A C. elegans model to study human metabolic regulation

Free and Easy Wanderer Ameliorates Intestinal Bloating-Dependent Avoidance Behavior of Caenorhabditis elegans Through Gut-Germline-Neural Signaling

PURPOSE

The aim of this study was to investigate the protective effect of Free and Easy Wanderer (FAEW) on the avoidance behavior induced by feeding Heat-Killed Escherichia coli, and to elucidate the underlying mechanisms.

METHODS

Initially, the effects of FAEW on avoidance behavior, survival, neuroendocrine signaling gene expression, and intestinal bloating were examined. The impact of FAEW on gut-germline-neural signaling was assessed by monitoring H4K8ac expression and the avoidance behavior of par-5 RNAi animals and glp-1(e2141) mutants. RNA-sequencing was conducted to analyze potential signaling pathways. Finally, avoidance behavior was examined using daf-16(mu86) mutants and the rescued animals.

RESULTS

FAEW delayed avoidance behavior. FAEW significantly downregulated gene expression in the neuroendocrine signaling pathway and alleviated intestinal bloating of C. elegans. The levels of H4K8ac and par-5 in the germline decreased significantly with FAEW's treatment, and FAEW failed to affect the avoidance behavior of par-5 RNAi animals and glp-1(e2141) mutants. FAEW's effect on avoidance behavior diminished in daf-16(mu86) mutants but was restored in daf-16 rescued animals. FAEW has been observed to restore daf-16 levels.

CONCLUSION

FAEW protects against avoidance behavior of C. elegans through downregulating H4K8ac protein expression and activating DAF-16. This study provides crucial experimental evidence supporting FAEW as a promising candidate for protecting against avoidance behavior associated with PTSD.

Intestinal Development and Gut Disease: Contributions From the Caenorhabditis elegans Model

The mammalian intestine is a highly organized and complex system essential for nutrient absorption, immune response, and homeostasis. Disruptions in its development can lead to various gut diseases, ranging from congenital anomalies to inflammatory and neoplastic disorders. Caenorhabditis elegans (C elegans) has emerged as a valuable model organism for studying intestinal development and gut diseases due to its genetic tractability and transparent body. This review explores the significant contributions of C elegans research to our understanding of intestinal biology, examining historical milestones, anatomical and physiological insights, and its utility in modeling gut diseases and drug discovery. We also draw comparative insights into mammalian systems and propose future research directions. The findings highlight the potential of C elegans as an essential model system for advancing our knowledge of intestinal development and its implications for human health.

Caffeine-Induced Upregulation of pas-1 and pas-3 Enhances Intestinal Integrity by Reducing Vitellogenin in Aged Caenorhabditis elegans Model

Background: Intestinal aging is characterized by declining protein homeostasis via reduced proteasome activity, which are hallmarks of age-related diseases. Our previous study showed that caffeine intake improved intestinal integrity with age by reducing vitellogenin (VIT, yolk protein) in C. elegans. In this study, we investigated the regulatory mechanisms by which caffeine intake improves intestinal integrity and reduces vitellogenin (VIT) production in aged Caenorhabditis elegans. Methods: We performed RNA-seq analysis, and qRT-PCR to validate and confirm the RNA-seq results. Transgenic worms with VIT-2::GFP and VIT-6::GFP were used for measuring VIT production. dsRNAi was conducted to elucidate the roles of pas-1 and pas-3 genes. Results:pas-1 and pas-3, a C. elegans ortholog of human PASM4, was upregulated by caffeine intake. They reduced VIT production by repressing unc-62, a transcriptional activator of vit expression. Interestingly, vit-2 was required for pas-1 and pas-3 expression, and RNAi of pas-1 and pas-3 promoted intestinal atrophy and colonization, suggesting a balancing mechanism for VIT levels in intestinal health. Additionally, lifespan was extended by caffeine intake (2 ± 0.05 days), however, this effect was not observed by pas-1 but not pas-3 RNAi, suggesting that the mode of action for an anti-aging effect of caffeine through pas-1 and pas-3 is distinctive. The lifespan extended by pas-1 was mediated by SKN-1 activation. Conclusions: Caffeine intake enhances intestinal health through proteasome activity and extends lifespan in aged C. elegans by upregulating pas-1 and pas-3. These findings suggest that caffeine consumption mitigates age-related proteasome impairment and maintains intestinal integrity during aging.

Oral nanotherapeutic formulation of insulin with reduced episodes of hypoglycaemia

Injectable insulin is an extensively used medication with potential life-threatening hypoglycaemic events. Here we report on insulin-conjugated silver sulfide quantum dots coated with a chitosan/glucose polymer to produce a responsive oral insulin nanoformulation. This formulation is pH responsive, is insoluble in acidic environments and shows increased absorption in human duodenum explants and Caenorhabditis elegans at neutral pH. The formulation is sensitive to glucosidase enzymes to trigger insulin release. It is found that the formulation distributes to the liver in mice and rats after oral administration and promotes a dose-dependent reduction in blood glucose without promoting hypoglycaemia or weight gain in diabetic rodents. Non-diabetic baboons also show a dose-dependent reduction in blood glucose. No biochemical or haematological toxicity or adverse events were observed in mice, rats and non-human primates. The formulation demonstrates the potential to orally control blood glucose without hypoglycaemic episodes.

