1989 — 2009 |
Raybould, Helen E |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. R29Activity Code Description: Undocumented code - click on the grant title for more information. |
Cholecystokinin--Role in Postprandial Gastric Motility @ University of California Los Angeles
The control of gastric motility and emptying following a meal is mediated by both hormonal and neural pathways. The aim of this proposal is to establish a role for cholecystokinin (CCK) in mediating changes in motility and emptying in response to duodenal stimulation, and investigate its pathways and mechanisms of action. In particular, the role of visceral afferent pathways in mediating changes in gastroduodenal motility induced by CCK and duodenal stimulants will be studied. Changes in gastroduodenal motility and gastric emptying in response to duodenal perfusion with protein, soya bean trypsin inhibitor, acid and glucose and duodenal distension and exogenous will be determined in anesthetized rats. Intraluminal pressure in the gastric corpus, antrum and duodenum will be measured using a multilumen catheter for perfused side hole manometry in combination with a sleeve sensor to simultaneously measure pyloric pressure. Gastric emptying studies will be carried out in conscious rats fitted with gastric fistulas using the double sampling technique. The role of CCK will be determined using a specific receptor antagonist and by immunoneutralization with a CCK monclonal antibody binding. The afferent pathways by which duodenal stimulation and CCK act will be studied using direct application of the sensory neurotoxin, capsaicin, to the vagus, coeliac/superior mesenteric ganglion or duodenum. Local administration of capsaicin to a peripheral nerve in adult animals produces an impairment of afferent C-fiber function and a long-lasting insensitivity to stimulation by physiological, electrical or chemical means. The mechanism of action of CCK will be assessed in electrophysiological recordings of vagal afferent fibers mediating intestinal mechano- and chemoreceptor discharge. The response of these afferents to duodenal stimulation will be studied in the presence of CCK, CCK receptor blockade or CCK immunoneutralization. There is abundant evidence that CCK acts in the periphery to inhibit food intake and alter feeding behaviors. There is evidence that this may be secondary to changes in gastrointestinal motility and transit. The elucidation of the pathway and mechanism of action of CCK on the gastrointestinal tract will contribute to a better understanding of postpostprandial events and consequently eating disorders.
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2003 — 2007 |
Raybould, Helen E |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Glucose-Sensing and Intestinal Feedback Inhibition @ University of California Davis
DESCRIPTION (provided by applicant): The ability of nutrients in the intestinal lumen to initiate changes in secretory and motor function in the gastrointestinal tract is well established. The precise nature of the "sensors" is not well characterized. Dietary carbohydrate in the intestinal lumen is well established to inhibit gastric emptying and food intake. The hypothesis to be tested is that dietary carbohydrate-induced inhibition of gastric emptying is dependent on binding of glucose to the sodium-glucose co-transporter SGLT on enterochromaffin (EC) cells, leading to release of 5-hydroxytryptamine (5-HT) that activates 5-HT3 receptors on extrinsic afferent nerve terminals in the intestinal mucosa. To test this hypothesis, studies are proposed to determine that (1) inhibition of gastric emptying by glucose is dependent on binding of glucose to SGLT; (2) glucose-induced release of 5-HT from EC cells is dependent on binding of glucose to SGLT; (3) activation of vagal and spinal afferents in response to glucose is dependent on SGLT and 5-HT3 receptor activation and (4) to demonstrate the expression of 5-HT3 receptors on vagal and spinal afferent terminals innervating the duodenum and their association with EC cells. The role of SGLT-1 and 5-HT release in glucose-induced inhibition of gastric emptying will be determined in awake rats by intestinal perfusion of analogues of glucose that are or are not substrates for SGLT, and the role of binding to SGLT will be determined by infusion of phloridzin that binds but is not internalized. Finally, the role of sodium ions or protons will be determined by alteration of their concentrations in intestinal glucose perfusates. 5-HT secretion will be measured in vitro from BON cells, a model for native EC cells, to determine that glucose acts directly on EC cells. The expression of SGLT by BON cells and native EC cells will be determined by measurement of expression of SGLT protein by Western blot and by immunocytochemistry. Duodenal vagal and spinal afferent discharge will be measured to determine whether glucose activates extrinsic afferent fiber activity and whether this is mediated by SGLT and a 5-HT3-receptor pathway. The cellular sites of expression of 5-HT3 receptors in the intestinal wall and their origins will be determined in immunohistochemical studies using antisera raised to the 5-HT3 receptor in tissue from intact, capsaicin-treated and extrinsically denervated rats. The relationship between primary afferent nerve terminals expressing 5-HT3 receptors and EC cells expressing 5-HT will be determined in double labeling experiments. These studies address sensory transduction in the gastrointestinal tract, which is important in the regulation of normal digestive function. There is evidence that sensory function of the intestine is altered in pathological conditions such as inflammatory bowel disease, functional bowel disease and obesity. A greater understanding of these sensory mechanisms will help in understanding the pathophysiology of these diseases.
