2007 Annual Report
1a.Objectives (from AD-416)
1. Characterize the role of newly identified metabolic regulators within the nuclear receptor superfamily, including the PPARs, LXRs, FXR, CAR and PXR, as targets of nutrients and other natural products that have direct regulatory effects on metabolic pathways.
2. Determine the cis- and trans-Paneth cell regulatory genes that contribute to the upregulation of the redundant soluble maltase-glucoamylase in the membrane maltase-glucoamylase KO mouse.
3. Test the hypothesis that long chain, unsaturated fatty acids (e.g. oleate) enhance fatty acid-responsive gene expression to a greater extent than shorter saturated fatty acids (e.g. palmitate).
4. Understand the direct effects of urea cycle intermediates both in sustaining ureagenesis in the presence of an enzymatic disorder and in maintaining nitric oxide production.
1b.Approach (from AD-416)
1. Identify nutritional products and other natural products that regulate the activity of nuclear hormone receptors, with a specific focus on PPAR (Peroxisome Proliferator Activated Receptor) isoforms, define the active agents that modulate receptor functions, and characterize the actions of such agents at the levels of receptor function and target genes.
2. There is a 6-fold increase in the soluble maltase-glucoamylase message in mice with membrane maltase-glucoamylase ablation. This increase is present in suckling as well as weaned null mice. This presents a novel model of gene regulation by dietary carbohydrates. The regulatory genes involved in this upregulation are under investigation by microarray analysis and will be confirmed and extended by mechanistic in vitro studies in the mICcl2 cell line.
3. Measure the effects of specific PPAR(alpha) and PPAR(beta/delta) agonists on metabolic gene expression in isolated cardiomyocytes; and by determining whether loss of PPAR(alpha) and PPAR(beta/delta) attenuates the effects of distinct fatty acid species on metabolic gene expression in the mouse model.
4. Investigate the genetic background on endogenous supply of ornithine and the presentation of urea cycles disorders.
Understanding the Benefit of Fatty Acid Oxidation:
Children's Nutrition Research Center researchers have defined the response of adult heart muscle cells to fatty acids of distinct carbon chain length and saturation, at a molecular level. The findings suggest that the promotion of fatty acid oxidation may be protective for the heart. This is important since dyslipidemia (a disruption in the amount of lipids in the blood) is strongly associated with cardiovascular disease development, as observed in both obesity and diabetes mellitus. However, not all types of fatty acids are equal: certain fatty acids are cardioprotective and others are cardotoxic. These observations will help to improve scientists' understanding of the mechanisms responsible for cardiovascular disease development during dyslipidemic states. This in turn may influence dietary recommendations for cardiovascular disease prevention and treatment, as well as future pharmacological strategies. [NP107 - Component 6 Prevention of Obesity and Disease] (CNRC Project 3)
The Role of Cafestol in Cholesterol Metabolism:
Cafestol is a substance found in coffee that has been shown to impact cholesterol levels. Researchers at the Children's Nutrition Research Center completed their study of the role of cafestol in cholesterol regulation in the mouse model. Our lab previously found that cafestol binds to a specific receptor, the nuclear bile acid receptor, Farnesoid X receptor (FXR), but was unable to explain its apparently unusual effects on gene expression in the gut and the liver. Our lab showed that cafestol exerts its effects specifically in the gut, activating the expression of a hormonal growth factor, which acts on the liver to modify cholesterol metabolism. These results provide unexpected and important new insights into the mechanism of the effects of cafestol on cholesterol metabolism and, more generally, on the impact of dietary effects in the gut on whole body cholesterol homeostasis. [NP107 - Component 6 Prevention of Obesity and Disease] (CNRC Project 1)
The Role of the Circadian Clock in Bodyweight Control:
Children's Nutrition Research Center scientists found that the circadian genes affect body weight control in a gene-specific manner. This accomplishment is important since researchers can address how a specific behavioral pattern affects the energy balance and how specific disruption of a signaling pathway contribute to body weight control. Our studies have focused on analyzing the body weight of mice with different circadian gene-mutations and to identify clock-controlled genes that link cell metabolism and growth regulation together. Further studies in this direction could improve our understanding of the pathophysiology of metabolic syndrome and its related diseases, including aging and cancer. Our studies will also help us to suggest a healthy lifestyle to the public to reduce the burden of the current health-care system by disease prevention. [NP107 - Component 6 Prevention of Obesity and Disease] (CNRC Project 5)
