Timothy H. Moran - US grants

The research proposed in this grant attempts to display the integrative physiology in the upper gastrointestinal tract and to relate features of this physiology to the control of food intake. The program, therefore, has both a physiological and a behavioral aspect and important health related findings can be expected from both. Rhesus monkeys and rats will be the experimental subjects. The following experiments are devised. 1) A definition of the integrative mechanisms relating the stomach's emptying to the contents of the intestine by displaying changes in the delivery of liquids from the stomach when nutrients are placed in the intestine and when intravenous infusions of gut hormones are given. This will demonstrate that the nutrients and the hormones that they release from the intestine such as cholecystokinin (CCK) will coordinate the stomach's emptying and by reducing the amount of a meal passing into the intestine cause the stomach to retain food and to distend. 2) A demonstration that contents of the stomach and the intestine can inhibit food intake. Infusions of nutrients into the intestine and intravenous infusions of gut hormones such as CCK will be studied alone or with distending loads of non-nutrient physiological saline in the stomach for effects on the consumption of sucrose solutions and monkey chow. A gastric balloon will test the inhibition on food intake from stomach distention alone. These experiments challenge the hypothesis that a major inhibition on food intake comes from the distended stomach. 3) A display of the receptor sites for gut hormones to determine their likely role in physiology and behavior. In vitro receptor autoradiography will be employed to demonstrate CCK, bombesin and other gut hormone receptor sites. 4) Demonstration of the physiological and behavioral effects of surgical disconnections of the gastric outlet by pyloroplasty and off the neural links from stomach to brain by vagotomy. This will also test the hypothesis that distention of the stomach provoked by intestinal nutrients and gut hormones during feeding produced a termination of feeding by sensations carried through the vagus nerve. Knowledge of this basic physiology and functional relationships to feeding behavior is crucial to any effort to define the pathophysiology and therefore the most appropriate treatments for such digestive disorders as peptic ulcer and alimentary hypoglycemia and behavioral disorders such as obesity, anorexia nervosa and bulimia.

DESCRIPTION (provided by applicant): Obesity is a major public health concern: the prevalence of obesity in the US has increased dramatically, reaching rates greater than 30%. Although lifestyle and pharmacological therapies are successful in the short term, subsequent regain of lost weight is common. Surgical approaches such as gastric banding and Roux-en-Y gastric bypass (RYGB) achieve weight losses of greater than 20% or 25% of body weight maintained for up to 15 years. RYGB results in rapid restoration of insulin sensitivity prior to appreciable weight loss. The mechanisms underlying the success of RYGB are poorly understood. RYGB is a dual procedure involving creation of a small gastric pouch and bypass of the remaining stomach and upper intestines such that ingested calories are rapidly delivered to more distal intestinal sites. How each separately contributes to the beneficial effects of the surgery has not been experimentally assessed. The present proposal directly assesses the consequences of nutrient delivery to the small intestine and will identify the underlying mechanisms using rat and nonhuman primate experiments. The experiments under the first specific aim expand our current rat model of intestinal nutrient delivery in lean rats to a diet-induced obesity model focusing on the elucidation of central and peripheral mechanisms. Our preliminary data in lean rats demonstrate that small volumes of jejunal nutrient infusions produce persistent reductions in food intake well beyond their caloric content and support a role for gut peptides in mediating these changes. The proposed experiments will further characterize such feeding inhibition in obese rats and will directly assess the roles of specific gut peptides, alterations in taste preferences and neural homeostatic signaling systems in the suppressions of food intake. Additional experiments will compare the hormonal profiles produced by intestinal nutrient infusion to that following sleeve gastrectomy, another bariatric procedure with significant efficacy. Finally, we will assess the potential role of vagal afferent signaling in mediating the effects of intestinal infusions. The experiments under the second specific aim translate these findings to nonhuman primates using our established nonhuman primate model that has been successful in elucidating feedback controls on food intake and gastric emptying that have direct relevance to man. Here we propose to characterize the feeding inhibitory effects of small intestinal nutrient delivery in rhesus monkeys as well as in our unique obese Bonnet macaques to assess potential mechanisms of action and determine the efficacy of such nutrient delivery for producing long term changes in food intake and body weight. . PUBLIC HEALTH RELEVANCE: The relevance of the proposed work is to provide an understanding of the mechanisms underlying the reductions in eating and body weight following gastric bypass surgery. This understanding could lead to less invasive but effective obesity therapies.

