Progress 08/01/99 to 07/31/04
Outputs
Poultry livers make a unique class of triglyceride-rich, apolipoprotein B-containing lipoproteins specifically for yolk formation called VLDLy. VLDLy are smaller than generic VLDL that provide the hen with energy, and VLDLy triglyceride-energy is less available to the hen's body. This project seeks to understand how VLDLy are made and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos. We have reported the results of a number of studies related to factors that affect production of VLDLy, such as: age of the hen, molt, and genetic variation. The process of VLDLy assembly is being studied in collaboration with Dr. Robert Hamilton. An exciting discovery of those experiments is that renal proximal tubule cells in birds assemble VLDL with diameters of - 60nm. This process may act to conserve fatty acids, and may support maternal lipid needs during the time that the liver produces
VLDLy directed at yolk production. Hens that go out of lay lose the capacity to produce VLDLy in the liver, but this loss is coupled with the appearance of a special lipoprotein, called HDLR, which appears to be produced to reabsorb yolk material from the regressing follicles in the ovary. Attempts to sequence a special protein in HDLR were made, but insufficient protein was available to obtain reliable results. IMPACT: 1999/01 TO 1999/12 Poultry livers make a unique class of triglyceride-rich, apolipoprotein B-containing lipoproteins specifically for yolk formation called VLDLy. VLDLy are smaller than generic VLDL that provide the hen with energy, and VLDLy triglyceride-energy is less available to the hen's body. This project seeks to understand how VLDLy are made and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos. We have reported the results of a number of studies related to factors
that affect production of VLDLy, such as: age of the hen, molt, and genetic variation. The process of VLDLy assembly is being studied in collaboration with Dr. Robert Hamilton. An exciting discovery of those experiments is that renal proximal tubule cells in birds assemble VLDL with diameters of - 60nm. This process may act to conserve fatty acids, and may support maternal lipid needs during the time that the liver produces VLDLy directed at yolk production. Hens that go out of lay lose the capacity to produce VLDLy in the liver, but this loss is coupled with the appearance of a special lipoprotein, called HDLR, which appears to be produced to reabsorb yolk material from the regressing follicles in the ovary. Attempts to sequence a special protein in HDLR were made, but insufficient protein was available to obtain reliable results.
Impacts
This project sought to understand how VLDLy are made and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos.
Publications
- Elkin, R.G., R.E. Porter Jr, Y. Zhong, C. Agca, R. Meunier, M.A. Latour, S.L. Neuman and R.L. Walzem. 2000. Modification and complete validation of a polymerase chain reaction-based method for identifying mutant restricted ovulator chickens. XXI World's Poultry Congress (Abstract in World's Poultry Science).
- Walzem, R.L. 2000. Yolk Formation and Nutritional Content. Presented at the VII International Symposium on Avian Endocrinology, January 28-February 2 at Varanasi, India.
- Walzem, R.L., G. Brower, and R.J. Hansen. 2000. Plasma lipoprotein profiles during a complete egg laying cycle (Abstract submitted to Poultry Science Association).
- Walzem, R.L. and R.L. Hamilton. 1999. Introductory Comments. Assembly and physiology of apolipoprotein B containing lipoproteins: not just for heart disease anymore. J. Nutrition, 129:449S-4505.
- Walzem, R. L. , R. J. Hansen, D. L. Williams and R. L. Hamilton. 1999. Estrogen induction of VLDLy assembly in egg-laying hens. Journal of Nutrition 129:467S-472S.
- Barron, L.G., R.L. Walzem and R.J. Hansen. 1999. Plasma lipoprotein changes in hens (Gallus domesticus) during an induced molt. Comparative Biochemistry and Physiology, Part B 123:9-16.
- Chen, S.-E., D.W. Long, K.E. Nestor, R.L. Walzem, V.L. Meuniot, H. Zhu, R.J. Hansen, and W.L. Bacon. 1999. Effect of divergent selection for total plasma phosphorus on plasma and yolk very low density lipoproteins and plasma concentrations of selected hormones in laying Japanese quail. Poultry Sci. 78:1241-1251.