Impact of Rates of Starch Digestion:
Starches are the main source of glucose in foods, but all starches are not equally digested. The nutritional importance of "resistant" and "slowly" digested starches (low glycemic) found in foods, as promoted on TV for weight reduction and preventing high blood glucose levels, is still unclear. As a result, Children's Nutrition Research Center scientists studied blood glucose metabolism to address the benefits of blocking experimental starch digestibility. We concluded that Mgam is the gate-keeping enzyme that determines rapid rates of small intestinal starch digestion, but this is suppressed during a large starch feeding, while the alternate small intestinal enzyme sucrase-isomaltase (Si) limits the rates of glucose production. We suggest that Mgam is the infant’s friend and Si the friend of the mature animal. Mgam is especially important at the time of weaning, when starches like rice cereals are first introduced in the infant’s diet, because of the human brain’s exclusive need for glucose as fuel. [NP107 - Component 2 Bioavailability of Nutrients and Food Components] (CNRC Project 2)
Interaction Between Mice Mutations and Genetics Yield Different Metabolic Phenotypes:
Scientists at the Children's Nutrition Research Center, Houston, TX, have established that a mutation in the urea cycle enzyme ornithine transcarbamylase interacts with the genetic makeup of mice to yield different metabolic phenotypes. Our lab addressed the complex interaction of specific mutations within a metabolic pathway with other parts of the pathway. This was accomplished by breeding the mouse mutation with two different genetic backgrounds. Stable isotope protocols were employed to study urea production, arginine fluxes, and nitric oxide production. This research is important since the impact of these studies is to understand the nutritional aspect of urea cycle disorders in humans, which affect newborns to adults and may lead to severe brain damage. [NP107 - Component 4 Nutrient Requirements] (CNRC Project 4)
|Number of non-peer reviewed presentations and proceedings||14|
|Number of newspaper articles and other presentations for non-science audiences||23|
Quezada-Calvillo, R., Robayo-Torres, C.C., Ao, Z., Hamaker, B.R., Quaroni, A., Brayer, G.D., Sterchi, E.E., Baker, S.S., Nichols, B.L. 2007. Luminal substrate "brake" on mucosal maltase-glucoamylase activity regulates total rate of starch digestion to glucose. Journal of Pediatric Gastroenterology and Nutrition. 45:32-43.
Robayo-Torres, C.C., Nichols, B.L. 2007. Molecular differentiation of congenital lactase deficiency from adult-type hypolactasia. Nutrition Reviews. 65:95-98.
Quezada-Calvillo, R., Robayo, C.C., Nichols, B.L. 2006. Carbohydrate digestion and absorption. In: Stipanuk, M.H., editor. Biochemical, Physiological, Molecular Aspects of Human Nutrition. 2nd edition. Philadelphia, PA: Saunders Elsevier. p. 168-199.
Gupte, S.A., Levine, R.J., Gupte, R.S., Young, M.E., Lionetti, V., Labinskyy, V., Floyd, B.C., Ojaimi, C., Bellomo, M., Wolin, M.S., Recchia, F.A. 2006. Glucose-6-phosphate dehydrogenase-derived NADPH fuels superoxide production in the failing heart. Journal of Molecular and Cellular Cardiology. 41:340-349.
Okere, I.C., Chandler, M.P., McElfresh, T.A., Rennison, J.H., Kung, T.A., Hoit, B.D., Ernsberger, P., Young, M.E., Stanley, W.C. 2007. Carnitine palmitoyl transferase-I inhibition is not associated with cardiac hypertrophy in rats fed a high fat diet. Clinical and Experimental Pharmacology and Physiology. 34:113-119.
Durgan, D.J., Smith, J.K., Hotze, M.A., Egbejimi, O., Cuthbert, K.D., Zaha, V.G., Dyck, J.R.B., Abel, E.D., Young, M.E. 2006. Distinct transcriptional regulation of long-chain acyl-CoA synthetase isoforms and cytosolic thioesterase 1 in the rodent heart by fatty acids and insulin. American Journal of Physiology - Heart and Circulatory Physiology. 290(6):H2480-H2497.
Robayo-Torres, C.C., Quezada-Calvillo, R., Nichols, B.L. 2006. Disaccharide digestion: Clinical and molecular aspects. Clinical Gastroenterology and Hepatology. 4(3):276-287.
Okere, I.C., Young, M.E., McElfresh, T.A., Chess, D.J., Sharov, V.G., Sabbah, H.N., Hoit, B.D., Ernsberger, P., Chandler, M.P., Stanley, W.C. 2006. Low carbohydrate/high-fat diet attenuates cardiac hypertrophy, remodeling, and altered gene expression in hypertension. Hypertension. 48:1116-1123.