Genetic studies have provided compelling evidence that heritable factors play a prominent role in the risk for developing a number of major mental disorders including schizophrenia, bipolar disorder and Alzheimer's disease. Furthermore, neurobiologic studies have demonstrated structural, metabolic and synaptic neurochemical abnormalities in individuals affected with these major mental disorders. A critical issue, at this juncture, is how the gap between molecular genetics and neurobiology might be bridged to begin to understand the mechanisms whereby abnormal gene expression affects brain development and function. As a clinically relevant and heuristically useful strategy, this Neuroscience Work Group will focus on the neurobiologic consequences of gene imbalance of mouse chromosome 16 (MMU16). Previous studies of this Group and of others have demonstrated extensive homology between a portion of MMU16 and human chromosome 21 (HSA 21). Down Syndrome (DS) results from triplication of the distal end of the long arm of HSA 21. DS is the most common genetically identified cause of mental retardation, is associated with a high risk for affective disorder, and invariably results in the pathology of Alzheimer's disease by the fourth decade. Mice with trisomy of MMU16 (Ts16) can be generated reproducibly by a specific breeding scheme. These mice exhibit many of the phenotypic characteristics of DS, including endocardial cushion defects, brain hypoplasia, synaptic neurochemical abnormalities and altered expression of amyloid precursor protein (APP). The Group, which has collaborated effectively for seven years, includes members with expertise in molecular genetics, developmental neurobiology, synaptic neurochemistry, and physiologic psychology. In the proposed studies, the Group will utilize mice with Ts16 and exploit current molecular strategies to generate mice transgenic for specific genes on MMU16 to determine how perturbation of the copy numbers of specific genes or group of genes affects their expression in the developing nervous system. Specifically, in Project I, mice will be developed that are transgenic for specific genes or portions thereof; such mice are directly relevant to the experimental goals of the other three projects. Project II will utilize both Ts16 mice and mice with specific transgenes to determine intrinsic and extrinsic fetal brain cells to identify factors that impair basal forebrain cholinergic development, somatostatin expression, and sensitivity to oxidative stress in Ts16, features analogous to those observed in DS.

The purpose of this core is to provide a phenotypic validation of the genetic manipulations made under the various projects. This core will provide neurobiological evaluations of trangenic and transonic lines constructed to provide overexpression of single or multiple genes from the Down syndrome region of human chromosome 21 or their murine counterparts. Behavioral, neurochemical and histological studies will be carried out to identify the specific neurobiological effects of overexpression of these genes to determine what genes singly or in combination with others may account for the mental retardation or other neurobiological outcomes exhibited in Down syndrome. The behavioral screens will include assessment of sensory and motoria development in neonatal animals, spontaneous locomotor activity in adults, and testing of aspects of learning and memory in both neonates and adults using conditioning paradigms and assessments of the animal's ability to acquire spatial discriminations and form learning sets. Brains will be screened for potential alterations in aspects of synaptic neurochemistry including assessments of norepinephrine, dopamine, serotonin and cholinergic transmission. Brains of trangenic and transonic animals will also be screened for neuropathological signs consistent with Down syndrome. These screens will include developmental and crossectional assessments of the presence of neuritic plaques, changes in synapse numbers and effects on specific synaptic membrane proteins neurofilament proteins and markers for synaptic transmitter. This Core will serve 3 of the 4 projects and provide assessments of the neurobiological outcomes of the specific manipulations proposed in those projects.

Virus infections of the developing brain are a serious and common cause of pediatric neurological disease. Since the brain continues to develop after birth, central nervous system (CNS) injuries can be sustained following pre-, peri- and post-natal virus infections. HIV causes one of the most common virus-induced neurological diseases of children in the US. Notably, although clinical evidence of developmental neurological disease is a prominent finding in HIV infected children, the mechanisms of the virus-related neurological developmental injury are poorly understood. Studies of Borna disease virus (BDV)-infected neonatal Lewis rats have revealed important principles about the neuroanatomical and neurobehavioral effects on brain development of persistent virus infections of the brain. This animal model system is useful for the study the pathogenesis of developmental neurological diseases following perinatal HIV infection. In Specific Aim 1, BDV-induced developmental damage to the rat cerebellum will be measured via quantitative measurements of cerebellar size and cortical development and cerebellar and hippocampal dentate gyrus neuron survival over time. In a mechanistic analysis, we will identify changes in important developmental gene mRNA expression in the cerebellum following perinatal virus infection. Specific Aim 2 explores associated abnormalities in the development of sensorimotor, emotion, cognitive, and social behaviors and abnormalities in neurotransmitter concentrations in the infected brain as a function of time post virus infection. The results of these multidimensional neuroanatomical/ neurobehavioral pathogenesis studies will advance our knowledge of the effects of viruses on infant brain development, and of anatomical- behavioral pathology linkages following perinatal infection with a persistent RNA virus.