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Progress 01/01/99 to 12/31/99
Outputs
Poultry livers make a unique class of triglyceride-rich, apolipoprotein B-containing lipoproteins specifically for yolk formation called VLDLy. VLDLy are smaller than generic VLDL that provide the hen with energy, and VLDLy triglyceride-energy is less available to the hen's body. This project seeks to understand how VLDLy are made and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos. We have reported the results of a number of studies related to factors that affect production of VLDLy, such as: age of the hen, molt, and genetic variation. The process of VLDLy assembly is being studied in collaboration with Dr. Robert Hamilton. An exciting discovery of those experiments is that renal proximal tubule cells in birds assemble VLDL with diameters of - 60nm. This process may act to conserve fatty acids, and may support maternal lipid needs during the time that the liver produces
VLDLy directed at yolk production. Hens that go out of lay lose the capacity to produce VLDLy in the liver, but this loss is coupled with the appearance of a special lipoprotein, called HDLR, which appears to be produced to reabsorb yolk material from the regressing follicles in the ovary. Attempts to sequence a special protein in HDLR were made, but insufficient protein was available to obtain reliable results.
Impacts
This project seeks to understand how VLDLy are made and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos.
Publications
- Walzem, R.L. and R.L. Hamilton. 1999. Introductory Comments. Assembly and physiology of apolipoprotein B containing lipoproteins: not just for heart disease anymore. J. Nutrition, 129:449S-4505.
- Walzem, R. L. , R. J. Hansen, D. L. Williams and R. L. Hamilton. 1999. Estrogen induction of VLDLy assembly in egg-laying hens. Journal of Nutrition 129:467S-472S.
- Barron, L.G., R.L. Walzem and R.J. Hansen. 1999. Plasma lipoprotein changes in hens (Gallus domesticus) during an induced molt. Comparative Biochemistry and Physiology, Part B 123:9-16.
- Chen, S.-E., D.W. Long, K.E. Nestor, R.L. Walzem, V.L. Meuniot, H. Zhu, R.J. Hansen, and W.L. Bacon. 1999. Effect of divergent selection for total plasma phosphorus on plasma and yolk very low density lipoproteins and plasma concentrations of selected hormones in laying Japanese quail. Poultry Sci. 78:1241-1251.
- Elkin, R.G., R.E. Porter Jr, Y. Zhong, C. Agca, R. Meunier, M.A. Latour, S.L. Neuman and R.L. Walzem. 2000. Modification and complete validation of a polymerase chain reaction-based method for identifying mutant restricted ovulator chickens. XXI World's Poultry Congress (Abstract in World's Poultry Science).
- Walzem, R.L. 2000. Yolk Formation and Nutritional Content. Presented at the VII International Symposium on Avian Endocrinology, January 28-February 2 at Varanasi, India.
- Walzem, R.L., G. Brower, and R.J. Hansen. 2000. Plasma lipoprotein profiles during a complete egg laying cycle (Abstract submitted to Poultry Science Association).
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Progress 01/01/98 to 12/31/98
Outputs
Lipoproteins transport lipids and lipophilic nutrients (such as Vitamin E) within the body. Poultry make a unique class of trig lyceride-rich, apolipoprotein B (apoB)-containing lipoproteins specifically for yolk formation called VLDLy. VLDLy are smaller than generic VLDL that provide the hen with energy, and VLDLy trig lyceride-energy is less available to the hen. This project seeks to understand how VLDLy are made, and how the physical differences between generic VLDL and VLDLy cause selective nutrient partitioning towards yolk formation and, ultimately, embryos. We use a laser-based method to rapidly and accurately measure the size characteristics of VLDL and VLDLy in large numbers of samples. Comparative studies with genetically-engineered mice and rat arterial preparations showed that both apoB genotype and oxidative stress can alter circulating VLDL diameter.
Impacts
(N/A)
Publications
- VENIANT, M.M., C.H. ZLOT, R.L. WALZEM, V. PIEROTTI, R. DRISCOLL, D. DICHECK, J. HERZ and S.G. YOUNG. 1998 Liproprotein clearance mechanisms in LDL receptor-deficient 'ApoB48-only' and 'ApoB100-only' mice. Journal of Clinical Investigation. 102: 1559-1568.
