Spermidine-induced hypusination preserves mitochondrial and cognitive function during aging.

Spermidine is a natural polyamine, central to cellular homeostasis and growth, that promotes macroautophagy/autophagy. The polyamine pathway is highly conserved from bacteria to mammals and spermidine (prominently found in some kinds of aged cheese, wheat germs, nuts, soybeans, and fermented products thereof, among others) is an intrinsic part of the human diet. Apart from nutrition, spermidine is available to mammalian organisms from intracellular biosynthesis and microbial production in the gut. Importantly, externally supplied spermidine (via drinking water or food) prolongs lifespan, activates autophagy, improves mitochondrial function, and refills polyamine pools that decline during aging in various tissues of model organisms, including mice. In two adjacent studies, we explored how dietary spermidine supplementation enhances eEF5/EIF5A hypusination, cerebral mitochondrial function and cognition in aging Drosophila melanogaster and mice.

Dietary spermidine improves cognitive function.

Decreased cognitive performance is a hallmark of brain aging, but the underlying mechanisms and potential therapeutic avenues remain poorly understood. Recent studies have revealed health-protective and lifespan-extending effects of dietary spermidine, a natural autophagy-promoting polyamine. Here, we show that dietary spermidine passes the blood-brain barrier in mice and increases hippocampal eIF5A hypusination and mitochondrial function. Spermidine feeding in aged mice affects behavior in homecage environment tasks, improves spatial learning, and increases hippocampal respiratory competence. In a Drosophila aging model, spermidine boosts mitochondrial respiratory capacity, an effect that requires the autophagy regulator Atg7 and the mitophagy mediators Parkin and Pink1. Neuron-specific Pink1 knockdown abolishes spermidine-induced improvement of olfactory associative learning. This suggests that the maintenance of mitochondrial and autophagic function is essential for enhanced cognition by spermidine feeding. Finally, we show large-scale prospective data linking higher dietary spermidine intake with a reduced risk for cognitive impairment in humans.

Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-obese Humans.

Caloric restriction and intermittent fasting are known to prolong life- and healthspan in model organisms, while their effects on humans are less well studied. In a randomized controlled trial study (ClinicalTrials.gov identifier: NCT02673515), we show that 4 weeks of strict alternate day fasting (ADF) improved markers of general health in healthy, middle-aged humans while causing a 37% calorie reduction on average. No adverse effects occurred even after >6 months. ADF improved cardiovascular markers, reduced fat mass (particularly the trunk fat), improving the fat-to-lean ratio, and increased ß-hydroxybutyrate, even on non-fasting days. On fasting days, the pro-aging amino-acid methionine, among others, was periodically depleted, while polyunsaturated fatty acids were elevated. We found reduced levels sICAM-1 (an age-associated inflammatory marker), low-density lipoprotein, and the metabolic regulator triiodothyronine after long-term ADF. These results shed light on the physiological impact of ADF and supports its safety. ADF could eventually become a clinically relevant intervention.

Acetyl-CoA carboxylase 1-dependent lipogenesis promotes autophagy downstream of AMPK.

Autophagy, a membrane-dependent catabolic process, ensures survival of aging cells and depends on the cellular energetic status. Acetyl-CoA carboxylase 1 (Acc1) connects central energy metabolism to lipid biosynthesis and is rate-limiting for the de novo synthesis of lipids. However, it is unclear how de novo lipogenesis and its metabolic consequences affect autophagic activity. Here, we show that in aging yeast, autophagy levels highly depend on the activity of Acc1. Constitutively active Acc1 (acc1S/A ) or a deletion of the Acc1 negative regulator, Snf1 (yeast AMPK), shows elevated autophagy levels, which can be reversed by the Acc1 inhibitor soraphen A. Vice versa, pharmacological inhibition of Acc1 drastically reduces cell survival and results in the accumulation of Atg8-positive structures at the vacuolar membrane, suggesting late defects in the autophagic cascade. As expected, acc1S/A cells exhibit a reduction in acetate/acetyl-CoA availability along with elevated cellular lipid content. However, concomitant administration of acetate fails to fully revert the increase in autophagy exerted by acc1S/A Instead, administration of oleate, while mimicking constitutively active Acc1 in WT cells, alleviates the vacuolar fusion defects induced by Acc1 inhibition. Our results argue for a largely lipid-dependent process of autophagy regulation downstream of Acc1. We present a versatile genetic model to investigate the complex relationship between acetate metabolism, lipid homeostasis, and autophagy and propose Acc1-dependent lipogenesis as a fundamental metabolic path downstream of Snf1 to maintain autophagy and survival during cellular aging.

4,4'Dimethoxychalcone: a natural flavonoid that promotes health through autophagy-dependent and -independent effects.

