Biology subjects

Sweeney, P.

Publications and source records attributed to Sweeney, P..

9 recordsLinked to original sources

bioRxiv2026

Mesolimbic dopamine signaling mediates increased hedonic feeding and food seeking in lactating mice

Lactation dramatically increases energy intake to support milk production and care for the offspring. However, the behavioral and neural circuit mechanisms driving heightened feeding during lactation remain unclear. Here, we reveal that lactation increases food-seeking behavior and enhances palatable food intake in mice. Fiber photometry recordings demonstrate increased dopamine release in the nucleus accumbens in lactating animals during feeding tasks. This elevated dopamine signaling is ultimately required for promoting both food seeking and palatable food intake during lactation as pharmacological inhibition of dopamine receptors or chemogenetic inhibition of VTA dopamine neurons both reduce food seeking and palatable food intake in lactating mice to non-lactating levels. Further, selective inhibition of dopamine receptors in the nucleus accumbens produces similar results. Together, these findings provide a circuit basis mediating elevated food seeking and palatable food intake during lactation, providing novel insights into the regulation of maternal energy balance and feeding behavior. HighlightsLactation increases food seeking and hedonic feeding in mice Mesolimbic dopamine levels are enhanced during feeding in lactating mice VTA dopamine neurons mediate increased palatable food intake and food seeking during lactation VTA-NAc dopamine transmission mediates increased food seeking and palatable food intake during lactation

neuroscience↗

bioRxiv2025

Elevated activity of the mesolimbic dopamine system promotes feeding during pregnancy in mice

The pregnancy period is accompanied by increased feeding behavior to accommodate the elevated energy demands associated with fetal growth and development. However, the underlying neural circuitry and molecular mechanisms mediating increased feeding during pregnancy are largely unknown. Here, we utilize a combination of fiber photometry, chemogenetics, and mouse behavioral assays to characterize altered feeding behavior during pregnancy in mice. We uncover that pregnancy increases the activity of the mesolimbic dopamine system during both homeostatic and hedonic feeding behavior in mice. VTA dopamine neurons are ultimately required for promoting increased hedonic feeding during pregnancy as inhibition of these cells selectively reduces acute high fat diet intake in pregnant mice. Further, pregnant mice exhibit increased sensitivity to food deprivation, an effect which requires activity of the mesolimbic dopamine system. Together, these findings provide a circuit basis mediating altered hedonic feeding behavior and sensitivity to negative energy balance during pregnancy in mice. HighlightsO_LIVTA dopamine neurons show enhanced responsivity to palatable food during pregnancy C_LIO_LIVTA dopamine neurons show enhanced responsivity to negative energy balance during pregnancy C_LIO_LINucleus accumbens dopamine is increased during homeostatic and hedonic feeding in pregnant mice C_LIO_LIVTA dopamine neuron activity regulates hedonic eating and fast-induced refeeding in pregnant mice C_LI

neuroscience↗

bioRxiv2025

Reduced melanocortin tone mediates increased feeding during pregnancy in mice

During pregnancy mammals increase their food intake to accommodate the elevated metabolic demands associated with fetal growth and development. However, the molecular and neural circuit mechanisms mediating increased feeding during pregnancy are largely unknown. Here, we demonstrate that arcuate nucleus agouti-related peptide (AgRP) neurons are activated and pro-opiomelanocortin (POMC) neurons are inhibited during pregnancy in mice. These changes are required for promoting hyperphagia during pregnancy as chemogenetic inhibition of AgRP neurons or activation of POMC neurons both reduced the feeding of pregnant mice to non-pregnant levels. Finally, we utilized single cell resolution spatial transcriptomics in the arcuate nucleus of non-pregnant and pregnant mice to characterize pregnancy-induced changes in the transcriptomic state of arcuate nucleus neurons, including significant changes in both AgRP and POMC neurons. Together, these findings outline a circuit mechanism mediating increased feeding during pregnancy, providing important mechanistic insights related to conditions at the intersection of reproduction and metabolism. HighlightsO_LIAgRP neuron activity is increased and POMC neuron activity is decreased in pregnant mice C_LIO_LIIncreased AgRP neuron activity and reduced POMC neuron activity is required for increased feeding during pregnancy C_LIO_LIPregnancy enhances responsivity of AgRP neurons to palatable food C_LIO_LIPregnancy drastically alters the transcriptional state of both AgRP and POMC neurons towards positive energy balance C_LI