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2010 — 2019 |
Raybould, Helen E |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Cholecystokinin - Role in Postprandial Gastric Motility @ University of California At Davis
? DESCRIPTION (provided by applicant): The only current effective treatment for obesity is surgical intervention. Novel treatments for obesity that avoid surgery are a desirable target. We investigate the mechanisms that attenuate the gut-brain vagal afferent pathway, resulting in loss of satiety signals from the gut that normally regulate food intake to provide peripheral targets fo novel therapies to effectively treat obesity. The ability of these gut-derived satiation signals to activate vagal afferent neurons and decrease food intake is absent in rodent models of diet-induced obesity (DIO), and altered gut-brain signaling has been shown to be present in human obesity. We have shown that an early response in high fat (HF) DIO is the onset of leptin resistance in vagal afferent neurons. To show causality, we developed a novel mouse model with a selective deletion of the leptin receptor in vagal afferent neurons. These mice gain weight and have increased adiposity on a regular chow diet, and do not increase their weight further on a high fat diet as would be expected. Thus, impaired leptin signaling in vagal afferent neurons is sufficient and necessary for an obese phenotype. We will now address the mechanisms that lead to leptin resistance in vagal afferent neurons, whether it can be reversed and if so, will thi reverse DIO. Obesity in humans and in rodent models is associated with impaired intestinal barrier function and metabolic endotoxemia, defined as low, chronic increases in plasma levels of the bacterial product lipopolysaccharide (LPS). In vagal afferent neurons, leptin-resistance can be induced by chronic treatment with low dose LPS and is accompanied by Toll-like receptor 4 (TLR4; receptor for LPS) activation and its downstream signal MyD88. Exposure of vagal afferent neurons to LPS in vitro increases SOCS3 and decreases leptin-induced pSTAT3. In the proposed research we will test the hypothesis that manipulation of the gut microbiota can restore leptin sensitivity in vagal afferent neurons and reverse DIO. The hypothesis will be addressed in two specific aims. In AIM 1, we will determine the intracellular signaling pathways leading to reversal of leptin resistance in vagal afferent neurons. We expect to find that: 1. leptn resistance in vagal afferent neurons is dependent on TLR4-MyD88 and/or Ghrelin receptor elevation of SOCS3, and 2. silencing SOCS3 or MyD88 will restore leptin sensitivity and reverse DIO. In AIM 2, expect to show that reversing the changes in intestinal barrier function using GLP2 which restores barrier function and normalizing gut microbiota using a inulin as a prebiotic can restore leptin sensitivity in vagal afferent neurons and reverses DIO. It is critical to understand the mechanisms by which vagal afferent neurons develop leptin resistance and how this can be reversed to restore satiety signaling from the gut. This proposal will take the novel approach of normalizing gut microbiota and barrier function to reverse leptin resistance. Defining both leptin sensitivity and changes in gut microbiota and barrier function are both priorities as the gut and vagal afferent neurons are peripheral targets for therapeutic interventio to solve the pressing need to treat obesity.
