Activation of genes involved in xenobiotic metabolism is a shared signature of mouse models with extended lifespan

The Role of Hypoxia in Longevity

Aging is marked by a progressive decrease in physiological function and reserve capacity, which results in increased susceptibility to diseases. Understanding the mechanisms of driving aging is crucial for extending health span and promoting human longevity. Hypoxia, marked by reduced oxygen availability, has emerged as a promising area of study within aging research. This review explores recent findings on the potential of oxygen restriction to promote healthy aging and extend lifespan. While the role of hypoxia-inducible factor 1 (HIF-1) in cellular responses to hypoxia is well-established, its impact on lifespan remains complex and context-dependent. Investigations in invertebrate models suggest a role for HIF-1 in longevity, while evidence in mammalian models is limited. Hypoxia extends the lifespan independent of dietary restriction (DR), a known intervention underlying longevity. However, both hypoxia and DR converge on common downstream effectors, such as forkhead box O (FOXO) and flavin-containing monooxygenase (FMOs) to modulate the lifespan. Further work is required to elucidate the molecular mechanisms underlying hypoxia-induced longevity and optimize clinical applications. Understanding the crosstalk between HIF-1 and other longevity-associated pathways is crucial for developing interventions to enhance lifespan and healthspan. Future studies may uncover novel therapeutic strategies to promote healthy aging and longevity in human populations.

fmo-4 promotes longevity and stress resistance via ER to mitochondria calcium regulation in C. elegans

Flavin-containing monooxygenases (FMOs) are a conserved family of xenobiotic enzymes upregulated in multiple longevity interventions, including nematode and mouse models. Previous work supports that C. elegans fmo-2 promotes longevity, stress resistance, and healthspan by rewiring endogenous metabolism. However, there are five C. elegans FMOs and five mammalian FMOs, and it is not known whether promoting longevity and health benefits is a conserved role of this gene family. Here, we report that expression of C. elegans fmo-4 promotes lifespan extension and paraquat stress resistance downstream of both dietary restriction and inhibition of mTOR. We find that overexpression of fmo-4 in just the hypodermis is sufficient for these benefits, and that this expression significantly modifies the transcriptome. By analyzing changes in gene expression, we find that genes related to calcium signaling are significantly altered downstream of fmo-4 expression. Highlighting the importance of calcium homeostasis in this pathway, fmo-4 overexpressing animals are sensitive to thapsigargin, an ER stressor that inhibits calcium flux from the cytosol to the ER lumen. This calcium/fmo-4 interaction is solidified by data showing that modulating intracellular calcium with either small molecules or genetics can change expression of fmo-4 and/or interact with fmo-4 to affect lifespan and stress resistance. Further analysis supports a pathway where fmo-4 modulates calcium homeostasis downstream of activating transcription factor-6 (atf-6), whose knockdown induces and requires fmo-4 expression. Together, our data identify fmo-4 as a longevity-promoting gene whose actions interact with known longevity pathways and calcium homeostasis.

fmo-4 promotes longevity and stress resistance via ER to mitochondria calcium regulation in C. elegans

Flavin-containing monooxygenases (FMOs) are a conserved family of xenobiotic enzymes upregulated in multiple longevity interventions, including nematode and mouse models. Previous work supports that C. elegans fmo-2 promotes longevity, stress resistance, and healthspan by rewiring endogenous metabolism. However, there are five C. elegans FMOs and five mammalian FMOs, and it is not known whether promoting longevity and health benefits is a conserved role of this gene family. Here, we report that expression of C. elegans fmo-4 promotes lifespan extension and paraquat stress resistance downstream of both dietary restriction and inhibition of mTOR. We find that overexpression of fmo-4 in just the hypodermis is sufficient for these benefits, and that this expression significantly modifies the transcriptome. By analyzing changes in gene expression, we find that genes related to calcium signaling are significantly altered downstream of fmo-4 expression. Highlighting the importance of calcium homeostasis in this pathway, fmo-4 overexpressing animals are sensitive to thapsigargin, an ER stressor that inhibits calcium flux from the cytosol to the ER lumen. This calcium/fmo-4 interaction is solidified by data showing that modulating intracellular calcium with either small molecules or genetics can change expression of fmo-4 and/or interact with fmo-4 to affect lifespan and stress resistance. Further analysis supports a pathway where fmo-4 modulates calcium homeostasis downstream of activating transcription factor-6 (atf-6), whose knockdown induces and requires fmo-4 expression. Together, our data identify fmo-4 as a longevity-promoting gene whose actions interact with known longevity pathways and calcium homeostasis.

Isotschimgine promotes lifespan, healthspan and neuroprotection of Caenorhabditis elegans via the activation of nuclear hormone receptors

Isotschimgine (ITG) is a bornane-type monoterpenoid derivative naturally occurring in genus Ferula plants and propolis. Its effects on aging and the underlying mechanisms are not yet well understood. This study employed Caenorhabditis elegans (C. elegans) as a model organism to evaluate the potential of ITG in extending lifespan, enhancing healthspan, and promoting neuroprotection, while exploring the underlying mechanisms involved. The results showed that ITG extended the lifespan and healthspan of C. elegans, significantly enhanced stress resistance and detoxification functions. Studies on mutants and qPCR data indicated that ITG-mediated lifespan extension was modulated by the insulin/IGF-1 signaling pathway and nuclear hormone receptors. Furthermore, ITG markedly increased stress-responsive genes, including daf-16 and its downstream genes sod-3 and hsp-16.2, as well as NHR downstream detoxification-related genes cyp35a1, cyp35b3, cyp35c1, gst-4, pgp-3 and pgp-13. Additionally, ITG alleviated β-amyloid-induced paralysis and behavioral dysfunction in transgenic C. elegans strains. The neuroprotective efficacy of ITG was weakened by RNAi knockdown of nuclear hormone receptors daf-12 and nhr-8. Overall, our study identifies ITG as a potential compound for promoting longevity and neuroprotection, mediated through nuclear hormone receptors.

Fmo induction as a tool to screen for pro-longevity drugs

Dietary restriction (DR) and hypoxia (low oxygen) extend lifespan in Caenorhabditis elegans through the induction of a convergent downstream longevity gene, fmo-2. Flavin-containing monooxygenases (FMOs) are highly conserved xenobiotic-metabolizing enzymes with a clear role in promoting longevity in nematodes and a plausible similar role in mammals. This makes them an attractive potential target of small molecule drugs to stimulate the health-promoting effects of longevity pathways. Here, we utilize an fmo-2 fluorescent transcriptional reporter in C. elegans to screen a set of 80 compounds previously shown to improve stress resistance in mouse fibroblasts. Our data show that 19 compounds significantly induce fmo-2, and 10 of the compounds induce fmo-2 more than twofold. Interestingly, 9 of the 10 high fmo-2 inducers also extend lifespan in C. elegans. Two of these drugs, mitochondrial respiration chain complex inhibitors, interact with the hypoxia pathway to induce fmo-2, whereas two dopamine receptor type 2 (DRD2) antagonists interact with the DR pathway to induce fmo-2, indicating that dopamine signaling is involved in DR-mediated fmo-2 induction. Together, our data identify nine drugs that each (1) increase stress resistance in mouse fibroblasts, (2) induce fmo-2 in C. elegans, and (3) extend nematode lifespan, some through known longevity pathways. These results define fmo-2 induction as a viable approach to identifying and understanding mechanisms of putative longevity compounds.