neuroscience↗

bioRxiv2024

Neuroanatomical dissection of the MC3R circuitry regulating energy rheostasis

Although mammals resist both acute weight loss and weight gain, the neural circuitry mediating bi-directional defense against weight change is incompletely understood. Global constitutive deletion of the melanocortin-3-receptor (MC3R) impairs the behavioral response to both anorexic and orexigenic stimuli, with MC3R knockout mice demonstrating increased weight gain following anabolic challenges and increased weight loss following anorexic challenges (i.e. impaired energy rheostasis). However, the brain regions mediating this phenotype remain incompletely understood. Here, we utilized MC3R floxed mice and viral injections of Cre-recombinase to selectively delete MC3R from medial hypothalamus (MH) in adult mice. Behavioral assays were performed on these animals to test the role of MC3R in MH in the acute response to orexigenic and anorexic challenges. Complementary chemogenetic approaches were used in MC3R-Cre mice to localize and characterize the specific medial hypothalamic brain regions mediating the role of MC3R in energy homeostasis. Finally, we performed RNAscope in situ hybridization to map changes in the mRNA expression of MC3R, POMC, and AgRP following energy rheostatic challenges. Our results demonstrate that MC3R deletion in MH increased feeding and weight gain following acute high fat diet feeding in males, and enhanced the anorexic effects of semaglutide, in a sexually dimorphic manner. Additionally, activation of DMH MC3R neurons increased energy expenditure and locomotion. Together, these results demonstrate that MC3R mediated effects on energy rheostasis result from the loss of MC3R signaling in the medial hypothalamus of adult animals and suggest an important role for DMH MC3R signaling in energy rheostasis. Key Points: O_LIMC3R signaling regulates energy rheostasis in adult mice C_LIO_LIMedial hypothalamus regulates energy rheostasis in adult mice C_LIO_LIEnergy rheostasis alters mRNA levels of AgRP and MC3R in DMH C_LIO_LIDMH MC3R neurons increase locomotion and energy expenditure C_LIO_LIMC3R expression in DMH is sexually dimorphic C_LI

neuroscience↗

bioRxiv2023

Physics-informed deep generative learning for quantitative assessment of the retina

Disruption of retinal vasculature is linked to various diseases, including diabetic retinopathy and macular degeneration, leading to vision loss. We present here a novel algorithmic approach that generates highly realistic digital models of human retinal blood vessels based on established biophysical principles, including fully-connected arterial and venous trees with a single inlet and outlet. This approach, using physics-informed generative adversarial networks (PI-GAN), enables the segmentation and reconstruction of blood vessel networks that requires no human input and out-performs human labelling. Our findings highlight the potential of PI-GAN for accurate retinal vasculature characterization, with implications for improving early disease detection, monitoring disease progression, and improving patient care.

biophysics↗

bioRxiv2023

Cell autonomous regulation of the activation of AgRP neurons by the melanocortin-3 receptor

The melanocortin-3 receptor (MC3R) is a negative regulator of the central melanocortin circuitry via presynaptic expression on AgRP nerve terminals, from where it regulates GABA release onto secondary MC4R-expressing neurons. Hence, animals lacking MC3R (MC3R KO) exhibit hypersensitivity to MC4R agonists. However, MC3R KO mice also exhibit defective behavioral and neuroendocrine responses to fasting. Here, we demonstrate that MC3R KO mice exhibit defective activation of AgRP neurons in response to fasting and cold exposure, while exhibiting normal inhibition of AgRP neurons by sensory detection of food. Further, using an AgRP-specific MC3R knockout model, we show that the control of AgRP neuron activation by MC3R is cell-autonomous. One mechanism underlying this involves the response to ghrelin, which is also blunted in mice with AgRP-specific deletion of the MC3R. Thus, MC3R is a crucial player in the control of energy homeostasis by the central melanocortin system, not only acting presynaptically on AgRP neurons, but via AgRP cell-autonomous regulation of fasting- and cold-induced neuronal activation as well.