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2011 — 2012 |
Mills, David A (co-PI) [⬀] Raybould, Helen E |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Activation of Host-Probiotic Communication by Prebiotic Milk Oligosaccharides @ University of California At Davis
DESCRIPTION (provided by applicant): Probiotics and prebiotics are CAM interventions frequently employed by the American public to promote intestinal health and wellness. The presence of beneficial bacteria such as lactobacilli and bifidobacteria, whether delivered exogenously as probiotics or enriched via prebiotics, has been linked to positive health effects including reduction of gut inflammation, diarrhea and allergic reactions. At present, however, our understanding of the mechanism of action underlying these biological effects is significantly lacking. Milk oligosaccharides are naturally evolved prebiotic substrates that facilitate bifidobacterial enrichment and interaction with the host. Work from the UC Davis Milk Bioactives Program has shown that human milk oligosaccharides are utilized by select bifidobacterial strains and demonstrated that small mass oligosaccharide species are uniquely consumed by Bifidobacterium longum subsp. infantis. In addition, genomic analysis of B. infantis isolates has revealed unique gene clusters linked to milk oligosaccharide metabolism that are specifically induced during growth human milk glycans but are not expressed in cells grown on lactose or current commercial prebiotics-inulin or galactooligosaccharides (GOS). There is mounting evidence to indicate that various probiotics interact with intestinal epithelial cells via the production of soluble factors shown to alter intestinal permeability and inhibit inflammatory cascades in epithelial cells. We have obtained preliminary evidence to show a probiotic species, B. infantis, produces a soluble factor(s) that activates gut enteroendocrine (EC) cells. Importantly, growth of B. infantis on milk oligosaccharides markedly increases expression of the soluble factor(s) while growth on lactose, inulin, GOS resulted in little or no production of the factor(s). In addition, growth on milk oligosaccharides also increases the ability of B. infantis to bind to intestinal epithelial cells. Thus, the presence of B. infantis with its preferred growth substrate (milk oligosaccharides) increases the probiotic binding to epithelial cells followed by release of soluble factors capable of activating EC cells. This may result in release of humoral and neuroactive mediators, to initiate changes in GI function, food intake and glucose homeostasis. The overarching aim of this proposal is to characterize the interaction of prebiotic milk oligosaccharides and bifidobacterial species in binding and activation of two types of GI epithelial cells, enterocytes and EC cells and to determine the downstream benefits of this interaction in terms of improved regulation of glucose homeostasis and body weight regulation. We will test the hypothesis that growth of probiotic B. infantis in the presence of milk oligosaccharides results in increased binding to epithelial cells and production of soluble signaling molecules that elicit activation of EC cells and release of regulatory peptides that inhibit food intake and improve glucose homeostasis. This hypothesis will be tested using the following specific aims: 1.To determine the influence of milk oligosaccharides on bifidobacterial binding to intestinal epithelial cells. 2. To determine the mechanism and functional significance of enteroendocrine cell activation by conditioned media from bifidobaceteria growth on MOS. Prebiotics and probiotics play a significant role worldwide as a CAM aimed at intestinal health and wellness. A critical barrier to progress in this field is that the mechanism by which prebiotics and probiotics influence health is ill defined. This proposal will address the role of prebiotic milk oligosaccharides as a mechanism for potentiating probiotic efficacy of B. infantis through increased binding of intestinal cells and production of a soluble signal that activates enteroendocrine cells-the latter of which collectively constitute a diffuse neuroendocrine system of the gut. The significance of this proposal is a greater mechanistic understanding of the beneficial effects of synbiotic (prebioitic plus probiotic) applications and provide clues for treatment of obesity and other disorders that involve the sensory innervation of the gut, such as functional bowel disease. PUBLIC HEALTH RELEVANCE: Probiotics and prebiotics are CAM interventions frequently employed by the American public to promote intestinal health and wellness. The presence of beneficial bacteria such as lactobacilli and bifidobacteria, whether delivered exogenously as probiotics or enriched via prebiotics, has been linked to positive health effects including reduction of gut inflammation, diarrhea and allergic reactions. At present, however, our understanding of the mechanism of action underlying these biological effects is significantly lacking. The current proposal will determine the specific role of milk oligosaccharides, naturally evolved prebiotic substrates that facilitate bifidobacterial enrichment and interaction with the host, on gut epithelial cells.
