Health and longevity studies in C. elegans: the "healthy worm database" reveals strengths, weaknesses and gaps of test compound-based studies

The role of Caenorhabditis elegans in the discovery of natural products for healthy aging

Covering: 2012 to 2023The human population is aging. Thus, the greatest risk factor for numerous diseases, such as diabetes, cancer and neurodegenerative disorders, is increasing worldwide. Age-related diseases do not typically occur in isolation, but as a result of multi-factorial causes, which in turn require holistic approaches to identify and decipher the mode of action of potential remedies. With the advent of C. elegans as the primary model organism for aging, researchers now have a powerful in vivo tool for identifying and studying agents that effect lifespan and health span. Natural products have been focal research subjects in this respect. This review article covers key developments of the last decade (2012-2023) that have led to the discovery of natural products with healthy aging properties in C. elegans. We (i) discuss the state of knowledge on the effects of natural products on worm aging including methods, assays and involved pathways; (ii) analyze the literature on natural compounds in terms of their molecular properties and the translatability of effects on mammals; (iii) examine the literature on multi-component mixtures with special attention to the studied organisms, extraction methods and efforts regarding the characterization of their chemical composition and their bioactive components. (iv) We further propose to combine small in vivo model organisms such as C. elegans and sophisticated analytical approaches ("wormomics") to guide the way to dissect complex natural products with anti-aging properties.

Structured Docosahexaenoic Acid (DHA) Enhances Motility and Promotes the Antioxidant Capacity of Aged C. elegans

The human lifespan has increased over the past century; however, healthspans have not kept up with this trend, especially cognitive health. Among nutrients for brain function maintenance, long-chain omega-3 polyunsaturated fatty acids (ω-3 LCPUFA): DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) must be highlighted, particularly structured forms of EPA and DHA which were developed to improve bioavailability and bioactivity in comparison with conventional ω-3 supplements. This study aims to elucidate the effect of a structured triglyceride form of DHA (DHA-TG) on the healthspan of aged C. elegans. Using a thrashing assay, the nematodes were monitored at 4, 8, and 12 days of adulthood, and DHA-TG improved its motility at every age without affecting lifespan. In addition, the treatment promoted antioxidant capacity by enhancing the activity and expression of SOD (superoxide dismutase) in the nematodes. Lastly, as the effect of DHA-TG was lost in the DAF-16 mutant strain, it might be hypothesized that the effects of DHA need DAF-16/FOXO as an intermediary. In brief, DHA-TG exerted a healthspan-promoting effect resulting in both enhanced physical fitness and increased antioxidant defense in aged C. elegans. For the first time, an improvement in locomotive function in aged wild-type nematodes is described following DHA-TG treatment.

In vivo quantitative high-throughput screening for drug discovery and comparative toxicology

Quantitative high-throughput screening (qHTS) pharmacologically evaluates chemical libraries for therapeutic uses, toxicological risk and, increasingly, for academic probe discovery. Phenotypic high-throughput screening assays interrogate molecular pathways, often relying on cell culture systems, historically less focused on multicellular organisms. Caenorhabditis elegans has served as a eukaryotic model organism for human biology by virtue of genetic conservation and experimental tractability. Here, a paradigm enabling C. elegans qHTS using 384-well microtiter plate laser-scanning cytometry is described, in which GFP-expressing organisms revealing phenotype-modifying structure-activity relationships guide subsequent life-stage and proteomic analyses, and Escherichia coli bacterial ghosts, a non-replicating nutrient source, allow compound exposures over two life cycles, mitigating bacterial overgrowth complications. We demonstrate the method with libraries of anti-infective agents, or substances of toxicological concern. Each was tested in seven-point titration to assess the feasibility of nematode-based in vivo qHTS, and examples of follow-up strategies were provided to study organism-based chemotype selectivity and subsequent network perturbations with a physiological impact. We anticipate that this qHTS approach will enable analysis of C. elegans orthologous phenotypes of human pathologies to facilitate drug library profiling for a range of therapeutic indications.

