Faculty Research Summaries
Steven A. Abrams, M.D.
Dr. Abrams' research projects are designed to use stable isotopes
to evaluate mineral metabolism in infants and children. True dietary
calcium absorption and bone formation and turnover are determined
using orally and intravenously administered stable isotopes of calcium.
Studies in children with mineral deficiencies are designed to determine
the etiology of the mineral deficiency and the possible response
to therapy. Studies are under way to evaluate the absorption of
calcium and iron from milk, formula and dietary supplements in children
age 4-12 months. Studies are being conducted to determine the iron
needs of children with rheumatoid arthritis.
Janice Baranowski, M.P.H.,
Ms. Baranowski's recent research has focused on improving fruit
and vegetable consumption among children in a variety of settings
(school, Boy Scout troops). She is currently developing and testing
a computer-based food recording system and an interactive, multimedia,
fruit and vegetable dietary behavior change program with elementary
school children. A newly funded grant will involve translating
these successful methods into obesity prevention among children.
Tom Baranowski, Ph.D.
Dr. Baranowski is interested in three general topics: why
children eat the foods that they do; the design, implementation,
and evaluation of dietary and physical activity change programs;
and whether children's diet and physical activity practices become
adult practices (behavior tracking). Most of his research in the
last 10 years has focused on children's fruit, juice and vegetable
intake. Recent projects also focus on the prevention of childhood
obesity. The interventions have been school-based and with Boy Scouts.
Intervention modalities include classroom curriculum, interactive
multimedia games, the internet and video tapes. The intended outcome
of this work is the design of new public health programs effecting
positive changes in the dietary habits and physical activities of
Dennis M. Bier, M.D.
Dr. Bier's primary research interest is the regulation of interorgan
transport of metabolic fuels; specifically, substrate and
hormonal regulation of glucose, lipid, and protein/amino acid fuels.
This work has taken two principal directions. The first entails
the regulation of endogenous fuel availability for metabolic functions
when a subject is ill and incapable of ingesting sufficient food.
The second involves the assessment of the metabolic fates of ingested,
exogenous fuels under various classical nutritional circumstances.
In each instance, he has developed and employed a wide variety of
stable isotope tracer kinetic methods to quantify substrate flux,
metabolism, precursor-product relationships, and irreversible oxidation
to excreted end products. The physiological information obtained
also has been used to further assess aberrations in interorgan fuel
transport consequent to a variety of pathological conditions.
Douglas G. Burrin, Ph.D.
The research objectives in Dr. Burrin's laboratory are to elucidate
the cellular and hormonal signals that mediate the stimulatory effects
of enteral nutrition on the growth and function of the neonatal
intestine. Current studies are focused on the establishing the optimum
quantity and composition of enteral nutrients necessary to maintain
normal intestinal growth and function. He has found that the
secretion of gut-derived peptides, including glucagon-like peptide
2 (GLP-2), are closely correlated with enteral nutrient intake and
produce trophic effects when given to neonatal pigs. Future studies
will investigate the physiological significance of GLP-2 and how
it impacts intestinal protein and amino acid metabolism in a neonatal
Nancy F. Butte, Ph.D.
The energy requirements of reproductive women and their infants
are the focus of Dr. Butte's research. Her major interests are the
functional consequences of variations in energy balance on pregnancy
outcome, lactation performance, and infant growth and development.
To further these evaluations, methodologies have been developed
to measure energy expenditure and body composition in the populations
of interest, including room respiration calorimeters and the doubly
labeled water method for the measurement of free-living energy expenditure.
Factors which predispose women to postpartum weight retention and
later development of obesity are under investigation. Also, genetic
and environmental factors that predispose infants and children to
the development of obesity are being explored.
David M. Cohen, Ph.D.
Dr. Cohen's research concerns the regulated coordination of
metabolic fluxes that is fundamental to health and sustained by
adequate nutrition. Study of the quantitative relationships
among metabolic flux rates depends on accurate measurement of those
rates, preferably in vivo. To this end, he has investigated
mathematical aspects of modeling rates of metabolic pathways, subsequent
to the administration of isotopically labeled precursors.