The age-induced deterioration of the organism results in detrimental and ultimately lethal pathologies. The process of aging itself involves a plethora of different mechanisms that should be subverted concurrently to delay and/or prevent age-related maladies. We have identified a natural compound, 4,4'-dimethoxychalcone (DMC), which promotes longevity in yeast, worms and flies, and protects mice from heart injury and liver toxicity. Interestingly, both the DMC-mediated lifespan extension and the cardioprotection depend on macroautophagy/autophagy whereas hepatoprotection does not. DMC induces autophagy by inhibiting specific GATA transcription factors (TFs), independently of the TORC1 kinase pathway. The autophagy-independent beneficial effects of DMC might involve its antioxidative properties. DMC treatment results in a phylogenetically conserved, systemic impact on the metabolome, which is most prominently characterized by changes in cellular amino acid composition. Altogether, DMC exerts multiple, geroprotective effects by igniting distinct pathways, and thus represents a potential pharmacological agent that delays aging through multipronged effects.

Targeting GATA transcription factors - a novel strategy for anti-aging interventions?

GATA transcription factors (TFs) are a conserved family of zinc-finger TFs that fulfill diverse functions across eukaryotes. Accumulating evidence suggests that GATA TFs also play a role in lifespan regulation. In a recent study, we have identified a natural compound, 4,4' dimethoxychalcone (DMC) that extends lifespan depending on reduced activity of distinct GATA TFs. Prolonged lifespan by DMC treatment depends on autophagy, a protective cellular self-cleaning mechanism. In yeast, DMC reduces the activity of the GATA TF Gln3 and, at the same time, deletion of GLN3 increases autophagy levels during cellular aging per se. Here, we examine current data on the involvement of GATA TFs in the regulation of both autophagy and lifespan in different organisms and explore, if GATA TFs are suitable targets for anti-aging interventions.

The flavonoid 4,4'-dimethoxychalcone promotes autophagy-dependent longevity across species.

Ageing constitutes the most important risk factor for all major chronic ailments, including malignant, cardiovascular and neurodegenerative diseases. However, behavioural and pharmacological interventions with feasible potential to promote health upon ageing remain rare. Here we report the identification of the flavonoid 4,4'-dimethoxychalcone (DMC) as a natural compound with anti-ageing properties. External DMC administration extends the lifespan of yeast, worms and flies, decelerates senescence of human cell cultures, and protects mice from prolonged myocardial ischaemia. Concomitantly, DMC induces autophagy, which is essential for its cytoprotective effects from yeast to mice. This pro-autophagic response induces a conserved systemic change in metabolism, operates independently of TORC1 signalling and depends on specific GATA transcription factors. Notably, we identify DMC in the plant Angelica keiskei koidzumi, to which longevity- and health-promoting effects are ascribed in Asian traditional medicine. In summary, we have identified and mechanistically characterised the conserved longevity-promoting effects of a natural anti-ageing drug.

HIV-1 gp41 transmembrane oligomerization monitored by FRET and FCS.

The HIV-1 envelope gp120/gp41 trimer mediates viral membrane fusion. After cluster of differentiation-4 recognition, gp120 detaches from the virus, exposing gp41 which triggers fusion. During the fusion process, gp41 may not remain trimeric, which could have functional importance. Here, we probe the reversible association of full length gp41 (minus the cytoplasmic domain) in detergent micelles (with probes attached to transmembrane domain) by fluorescence resonance energy transfer (FRET) with a µm dissociation constant. This is compared with other methods. A gp41-targeted fusion inhibitor must interfere with this transition, and monomeric, partially monomeric or trimeric states all present potential binding epitopes. The gp41 self-association is a valid drug target model and FRET, a potential high-throughput assay system, could be used to screen drug libraries.

Dietary spermidine for lowering high blood pressure.

Loss of cardiac macroautophagy/autophagy impairs heart function, and evidence accumulates that an increased autophagic flux may protect against cardiovascular disease. We therefore tested the protective capacity of the natural autophagy inducer spermidine in animal models of aging and hypertension, which both represent major risk factors for the development of cardiovascular disease. Dietary spermidine elicits cardioprotective effects in aged mice through enhancing cardiac autophagy and mitophagy. In salt-sensitive rats, spermidine supplementation also delays the development of hypertensive heart disease, coinciding with reduced arterial blood pressure. The high blood pressure-lowering effect likely results from improved global arginine bioavailability and protection from hypertension-associated renal damage. The polyamine spermidine is naturally present in human diets, though to a varying amount depending on food type and preparation. In humans, high dietary spermidine intake correlates with reduced blood pressure and decreased risk of cardiovascular disease and related death. Altogether, spermidine represents a cardio- and vascular-protective autophagy inducer that can be readily integrated in common diets.