Identification of a Hydroxygallic Acid Derivative, Zingibroside R1 and a Sterol Lipid as Potential Active Ingredients of Cuscuta chinensis Extract That Has Neuroprotective and Antioxidant Effects in Aged Caenorhabditis elegans

We examined the effects of the extracts from two traditional Chinese medicine plants, Cuscuta chinensis and Eucommia ulmoides, on the healthspan of the model organism Caenorhabditis elegans. C. chinensis increased the short-term memory and the mechanosensory response of aged C. elegans. Furthermore, both extracts improved the resistance towards oxidative stress, and decreased the intracellular level of reactive oxygen species. Chemical analyses of the extracts revealed the presence of several bioactive compounds such as chlorogenic acid, cinnamic acid, and quercetin. A fraction from the C. chinensis extract enriched in zingibroside R1 improved the lifespan, the survival after heat stress, and the locomotion in a manner similar to the full C. chinensis extract. Thus, zingibroside R1 could be (partly) responsible for the observed health benefits of C. chinensis. Furthermore, a hydroxygallic acid derivative and the sterol lipid 4-alpha-formyl-stigmasta-7,24(241)-dien-3-beta-ol are abundantly present in the C. chinensis extract and its most bioactive fraction, but hardly in E. ulmoides, making them good candidates to explain the overall healthspan benefits of C. chinensis compared to the specific positive effects on stress resistance by E. ulmoides. Our findings highlight the overall anti-aging effects of C. chinensis in C. elegans and provide first hints about the components responsible for these effects.

Identification of healthspan-promoting genes in Caenorhabditis elegans based on a human GWAS study

To find drivers of healthy ageing, a genome-wide association study (GWAS) was performed in healthy and unhealthy older individuals. Healthy individuals were defined as free from cardiovascular disease, stroke, heart failure, major adverse cardiovascular event, diabetes, dementia, cancer, chronic obstructive pulmonary disease (COPD), asthma, rheumatism, Crohn’s disease, malabsorption or kidney disease. Six single nucleotide polymorphisms (SNPs) with unknown function associated with ten human genes were identified as candidate healthspan markers. Thirteen homologous or closely related genes were selected in the model organism C. elegans for evaluating healthspan after targeted RNAi-mediated knockdown using pathogen resistance, muscle integrity, chemotaxis index and the activity of known longevity and stress response pathways as healthspan reporters. In addition, lifespan was monitored in the RNAi-treated nematodes. RNAi knockdown of yap-1, wwp-1, paxt-1 and several acdh genes resulted in heterogeneous phenotypes regarding muscle integrity, pathogen resistance, chemotactic behaviour, and lifespan. Based on these observations, we hypothesize that their human homologues WWC2, CDKN2AIP and ACADS may play a role in health maintenance in the elderly.

Stress Buffering and Longevity Effects of Amber Extract on Caenorhabditis elegans (C. elegans)

Amber is a fossilized tree resin historically used in wound healing and stress relief. Unfortunately, there is no concrete scientific evidence supporting such efficacy. Here, the stress buffering and longevity effect of Amber extract (AE) in Caenorhabditis elegans (C. elegans) was investigated. Survival assays, health span assays, Enzyme-Linked Immunosorbent Assay (ELISA), Stress biomarker detection assays, Green Fluorescence Proteins (GFP), Real Time quantitative PCR (RT-qPCR) and C. elegans mutants were employed to investigate the stress buffering and longevity effect of AE. In the study, it was observed that AE supplementation improved health span and survival in both normal and stressed worms. Additionally, AE positively regulated stress hormones (cortisol, oxytocin, and dopamine) and decreased fat and reactive oxygen species (ROS) accumulation. Through the Insulin/IGF-1 signaling (IIS) pathway, AE enhanced the nuclear localization of DAF-16 and the expression of heat shock proteins and antioxidant genes in GFP-tagged worms and at messenger RNA levels. Finally, AE failed to increase the survival of daf-16, daf-2, skn-1 and hsf-1 loss-of-function mutants, confirming the involvement of the IIS pathway. Evidently, AE supplementation relieves stress and enhances longevity. Thus, amber may be a potent nutraceutical for stress relief.