Li, J., Coven, D.L., Miller, E.J., Hu, X., Young, M.E., Carling, D., Sinusas, A.J., Young, L.H. 2006. Activation of AMPK alpha and gamma-isoform complexes in the intact ischemic rat heart. American Journal of Physiology - Heart and Circulatory Physiology. 291:H1927-H1934.
Dyck, J.R.B., Hopkins, T.A., Bonnet, S., Michelakis, E.D., Young, M.E., Wantanabe, M., Kawase, Y., Jishage, K., Lopaschuk, G.D. 2006. Absence of malonyl coenzyme A decarboxylase in mice increases cardiac glucose oxidation and protects the heart from ischemic injury. Circulation. 114:1721-1728.
Morgan, E.E., Young, M.E., Mcelfresh, T.A., Kung, T.A., Hoit, B.D., Chandler, M.P., Stanley, W.C. 2006. Chronic treatment with trimethzidine reduces the upregulation of atrial natriuretic peptide in heart failure. Fundamental and Clinical Pharmacology. 20(5):503-505.
Nichols, B.L., Avery, S., Sen, P., Robayo, C., Quezada-Calvillo, R., Wattler, S., Nehls, M.C., Luginbuehl, U., Sterchi, E. 2006. Secreted maltase-glucoamylase is upregulated in membrane maltase-glucoamylase null mice. In: Naim HY, Zimmer KP, editors. The Brush Border Membrane: From Molecular Cell Biology to Clinical Pathology. Heilbronn, Germany: SPS Verlagsgesellschaft. p. 214-224.
King, K.L., Young, M.E., Kerner, J., Hanug, H., O'Shea, K.M., Alexson, S.E.H., Hoppel, C.L., Stanley, W.C. 2007. Diabetes or peroxisome proliferator-activated receptor alpha agonist increases mitochondrial thioesterase I activity in heart. Journal of Lipid Research. 48:1511-1517.
Young, M.E., Bray, M.S. 2007. Potential role for peripheral circadian clock dyssynchrony in the pathogenesis of cardiovascular dysfunction. Sleep Medicine. 8:656-667.
Chandler, M.P., Morgan, E.E., Mcelfresh, T.A., Kung, T.A., Rennison, J.H., Hoit, B.D., Young, M.E. 2007. Heart failure progression is accelerated following myocardial infarction in type II diabetic rats. American Journal of Physiology - Heart and Circulatory Physiology. 293(3):H1609-H1616.
Khairallah, M., Khairallah, R., Young, M.E., Dyck, J.R.B., Petrof, B.J., Des Rosiers, C. 2007. Metabolic and signaling alterations in dystrophin-deficient hearts precede overt cardiomyopathy. Journal of Molecular and Cellular Cardiology. 43:119-129.
Wilson, C.R., Tran, M.K., Salazar, K.L., Young, M.E., Taegtmeyer, H. 2007. Western diet, but not high fat diet, causes derangements of fatty acid metabolism and contractile dysfunction in the heart of Wistar rats. Biochemical Journal. 406(3):457-467.
Nichols, B.L. 2007. Indicators of normal carbohydrate digestion in children. Journal of Pediatric Gastroenterology and Nutrition. 45:176-177.
Morgan, E.E., Rennison, J.H., Young, M.E., McElfresh, T.A., Kung, T.A., Tserng, K.Y., Hoit, B.D., Stanley, W.C., Chandler, M.P. 2006. Effects of chronic activation of peroxisome proliferator-activated receptor-alpha or high-fat feeding in a rat infarct model of heart failure. American Journal of Physiology - Heart and Circulatory Physiology. 290(5):H1899-H1904.
Young, M.E. 2006. The circadian clock within the heart: potential influence on myocardial gene expression, metabolism, and function. American Journal of Physiology - Heart and Circulatory Physiology. 290(1):H1-H16.
Labinskyy, V., Bellomo, M., Chandler, M.P., Young, M.E., Lionetti, V., Qanud, K., Bigazzi, F., Sampietro, T., Stanley, W.C., Recchia, F.A. 2007. Chronic activation of peroxisome proliferator-activated receptor-alpha with fenofibrate prevents alterations in cardiac metabolic phenotype without changing the onset of decompensation in pacing-induced heart failure. Journal of Pharmacology and Experimental Therapeutics. 321(1):165-171.