Cardioprotection and lifespan extension by the natural polyamine spermidine.

Aging is associated with an increased risk of cardiovascular disease and death. Here we show that oral supplementation of the natural polyamine spermidine extends the lifespan of mice and exerts cardioprotective effects, reducing cardiac hypertrophy and preserving diastolic function in old mice. Spermidine feeding enhanced cardiac autophagy, mitophagy and mitochondrial respiration, and it also improved the mechano-elastical properties of cardiomyocytes in vivo, coinciding with increased titin phosphorylation and suppressed subclinical inflammation. Spermidine feeding failed to provide cardioprotection in mice that lack the autophagy-related protein Atg5 in cardiomyocytes. In Dahl salt-sensitive rats that were fed a high-salt diet, a model for hypertension-induced congestive heart failure, spermidine feeding reduced systemic blood pressure, increased titin phosphorylation and prevented cardiac hypertrophy and a decline in diastolic function, thus delaying the progression to heart failure. In humans, high levels of dietary spermidine, as assessed from food questionnaires, correlated with reduced blood pressure and a lower incidence of cardiovascular disease. Our results suggest a new and feasible strategy for protection against cardiovascular disease.

High reactive oxygen species levels are detected at the end of the chronological life span of translocant yeast cells.

Chromosome translocation is a major genomic event for a cell, affecting almost every of its life aspects ranging from metabolism, organelle maintenance and homeostasis to gene maintenance and expression. By using the bridge-induced translocation system, we defined the effects of induced chromosome translocation on the chronological life span (CLS) of yeast with particular interest to the oxidative stress condition. The results demonstrate that every translocant strain has a different CLS, but all have a high increase in reactive oxygen species and in lipid peroxides levels at the end of the life span. This could be due to the very unique and strong deregulation of the oxidative stress network. Furthermore, the loss of the translocated chromosome occurs at the end of the life span and is locus dependent. Additionally, the RDH54 gene may play a role in the correct segregation of the translocant chromosome, since in its absence there is an increase in loss of the bridge-induced translocated chromosome.

Feline paraneoplastic alopecia associated with metastasising intestinal carcinoma.

CASE SUMMARY: A 10-year-old male neutered British Shorthair cat was presented with a 6 month history of lethargy, weight loss and alopecia. Clinical examination revealed widespread alopecia of the ventral abdomen and hindlimbs. The skin in these areas was smooth and shiny and hairs could be easily epilated. Spontaneous pruritus was observed. Cytological examination of superficial impression smears showed a severe Malassezia species dermatitis and pyoderma. Ectoparasites could not be detected and no sign of dermatophytosis was visible in trichograms and Wood's lamp analysis. Abdominal ultrasound found a focally thickened wall of the large intestine and multiple nodules in the liver. Fine-needle aspirates from lymph nodes, liver and altered colonic wall were consistent with an undifferentiated malignant neoplasia. The cat was euthanased at the owners' request, owing to potential neoplasia with metastatic spread. At necropsy a metastasising carcinoma of the colonic wall was found, as well as a paraneoplastic alopecia. RELEVANCE AND NOVEL INFORMATION: Feline paraneoplastic alopecia has been reported in association with pancreatic carcinoma, bile duct carcinoma and hepatocellular carcinoma, as well as with neuroendocrine pancreatic carcinoma and hepatosplenic plasma cell tumour. This is the first reported case of feline paraneoplastic alopecia associated with a colon carcinoma.

A histone point mutation that switches on autophagy.

The multifaceted process of aging inevitably leads to disturbances in cellular metabolism and protein homeostasis. To meet this challenge, cells make use of autophagy, which is probably one of the most important pathways preserving cellular protection under stressful conditions. Thus, efficient autophagic flux is required for healthy aging in many if not all eukaryotic organisms. The regulation of autophagy itself is affected by changing metabolic conditions, but the precise metabolic circuitries are poorly understood. Recently, we found that the nucleocytosolic pool of acetyl-coenzyme A (AcCoA) functions as a major and dominant suppressor of cytoprotective autophagy during aging. Here, we propose an epigenetic mechanism for AcCoA-mediated autophagy suppression that causally involves the regulation of histone acetylation and changes in the autophagy-relevant transcriptome.

Acetyl-coenzyme A: a metabolic master regulator of autophagy and longevity.

