incorporation into selenoproteins as selenocysteine. Two further types of Se-containing proteins exist, including those that have selenomethionine incorporated instead of methionine, and the group of selenium-binding proteins. We previously described an ortholog of selenium-binding protein 1 (SELENBP1) in the nematode Caenorhabditis elegans, Y37A1B.5, and demonstrated that it confers resistance to toxic selenite concentrations while impairing general stress resistance and life expectancy of C. elegans. Objective: We tested for the effect of selenite on Y37A1B.5 expression, and we analyzed whether Y37A1B.5 also shows a lifespan-modulating effect when the nematodes are deficient in the selenoenzyme thioredoxin reductase-1 (TRXR-1). Methods: C. elegans expressing a translational reporter construct encoding GFP-tagged Y37A1B.5 under the control of the Y37A1B.5 promoter were exposed to selenite, followed by fluorescence microscopic analysis of GFP levels. Lifespan analyses and RNA interference experiments were performed in trxr-1-deficient worms. Results: We here demonstrate that selenite at toxic concentrations stimulates the expression of the translational Y37A1B.5 reporter. The lifespan-extending effect of Y37A1B.5 deficiency was preserved upon the deletion of the only selenoprotein in C. elegans, TRXR-1. Conclusion: These data suggest that (1) Y37A1B.5 may serve as a selenite-responsive buffer against high environmental selenium concentrations and that (2) lifespan extension elicited by Y37A1B.5 knockdown does not require functional TRXR-1.

Raman spectroscopy reveals distribution of glycogen in C. elegans.