The MDT-15 subunit of mediator interacts with dietary restriction to modulate longevity and fluoranthene toxicity in Caenorhabditis elegans

Responses of bitter melon saponins to oxidative stress and aging via the IIS pathway linked with sir-2.1 and hlh-30

Saponins from bitter melon (BMS) exert potential bioactivities and pharmacological activities, including anti-oxidation and lifespan extension. However, the exact mechanisms of BMS in response to oxidative stress remain unknown. Results demonstrated that bitter melon saponins could strengthen locomotive activities (body bend and head thrashing) accompanied by delaying the muscle fiber damage with age in Caenorhabditis elegans. In addition, BMS inhibited the ROS accumulation, improved the activities of antioxidant enzymes like SOD (by 57.90% and 94.34% for 100 μg/ml and 200 μg/ml BMS, respectively) and CAT (by 51.45% and 56.91% for 100 μg/ml and 200 μg/ml BMS, respectively), and extend the lifespan of N2 and CL2006 worms under paraquat-induced oxidative stress. Mechanism study suggested that BMS modulated the mRNA expressions of oxidation-related regulators, like the upregulation of cat-1, hsf-1, sir-2.1, and hlh-30. Furthermore, gene-deficient mutants verified that IIS (insulin/insulin-like growth factor-1 signaling) pathway linked with sir-2.1 and hlh-30 factors were involved in the BMS's lifespan-extension effects under oxidative stress. In general, this study supplemented the explanation of BMS in promoting oxidation-resistance and lifespan-extension activities, which could be served as a potential candidate for anti-aging. PRACTICAL APPLICATIONS: Our previous studies have suggested that saponins from bitter melon exhibited fat-lowering activity in C. elegans. However, little was known about the mechanism underlying the anti-oxidation effects of BMS in C. elegans. Current results indicated that the IIS pathway linked with sir-2.1 and hlh-30 transcriptional factors jointly to increase the lifespan in BMS' responses to oxidative stress. Our findings are beneficial to understand the main nutritional ingredients in bitter melon, which are ideal and expected in functional foods for aging.

Redefining proteostasis transcription factors in organismal stress responses, development, metabolism, and health

Eukaryotic organisms have evolved complex and robust cellular stress response pathways to ensure maintenance of proteostasis and survival during fluctuating environmental conditions. Highly conserved stress response pathways can be triggered and coordinated at the cell-autonomous and cell-nonautonomous level by proteostasis transcription factors, including HSF1, SKN-1/NRF2, HIF1, and DAF-16/FOXO that combat proteotoxic stress caused by environmental challenges. While these transcription factors are often associated with a specific stress condition, they also direct “noncanonical” transcriptional programs that serve to integrate a multitude of physiological responses required for development, metabolism, and defense responses to pathogen infections. In this review, we outline the established function of these key proteostasis transcription factors at the cell-autonomous and cell-nonautonomous level and discuss a newly emerging stress responsive transcription factor, PQM-1, within the proteostasis network. We look beyond the canonical stress response roles of proteostasis transcription factors and highlight their function in integrating different physiological stimuli to maintain cytosolic organismal proteostasis.

MDT-15/MED15 permits longevity at low temperature via enhancing lipidostasis and proteostasis

Low temperatures delay aging and promote longevity in many organisms. However, the metabolic and homeostatic aspects of low-temperature–induced longevity remain poorly understood. Here, we show that lipid homeostasis regulated by Caenorhabditis elegans Mediator 15 (MDT-15 or MED15), a transcriptional coregulator, is essential for low-temperature–induced longevity and proteostasis. We find that inhibition of mdt-15 prevents animals from living long at low temperatures. We show that MDT-15 up-regulates fat-7, a fatty acid desaturase that converts saturated fatty acids (SFAs) to unsaturated fatty acids (UFAs), at low temperatures. We then demonstrate that maintaining a high UFA/SFA ratio is essential for proteostasis at low temperatures. We show that dietary supplementation with a monounsaturated fatty acid, oleic acid (OA), substantially mitigates the short life span and proteotoxicity in mdt-15(-) animals at low temperatures. Thus, lipidostasis regulated by MDT-15 appears to be a limiting factor for proteostasis and longevity at low temperatures. Our findings highlight the crucial roles of lipid regulation in maintaining normal organismal physiology under different environmental conditions.