A Potential Probiotic Lactobacillus plantarum JBC5 Improves Longevity and Healthy Aging by Modulating Antioxidative, Innate Immunity and Serotonin-Signaling Pathways in Caenorhabditis elegans

Since the hypothesis of Dr. Elie Metchnikoff on lactobacilli-mediated healthy aging, several microbes have been reported to extend the lifespan with different features of healthy aging. However, a microbe affecting diverse features of healthy aging is of choice for broader acceptance and marketability as a next-generation probiotic. We employed Caenorhabditis elegans as a model to understand the potential of Lactobacillus plantarum JBC5 (LPJBC5), isolated from fermented food sample on longevity and healthy aging as well as their underlying mechanisms. Firstly, LPJBC5 enhanced the mean lifespan of C. elegans by 27.81% compared with control (untreated). LPBC5-induced longevity was accompanied with better aging-associated biomarkers, such as physical functions, fat, and lipofuscin accumulation. Lifespan assay on mutant worms and gene expression studies indicated that LPJBC5-mediated longevity was due to upregulation of the skinhead-1 (skn-1) gene activated through p38 MAPK signaling cascade. Secondly, the activated transcription factor SKN-1 upregulated the expression of antioxidative, thermo-tolerant, and anti-pathogenic genes. In support, LPJBC5 conferred resistance against abiotic and biotic stresses such as oxidative, heat, and pathogen. LPJBC5 upregulated the expression of intestinal tight junction protein ZOO-1 and improved gut integrity. Thirdly, LPJBC5 improved the learning and memory of worms trained on LPJBC5 compared with naive worms. The results showed upregulation of genes involved in serotonin signaling (ser-1, mod-1, and tph-1) in LPJBC5-fed worms compared with control, suggesting that serotonin-signaling was essential for LPJBC5-mediated improved cognitive function. Fourthly, LPJBC5 decreased the fat accumulation in worms by reducing the expression of genes encoding key substrates and enzymes of fat metabolism (i.e., fat-5 and fat-7). Lastly, LPJBC5 reduced the production of reactive oxygen species and improved mitochondrial function, thereby reducing apoptosis in worms. The capability of a single bacterium on pro-longevity and the features of healthy aging, including enhancement of gut integrity and cognitive functions, makes it an ideal candidate for promotion as a next-generation probiotic.

An extract of Rosaceae, Solanaceae and Zingiberaceae increases health span and mobility in Caenorhabditis elegans

Background

Members of the Rosaceae, Solanaceae and Zingiberaceae families which include fruits such as cherries, tomatoes and ginger are known to have health promoting effects. There is growing interest in consuming these “functional foods” as a means to increase health and healthy ageing. However, many studies explore the effect of these foods in isolation, not as a blend of multiple functional foods.

Methods

In this study, an extract containing the dried berries, fruits, and roots of members of these families was prepared, which we called Bioact®180. The nematode Caenorhabditis elegans was used to evaluate the effects of Bioact®180 on lifespan and health endpoints, including muscle and mitochondria structure and locomotion.

Results

Exposure to the 1000 µg/mL of Bioact®180 extract, containing 4% total phenols, were healthier, as observed by an increase in mean lifespan with and small but significant increase in maximal lifespan. Nematodes exposed to Bioact®180 displayed better mobility in mid-life stages as well as enhanced mitochondrial morphology, which was more comparable to younger animals, suggesting that these worms are protected to some degree from sarcopenia.

Conclusions

Together, our findings reveal that Bioact®180, a blend of fruits and roots from Rosaceae, Solanaceae and Zingiberaceae family members has anti-aging effects. Bioact®180 promotes health and lifespan extension in C. elegans, corresponding to functional improvements in mobility.

Knock-down of odr-3 and ife-2 additively extends lifespan and healthspan in C. elegans

Genetic manipulations can ameliorate the aging process and extend the lifespan of model organisms. The aim of this research was to identify novel genetic interventions that promote both lifespan and healthspan, by combining the effects of multiple longevity-associated gene inactivations in C. elegans. For this, the individual and combined effects of the odr-3 mutation and of ife-2 and cku-70 knock-downs were studied, both in the wild type and daf-16 mutant backgrounds. We found that besides increasing the lifespan of wild type animals, the knock-down of ife-2 (starting at L4) also extends the lifespan and healthspan of long-lived odr-3 mutants. In the daf-16 background, ife-2 and odr-3 impairment exert opposing effects individually, while the daf-16; odr-3; ife-2 deficient animals show a similar lifespan and healthspan as daf-16, suggesting that the odr-3 and ife-2 effector outcomes converge downstream of DAF-16. By contrast, cku-70 knock-down did not extend the lifespan of single or double odr-3; ife-2 inactivated animals, and was slightly deleterious to healthspan. In conclusion, we report that impairment of odr-3 and ife-2 increases lifespan and healthspan in an additive and synergistic manner, respectively, and that this result is not improved by further knocking-down cku-70.

