Biology subjects

Stark, R.

Publications and source records attributed to Stark, R..

At least 19 recordsLinked to original sources

bioRxiv2026

Unlocking the secrets of paired terminal genomic repeats utilised by the Burkholderia jumbo phage Matilda

Bacteriophages (phages) are viruses that infect bacteria. Jumbo phages have genomes exceeding 220 kb, which can support greater functional independence and complexity. This work identified vB_BceM_Matilda ({phi}Matilda), a novel Burkholderia-targeting jumbo phage. Before injecting its genome into the host bacterium, {phi}Matilda binds to the bacterial flagellum, the rotation of which is required to drive a productive phage infection. Its linear 267 kb dsDNA genome has a previously undescribed tripartite architecture, with bidirectional terminal elements of 1.3 kb and 25 kb, each flanked by distinct inverted repeats of 1.5 kb and 18 kb, respectively. These architectural elements bookend the genome. Transcriptomic and proteomic analyses tracked the phage infection process and confirmed that genes within these terminal elements are transcribed and translated during infection. The presence of bidirectional terminal sequences in related jumbo phages suggests that the tripartite genome architecture may be conserved and functionally important. This work represents the first description of this genome architecture in any organism, expanding our understanding of genome organisation and raising new questions about the replication, packaging, and evolution of jumbo phage genomes.

microbiology↗

bioRxiv2026

An unexpected specialization of the active zone scaffold RIM at high release synapses

The active zone scaffold RIM is canonically viewed as an obligate, universal pillar of the neurotransmitter release machinery. However, whether RIM is strictly required across diverse synapse subtypes with distinct release probabilities has remained an important unresolved question. Here, we report a fundamental revision of this model: RIM is not a constitutive necessity for baseline transmission, but rather a specialized "gain factor" selectively deployed to empower high-release synapses. Utilizing botulinum neurotoxin-based silencing to isolate convergent inputs at the Drosophila neuromuscular junction, we demonstrate that while RIM is essential for high-fidelity transmission at phasic (MN-Is) synapses, it is largely dispensable at low-release tonic (MN-Ib) synapses. This input specificity extends into plasticity: RIM is required for acute presynaptic homeostatic potentiation (PHP) at phasic inputs but is dispensable for the chronic maintenance of PHP at tonic inputs. Mechanistically, super-resolution imaging reveals that RIM is positioned significantly closer to CaV2 Ca2+ channel nanodomains at phasic synapses. During acute plasticity, RIM coordinates the homeostatic compaction of CaV2 channel clusters and drives the rapid expansion of the readily releasable vesicle pool. Our results revise the canonical view of active zone architecture, demonstrating that rather than serving as a static, uniform structural anchor, RIM functions as a tunable, dynamic module deployed to shape the performance and plasticity of high-demand synaptic connections.

neuroscience↗

bioRxiv2026

Acute threats modulate hunger circuit dynamics to instruct avoidance behaviour

During foraging animals must balance food-seeking with predator avoidance, yet how the brain integrates sensory information relating to food and threat remains unclear. Using in vivo calcium imaging in mice, we show that hunger-sensitive AgRP neurons in the hypothalamus are rapidly inhibited by threats across a threat imminence continuum, from a low environmental risk to a high physical restraint threat, independent of fasting state. This suppression is driven by GABAergic inputs from dorsomedial hypothalamus (DMH) neurons, which increase activity during threat exposure. While AgRP population activity shows uniform inhibition, pathway-specific monitoring using axonal GCaMP reveals distinct projection patterns. For example, AgRP terminals in BNST and LH decrease activity to both threat and food, while threats increased AgRP axonal activity in the PVN. Furthermore, location-specific optogenetic inhibition of AgRP neurons conditions spatial avoidance, mimicking a threat-induced defensive behavioural responses. These findings reveal a hypothalamic circuit where DMH GABA neurons suppress AgRP activity in response to external threats, prioritising avoidance over food-seeking to optimise adaptive behavioural responses during foraging.