Maternal α-casein deficiency extends the lifespan of offspring and programmes their body composition

Early nutrition has significant effects on physiological outcomes during adult life. We have analysed the effect of maternal α-casein (CSN1S1) deficiency on the physiological fate of dams and their offspring. α-casein deficiency reduces maternal milk protein concentration by more than 50% and attenuates the growth of pups to 27% (p < 0.001) of controls at the point of weaning. This is associated with a permanent reduction in adult body weight (- 31% at 25 weeks). Offspring nursed by α-casein deficient dams showed a significantly increased lifespan (+ 20%, χ2: 10.6; p = 0.001). Liver transcriptome analysis of offspring nursed by α-casein deficient dams at weaning revealed gene expression patterns similar to those found in dwarf mice (reduced expression of somatotropic axis signalling genes, increased expression of xenobiotic metabolism genes). In adult mice, the expression of somatotropic axis genes returned to control levels. This demonstrates that, in contrast to dwarf mice, attenuation of the GH-IGF signalling axis in offspring nursed by α-casein deficient dams is transient, while the changes in body size and lifespan are permanent. Offspring nursed by α-casein deficient dams showed permanent changes in body composition. Absolute and relative adipose tissue weights (p < 0.05), the percentage of body fat (p < 0.001) as well as adipocyte size in epididymal white adipose tissue are all reduced. Serum leptin levels were 25% of those found in control mice (p < 0.001). Liver lipid content and lipid composition were significantly altered in response to postnatal nutrition. This demonstrates the nutrition in early life programmes adult lipid metabolism, body composition and lifespan.

The Roles of White Adipose Tissue and Liver NADPH in Dietary Restriction-Induced Longevity

Dietary restriction (DR) protocols frequently employ intermittent fasting. Following a period of fasting, meal consumption increases lipogenic gene expression, including that of NADPH-generating enzymes that fuel lipogenesis in white adipose tissue (WAT) through the induction of transcriptional regulators SREBP-1c and CHREBP. SREBP-1c knockout mice, unlike controls, did not show an extended lifespan on the DR diet. WAT cytoplasmic NADPH is generated by both malic enzyme 1 (ME1) and the pentose phosphate pathway (PPP), while liver cytoplasmic NADPH is primarily synthesized by folate cycle enzymes provided one-carbon units through serine catabolism. During the daily fasting period of the DR diet, fatty acids are released from WAT and are transported to peripheral tissues, where they are used for beta-oxidation and for phospholipid and lipid droplet synthesis, where monounsaturated fatty acids (MUFAs) may activate Nrf1 and inhibit ferroptosis to promote longevity. Decreased WAT NADPH from PPP gene knockout stimulated the browning of WAT and protected from a high-fat diet, while high levels of NADPH-generating enzymes in WAT and macrophages are linked to obesity. But oscillations in WAT [NADPH]/[NADP+] from feeding and fasting cycles may play an important role in maintaining metabolic plasticity to drive longevity. Studies measuring the WAT malate/pyruvate as a proxy for the cytoplasmic [NADPH]/[NADP+], as well as studies using fluorescent biosensors expressed in the WAT of animal models to monitor the changes in cytoplasmic [NADPH]/[NADP+], are needed during ad libitum and DR diets to determine the changes that are associated with longevity.

Flavin-containing monooxygenase (FMO): Beyond xenobiotics

Flavin-containing monooxygenases (FMOs), traditionally known for detoxifying xenobiotics, are now recognized for their involvement in endogenous metabolism. We recently discovered that an isoform of FMO, fmo-2 in Caenorhabditis elegans, alters endogenous metabolism to impact longevity and stress tolerance. Increased expression of fmo-2 in C. elegans modifies the flux through the key pathway known as One Carbon Metabolism (OCM). This modified flux results in a decrease in the ratio of S-adenosyl-methionine (SAM) to S-adenosyl-homocysteine (SAH), consequently diminishing methylation capacity. Here we discuss how FMO-2-mediated formate production during tryptophan metabolism may serve as a trigger for changing the flux in OCM. We suggest formate bridges tryptophan and OCM, altering metabolic flux away from methylation during fmo-2 overexpression. Additionally, we highlight how these metabolic results intersect with the mTOR and AMPK pathways, in addition to mitochondrial metabolism. In conclusion, the goal of this essay is to bring attention to the central role of FMO enzymes but lack of understanding of their mechanisms. We justify a call for a deeper understanding of FMO enzyme's role in metabolic rewiring through tryptophan/formate or other yet unidentified substrates. Additionally, we emphasize the identification of novel drugs and microbes to induce FMO activity and extend lifespan.

Proteomic changes induced by longevity-promoting interventions in mice

Using mouse models and high-throughput proteomics, we conducted an in-depth analysis of the proteome changes induced in response to seven interventions known to increase mouse lifespan. This included two genetic mutations, a growth hormone receptor knockout (GHRKO mice) and a mutation in the Pit-1 locus (Snell dwarf mice), four drug treatments (rapamycin, acarbose, canagliflozin, and 17α-estradiol), and caloric restriction. Each of the interventions studied induced variable changes in the concentrations of proteins across liver, kidney, and gastrocnemius muscle tissue samples, with the strongest responses in the liver and limited concordance in protein responses across tissues. To the extent that these interventions promote longevity through common biological mechanisms, we anticipated that proteins associated with longevity could be identified by characterizing shared responses across all or multiple interventions. Many of the proteome alterations induced by each intervention were distinct, potentially implicating a variety of biological pathways as being related to lifespan extension. While we found no protein that was affected similarly by every intervention, we identified a set of proteins that responded to multiple interventions. These proteins were functionally diverse but tended to be involved in peroxisomal oxidation and metabolism of fatty acids. These results provide candidate proteins and biological mechanisms related to enhancing longevity that can inform research on therapeutic approaches to promote healthy aging.

Abalone peptide increases stress resilience and cost-free longevity via SKN-1-governed transcriptional metabolic reprogramming in C. elegans

A major goal of healthy aging is to prevent declining resilience and increasing frailty, which are associated with many chronic diseases and deterioration of stress response. Here, we propose a loss-or-gain survival model, represented by the ratio of cumulative stress span to life span, to quantify stress resilience at organismal level. As a proof of concept, this is demonstrated by reduced survival resilience in Caenorhabditis elegans exposed to exogenous oxidative stress induced by paraquat or with endogenous proteotoxic stress caused by polyglutamine or amyloid-β aggregation. Based on this, we reveal that a hidden peptide ("cryptide")-AbaPep#07 (SETYELRK)-derived from abalone hemocyanin not only enhances survival resilience against paraquat-induced oxidative stress but also rescues proteotoxicity-mediated behavioral deficits in C. elegans, indicating its capacity against stress and neurodegeneration. Interestingly, AbaPep#07 is also found to increase cost-free longevity and age-related physical fitness in nematodes. We then demonstrate that AbaPep#07 can promote nuclear localization of SKN-1/Nrf, but not DAF-16/FOXO, transcription factor. In contrast to its effects in wild-type nematodes, AbaPep#07 cannot increase oxidative stress survival and physical motility in loss-of-function skn-1 mutant, suggesting an SKN-1/Nrf-dependent fashion of these effects. Further investigation reveals that AbaPep#07 can induce transcriptional activation of immune defense, lipid metabolism, and metabolic detoxification pathways, including many SKN-1/Nrf target genes. Together, our findings demonstrate that AbaPep#07 is able to boost stress resilience and reduce behavioral frailty via SKN-1/Nrf-governed transcriptional reprogramming, and provide an insight into the health-promoting potential of antioxidant cryptides as geroprotectors in aging and associated conditions.

