Assessing chronological aging in Saccharomyces cerevisiae.

Chronological age represents the time that passes between birth and a given date. To understand the complex network of factors contributing to chronological lifespan, a variety of model organisms have been implemented. One of the best studied organisms is the yeast Saccharomyces cerevisiae, which has greatly contributed toward identifying conserved biological mechanisms that act on longevity. Here, we discuss high- und low-throughput protocols to monitor and characterize chronological lifespan and chronological aging-associated cell death in S. cerevisiae. Included are propidium iodide staining with the possibility to quantitatively assess aging-associated cell death via flow cytometry or qualitative assessments via microscopy, cell viability assessment through plating and cell counting and cell death characterization via propidium iodide/AnnexinV staining and subsequent flow cytometric analysis or microscopy. Importantly, all of these methods combined give a clear picture of the chronological lifespan under different conditions or genetic backgrounds and represent a starting point for pharmacological or genetic interventions.

Metabolic control of mitophagy.

Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.

Sex- and timing-specific effects of fasting and caloric restriction.

Optimizing food quantity and fasting time may improve health and lifespan. We summarize emerging knowledge on sex, age, and circadian timing as important determinants for the efficacy of dietary interventions and highlight results from Duregon et al. pointing to a favorable combination of caloric restriction (CR) and fasting in aged female mice.

Molecular targets of spermidine: implications for cancer suppression.

Spermidine is a ubiquitous, natural polyamine with geroprotective features. Supplementation of spermidine extends the lifespan of yeast, worms, flies, and mice, and dietary spermidine intake correlates with reduced human mortality. However, the crucial role of polyamines in cell proliferation has also implicated polyamine metabolism in neoplastic diseases, such as cancer. While depleting intracellular polyamine biosynthesis halts tumor growth in mouse models, lifelong external spermidine administration in mice does not increase cancer incidence. In contrast, a series of recent findings points to anti-neoplastic properties of spermidine administration in the context of immunotherapy. Various molecular mechanisms for the anti-aging and anti-cancer properties have been proposed, including the promotion of autophagy, enhanced translational control, and augmented mitochondrial function. For instance, spermidine allosterically activates mitochondrial trifunctional protein (MTP), a bipartite protein complex that mediates three of the four steps of mitochondrial fatty acid (ß-oxidation. Through this action, spermidine supplementation is able to restore MTP-mediated mitochondrial respiratory capacity in naïve CD8+ T cells to juvenile levels and thereby improves T cell activation in aged mice. Here, we put this finding into the context of the previously described molecular target space of spermidine.

Acyl coenzyme A binding protein (ACBP): An aging- and disease-relevant "autophagy checkpoint".

Acyl coenzyme A binding protein (ACBP), also known as diazepam-binding inhibitor (DBI), is a phylogenetically ancient protein present in some eubacteria and the entire eukaryotic radiation. In several eukaryotic phyla, ACBP/DBI transcends its intracellular function in fatty acid metabolism because it can be released into the extracellular space. This ACBP/DBI secretion usually occurs in response to nutrient scarcity through an autophagy-dependent pathway. ACBP/DBI and its peptide fragments then act on a range of distinct receptors that diverge among phyla, namely metabotropic G protein-coupled receptor in yeast (and likely in the mammalian central nervous system), a histidine receptor kinase in slime molds, and ionotropic gamma-aminobutyric acid (GABA)A receptors in mammals. Genetic or antibody-mediated inhibition of ACBP/DBI orthologs interferes with nutrient stress-induced adaptations such as sporulation or increased food intake in multiple species, as it enhances lifespan or healthspan in yeast, plant leaves, nematodes, and multiple mouse models. These lifespan and healthspan-extending effects of ACBP/DBI suppression are coupled to the induction of autophagy. Altogether, it appears that neutralization of extracellular ACBP/DBI results in "autophagy checkpoint inhibition" to unleash the anti-aging potential of autophagy. Of note, in humans, ACBP/DBI levels increase in various tissues, as well as in the plasma, in the context of aging, obesity, uncontrolled infection or cardiovascular, inflammatory, neurodegenerative, and malignant diseases.

Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models.

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

Glucose Metabolism and Metabolomic Changes in Response to Prolonged Fasting in Individuals with Obesity, Type 2 Diabetes and Non-Obese People-A Cohort Trial.