- WALZEM, R.L., R. J. HANSEN, D. L. WILLIAMS and R. L. HAMILTON. 1999. Estrogen induction of VLDLy assembly in egg-laying hens. In: Assembly and secretion of apolipoprotein B containing lipoproteins: Not just for heart disease anymore!, Journal of Nutrition 129S: (in press)
- BARRON, L.G., R.L. WALZEM and R.J. HANSEN. 1999. Plasma lipoprotein changes during molting in hens (Gallus domesticus). Comparative Biochemistry and Physiology, Part B. (in press)
- WALSH, B.A., A.E. MULLICK, R.L. WALZEM, and J.C. RUTLEDGE. 1999.17-b estradiol reduces tumor necrosis factor-a-mediated LDL accumulation in the artery wall. Journal of Lipid Research,(in press)
- BOYLE-RODEN, E. and R.L. WALZEM. 1998. Novel strategy to enrich native lipoproteins with 13C lipids. Poster presented at Gordon Conference on Lipoprotein Metabolism, June 28-July 3, Kimball Union Academy, Meriden, New Hampshire.
- MacDOUGALL, E. D., R.L. WALZEM, and K. C. KLASING. 1999. Leukocytes are present during the clearance of yolk from the abdominal cavity of hens. FASEB J. (Abstract to EB '99)
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Progress 01/01/97 to 12/31/97
Outputs
Poultry assemble a unique class of triglyceride-rich lipoproteins, called VLDLy, to specifically transport lipids and lipophilic nutrients to forming egg yolks. VLDLy particles are smaller and more resistant to lipases than VLDL made by non-laying hens and roosters. We seek to determine how VLDLy are made, and how the physical differences between VLDL and VLDLy cause selective nutrient partitioning towards yolk, and subsequently embryos. Methods needed to be developed to test the hypothesis that ideal VLDLy are uniform in size, lipase resistance and nutrient composition. Correlate hypotheses: 1) VLDLy synthetic capacity influences reproductive efficiency in hens; 2) VLDLy nutrient composition varies with maternal nutriture, and 3) imbalanced lipoprotein metabolism causes disease. Method 1: to study lipase resistance, carbonyl moieties of VLDLy triglycerides were selectively enriched with the stable isotope 13C, in order to be visualized by nuclear magnetic resonance
(NMR) imaging. Method 2: to study how VLDLy are assembled, individual parts of liver cells and their content assembly intermediates were isolated and partially characterized. A separate method was developed to perfuse intact livers at various stages of VLDLy assembly in order to view assembly processes in the liver cell by electron microscopy. Method 3: to study molecular events of VLDLy assembly, stably transformed cell lines were created to test the role of apo-VLDL-II in controlling VLDLy=s particle size.
Impacts
(N/A)
Publications
- XU, R., YOKOYAMA, W.H., IRVING, D., REIN, D., WALZEM, R. L., and GERMAN J.B. 1997. Effect of dietary catechin and vitamin E on aortic lipid accumulation in hypercholesterolemic hamsters. Atherosclerosis
- REIN, D., YOKOYAMA, W.H., XU, R., WALZEM, R. L., and GERMAN, J.B. German. 1997. Dietary vitamin E in an atherogenic hamster model. Nutrition Research (Accepted)
- American Heart Association, Grant-in-Aid. California Affiliate (1997-1999). AVLDLy Assembly in Hepatocytes of Estrogenized Chicks.@ Funded for $100,000. Robert L. Hamilton Co-principal investigator.
- American Heart Association, Grant-in-Aid. Maryland Affiliate (1995-1996). AUse of 13C NMR to Determine Specific Surface Lipid Composition Correlation with Lipolysis of VLDL.@ Funded for $21,980. Elizabeth Boyle Co-principal investigator.
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Progress 01/01/96 to 12/30/96
Outputs
We have been studying the role of very low density lipoprotein (VLDL) structure and composition in yolk formation. An opportunity to study VLDL properties in quail by collaborating with Dr. Wayne Bacon, at Ohio State University, Wooster, developed subsequent to submitting last year's LDRL proposal. Quail are another commercially-used oviparous species whose size, life span and reproductive capacities lend themselves to rapid genetic selection. Dr. Bacon has bred selected strains of Coturnix for high and low blood VLDL lipid levels for over 30 generations. He provided plasma from 30 hens for each of 3 lines of quail he selected to differ in plasma total phosphorous during yolk formation. In these lines, plasma total phosphorous is highly correlated with total plasma lipids, including VLDL triglyceride. The VLDLy particle size distributions were measured for each of 30 hens from high-phosphorous (HP), low-phosphorous (LP) and random-bred control (RB) lines using a
dynamic laser light scattering technique we developed for this purpose. Comparisons were made using an unpaired "t" test", and p<0.05 was considered significant. All groups of hens laid an average of 6 eggs during each 7-day period (86%) preceding and following blood sampling. Plasma VLDL were isolated as the d < 1.02 g/mL fraction of plasma by density gradient ultracentrifugation. The diameters of VLDL particles from quail hens expressed as an area distribution averaged 39 nm, which are substantially larger than those of chickens or tu.
