Selenocysteine modulates resistance to environmental stress and confers anti-aging effects in C. elegans

The impact of cysteine on lifespan in three model organisms: A systematic review and meta-analysis

Cysteine is an amino acid present in thiol proteins and often dictates their secondary structures. Although considered nonessential, cysteine may be essential for patients with certain metabolic diseases and can reduce the requirement for dietary methionine. Cysteine and some of its derivatives, such as N-acetylcysteine, are considered antioxidants and widely used in animal aging studies. To provide insights into the potential anti-aging effects of cysteine, we systematically reviewed and performed a meta-analysis to investigate the impact of cysteine supplementation on lifespan using three model organisms: mice, nematodes, and fruit flies. A total of 13 mouse studies, 13 C. elegans studies, and 5 Drosophila studies were included in the analysis. The findings revealed that cysteine supplementation significantly reduced the risk of mortality in mice and C. elegans. Subgroup analysis showed consistent results across different starting times and administration methods and revealed adverse effects of high doses on worms and a lack of effect in nondisease mouse models. Similar to mice, the effects of cysteine supplementation on Drosophila were not statistically significant, except in transgenic flies. The study identified certain limitations, including the quality of the included studies and the potential for publication bias. We also discussed uncertainties in the underlying molecular mechanisms and the clinical application of dietary cysteine.

Preparation of low molecular weight polysaccharides from Tremella fuciformis by ultrasonic-assisted H2O2-Vc method: Structural characteristics, in vivo antioxidant activity and stress resistance

Different methods were used to degrade Tremella fuciformis polysaccharides (TFP) and prepare low molecular weight polysaccharides of Tremella fuciformis (TFLP) to improve their bioavailability. It was found that the TFLP prepared by ultrasonic-assisted H2O2-Vc method showed the highest level of antioxidant activity and stress resistance in C. elegans. The structural characteristics, in vivo antioxidant and stress resistance of TFLP-1 were evaluated after isolation and purification of TFLP, it was found that TFLP-1 was an acid polysaccharide with a molecular weight of 75770 Da, which mainly composed of mannose. Meanwhile, it could regulate the antioxidant activity and stress resistance in C. elegans by upregulating the transcription of fat-5, fat-7, acs-2, glp-1, hsf-1, hsp-1, mtl-1, nhr-49, skn-1 and sod-3 mRNA. The improvement effects were closely related to the significant regulation of galactose metabolism, alpha linolenic acid metabolism, and pantothenate and CoA biosynthesis metabolic pathways. These results provided insights into the high value application of Tremella fuciformis in the food industry and the development of antioxidant related functional foods.

Sniffer worm, C. elegans, as a toxicity evaluation model organism with sensing and locomotion abilities

Additive manufacturing, or 3D printing, has revolutionized the way we create objects. However, its layer-by-layer process may lead to an increased incidence of local defects compared to traditional casting-based methods. Factors such as light intensity, depth of light penetration, component inhomogeneity, and fluctuations in nozzle temperature all contribute to defect formations. These defective regions can become sources of toxic component leakage, but pinpointing their locations in 3D printed materials remains a challenge. Traditional toxicological assessments rely on the extraction and subsequent exposure of living organisms to these harmful agents, thus only offering a passive detection approach. Therefore, the development of an active system to both identify and locate sources of toxicity is essential in the realm of 3D printing technologies. Herein, we introduce the use of the nematode model organism, Caenorhabditis elegans (C. elegans), for toxicity evaluation. C. elegans exhibits distinctive 'sensing' and 'locomotion' capabilities that enable it to actively navigate toward safe zones while steering clear of hazardous areas. This active behavior sets C. elegans apart from other aquatic and animal models, making it an exceptional choice for immediate and precise identification and localization of toxicity sources in 3D printed materials.