neuroscience↗

bioRxiv2025

FiPhoPHA - A fiber photometry python package for post-hoc analysis

Fiber photometry is a neuroscience technique that can continuously monitor in vivo fluorescence to assess population neural activity or neuropeptide/transmitter release in freely behaving animals. Despite the widespread adoption of this technique, methods to statistically analyse data in an unbiased, objective, and easily adopted manner are lacking. Various pipelines for data analysis exist, but they are often system-specific, only for pre-processing data, and/or lack usability. Current post hoc statistical approaches involve inadvertently biased user-defined time-binned averages or area under the curve analysis. To date, no post-hoc user-friendly tool with few assumptions for a standardised unbiased analysis exists, yet such a tool would improve reproducibility and statistical reliability for all users. Hence, we have developed a user-friendly post hoc statistical analysis package in Python that is easily downloaded and applied to data from any fiber photometry system. This Fiber Photometry Post Hoc Analysis (FiPhoPHA) package incorporates a variety of tools, a downsampler, bootstrapped confidence intervals (CIs) for analyzing peri-event signals between groups and compared to baseline, and permutation tests for comparing peri-event signals across comparison periods. We also include the ability to quickly and efficiently sort the data into mean time bins, if desired. This provides an open-source, user-friendly python package for unbiased and standardised post-hoc statistical analysis to improve reproducibility using data from any fiber photometry system.

neuroscience↗

bioRxiv2024

A simple action reduces food intake and obesity in mice

Diets that are high in fat cause over-eating and weight gain in multiple species of animals, suggesting that high dietary fat is sufficient to cause obesity. However, high-fat diets are typically provided freely to animals in obesity experiments, so it remains unclear if high-fat diets would still cause obesity if they required more effort to obtain. We hypothesized that unrestricted and easy access is necessary for high-fat diet induced over-eating, and the corollary that requiring mice to perform small amounts of work to obtain high-fat diet would reduce high-fat diet intake and associated weight gain. To test this hypothesis, we developed a novel home-cage based feeding device that either provided high-fat diet freely, or after mice poked their noses into a port one time - a simple action that is easy for them to do. We tested the effect of this intervention for six weeks, with mice receiving all daily calories from high-fat diet, modifying only how they accessed it. Requiring mice to nose-poke to access high-fat diet reduced intake and nearly completely prevented the development of obesity. In follow up experiments, we observed a similar phenomenon in mice responding for low-fat grain-based pellets that do not induce obesity, suggesting a general mechanism whereby animals engage with and consume more food when it is freely available vs. when it requires a simple action to obtain. We conclude that unrestricted access to food promotes overeating, and that a simple action such as a nose-poke can reduce over-eating and weight gain in mice. This may have implications for why over-eating and obesity are common in modern food environments, which are often characterized by easy access to low-cost unhealthy foods.

animal behavior and cognition↗

bioRxiv2024

EnteroBase in 2025: exploring the genomic epidemiology of bacterial pathogens

This paper presents an update on the content, accessibility and analytical tools of the EnteroBase platform for web-based pathogen genome analysis. EnteroBase provides manually curated databases of genome sequence data and associated metadata from currently >1.1 million bacterial isolates, more recently including Streptococcus spp. and Mycobacterium tuberculosis. We have implemented the genome-based detection of antimicrobial resistance determinants and the new bubble plot graphical tool for visualising bacterial genomic population structures, based on pre-computed hierarchical clusters. Access to data and analysis tools is provided through an enhanced graphical user interface and a new application programming interface (RESTful API). EnteroBase is now being developed and operated by an international consortium, to accelerate the development of the platform and ensure the longevity of the resources built. EnteroBase can be accessed at https://enterobase.warwick.ac.uk as well as https://enterobase.dsmz.de. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/608032v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@88ff78org.highwire.dtl.DTLVardef@3c426eorg.highwire.dtl.DTLVardef@2d8481org.highwire.dtl.DTLVardef@5644bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2023

Ghrelin signalling in AgRP neurons links metabolic state to the sensory regulation of AgRP neural activity.