Epigenetic regulation of drug metabolism in aging: utilizing epigenetics to optimize geriatric pharmacotherapy

We explore the relationship between epigenetic aging and drug metabolism. We review current evidence for changes in drug metabolism in normal aging, followed by a description of how epigenetic modifications associated with age can regulate the expression and functionality of genes. In particular, we focus on the role of epigenome-wide studies of human and mouse liver in understanding these age-related processes with respect to xenobiotic processing. We highlight genes encoding drug metabolizing enzymes and transporters revealed to be affected by epigenetic aging in these studies. We conclude that substantial evidence exists for epigenetic aging impacting drug metabolism and transport genes, but more work is needed. We further highlight the promise of pharmacoepigenetics applied to enhancing drug safety in older adults.

GHR disruption in mature adult mice alters xenobiotic metabolism gene expression in the liver

BACKGROUND

Lifelong reduction of growth hormone (GH) action extends lifespan and improves healthspan in mice. Moreover, congenital inactivating mutations of GH receptor (GHR) in mice and humans impart resistance to age-associated cancer, diabetes, and cognitive decline. To investigate the consequences of GHR disruption at an adult age, we recently ablated the GHR at 6-months of age in mature adult (6mGHRKO) mice. We found that both, male and female 6mGHRKO mice have reduced oxidative damage, with males 6mGHRKO showing improved insulin sensitivity and cancer resistance. Importantly, 6mGHRKO females have an extended lifespan compared to controls.

OBJECTIVE AND METHODS

To investigate the possible mechanisms leading to health improvements, we performed RNA sequencing using livers from male and female 6mGHRKO mice and controls.

RESULTS

We found that disrupting GH action at an adult age reduced the gap in liver gene expression between males and females, making gene expression between sexes more similar. However, there was still a 6-fold increase in the number of differentially expressed genes when comparing male 6mGHRKO mice vs controls than in 6mGHRKO female vs controls, suggesting that GHR ablation affects liver gene expression more in males than in females. Finally, we found that lipid metabolism and xenobiotic metabolism pathways are activated in the liver of 6mGHRKO mice.

CONCLUSION

The present study shows for the first time the specific hepatic gene expression profile, cellular pathways, biological processes and molecular mechanisms that are driven by ablating GH action at a mature adult age in males and females. Importantly, these results and future studies on xenobiotic metabolism may help explain the lifespan extension seen in 6mGHRKO mice.

The Effects of Graded Levels of Calorie Restriction: XIX. Impact of Graded Calorie Restriction on Protein Expression in the Liver

Calorie restriction (CR) extends life span by modulating the mechanisms involved in aging. We quantified the hepatic proteome of male C57BL/6 mice exposed to graded levels of CR (0%-40% CR) for 3 months, and evaluated which signaling pathways were most affected. The metabolic pathways most significantly stimulated by the increase in CR, included the glycolysis/gluconeogenesis pathway, the pentose phosphate pathway, the fatty acid degradation pathway, the valine, leucine, and isoleucine degradation pathway, and the lysine degradation pathway. The metabolism of xenobiotics by cytochrome P450 pathway was activated and feminized by increased CR, while production in major urinary proteins (Mups) was strongly reduced, consistent with a reduced investment in reproduction as predicted by the disposable soma hypothesis. However, we found no evidence of increased somatic protection, and none of the 4 main pathways implied to be linked to the impact of CR on life span (insulin/insulin-like growth factor [IGF-1], nuclear factor-κB [NF-κB], mammalian Target of Rapamycin [mTOR], and sirtuins) as well as pathways in cancer, were significantly changed at the protein level in relation to the increase in CR level. This was despite previous work at the transcriptome level in the same individuals indicating such changes. On the other hand, we found Aldh2, Aldh3a2, and Aldh9a1 in carnitine biosynthesis and Acsl5 in carnitine shuttle system were up-regulated by increased CR, which are consistent with our previous work on metabolome of the same individuals. Overall, the patterns of protein expression were more consistent with a "clean cupboards" than a "disposable soma" interpretation.

Pregnane X receptor agonist nomilin extends lifespan and healthspan in preclinical models through detoxification functions

Citrus fruit has long been considered a healthy food, but its role and detailed mechanism in lifespan extension are not clear. Here, by using the nematode C. elegans, we identified that nomilin, a bitter-taste limoloid that is enriched in citrus, significantly extended the animals' lifespan, healthspan, and toxin resistance. Further analyses indicate that this ageing inhibiting activity depended on the insulin-like pathway DAF-2/DAF-16 and nuclear hormone receptors NHR-8/DAF-12. Moreover, the human pregnane X receptor (hPXR) was identified as the mammalian counterpart of NHR-8/DAF-12 and X-ray crystallography showed that nomilin directly binds with hPXR. The hPXR mutations that prevented nomilin binding blocked the activity of nomilin both in mammalian cells and in C. elegans. Finally, dietary nomilin supplementation improved healthspan and lifespan in D-galactose- and doxorubicin-induced senescent mice as well as in male senescence accelerated mice prone 8 (SAMP8) mice, and induced a longevity gene signature similar to that of most longevity interventions in the liver of bile-duct-ligation male mice. Taken together, we identified that nomilin may extend lifespan and healthspan in animals via the activation of PXR mediated detoxification functions.

Resistance to mild cold stress is greater in both wild-type and long-lived GHR-KO female mice

Adapting to stress, including cold environmental temperature (eT), is crucial for the survival of mammals, especially small rodents. Long-lived mutant mice have enhanced stress resistance against oxidative and non-oxidative challenges. However, much less is known about the response of those long-lived mice to cold stress. Growth hormone receptor knockout (GHR-KO) mice are long-lived with reduced growth hormone signaling. We wanted to test whether GHR-KO mice have enhanced resistance to cold stress. To examine the response of GHR-KO mice to cold eT, GHR-KO mice were housed at mild cold eT (16 °C) immediately following weaning. Longevity results showed that female GHR-KO and wild-type (WT) mice retained similar lifespan, while both male GHR-KO and WT mice had shortened lifespan compared to the mice housed at 23 °C eT. Female GHR-KO and WT mice housed at 16 °C had upregulated fibroblast growth factor 21 (FGF21), enhanced energy metabolism, reduced plasma triglycerides, and increased mRNA expression of some xenobiotic enzymes compared to females housed at 23 °C and male GHR-KO and WT mice housed under the same condition. In contrast, male GHR-KO and WT mice housed at 16 °C showed deleterious effects in parameters which might be associated with their shortened longevity compared to male GHR-KO and WT mice housed at 23 °C. Together, this study suggests that in response to mild cold stress, sex plays a pivotal role in the regulation of longevity, and female GHR-KO and WT mice are more resistant to this challenge than the males.