Kombucha Tea-associated microbes remodel host metabolic pathways to suppress lipid accumulation

The popularity of the ancient, probiotic-rich beverage Kombucha Tea (KT) has surged in part due to its purported health benefits, which include protection against metabolic diseases; however, these claims have not been rigorously tested and the mechanisms underlying host response to the probiotics in KT are unknown. Here, we establish a reproducible method to maintain C. elegans on a diet exclusively consisting of Kombucha Tea-associated microbes (KTM), which mirrors the microbial community found in the fermenting culture. KT microbes robustly colonize the gut of KTM-fed animals and confer normal development and fecundity. Intriguingly, animals consuming KTMs display a marked reduction in total lipid stores and lipid droplet size. We find that the reduced fat accumulation phenotype is not due to impaired nutrient absorption, but rather it is sustained by a programed metabolic response in the intestine of the host. KTM consumption triggers widespread transcriptional changes within core lipid metabolism pathways, including upregulation of a suite of lysosomal lipase genes that are induced during lipophagy. The elevated lysosomal lipase activity, coupled with a decrease in lipid droplet biogenesis, is partially required for the reduction in host lipid content. We propose that KTM consumption stimulates a fasting-like response in the C. elegans intestine by rewiring transcriptional programs to promote lipid utilization. Our results provide mechanistic insight into how the probiotics in Kombucha Tea reshape host metabolism and how this popular beverage may impact human metabolism.

Partners in diabetes epidemic: A global perspective

There is a recent increase in the worldwide prevalence of both obesity and diabetes. In this review we assessed insulin signaling, genetics, environment, lipid metabolism dysfunction and mitochondria as the major determinants in diabetes and to identify the potential mechanism of gut microbiota in diabetes diseases. We searched relevant articles, which have key information from laboratory experiments, epidemiological evidence, clinical trials, experimental models, meta-analysis and review articles, in PubMed, MEDLINE, EMBASE, Google scholars and Cochrane Controlled Trial Database. We selected 144 full-length articles that met our inclusion and exclusion criteria for complete assessment. We have briefly discussed these associations, challenges, and the need for further research to manage and treat diabetes more efficiently. Diabetes involves the complex network of physiological dysfunction that can be attributed to insulin signaling, genetics, environment, obesity, mitochondria and stress. In recent years, there are intriguing findings regarding gut microbiome as the important regulator of diabetes. Valid approaches are necessary for speeding medical advances but we should find a solution sooner given the burden of the metabolic disorder - What we need is a collaborative venture that may involve laboratories both in academia and industries for the scientific progress and its application for the diabetes control.

KLF regulation of insulin pathway genes

Alteration in lipid metabolism can result in fat accumulation in adipose tissues, which may lead to two most important human diseases, obesity and diabetes. A shift in lipid metabolism deregulates signaling pathways which regulates obesity and/or diabetes. In this study, we examined the components of insulin/ TGF-β pathways and their genetic interaction with Krüppel-like transcription factors (KLFs). Their role in energy homeostasis were discussed. We separately created klf/daf genes double mutants by carrying out klfs RNAi on daf-2 (e1391), daf-4 (e1364), daf-7 (e1372); dpy-1 (e1), daf-14 (m77), daf-16 (mgDf50) mutants. And then conducted Oil O Red staining to assay the klf/daf RNAi worms for fat deposits and examine genetic interaction between klfs and daf genes. The results showed that worms bearing klf-1, 2, or 3 and daf-2, or daf-4 mutations deposit large, but similar fat levels as individual mutants. The results suggested that they target the same molecular pathway of fat storage. klf-1, 2 or 3 RNAi /daf-7 worms showed higher fat deposits in klf-1, 2, or 3 RNAi/daf-7 worms than klf-1, 2, or 3 RNAi or daf-7 mutants alone, which showed a functional interaction between klfs and daf-7 in perhaps TGF-β-like pathway. Altogether our study suggests a direct role of klfs in insulin signaling pathway.

See the Unseen: Red-Emissive Carbon Dots for Visualizing the Nucleolar Structures in Two Model Animals and In Vivo Drug Toxicity

Nucleolus, which participates in many crucial cellular activities, is an ideal target for evaluating the state of a cell or an organism. Here, bright red-emissive carbon dots (termed CPCDs) with excitation-independent/polarity-dependent fluorescence emission are synthesized by a one-step hydrothermal reaction between congo red and p-phenylenediamine. The CPCDs can achieve wash-free, real-time, long-term, and high-quality nucleolus imaging in live cells, as well as in vivo imaging of two common model animals-zebrafish and Caenorhabditis elegans (C. elegans). Strikingly, CPCDs realize the nucleolus imaging of organs/flowing blood cells in zebrafish at a cellular level for the first time, and the superb nucleolus imaging of C. elegans suggests that the germ cells in the spermatheca probably have no intact nuclei. These previously unachieved imaging results of the cells/tissues/organs may guide the zebrafish-related studies and benefit the research of C. elegans development. More importantly, a novel strategy based on CPCDs for in vivo toxicity evaluation of materials/drugs (e.g., Ag⁺ ), which can visualize the otherwise unseen injuries in zebrafish, is developed. In conclusion, the CPCDs represent a robust tool for visualizing the structures and dynamic behaviors of live zebrafish and C. elegans, and may find important applications in cell biology and toxicology.