ObjectiveThe sensory detection of food and food cues suppresses Agouti related peptide (AgRP) neuronal activity prior to consumption with greatest suppression in response to high caloric food or energy need. Although external sensory cues regulate AgRP neuronal activity, the interoceptive mechanisms priming an appropriate AgRP neural response to sensory information of caloric availability remain unexplored. Since hunger increases plasma ghrelin, we hypothesized that ghrelin receptor (GHSR) signalling on AgRP neurons is a key interoceptive mechanism integrating energy need with external sensory cues predicting caloric availability. MethodsWe used in vivo photometry to measure the effects of ghrelin administration or fasting on AgRP neural activity with GCaMP6s and dopamine release in the nucleus accumbens with GRAB-DA in mice lacking ghrelin receptors in AgRP neurons. ResultsThe deletion of GHSR on AgRP neurons prevented ghrelin-induced food intake, motivation and AgRP activity. The presentation of food (peanut butter pellet) or a wooden dowel suppressed AgRP activity in fasted WT but not mice lacking GHSRs in AgRP neurons. Similarly, peanut butter and a wooden dowel increased dopamine release in the nucleus accumbens after ip ghrelin injection in WT but not mice lacking GHSRs in AgRP neurons. No difference in dopamine release was observed in fasted mice. Finally, ip ghrelin administration did not directly increase dopamine neural activity in the ventral tegmental area. ConclusionsOur results suggest that AgRP GHSRs integrate an interoceptive state of energy need with external sensory information to produce an optimal change in AgRP neural activity. Thus, ghrelin signalling on AgRP neurons is more than just a feedback signal to increase AgRP activity during hunger.

neuroscience↗

bioRxiv2023

Temporal regulation of AgRP neurons mediates context-induced feeding

An environment can have a powerful influence over appetite and feeding behaviour. For example, an environmental context, which reliably predicts food, will increase the appetitive food drive to the same environment context. Interestingly, mice are required to be hungry to develop such a context-induced feeding (CIF) response, suggesting the neural circuits sensitive to hunger play an important role to associate an internal energy state with a particular environment context. Hunger-sensing Agouti related peptide (AgRP) neurons are activated by circulating signals of energy deficit and reset to a silenced state by gut feedback mechanisms following food consumption. We hypothesised that AgRP neurons are both necessary and sufficient to drive CIF in the absence of hunger. While fasting increased CIF, chemogenetic inhibition of AgRP neurons during context acquisition prevented this effect. Intriguingly, chemogenetic activation of AgRP neurons during context acquisition did not increase CIF, suggesting precise temporal firing properties may be required. Indeed, photostimulation of AgRP neurons, only during context exposure (ON-OFF in context), increased CIF. Moreover, AgRP photostimulation prior to context exposure, coupled with the termination of photostimulation in the context in the absence of food consumption, was sufficient to drive a subsequent CIF. Our results suggest that AgRP neurons regulate the acquisition of CIF when the temporal firing properties are matched to context exposure. These results further highlight that acute AgRP inhibition is a salient neural event underscoring the effect of hunger on associative learning.

neuroscience↗

bioRxiv2023

Dual RNA-seq identifies proteins and pathways modulated during Clostridioides difficile colonisation