FMO rewires metabolism to promote longevity through tryptophan and one carbon metabolism in C. elegans

Flavin containing monooxygenases (FMOs) are promiscuous enzymes known for metabolizing a wide range of exogenous compounds. In C. elegans, fmo-2 expression increases lifespan and healthspan downstream of multiple longevity-promoting pathways through an unknown mechanism. Here, we report that, beyond its classification as a xenobiotic enzyme, fmo-2 expression leads to rewiring of endogenous metabolism principally through changes in one carbon metabolism (OCM). These changes are likely relevant, as we find that genetically modifying OCM enzyme expression leads to alterations in longevity that interact with fmo-2 expression. Using computer modeling, we identify decreased methylation as the major OCM flux modified by FMO-2 that is sufficient to recapitulate its longevity benefits. We further find that tryptophan is decreased in multiple mammalian FMO overexpression models and is a validated substrate for FMO-2. Our resulting model connects a single enzyme to two previously unconnected key metabolic pathways and provides a framework for the metabolic interconnectivity of longevity-promoting pathways such as dietary restriction. FMOs are well-conserved enzymes that are also induced by lifespan-extending interventions in mice, supporting a conserved and important role in promoting health and longevity through metabolic remodeling.

Convergent genomics of longevity in rockfishes highlights the genetics of human life span variation

Longevity is a defining, heritable trait that varies dramatically between species. To resolve the genetic regulation of this trait, we have mined genomic variation in rockfishes, which range in longevity from 11 to over 205 years. Multiple shifts in rockfish longevity have occurred independently and in a short evolutionary time frame, thus empowering convergence analyses. Our analyses reveal a common network of genes under convergent evolution, encompassing established aging regulators such as insulin signaling, yet also identify flavonoid (aryl-hydrocarbon) metabolism as a pathway modulating longevity. The selective pressures on these pathways indicate the ancestral state of rockfishes was long lived and that the changes in short-lived lineages are adaptive. These pathways were also used to explore genome-wide association studies of human longevity, identifying the aryl-hydrocarbon metabolism pathway to be significantly associated with human survival to the 99th percentile. This evolutionary intersection defines and cross-validates a previously unappreciated genetic architecture that associates with the evolution of longevity across vertebrates.

The Aryl Hydrocarbon Receptor, Epigenetics and the Aging Process

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor, classically associated with the regulation of xenobiotic metabolism in response to environmental toxins. In recent years, transgenic rodent models have implicated AhR in aging and longevity. Moreover, several AhR ligands, such as resveratrol and quercetin, are compounds proven to extend the lifespan of model organisms. In this paper, we first review AhR biology with a focus on aging and highlight several AhR ligands with potential anti-aging properties. We outline how AhR-driven expression of xenobiotic metabolism genes into old age may be a key mechanism through which moderate induction of AhR elicits positive benefits on longevity and healthspan. Furthermore, via integration of publicly available datasets, we show that liver-specific AhR target genes are enriched among genes subject to epigenetic aging. Changes to epigenetic states can profoundly affect transcription factor binding and are a hallmark of the aging process. We suggest that the interplay between AhR and epigenetic aging should be the subject of future research and outline several key gaps in the current literature. Finally, we recommend that a broad range of non-toxic AhR ligands should be investigated for their potential to promote healthspan and longevity.

Soft-Shelled Turtle Peptides Extend Lifespan and Healthspan in Drosophila

In traditional Chinese medicine, soft-shelled turtle protein and peptides serve as a nutraceutical for prolonging the lifespan. However, their effects on anti-aging have not been clarified scientifically in vivo. This study aimed to determine whether soft-shelled turtle peptides (STP) could promote the lifespan and healthspan in Drosophila melanogaster and the underlying molecular mechanisms. Herein, STP supplementation prolonged the mean lifespan by 20.23% and 9.04% in males and females, respectively, delaying the aging accompanied by climbing ability decline, enhanced gut barrier integrity, and improved anti-oxidation, starvation, and heat stress abilities, while it did not change the daily food intake. Mechanistically, STP enhanced autophagy and decreased oxidative stress by downregulating the target of rapamycin (TOR) signaling pathway. In addition, 95.18% of peptides from the identified sequences in STP could exert potential inhibitory effects on TOR through hydrogen bonds, van der Walls, hydrophobic interactions, and electrostatic interactions. The current study could provide a theoretical basis for the full exploitation of soft-shelled turtle aging prevention.

In silico identification of the potential molecular mechanisms involved in protective effects of prolactin on motor and memory deficits induced by 1,2-Diacetylbenzene in young and old rats

We aimed to identify the molecular mechanisms through which prolactin protects against 1,2-Diacetylbenzene (DAB)-induced memory and motor impairments. The gene expression omnibus database (no. GSE119435), transcriptomic data, GeneMANIA, ToppGeneSuite, Metascape, STRING database, Cytoscape, and Autodock were used as the core tools in in-silico analyses. We observed that prolactin may improve memory and motor deficits caused by DAB via 13 genes (Scn5a, Lmntd1, LOC100360619, Rgs9, Srpk3, Syndig1l, Gpr88, Egr2, Ctxn3, Drd2, Ttr, Gpr6, and Ecel1) in young rats and 9 genes (Scn5a, Chat, RGD1560608, Ucma, Lrrc31, Gpr88, Col1a2, Cnbd1, and Ttr) in old rats. Almost all of these genes were downregulated in both young and old rats given DAB, but they were increased in both young and old rats given prolactin. Co-expression interactions were identified as the most important interactions (83.2 % for young rats and 100 % for old rats). The most important mechanisms associated with prolactin's ability to counteract DAB were identified, including "learning and memory," and "positive regulation of ion transport" in young rats, as well as "acetylcholine related pathways," "inflammatory response pathway," and "neurotransmitter release cycle" in old rats. We also identified several key miRNAs associated with memory and motor deficits, as well as prolactin and DAB exposure (rno-miR-141-3p, rno-miR-200a-3p, rno-miR-124-3p, rno-miR-26, and rno-let-7 families). The most significant transcription factors associated with differentially expressed gene regulation were Six3, Rxrg, Nkx26, and Tbx20. These findings will contribute to our understanding of the processes through which prolactin's beneficial effects counteract DAB-induced memory and motor deficits.

Serotonin and dopamine modulate aging in response to food odor and availability

An organism's ability to perceive and respond to changes in its environment is crucial for its health and survival. Here we reveal how the most well-studied longevity intervention, dietary restriction, acts in-part through a cell non-autonomous signaling pathway that is inhibited by the presence of attractive smells. Using an intestinal reporter for a key gene induced by dietary restriction but suppressed by attractive smells, we identify three compounds that block food odor effects in C. elegans, thereby increasing longevity as dietary restriction mimetics. These compounds clearly implicate serotonin and dopamine in limiting lifespan in response to food odor. We further identify a chemosensory neuron that likely perceives food odor, an enteric neuron that signals through the serotonin receptor 5-HT1A/SER-4, and a dopaminergic neuron that signals through the dopamine receptor DRD2/DOP-3. Aspects of this pathway are conserved in D. melanogaster. Thus, blocking food odor signaling through antagonism of serotonin or dopamine receptors is a plausible approach to mimic the benefits of dietary restriction.

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.

