Daf-2 Mutants Research Articles

Tetrastigma hemsleyanum leaves extract against acrylamide-induced toxicity in HepG2 cells and Caenorhabditis elegans

Acrylamide (ACR), as a raw material of polyacrylamide that used in water purification, was verified to possess various toxicity. Tetrastigma hemsleyanum (TH) is a medicinal plant widely used to anti-inflammation and anti-tumor in Chinese folks. However, more researches focused on the biological activities in tubers and the leaves were ignored. Thus, the protective effect of Tetrastigma hemsleyanum leaves extract (THLE) against ACR-induced toxicity in HepG2 cells and Caenorhabditis elegans (C. elegans) was explored in this study. In vitro, we observed that THLE attenuated ACR-induced toxicity in HepG2 cell via regulating Akt/mTOR/FOXO1/MAPK signaling pathway. Further research proved that 5-caffeoylquinic acid (5-CA) plays a major role in THLE’s amelioration effect of ACR toxicity. In vivo, it was found that THLE possesses the same protective effect in ACR-treated wild-type N2 C. elegans and daf-2 (-) (deficit in DAF-2) mutants. However, the anti-ACR toxicity effect of THLE in daf-16 (-) mutants (deficit in DAF-16 that homologous to FOXO family in human) was weakened. Our results indicated that THLE exhibited protective effects against ACR-induced toxicity both in HepG2 cells and C. elegans, while DAF-16/FOXO gene is involved in THLE’ protective effect via regulating the expression levels of downstream antioxidant genes.

Heat shock pretreatment induced cadmium resistance in the nematode Caenorhabditis elegans is depend on transcription factors DAF-16 and HSF-1

Cadmium (Cd) exposure poses a serious environmental problem due to the metal’s bioaccumulation and difficult to eliminate from body. Understanding the mechanisms of Cd detoxification and resistance can provide insights into methods to protect against the damaging effects of the heavy metal. In the present study, we found that heat shock (HS) pretreatment increased Cd resistance of the nematode Caenorhabditis elegans by reducing the bagging phenotype and protecting the integrity of the intestinal barrier. HS pretreatment increased the expression of heat shock protein-16.2 (HSP-16.2) prior to Cd exposure, and HS-induced Cd resistance was absent in worms with hsp-16.2 loss-of-function mutation. Worm strain with daf-2(e1370) mutation presented enhanced HS-induced Cd resistance, which was eliminated in worm strains of daf-16(mu86) and hsf-1(sy441). HS pretreatment increased DAF-16 nuclear localization and HSF-1 granule formation prior to Cd exposure. DAF-16 and HSF-1 was essential in reducing bagging formation and protecting the integrity of intestinal barrier after HS pretreatment. In conclusion, the present study demonstrated that HS-induced Cd resistance in C. elegans is regulated by the DAF-16/FOXO and HSF-1 pathways through regulation of HSP-16.2 expression.

DAF-16/FoxO in Caenorhabditis elegans and Its Role in Metabolic Remodeling

DAF-16, the only forkhead box transcription factors class O (FoxO) homolog in Caenorhabditis elegans, integrates signals from upstream pathways to elicit transcriptional changes in many genes involved in aging, development, stress, metabolism, and immunity. The major regulator of DAF-16 activity is the insulin/insulin-like growth factor 1 (IGF-1) signaling (IIS) pathway, reduction of which leads to lifespan extension in worms, flies, mice, and humans. In C. elegans daf-2 mutants, reduced IIS leads to a heterochronic activation of a dauer survival program during adulthood. This program includes elevated antioxidant defense and a metabolic shift toward accumulation of carbohydrates (i.e., trehalose and glycogen) and triglycerides, and activation of the glyoxylate shunt, which could allow fat-to-carbohydrate conversion. The longevity of daf-2 mutants seems to be partially supported by endogenous trehalose, a nonreducing disaccharide that mammals cannot synthesize, which points toward considerable differences in downstream mechanisms by which IIS regulates aging in distinct groups.