neuroscience↗

bioRxiv2021

Structure, dynamics, and inhibition of Staphylococcus aureus m1A22-tRNA methyltransferase

The enzyme m1A22-tRNA methyltransferase (TrmK) catalyses the transfer of a methyl group from SAM to the N1 of adenine 22 in tRNAs. TrmK is essential for Staphylococcus aureus survival during infection, but has no homologue in mammals, making it a promising target for antibiotic development. Here we describe the structural and functional characterisation of S. aureus TrmK. Crystal structures are reported for S. aureus TrmK apoenzyme and in complexes with SAM and SAH. Isothermal titration calorimetry showed that SAM binds to the enzyme with favourable but modest enthalpic and entropic contributions, whereas SAH binding leads to an entropic penalty compensated by a large favourable enthalpic contribution. Molecular dynamics simulations point to specific motions of the C-terminal domain being altered by SAM binding, which might have implications for tRNA recruitment. Activity assays for S. aureus TrmK-catalysed methylation of WT and position 22 mutants of tRNALeu demonstrate that the enzyme requires an adenine at position 22 of the tRNA. Intriguingly, a small RNA hairpin of 18 nucleotides is methylated by TrmK depending on the position of the adenine. In-silico screening of compounds suggested plumbagin as a potential inhibitor of TrmK, which was confirmed by activity measurements. Furthermore, LC-MS indicated the protein was covalently modified by one equivalent of the inhibitor, and proteolytic digestion coupled with LC-MS identified Cys92, in the vicinity of the SAM-binding site, as the sole residue modified. These results these results identify a cryptic binding pocket of S. aureus TrmK and lay the foundation for future structure-based drug discovery.

biochemistry↗

bioRxiv2017

Combining optical imaging of cleared tissue with mathematical modelling to predict drug delivery and therapeutic response

Understanding how drugs are delivered to diseased tissue, and their subsequent spatial and temporal distribution, is a key factor in the development of effective, targeted therapies. However, the interaction between the pathophysiology of diseased tissue and individual therapeutic agents can be complex, and can vary significantly between individuals. In cancer, suboptimal dosing resulting from poor delivery can cause reduced treatment efficacy, upregulation of resistance mechanisms and can even stimulate growth. Preclinical tools to better understand drug delivery are therefore urgently required, which incorporate the inherent variability and heterogeneity of human disease. To meet this need, we have combined multiscale mathematical modelling, high-resolution optical imaging of intact, optically-cleared tumour tissue from animal models, and in vivo magnetic resonance imaging (MRI). Our framework, named REANIMATE (REAlistic Numerical Image-based Modelling of biologicAl Tissue substratEs) allows large tissue samples to be investigated as if it were a living sample, in detailed, highly controlled, computational experiments. Specifically, we show that REANIMATE can be used to predict the heterogeneous delivery of specific therapeutic agents, in disparate two murine xenograft models of human colorectal carcinoma. Given the wide adoption of optical clearing equipment in biomedical research laboratories, REANIMATE enables a new paradigm in cancer drug development, which could also be applied to other disease areas.

biophysics↗

bioRxiv2017

Insights into cerebral haemodynamics and oxygenation utilising in vivo mural cell imaging and mathematical modelling

The neurovascular mechanisms underpinning the local regulation of cerebral blood flow (CBF) and oxygen transport remain elusive. In this study we have combined novel in vivo imaging of cortical microvascular and mural cell architecture with mathematical modelling of blood flow and oxygen transport, to provide new insights into CBF regulation that would be inaccessible in a conventional experimental context. Our study implicates vasomotion of smooth muscle actin-covered vessels, rather than pericyte-covered capillaries, as the main mechanism for modulating tissue oxygenation. We also resolve seemingly paradoxical observations in the literature around reduced blood velocity in response to arteriolar constrictions and deduce the cause to be propagation of constrictions to upstream penetrating arterioles. We provide support for pericytes acting as signalling conduits for upstream smooth muscle activation, and erythrocyte deformation as a complementary regulatory mechanism. Finally, we caution against the use of blood velocity as a proxy measurement for flow. Our combined imaging-modelling platform complements conventional experimentation allowing cerebrovascular physiology to be probed in unprecedented detail.

biophysics↗