An antisteatosis response regulated by oleic acid through lipid droplet-mediated ERAD enhancement

Although excessive lipid accumulation is a hallmark of obesity-related pathologies, some lipids are beneficial. Oleic acid (OA), the most abundant monounsaturated fatty acid (FA), promotes health and longevity. Here, we show that OA benefits Caenorhabditis elegans by activating the endoplasmic reticulum (ER)-resident transcription factor SKN-1A (Nrf1/NFE2L1) in a lipid homeostasis response. SKN-1A/Nrf1 is cleared from the ER by the ER-associated degradation (ERAD) machinery and stabilized when proteasome activity is low and canonically maintains proteasome homeostasis. Unexpectedly, OA increases nuclear SKN-1A levels independently of proteasome activity, through lipid droplet-dependent enhancement of ERAD. In turn, SKN-1A reduces steatosis by reshaping the lipid metabolism transcriptome and mediates longevity from OA provided through endogenous accumulation, reduced H3K4 trimethylation, or dietary supplementation. Our findings reveal an unexpected mechanism of FA signal transduction, as well as a lipid homeostasis pathway that provides strategies for opposing steatosis and aging, and may mediate some benefits of the OA-rich Mediterranean diet.

Perspective: Leveraging the Gut Microbiota to Predict Personalized Responses to Dietary, Prebiotic, and Probiotic Interventions

Humans often show variable responses to dietary, prebiotic, and probiotic interventions. Emerging evidence indicates that the gut microbiota is a key determinant for this population heterogeneity. Here, we provide an overview of some of the major computational and experimental tools being applied to critical questions of microbiota-mediated personalized nutrition and health. First, we discuss the latest advances in in silico modeling of the microbiota-nutrition-health axis, including the application of statistical, mechanistic, and hybrid artificial intelligence models. Second, we address high-throughput in vitro techniques for assessing interindividual heterogeneity, from ex vivo batch culturing of stool and continuous culturing in anaerobic bioreactors, to more sophisticated organ-on-a-chip models that integrate both host and microbial compartments. Third, we explore in vivo approaches for better understanding of personalized, microbiota-mediated responses to diet, prebiotics, and probiotics, from nonhuman animal models and human observational studies, to human feeding trials and crossover interventions. We highlight examples of existing, consumer-facing precision nutrition platforms that are currently leveraging the gut microbiota. Furthermore, we discuss how the integration of a broader set of the tools and techniques described in this piece can generate the data necessary to support a greater diversity of precision nutrition strategies. Finally, we present a vision of a precision nutrition and healthcare future, which leverages the gut microbiota to design effective, individual-specific interventions.

Effects of High Dietary Carbohydrate and Lipid Intake on the Lifespan of C. elegans

Health and lifespan are influenced by dietary nutrients, whose balance is dependent on the supply or demand of each organism. Many studies have shown that an increased carbohydrate–lipid intake plays a critical role in metabolic dysregulation, which impacts longevity. Caenorhabditis elegans has been successfully used as an in vivo model to study the effects of several factors, such as genetic, environmental, diet, and lifestyle factors, on the molecular mechanisms that have been linked to healthspan, lifespan, and the aging process. There is evidence showing the causative effects of high glucose on lifespan in different diabetic models; however, the precise biological mechanisms affected by dietary nutrients, specifically carbohydrates and lipids, as well as their links with lifespan and longevity, remain unknown. Here, we provide an overview of the deleterious effects caused by high-carbohydrate and high-lipid diets, as well as the molecular signals that affect the lifespan of C. elegans; thus, understanding the detailed molecular mechanisms of high-glucose- and lipid-induced changes in whole organisms would allow the targeting of key regulatory factors to ameliorate metabolic disorders and age-related diseases.

High-speed label-free confocal microscopy of Caenorhabditis elegans with near infrared spectrally encoded confocal microscopy

Caenorhabditis elegans (C. elegans) is an optically transparent nematode that shares many gene orthologs and homologs with humans. C. elegans are widely used in large populations for genetic studies relevant to human biology and disease. Success of such studies frequently relies on the ability to image C. elegans structure at high-resolution and high-speed. In this manuscript, we report on the feasibility and suitability of a high-speed variant of reflectance confocal microscopy, known as spectrally encoded confocal microscopy (SECM), for label-free imaging of C. elegans. The developed system utilizes near-infrared illumination in conjunction with refractive and diffractive optics to instantaneously image a confocal image line at a speed of up to 147 kHz with lateral and axial resolutions of 2µm and 10µm, respectively. Our imaging results from wild-type C. elegans and four mutant strains (MT2124, MT1082, CB61, and CB648) demonstrate the ability of SECM in revealing the overall geometry, key internal organs, and mutation-induced structural variations, opening the door for downstream integration of SECM in microfluidic platforms for high throughput structural imaging of C. elegans.