From pathogen to a commensal: modification of the Microbacterium nematophilum-Caenorhabditis elegans interaction during chronic infection by the absence of host insulin signalling.

ABSTRACTThe nematode worm Caenorhabditis elegans depends on microbes in decaying vegetation as its food source. To survive in an environment rich in opportunistic pathogens, C. elegans has evolved an epithelial defence system where surface-exposed tissues such as epidermis, pharynx, intestine, vulva and hindgut have the capacity of eliciting appropriate immune defences to acute gut infection. However, it is unclear how the worm responds to chronic intestinal infections. To this end, we have surveyed C. elegans mutants that are involved in inflammation, immunity and longevity to find their phenotypes during chronic infection. Worms that grew in a monoculture of the natural pathogen Microbacterium nematophilum (CBX102 strain) had a reduced lifespan and vigour. This was independent of intestinal colonisation as both CBX102 and the derived avirulent strain UV336 were early persistent colonisers. In contrast, the long-lived daf-2 mutant was resistant to chronic infection, showing reduced colonisation and higher vigour. In fact, UV336 interaction with daf-2 resulted in a host lifespan extension beyond OP50, the Escherichia coli strain used for laboratory C. elegans culture. Longevity and vigour of daf-2 mutants growing on CBX102 was dependent on the FOXO orthologue DAF-16. Our results indicate that the interaction between host genotype and strain-specific bacteria determines longevity and health for C. elegans.

Effect of plant sterol and galactooligosaccharides enriched beverages on oxidative stress and longevity in Caenorhabditis elegans

Abstract This study evaluates the impact of two plant sterol (PS) enriched fruit beverages (0.6 g /100 ml), without (MfB) or with GOS (MfB-G) (1.2 g/100 ml) on the resistance against oxidative stress induced by non-conventional (cholesterol oxidation products (COPs)) and conventional (H2O2) oxidant compounds, as well as their impact on C. elegans longevity. Nematodes fed with both beverages (0.005–0.25%, v/v) showed similar improved oxidative stress resistance against COPs and H2O2. This effect was dependent on daf-16 transcription factor, although GOS showed an additional beneficial effect independent to daf-16. In addition, both beverages extended nematode lifespan, independently of the presence of GOS. Longevity assays using daf-16 and daf-2 mutant strains revealed that the observed effect was potentially linked to the insulin-IGF-1 pathway. These results provide new in vivo evidence for the potential use of PS enriched fruit beverages in the prevention of oxidative stress underlying many diseases.

Antiaging, Stress Resistance, and Neuroprotective Efficacies of Cleistocalyx nervosum var. paniala Fruit Extracts Using Caenorhabditis elegans Model.

Plant parts and their bioactive compounds are widely used by mankind for their health benefits. Cleistocalyx nervosum var. paniala is one berry fruit, native to Thailand, known to exhibit various health benefits in vitro. The present study was focused on analyzing the antiaging, stress resistance, and neuroprotective effects of C. nervosum in model system Caenorhabditis elegans using physiological assays, fluorescent imaging, and qPCR analysis. The results suggest that the fruit extract was able to significantly extend the median and maximum lifespan of the nematode. It could also extend the healthspan by reducing the accumulation of the “age pigment” lipofuscin, inside the nematode along with regulating the expression of col-19, egl-8, egl-30, dgk-1, and goa-1 genes. Further, the extracts upregulated the expression of daf-16 while downregulating the expression of daf-2 and age-1 in wild-type nematodes. Interestingly, it could extend the lifespan in DAF-16 mutants suggesting that the extension of lifespan and healthspan was dependent and independent of DAF-16-mediated pathway. The fruit extract was also observed to reduce the level of Reactive Oxygen Species (ROS) inside the nematode during oxidative stress. The qPCR analysis suggests the involvement of skn-1 and sir-2.1 in initiating stress resistance by activating the antioxidant mechanism. Additionally, the fruit could also elicit neuroprotection as it could extend the median and maximum lifespan of transgenic strain integrated with Aβ. SKN-1 could play a pivotal role in establishing the antiaging, stress resistance, and neuroprotective effect of C. nervosum. Overall, C. nervosum can be used as a nutraceutical in the food industry which could offer potential health benefits.