Metabolic regulation of glucose can be altered by fasting periods. We examined glucose metabolism and metabolomics profiles after 12 h and 36 h fasting in non-obese and obese participants and people with type 2 diabetes using oral glucose tolerance (OGTT) and intravenous glucose tolerance testing (IVGTT). Insulin sensitivity was estimated by established indices and mass spectrometric metabolomics was performed on fasting serum samples. Participants had a mean age of 43 ± 16 years (62% women). Fasting levels of glucose, insulin and C-peptide were significantly lower in all cohorts after 36 h compared to 12 h fasting (p < 0.05). In non-obese participants, glucose levels were significantly higher after 36 h compared to 12 h fasting at 120 min of OGTT (109 ± 31 mg/dL vs. 79 ± 18 mg/dL; p = 0.001) but insulin levels were lower after 36 h of fasting at 30 min of OGTT (41.2 ± 34.1 mU/L after 36 h vs. 56.1 ± 29.7 mU/L; p < 0.05). In contrast, no significant differences were observed in obese participants or people with diabetes. Insulin sensitivity improved in all cohorts after 36 h fasting. In line, metabolomics revealed subtle baseline differences and an attenuated metabolic response to fasting in obese participants and people with diabetes. Our data demonstrate an improved insulin sensitivity after 36 h of fasting with higher glucose variations and reduced early insulin response in non-obese people only.

High plasma concentrations of acyl-coenzyme A binding protein (ACBP) predispose to cardiovascular disease: Evidence for a phylogenetically conserved proaging function of ACBP.

Autophagy defects accelerate aging, while stimulation of autophagy decelerates aging. Acyl-coenzyme A binding protein (ACBP), which is encoded by a diazepam-binding inhibitor (DBI), acts as an extracellular feedback regulator of autophagy. As shown here, knockout of the gene coding for the yeast orthologue of ACBP/DBI (ACB1) improves chronological aging, and this effect is reversed by knockout of essential autophagy genes (ATG5, ATG7) but less so by knockout of an essential mitophagy gene (ATG32). In humans, ACBP/DBI levels independently correlate with body mass index (BMI) as well as with chronological age. In still-healthy individuals, we find that high ACBP/DBI levels correlate with future cardiovascular events (such as heart surgery, myocardial infarction, and stroke), an association that is independent of BMI and chronological age, suggesting that ACBP/DBI is indeed a biomarker of "biological" aging. Concurringly, ACBP/DBI plasma concentrations correlate with established cardiovascular risk factors (fasting glucose levels, systolic blood pressure, total free cholesterol, triglycerides), but are inversely correlated with atheroprotective high-density lipoprotein (HDL). In mice, neutralization of ACBP/DBI through a monoclonal antibody attenuates anthracycline-induced cardiotoxicity, which is a model of accelerated heart aging. In conclusion, plasma elevation of ACBP/DBI constitutes a novel biomarker of chronological aging and facets of biological aging with a prognostic value in cardiovascular disease.

DBI/ACBP is a targetable autophagy checkpoint involved in aging and cardiovascular disease.

DBI/ACBP (diazepam binding inhibitor, acyl-CoA binding protein) is a phylogenetically conserved paracrine inhibitor of macroautophagy/autophagy. As such, DBI/ACBP acts as a pro-aging molecule. Indeed, we observed that the knockout of ACB1 (the yeast equivalent of human DBI/ACBP) induces autophagy and prolongs lifespan in an autophagy-dependent fashion in chronological lifespan experiments. Intriguingly, circulating DBI/ACBP protein augments with age in humans, and this increase occurs independently from the known correlation of DBI/ACBP with body mass index (BMI). A supraphysiological DBI/ACBP level announces future cardiovascular disease (such as heart surgery, myocardial infarction and stroke) in still healthy individuals, suggesting that, beyond its correlation with chronological age, DBI/ACBP is a biomarker of biological age. Plasma DBI/ACBP concentrations correlate with triglycerides and anticorrelate with high-density lipoprotein. Of note, these associations with cardiovascular risk factors are independent from age and BMI in a multivariate regression model. In mice, we found that antibody-mediated neutralization of DBI/ACBP reduces signs of anthracycline-accelerated cardiac aging including the upregulation of the senescence marker CDKN2A/p16 (cyclin dependent kinase inhibitor 2A) and the functional decline of the heart. In conclusion, it appears that extracellular DBI/ACBP can be targeted to combat age-associated cardiovascular disease.Abbreviations: BMI: body mass index; CDKN2A/p16: cyclin dependent kinase inhibitor 2A; CVD: cardiovascular disease; DBI/ACBP: diazepam binding inhibitor, acyl-CoA binding protein; ELISA: enzyme-linked immunosorbent assay; GABA: gamma-aminobutyric acid; GABR: gamma-aminobutyric acid type A receptor.