α-ketoglutarate delays age-related fertility decline in mammals

The fecundity reduction with aging is referred as the reproductive aging which comes earlier than that of chronological aging. Since humans have postponed their childbearing age, to prolong the reproductive age becomes urgent agenda for reproductive biologists. In the current study, we examined the potential associations of α-ketoglutarate (α-KG) and reproductive aging in mammals including mice, swine, and humans. There is a clear tendency of reduced α-KG level with aging in the follicle fluids of human. To explore the mechanisms, mice were selected as the convenient animal model. It is observed that a long term of α-KG administration preserves the ovarian function, the quality and quantity of oocytes as well as the telomere maintaining system in mice. α-KG suppresses ATP synthase and alterations of the energy metabolism trigger the nutritional sensors to down-regulate mTOR pathway. These events not only benefit the general aging process but also maintain ovarian function and delay the reproductive decline. Considering the safety of the α-KG as a naturally occurring molecule in energy metabolism, its utility in reproduction of large mammals including humans deserves further investigation.

Effects of Phosphoethanolamine Supplementation on Mitochondrial Activity and Lipogenesis in a Caffeine Ingestion Caenorhabditis elegans Model

Caffeine intake is strongly linked to lipid metabolism. We previously reported the age-dependent physiological effects of caffeine intake in a Caenorhabditis elegans model. Since nutritional status can actively influence metabolism and overall health, in this study, we evaluated the effect of caffeine intake on lipid metabolism in adult-stage C. elegans. We found that, in C. elegans, fat storage and the level of phosphoethanolamine (PE) were significantly reduced with caffeine intake. In addition, mitochondrial activity decreased and mitochondrial morphology was disrupted, and the expression of oxidative stress response genes, hsp-6, gst-4, and daf-16, was induced by caffeine intake. Furthermore, the level of an energy metabolism sensor, phospho-AMP-activated protein kinase, was increased, whereas the expression of the sterol regulatory element binding protein gene and its target stearoyl-CoA desaturase genes, fat-5, -6, and -7, was decreased with caffeine intake. These findings suggest that caffeine intake causes mitochondrial dysfunction and reduces lipogenesis. Interestingly, these changes induced by caffeine intake were partially alleviated by PE supplementation, suggesting that the reduction in mitochondrial activity and lipogenesis is in part because of the low PE level, and proper dietary supplementation can improve organelle integrity.

Aqueous Bark Extract of Ceiba speciosa (A. St.-Hill) Ravenna Protects against Glucose Toxicity in Caenorhabditis elegans

Plants are widely used in folk medicine because of their pharmacological properties. Ceiba speciosa, popularly known as paineira-rosa or tree-of-wool, is a species found in the Northwest of Rio Grande do Sul, being native of the upper Uruguay River, Brazil. The tea obtained from the stem bark is employed in folk medicine to reduce cholesterol, triacylglycerides, and glucose levels. However, there are no studies in the literature proving its efficacy or the safety of its use. For this study, we used Caenorhabditis elegans as an animal model considering its advantages for risk assessment and pharmacological screenings. For the toxicological tests, C. elegans N2 (wild type) was treated with the aqueous extract of the stem bark of C. speciosa (ECE) at the first larval stage (L1) at concentrations of 5, 25, 50, and 250 μg/mL. To evaluate biological activities, we challenged the extract for oxidative stress resistance in the presence of paraquat (0.5 mM), H2O2 (1 mM), and against glucose-induced toxicity. Our results demonstrated that ECE did not alter survival rate, pharyngeal pumping, and reproduction of the nematodes. The extract was not able to protect the nematodes against the toxicity induced by prooxidants. Notably, ECE protected against glucotoxicity by increasing worms' life span and by reducing glucose levels. On the other hand, ECE treatment did not reduce lipid accumulation induced by exogenous glucose feeding, as observed in worms which lipid droplets were tagged with GFP. Based on our results, we believe that the extract is indeed promising for further studies focusing on carbohydrates metabolism; however, it needs to be carefully evaluated since the extract does not seem to modulate lipid accumulation.

Comparative genomic analysis of the human and nematode Caenorhabditis elegans uncovers potential reproductive genes and disease associations in humans

Reproduction is an important biological process. However, studies of human reproduction at the molecular level are limited due to the difficulty of performing in vivo studies. Hence, a mechanistic understanding of human reproduction remains still poor. Thus, it is important to use an alternative model organism for mechanistic studies of human reproduction. In this study, we used the nematode Caenorhabditis elegans as a model for studying human reproduction and identified 61 human and 535 worm reproductive genes through a combination of comparative genomic and Gene Ontology (GO) analyses. Interestingly, in terms of sex specificity, the number of male-specific genes was greater than the number of female-specific genes. Gene enrichment analysis identified biologically significant processes such as protein localization to cajal bodies/telomeres/nuclear bodies/chromosomes, helicase activity, pyrimidine biosynthesis, and determination of adult lifespan. Regarding the analysis of human reproductive diseases among the identified genes, 10 and 12 genes were identified in the human- and C. elegans-based analyses, respectively. In addition, RNA interference knockdown of a newly identified F52H2.6/DHCR24 gene increased brood size and ovulation/egg-laying rate in C. elegans. Therefore, gene identification, disease associations, and a proof-of-concept experiment using C. elegans will not only provide insights into mechanistic study of human reproduction, but also demonstrate the utility in studying human reproduction.