An important focus of Dr. Cohen's work is the measurement of cerebral
metabolism in vivo, using nuclear magnetic resonance spectroscopy.
Currently, he is developing a new method for estimation of the rate
of cerebral glucose metabolism, with a substantial improvement in
time resolution. In the long term, he hopes to learn more about
the role of diet in support of brain metabolism and function.
Karen W. Cullen, Dr. P.H., R.D.,
Dr. Cullen's research focuses on improving fruit and vegetable consumption
and decreasing fat consumption among children and adolescents.
She has received funding to investigate social and environmental
influences on children's diets, children's goal-setting processes
for dietary behavior change, and the effect of school a la carte/snack
bars on the fruit, vegetable, and fat intakes of middle school children.
The results of these studies will be used to develop methods to
assist children with goal-setting procedures as part of dietary
behavior change programs; develop interventions to increase children's
fruit and vegetable consumption, both at school and home; and document
tracking of dietary behaviors among children.
Teresa A. Davis, Ph.D.
The goal of Dr. Davis' work is to determine the mechanisms by which
nutrients, hormones, and growth factors regulate the high rate of
muscle in the neonate. To achieve this objective, her research
focuses on four main areas: 1) the developmental changes in the
regulation of protein synthesis and degradation by insulin, 2) the
direct effect of amino acids on protein synthesis and their influence
on insulin-stimulated protein synthesis, 3) the interaction of insulin
and insulin-like growth factor-I in regulating protein turnover,
and 4) the role of insulin and insulin-like growth factor-I in the
anabolic response to growth hormone. To examine the effects of these
endocrine and metabolic factors on tissue and whole body protein
synthesis and degradation, stable isotopes and radioisotopes of
amino acids are used during in vivo infusion studies in growing
pigs. Novel techniques are being used which allow the active control
of many of the hormones and substrates which interact to regulate
protein anabolism. Identification of the signal transduction
proteins and translation initiation factors which regulate the high
growth rate of muscle is a primary goal of her current research.
Kenneth J. Ellis, Ph.D.
The goal of Dr. Ellis' research is to establish reference standards
for body elemental composition in infancy, childhood and adolescence.
This research focuses on the development and application of nuclearbased
techniques for in vivo studies of human body composition. This approach
provides knowledge of changes in growth and body composition that
reflect the body's cumulative response to basic physiologic and
metabolic processes. Detection of these changes often requires unique
instrumentation like the CNRC's whole body counters, which
monitor 40K, a naturally occurring isotope in the human.
Dr Ellis has developed in vivo neutron activation techniques for
clinical research and postmortem examinations, and he has extended
the use of dual-energy X-ray absorptiometry to the examination of
infants and children.
Marta Fiorotto, Ph.D.
The effects of chronic alterations in nutrient intake on the growth
and development of skeletal muscle are the focus of Dr. Fiorotto's
research. Currently, she is attempting to show that the nature
of skeletal muscle response is dependent on the developmental stage
at which the organism is subjected to a nutritional insult. She
is also attempting to identify the underlying factors responsible
for the agerelated change in the sensitivity of skeletal muscle
to nutritional perturbations. Dr. Fiorotto also will evaluate the
consequences of changes in sensitivity on the numerous functional
roles of skeletal muscle in the body.
Michael A. Grusak, Ph.D.
Dr. Grusak's laboratory is involved in both plant physiology and
human nutrition research. His plant physiology research is focused
on the mechanisms and regulation of nutrients in plants. His long-term
goals are to characterize the dynamics of nutrient flow within plants
to determine the biophysical/molecular signals which regulate source-to-sink
nutrient partitioning, and ultimately to use this information to
enhance the nutritional quality of plant foods. With regard to human
nutrition research, his laboratory group has developed hydroponic
growth facilities and protocols to label plant foods intrinsically
with stable isotopes of important nutrients; these then are used
to assess nutrient bioavailability and metabolism in humans.