The gastrointestinal pathogen, Clostridioides difficile, is the most common cause of hospital-acquired diarrhoea. Bacterial interactions with the gut mucosa are crucial for colonisation and establishment of C. difficile infection, however, key infection events like bacterial attachment and gut penetration are still poorly defined. To better understand the initial events that occur when this anaerobic pathogen interacts with human gut epithelial cells, we employed a dual RNA-sequencing approach to study the bacterial and host transcriptomic profiles during C. difficile infection in a dual-environment in vitro human gut model. Temporal changes in gene expression during infection were studied in the bacterium and the host cells over the course of 3-24 hours. While there were several common differentially expressed bacterial genes across the different times after infection, mammalian transcriptional profiles were quite distinct with little overlap. Interestingly, an induction of colonic receptors for C. difficile toxins was observed, along with the expression downregulation of genes encoding immune response markers. Several cell wall associated proteins were downregulated in C. difficile when in association with host cells, including slpA, which encodes the main S-layer protein. Gene function and pathway enrichment analyses revealed a potential modulation of the purine/pyrimidine synthesis pathways both in the mammalian and the bacterial cells. We observed that proline-proline endopeptidase, a secreted metalloprotease responsible for cell surface protein cleavage, is downregulated during infection, and a mutant lacking this enzyme demonstrated enhanced adhesion to epithelial cells during infection. This study provides new insight into the host and bacterial pathways based on gene expression modulation during the initial contact of C. difficile with gut cells. ImportanceThe initial interactions between the colonic epithelium and the bacterium are likely critical in the establishment of Clostridioides difficile infection, one of the major causes of hospital acquired diarrhoea worldwide. Molecular interactions between C. difficile and human gut cells have not been well defined mainly due to the technical challenges of studying cellular host-pathogen interactions with this anaerobe. Here we have examined transcriptional changes occurring in the pathogen and host cells during the initial 24 hours of infection. Our data indicate several changes in metabolic pathways and virulence-associated factors during the initial bacterium-host cell contact and early stages of infection. We describe canonical pathways enriched based on the expression profiles of a dual RNAseq in the host and the bacterium, and functions of bacterial factors modulated during infection. This study provides insight into the early infection process at a molecular level.

microbiology↗

bioRxiv2023

Hunger signalling in the olfactory bulb primes exploration, food-seeking and peripheral metabolism.

Growing evidence highlights a complex interaction between olfaction and metabolism with impaired olfactory function observed in obesity and increased olfactory sensitivity during hunger. The mechanisms linking metabolic state and olfaction remain unknown, but increased accessibility of hormones, such as ghrelin, and the diverse expression of hormone receptors such as those for ghrelin (GHSRs) in the olfactory system suggests an underappreciated neuroendocrine role. Here, we examined the hypothesis that GHSRs in the olfactory bulb (OB) link hunger with olfactory sensitivity to influence foraging behaviours and metabolism. Selective deletion of OBGHSRs in adult male mice was achieved with adeno-associated viral expression of cre-recombinase in the OB of floxed-Ghsr mice. OBGHSR deletion significantly affected olfactory discrimination and habituation to both food and pheromone odours, with greatest effect under fasted conditions. Anxiety-like and depression-like behaviour was significantly greater after OBGHSR deletion using 3 independent anxiety behavioural tasks and testing for anhedonia, whereas exploratory behaviour was reduced. No effect on spatial navigation and memory was observed. Although OBGHSR deletion did not affect cumulative food intake, it significantly impacted feeding behaviour as evidenced by altered bout number and duration. Moreover, food-finding after fasting or ip ghrelin was attenuated. Intriguingly, OBGHSR deletion caused an increase in body weight and fat mass, spared fat utilisation on a chow diet and impaired glucose metabolism indicating metabolic dysfunction. We conclude that OBGHSRs maintain olfactory sensitivity, particularly during hunger, and facilitate behavioural adaptations that optimise food-seeking in anxiogenic environments, priming metabolic pathways in preparation for food consumption.

neuroscience↗

bioRxiv2021

Identification of a stress-sensitive anorexigenic neurocircuit from medial prefrontal cortex to lateral hypothalamus in humans and mice

By modeling neural network dynamics related to homeostatic state and BMI, we identified a novel pathway projecting from the medial prefrontal cortex (mPFC) to the lateral hypothalamus (LH) in humans. We then assessed the physiological role and dissected the function of this mPFC-LH circuit in mice. In vivo recordings of population calcium activity revealed that this glutamatergic mPFC-LH pathway is activated in response to acute stressors and inhibited during food consumption, suggesting a role in stress-related control over food intake. Consistent with this role, inhibition of this circuit increased feeding and sucrose seeking during mild stressors, but not under non-stressful conditions. Finally, chemogenetic or optogenetic activation of the mPFC-LH pathway is sufficient to suppress food intake and sucrose-seeking in mice. These studies identify a glutamatergic mPFC-LH as a novel stress-sensitive anorexigenic neural pathway involved in the cortical control of food intake.