The development of mouse models of Down Syndrome, with appropriate gene expression to mimic what takes place with a trisomy of human chromosome 21, provides test systems for potential therapeutic interventions aimed at improving cognitive performance. As detailed under Dr. Davisson's Project, the Ts65Dn mouse containing homologs to the majority of the genes on human chromosome 21. This segmental trisomy model has a number of distinct advantages over previous models, not the least of which is survival to adulthood. We and others have demonstrative a cognitive phenotype in the Ts65Dn mouse which has clear similarities to that seen in Down Syndrome. Ts65Dn mice demonstrate performance deficits in tests of learning and memory against a background of relatively intact motor and sensory abilities. Both acetylcholine and glutamate play important roles in learning and memory and are involved in neural organization during development. Alterations of cholinergic and glutamatergic activity in DS have been identified. The proposed experiments will 1) provide a more complete characterization of the development of cholinergic and glutamatergic systems in Ts65Dn mice. This characterization will provide a necessary background for proposed experiments aimed at, 2) assessing whether strategies aimed at blocking cholinergic degradation with the acetyl cholinesterase at, 2) assessing whether strategies aimed at blocking cholinergic degradation with the acetyl cholinesterase inhibitor donepezil or producing a development increase in cholinergic function with prenatal choline can improve performance in the Ts65Dn mouse, 3) assessing whether developmental treatment with piracetan alone, or piracetam combined with prenatal choline administration, improves performance in the Ts65Dn, and 4) assessing wheth4r developmental treatment with the neuroprotective agent acetyl-L-carnitine prevents cholinergic degeneration and results in improved cognitive performance in the Ts65Dn mouse. In these studies, we will assess performance in the Morris water maze and a cued and contextual conditioning paradigm. We will also monitor activity over the 24 hour cycle and in elevated plus maze paradigm. Behavioral assessments will be followed up by appropriate neurobiological analyses to determine whether the neurochemical systems impacted by these treatments respond similar in Ts65Dn and control mice.

Support is requested to enhance the annual meeting of the Society for the Study of Ingestive Behavior (SSIB). This annual meeting is the nation's principal forum for scientists and clinicians involved in basic and applied research in ingestive behavior. Two mechanisms are proposed: 1) establishment of young investigator awards to provide financial support for outstanding United States graduate students and postdoctoral fellows to attend the annual meeting and present their research findings; 2) establishment of an NIH sponsored symposium to inform the membership of important technical and conceptual advances in related fields. This symposium will permit SSIB to invite established investigators from other fields who are not currently SSIB members to present their latest work to our membership and interact with the members throughout the annual meeting. These programs will: 1) foster the development of young investigators in the field of ingestive behavior research, 2) increase the overall profile of ingestive behavior research and, 3) translate into new basic knowledge and improved clinical practice in such diverse areas as obesity, eating and metabolic disorders, and cardiovascular regulation.

DESCRIPTION: Obesity has reached epidemic proportions in the United States, and both genetic and environmental contributions to the development and maintenance of obesity have been identified in human studies and animal models. Recent rodent models of genetic obesity have hypothalamic signaling pathways related to the overall control of metabolism and energy balance. Unlike these strains, the obese Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a unique genetic model of obesity with an identified deficit in a peripheral gut-brain peptide signaling pathway critical to the within meal control of food intake. OLETF rats spontaneously lack the promoter region for the gene that encodes for the cholecystokinin (CCK) A receptor, the subtype that mediates the satiety actions of this meal-elicited peptide. OLETF rats are obese and hyperphagic, and we have shown that their hyperphagia is characterized by increased meal size, consistent with the lack of a meal related signal important in the negative feedback control of food intake. In this proposal, we hypothesize that OLETF hyperphagia and obesity: 1) depends upon their genetically determined inability to detect meal-related CCK negative feedback signals critical in the control of meal size, and 2) is not dependent on altered central nervous system processing of other metabolic and hypothalamic signals important in the overall control of energy balance. Experiments in this proposal are designed to address multiple aspects of this hypothesis. Specifically, we will: 1) identify the roles of increased meal size and hyperphagia in the development of obesity in OLETF rats, 2) characterize metabolic profiles and patterns of hypothalamic gene expression in ad lib and pair fed OLETF rats, 3) identify potential interactions between exercise and disordered patterns of food intake in OLETF rats, 4) characterize OLETF feeding and metabolic responses to high fat and macronutrient selection diets and 5) compare the OLETF rat to a newly available CCK-A knockout mouse that does not develop obesity. Together, results from these studies will: 1) identify and characterize the ways in which a unique genetic deficit in a peripheral satiety signaling pathway interacts with a range of environmental factors (exercise, dietary restriction, diet composition) to modulate the development and maintenance of obesity, and 2) identify how such a satiety deficit interacts with central hypothalamic pathways mediating the control of energy balance.