Low temperatures delay aging and promote longevity in many organisms. This study shows that at low ambient temperatures, Mediator 15, a transcriptional coregulator, allows the nematode Caenorhabditis elegans to live longer by increasing the levels of unsaturated lipids, helping to maintain protein homeostasis.

Adaptive and specialised transcriptional responses to xenobiotic stress in Caenorhabditis elegans are regulated by nuclear hormone receptors

Characterisation of the pathways by which xenobiotics are metabolised and excreted in both target and non-target organisms is crucial for the rational design of effective and specific novel bioactive molecules. Consequently, we have investigated the induced responses of the model nematode Caenorhabditis elegans to a variety of xenobiotics which represent a range of putative modes of action. The majority of genes that were specifically induced in preliminary microarray analyses encoded enzymes from Phase I and II metabolism, including cytochrome P450s, short chain dehydrogenases, UDP-glucuronosyl transferases and glutathione transferases. Changes in gene expression were confirmed by quantitative PCR and GFP induction in reporter strains driven by promoters for transcription of twelve induced enzymes was investigated. The particular complement of metabolic genes induced was found to be highly contingent on the xenobiotic applied. The known regulators of responses to applied chemicals ahr-1, hif-1, mdt-15 and nhr-8 were not required for any of these inducible responses and skn-1 regulated GFP expression from only two of the promoters. Reporter strains were used in conjunction with systematic RNAi screens to identify transcription factors which drive expression of these genes under xenobiotic exposure. These transcription factors appeared to regulate specific xenobiotic responses and have no reported phenotypes under standard conditions. Focussing on nhr-176 we demonstrate the role of this transcription factor in mediating the resistance to thiabendazole.

Caffeine extends life span, improves healthspan, and delays age-associated pathology in Caenorhabditis elegans

BACKGROUND

The longevity of an organism is influenced by both genetic and environmental factors. With respect to genetic factors, a significant effort is being made to identify pharmacological agents that extend life span by targeting pathways with a defined role in the aging process. On the environmental side, the molecular mechanisms responsible for the positive influence of interventions such as dietary restriction are being explored. The environment experienced by humans in modern societies already contains countless compounds that may influence longevity. Understanding the role played by common compounds that substantially affect the aging process will be critical for predicting and interpreting the outcome of introducing new interventions. Caffeine is the most widely used psychoactive drug worldwide. Prior studies in flies, worms, and mice indicate that caffeine may positively impact age-associated neurodegenerative pathology, such as that observed in Alzheimer's disease.

RESULTS

Here we report that caffeine is capable of extending life span and improving healthspan in Caenorhabditis elegans, a finding that is in agreement with a recently published screen looking for FDA-approved compounds capable of extending worm life span. Life span extension using caffeine displays epistatic interaction with two known longevity interventions: dietary restriction and reduced insulin signaling. Caffeine treatment also delays pathology in a nematode model of polyglutamine disease.

CONCLUSIONS

The identification of caffeine as a relevant factor in aging and healthspan in worms, combined with prior work in both humans and rodents linking caffeine consumption to reduced risk of age-associated disease, suggests that caffeine may target conserved longevity pathways. Further, it may be important to consider caffeine consumption when developing clinical interventions, particularly those designed to mimic dietary restriction or modulate insulin/IGF-1-like signaling. The positive impact of caffeine on a worm model of polyglutamine disease suggests that chronic caffeine consumption may generally enhance resistance to proteotoxic stress and may be relevant to assessing risk and developing treatments for human diseases like Alzheimer's and Huntington's disease. Future work addressing the relevant targets of caffeine in models of aging and healthspan will help to clarify the underlying mechanisms and potentially identify new molecular targets for disease intervention.