neuroscience↗

bioRxiv2021

Meta-exoproteomics identifies active plant-microbe interactions operating in the rhizosphere

The advance of DNA sequencing technologies has drastically changed our perception of the complexity and structure of the plant microbiome and its role in augmenting plant health. By comparison, our ability to accurately identify the metabolically active fraction of soil microbiota and their specific functional role is relatively limited. Here, we combined our recently developed protein extraction method and an iterative bioinformatics pipeline to enable the capture and identification of extracellular proteins (meta-exoproteomics) expressed in the rhizosphere of Brassica spp. First, we validated our method in the laboratory by successfully identifying proteins related to the host plant (Brassica rapa) and a bacterial inoculant, Pseudomonas putida BIRD-1, revealing the latter expressed numerous rhizosphere specific proteins linked to the acquisition of plant-derived nutrients. Next, we analysed natural field-soil microbial communities associated with Brassica napus L (Oil Seed rape). By combining deep-sequencing metagenomics with meta-exoproteomics, a total of 1882 proteins were identified in bulk and rhizosphere samples. Importantly, meta-exoproteomics identified a clear shift (p<0.001) in the metabolically active fraction of the soil microbiota responding to the presence of B. napus roots that was not apparent in the composition of the total microbial community (metagenome). This metabolic shift was associated with the stimulation of rhizosphere-specialised bacteria, such as Gammaproteobacteria, Betaproteobacteria and Flavobacteriia and the upregulation of plant beneficial functions related to phosphorus and nitrogen mineralisation. By providing the first meta-proteomic level assessment of the active plant microbiome at the field-scale, this study demonstrates the importance of moving past a genomic assessment of the plant microbiome in order to determine ecologically important plant: microbe interactions driving plant growth.

microbiology↗

bioRxiv2021

Impact of sulfamethoxazole on a riverine microbiome

The continued emergence of bacterial pathogens presenting antimicrobial resistance is widely recognised as a global health threat and recent attention focused on potential environmental reservoirs of antibiotic resistance genes (ARGs). Freshwater environments such as rivers represent a potential hotspot for ARGs and antibiotic resistant bacteria as they are receiving systems for effluent discharges from wastewater treatment plants (WWTPs). Effluent also contains low levels of different antimicrobials including antibiotics and biocides. Sulfonamides are antibacterial chemicals widely used in clinical, veterinary and agricultural settings and are frequently detected in sewage sludge and manure in addition to riverine ecosystems. The impact of such exposure on ARG prevalence and diversity is unknown, so the aim of this study was to investigate the release of a sub-lethal concentration of the sulfonamide compound sulfamethoxazole (SMX) on the river bacterial microbiome using a flume system. This system was a semi-natural in vitro flume using river water (30 L) and sediment with circulation to mimic river flow. A combination of omics approaches were conducted to study the impact of SMX exposure on the microbiomes within the flumes. Metagenomic analysis showed that the addition of low concentrations of SMX (<4 g L-1) had a limited effect on the bacterial resistome in the water fraction only, with no impact observed in the sediment. Metaproteomics did not show differences in ARGs expression with SMX exposure in water. Overall, the river bacterial community was resilient to short term exposure to sub-lethal concentrations of SMX which mimics the exposure such communities experience downstream of WWTPs throughout the year.

microbiology↗

bioRxiv2021

Glucose-sensing in AgRP neurons integrates homeostatic energy state with dopamine signalling in the striatum.

