Coherent anti-Stokes Raman scattering (CARS) spectroscopy in Caenorhabditis elegans and Globodera pallida: evidence for an ivermectin-activated decrease in lipid stores.

BACKGROUND: Macrocyclic lactones are arguably the most successful chemical class with efficacy against parasitic nematodes. Here we investigated the effect of the macrocyclic lactone ivermectin on lipid homeostasis in the plant parasitic nematode Globodera pallida and provide new insight into its mode of action. RESULTS: A non-invasive, non-destructive, label-free and chemically selective technique called Coherent anti-Stokes Raman scattering (CARS) spectroscopy was used to study lipid stores in G. pallida. We optimised the protocol using the free-living nematode Caenorhabditis elegans and then used CARS to quantify lipid stores in the pre-parasitic, non-feeding J2 stage of G. pallida. This revealed a concentration of lipid stores in the posterior region of J2 s within 24 h of hatching which decreased to undetectable levels over the course of 28 days. We tested the effect of ivermectin on J2 viability and lipid stores. Within 24 h, ivermectin paralysed J2 s. Counterintuitively, over the same time-course ivermectin increased the rate of depletion of J2 lipid, suggesting that in ivermectin-treated J2 s there is a disconnection between the energy requirements for motility and metabolic rate. This decrease in lipid stores would be predicted to negatively impact on J2 infective potential. CONCLUSION: These data suggest that the benefit of macrocyclic lactones as seed treatments may be underpinned by a multilevel effect involving both neuromuscular inhibition and acceleration of lipid metabolism. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Multiple excitatory and inhibitory neural signals converge to fine-tune Caenorhabditis elegans feeding to food availability.

How an animal matches feeding to food availability is a key question for energy homeostasis. We addressed this in the nematode Caenorhabditis elegans, which couples feeding to the presence of its food (bacteria) by regulating pharyngeal activity (pumping). We scored pumping in the presence of food and over an extended time course of food deprivation in wild-type and mutant worms to determine the neural substrates of adaptive behavior. Removal of food initially suppressed pumping but after 2 h this was accompanied by intermittent periods of high activity. We show pumping is fine-tuned by context-specific neural mechanisms and highlight a key role for inhibitory glutamatergic and excitatory cholinergic/peptidergic drives in the absence of food. Additionally, the synaptic protein UNC-31 [calcium-activated protein for secretion (CAPS)] acts through an inhibitory pathway not explained by previously identified contributions of UNC-31/CAPS to neuropeptide or glutamate transmission. Pumping was unaffected by laser ablation of connectivity between the pharyngeal and central nervous system indicating signals are either humoral or intrinsic to the enteric system. This framework in which control is mediated through finely tuned excitatory and inhibitory drives resonates with mammalian hypothalamic control of feeding and suggests that fundamental regulation of this basic animal behavior may be conserved through evolution from nematode to human.

Metabolomics analysis uncovers that dietary restriction buffers metabolic changes associated with aging in Caenorhabditis elegans.

Dietary restriction (DR) is one of the most universal means of extending lifespan. Yet, whether and how DR specifically affects the metabolic changes associated with aging is essentially unknown. Here, we present a comprehensive and unbiased picture of the metabolic variations that take place with age at the whole organism level in Caenorhabditis elegans by using (1)H high-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) analysis of intact worms. We investigate metabolic variations potentially important for lifespan regulation by comparing the metabolic fingerprint of two previously described genetic models of DR, the long-lived eat-2(ad465) and slcf-1(tm2258) worms, as single mutants or in combination with a genetic suppressor of their lifespan phenotype. Our analysis shows that significant changes in metabolite profiles precede the major physiological decline that accompanies aging and that DR protects from some of those metabolic changes. More specifically, low phosphocholine (PCho) correlates with high life expectancy. A mutation in the tumor suppressor gene PTEN/DAF-18, which suppresses the beneficial effects of DR in both C. elegans and mammals, increases both PCho level and choline kinase expression. Furthermore, we show that choline kinase function in the intestine can regulate lifespan. This study highlights the relevance of NMR metabolomic approaches for identifying potential biomarkers of aging.

Meeting report: 2012 Caenorhabditis elegans Neurobiology meeting, EMBL Advanced Training Centre, Germany.

Some of the finest minds in the field of Caenorhabditis elegans neurobiology were brought together from 14 June to 17 June 2012 in the small, quaint and picturesque German city of Heidelberg for the biannual C. elegans neurobiology conference. Held at the EMBL Advanced Training Centre and wonderfully organised by Diah Yulianti, Jean-Louis Bessereau, Gert Jansen and William Schafer, the meeting contained 62 verbal presentations and hundreds of posters that were displayed around the double-helical walkways that looped throughout the conference centre. Presentations on recent advances in microfluidics, cell ablation and targeted gene expression exemplified the strengths of C. elegans as a model organism, with these advances allowing detailed high-throughput analysis and study. Interesting behaviours that were previously poorly characterised were widely discussed, as were the advantages of C. elegans as a model for neurodevelopment and neurodegeneration and the investigation of neuropeptide function. The examples discussed in this meeting report seek to illustrate the breadth and depth of presentations given on these recurring topics.

Pyruvate imbalance mediates metabolic reprogramming and mimics lifespan extension by dietary restriction in Caenorhabditis elegans.

Dietary restriction (DR) is the most universal intervention known to extend animal lifespan. DR also prevents tumor development in mammals, and this effect requires the tumor suppressor PTEN. However, the metabolic and cellular processes that underly the beneficial effects of DR are poorly understood. We identified slcf-1 in an RNAi screen for genes that extend Caenorhabditis elegans lifespan in a PTEN/daf-18-dependent manner. We showed that slcf-1 mutation, which increases average lifespan by 40%, mimics DR in worms fed ad libitum. An NMR-based metabolomic characterization of slcf-1 mutants revealed lower lipid levels compared to wild-type animals, as expected for dietary-restricted animals, but also higher pyruvate content. Epistasis experiments and metabolic measurements support a model in which the long lifespan of slcf-1 mutants relies on increased mitochondrial pyruvate metabolism coupled to an adaptive response to oxidative stress. This response requires DAF-18/PTEN and the previously identified DR effectors PHA-4/FOXA, HSF-1/HSF1, SIR-2.1/SIRT-1, and AMPK/AAK-2. Overall, our data show that pyruvate homeostasis plays a central role in lifespan control in C. elegans and that the beneficial effects of DR results from a hormetic mechanism involving the mitochondria. Analysis of the SLCF-1 protein sequence predicts that slcf-1 encodes a plasma membrane transporter belonging to the conserved monocarboxylate transporter family. These findings suggest that inhibition of this transporter homolog in mammals might also promote a DR response.

Life span extension by resveratrol, rapamycin, and metformin: The promise of dietary restriction mimetics for an healthy aging.

Life expectancy at the turn of the 20th century was 46 years on average worldwide and it is around 65 years today. The correlative increase in age-associated diseases incidence has a profound public health impact and is an important matter of concern for our societies. Aging is a complex, heterogeneous, and multifactorial phenomenon, which is the consequence of multiple interactions between genes and environment. In this review, we survey animals models that have been of great help for both investigating mechanism of aging and identifying molecules, which slow down the onset of age-related diseases. Resveratrol (RSV) is one of those. We will report evidences supporting RSV as a molecule that acts by mimicking the beneficial effects of dietary restriction, and may share common downstream targets with rapamycin and metformin. Although those molecules do not reveal all the secrets of the fountain of youth, they may help us maintaining the quality of life in the old age.