Progress 05/15/07 to 02/28/10
Outputs
Progress Report Objectives (from AD-416) The specific objectives of this project are: 1) To determine the effects of selection of chickens for high and low body weight on the function and expression of specific genes regulating feed intake and energy balance, 2) To determine the relationship between high and low body weight phenotypes and the expression of genes encoding AMP-activated protein kinase (AMPK), and 3) To determine if selection for body weight has altered the brain's response to selected neurotransmitters, and to determine if such differences are due to a differential affect on the brain AMPK system. Approach (from AD-416) We will be testing the hypothesis that genetic selection for body weight results in changes in brain, and possibly peripheral, neurotransmitter and growth factor levels. Using a unique genetic line of birds that have been selected for over 45 generations for either high or low 8-week body weight, we will investigate how such selections have altered the brain mechanisms controlling food intake. This is the final report for this project. The purpose of this project was to determine how genetic selection for body weight in chickens influenced mechanisms that regulate feed intake and energy balance involving the energy-sensing enzyme AMP-activated protein kinase (AMPK). Work was conducted by ARS researchers at Beltsville, Maryland in collaboration with scientists at Virginia Polytechnic Institute and State University to determine the effects of selecting for body weight on: 1) expression of genes regulating feed intake and energy balance; 2) expression of genes encoding AMPK subunits and associated proteins; and 3) the brain�s response to modulators (neurotransmitters and hormones) that regulate feed intake via the AMPK system. There were significant effects caused by selection for body weight on the expression of the AMPK subunit genes in the brain (the central regulator of feed intake) as well as in two peripheral tissues that play important roles in regulating energy balance (liver and skeletal muscle). However, no differences were found in the expression of genes encoding the neuroendocrine factors neuropeptide Y (NPY) or proopiomeleanocortin (POMC) which play important roles in modulating brain neural circuits that regulate feed intake and energy expenditure. Expression of two genes encoding up-stream kinase enzymes that activate AMPK (LKB1 and CAMKK) was significantly up- regulated in the brains of chickens selected for low juvenile body weight indicating the potential for higher AMPK system activity in these birds. Two compounds known to influence AMPK activity, AICAR (an AMPK activator) and Compound C (an AMPK inhibitor) were tested by direct injection into the brain. AICAR caused a decrease in feed intake in birds selected for low body weight, whereas Compound C caused an increase in feed intake when injected into the brains of both high and low weight-selected birds. These results are completely opposite to what would be predicted from mammalian studies and indicate fundamental differences in the regulation of feed intake in birds. The hormone ghrelin was also tested and found to inhibit feed intake in both groups when administered into the brain. Again, this anorexigenic effect of ghrelin in chickens is completely opposite of that found in mammalian species. Other modulators including lipoic acid (an AMPK inhibitor), C75 (an AMPK activator), obestatin and glucagon-like peptide-1 were subsequently tested with respect to their effects on feed and water intake to further explore regulatory mechanisms in the chicken. The overall impact of these accomplishments is that new information is now available to poultry researchers and producers to determine how selection for body weight influences the central AMPK system that modulates feed intake and regulates energy balance. This work also suggests specific genes involved in controlling feed intake and body weight in chickens as potential candidates for marker-assisted selection of more efficient lines of poultry. Research progress was monitored via telephone and e-mail discussions and presentations at scientific conferences.