Supplementation with phosphatidylethanolamine confers anti-oxidant and anti-aging effects via hormesis and reduced insulin/IGF-1-like signaling in C. elegans

Phosphatidylethanolamine is a major component of phospholipids with both structural and metabolic functions in cells. Previous studies have revealed that phosphatidylethanolamine can modulate autophagy with a protective effect against age-related diseases. We examined the effect of dietary supplementation with phosphatidylethanolamine on stress response and aging in Caenorhabditis elegans. Phosphatidylethanolamine increased resistance to oxidative stress without effect on heat stress or ultraviolet irradiation. Both mean and maximum lifespans were significantly increased by phosphatidylethanolamine while fertility was reduced as a trade-off. Age-related decline of muscle function was delayed in animals treated with phosphatidylethanolamine. Supplementation with phosphatidylethanolamine suppressed toxic effect of amyloid β and high-glucose diet. Increased ROS levels and induction of stress-responsive genes after dietary supplementation with phosphatidylethanolamine suggest that anti-oxidative stress and anti-aging effects of phosphatidylethanolamine might be though hormesis. Genetic analysis using long-lived mutants and knockdown by RNAi revealed that the lifespan-extending effect of phosphatidylethanolamine overlapped with that of reduced insulin/IGF-1-like signaling and required DAF-16, a downstream transcription factor known to regulate the expression of many stress-responsive genes. These findings indicate that phosphatidylethanolamine has anti-oxidative stress and anti-aging activities with its underlying mechanisms involving hormesis and reduced insulin/IGF-1-like signaling in C. elegans.

2,4-Dichlorophenoxyacetic acid induced hepatic and renal toxicological perturbations in rat model: Attenuation by selenium supplementation

2,4-Dichlorophenoxyacetic acid (2,4-D) is a commercially used herbicide to manage broadleaf weeds that have various toxicological and ecological effects. In view of ever-escalating use of 2,4-D, risk assessment becomes mandatory to ensure the safety of both human health and the ecosystem. Oxidative injury has been expected as a possible mechanism implicated in 2,4-D toxicity. The present study was planned and conducted to explore the antioxidant potential of selenium (Se) supplementation to moderate the 2,4-D hepatic and renal toxicity in a rat model. The rats were randomly assigned to four equal groups and treated via oral gavage for a period of 4 weeks. Group I: received deionized water as a vehicle, group II: received 2,4-D (150 mg^-1 kg^-1 day^-1), group III: received Se supplement (1 mg^-1 kg^-1 day^-1), and group IV: received 2,4-D (150 mg^-1 kg^-1 day^-1) and Se supplement (1 mg^-1 kg^-1 day^-1) simultaneously. After 4 weeks of administration, 2,4-D induced toxicity was observed, as manifested by disrupted levels of plasma urea, creatinine, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). Further, 2,4-D caused a considerable increase in tissue malondialdehyde (MDA) levels and decreased activity of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione reductase. Se supplementation exhibited its antioxidant properties by significantly improving urea, creatinine, ALP, AST, and ALT, and MDA levels and antioxidant enzyme activities. In conclusion, the results suggest that 2,4-D induced hepatic and renal toxicities were attenuated by Se supplementation probably owing to its antioxidant properties.

Cur2004-8, a synthetic curcumin derivative, extends lifespan and modulates age-related physiological changes in Caenorhabditis elegans

Curcumin, a compound found in Indian yellow curry, is known to possess various biological activities, including anti-oxidant, anti-inflammatory, and anti-cancer activities. Cur2004-8 is a synthetic curcumin derivative having symmetrical bis-alkynyl pyridines that shows a strong anti-angiogenic activity. In the present study, we examined the effect of dietary supplementation with Cur2004-8 on response to environmental stresses and aging using Caenorhabditis elegans as a model system. Dietary intervention with Cur2004-8 significantly increased resistance of C. elegans to oxidative stress. Its anti-oxidative-stress effect was greater than curcumin. However, response of C. elegans to heat stress or ultraviolet irradiation was not significantly affected by Cur2004-8. Next, we examined the effect of Cur2004-8 on aging. Cur2004-8 significantly extended both mean and maximum lifespan, accompanying a shift in time-course distribution of progeny production. Age-related decline in motility was also delayed by supplementation with Cur2004-8. In addition, Cur2004-8 prevented amyloid-beta-induced toxicity in Alzheimer's disease model animals which required a forkhead box (FOXO) transcription factor DAF-16. Dietary supplementation with Cur2004-8 also reversed the increase of mortality observed in worms treated with high-glucose-diet. These results suggest that Cur2004-8 has higher anti-oxidant and anti-aging activities than curcumin. It can be used for the development of novel anti-aging product.