Krüppel-Like Factors in Metabolic Homeostasis and Cardiometabolic Disease

Members of the Krüppel-like factor (KLF) family of transcription factors, which are characterized by the presence of three conserved Cys₂/His₂ zinc-fingers in their C-terminal domains, control a wide variety of biological processes. In particular, recent studies have revealed that KLFs play diverse and essential roles in the control of metabolism at the cellular, tissue and systemic levels. In both liver and skeletal muscle, KLFs control glucose, lipid and amino acid metabolism so as to coordinate systemic metabolism in the steady state and in the face of metabolic stresses, such as fasting. The functions of KLFs within metabolic tissues are also important contributors to the responses to injury and inflammation within those tissues. KLFs also control the function of immune cells, such as macrophages, which are involved in the inflammatory processes underlying both cardiovascular and metabolic diseases. This review focuses mainly on the physiological and pathological functions of KLFs in the liver and skeletal muscle. The involvement of KLFs in inflammation in these tissues is also summarized. We then discuss the implications of KLFs' control of metabolism and inflammation in cardiometabolic diseases.

Role of Caenorhabditis elegans AKT-1/2 and SGK-1 in Manganese Toxicity

Excessive levels of the essential metal manganese (Mn) may cause a syndrome similar to Parkinson's disease. The model organism Caenorhabditis elegans mimics some of Mn effects in mammals, including dopaminergic neurodegeneration, oxidative stress, and increased levels of AKT. The evolutionarily conserved insulin/insulin-like growth factor-1 signaling pathway (IIS) modulates worm longevity, metabolism, and antioxidant responses by antagonizing the transcription factors DAF-16/FOXO and SKN-1/Nrf-2. AKT-1, AKT-2, and SGK-1 act upstream of these transcription factors. To study the role of these proteins in C. elegans response to Mn intoxication, wild-type N2 and loss-of-function mutants were exposed to Mn (2.5 to 100 mM) for 1 h at the L1 larval stage. Strains with loss-of-function in akt-1, akt-2, and sgk-1 had higher resistance to Mn compared to N2 in the survival test. All strains tested accumulated Mn similarly, as shown by ICP-MS. DAF-16 nuclear translocation was observed by fluorescence microscopy in WT and loss-of-function strains exposed to Mn. qRT-PCR data indicate increased expression of γ-glutamyl cysteine synthetase (GCS-1) antioxidant enzyme in akt-1 mutants. The expression of sod-3 (superoxide dismutase homologue) was increased in the akt-1 mutant worms, independent of Mn treatment. However, dopaminergic neurons degenerated even in the more resistant strains. Dopaminergic function was evaluated with the basal slowing response behavioral test and dopaminergic neuron integrity was evaluated using worms expressing green fluorescent protein (GFP) under the dopamine transporter (DAT-1) promoter. These results suggest that AKT-1/2 and SGK-1 play a role in C. elegans response to Mn intoxication. However, tissue-specific responses may occur in dopaminergic neurons, contributing to degeneration.

The African turquoise killifish: A research organism to study vertebrate aging and diapause

The African turquoise killifish has recently gained significant traction as a new research organism in the aging field. Our understanding of aging has strongly benefited from canonical research organisms—yeast, C. elegans, Drosophila, zebrafish, and mice. Many characteristics that are essential to understand aging—for example, the adaptive immune system or the hypothalamo‐pituitary axis—are only present in vertebrates (zebrafish and mice). However, zebrafish and mice live more than 3 years and their relatively long lifespans are not compatible with high‐throughput studies. Therefore, the turquoise killifish, a vertebrate with a naturally compressed lifespan of only 4–6 months, fills an essential gap to understand aging. With a recently developed genomic and genetic toolkit, the turquoise killifish not only provides practical advantages for lifespan and longitudinal experiments, but also allows more systematic characterizations of the interplay between genetics and environment during vertebrate aging. Interestingly, the turquoise killifish can also enter a long‐term dormant state during development called diapause. Killifish embryos in diapause already have some organs and tissues, and they can last in this state for years, exhibiting exceptional resistance to stress and to damages due to the passage of time. Understanding the diapause state could give new insights into strategies to prevent the damage caused by aging and to better preserve organs, tissues, and cells. Thus, the African turquoise killifish brings two interesting aspects to the aging field—a compressed lifespan and a long‐term resistant diapause state, both of which should spark new discoveries in the field.

An intestinal microRNA modulates the homeostatic adaptation to chronic oxidative stress in C. elegans

Adaptation to an environmental or metabolic perturbation is a feature of the evolutionary process. Recent insights into microRNA function suggest that microRNAs serve as key players in a robust adaptive response against stress in animals through their capacity to fine-tune gene expression. However, it remains largely unclear how a microRNA-modulated downstream mechanism contributes to the process of homeostatic adaptation. Here we show that loss of an intestinally expressed microRNA gene, mir-60, in the nematode C. elegans promotes an adaptive response to chronic - a mild and long-term - oxidative stress exposure. The pathway involved appears to be unique since the canonical stress-responsive factors, such as DAF-16/FOXO, are dispensable for mir-60 loss to enhance oxidative stress resistance. Gene expression profiles revealed that genes encoding lysosomal proteases and those involved in xenobiotic metabolism and pathogen defense responses are up-regulated by the loss of mir-60. Detailed genetic studies and computational microRNA target prediction suggest that endocytosis components and a bZip transcription factor gene zip-10, which functions in innate immune response, are directly modulated by miR-60 in the intestine. Our findings suggest that the mir-60 loss facilitates adaptive response against chronic oxidative stress by ensuring the maintenance of cellular homeostasis.