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) The specific objectives of this project are: 1) To determine the effects of selection of chickens for high and low body weight on the function and expression of specific genes regulating feed intake and energy balance, 2) To determine the relationship between high and low body weight phenotypes and the expression of genes encoding AMP-activated protein kinase (AMPK), and 3) To determine if selection for body weight has altered the brain's response to selected neurotransmitters, and to determine if such differences are due to a differential affect on the brain AMPK system. Approach (from AD-416) We will be testing the hypothesis that genetic selection for body weight results in changes in brain, and possibly peripheral, neurotransmitter and growth factor levels. Using a unique genetic line of birds that have been selected for over 45 generations for either high or low 8-week body weight, we will investigate how such selections have altered the brain mechanisms controlling food intake. Significant Activities that Support Special Target Populations Progress has been made by the Virginia Tech group this past year and work continues to characterize the effects of injection of a series of compounds (including hormones, neuropeptides and small molecules) into the canal system of the brain on food intake in two lines of chickens selected for high and low body weight gain at eight weeks of age. The responses of chickens to some of the compounds administered into the brain were found to be opposite to those reported for mammalian species indicating the potential for different mechanisms regulating food intake in birds versus mammals. This was found to be the case with ghrelin and obestatin, two peptide hormones produced by the stomach which affect appetite. Also, it was found that selection for eight-week body weight in chickens did alter the brain�s response to selected compounds known to influence food intake. These results will serve as a foundation for future experiments designed to identify and characterize the specific molecular components and mechanisms operating in the brain that regulate whole body energy balance and food intake.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) The specific objectives of this project are: 1) To determine the effects of selection of chickens for high and low body weight on the function and expression of specific genes regulating feed intake and energy balance, 2) To determine the relationship between high and low body weight phenotypes and the expression of genes encoding AMP-activated protein kinase (AMPK), and 3) To determine if selection for body weight has altered the brain's response to selected neurotransmitters, and to determine if such differences are due to a differential affect on the brain AMPK system. Approach (from AD-416) We will be testing the hypothesis that genetic selection for body weight results in changes in brain, and possibly peripheral, neurotransmitter and growth factor levels. Using a unique genetic line of birds that have been selected for over 45 generations for either high or low 8-week body weight, we will investigate how such selections have altered the brain mechanisms controlling food intake. Significant Activities that Support Special Target Populations Progress has been made by the Virginia Tech group this past year and work continues to characterize the effects of injection of a series of compounds (including hormones, neuropeptides and small molecules) into the canal system of the brain on food intake in two lines of chickens selected for high and low body weight gain at eight weeks of age. The responses of chickens to some of the compounds administered into the brain were found to be opposite to those reported for mammalian species indicating the potential for different mechanisms regulating food intake in birds versus mammals. Also, it was found that selection for eight- week body weight in chickens did alter the brain�s response to selected compounds known to influence food intake. These results will serve as a foundation for future experiments designed to identify and characterize the specific molecular components of mechanisms operating in the brain that regulate whole body energy balance and food intake. The accomplishments of this project relate to National Program 101 Food Animal Production Action Plan Component 2: Enhancing animal adaptation, well-being and efficiency in diverse production systems and Action Plan Problem Statement 2C: Improving efficiency of nutrient utilization and conversion to animal products.
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) The specific objectives of this project are: 1) To determine the effects of selection of chickens for high and low body weight on the function and expression of specific genes regulating feed intake and energy balance, 2) To determine the relationship between high and low body weight phenotypes and the expression of genes encoding AMP-activated protein kinase (AMPK), and 3) To determine if selection for body weight has altered the brain's response to selected neurotransmitters, and to determine if such differences are due to a differential affect on the brain AMPK system. Approach (from AD-416) We will be testing the hypothesis that genetic selection for body weight results in changes in brain, and possibly peripheral, neurotransmitter and growth factor levels. Using a unique genetic line of birds that have been selected for over 45 generations for either high or low 8-week body weight, we will investigate how such selections have altered the brain mechanisms controlling food intake. Significant Activities that Support Special Target Populations This reimbursable cooperative agreement between ARS and Virginia Polytechnic Institute and State University (VPI) was initiated on May 15, 2007 and is associated with project 1265-31000-087-00D. There is no progress to report at this time. Additional details of the research can be found in the report for the parent project 1265-31000-087-00D "Genetic Regulation of Feed Intake and Energy Balance in Poultry and Swine."
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