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2014 — 2018 |
German, Bruce Lebrilla, Carlito B (co-PI) [⬀] Mills, David Andrew [⬀] Raybould, Helen E |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Activation of Probiotic Bifidobacteria by Milk Glyans @ University of California At Davis
Program Director/Principal Investigator (Last, First, Middle): MIIIS, D a v l d , A . PROJECT SUMMARY (See instmctions): The use of prebiotics and probiotics to restore a healthy gut microbiota represent a desirable target, but the lack of mechanistically relevant signatures of how specific bacteria interact with the intestinal environment and the host has hindered the development of effective and well-characterized prebiotic and probiotic treatments. The long-term goal is to translate the successful strategy of mammalian lactation, shown using human milk glycans, to the development of targeted, effective synbiotics by using plentiful and available bovine milk glycan streams. The overarching hypothesis to be tested is that the evolutionary relationship between infant-borne bifidobacteria and bovine milk glycans and glycoconjugates produce a synergistic human milk glycan-like phenotype that can effectively colonize, restore a healthy gut microbiota and induce host response to better protect epithelial barrier function and thus improve health outcomes. First, the team will address whether in infant-borne bifidobacteria species, complex milk glycoconjugates induce specific glycosyl hydrolases and transporters that are necessary to consume these complex substrates. Milk glycoconjugate catabolism by infant-borne bifidobacteria will be examined by detailed transcriptomics, specific enzymatic and transporter analysis, and glycoprofiling to identify precise links between glycan components and their cognate bifidobacterial processing mechanisms. Second, the research team will determine whether select infant-borne bifidobacteria that consume complex milk glycoconjugates compared to simple sugar substrates are more effective in inducing a protective response within the host epithelium. Measurements of bifidobacterial adherence, improved barrier function, release of inflammatory mediators and activation of enteroendocrine cells will be obtained from gut epithelial and enteroendocrine cells in vitro and ex vivo in rat small and large intestinal tissue. Finally, the team will determine whether modulation of intestinal function by application of synbiotic milk glycan- and glycoconjugate-consuming bifidobacteria improves outcomes in a rodent model of intestinal and metabolic disease. The significance of this project is that it will take a systematic and mechanistic approach to understanding the synbiotic relationship. RELEVANCE (See instmctions): The gut microbiome is a crucial component of human health. Safe and effective approaches for correcting, maintaining, and guiding establishment of a healthy gut microbiota, particularly in infancy and early childhood, are needed. The project is relevant to NCCAM's mission because it supports a portfolio of synbiotic interventions for improving health, with mechanistic signatures of biological effects.
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2014 — 2018 |
Raybould, Helen E |
T32Activity Code Description: To enable institutions to make National Research Service Awards to individuals selected by them for predoctoral and postdoctoral research training in specified shortage areas. |
Year-Long Exposure to Advanced Research (Year) Program For Vet Students @ University of California At Davis
DESCRIPTION (provided by applicant): This application represents the second 5 year competitive renewal of our veterinary student-targeted, pre-doctoral T32 training program (see PA-11-184), called the Yearlong Exposure to Advanced Research, or YEAR, Program at the University of California Davis (UCD). The YEAR Program is structured as a 1-year training opportunity for veterinary students from diverse backgrounds who seek to further their interest in hypothesis-based comparative and biomedical research. To accomplish this, applications will be encouraged from veterinary students at any AVMA-accredited School or College of Veterinary Medicine in the United States. The 3 veterinary students selected each year will be awarded full financial support to participate in supervised research under the guidance of any of 51 NIH-supported faculty...MD's, DVM's, PhD's...with active research programs from 23 departments in 6 schools and affiliated with 26 centers and participating in 7 graduate groups and programs across the UC Davis campus who have committed to welcoming veterinary students into their laboratories. Students will be afforded up to four 3-month long rotations during the year. This unique research training opportunity effectively adds a 5th year to the student's 4 year professional education and training. During the previous 8 years of the Program, 22 DVM students were selected and appointed as trainees, all of whom have elected to pursue their PhD degree after completing the program and before graduating from veterinary school. Thus, we have fulfilled all the expectations of this special T32 training mechanism, and utilized the YEAR Program to seek, recruit, and catalyze a new generation of veterinary students, especially women and underrepresented minorities, to embark on advanced scientific research training. In so doing, continued funding of the YEAR Program will help to ensure that highly trained comparative medical scientists will be available to meet the growing needs for principal investigator-driven and collaborative animal-based, biomedical research. Therefore, we seek to competitively renew our NIH funded T32 YEAR Program and allow us to continue to encourage the best and brightest veterinary students, particularly women and underrepresented minorities, to experience biomedical research and to convince them to pursue academic professional scientific careers.