Profiling microRNAs through development of the parasitic nematode Haemonchus identifies nematode-specific miRNAs that suppress larval development

Parasitic nematodes transition between dramatically different free-living and parasitic stages, with correctly timed development and migration crucial to successful completion of their lifecycle. However little is known of the mechanisms controlling these transitions. microRNAs (miRNAs) negatively regulate gene expression post-transcriptionally and regulate development of diverse organisms. Here we used microarrays to determine the expression profile of miRNAs through development and in gut tissue of the pathogenic nematode Haemonchus contortus. Two miRNAs, mir-228 and mir-235, were enriched in infective L3 larvae, an arrested stage analogous to Caenorhabditis elegans dauer larvae. We hypothesized that these miRNAs may suppress development and maintain arrest. Consistent with this, inhibitors of these miRNAs promoted H. contortus development from L3 to L4 stage, while genetic deletion of C. elegans homologous miRNAs reduced dauer arrest. Epistasis studies with C. elegans daf-2 mutants showed that mir-228 and mir-235 synergise with FOXO transcription factor DAF-16 in the insulin signaling pathway. Target prediction suggests that these miRNAs suppress metabolic and transcription factor activity required for development. Our results provide novel insight into the expression and functions of specific miRNAs in regulating nematode development and identify miRNAs and their target genes as potential therapeutic targets to limit parasite survival within the host.

Purified Tetrastigma hemsleyanum vines polysaccharide attenuates EC-induced toxicity in Caco-2 cells and Caenorhabditis elegans via DAF-16/FOXO pathway

Ethyl Carbamate (EC), as a carcinogen widely found in fermented foods, was verified that its cytotoxicity was associated with oxidative stress. Polysaccharides from natural sources due to their antioxidative capacity have attracted great attention in the past time. In this study, purified polysaccharide from Tetrastigma hemsleyanum vines (TVP) with 64.89 kDA was extracted and conducted multiple analysis to identify its structural information. It could be discovered that TVP was composed of mannose, rhamnose, glucuronic acid, glucose, galactose, and arabinose. In vitro, TVP could inhibit cytotoxicity and genotoxicity, attenuate oxidative damage and mitochondrial dysfunction induced by EC in Caco-2 cells. Meanwhile, TVP could suppress apoptosis by mTOR and Bcl-2 signaling pathways, ameliorate oxidative via Sirt1-FoxO1 and Nrf2-Keap1 signaling pathways. In vivo, EC as well triggered the decline of survival and athletic ability in Caenorhabditis elegans (C. elegans) and TVP could reverse the decline. In the meantime, TVP could ameliorate oxidative damage in N2 and daf-2 (-) mutant but fail in daf-16 (-) mutant, which suggested that DAF-16 (FOXO) might affect the antioxidative protection of TVP in C. elegans. In brief, our results manifested that TVP could attenuate EC-induced cytotoxicity both in vitro and in vivo.

Multigenerational effects of perfluorooctanoic acid on lipid metabolism of Caenorhabditis elegans and its potential mechanism

Per-and polyfluoroalkyl substances (PFASs), especially perfluorooctanoic acid (PFOA), have been showed to induce obesogenic effects which may last over generations. However, the underlying mechanisms are not yet clear. In the present study, wild-type N2 Caenorhabditis elegans and the daf-2 mutant were exposed to PFOA for 4 consecutive generations (F0 to F3) at 1.0 ng/L. Effects on fat content and fat metabolism in the directly exposed F0 to F3 generations, the offspring of F0 (T1 to T3) and also those of F3 (T1′ to T3′). Results showed that PFOA significantly stimulated the fat contents in F0 (with the percentage of the control as 184.1%), T1 (189.5%), F1 (167.3%), F2 (238.0%), T2′ (193.9%) and T3′ (159.4%) while inhibited them in T3 (70%). The changes of fat contents over generations were accompanied with significant changes in enzymes facilitating fatty acid synthesis (e.g., acetyl-CoA carboxylase, fatty acid synthase and desaturase, and glycerol phosphate acyltransferase) and those in fatty acid consumption (e.g., acetyl CoA synthetase, fatty acid transport protein, acyl-CoA oxidase and carnitine palmitoyl transferase). Furthermore, RNA-Seq analysis was performed on F0, F3 and T3 generations. Based on the KEGG analysis of differential genes, PFOA exposure affected lipid metabolism signaling pathways including MAPK, fatty acid degradation, TGF-β signaling pathways. Notably, PFOA exposure provoked significantly different effects in daf-2 nematodes on fat contents, lipid metabolizing enzymes and even different signaling pathways. The overall results demonstrated that the obesogenic effects of PFOA were resulted from a complex combination of various enzymes and pathways with essential involvement of insulin signaling pathway.