Support is requested to enhance the annual meeting of the Society for the Study of Ingestive Behavior (SSIB). This annual meeting is the nation's principal forum for scientists and clinicians involved in basic and applied research in ingestive behavior. Two mechanisms are proposed: 1) establishment of young investigator awards to provide financial support for outstanding United States graduate students and postdoctoral fellows to attend the annual meeting and present their research findings; 2) establishment of an NIH sponsored symposium to inform the membership of important technical and conceptual advances in related fields. This symposium will permit SSIB to invite established investigators from other fields who are not currently SSIB members to present their latest work to our membership and interact with the members throughout the annual meeting. These programs will: 1) foster the development of young investigators in the field of ingestive behavior research, 2) increase the overall profile of ingestive behavior research and, 3) translate into new basic knowledge and improved clinical practice in such diverse areas as obesity, eating and metabolic disorders, and cardiovascular regulation.

DESCRIPTION (provided by applicant): Low carbohydrate dieting plans are increasingly popular. Recent data from randomized clinical studies have shown that low carbohydrate diets have increased efficacy at 6 month time points as compared to low-fat diets. Despite the popularity and efficacy of low carbohydrate diets, little is known about the mechanisms through which they affect food intake and body weight. It has been suggested that transition from a carbohydrate to a lipid metabolism results in greater energy utilization but data from clinical studies suggest that reduced food intake accounts for the increased weight loss. We have conducted animal studies to begin to assess how low carbohydrate diets may affect food intake and body weight. Our preliminary data demonstrate that rats maintained on a low carbohydrate-high fat diet consume less food and gain less weight than rats on an ordinary high carbohydrate-high fat diet. Low carbohydrate diet rats also have increased sensitivity to the anorexigenic effects of a melanocortin agonist and decreased sensitivity to the orexigenic effects of a melanocortin antagonist. Furthermore, rats on a low carbohydrate diet do not show a rebound hyperphagia in response to food deprivation and patterns of hypothalamic gene expression in response to fasting are altered in a manner consistent with the lack of a compensatory feeding response. These data suggest potential mechanisms underlying the ability of low carbohydrate diets to produce weight loss without inducing "hunger". The proposed experiments will provide a more complete characterization of the consequences of consuming a low carbohydrate diet by 1) generalizing the findings to a diet composition similar to that consumed by individuals following Atkins-type diets, 2) assessing whether the response to melanocortins is specific or generalizes to other anorexigenic and orexigenic stimuli and 3) assessing how diet composition may differentially alter hypothalamic responses to the state of chronic food restriction that accompanies dieting.