Fatty Acids Consumption: The Role Metabolic Aspects Involved in Obesity and Its Associated Disorders

Obesity and its associated disorders, such as insulin resistance, dyslipidemia, metabolic inflammation, dysbiosis, and non-alcoholic hepatic steatosis, are involved in several molecular and inflammatory mechanisms that alter the metabolism. Food habit changes, such as the quality of fatty acids in the diet, are proposed to treat and prevent these disorders. Some studies demonstrated that saturated fatty acids (SFA) are considered detrimental for treating these disorders. A high fat diet rich in palmitic acid, a SFA, is associated with lower insulin sensitivity and it may also increase atherosclerosis parameters. On the other hand, a high intake of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids may promote positive effects, especially on triglyceride levels and increased high-density lipoprotein (HDL) levels. Moreover, polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs) are effective at limiting the hepatic steatosis process through a series of biochemical events, such as reducing the markers of non-alcoholic hepatic steatosis, increasing the gene expression of lipid metabolism, decreasing lipogenic activity, and releasing adiponectin. This current review shows that the consumption of unsaturated fatty acids, MUFA, and PUFA, and especially EPA and DHA, which can be applied as food supplements, may promote effects on glucose and lipid metabolism, as well as on metabolic inflammation, gut microbiota, and hepatic metabolism.

Defective lipid metabolism associated with mutation in klf-2 and klf-3: important roles of essential dietary salts in fat storage

Background

Dietary salts are important factors in metabolic disorders. They are vital components of enzymes, vitamins, hormones, and signal transduction that act synergistically to regulate lipid metabolism. Our previous studies have identified that Krüppel-like factor −3 (KLF-3) is an essential regulator of lipid metabolism. However, it is not known if KLF-2 also regulates lipid metabolism and whether KLF-2 and −3 mediate the effects of dietary salts on lipid metabolism.

Methods

In this study, we used klf mutants [homozygous klf-2 (ok1043) V and klf-3 (ok1975) II mutants] to investigate the role of dietary salts in lipid metabolism. All gene expression was quantified by qRT-PCR. Localization of KLF-2 was analyzed by the expression of klf-2::gfp (in pPD95.75 vector) using a fluorescent microscope. Fat storage was measured by Oil Red O staining.

Results

Klf-2 was identified to express in the intestine during all stages of Caenorhabditis elegans development with peak expression at L3 stage. Mutation of klf-2 increased fat accumulation. Under regular growth media free of Ca^2+, the expression of both klf-2 and −3 was inhibited slightly; further their expression reduced significantly in WT worms fed on 10X Ca²⁺ diet. When klf-3 was mutated, the expression of klf-2 increased under 10X Ca²⁺ diet; but when klf-2 was mutated, the expression of klf-3 was not altered under 10X Ca²⁺ diet. Overall, Mg²⁺ and K⁺ were less effective on the gene expression of klfs. KLF target gene Ce-C/EBP-2 showed elevated expression in WT and klf-3 (ok1975) worms with changed Ca²⁺ concentrations but not in klf-2 (ok1043) worms. However, high Ca⁺² diet exhibited inhibitory effect on Ce-SREBP expression in WT worms.

Conclusion

Dietary Ca²⁺ is most effective on fat storage and klf-2 expression, wherein high Ca²⁺ diet decreased klf-2 expression and reduced fat buildup. Mechanistic study identified Ce-C/EBP (C48E7.3; lpd-2) and Ce-SREBP (Y47D3B.7; lpd-1) as the target genes of klf-2 and/or klf-3 to mediate lipid metabolism. This study identifies a new function of klf-2 in inhibiting fat buildup and reveals the interplay between dietary salts and klf-2 and klf-3 in lipid metabolism.

A genome-wide screen of bacterial mutants that enhance dauer formation in C. elegans

Molecular pathways involved in dauer formation, an alternate larval stage that allows Caenorhabditis elegans to survive adverse environmental conditions during development, also modulate longevity and metabolism. The decision to proceed with reproductive development or undergo diapause depends on food abundance, population density, and temperature. In recent years, the chemical identities of pheromone signals that modulate dauer entry have been characterized. However, signals derived from bacteria, the major source of nutrients for C. elegans, remain poorly characterized. To systematically identify bacterial components that influence dauer formation and aging in C. elegans, we utilized the individual gene deletion mutants in E. coli (K12). We identified 56 diverse E. coli deletion mutants that enhance dauer formation in an insulin-like receptor mutant (daf-2) background. We describe the mechanism of action of a bacterial mutant cyaA, that is defective in the production of cyclic AMP, which extends lifespan and enhances dauer formation through the modulation of TGF-β (daf-7) signaling in C. elegans. Our results demonstrate the importance of bacterial components in influencing developmental decisions and lifespan in C. elegans. Furthermore, we demonstrate that C. elegans is a useful model to study bacterial-host interactions.