Spermidine supplementation influences mitochondrial number and morphology in the heart of aged mice.

Aging is associated with cardiac hypertrophy and progressive decline in heart function. One of the hallmarks of cellular aging is the dysfunction of mitochondria. These organelles occupy around 1/4 to 1/3 of the cardiomyocyte volume. During cardiac aging, the removal of defective or dysfunctional mitochondria by mitophagy as well as the dynamic equilibrium between mitochondrial fusion and fission is distorted. Here, we hypothesized that these changes affect the number of mitochondria and alter their three-dimensional (3D) characteristics in aged mouse hearts. The polyamine spermidine stimulates both mitophagy and mitochondrial biogenesis, and these are associated with improved cardiac function and prolonged lifespan. Therefore, we speculated that oral spermidine administration normalizes the number of mitochondria and their 3D morphology in aged myocardium. Young (4-months old) and old (24-months old) mice, treated or not treated with spermidine, were used in this study (n = 10 each). The number of mitochondria in the left ventricles was estimated by design-based stereology using the Euler-Poincaré characteristic based on a disector at the transmission electron microscopic level. The 3D morphology of mitochondria was investigated by 3D reconstruction (using manual contour drawing) from electron microscopic z-stacks obtained by focused ion beam scanning electron microscopy. The volume of the left ventricle and cardiomyocytes were significantly increased in aged mice with or without spermidine treatment. Although the number of mitochondria was similar in young and old control mice, it was significantly increased in aged mice treated with spermidine. The interfibrillar mitochondria from old mice exhibited a lower degree of organization and a greater variation in shape and size compared to young animals. The mitochondrial alignment along the myofibrils in the spermidine-treated mice appeared more regular than in control aged mice, however, old mitochondria from animals fed spermidine also showed a greater diversity of shape and size than young mitochondria. In conclusion, mitochondria of the aged mouse left ventricle exhibited changes in number and 3D ultrastructure that is likely the structural correlate of dysfunctional mitochondrial dynamics. Spermidine treatment reduced, at least in part, these morphological changes, indicating a beneficial effect on cardiac mitochondrial alterations associated with aging.

Long-term fasting: Multi-system adaptations in humans (GENESIS) study-A single-arm interventional trial.

Fasting provokes fundamental changes in the activation of metabolic and signaling pathways leading to longer and healthier lifespans in animal models. Although the involvement of different metabolites in fueling human fasting metabolism is well known, the contribution of tissues and organs to their supply remains partly unclear. Also, changes in organ volume and composition remain relatively unexplored. Thus, processes involved in remodeling tissues during fasting and food reintroduction need to be better understood. Therefore, this study will apply state-of-the-art techniques to investigate the effects of long-term fasting (LF) and food reintroduction in humans by a multi-systemic approach focusing on changes in body composition, organ and tissue volume, lipid transport and storage, sources of protein utilization, blood metabolites, and gut microbiome profiles in a single cohort. This is a prospective, single-arm, monocentric trial. One hundred subjects will be recruited and undergo 9 ± 3 day-long fasting periods (250 kcal/day). We will assess changes in the composition of organs, bones and blood lipid profiles before and after fasting, as well as high-density lipoprotein (HDL) transport and storage, untargeted metabolomics of peripheral blood mononuclear cells (PBMCs), protein persulfidation and shotgun metagenomics of the gut microbiome. The first 32 subjects, fasting for 12 days, will be examined in more detail by magnetic resonance imaging (MRI) and spectroscopy to provide quantitative information on changes in organ volume and function, followed by an additional follow-up examination after 1 and 4 months. The study protocol was approved by the ethics board of the State Medical Chamber of Baden-Württemberg on 26.07.2021 and registered at ClinicalTrials.gov (NCT05031598). The results will be disseminated through peer-reviewed publications, international conferences and social media. Clinical trial registration: [ClinicalTrials.gov], identifier [NCT05031598].

