Location: Children's Nutrition Research Center2010 Annual Report
1a. Objectives (from AD-416)
Obesity and related co-morbidities are among the most profound public health problems today. Obesity prevalence has increased dramatically in recent decades and is affecting individuals at every age, including women of child-bearing age. Children's Nutrition Research Center researchers will address these issues by targeting these objectives: 1) determine the role of the circadian clock in regulation of food intake and the interaction between diet composition and circadian rhythms of food intake on body weight control during post-weaning and adult life; determine the specific role of central and peripheral clocks, as well as circadian output pathways in maintaining the homeostasis of food intake; 2)determine roles for adipocyte- and skeletal myocyte-specific circadian clocks in high fat feeding-induced alterations of feeding behavior, adiposity, and insulin sensitivity; relate observed changes to circadian patterns in gene expression, protein levels, and metabolic fluxes; 3) determine whether early nutritional intervention-mediated metabolic programming predisposes toward age-onset induced obesity and insulin resistance through modulation of intracellular circadian clocks; 4) establish a model to investigate the impact of prematurity on the gastrointestinal and metabolic response to perinatal nutrition; 5) compare the impact of continuous versus intermittent bolus delivery of nutrients provided enterally or parenterally on protein synthesis and accretion in neonatal pigs and identify the intracellular signaling mechanism involved; 6) define the specific classes of resident and emigrated leukocytes in adipose tissue, their phenotypic changes during development of obesity, and inflammatory mediators involved; 7) characterize leukocyte patterns and gene expression in adipose tissue of animals fed normal and high fat diets; 8) investigate changes of SIRT3 gene expression in the liver by various physiological and pathophysiological stimuli, and study the effects of SIRT3 expression on hepatic metabolism, oxidative stress, and fat deposition; 9) determine the role of protein kinase C interacting cousin of thioredoxin in insulin-mediated growth, macronutrient metabolism, and insulin resistance in the liver; 10) define the central action of glucagon-like peptide-2 (GLP-2) receptor on food intake and inter-organ macronutrient flux; 11) identify genes that show epigenetic dysregulation in obesity using a candidate-gene approach in a mouse model; 12) determine if methylation and expression of specific genes in hypothalamus and/or adipose tissue differ between lean and obese animals and determine if maternal obesity and/or nutrition before and during pregnancy persistently alters epigenetic regulation in offspring; 13) determine if maternal obesity and/or nutrition before and during pregnancy persistently alters epigenetic regulation in offspring hypothalamus or adipose tissue; 14) identify placental epigenetic mechanisms that affect fetal nutrition, growth and development; and 15) determine how programming of glucose intolerance, obesity, and the epigenetic dysregulation of skeletal muscle-growth in mice is affected by maternal diet during development.
1b. Approach (from AD-416)
The research will be accomplished using a variety of animal models and scientific tools to simulate the human newborn and/or child. Animal models will be used to understand the central and peripheral circadian clock mechanisms that influence eating behavior, metabolism, and energy balance. Newborm animal models will be used to examine the effect of chronic parenteral nutrition during the neonatal period on glucose tolerance, insulin sensitivity, and body composition during late infancy and adolescence. Researchers will investigate the effects of intermittent bolus feeding versus continuous feeding, delivered either enterally or parenterally, on protein synthesis in neonatal animal models. This will allow our team to determine the long-term impact of these feeding modalities on growth and body composition. Various models will be placed on obesigenic diets at 5-6 weeks of age and evaluated at 7 days, 5 weeks, and 6 months to define a blood leukocyte expression profile at these time points. Children's Nutrition Research Center scientists will also characterize the functions of intracellular systems in the liver and their influences on the onset of fatty liver disease and glucose homeostasis. Additional investigation will occur on the intracellular signaling pathways of GLP-2 and their metabolic effects on food intake, energy expenditure, and glucose homeostasis. Various mouse models, and a human model of epigenetic dysregulation compromising placental development, will be used to test if maternal obesity and fetal nutrition during development affects the establishment of gene-specific DNA methylation patterns in the developing fetus, which would cause permanent changes in gene expression, metabolism, food intake regulation, and body weight.
3. Progress Report
Project 1. We learned that the peripheral clock indirectly controls leptin transcription by interacting with other transcription factors on the leptin promoter. We discovered that the peripheral clock controls bile acid synthesis in the liver by regulating the expression of the FXR and SHP that inhibit the expression of Cyp7A1 for bile acid synthesis. Animal models show a significant decrease in the expression of FXR and SHP in the liver which is correlated with a dramatic increase in Cyp7A1 expression and bile acid levels in serum and the liver. Project 2. We studied whether pretreatment with GLP-2 reduces inflammation and NEC in premature piglets; we may extend the GLP-2 treatment period to test whether this might prevent NEC. We completed studies on the effects of continuous parenteral amino acid infusion on protein synthesis in newborns to identify optimum nutrition support regimens to increase growth of premature infants. We compared how amino acids and insulin separately increase protein synthesis in different tissues of newborn pigs. We showed that both amino acids and insulin increased protein synthesis in a variety of different types of muscles. We studied the effect of prolonged parenteral leucine infusion on protein synthesis in neonatal pigs. We examined the time course of changes in protein synthesis in newborn muscle after a meal. Project 3. We examined livers of male C57BL/6 mice under various diet conditions for detection of fat tissue. The function of the CD11c macrophage surface protein was analyzed by studying mice deficient in CD11c. We studied diet reversal for changes in inflammatory gene expression. We began collaborating on a study on inflammatory bowel disease utilizing our mouse strains with genetically engineered deletions of proteins important in obesity-related inflammation. Project 4. We studied expression of SIRT3 in mouse liver under various conditions; mouse liver SIRT3 protein levels are increased in mice that underwent 12 or 18 months of 40% food restriction, but is down-regulated in mice fed high-fat diet for 16 wks. We analyzed PICOT expression in mouse embryos and adult tissue. We genetically generated a mouse line that lacks the GLP-2 receptor in brain neurons. We found GLP-2 receptor activation is essential for maintaining blood glucose levels by modulating the brain neuron activities. We found deficiency of GLP-2 receptor in brain neurons increases gastric emptying, decreases insulin sensitivity, and has higher rates of glucose synthesis in liver in type 2 diabetes. We began feeding studies of mice lacking the receptor for a stomach-secreted feeding regulating hormone GHS-R. Project 5. We identified over 1000 genomic regions undergoing postnatal DNA methylation changes, and validated over 10. We longitudinally measured body weight in a cohort of Avy/a mice. We performed DNA methylation profiling on Illumina arrays on 6 AnCHM tissues as an alternative to MSAM. We tested several new antibodies to the NLRP7 protein; we found some evidence that NLRP7 may be cleaved by caspase. We isolated RNA from liver at 1 yr, and muscle (soleus) at p21 and 1 yr and performed gene expression profiling.
Kellermayer, R., Balasa, A., Zhang, W., Lee, S., Mirza, S., Chakravarty, A., Szigeti, R., Laritsky, E., Tatevian, N., Smith, W.C., Shen, L., Waterland, R.A. 2010. Epigenetic maturation in colonic mucosa continues beyond infancy in mice. Human Molecular Genetics. 19(11):2168-2176.