Recombinant buckwheat trypsin inhibitor decreases fat accumulation via the IIS pathway in Caenorhabditis elegans.

Buckwheat trypsin inhibitor (BTI) is a low molecular weight polypeptide that can help to prevent metabolic diseases such as obesity, hyperglycemia and hyperlipidemia. Herein, the effects of recombinant BTI (rBTI) on fat accumulation in Caenorhabditis elegans were studied. rBTI prevented fat accumulation under normal and high glucose conditions, and led to significantly shorter body widths without affecting C. elegans feeding behavior. Results also indicate that rBTI altered fat breakdown, synthesis, and accumulation by altering the transcription, expression and activity of key enzymes in lipolysis and fat synthesis. In daf-2 and daf-16 mutants, rBTI did not prevent fat accumulation, indicating that rBTI activity relies on the insulin/insulin-like growth factor (IIS) pathway. Overall rBTI may regulate changes in lipolysis and fat synthesis by down-regulating the IIS pathway, which can affect fat accumulation. These findings support the application of rBTI in preventing obesity, hyperglycemia and hyperlipemia.

Regulation of lifespan by neural excitation and REST.

The mechanisms that extend lifespan in humans are poorly understood. Here we show that extended longevity in humans is associated with a distinct transcriptome signature in the cerebral cortex characterized by downregulation of genes related to neural excitation and synaptic function. In the model system C. elegans, neural excitation increases with age and inhibition of excitation globally, or in glutamatergic or cholinergic neurons, increases longevity. Furthermore, longevity is dynamically regulated by the excitatory-inhibitory balance of neural circuits. The REST transcription factor is upregulated in humans with extended longevity and represses excitation-related genes. Notably, REST-deficient mice exhibit increased cortical activity and neuronal excitability during aging. Similarly, loss-of-function mutations in the C. elegans REST orthologs spr-3 and spr-4 elevate neural excitation and reduce the lifespan of long-lived daf-2 mutants. In wild-type worms, spr-4 overexpression suppresses excitation and extends lifespan. REST, SPR-3/4 and reduced excitation activate the longevity-associated transcription factors FOXO1 and DAF-16 in mammals and worms, respectively. These findings reveal a conserved mechanism of aging mediated by neural circuit activity and regulated by REST.

Intestine-specific activity of insulin signaling pathway in response to microgravity stress in Caenorhabditis elegans

Insulin signaling pathway is conserved and important during the control of biological processes in organisms. In this study, using the simulated microgravity system in Caenorhabditis elegans, we examined the response of insulin signaling pathway to simulated microgravity. After simulated microgravity treatment for 24-h, we observed the significant decrease in expressions of daf-2 encoding an insulin receptor and two genes (age-1 and akt-1) encoding kinase proteins, and increase in expression of daf-16 encoding a FOXO transcriptional factor. Simulated microgravity also induced an obvious translocation and accumulation of DAF-16::GFP signals in the nucleus. Mutation of daf-2, age-1, or akt-1 caused the resistance to toxicity of simulated microgravity, and daf-16 mutation caused the susceptibility to toxicity of simulated microgravity, indicating the protective response of insulin signaling to simulated microgravity. RNA interference (RNAi) knockdown of daf-16 could suppress the resistance of daf-2, age-1, or akt-1 mutant nematodes to toxicity of simulated microgravity, implying the involvement of signaling cascade of DAF-2-AGE-1-AKT-1-DAF-16 in regulating the response to simulated microgravity. Tissue-specific activity analysis demonstrated that the insulin signaling pathway only acted in the intestine to regulate the response to simulated microgravity. Moreover, in the intestine, insulin signaling functioned synergistically with p38 mitogen-activated protein kinase (MAPK) signaling to regulate the response to simulated microgravity. Therefore, our results suggest the crucial role of intestinal insulin signaling pathway in response to simulate microgravity in nematodes.

