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The DAF-2/insulin/insulin-like growth factor signaling (IIS) pathway plays an evolutionarily conserved role in regulating reproductive development, life span, and stress resistance. In Caenorhabditis elegans, DAF-2/IIS signaling is modulated by an extensive array of insulin-like peptides (ILPs) with diverse spatial and temporal expression patterns. However, the release dynamics and specific functions of these ILPs in adapting to different environmental conditions remain poorly understood. Here, we show that the ILP, insulin-3 (INS-3), plays a crucial role in modulating the response to various environmental stressors in C. elegans. ins-3 mutants display increased resistance to heat, oxidative stress, and starvation; however, this advantage is countered by slower reproductive development under favorable conditions. We find that ins-3 expression is downregulated in response to environmental stressors, whereas, the neurohormone tyramine, which is released during the acute flight response, increases ins-3 expression. We show that tyramine induces intestinal calcium (Ca2+) transients through the activation of the TYRA-3 receptor. Our data support a model in which tyramine negatively impacts environmental stress resistance by stimulating the release of INS-3 from the intestine via the activation of a TYRA-3-Gαq-IP3 pathway. The release of INS-3 systemically activates the DAF-2 pathway, resulting in the inhibition of cytoprotective mechanisms mediated by DAF-16/FOXO. These studies offer mechanistic insights into a brain–gut communication pathway that weighs adaptive strategies to respond to acute and long-term stressors. The flight response in worms induces changes in insulin signaling that promote short-term metabolic benefits at the cost of decreased cytoprotective mechanisms. Here, the authors define a brain-gut pathway mediating this adaptive tradeoff, wherein TYRA-3 stimulates INS-3 expression in the intestine, leading to the systemic activation of insulin signaling and reduced stress resistance. [ABSTRACT FROM AUTHOR]

A finely tuned balance between excitation and inhibition (E/I) is essential for proper brain function. Disruptions in the GABAergic system, which alter this equilibrium, are a common feature in various types of neurological disorders, including autism spectrum disorders (ASDs). Mutations in Phosphatase and Tensin Homolog (PTEN), the main negative regulator of the phosphatidylinositol 3-phosphate kinase/Akt pathway, are strongly associated with ASD. However, it is unclear whether PTEN deficiencies can differentially affect inhibitory and excitatory signaling. Using the Caenorhabditis elegans neuromuscular system, where both excitatory (cholinergic) and inhibitory (GABAergic) inputs regulate muscle activity, we found that daf-18/PTEN mutations impact GABAergic (but not cholinergic) neurodevelopment and function. This selective impact results in a deficiency in inhibitory signaling. The defects observed in the GABAergic system in daf-18/PTEN mutants are due to reduced activity of DAF-16/FOXO during development. Ketogenic diets (KGDs) have proven effective for disorders associated with E/I imbalances. However, the mechanisms underlying their action remain largely elusive. We found that a diet enriched with the ketone body β-hydroxybutyrate during early development induces DAF-16/FOXO activity, therefore improving GABAergic neurodevelopment and function in daf-18/PTEN mutants. Our study provides valuable insights into the link between PTEN mutations and neurodevelopmental defects and delves into the mechanisms underlying the potential therapeutic effects of KGDs. [ABSTRACT FROM AUTHOR]

Therapeutic drug development is a long, expensive, and complex process that usually takes 12-15 years. In the early phases of drug discovery, in particular, there is a growing need for animal models that ensure the reduction in both cost and time. Caenorhabditis elegans has been traditionally used to address fundamental aspects of key biological processes, such as apoptosis, aging, and gene expression regulation. During the last decade, with the advent of large-scale platforms for screenings, this invertebrate has also emerged as an essential tool in the pharmaceutical research industry to identify novel drugs and drug targets. In this review, we discuss the reasons why C. elegans has been positioned as an outstanding cost-effective option for drug discovery, highlighting both the advantages and drawbacks of this model. Particular attention is paid to the suitability of this nematode in large-scale genetic and pharmacological screenings. High-throughput screenings in C. elegans have indeed contributed to the breakthrough of a wide variety of candidate compounds involved in extensive fields including neurodegeneration, pathogen infections and metabolic disorders. The versatility of this nematode, which enables its instrumentation as a model of human diseases, is another attribute also herein underscored. As illustrative examples, we discuss the utility of C. elegans models of both human neurodegenerative diseases and parasitic nematodes in the drug discovery industry. Summing up, this review aims to demonstrate the impact of C. elegans models on the drug discovery pipeline. [ABSTRACT FROM AUTHOR]

The DAF-2/insulin/insulin-like growth factor signaling (IIS) pathway plays an evolutionarily conserved role in regulating reproductive development, lifespan, and stress resistance. In C. elegans , DAF-2/IIS signaling is modulated by an extensive array of insulin-like peptides (ILPs) with diverse spatial and temporal expression patterns. However, the release dynamics and specific functions of these ILPs in adapting to different environmental conditions remain poorly understood. Here, we show that the ILP, INS-3, plays a crucial role in modulating the response to different types of stressors in C. elegans . ins-3 mutants display increased resistance to both heat and oxidative stress; however, under favorable conditions, this advantage is countered by slower reproductive development. ins-3 expression in both neurons and the intestine is downregulated in response to environmental stressors. Conversely, the neurohormone tyramine, which is released during the acute flight response, triggers an upregulation in ins-3 expression. Moreover, we found that tyramine negatively impacts environmental stress resistance by stimulating the release of INS-3 from the intestine. The subsequent release of INS-3 systemically activates the DAF-2 pathway, resulting in the inhibition of cytoprotective mechanisms mediated by DAF-16/FOXO and HSF-1. These studies offer mechanistic insights into the brain-gut communication pathway that weighs adaptive strategies to respond to acute and long-term stress scenarios.