The rise of Candida auris: from unique traits to co-infection potential.

Candida auris is a multidrug resistant (MDR) fungal pathogen with a crude mortality rate of 30-60%. First identified in 2009, C. auris has been rapidly emerging to become a global risk in clinical settings and was declared an urgent health threat by the Centers for Disease Control and Prevention (CDC). A concerted global action is thus needed to successfully tackle the challenges created by this emerging fungal pathogen. In this brief article, we underline the importance of unique virulence traits,including its easy transformation, its persistence outside the host and its resilience against multiple cellular stresses, as well as of environmental factors that have mainly contributed to the rise of this superbug.

Spermidine overrides INSR (insulin receptor)-IGF1R (insulin-like growth factor 1 receptor)-mediated inhibition of autophagy in the aging heart.

Although attenuated IGF1R (insulin-like growth factor 1 receptor) signaling has long been viewed to promote longevity in model organisms, adverse effects on the heart have been the subject of major concern. We observed that IGF1R is overexpressed in cardiac tissues from patients with end-stage non-ischemic heart failure, coupled to the activation of the IGF1R downstream effector AKT/protein kinase B and inhibition of ULK1 (unc-51 like autophagy activating kinase 1). Transgenic overexpression of human IGF1R in cardiomyocytes from mice initially induces physiological cardiac hypertrophy and superior function, but later in life confers a negative impact on cardiac health, causing macroautophagy/autophagy inhibition as well as impaired oxidative phosphorylation, thus reducing life expectancy. Treatment with the autophagy inducer and caloric restriction mimetic spermidine ameliorates most of these IGF1R-induced cardiotoxic effects in vivo. Moreover, inhibition of IGF1R signaling by means of a dominant-negative phosphoinositide 3-kinase (PI3K) mutant induces cardioprotective autophagy, restores myocardial bioenergetics and improves late-life survival. Hence, our results demonstrate that IGF1R exerts a dual biphasic impact on cardiac health, and that autophagy mediates the late-life geroprotective effects of IGF1R inhibition in the heart.

Fine-Tuning Cardiac Insulin-Like Growth Factor 1 Receptor Signaling to Promote Health and Longevity.

BACKGROUND: The insulin-like growth factor 1 (IGF1) pathway is a key regulator of cellular metabolism and aging. Although its inhibition promotes longevity across species, the effect of attenuated IGF1 signaling on cardiac aging remains controversial. METHODS: We performed a lifelong study to assess cardiac health and lifespan in 2 cardiomyocyte-specific transgenic mouse models with enhanced versus reduced IGF1 receptor (IGF1R) signaling. Male mice with human IGF1R overexpression or dominant negative phosphoinositide 3-kinase mutation were examined at different life stages by echocardiography, invasive hemodynamics, and treadmill coupled to indirect calorimetry. In vitro assays included cardiac histology, mitochondrial respiration, ATP synthesis, autophagic flux, and targeted metabolome profiling, and immunoblots of key IGF1R downstream targets in mouse and human explanted failing and nonfailing hearts, as well. RESULTS: Young mice with increased IGF1R signaling exhibited superior cardiac function that progressively declined with aging in an accelerated fashion compared with wild-type animals, resulting in heart failure and a reduced lifespan. In contrast, mice with low cardiac IGF1R signaling exhibited inferior cardiac function early in life, but superior cardiac performance during aging, and increased maximum lifespan, as well. Mechanistically, the late-life detrimental effects of IGF1R activation correlated with suppressed autophagic flux and impaired oxidative phosphorylation in the heart. Low IGF1R activity consistently improved myocardial bioenergetics and function of the aging heart in an autophagy-dependent manner. In humans, failing hearts, but not those with compensated hypertrophy, displayed exaggerated IGF1R expression and signaling activity. CONCLUSIONS: Our findings indicate that the relationship between IGF1R signaling and cardiac health is not linear, but rather biphasic. Hence, pharmacological inhibitors of the IGF1 pathway, albeit unsuitable for young individuals, might be worth considering in older adults.

Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adults With Subjective Cognitive Decline: A Randomized Clinical Trial.