Microfluidic Devices in Advanced Caenorhabditis elegans Research

The study of model organisms is very important in view of their potential for application to human therapeutic uses. One such model organism is the nematode worm, Caenorhabditis elegans. As a nematode, C. elegans have ~65% similarity with human disease genes and, therefore, studies on C. elegans can be translated to human, as well as, C. elegans can be used in the study of different types of parasitic worms that infect other living organisms. In the past decade, many efforts have been undertaken to establish interdisciplinary research collaborations between biologists, physicists and engineers in order to develop microfluidic devices to study the biology of C. elegans. Microfluidic devices with the power to manipulate and detect bio-samples, regents or biomolecules in micro-scale environments can well fulfill the requirement to handle worms under proper laboratory conditions, thereby significantly increasing research productivity and knowledge. The recent development of different kinds of microfluidic devices with ultra-high throughput platforms has enabled researchers to carry out worm population studies. Microfluidic devices primarily comprises of chambers, channels and valves, wherein worms can be cultured, immobilized, imaged, etc. Microfluidic devices have been adapted to study various worm behaviors, including that deepen our understanding of neuromuscular connectivity and functions. This review will provide a clear account of the vital involvement of microfluidic devices in worm biology.

Probiotic Strain Bifidobacterium animalis subsp. lactis CECT 8145 Reduces Fat Content and Modulates Lipid Metabolism and Antioxidant Response in Caenorhabditis elegans

Recently, microbial changes in the human gut have been proposed as a possible cause of obesity. Therefore, modulation of microbiota through probiotic supplements is of great interest to support obesity therapeutics. The present study examines the functional effect and metabolic targets of a bacterial strain, Bifidobacterium animalis subsp. lactis CECT 8145, selected from a screening in Caenorhabditis elegans. This strain significantly reduced total lipids (40.5% ± 2.4) and triglycerides (27.6% ± 0.5), exerting antioxidant effects in the nematode (30% ± 2.8 increase in survival vs control); activities were also preserved in a final food matrix (milk). Furthermore, transcriptomic and metabolomic analyses in nematodes fed with strain CECT 8145 revealed modulation of the energy and lipid metabolism, as well as the tryptophan metabolism (satiety), as the main metabolic targets of the probiotic. In conclusion, our study describes for the first time a new B. animalis subsp. lactis strain, CECT 8145, as a promising probiotic for obesity disorders. Furthermore, the data support future studies in obesity murine models.

Modeling type 2 diabetes-like hyperglycemia in C. elegans on a microdevice

Caenorhabditis elegans (C. elegans) has been widely used as a model organism for biomedical research due to its sufficient homology with mammals at the molecular and genomic levels. In this work, we describe a microfluidic assay to model type 2 diabetes-like hyperglycemia in C. elegans to examine several aspects of this disease on a microdevice. The microdevice is characterized by the integration of long-term worm culture, worm immobilization, and precise chemical stimuli in a single device, thus enabling the multi-parameter analysis of individual worms at a single-animal resolution. With this device, the lifespan, oxidative stress responses, and lipid metabolism of individual worms in response to different glucose concentrations were characterized. It was found that the mean lifespan of worms was significantly reduced by as much as 29.0% and 30.8% in worms that were subjected to 100 mM and 200 mM glucose, respectively. The expression of oxidative stress protein gst-4 was increased, and the expression of hsp-70 (heat shock protein) and skn-1 (redox sensitive transcription factor) genes was down-regulated in worms treated with a high level of glucose. Moreover, fat storage was markedly increased in the bodies of VS29 worms (vha-6p::GFP::dgat-2) that were exposed to the high-glucose condition. The established approach is not only suitable for further elucidation of the mechanism of metabolic disorders involved in diabetes and its complications, but also facilitates the evaluation of anti-diabetic drugs in a high-throughput manner.

Arsenic Exposure, Arsenic Metabolism, and Incident Diabetes in the Strong Heart Study

OBJECTIVE

Little is known about arsenic metabolism in diabetes development. We investigated the prospective associations of low-moderate arsenic exposure and arsenic metabolism with diabetes incidence in the Strong Heart Study.

RESEARCH DESIGN AND METHODS

A total of 1,694 diabetes-free participants aged 45-75 years were recruited in 1989-1991 and followed through 1998-1999. We used the proportions of urine inorganic arsenic (iAs), monomethylarsonate (MMA), and dimethylarsinate (DMA) over their sum (expressed as iAs%, MMA%, and DMA%) as the biomarkers of arsenic metabolism. Diabetes was defined as fasting glucose ≥ 126 mg/dL, 2-h glucose ≥ 200 mg/dL, self-reported diabetes history, or self-reported use of antidiabetic medications.

RESULTS

Over 11,263.2 person-years of follow-up, 396 participants developed diabetes. Using the leave-one-out approach to model the dynamics of arsenic metabolism, we found that lower MMA% was associated with higher diabetes incidence. The hazard ratios (95% CI) of diabetes incidence for a 5% increase in MMA% were 0.77 (0.63-0.93) and 0.82 (0.73-0.92) when iAs% and DMA%, respectively, were left out of the model. DMA% was associated with higher diabetes incidence only when MMA% decreased (left out of the model) but not when iAs% decreased. iAs% was also associated with higher diabetes incidence when MMA% decreased. The association between MMA% and diabetes incidence was similar by age, sex, study site, obesity, and urine iAs concentrations.