DAF-16/FOXO promotes taste avoidance learning independently of axonal insulin-like signaling.

The avoidance of starvation is critical for the survival of most organisms, thus animals change behavior based on past nutritional conditions. Insulin signaling is important for nutritional state-dependent behavioral plasticity, yet the underlying regulatory mechanism at the cellular level remains unclear. Previous studies showed that insulin-like signaling is required for taste avoidance learning, in which the nematode Caenorhabditis elegans avoids salt concentrations encountered under starvation conditions. DAF-2c, a splice isoform of the DAF-2 insulin receptor, functions in the axon of the ASER sensory neuron, which senses changes in salt concentrations. In addition, mutants of a major downstream factor of DAF-2, the forkhead transcription factor O (FOXO) homolog DAF-16, show defects in taste avoidance learning. Interestingly, the defect of the daf-2 mutant is not suppressed by daf-16 mutations in the learning, unlike those in other phenomena, such as longevity and development. Here we show that multiple DAF-16 isoforms function in ASER. By epistasis analysis using a DAF-2c isoform-specific mutant and an activated form of DAF-16, we found that DAF-16 acts in the nucleus in parallel with the DAF-2c-dependent pathway in the axon, indicating that insulin-like signaling acts both in the cell body and axon of a single neuron, ASER. Starvation conditioning induces nuclear translocation of DAF-16 in ASER and degradation of DAF-16 before starvation conditioning causes defects in taste avoidance learning. Forced nuclear localization of DAF-16 in ASER biased chemotaxis towards lower salt concentrtions and this effect required the Gq/PKC pathway and neuropeptide processing enzymes. These data imply that DAF-16/FOXO transmits starvation signals and modulates neuropeptide transmission in the learning.

ATGL-1 mediates the effect of dietary restriction and the insulin/IGF-1 signaling pathway on longevity in C. elegans

ObjectiveAnimal lifespan is controlled through genetic pathways that are conserved from nematodes to humans. Lifespan-promoting conditions in nematodes include fasting and a reduction of insulin/IGF signaling. Here we aimed to investigate the input of the Caenorhabditis elegans homologue of the mammalian rate-limiting lipolytic enzyme Adipose Triglyceride Lipase, ATGL-1, in longevity control. MethodsWe used a combination of genetic and biochemical approaches to determine the role of ATGL-1 in accumulation of triglycerides and regulation of longevity. ResultsWe found that expression of ATGL is increased in the insulin receptor homologue mutant daf-2 in a FoxO/DAF-16-dependent manner. ATGL-1 is also up-regulated by fasting and in the eat-2 loss-of-function mutant strain. Overexpression of ATGL-1 increases basal and maximal oxygen consumption rate and extends lifespan in C. elegans. Reduction of ATGL-1 function suppresses longevity of the long-lived mutants eat-2 and daf-2. ConclusionOur results demonstrate that ATGL is required for extended lifespan downstream of both dietary restriction and reduced insulin/IGF signaling.