Characterization of an in vitro 3D intestinal organoid model by using massive RNAseq-based transcriptome profiling

Organoids culture provides unique opportunities to study human diseases and to complement animal models. Several organs and tissues can be in vitro cultured in 3D structures resembling in vivo tissue organization. Organoids culture contains most of the cell types of the original tissue and are maintained by growth factors mimicking the in vivo state. However, the system is yet not fully understood, and specific in vivo features especially those driven by cell-extrinsic factors may be lost in culture. Here we show a comprehensive transcriptome-wide characterization of mouse gut organoids derived from different intestinal compartments and from mice of different gender and age. RNA-seq analysis showed that the in vitro culture strongly influences the global transcriptome of the intestinal epithelial cells (~ 60% of the total variance). Several compartment-, age- and gender-related transcriptome features are lost after culturing indicating that they are driven by niche or systemic factors. However, certain intrinsic transcriptional programs, for example, some compartment-related features and a minority of gender- and aging- related features are maintained in vitro which suggested possibilities for these features to be studied in this system. Moreover, our study provides knowledge about the cell-extrinsic or cell-intrinsic origin of intestinal epithelial transcriptional programs. We anticipated that our characterization of this in vitro system is an important reference for scientists and clinicians using intestinal organoids as a research model.

National Institute on Aging Workshop: Repurposing Drugs or Dietary Supplements for Their Senolytic or Senomorphic Effects: Considerations for Clinical Trials

BACKGROUND

Cell senescence is implicated in numerous age-related conditions. Drugs and nutritional supplements developed for a variety of purposes kill senescent cells (senolytics) or suppress their secretions (senomorphics). There is interest in repurposing such drugs to treat or prevent age-related diseases. To date, only small-scale preliminary trials have been conducted.

METHOD

At a workshop convened by the National Institute on Aging in August 2019, academic, industry, and government scientists reviewed issues for phase II trials of potentially repurposable drugs, or dietary supplements, to assess benefits and risks of their senolytic (killing senescent cells) or senomorphic (altering senescent cells' phenotypes) effects in treating or preventing age-related conditions.

RESULTS

Participants reviewed mechanisms and effects of cellular senescence, senolytics, and senomorphics of several classes and their potential role in treating or preventing disease, modulators of the senescence-associated secretory phenotype, needs for senescence markers, data and specimen resources, infrastructure for planning trials, and potential effects on outcomes in older patients with multimorbidity and polypharmacy.

CONCLUSIONS

Participants noted the importance of considering potential effects of candidate drugs on multiple aging outcomes. It is important to assess drugs' specificity for killing senescent cells and the balance between senolytic and cytotoxic effects. Markers of specific senescent cell types are needed to assess intervention responses. There are potential interactions with coexisting diseases and their treatments in older persons. Standardized measures could enhance comparisons and pooling of data. Additional characterization of human cell senescent phenotypes is needed for developing better and more specific senolytics and senomorphics.

Mouse models of growth hormone deficiency

Nearly one century of research using growth hormone deficient (GHD) mouse lines has contributed greatly toward our knowledge of growth hormone (GH), a pituitary-derived hormone that binds and signals through the GH receptor and affects many metabolic processes throughout life. Although delayed sexual maturation, decreased fertility, reduced muscle mass, increased adiposity, small body size, and glucose intolerance appear to be among the negative characteristics of these GHD mouse lines, these mice still consistently outlive their normal sized littermates. Furthermore, the absence of GH action in these mouse lines leads to enhanced insulin sensitivity (likely due to the lack of GH's diabetogenic actions), delayed onset for a number of age-associated physiological declines (including cognition, cancer, and neuromusculoskeletal frailty), reduced cellular senescence, and ultimately, extended lifespan. In this review, we provide details about history, availability, growth, physiology, and aging of five commonly used GHD mouse lines.

Flavin-Containing Monooxygenases Are Conserved Regulators of Stress Resistance and Metabolism

Flavin-Containing Monooxygenases are conserved xenobiotic-detoxifying enzymes. Recent studies have revealed endogenous functions of FMOs in regulating longevity in Caenorhabditis elegans and in regulating aspects of metabolism in mice. To explore the cellular mechanisms of FMO's endogenous function, here we demonstrate that all five functional mammalian FMOs may play similar endogenous roles to improve resistance to a wide range of toxic stresses in both kidney and liver cells. We further find that stress-activated c-Jun N-terminal kinase activity is enhanced in FMO-overexpressing cells, which may lead to increased survival under stress. Furthermore, FMO expression modulates cellular metabolic activity as measured by mitochondrial respiration, glycolysis, and metabolomics analyses. FMO expression augments mitochondrial respiration and significantly changes central carbon metabolism, including amino acid and energy metabolism pathways. Together, our findings demonstrate an important endogenous role for the FMO family in regulation of cellular stress resistance and major cellular metabolic activities including central carbon metabolism.

Cell non-autonomous regulation of health and longevity

As the demographics of the modern world skew older, understanding and mitigating the effects of aging is increasingly important within biomedical research. Recent studies in model organisms demonstrate that the aging process is frequently modified by an organism’s ability to perceive and respond to changes in its environment. Many well-studied pathways that influence aging involve sensory cells, frequently neurons, that signal to peripheral tissues and promote survival during the presence of stress. Importantly, this activation of stress response pathways is often sufficient to improve health and longevity even in the absence of stress. Here, we review the current landscape of research highlighting the importance of cell non-autonomous signaling in modulating aging from C. elegans to mammals. We also discuss emerging concepts including retrograde signaling, approaches to mapping these networks, and development of potential therapeutics.

Polyunsaturated fatty acids and p38-MAPK link metabolic reprogramming to cytoprotective gene expression during dietary restriction

The metabolic state of an organism instructs gene expression modalities, leading to changes in complex life history traits, such as longevity. Dietary restriction (DR), which positively affects health and life span across species, leads to metabolic reprogramming that enhances utilisation of fatty acids for energy generation. One direct consequence of this metabolic shift is the upregulation of cytoprotective (CyTP) genes categorized in the Gene Ontology (GO) term of "Xenobiotic Detoxification Program" (XDP). How an organism senses metabolic changes during nutritional stress to alter gene expression programs is less known. Here, using a genetic model of DR, we show that the levels of polyunsaturated fatty acids (PUFAs), especially linoleic acid (LA) and eicosapentaenoic acid (EPA), are increased following DR and these PUFAs are able to activate the CyTP genes. This activation of CyTP genes is mediated by the conserved p38 mitogen-activated protein kinase (p38-MAPK) pathway. Consequently, genes of the PUFA biosynthesis and p38-MAPK pathway are required for multiple paradigms of DR-mediated longevity, suggesting conservation of mechanism. Thus, our study shows that PUFAs and p38-MAPK pathway function downstream of DR to help communicate the metabolic state of an organism to regulate expression of CyTP genes, ensuring extended life span.

Stress Resistance Screen in a Human Primary Cell Line Identifies Small Molecules That Affect Aging Pathways and Extend Caenorhabditis elegans' Lifespan

Increased resistance to environmental stress at the cellular level is correlated with the longevity of long-lived mutants and wild-animal species. Moreover, in experimental organisms, screens for increased stress resistance have yielded mutants that are long-lived. To find entry points for small molecules that might extend healthy longevity in humans, we screened ∼100,000 small molecules in a human primary-fibroblast cell line and identified a set that increased oxidative-stress resistance. Some of the hits fell into structurally related chemical groups, suggesting that they may act on common targets. Two small molecules increased C. elegans’ stress resistance, and at least 9 extended their lifespan by ∼10–50%. We further evaluated a chalcone that produced relatively large effects on lifespan and were able to implicate the activity of two, stress-response regulators, NRF2/skn-1 and SESN/sesn-1, in its mechanism of action. Our findings suggest that screening for increased stress resistance in human cells can enrich for compounds with promising pro-longevity effects. Further characterization of these compounds may reveal new ways to extend healthy human lifespan.