CONCLUSIONS

Arsenic metabolism, particularly lower MMA%, was prospectively associated with increased incidence of diabetes. Research is needed to evaluate whether arsenic metabolism is related to diabetes incidence per se or through its close connections with one-carbon metabolism.

Glucose induces sensitivity to oxygen deprivation and modulates insulin/IGF-1 signaling and lipid biosynthesis in Caenorhabditis elegans

Diet is a central environmental factor that contributes to the phenotype and physiology of individuals. At the root of many human health issues is the excess of calorie intake relative to calorie expenditure. For example, the increasing amount of dietary sugars in the human diet is contributing to the rise of obesity and type 2 diabetes. Individuals with obesity and type 2 diabetes have compromised oxygen delivery, and thus it is of interest to investigate the impact a high-sugar diet has on oxygen deprivation responses. By utilizing the Caenorhabditis elegans genetic model system, which is anoxia tolerant, we determined that a glucose-supplemented diet negatively impacts responses to anoxia and that the insulin-like signaling pathway, through fatty acid and ceramide synthesis, modulates anoxia survival. Additionally, a glucose-supplemented diet alters lipid localization and initiates a positive chemotaxis response. Use of RNA-sequencing analysis to compare gene expression responses in animals fed either a standard or glucose-supplemented diet revealed that glucose impacts the expression of genes involved with multiple cellular processes including lipid and carbohydrate metabolism, stress responses, cell division, and extracellular functions. Several of the genes we identified show homology to human genes that are differentially regulated in response to obesity or type 2 diabetes, suggesting that there may be conserved gene expression responses between C. elegans fed a glucose-supplemented diet and a diabetic and/or obesity state observed in humans. These findings support the utility of the C. elegans model for understanding the molecular mechanisms regulating dietary-induced metabolic diseases.

let-65 is cytoplasmic methionyl tRNA synthetase in C. elegans

Cytoplasmic methionyl tRNA synthetase (MetRS) is one of more than 20 cytoplasmic aminoacyl tRNA synthetase enzymes (ARS). This family of enzymes catalyzes a process fundamental for protein translation. Using a combination of genetic mapping, oligonucleotide array comparative genomic hybridization, and phenotypic correlation, we show that mutations in the essential gene, let-65, reside within the predicted Caenorhabditis elegans homologue of MetRS, which we have named mars-1. We demonstrate that the lethality associated with alleles of let-65 is fully rescued by a transgenic array that spans the mars-1 genomic region. Furthermore, sequence analysis reveals that six let-65 alleles lead to the alteration of highly conserved amino acids.

Genetic Dissection of the Physiological Role of Skeletal Muscle in Metabolic Syndrome

The primary deficiency underlying metabolic syndrome is insulin resistance, in which insulin-responsive peripheral tissues fail to maintain glucose homeostasis. Because skeletal muscle is the major site for insulin-induced glucose uptake, impairments in skeletal muscle’s insulin responsiveness play a major role in the development of insulin resistance and type 2 diabetes. For example, skeletal muscle of type 2 diabetes patients and their offspring exhibit reduced ratios of slow oxidative muscle. These observations suggest the possibility of applying muscle remodeling to recover insulin sensitivity in metabolic syndrome. Skeletal muscle is highly adaptive to external stimulations such as exercise; however, in practice it is often not practical or possible to enforce the necessary intensity to obtain measurable benefits to the metabolic syndrome patient population. Therefore, identifying molecular targets for inducing muscle remodeling would provide new approaches to treat metabolic syndrome. In this review, the physiological properties of skeletal muscle, genetic analysis of metabolic syndrome in human populations and model organisms, and genetically engineered mouse models will be discussed in regard to the prospect of applying skeletal muscle remodeling as possible therapy for metabolic syndrome.

Nematode Hsp90: highly conserved but functionally diverse

Nematodes are amongst the most successful and abundant organisms on the planet with approximately 30 000 species described, although the actual number of species is estimated to be one million or more. Despite sharing a relatively simple and invariant body plan, there is considerable diversity within the phylum. Nematodes have evolved to colonize most ecological niches, and can be free-living or can parasitize plants or animals to the detriment of the host organism. In this review we consider the role of heat shock protein 90 (Hsp90) in the nematode life cycle. We describe studies on Hsp90 in the free-living nematode Caenorhabditis elegans and comparative work on the parasitic species Brugia pahangi, and consider whether a dependence upon Hsp90 can be exploited for the control of parasitic species.

In vitro and in vivo models of non-alcoholic fatty liver disease (NAFLD)

By now, non-alcoholic fatty liver disease (NAFLD) is considered to be among the most common liver diseases world-wide. NAFLD encompasses a broad spectrum of pathological conditions ranging from simple steatosis to steatohepatitis, fibrosis and finally even cirrhosis; however, only a minority of patients progress to end-stages of the disease, and the course of the disease progression to the later stages seems to be slow, developing progressively over several years. Key risk factors including overweight, insulin resistance, a sedentary life-style and an altered dietary pattern, as well as genetic factors and disturbances of the intestinal barrier function have been identified in recent years. Despite intense research efforts that lead to the identification of these risk factors, knowledge about disease initiation and molecular mechanisms involved in progression is still limited. This review summarizes diet-induced and genetic animal models, as well as cell culture models commonly used in recent years to add to the understanding of the mechanisms involved in NAFLD, also referring to their advantages and disadvantages.