Translational Regulation of Non-autonomous Mitochondrial Stress Response Promotes Longevity

SUMMARYReduced mRNA translation delays aging, but the underlying mechanisms remain underexplored. Mutations in both DAF-2 (IGF-1 receptor) and RSKS-1 (ribosomal S6 kinase/S6K) cause synergistic lifespan extension in C. elegans. To understand the roles of translational regulation in this process, we performed polysomal profiling and identified translationally regulated ribosomal and cytochrome c (CYC-2.1) genes as key mediators of longevity. cyc-2.1 knockdown significantly extends lifespan by activating the intestinal mitochondrial unfolded protein response (UPRmt), mitochondrial fission, and AMP-activated kinase (AMPK). The germline serves as the key tissue for cyc-2.1 to regulate lifespan, and germline-specific cyc-2.1 knockdown non-autonomously activates intestinal UPRmt and AMPK. Furthermore, the RNA-binding protein GLD-1-mediated translational repression of cyc-2.1 in the germline is important for the non-autonomous activation of UPRmt and synergistic longevity of the daf-2 rsks-1 mutant. Altogether, these results illustrate a translationally regulated non-autonomous mitochondrial stress response mechanism in the modulation of lifespan by insulin-like signaling and S6K.

Fasting prevents hypoxia-induced defects of proteostasis in C. elegans.

Low oxygen conditions (hypoxia) can impair essential physiological processes and cause cellular damage and death. We have shown that specific hypoxic conditions disrupt protein homeostasis in C. elegans, leading to protein aggregation and proteotoxicity. Here, we show that nutritional cues regulate this effect of hypoxia on proteostasis. Animals fasted prior to hypoxic exposure develop dramatically fewer polyglutamine protein aggregates compared to their fed counterparts, indicating that the effect of hypoxia is abrogated. Fasting also reduced the hypoxia-induced exaggeration of proteostasis defects in animals that express Aβ1–42 and in animals with a temperature-sensitive mutation in dyn-1, suggesting that this effect was not specific to polyglutamine proteins. Our data also demonstrate that the nutritional environment experienced at the onset of hypoxia dictates at least some aspects of the physiological response to hypoxia. We further demonstrate that the insulin/IGF-like signaling pathway plays a role in mediating the protective effects of fasting in hypoxia. Animals with mutations in daf-2, the C. elegans insulin-like receptor, display wild-type levels of hypoxia-induced protein aggregation upon exposure to hypoxia when fed, but are not protected by fasting. DAF-2 acts independently of the FOXO transcription factor, DAF-16, to mediate the protective effects of fasting. These results suggest a non-canonical role for the insulin/IGF-like signaling pathway in coordinating the effects of hypoxia and nutritional state on proteostasis.

Recombinant Buckwheat Trypsin Inhibitor Improves the Protein and Mitochondria Homeostasis in Caenorhabditis elegans Model of Aging and Age-Related Disease

Background: With the acceleration of aging process in human society, improvements of the physical functionality and life quality in the elderly population are more meaningful than pure longevity. Buckwheat trypsin inhibitor is a low molecular weight polypeptide extracted from buckwheat, which is a beneficial food for improving the health in the elderly. Objectives: The aim of the current study was to evaluate the potential beneficial effects of recombinant buckwheat trypsin inhibitor (rBTI) on age-dependent function decline and the primary mechanism. Method: Day 10 N2 Caenorhabditis elegans and day 6 AM140 C. elegans cultured at 25°C were used as models of aging and age-related disease, respectively. Motor function was as an indicator of age-dependent function. ATP content and damage mitochondrial DNA mass were detected to assess mitochondrial damage and function by ATP Assay Kit and agarose gel electrophoresis, respectively. Soluble protein content was quantified by SDS polyacrylamide gel electrophoresis. Autophagy-related genes transcription levels, autophagy marker proteins lgg-1, and lysosomal content were analyzed to quantify autophagy levels by qRT-PCR, transgenic C. elegans, and lysosomal staining. Autophagy inhibitor chloroquine, daf-16 mutant, and RNA Interference were used to determine the roles of autophagy and DAF-16 in rBTI-mediated effects. Results: In this study, we found that rBTI could decrease the proportions of insoluble protein and impaired mitochondria, finally reduce motility deficits in both models. Further study indicated that rBTI activated the autophagy, and the inhibition of autophagy reduced rBTI-mediated beneficial effects. Genetic analyses showed the transcriptional activity of DAF-16 was increased by rBTI and was required for rBTI-mediated beneficial effects. Conclusions: These data indicated that rBTI might promote the autophagy to alleviate the age-related functional decline via DAF-16 in C. elegans and suggested a potential role of rBTI as a nutraceutical for the improvement of age-related complications.