A cell-based assay system for activators of the environmental cell stress response

Improved health span and lifespan extension in a wide phylogenetic range of species is associated with the induction of the environmental cell stress response through a signalling pathway regulated by the transcription factor Nrf2. Phytochemicals which stimulate this response may form part of therapeutic interventions which stimulate endogenous cytoprotective mechanisms, thereby delaying the onset of age-related diseases and promoting healthy ageing in humans. In order to identify compounds that activate the Nrf2 pathway, a cell-based reporter system was established in HepG2 cells using a luciferase reporter gene under the control of the Nqo1 promoter. Sulforaphane, an isothiocyanate derived from cruciferous vegetables and a known activator of the Nrf2 pathway, was used to validate the reporter system. The transfected cell line HepG2 C1 was subsequently used to screen natural product libraries. Five compounds were identified as activating the bioluminescent reporter by greater than 5-fold. The two most potent compounds, MBC20 and MBC37, were further characterised and shown to stimulate endogenous cytoprotective gene and protein expression. The bioluminescent reporter system will allow rapid, in vitro identification of novel compounds that have the potential to improve health span through activation of the environmental stress response.

Upregulation of flavin-containing monooxygenase 3 mimics calorie restriction to retard liver aging by inducing autophagy

Flavin-containing monooxygenase 3 (FMO3) gene expression is often upregulated in long-lived murine models. However, the specific relationship between FMO3 and aging remains unknown. Here, we show that 40% calorie restriction (CR), which is considered to be one of the most robust interventions to delay aging progression, markedly upregulates FMO3. Most importantly, upregulation of hepatocyte FMO3 in murine models prevented or reversed hepatic aging. Accordingly, the upregulation of FMO3 mimicked the effects of CR: reduced serum levels of pro-inflammatory cytokine interleukin-6 and fasting insulin; relief of oxidative stress, with lower hepatic malondialdehyde levels and higher superoxide dismutase activity; reduced serum and hepatic levels of total cholesterol and triglyceride, as well as reduced lipid deposition in the liver; and diminished levels of aging-related markers β-gal and p16. There were also synergistic effects between FMO3 upregulation and CR. Inhibition of autophagy blocked the anti-aging effects of upregulation of hepatocyte FMO3, including reversing the amelioration of the serum and hepatic parameters related to inflammation, oxidative stress, lipid metabolism, liver function, and hepatocyte senescence. Our results suggest that the upregulation of FMO3 mimics CR to prevent or reverse hepatic aging by promoting autophagy.

KLF-1 orchestrates a xenobiotic detoxification program essential for longevity of mitochondrial mutants

Most manipulations that extend lifespan also increase resistance to various stress factors and environmental cues in a range of animals from yeast to mammals. However, the underlying molecular mechanisms regulating stress resistance during aging are still largely unknown. Here we identify Krüppel-like factor 1 (KLF-1) as a mediator of a cytoprotective response that dictates longevity induced by reduced mitochondrial function. A redox-regulated KLF-1 activation and transfer to the nucleus coincides with the peak of somatic mitochondrial biogenesis that occurs around a transition from larval stage L3 to D1. We further show that KLF-1 activates genes involved in the xenobiotic detoxification programme and identified cytochrome P450 oxidases, the KLF-1 main effectors, as longevity-assurance factors of mitochondrial mutants. Collectively, these findings underline the importance of the xenobiotic detoxification in the mitohormetic, longevity assurance pathway and identify KLF-1 as a central factor in orchestrating this response.

DDS promotes longevity through a microbiome-mediated starvation signal

The antibiotic diaminodiphenyl sulfone (DDS) is used in combination with other antibiotics as a first line treatment for leprosy. DDS has been previously reported to extend lifespan in Caenorhabditis elegans through inhibition of pyruvate kinase and decreased mitochondrial function. Here we report an alternative mechanism of action by which DDS promotes longevity in C. elegans by reducing folate production by the microbiome. This results in altered methionine cycle metabolite levels mimicking the effects of metformin and lifespan extension that is dependent on the starvation- and hypoxia-induced flavin containing monoxygenase, FMO-2.

Analysis of the coding sequences of clownfish reveals molecular convergence in the evolution of lifespan

Background

Standard evolutionary theories of aging postulate that reduced extrinsic mortality leads to evolution of longevity. Clownfishes of the genus Amphiprion live in a symbiotic relationship with sea anemones that provide protection from predators. We performed a survey and identified at least two species with a lifespan of over 20 years. Given their small size and ease of captive reproduction, clownfish lend themselves as experimental models of exceptional longevity. To identify genetic correlates of exceptional longevity, we sequenced the transcriptomes of Amphiprion percula and A. clarkii and performed a scan for positively-selected genes (PSGs).

Results

The PSGs that we identified in the last common clownfish ancestor were compared with PSGs detected in long-lived mole rats and short-lived killifishes revealing convergent evolution in processes such as mitochondrial biogenesis. Among individual genes, the Mitochondrial Transcription Termination Factor 1 (MTERF1), was positively-selected in all three clades, whereas the Glutathione S-Transferase Kappa 1 (GSTK1) was under positive selection in two independent clades. For the latter, homology modelling strongly suggested that positive selection targeted enzymatically important residues.

Conclusions

These results indicate that specific pathways were recruited in independent lineages evolving an exceptionally extended or shortened lifespan and point to mito-nuclear balance as a key factor.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1409-0) contains supplementary material, which is available to authorized users.

A novel gene-diet pair modulates C. elegans aging

Diet profoundly affects metabolism and incidences of age-related diseases. Animals adapt their physiology to different food-types, modulating complex life-history traits like aging. The molecular mechanisms linking adaptive capacity to diet with aging are less known. We identify FLR-4 kinase as a novel modulator of aging in C. elegans, depending on bacterial diet. FLR-4 functions to prevent differential activation of the p38MAPK pathway in response to diverse food-types, thereby maintaining normal life span. In a kinase-dead flr-4 mutant, E. coli HT115 (K12 strain), but not the standard diet OP50 (B strain), is able to activate p38MAPK, elevate expression of cytoprotective genes through the nuclear hormone receptor NHR-8 and enhance life span. Interestingly, flr-4 and dietary restriction utilize similar pathways for longevity assurance, suggesting cross-talks between cellular modules that respond to diet quality and quantity. Together, our study discovers a new C. elegans gene-diet pair that controls the plasticity of aging.

For animals living in the wild, being able to utilize a wide range of diet is evolutionarily advantageous as they can survive even when their optimal diet is depleted. Since diet is known to influence the rate of aging, animals seem to have evolved intricate mechanisms to maintain homeostasis and normal life span, but the molecular mechanisms are less understood. Using a small nematode, C. elegans as a model, we show that the adaptive capacity to different diet is maintained by a kinase gene. When this gene is mutated, worms start living longer on one strain of bacterial diet but not on the other. We identify the molecular cascade required for this food-type-dependent longevity. We show that this cascade of events significantly overlaps with the pathway that determine food quantity-dependent life span enhancement. Our study thus elucidates a part of the molecular monitoring system that regulates longevity dependent on the available quality and quantity of diet.