Importance: Developing interventions against age-related memory decline and for older adults experiencing neurodegenerative disease is one of the greatest challenges of our generation. Spermidine supplementation has shown beneficial effects on brain and cognitive health in animal models, and there has been preliminary evidence of memory improvement in individuals with subjective cognitive decline. Objective: To determine the effect of longer-term spermidine supplementation on memory performance and biomarkers in this at-risk group. Design, Setting, and Participants: This 12-month randomized, double-masked, placebo-controlled phase 2b trial (the SmartAge trial) was conducted between January 2017 and May 2020. The study was a monocenter trial carried out at an academic clinical research center in Germany. Eligible individuals were aged 60 to 90 years with subjective cognitive decline who were recruited from health care facilities as well as through advertisements in the general population. Data analysis was conducted between January and March 2021. Interventions: One hundred participants were randomly assigned (1:1 ratio) to 12 months of dietary supplementation with either a spermidine-rich dietary supplement extracted from wheat germ (0.9 mg spermidine/d) or placebo (microcrystalline cellulose). Eighty-nine participants (89%) successfully completed the trial intervention. Main Outcomes and Measures: Primary outcome was change in memory performance from baseline to 12-month postintervention assessment (intention-to-treat analysis), operationalized by mnemonic discrimination performance assessed by the Mnemonic Similarity Task. Secondary outcomes included additional neuropsychological, behavioral, and physiological parameters. Safety was assessed in all participants and exploratory per-protocol, as well as subgroup, analyses were performed. Results: A total of 100 participants (51 in the spermidine group and 49 in the placebo group) were included in the analysis (mean [SD] age, 69 [5] years; 49 female participants [49%]). Over 12 months, no significant changes were observed in mnemonic discrimination performance (between-group difference, -0.03; 95% CI, -0.11 to 0.05; P = .47) and secondary outcomes. Exploratory analyses indicated possible beneficial effects of the intervention on inflammation and verbal memory. Adverse events were balanced between groups. Conclusions and Relevance: In this randomized clinical trial, longer-term spermidine supplementation in participants with subjective cognitive decline did not modify memory and biomarkers compared with placebo. Exploratory analyses indicated possible beneficial effects on verbal memory and inflammation that need to be validated in future studies at higher dosage. Trial Registration: ClinicalTrials.gov Identifier: NCT03094546.

A hundred spotlights on microbiology: how microorganisms shape our lives.

Viral, bacterial, fungal and protozoal biology is of cardinal importance for the evolutionary history of life, ecology, biotechnology and infectious diseases. Various microbiological model systems have fundamentally contributed to the understanding of molecular and cellular processes, including the cell cycle, cell death, mitochondrial biogenesis, vesicular fusion and autophagy, among many others. Microbial interactions within the environment have profound effects on many fields of biology, from ecological diversity to the highly complex and multifaceted impact of the microbiome on human health. Also, biotechnological innovation and corresponding industrial operations strongly depend on microbial engineering. With this wide range of impact in mind, the peer-reviewed and open access journal Microbial Cell was founded in 2014 and celebrates its 100th issue this month. Here, we briefly summarize how the vast diversity of microbiological subjects influences our personal and societal lives and shortly review the milestones achieved by Microbial Cell during the last years.

The HSP40 chaperone Ydj1 drives amyloid beta 42 toxicity.

Amyloid beta 42 (Abeta42) is the principal trigger of neurodegeneration during Alzheimer's disease (AD). However, the etiology of its noxious cellular effects remains elusive. In a combinatory genetic and proteomic approach using a yeast model to study aspects of intracellular Abeta42 toxicity, we here identify the HSP40 family member Ydj1, the yeast orthologue of human DnaJA1, as a crucial factor in Abeta42-mediated cell death. We demonstrate that Ydj1/DnaJA1 physically interacts with Abeta42 (in yeast and mouse), stabilizes Abeta42 oligomers, and mediates their translocation to mitochondria. Consequently, deletion of YDJ1 strongly reduces co-purification of Abeta42 with mitochondria and prevents Abeta42-induced mitochondria-dependent cell death. Consistently, purified DnaJ chaperone delays Abeta42 fibrillization in vitro, and heterologous expression of human DnaJA1 induces formation of Abeta42 oligomers and their deleterious translocation to mitochondria in vivo. Finally, downregulation of the Ydj1 fly homologue, Droj2, improves stress resistance, mitochondrial morphology, and memory performance in a Drosophila melanogaster AD model. These data reveal an unexpected and detrimental role for specific HSP40s in promoting hallmarks of Abeta42 toxicity.