Darryl L. Hadsell, Ph.D.
Current evidence supports the idea that insulin-gene family members
are necessary for all aspects of mammary gland development and lactation.
Despite this, the mechanisms by which these peptides regulate mammary
gland function are poorly understood. Research within Dr. Hadsell's
laboratory focuses on three main goals. The first is to understand
the specific mechanisms through which the receptors for insulin
(IR) or IGF-I (IGF-IR) influence mammary gland development and/or
lactation. The second is to understand the mechanisms through which
nutrient availability influences mammary gland development and/or
lactation. The last is to understand how these factors interact
at the transcriptional level to allow normal mammary gland development
and lactation. The combined use of transgenic and knockout mice,
tissue grafting strategies, and in-vitro cell culture models to
modify IR or IGF-IR activity has provided insights into the mechanism
through which apoptosis is regulated within the mammary gland.
These strategies have also led to a focus on putative insulin-responsive
transcription factors as a means to define insulin-dependent milk
protein gene expression
Peter M. Haney, M.D., Ph.D.
Dr. Haney's long-term research goal is to understand the molecular
cell biology of lactation. Human milk is recognized as the ideal
source of nutrition for infants, but the mechanisms and regulation
of milk secretion are poorly understood at the cellular and molecular
level. Current work is focused on glucose transport in the lactating
mammary gland. Dr. Haney is studying the regulation of the amount,
activity, and subcellular targeting of GLUT1, the only glucose transporter
isoform identified in the mammary gland, in established and primary
mammary epithelial cell lines, as well as in humans and rodents.
Efforts are under way to elucidate the mechanisms of altered glucose
transporter targeting, including Golgi sequestration and polarization
of plasma membrane distribution, that he has observed during lactation.
He will examine how GLUT1 gene expression and subcellular targeting
regulate the synthesis of lactose. Dr. Haney has observed a novel
protein, structurally similar to GLUT1, that resides in the Golgi,
and is expressed only during lactation. He is pursuing the purification
of this protein, the cloning of its cDNA, and the characterization
of its possible role in regulating the targeting of GLUT1.
Morey W. Haymond, M.D.
The focus of Dr. Haymond's research program is to delineate and
ultimately manipulate the hormone and substrate factors that regulate
the absorption, assimilation, mobilization and disposal of carbohydrates
in infants and children. The delicate balance of nutrient availability
to meet the energy and growth needs of children is frequently disturbed
as a result of chronic disease, infection, trauma and/or organ failure.
In addition, the incidence of both type I and type II diabetes is
on the rise, providing unique opportunities to study the effects
of insulin, insulin resistance and obesity on macronutrient assimilation
in children. These issues are being addressed in infants, children,
adults, and when necessary, in animals, using a variety of stable
isotope tracer techniques to estimate insulin sensitivity, absorption
of carbohydrates, proteolysis, protein synthesis, gluconeogenesis,
carbohydrate disposal, and substrate oxidation. Dr. Haymond is currently
studying the impact of diet composition (fat and carbohydrate) on
glucose homeostasis and macronutrient assertion; the impact of lactation
production on glucose homeostasis in women; the precursors for lactose
production and the factor(s) that regulate it; and the regulation
of galactose and fructose metabolism by the liver.
William C. Heird, M.D.
Dr. Heird's research concerns specific fatty acid and amino acid
needs of infants. Clinical studies of fatty acid needs focus
on the effect of 3 vs. 6 fatty acids on energy balance and the mechanism(s)
by which these two families of fatty acids exert effects.
Concurrent studies in animals focus on the effects of specific 6
and/or 3 fatty acids on cellular and molecular events controlling
nutrient utilization and, hence, energy balance. Clinical studies
of amino acid needs focus on the role of aromatic amino acids in
supporting the acute-phase protein response of various groups of
stressed infants. The need for tyrosine, particularly by infants
who require parenteral nutrition, is of specific interest. Studies
of fatty acid needs are being conducted collaboratively with Dr.