Maternal nutrient restriction in baboon programs later-life cellular growth and respiration of cultured skin fibroblasts: a potential model for the study of aging-programming interactions

Compelling data exist for programming of chronic later-life diseases and longevity by perinatal developmental programming challenges. Understanding mechanisms by which life course health trajectory and longevity are set is fundamental to understanding aging. Appropriate approaches are needed to determine programming effects on cellular function. We have developed a baboon model in which control mothers eat ad libitum while a second group eat 70% of the global diet fed controls, leading to male and female offspring intrauterine growth restriction (IUGR). We have shown that IUGR suffer from acceleration of several age-related physiological declines. Here, we report on a skin-derived fibroblast model with potential relevance for mechanistic studies on how IUGR impacts aging. Fibroblasts were cultured from the skin biopsies taken from adult baboons from control and IUGR cohorts. IUGR-derived fibroblasts grew in culture less well than controls and those derived from male, but not female, IUGR baboons had a significant reduction in maximum respiration rate compared to control-derived fibroblasts. We also show that relative levels of several mitochondrial protein subunits, including NDUFB8 and cytochrome c oxidase subunit IV, were reduced in IUGR-derived fibroblasts even after serial passaging in culture. The lower levels of electron transport system components provide potential mechanisms for accelerated life course aging in the setting of programmed IUGR. This observation fits with the greater sensitivity of males compared with females to many, but not all, outcomes in response to programming challenges. These approaches will be powerful in the determination of programming-aging interactions.

The effects of graded levels of calorie restriction: XI. Evaluation of the main hypotheses underpinning the life extension effects of CR using the hepatic transcriptome

Calorie restriction (CR) may extend longevity by modulating the mechanisms involved in aging. Different hypotheses have been proposed for its main mode of action. We quantified hepatic transcripts of male C57BL/6 mice exposed to graded levels of CR (0% to 40% CR) for three months, and evaluated the responses relative to these various hypotheses. Of the four main signaling pathways implied to be linked to the impact of CR on lifespan (insulin/insulin like growth factor 1 (IGF-1), nuclear factor-kappa beta (NF-ĸB), mechanistic target of rapamycin (mTOR) and sirtuins (SIRTs)), all the pathways except SIRT were altered in a manner consistent with increased lifespan. However, the expression levels of SIRT4 and SIRT7 were decreased with increasing levels of CR. Changes consistent with altered fuel utilization under CR may reduce reactive oxygen species production, which was paralleled by reduced protection. Downregulated major urinary protein (MUP) transcription suggested reduced reproductive investment. Graded CR had a positive effect on autophagy and xenobiotic metabolism, and was protective with respect to cancer signaling. CR had no significant effect on fibroblast growth factor-21 (FGF21) transcription but affected transcription in the hydrogen sulfide production pathway. Responses to CR were consistent with several different hypotheses, and the benefits of CR on lifespan likely reflect the combined impact on multiple aging related processes.

Longevity is impacted by growth hormone action during early postnatal period

Life-long lack of growth hormone (GH) action can produce remarkable extension of longevity in mice. Here we report that GH treatment limited to a few weeks during development influences the lifespan of long-lived Ames dwarf and normal littermate control mice in a genotype and sex-specific manner. Studies in a separate cohort of Ames dwarf mice show that this short period of the GH exposure during early development produces persistent phenotypic, metabolic and molecular changes that are evident in late adult life. These effects may represent mechanisms responsible for reduced longevity of dwarf mice exposed to GH treatment early in life. Our data suggest that developmental programming of aging importantly contributes to (and perhaps explains) the well documented developmental origins of adult disease.

Flavin-containing monooxygenases in aging and disease: Emerging roles for ancient enzymes

Flavin-containing monooxygenases (FMOs) are primarily studied as xenobiotic metabolizing enzymes with a prominent role in drug metabolism. In contrast, endogenous functions and substrates of FMOs are less well understood. A growing body of recent evidence, however, implicates FMOs in aging, several diseases, and metabolic pathways. The evidence suggests an important role for these well-conserved proteins in multiple processes and raises questions about the endogenous substrate(s) and regulation of FMOs. Here, we present an overview of evidence for FMOs' involvement in aging and disease, discussing the biological context and arguing for increased investigation into the function of these enzymes.

Molecular pathology endpoints useful for aging studies

The first clinical trial aimed at targeting fundamental processes of aging will soon be launched (TAME: Targeting Aging with Metformin). In its wake is a robust pipeline of therapeutic interventions that have been demonstrated to extend lifespan or healthspan of preclinical models, including rapalogs, antioxidants, anti-inflammatory agents, and senolytics. This ensures that if the TAME trial is successful, numerous additional clinical trials are apt to follow. But a significant impediment to these trials remains the question of what endpoints should be measured? The design of the TAME trial very cleverly skirts around this based on the fact that there are decades of data on metformin in humans, providing unequaled clarity of what endpoints are most likely to yield a positive outcome. But for a new chemical entity, knowing what endpoints to measure remains a formidable challenge. For economy's sake, and to achieve results in a reasonable time frame, surrogate markers of lifespan and healthy aging are desperately needed. This review provides a comprehensive analysis of molecular endpoints that are currently being used as indices of age-related phenomena (e.g., morbidity, frailty, mortality) and proposes an approach for validating and prioritizing these endpoints.

Selected life-extending interventions reduce arterial CXCL10 and macrophage colony-stimulating factor in aged mouse arteries

Cardiovascular disease (CVD) is the leading cause of death in the industrialized world. Aging is the most predictive risk factor for CVD and is associated with arterial inflammation which contributes to increased CVD risk. Although age-related arterial inflammation has been described in both humans and animals, only a limited number of inflammatory mediators, cytokines and chemokines have been identified. In this investigation we sought to determine whether lifespan extending interventions, including crowded litter early life nutrient deprivation (CL), traditional lifelong caloric restriction (CR) and lifelong Rapamycin treatment (Rap) would attenuate age-related arterial inflammation using multi analyte profiling. Aortas from Young (4-6months), Old (22months), Old CL, Old CR and Old Rap mice were homogenized and cytokine concentrations were assessed using Luminex Multi Analyte Profiling. Chemokines involved in immune cell recruitment, such as CCL2, CXCL9, CXCL10, GMCSF and MCSF, were increased in Old vs. Young (p<0.05). The age-related increase of CXCL10 was prevented by CR (p<0.05 vs. Old). MSCF concentrations were lower in aortas of Rap treated mice (p<0.05 vs. Old). Interleukins (IL), IL-1α, IL-1β and IL-10, were also greater in Old vs. Young mice (p<0.05). These data demonstrate selected lifespan extending interventions can prevent or limit age-related increases in selected aortic chemokines.

