Publications by authors named "Ramon C Sun"

Absence of functional acid-α-glucosidase (GAA) leads to early-onset Pompe disease with cardiorespiratory and neuromuscular failure. A novel Pompe rat model ( ) was used to test the hypothesis that neonatal gene therapy with adeno-associated virus serotype 9 (AAV9) restores cardiorespiratory neuromuscular function across the lifespan. Temporal vein administration of AAV9-DES-GAA or sham (saline) injection was done on post-natal day 1; rats were studied at 6-12 months old.

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Excessive fructose intake is a risk factor for the development of obesity and its complications. Targeting ketohexokinase (KHK), the first enzyme of fructose metabolism, has been investigated for the management of metabolic dysfunction-associated steatotic liver disease (MASLD). We compared the effects of systemic, small molecule inhibitor of KHK enzymatic activity with hepatocyte-specific, N-acetylgalactosamine siRNA-mediated knockdown of KHK in mice on an HFD.

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Article Synopsis
  • * Patients with n-GSDs show varying neurological symptoms and require different treatment strategies compared to traditional GSDs, as recent studies have uncovered the genetic and biochemical mechanisms behind these conditions.
  • * New therapeutic approaches such as enzyme replacement therapy, substrate reduction therapy, and gene therapy have shown promising results in clinical trials, paving the way for improved treatment and better outcomes for n-GSD patients.
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The apolipoprotein E () gene has been studied due to its influence on Alzheimer's disease (AD) development and work in an mouse model recently demonstrated impaired respiratory motor plasticity following spinal cord injury (SCI). Individuals with AD often copresent with obstructive sleep apnea (OSA) characterized by cessations in breathing during sleep. Despite the prominence of genotype and sex as factors in AD progression, little is known about the impact of these variables on respiratory control.

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Microglia undergo two-stage activation in neurodegenerative diseases, known as disease-associated microglia (DAM). TREM2 mediates the DAM2 stage transition, but what regulates the first DAM1 stage transition is unknown. We report that glucose dyshomeostasis inhibits DAM1 activation and PKM2 plays a role.

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Glycogen synthase 1 (GYS1), the rate-limiting enzyme in muscle glycogen synthesis, plays a central role in energy homeostasis and has been proposed as a therapeutic target in multiple glycogen storage diseases. Despite decades of investigation, there are no known potent, selective small-molecule inhibitors of this enzyme. Here, we report the preclinical characterization of MZ-101, a small molecule that potently inhibits GYS1 in vitro and in vivo without inhibiting GYS2, a related isoform essential for synthesizing liver glycogen.

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Article Synopsis
  • Spinal cord injury (SCI) leads to issues with motor and sensory functions, and often results in gut problems like gastrointestinal complications and neurogenic bowel, affecting quality of life.
  • Research shows that high cervical SCI causes temporary gut imbalance (dysbiosis) which contributes to ongoing GI issues and hinders recovery.
  • Probiotic treatment can improve gut health and respiratory function post-SCI by reducing inflammation and enhancing nerve regeneration, highlighting the gut microbiome's potential as a treatment target for better recovery.
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High-resolution spatial imaging is transforming our understanding of foundational biology. Spatial metabolomics is an emerging field that enables the dissection of the complex metabolic landscape and heterogeneity from a thin tissue section. Currently, spatial metabolism highlights the remarkable complexity in two-dimensional space and is poised to be extended into the three-dimensional world of biology.

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Metabolic reprogramming has been recognized as one of the major mechanisms that fuel tumor initiation and progression. Our previous studies demonstrate that activation of Drp1 promotes fatty acid oxidation and downstream Wnt signaling. Here we investigate the role of Drp1 in regulating glycogen metabolism in colon cancer.

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The asexual stages of are defined by the rapidly growing tachyzoite during the acute infection and by the slow growing bradyzoite housed within tissue cysts during the chronic infection. These stages represent unique physiological states, each with distinct glucans reflecting differing metabolic needs. A defining feature of bradyzoites is the presence of insoluble storage glucans known as amylopectin granules (AGs), the function of which remains largely unexplored during the chronic infection.

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Background And Aims: Genome and epigenome wide association studies identified variants in carnitine palmitoyltransferase 1a (CPT1a) that associate with lipid traits. The goal of this study was to determine the role of liver-specific CPT1a on hepatic lipid metabolism.

Approach And Results: Male and female liver-specific knockout (LKO) and littermate controls were placed on a low-fat or high-fat diet (60% kcal fat) for 15 weeks.

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Oligodendrocytes (OLs) generate lipid-rich myelin membranes that wrap axons to enable efficient transmission of electrical impulses. Using a knockout mouse model and high-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) coupled with MS-based lipidomic analysis to determine the contribution of RIT1 to lipid homeostasis. Here, we report that RIT1 loss is associated with altered lipid levels in the central nervous system (CNS), including myelin-associated lipids within the corpus callosum (CC).

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Patients with Lafora disease have a mutation in EPM2A or EPM2B, resulting in dysregulation of glycogen metabolism throughout the body and aberrant glycogen molecules that aggregate into Lafora bodies. Lafora bodies are particularly damaging in the brain, where the aggregation drives seizures with increasing severity and frequency, coupled with neurodegeneration. Previous work employed mouse genetic models to reduce glycogen synthesis by approximately 50%, and this strategy significantly reduced Lafora body formation and disease phenotypes.