Of Mice, Whales, Jellyfish and Men: In Pursuit of Increased Longevity

The quest for increased human longevity has been a goal of mankind throughout recorded history. Recent molecular studies are now providing potentially useful insights into the aging process which may help to achieve at least some aspects of this quest. This chapter will summarize the main findings of these studies with a focus on long-lived mutant mice and worms, and the longest living natural species including Galapagos giant tortoises, bowhead whales, Greenland sharks, quahog clams and the immortal jellyfish.

Selenocysteine mimics the effect of dietary restriction on lifespan via SKN‑1 and retards age‑associated pathophysiological changes in Caenorhabditis elegans

Selenocysteine, a sulfur-containing amino acid, can modulate cellular oxidative stress defense systems by incorporating into anti-oxidant enzymes such as glutathione peroxidase and thioredoxin reductase. Selenocysteine can also prevent cancer, neurodegenerative diseases and cardiovascular diseases. A recent study revealed that dietary supplementation with selenocysteine can increase the resistance of Caenorhabditis elegans to environmental stressors and its lifespan. The objective of the present study was to identify the underlying mechanism involved in the lifespan-extending effect of selenocysteine and the effect of selenocysteine on age-associated pathophysiological changes. Lifespan assays with known long-lived mutants of age-1 (the ortholog of the phosphoinositide 3-kinase), clk-1 (the ortholog of demethoxyubiquinone hydroxylase) and eat-2 (a ligand-gated ion channel subunit) revealed that the effect of selenocysteine on lifespan specifically overlapped with that of the eat-2 mutation, a genetic model of dietary restriction (DR). Selenocysteine mimicked the effect of DR on the bacterial dilution method. It required SKN-1 (the ortholog of mammalian nuclear factor-erythroid-related factor) for lifespan extension. In addition, selenocysteine significantly delayed the paralysis induced by human amyloid-β gene, positively correlated with the incidence of Alzheimer's disease. The effect of selenocysteine on amyloid-β-induced toxicity was dependent on the nuclear localization of DAF-16. Reduced survival caused by high-glucose-diet was recovered by selenocysteine. Selenocysteine also reduced the cellular level of reactive oxygen species known to be increased by high-glucose-diet. The results of the present study suggested that selenocysteine can mimic the effect of DR on lifespan and age-associated pathophysiological alterations, providing scientific evidence for the development of DR mimetics using selenocysteine.

Antioxidant effects of selenocysteine on replicative senescence in human adipose-derived mesenchymal stem cells

In most clinical applications, human mesenchymal stem cells (hMSCs) are expanded in large scale before their administration. Prolonged culture in vitro results in cellular senescence-associated phenotypes, including accumulation of reactive oxygen species (ROS) and decreased cell viabilities. Profiling of stem cell-related genes during in vitro expansion revealed that numerous canonical pathways were significantly changed. To determine the effect of selenocysteine (Sec), a rare amino acid found in several antioxidant enzymes, on the replicative senescence in hMSCs, we treated senescent hMSCs with Sec. Supplementation of Sec in the culture medium in late-passage hMSCs reduced ROS levels and improved the survival of hMSCs. In addition, a subset of key antioxidant genes and Sec-containing selenoproteins showed increased mRNA levels after Sec treatment. Furthermore, ROS metabolism and inflammation pathways were predicted to be downregulated. Taken together, our results suggest that Sec has antioxidant effects on the replicative senescence of hMSCs.