[unreadable] DESCRIPTION (provided by applicant): Obesity is a worldwide public health problem and recent work has suggested that alterations in maternal nutritional status may increase the risk of becoming obese. Epidemiological data have shown that maternal under-nutrition can lead to intrauterine growth retardation with long-term consequences to offspring including hypertension, cardiovascular disease, type 2 diabetes and obesity. Evidence is now emerging that maternal over-nutrition may have similar long-term consequences. Specifically, maternal consumption of a high fat diet, characteristic of the modern day Western lifestyle, has been shown to lead to metabolic disorders such as obesity and insulin resistance in offspring. The mechanisms mediating the consequences of maternal over-nutrition are not well understood. The overall goal of this proposal is to characterize the short- and long-term effects of maternal consumption of a high fat diet and resulting obesity in a polygenic diet induced rat model of obesity. The specific experiments address numerous aspects of the RFA in that they will: 1) characterize an animal model appropriate for the study of metabolic consequences of maternal high fat diet consumption and obesity, 2) define critical periods of susceptibility to metabolic perturbations on neural pathways involved in energy balance and 3) investigate the role of epigenetic changes as mediating mechanisms. The specific aims are: 1) To determine the developmental time course of behavioral and endocrine alterations resulting from maternal high fat diet consumption in obesity prone Sprague Dawley rats, 2) To test the hypothesis that maternal consumption of high fat diet produces alterations in hypothalamic neuropeptide signaling systems involved in energy balance that bias the developing pups toward obesity and metabolic disturbances, and 3) To determine whether high fat diet results in obesity and metabolic disturbances in offspring through epigenetic modifications. We hypothesize that genes that are critical to energy homeostasis are subject to regulation by DNA methylation and are differentially methylated in response to exposure to maternal high fat diet consumption and obesity. The results of these experiments will enhance our understanding of the etiology of obesity and metabolic disease ultimately allowing the development of rational clinical interventions for such conditions. [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Obesity has reached epidemic proportions in the United States, and both genetic and environmental contributions to the development and maintenance of obesity have been identified in human studies and animal models. Analyses of rodent models of genetic obesity have illuminated hypothalamic signaling pathways related to the overall control of metabolism and energy balance. The majority of these have involved deficits in aspects of the leptin signaling pathway. The obese Otsuka Long-Evans Tokushima Fatty (OLETF) rat lacking CCK1 receptors is a unique genetic model of obesity in that it appears to have deficits in both a peripheral gut-brain peptide signaling pathway critical to the within meal control of food intake and in hypothalamic signaling pathways that are independent of leptin. OLETF rats are obese and hyperphagic, and we have shown that their hyperphagia, characterized by increased meal size, accounts for the obesity. Experiments under the first specific aim will characterize the contributions of vagal and dorsal medial hypothalamic (DMH) CCK-A receptors in the disordered meal patterns and overall hyperpagia and evaluate the role of DMH overexpression of NPY in their hyperphagia. In the second specific aim, we will follow up on our studies demonstrating the ability of exercise to normalize food intake and body weight in OLETF rats. These experiments will assess interactions between exercise and diet, assess a role for DMH corticotrophin releasing peptide (CRF) in mediating the effects of exercise and use microarracy techniques in an attempt to identify novel factors that contribute to both the short and long term effects of exercise. Experiments under the third specific aim will examine the role of maternal influences in the development of hyperphagia and obesity. Preliminary results demonstrate that cross fostering control Long Evans Tokushima Otsuka (LETO) pups to OLETF dams results in obesity in male offspring. Proposed experiments will investigate the basis of this phenomenon both from the standpoint of the maternal factors involved and how that experience modifies patterns of connectivity and gene expression in the brains of the developing pups. Together, results from these studies will: 1) characterize the mechanisms underlying the hyperphagia and obesity in OLETF rats, 2) identify exercise induced factors that modify the effects of disordered peripheral satiety and hypothalamic signaling, and 3) identify developmental influences that may bias towards obesity. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Obesity is a major public health concern: the prevalence of obesity in the US has increased dramatically, reaching rates greater than 30%. Although lifestyle and pharmacological therapies are successful in the short term, subsequent regain of lost weight is common. Surgical approaches such as gastric banding and Roux-en-Y gastric bypass (RYGB) achieve weight losses of greater than 20% or 25% of body weight maintained for up to 15 years. RYGB results in rapid restoration of insulin sensitivity prior to appreciable weight loss. The mechanisms underlying the success of RYGB are poorly understood. RYGB is a dual procedure involving creation of a small gastric pouch and bypass of the remaining stomach and upper intestines such that ingested calories are rapidly delivered to more distal intestinal sites. How each separately contributes to the beneficial effects of the surgery has not been experimentally assessed. The present proposal directly assesses the consequences of nutrient delivery to the small intestine and will identify the underlying mechanisms using rat and nonhuman primate experiments. The experiments under the first specific aim expands our current rat model of intestinal nutrient delivery in lean rats to a diet-induced obesity model focusing on the elucidation of central and peripheral mechanisms. Our preliminary data in lean rats demonstrate that small volumes of jejunal nutrient infusions produce persistent reductions in food intake well beyond their caloric content and support a role for gut peptides in mediating these changes. The proposed experiments will further characterize such feeding inhibition in obese rats and will directly assess the roles of specific gut peptides, alterations in taste preferences and neural homeostatic signaling systems in the suppressions of food intake. Additional experiments will assess the potential role of vagal afferent signaling in mediating these effects. The experiments under the second specific aim translate these findings to nonhuman primates using our established nonhuman primate model that has been successful in elucidating feedback controls on food intake and gastric emptying that have direct relevance to man. Here we propose to characterize the feeding inhibitory effects of small intestinal nutrient delivery in rhesus monkeys as well as in our unique obese Bonnet macaques to assess potential mechanisms of action and determine the efficacy of such nutrient delivery for producing long term changes in food intake and body weight.