Craig L. Jensen of the CNRC and Dr. Steven D. Clarke of the University
of Texas at Austin. Those studies concerning amino acid needs are
being conducted collaboratively with Dr. Farook Jahoor of the CNRC.
Karen Hirschi, Ph.D.
Blood vessel formation is essential for normal growth and development.
It plays a central role in the progression of prevalent pathologies
including atherosclerosis, tumor angiogenesis and diabetic retinopathy.
Dr. Karen Hirschi is interested in understanding how blood vessels
are assembled, elucidating the regulators of cellular recruitment,
proliferation and differentiation needed for vessel formation and
maintenance, and exploring the role of such effectors in prevention
and treatment of vascular pathologies. She is specifically
interested in elucidating the role of nutrients in the direct modulation
of vascular cell growth and mural cell differentiation via cell
cycle-associated, and mural-cell-specific, gene regulation.
She is also interested in the indirect modulation of vascular cell
differentiation and growth via nutrient regulation of cell-cell
junctional components such as extracellular matrix and gap junctions.These
issues are being addressed using novel in vitro coculture systems,
murine embryo culture, and transgenic mouse models.
Kendal Hirschi, Ph.D.
Unable to flee when challenged by an environmental threat, plants
must adapt by altering their physiology. Calcium ions play a central
signaling role in the cascade of events that empower plant cells
to initiate these responses. Dr. Kendal Hirschi has utilized mutants
in budding yeast to isolate plant genes that regulate intracellular
calcium levels. Future work in his lab will be directed toward molecular
and genetic approaches to study calcium transport and signaling
in the model plant Arabidopsis thaliana.
Judy A. Hopkinson, Ph.D.
Dr. Hopkinson's research is focused on body composition changes
during reproduction, and the effects of those changes on pregnancy
outcome, lactation performance, and maternal weight retention. Maternal
energy balance is computed from measures of food intake, energy
expenditure, energy deposition during pregnancy, and milk production
during lactation. Maternal body composition changes are monitored
for 2 years postpartum. Dr. Hopkinson continues to study maternal
factors that influence milk production and composition: preterm
delivery, frequency of nursing, smoking, and alcohol consumption.
Kazumi Ishimura-Oka, M.D.
Dr. Ishimura-Oka's major interest is lipoprotein metabolism. She
has recently generated transgenic mice which express lipoprotein
lipase (LPL), a pivotal enzyme of lipoprotein metabolism. In this
animal model, LPL is expressed only in adipose tissue. Using this
animal model, her laboratory will determine the tissue-specific
effects of LPL in lipid metabolism with regard to metabolic disorders
such as obesity, atherosclerosis and non-insulin-dependent diabetes
Farook Jahoor, Ph.D.
Dr. Jahoor's research focuses on the intermediary metabolism of
macronutrient fuels. One area of primary interest is the altered
metabolic response to the stress of infections, and its impact on
nutritional requirements during early growth and development. Studies
are being performed in both animals and humans to determine how
stress alters protein (and specific amino acids), carbohydrate and
lipid metabolism. Another area of research looks at how the
production of antioxidants and proteins involved in the immune response
is affected by conditions such as protein-energy malnutrition, HIV
infection, aging and diabetes mellitus. Specific studies focus on
the metabolism of glutathione, cysteine, acute-phase proteins and
nitric oxide. Stress-induced changes in the partitioning of nitrogen
for the synthesis of muscle proteins, acute-phase proteins and nutrient
transport proteins are also being investigated. Dr. Jahoor is also
involved in the development and use of different stable isotope
tracer methodologies to investigate intermediary metabolism.
Craig L. Jensen, M.D.
Dr. Jensen's research is directed toward determining the optimal
intakes of polyunsaturated fatty acids for term and preterm infants.
The ability of infants to synthesize longer-chain n-3 and n-6 polyunsaturated
fatty acids from their precursors, -linolenic and linoleic
acids, respectively, is being investigated using stable isotope
techniques. The effects of different dietary intakes of essential
fatty acids on biochemical and functional outcomes in both term
and preterm infants are being assessed.