Impacts
(N/A)
Publications
- There were no publications during this reporting period.
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Progress 01/01/95 to 12/30/95
Outputs
The purpose of these studies was to develop methods for separation and analysis of lipoproteins from the plasma of laying hens. The size distribution of triglyceride-rich very low density lipoprotein (VLDL) is an important factor in a hen's ability to lay eggs. Hens must deposit large amounts of triglyceride into egg yolks each day in order to continue laying eggs. Hens that are able to make VLDL that are 25-40 nm in diameter usually lay more eggs than hens that make VLDL that are larger or smaller than this optimal size range. VLDL within this optimal diameter seem to be used preferentially for yolk formation. This specific association with yolk deposition is indicated by the abbreviation of VLDLy. Our goal is to determine the basis for the special association between VLDLy and yolk formation. Part of the selectivity is based on the ability of the ovary to prevent VLDL larger than 46 nm from entering the yolk follicle. This mechanical size exclusion does not explain
why VLDL smaller than 25 nm are also associated with decreased egg production. Other possible reasons include direct failure to interact with the ovarian receptor that deposits VLDL into the growing yolk follicle, and alternative metabolism by peripheral tissues. To test possible mechanisms, mixed populations of VLDL, ranging in size from 20 - 150 nm must first be separated into discrete size subclasses for chemical and metabolic characterization. This objective was accomplished by the method of size exclusion chromatography.
Impacts
(N/A)
Publications
- MEUNOIT, V.L., HANSEN, R.J. and WALZEM, R.L. 1996. Storage conditions affect observed size distributions of very low density lipoproteins (VLDL). FASEB J. 10: A4326.
- GERMAN, J.B., XU, R., WALZEM, R.L., KINSELLA, J.E., KNUCKELS, B., NAKAMURA, M. and YOKOYAMA, W.H.. 1996, Fiber lowers total cholesterol but not lipoprotein remodeling in the hamster. Nutrition Research, (Accepted).
- GERMAN, J.B., XU, R., WALZEM, R.L., KINSELLA, J.E., KNUCKELS, B. and YOKOYAMA, W.H. . 1995. Fiber lowers total cholesterol but not lipoprotein remodeling in diet-induced hypercholesterolemia in the hamster. FASEB J. 9: A768.
- XU, R., YOKOYAMA, W.H., HUDSON, C.A., WALZEM, R., HANSEN, R.J. and GERMAN, J.B. 1995. Gender response to dietary induced lipoprotein changes in the hamster. FASEB J. 9: A4453.
- YOKOYAMA, W.H., WALZEM, R., XU, R. and GERMAN, J.B.. 1994. Lipoprotein cholesterol analysis by size exclusion chromatography: comparison with sequential equilibrium density ultracentrifugation. FASEB J. 8: A2602.
- BURNS, L.C., HANSEN, R.J., and WALZEM, R.L. 1996. Separation of size subclasses of laying hen very low density lipoprotein (VLDL) by FPLC. FASEB J. 10: A4325.
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Progress 01/01/93 to 12/30/93
Outputs
An overfed-hen model was shown to mimic much of the pathology of spontaneous Fatty Liver Hemorrhagic Syndrome including distinctive changes in the protein fibers (reticulin) which confer structural integrity to the liver. Reproductive dysfunction and frank involution of the reproductive tract was demonstrated in greater than 30% of hens studied. Evidence of reproductive dysfunction included erratic oviposition, double ovulations, laying of soft or incompletely shelled or shell-less eggs as well as cessation of egg production. Follicle populations of overfed, erratically laying hens showed an increase the total number of yolks within the yellow hierarchy and an increase in the number of small white follicles. Thus fatty liver hemorrhagic syndrome is an extreme example of the detrimental effects that excess energy intake has on the reproductive performance of female avians. Many of the detrimental effects of energy excess were mediated by changes in plasma lipoprotein
functional properties which resulted in a redirection of hepatic lipoprotein away from deposition into yolk and towards deposition into adipose. The changes observed in the density distribution and chemical composition of plasma lipoproteins suggest that continued yolk deposition in the face of increasing energy intakes depends upon the liver's ability to synthesize very low density lipoprotein (VLDL) with the requisite physical and functional properties. Synthesis of VLDL suitable for yolk deposition depends largely upon estrogen p.