As the major lysosomal degradation pathway, autophagy represents the guardian of cellular homeostasis, removing damaged and potentially harmful material and replenishing energy reserves in conditions of starvation. Given its vast physiological importance, autophagy is crucially involved in the process of aging and associated pathologies. Although the regulation of autophagy strongly depends on nutrient availability, specific metabolites that modulate autophagic responses are poorly described. Recently, we revealed nucleo-cytosolic acetyl-coenzyme A (AcCoA) as a phylogenetically conserved inhibitor of starvation-induced and age-associated autophagy. AcCoA is the sole acetyl-group donor for protein acetylation, explaining why pharmacological or genetic manipulations that modify the concentrations of nucleo-cytosolic AcCoA directly affect the levels of protein acetylation. The acetylation of histones and cytosolic proteins inversely correlates with the rate of autophagy in yeast and mammalian cells, respectively, despite the fact that the routes of de novo AcCoA synthesis differ across phyla. Thus, we propose nucleo-cytosolic AcCoA to act as a conserved metabolic rheostat, linking the cellular metabolic state to the regulation of autophagy via effects on protein acetylation.

Nucleocytosolic depletion of the energy metabolite acetyl-coenzyme a stimulates autophagy and prolongs lifespan.

Healthy aging depends on removal of damaged cellular material that is in part mediated by autophagy. The nutritional status of cells affects both aging and autophagy through as-yet-elusive metabolic circuitries. Here, we show that nucleocytosolic acetyl-coenzyme A (AcCoA) production is a metabolic repressor of autophagy during aging in yeast. Blocking the mitochondrial route to AcCoA by deletion of the CoA-transferase ACH1 caused cytosolic accumulation of the AcCoA precursor acetate. This led to hyperactivation of nucleocytosolic AcCoA-synthetase Acs2p, triggering histone acetylation, repression of autophagy genes, and an age-dependent defect in autophagic flux, culminating in a reduced lifespan. Inhibition of nutrient signaling failed to restore, while simultaneous knockdown of ACS2 reinstated, autophagy and survival of ach1 mutant. Brain-specific knockdown of Drosophila AcCoA synthetase was sufficient to enhance autophagic protein clearance and prolong lifespan. Since AcCoA integrates various nutrition pathways, our findings may explain diet-dependent lifespan and autophagy regulation.

Regulation of autophagy by cytosolic acetyl-coenzyme A.

Acetyl-coenzyme A (AcCoA) is a major integrator of the nutritional status at the crossroads of fat, sugar, and protein catabolism. Here we show that nutrient starvation causes rapid depletion of AcCoA. AcCoA depletion entailed the commensurate reduction in the overall acetylation of cytoplasmic proteins, as well as the induction of autophagy, a homeostatic process of self-digestion. Multiple distinct manipulations designed to increase or reduce cytosolic AcCoA led to the suppression or induction of autophagy, respectively, both in cultured human cells and in mice. Moreover, maintenance of high AcCoA levels inhibited maladaptive autophagy in a model of cardiac pressure overload. Depletion of AcCoA reduced the activity of the acetyltransferase EP300, and EP300 was required for the suppression of autophagy by high AcCoA levels. Altogether, our results indicate that cytosolic AcCoA functions as a central metabolic regulator of autophagy, thus delineating AcCoA-centered pharmacological strategies that allow for the therapeutic manipulation of autophagy.

Restoring polyamines protects from age-induced memory impairment in an autophagy-dependent manner.

Age-dependent memory impairment is known to occur in several organisms, including Drosophila, mouse and human. However, the fundamental cellular mechanisms that underlie these impairments are still poorly understood, effectively hampering the development of pharmacological strategies to treat the condition. Polyamines are among the substances found to decrease with age in the human brain. We found that levels of polyamines (spermidine, putrescine) decreased in aging fruit flies, concomitant with declining memory abilities. Simple spermidine feeding not only restored juvenile polyamine levels, but also suppressed age-induced memory impairment. Ornithine decarboxylase-1, the rate-limiting enzyme for de novo polyamine synthesis, also protected olfactory memories in aged flies when expressed specifically in Kenyon cells, which are crucial for olfactory memory formation. Spermidine-fed flies showed enhanced autophagy (a form of cellular self-digestion), and genetic deficits in the autophagic machinery prevented spermidine-mediated rescue of memory impairments. Our findings indicate that autophagy is critical for suppression of memory impairments by spermidine and that polyamines, which are endogenously present, are candidates for pharmacological intervention.

Friend or food: different cues to the autophagosomal proteome.

A hallmark of macroautophagy is the formation of autophagosomes, double-membrane vesicles that enwrap cellular components destined for lysosomal degradation. We examined autophagosomal protein dynamics under various inducing stimuli using a comprehensive mass spectrometry-based proteomics approach in combination with functional studies in yeast and human cell cultures. Time frame and stimuli type influenced the autophagosome proteome, underlining the dynamic constitution of the organelle. We identified both a core set of proteins always localizing to autophagosomes and stimulus-dependent components that will serve as a resource for further characterization of the autophagosomal machinery and cargo selection. Among the core proteins were newly discovered autophagy regulators found to be conserved from yeast to humans, as well as the proteasome.