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Dopaminergic signaling in the nucleus accumbens shell (NAc) regulates neuronal activity relevant to reward-related learning, including cocaine-associated behaviors. Although astrocytes respond to dopamine and cocaine with structural changes, the impact of dopamine and cocaine on astrocyte functional plasticity has not been widely studied. Specifically, behavioral implications of voltage-gated channel activity in the canonically non-excitable astrocytes are not known.

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Background And Aims: Genome and epigenome wide association studies identified variants in carnitine palmitoyltransferase 1a (CPT1a) that associate with lipid traits. The goal of this study was to determine the impact by which liver-specific CPT1a deletion impacts hepatic lipid metabolism.

Approach And Results: Six-to-eight-week old male and female liver-specific knockout (LKO) and littermate controls were placed on a low-fat or high-fat diet (HFD; 60% kcal fat) for 15 weeks.

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Article Synopsis
  • Pompe disease is a serious inherited disorder that results in muscle weakness and neurological issues due to glycogen buildup, and while enzyme replacement therapy has improved patient outcomes, it has limitations.
  • Gene therapy is emerging as a promising alternative, especially for addressing neurological aspects of the disease, with recent studies focusing on the use of recombinant adeno-associated virus (rAAV) and lentiviral vectors (LV).
  • Current research shows that gene therapy could potentially correct the core issues of Pompe disease, but there are still challenges to tackle, including vector production, immune responses, and the possibility of needing to redose patients.
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  • Glycogen is a critical macromolecule for energy storage in the liver and muscles, but recent studies reveal its important roles in brain health and disease.
  • Researchers are uncovering how glycogen's function impacts brain cells and contributes to various neurological disorders known as neurological glycogen storage diseases (n-GSDs), which can lead to severe symptoms and neurodegeneration.
  • Innovative technologies and research advancements are paving the way for new treatment strategies for n-GSDs, highlighting the need for ongoing studies to fully understand glycogen's diverse roles in the brain and its implications for human health.
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Metabolites, lipids, and glycans are fundamental biomolecules involved in complex biological systems. They are metabolically channeled through a myriad of pathways and molecular processes that define the physiology and pathology of an organism. Here, we present a blueprint for the simultaneous analysis of spatial metabolome, lipidome, and glycome from a single tissue section using mass spectrometry imaging.

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Matrix assisted laser desorption/ionization imaging has greatly improved our understanding of spatial biology, however a robust bioinformatic pipeline for data analysis is lacking. Here, we demonstrate the application of high-dimensionality reduction/spatial clustering and histopathological annotation of matrix assisted laser desorption/ionization imaging datasets to assess tissue metabolic heterogeneity in human lung diseases. Using metabolic features identified from this pipeline, we hypothesize that metabolic channeling between glycogen and N-linked glycans is a critical metabolic process favoring pulmonary fibrosis progression.

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  • Brain glucose metabolism varies significantly across different brain areas and continues even after death, but methods of tissue preservation can influence the results.
  • Conventional methods like quick brain removal and freezing reduce glycogen and glucose levels and increase lactate, while microwave fixation preserves metabolism better.
  • In a mouse model of type 1 diabetes, researchers found overall reduced glucose metabolism in the brain, linked to decreased GLUT2 and metabolic enzyme expression, highlighting the importance of microwave fixation for accurate metabolic studies.
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High-cervical spinal cord injury often disrupts respiratory motor pathways and disables breathing in the affected population. Moreover, cervically injured individuals are at risk for developing acute lung injury, which predicts substantial mortality rates. While the correlation between acute lung injury and spinal cord injury has been found in the clinical setting, the field lacks an animal model to interrogate the fundamental biology of this relationship.

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Quiescent stem cells are activated in response to a mechanical or chemical injury to their tissue niche. Activated cells rapidly generate a heterogeneous progenitor population that regenerates the damaged tissues. While the transcriptional cadence that generates heterogeneity is known, the metabolic pathways influencing the transcriptional machinery to establish a heterogeneous progenitor population remains unclear.

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The E4 allele of Apolipoprotein E (APOE) is associated with both metabolic dysfunction and a heightened pro-inflammatory response: two findings that may be intrinsically linked through the concept of immunometabolism. Here, we combined bulk, single-cell, and spatial transcriptomics with cell-specific and spatially resolved metabolic analyses in mice expressing human APOE to systematically address the role of APOE across age, neuroinflammation, and AD pathology. RNA sequencing (RNA-seq) highlighted immunometabolic changes across the APOE4 glial transcriptome, specifically in subsets of metabolically distinct microglia enriched in the E4 brain during aging or following an inflammatory challenge.

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Synopsis of recent research by authors named "Ramon C Sun"

  • - Ramon C. Sun's recent research focuses on the intersection of glycogen metabolism and neurological health, with studies investigating various metabolic disorders and their implications for conditions such as obesity, Alzheimer's disease, and glycogen storage diseases.
  • - His work also explores the therapeutic potential of targeting metabolic pathways, including the development of small-molecule inhibitors for treating glycogen storage disorders, such as Pompe disease, and the implications of apolipoprotein E on neuroinflammation and metabolic dysfunction.
  • - Additionally, Sun's research highlights innovative methodologies, such as spatial metabolomics, to analyze metabolic heterogeneity in tissues, enhancing understanding of disease mechanisms, especially in the context of brain health and systemic metabolic reprogramming.