Impacts
(N/A)
Publications
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Progress 01/01/92 to 12/30/92
Outputs
Previous work has shown that some overfed Single Comb White Leghorn (SCWL) hens experience reproductive failure and follicular involution. Such hens develop a unique 20nm high density lipoprotein (HDL(subscript R)). Three studies were conducted to study frequency of particle formation in situations of reproductive failure. 1). 15% of 34 wk old broiler breeder hens, fed ad libitum; and 2.5% of feed restricted broiler breeder hens, experienced ovarian regression. 80% of poorly laying ad lib fed, and 20% of poorly laying restricted fed hens were found to have HDL(subscript R) in plasma, 2). SCWL hens were force-molted by either deprivation of light and feed, or prolactin injection. Both groups of hens exhibited HDL(subscript R) in plasma 2-4 days following cessation of egg production, 3). SCWL hens were overfed to achieve 150% of their usual daily feed consumption. Particle diameters of very low density lipoproteins (VLDL) were measured by low-angle laser light
scattering. Mean VLDL diameter prior to overfeeding was 28nm. Average VLDL diameter increased to 40.3nm with overfeeding. VLDL diameters ranged from 28 - 65nm. Others have reported that VLDL larger than 46nm do not penetrate the basal lamina of the oocyte. In our study, the percentage of VLDL with diameters larger than 46nm increased from 16% to 32% in overfeeding. In hens undergoing follicular collapse, the percentage of VLDL larger than 46nm was 76%.
Impacts
(N/A)
Publications
- BARRON, L., WALZEM, R.L. and HANSEN, R.J. 1992. Appearance of a novel lipoprotein in plasma of force-molted Single Comb White Leghorn (SCWL) hens. FASEB J. 6:A1390 (#2629).
- WALZEM, R.L., ROBINSON, F.E., YU, M.W. and HANSEN R.J. 1992. Broiler-breeder hen plasma lipoprotein size distributions are affected by feed restriction and egg production. FASEB J. 6:A1390(#2630).
- HANSEN, R.J. and WALZEM, R.L. 1993. Avian fatty liver hemorrhagic syndrome: A comparative review. Advan. Vet. Sci. and Comp. Med. (in-press).
- WALZEM, R.L., SIMON, C., MORISHITA, T., LOWENSTINE, L. and HANSEN, R.J. 1993. Fatty liver hemorrhagic syndrome in hens overfed a purified diet. Selected enzyme activities and liver histology in relation to liver hemorrhage and reproductive.
- BARRON, L. 1993. Effect of Two Methods of Force-Molting on Lipoprotein Profiles of Single Comb White Leghorn Hens. M.S. Thesis.
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Progress 01/01/91 to 12/30/91
Outputs
Previous work from this laboratory had demonstrated the appearance of a novel 19-21mm HDL particle associated with involution and cessation of egg production in layers overfed a purified diet. To determine if the appearance of this particle was specific to overfeeding or some general phenomenon related to involution, laying hens were force-molted. Using a method in common usage in industry, hens were subjected to light deprivation and starvation. Blood samples were obtained prior to the start of the experiment and daily thereafter for 7 days. Plasma lipoproteins were separated by density gradient centrifugation. VLDL, LDL, and HDL fractions analyzed chemically for triacylglycerides (TAG), protein, phospholipids and cholesterol and electrophoretically to determine particle sizes and numbers. An initial experiment has been performed and a subsequent one is currently underway. Chemical analyses of the 3 lipoprotein fractions show the following: 1) as expected, total
plasma TAG decreased when food was withdrawn and light was reduced; 2) VLDL TAG decreased with starvation, but DHL and LDL TAG were increased as starvation progressed; and 3) total plasma and VLDL cholesterol decreased with starvation but HDL cholesterol increased. Gradient gel electrophoresis of HDL and LDL proteins demonstrated the presence of the novel 19-21nm particle that had been observed in overfed hens, indicating that the particle is associated with follicular involution rather than overfeeding.
Impacts
(N/A)
Publications
- NO PUBLICATIONS REPORTED THIS PERIOD.
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