Ethanol extracts of Panax notoginseng increase lifespan and protect against oxidative stress in Caenorhabditis elegans via the insulin/IGF-1 signaling pathway

Abstract Panax notoginseng (Burk.) F.H. Chen (PN) has been widely used as an edible and medicinal resource in China, with PN powder being used in dosage form. The present study aimed to investigate the optimal powder size of PN and evaluate its anti-ageing effect in Caenorhabditis elegans. Firstly, four PN powders of different sizes were prepared and their extracts were obtained. These extracts improved the lifespan of Caenorhabditis elegans, with FPE having the greatest effect. Moreover, FPE increased the activity of antioxidant enzymes and reduced the accumulation of reactive oxygen species. FPE also decreased the lipofuscin level and the carbonylated protein content. At the same time, FPE affected the mRNA expression levels of sod-3, hsp-16.2, daf-2, and daf-16 involved in the insulin/IGF-1 signaling pathway, as detected by RT-PCR. Furthermore, the upregulation of SOD-3::GFP and HSP-16.2::GFP following addition of FPE was quantitated using fluorescence. Daf-2 and daf-16 mutants were used for the survival assay, and no life span extension was observed. These observations not only revealed that fine powder is the optimal particle size for PN, but also validated that the anti-ageing effects of PN are mediated by the insulin/IGF-1 signaling pathway.

Radix Tetrastigma flavonoid ameliorates inflammation and prolongs the lifespan of Caenorhabditis elegans through JNK, p38 and Nrf2 pathways

The main flavonoid components of Radix Tetrastigma (RTF) were extracted and identified by UPLC-TOF/MS. In vitro, RTF prevented inflammation in RAW 264.7 cells by suppressing morphological (both cell and nucleus) changes, and decreasing nitric oxide (NO), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) contents. Exposure to LPS also leads to oxidant damage, and RTF alleviated damage to mitochondria, decreased O2− accumulation, and restored the glutathione level. RTF intervention decreased the expression of c-Jun N-terminal kinase (JNK) and p38 phosphorylation, accompanied by downregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and forkhead box protein O1 (FoxO1). In vivo, aging of Caenorhabditis elegans (C. elegans) by paraquat (PQ) was observed through lifespan, lipofuscin, and enzyme analysis. RTF protected against damage in N2 worms but not in daf-16 mutants. Gene expression was further assessed, and p38/PMK-1 and Nrf2/SKN-1 expression in worms was suppressed by PQ, which was reversed by RTF treatment. Together, these results suggested that RTF could help ameliorate inflammation-induced damage through JNK, p38 and Nrf2 pathways.

Cell-autonomous and non-autonomous roles of daf-16 in muscle function and mitochondrial capacity in aging C. elegans.

Sarcopenia, defined as the loss of skeletal muscle mass and strength, contributes to disability and health-related conditions with aging. In vitro studies indicate that age-related mitochondrial dysfunction could play a central role in the development and progression of sarcopenia, but because of limitations in the methods employed, how aging affects muscle mitochondrial function in vivo is not fully understood. We use muscle-targeted fluorescent proteins and the ratiometric ATP reporter, ATeam, to examine changes in muscle mitochondrial mass and morphology, and intracellular ATP levels in C. elegans. We find that the preserved muscle function in aging daf-2 mutants is associated with higher muscle mitochondrial mass, preserved mitochondrial morphology, and higher levels of intracellular ATP. These phenotypes require the daf-16/FOXO transcription factor. Via the tissue-specific rescue of daf-16, we find that daf-16 activity in either muscle or neurons is sufficient to enhance muscle mitochondrial mass, whereas daf-16 activity in the muscle is required for the enhanced muscle function and mobility of the daf-2 mutants. Finally, we show through the use of drugs known to enhance mitochondrial activity that augmenting mitochondrial function leads to improved mobility during aging. These results suggest an important role for mitochondrial function in muscle aging.