Genes implicated in Caenorhabditis elegans and human health regulate stress resistance and physical abilities in aged Caenorhabditis elegans

Recently, nine Caenorhabditis elegans genes, grouped into two pathways/clusters, were found to be implicated in healthspan in C. elegans and their homologues in humans, based on literature curation, WormBase data mining and bioinformatics analyses. Here, we further validated these genes experimentally in C. elegans. We downregulated the nine genes via RNA interference (RNAi), and their effects on physical function (locomotion in a swim assay) and on physiological function (survival after heat stress) were analysed in aged nematodes. Swim performance was negatively affected by the downregulation of acox-1.1, pept-1, pak-2, gsk-3 and C25G6.3 in worms with advanced age (twelfth day of adulthood) and heat stress resistance was decreased by RNAi targeting of acox-1.1, daf-22, cat-4, pig-1, pak-2, gsk-3 and C25G6.3 in moderately (seventh day of adulthood) or advanced aged nematodes. Only one gene, sad-1, could not be linked to a health-related function in C. elegans with the bioassays we selected. Thus, most of the healthspan genes could be re-confirmed by health measurements in old worms.

Red Cabbage Rather Than Green Cabbage Increases Stress Resistance and Extends the Lifespan of Caenorhabditis elegans

Many studies have demonstrated that cabbages possess various biological activities, and our previous studies confirmed that cyanidin-3-diglucoside-5-glucoside (CY3D5G), the major core of red cabbage anthocyanins, exhibited in vitro antioxidant activity. This study further investigated the protective effects of CY3D5G derivative from red cabbage juice (RCJ) on oxidative stress and lifespan in cells and Caenorhabditis elegans, green cabbage juice (GCJ) was used as control. RCJ rather than GCJ significantly improved cell viability and decreased lactate dehydrogenase release in H₂O₂-induced caco-2 cells. RCJ significantly increased survival during oxidative and heat stress and mean lifespan in C. elegans by 171.63% and 31.64%, and 28.16%, respectively, while GCJ treatment showed no significant effects (p < 0.05). These results might be attributed to significantly (p < 0.05) higher contents of total phenolics, ascorbic acid, glucosinolates, and anthocyanins in RCJ compared to those in GCJ. Additionally, both of them decreased autofluorescence and reproductive capacity, increased body length, but did not alter the intracellular ROS level. Prolonged lifespan by RCJ might require heat-shock transcription factor pathway, sirtuin signaling, and calmodulin kinase II pathway, independent of insulin/insulin-like growth factor-1 signaling pathway. RCJ showed promising antioxidant properties in caco-2 cells and C. elegans, which provided more information on the health benefits of cabbage.

Curcuma Longa, the "Golden Spice" to Counteract Neuroinflammaging and Cognitive Decline-What Have We Learned and What Needs to Be Done

Due to the global increase in lifespan, the proportion of people showing cognitive impairment is expected to grow exponentially. As target-specific drugs capable of tackling dementia are lagging behind, the focus of preclinical and clinical research has recently shifted towards natural products. Curcumin, one of the best investigated botanical constituents in the biomedical literature, has been receiving increased interest due to its unique molecular structure, which targets inflammatory and antioxidant pathways. These pathways have been shown to be critical for neurodegenerative disorders such as Alzheimer’s disease and more in general for cognitive decline. Despite the substantial preclinical literature on the potential biomedical effects of curcumin, its relatively low bioavailability, poor water solubility and rapid metabolism/excretion have hampered clinical trials, resulting in mixed and inconclusive findings. In this review, we highlight current knowledge on the potential effects of this natural compound on cognition. Furthermore, we focus on new strategies to overcome current limitations in its use and improve its efficacy, with attention also on gender-driven differences.