Hunger increases the motivation of an organism to seek out and consume highly palatable energy dense foods. While hunger-sensing Agouti-related peptide (AgRP) neurons influence this process, whether metabolic detection of homeostatic state via metabolic sensing in AgRP neurons potentiates motivation through the midbrain dopamine system is unexplored. Here, we used the AgRP-specific deletion of carnitine acetyltransferase (Crat), a metabolic enzyme regulating glucose and fatty acid oxidation, as a model of impaired metabolic-sensing in AgRP neurons. We then tested the hypothesis that appropriate metabolic-sensing in AgRP neurons is required to increase food reward motivation by modulating accumbal or striatal dopamine release. Electrophysiological studies confirm that Crat deletion in AgRP neurons (KO) impairs normal ex vivo glucose-sensing, and in vivo photometry experiments show that AgRP neurons in KO mice do not exhibit normal responses to repeated palatable food presentation and consumption, highlighting that this model is appropriate to test the hypothesis. Fiber photometry experiments, using the dopamine sensor GRAB-DA, revealed that impaired metabolic-sensing reduces acute dopamine release (seconds) in the nucleus accumbens, but not the dorsal striatum, to palatable food consumption and during operant responding. Positron electron tomography (PET) methods indicated that impaired metabolic-sensing in AgRP neurons suppressed radiolabelled 18F-fDOPA accumulation after [~]30 minutes in the dorsal striatum but not the ventral striatum, suggesting a role for AgRP neurons to restrict a long term post-ingestive dopamine response in the dorsal striatum. Finally, impaired metabolic-sensing in AgRP neurons suppresses motivated operant responding for sucrose rewards. Notably, these behavioural effects are potentiated in the hungry state and therefore highlight that metabolic-sensing in AgRP neurons is required for the appropriate temporal integration and transmission of homeostatic hunger-sensing to dopamine signalling in the striatum.

neuroscience↗

bioRxiv2020

Feeding Experimentation Device version 3 (FED3): An open-source home-cage compatible device for measuring food intake and operant behavior

Feeding is critical for survival and disruption in the mechanisms that govern food intake underlie disorders such as obesity and anorexia nervosa. It is important to understand both food intake and food motivation to reveal mechanisms underlying feeding disorders. Operant behavioral testing can be used to measure the motivational component to feeding, but most food intake monitoring systems do not measure operant behavior. Here, we present a new solution for monitoring both food intake and motivation: The Feeding Experimentation Device version 3 (FED3). FED3 measures food intake and operant behavior in rodent home-cages, enabling longitudinal studies of feeding behavior with minimal experimenter intervention. It has a programmable output for synchronizing behavior with optogenetic stimulation or neural recordings. Finally, FED3 design files are open-source and freely available, allowing researchers to modify FED3 to suit their needs. In this paper we demonstrate the utility of FED3 in a range of experimental paradigms. In BriefUsing a novel, high-throughput home cage feeding platform, FED3, Matikainen-Ankney et al. quantify food intake and operant learning in groups of mice conducted at multiple institutions across the globe. Results include rates of operant efficiency, circadian feeding patterns, and operant optogenetic self-stimulation. Highlights O_LIThe Feeding Experimentation Device version 3(FED3) records food intake and operant behavior in rodent home cages. C_LIO_LIAnalysis of food intake includes total intake, meal pattern analysis, and circadian analysis of feeding patterns. C_LIO_LIFED3 also allows for operant behavioral assays to examine food learning and motivation. C_LI

animal behavior and cognition↗

bioRxiv2020

The Brain Activation-based Sexual Image Classifier (BASIC): A sensitive and specific fMRI activity pattern for sexual image perception