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2016 — 2020 |
Raybould, Helen E |
U2CActivity Code Description: To support multi-component research resource projects and centers that will enhance the capability of resources to serve biomedical research. Substantial federal programmatic staff involvement is intended to assist investigators during performance of the research activities, as defined in the terms and conditions of the award. |
Microbiome Research Project @ University of California At Davis
MMPC-UCD MICROBIOME RESEARCH AND DEVELOPMENT PROJECT ABSTRACT (RESEARCH PROJECT) Bariatric surgeries, such as Roux-en-Y gastric bypass (RYGB), achieve rapid improvements in glucose homeostasis and long-term maintenance of reduced body weight. Obesity in humans and rodent models is associated with changes in the gut microbiota and bariatric surgery produces significant changes in the gut microbiota in obese humans; after RYGB the gut microbiota more closely resembles that of lean individuals. Similar changes are seen in rodent models of bariatric surgery; both RYGB and vertical sleeve gastrectomy (VSG) produce significant changes in the gut microbiota. The diversity of the gut microbiota and abundance at phyla and genera level differ in the different regions of the GI tract in rodent diet-induced obesity. How these changes in the microbiota in the different gut regions contribute to body weight gain or insulin resistance, or how these are modified after bariatric surgery is not known. The overarching goal of this study is to determine how the gut microbiota contributes to the physiological improvements seen with RYGB. A further goal of this proposal is to establish the pipeline to measure, analyze and integrate data from metabolomics and transcriptomics with the microbial community taxonomic profiles using bioinformatics tools and multivariate modeling. This project will utilize the expertise, resources, and services of all 4 Cores in our MMPC-UCD: Animal Care (Core B) and the 3 Phenotyping Cores (C, D, and E). Further, the metabolomic and functional characterization of the microbiota and host as well as the integrative analyses will be made available as Core services to clients of our Center. In Specific Aim I, the temporal and regional microbiota, host and microbial transcriptome, and metabolome of the intestinal tract after RYGB surgery will be determined. The hypothesis to be tested is that the gene expression and metabolism of the microbiota after RYGB induce changes in energy balance in the host that result in maintenance of weight loss and improved glucose homeostasis. Using a multi- omic (metagenomic, transcriptomic, and metabolomic) approach, the microbial community and metabolome of the luminal microbiota in the small and large intestine during both the active weight loss phase and stable weight maintenance phase after sham or RYGB surgery in male and female mice will be determined. The transcriptional responses of the gut and microbial population will be characterized, and data used to identify important biological pathways involved in the beneficial response to RYGB surgery. Specific Aim II will determine whether transplantation of RYGB microbiota protects mice from the deleterious effects of a HFD. The hypothesis to be tested is that that the RYGB microbiota regulates host physiology through production of metabolites and altered host-microbe crosstalk to decrease body weight and adiposity, and improve metabolic status. Contents from different regions of the gut from sham or RYGB mice will be used to colonize male and female germ-free mice subsequently challenged with low-fat diet (LFD) or HFD. The multi-omic approach developed in Specific Aim I will be used to identify microbial populations, and to characterize the transcriptional responses and metabolites of the gut, luminal contents, liver and skeletal muscle. We anticipate that we will identify a number of metabolites and a transcriptional signature that distinguishes RYGB microbiota recipients from sham recipients and that changes in metabolites and transcription are involved in the mechanisms bestowing protection from the negative effects of a HFD.
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2017 — 2018 |
Raybould, Helen E Reardon, Colin |
OT2Activity Code Description: A single-component research award that is not a grant, cooperative agreement or contract using Other Transaction Authorities |
Mapping of the Neuro-Immune Interface @ University of California At Davis
Project summary The nervous system and neurotransmitters can significantly effect the function of the immune system. Recently, we have identified a novel CD4+ T-cell population that regulates innate immune function preventing mortality during septic shock. These unique T-cells exert regulatory function through production and release of the neurotransmitter of acetylcholine, inhibiting NF-?B dependent gene transcription in splenic macrophages. Release of this immuno-modulatory molecule is evoked by neurons that innervate the spleen, and release the neurotransmitter norepinephrine. Originally proposed to originate in the celiac ganglia, the anatomic origin of this splenic innervation, has become highly controversial. This foundational knowledge will be crucial in developing therapeutics that utilize electrical stimulation to target this organ system. Equally important, communication between these neurons and CD4+ T-cells has been presumed to occur through intimate association and formation of a classical synapse, despite limited evidence for such a hypothesis. Alternatively, simple diffusion of neurotransmitters, including norepinephrine, has been shown to occur in the central nervous system. The overall goals of this project are to fill these significant gaps in the basic knowledge of the function of the immune system. This will be achieved in SA1, with mapping the origin of splenic sympathetic innervation using optogenetic stimulation of target ganglia. Using advanced imaging techniques in SA2, the interactions between neurons and CD4+ ChAT+ T-cells and the target effector immune cells in healthy mice will be determined. Completion of these studies will yield important information in the basic immunological function of neuro- immune communication, providing a foundation for development of therapeutic devices.
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