Influence of Nrf2 activators on subcellular skeletal muscle protein and DNA synthesis rates after 6 weeks of milk protein feeding in older adults

In older adults, chronic oxidative and inflammatory stresses are associated with an impaired increase in skeletal muscle protein synthesis after acute anabolic stimuli. Conjugated linoleic acid (CLA) and Protandim have been shown to activate nuclear factor erythroid-derived 2-like 2 (Nrf2), a transcription factor for the antioxidant response element and anti-inflammatory pathways. This study tested the hypothesis that compared to a placebo control (CON), CLA and Protandim would increase skeletal muscle subcellular protein (myofibrillar, mitochondrial, cytoplasmic) and DNA synthesis in older adults after 6 weeks of milk protein feeding. CLA decreased oxidative stress and skeletal muscle oxidative damage with a trend to increase messenger RNA (mRNA) expression of a Nrf2 target, NAD(P)H dehydrogenase quinone 1 (NQO1). However, CLA did not influence other Nrf2 targets (heme oxygenase-1 (HO-1), glutathione peroxidase 1 (Gpx1)) or protein or DNA synthesis. Conversely, Protandim increased HO-1 protein content but not the mRNA expression of downstream Nrf2 targets, oxidative stress, or skeletal muscle oxidative damage. Rates of myofibrillar protein synthesis were maintained despite lower mitochondrial and cytoplasmic protein syntheses after Protandim versus CON. Similarly, DNA synthesis was non-significantly lower after Protandim compared to CON. After Protandim, the ratio of protein to DNA synthesis tended to be greater in the myofibrillar fraction and maintained in the mitochondrial and cytoplasmic fractions, emphasizing the importance of measuring both protein and DNA synthesis to gain insight into proteostasis. Overall, these data suggest that Protandim may enhance proteostatic mechanisms of skeletal muscle contractile proteins after 6 weeks of milk protein feeding in older adults.

Transaldolase inhibition impairs mitochondrial respiration and induces a starvation-like longevity response in Caenorhabditis elegans

Mitochondrial dysfunction can increase oxidative stress and extend lifespan in Caenorhabditis elegans. Homeostatic mechanisms exist to cope with disruptions to mitochondrial function that promote cellular health and organismal longevity. Previously, we determined that decreased expression of the cytosolic pentose phosphate pathway (PPP) enzyme transaldolase activates the mitochondrial unfolded protein response (UPRmt) and extends lifespan. Here we report that transaldolase (tald-1) deficiency impairs mitochondrial function in vivo, as evidenced by altered mitochondrial morphology, decreased respiration, and increased cellular H2O2 levels. Lifespan extension from knockdown of tald-1 is associated with an oxidative stress response involving p38 and c-Jun N-terminal kinase (JNK) MAPKs and a starvation-like response regulated by the transcription factor EB (TFEB) homolog HLH-30. The latter response promotes autophagy and increases expression of the flavin-containing monooxygenase 2 (fmo-2). We conclude that cytosolic redox established through the PPP is a key regulator of mitochondrial function and defines a new mechanism for mitochondrial regulation of longevity.

Rapamycin and the inhibition of the secretory phenotype

Senescent cells contribute to age-related pathology and loss of function, and their selective removal improves physiological function and extends longevity. Cell senescence is a complex process that can be triggered by multiple challenges. Recently it has been observed that the composition of the secretory phenotype or SASP depends on the insult that triggers cell senescence. Rapamycin, an inhibitor of mTOR that increases longevity in several species, inhibits cell senescence in vitro, while silencing the Nrf2 gene induces premature senescence. We have found that rapamycin activates the Nrf2 pathway to regulate cell cycle arrest, but not the production of SASP, which is regulated by a different pathway, probably involving the inhibition of MAPKAPK2.

Rapamycin: An InhibiTOR of Aging Emerges From the Soil of Easter Island

Rapamycin (sirolimus) is a macrolide immunosuppressant that inhibits the mechanistic target of rapamycin (mTOR) protein kinase and extends lifespan in model organisms including mice. Although rapamycin is an FDA-approved drug for select indications, a diverse set of negative side effects may preclude its wide-scale deployment as an antiaging therapy. mTOR forms two different protein complexes, mTORC1 and mTORC2; the former is acutely sensitive to rapamycin whereas the latter is only chronically sensitive to rapamycin in vivo. Over the past decade, it has become clear that although genetic and pharmacological inhibition of mTORC1 extends lifespan and delays aging, inhibition of mTORC2 has negative effects on mammalian health and longevity and is responsible for many of the negative side effects of rapamycin. In this review, we discuss recent advances in understanding the molecular and physiological effects of rapamycin treatment, and we discuss how the use of alternative rapamycin treatment regimens or rapamycin analogs has the potential to mitigate the deleterious side effects of rapamycin treatment by more specifically targeting mTORC1. Although the side effects of rapamycin are still of significant concern, rapid progress is being made in realizing the revolutionary potential of rapamycin-based therapies for the treatment of diseases of aging.

Nutritional limitation in early postnatal life and its effect on aging and longevity in rodents

Nutrient limitation in the form of chronic dietary restriction (DR), or more specifically a life-long reduction of total daily nutritional intake, was first shown to extend longevity in rats more than eight decades ago and is one of the most robust anti-aging interventions known. More recently, it has become apparent that dietary restriction limited to only the first few weeks of life in rodents is also capable of significantly impacting aging and longevity. The imposition of nutrient limitation is often achieved via the manipulation of litter size or the modulation of maternal nutrient intake during the lactational period. Not surprisingly, nutrient limited pups are smaller at weaning, and remain so throughout their life, while exhibiting signs of slowed aging. In this review, we discuss potential mechanisms that account for the anti-aging effects of postnatal undernutrition with an emphasis on those pathways that parallel changes seen with chronic DR.

Lithium Promotes Longevity through GSK3/NRF2-Dependent Hormesis

The quest to extend healthspan via pharmacological means is becoming increasingly urgent, both from a health and economic perspective. Here we show that lithium, a drug approved for human use, promotes longevity and healthspan. We demonstrate that lithium extends lifespan in female and male Drosophila, when administered throughout adulthood or only later in life. The life-extending mechanism involves the inhibition of glycogen synthase kinase-3 (GSK-3) and activation of the transcription factor nuclear factor erythroid 2-related factor (NRF-2). Combining genetic loss of the NRF-2 repressor Kelch-like ECH-associated protein 1 (Keap1) with lithium treatment revealed that high levels of NRF-2 activation conferred stress resistance, while low levels additionally promoted longevity. The discovery of GSK-3 as a therapeutic target for aging will likely lead to more effective treatments that can modulate mammalian aging and further improve health in later life.

A longitudinal analysis of the effects of age on the blood plasma metabolome in the common marmoset, Callithrix jacchus

Primates tend to be long-lived for their size with humans being the longest lived of all primates. There are compelling reasons to understand the underlying age-related processes that shape human lifespan. But the very fact of our long lifespan that makes it so compelling, also makes it especially difficult to study. Thus, in studies of aging, researchers have turned to non-human primate models, including chimpanzees, baboons, and rhesus macaques. More recently, the common marmoset, Callithrix jacchus, has been recognized as a particularly valuable model in studies of aging, given its small size, ease of housing in captivity, and relatively short lifespan. However, little is known about the physiological changes that occur as marmosets age. To begin to fill in this gap, we utilized high sensitivity metabolomics to define the longitudinal biochemical changes associated with age in the common marmoset. We measured 2104 metabolites from blood plasma at three separate time points over a 17-month period, and we completed both a cross-sectional and longitudinal analysis of the metabolome. We discovered hundreds of metabolites associated with age and body weight in both male and female animals. Our longitudinal analysis identified age-associated metabolic pathways that were not found in our cross-sectional analysis. Pathways enriched for age-associated metabolites included tryptophan, nucleotide, and xenobiotic metabolism, suggesting these biochemical pathways might play an important role in the basic mechanisms of aging in primates. Moreover, we found that many metabolic pathways associated with age were sex specific. Our work illustrates the power of longitudinal approaches, even in a short time frame, to discover novel biochemical changes that occur with age.