Sexual stimuli processing is a key element in the repertoire of human affective and motivational states. Previous neuroimaging studies of sexual stimulus processing have revealed a complicated mosaic of activated regions, leaving unresolved questions about their sensitivity and specificity to sexual stimuli per se, generalizability across individuals, and potential utility as neuromarkers for sexual stimulus processing. In this study, data on sexual, negative, non-sexual positive, and neutral images from Wehrum et al. (2013) (N = 100) were re-analyzed with multivariate Support Vector Machine models to create the Brain Activation-based Sexual Image Classifier (BASIC) model. This model was tested for sensitivity, specificity, and generalizability in cross-validation (N = 100) and an independent test cohort (N = 18; Kragel et al. 2019). The BASIC model showed highly accurate performance (94-100%) in classifying sexual versus neutral or nonsexual affective images in both datasets. Virtual lesions and test of individual large-scale networks (e.g., visual or attention networks) show that these individual networks are neither necessary nor sufficient to capture sexual stimulus processing. These findings suggest that brain responses to sexual stimuli constitute a category of mental event that is distinct from general affect and involves multiple brain networks. It is, however, largely conserved across individuals, permitting the development of neuromarkers for sexual processing in individual persons. Future studies could assess performance of BASIC to a broader array of affective/motivational stimuli and link brain responses with physiological and subjective measures of sexual arousal.

neuroscience↗

bioRxiv2020

Pharmacologic activation of the mitochondrial phosphoenolpyruvate cycleenhances islet function in vivo

The mitochondrial GTP (mtGTP)-dependent phosphoenolpyruvate (PEP) cycle is an anaplerotic-cataplerotic mitochondrial shuttle utilizing mitochondrial PEPCK (PCK2) and pyruvate kinase (PK). PEP cycling stimulates insulin secretion via OxPhos-independent lowering of ADP by PK. We assess in vivo whether islet PCK2 is necessary for glucose sensing and if speeding the PEP cycle via pharmacological PK activators amplifies insulin secretion. Pck2-/- mice had severely impaired insulin secretion during islet perifusion, oral glucose tolerance tests and hyperglycemic clamps. Acute and chronic pharmacologic PK activator therapy improved islet insulin secretion from normal, high-fat diet (HFD) fed, or Zucker diabetic fatty (ZDF) rats, and glucolipotoxic or diabetic humans. A similar improvement in insulin secretion was observed in regular chow and HFD rats in vivo. Insulin secretion and cytosolic Ca2+ during PK activation were dependent on PCK2. These data provide a preclinical rationale for strategies, such as PK activation, that target the PEP cycle to improve glucose homeostasis. HighlightsO_LILoss of mitochondrial phosphoenolpyruvate (PEP) impairs insulin release in vivo. C_LIO_LIPyruvate kinase (PK) activators stimulate beta-cells in preclinical diabetes models. C_LIO_LIPEP cycling in vivo depends on PK and mitochondrial PEPCK (PCK2) for insulin release. C_LIO_LIAcute and 3-week oral PK activator amplifies insulin release during hyperglycemia. C_LI eTOC BlurbAbudukadier et al. show that small molecule pyruvate kinase activation in vivo and in vitro increases insulin secretion in rodent and human models of diabetes. The phosphoenolpyruvate (PEP) cycling mechanism and its amplification are dependent on mitochondrial PEPCK (PCK2).

physiology↗

bioRxiv2019

Independence of HIF1a and androgen signaling pathways in prostate cancer

Androgen signaling drives prostate cancer progression and is a therapeutic target. Hypoxia/HIF1a signaling is associated with resistance to hormone therapy and a poor prognosis in patients treated with surgery or radiotherapy. It is not known whether the pathways operate in cooperation or independently. Using LNCaP cells with and without stable transfection of a HIF1a expression vector, we show that combined AR and HIF1a signaling promotes tumor growth in vitro and in vivo, and the capacity of HIF1a to promote tumor growth in the absence of endogenous androgen in vivo. Gene expression analysis identified 7 genes that were upregulated by both androgen and HIF1a. ChIP-Seq analysis showed that the AR and HIF/hypoxia signaling pathways function independently regulating the transcription of different genes with few shared targets. In clinical datasets elevated expression of 5 of the 7 genes was associated with a poor prognosis. Our findings suggest that simultaneous therapeutic inhibition of AR and HIF1a signaling pathways should be explored as a potential therapeutic strategy.

cancer biology↗