National Institute on Alcohol Abuse and
Overview of NIAAA Rare Diseases in Children Research
Activities, FY 2000FY 2005
The mission of NIAAA is to conduct and support research activities
on the causes, consequences, and treatment of alcoholism and
alcohol abuse. Alcoholism results in widespread and damaging
consequences to the health of children, both psychologically
in child abuse and neglect and physically in mental retardation
and birth defects associated with fetal alcohol syndrome (FAS).
Please see "Ongoing, New, and Planned Research Initiatives"
for more information. In terms of funding, many NIAAA FAS
studies are funded through FY 2004. Funding for research on
other diseases and conditions discussed in this report is
assured, although specifics in terms of funding allocation
are linked to progress and Principal Investigator evaluation
of scientific merit.
Recent Scientific Advances in Rare Diseases Research
Relevant to Children
Friedreich's Ataxia (FRDA)
FRDA is an autosomal recessive disease clinically
characterized by progressive ataxia, hypertrophic cardiomyopathy,
early onset of insulin-resistant diabetes, invalidism, and
premature death. Current therapy for FRDA is palliative.
FRDA is caused by a deficiency of frataxin, a 210 amino
acid nuclear-encoded mitochondrial protein, resulting from
the expansion of an intronic GAA repeat that leads to inhibition
of transcription in the nucleus, leading to decreased message.
In yeast, frataxin appears to be involved in iron export from
mitochondria. In experiments, yeast cells with deleted frataxin
accumulated mitochondrial iron, showed a high sensitivity
to oxidation damage, and showed decreased mitochondrial respiration.
In human cells, however, FRDA patients show a decrease
in activity of the mitochondrial enzyme aconitase (EC 126.96.36.199),
the enzyme responsible for conversion of citrate to isocitrate,
the first step in the Krebs (also known as citric acid or
TCA) cycle. Over-expression of frataxin in mammalian cells
results in increases in the flux through the TCA cycle, in
the electric potential between mitochondria and cytoplasm,
and in the cellular adenosine triphosphate (ATP) content.
These findings in mammalian cells indicate that deficiency
of frataxin in human patients results primarily from defects
in the TCA cycle and not from mitochondrial iron overload.
The clinical phenotype of FRDA patients is indistinguishable
from the phenotype of patients with familial -tocopherol (vitamin
E) deficiency, and is different from patients with iron overload.
Recent work shows that elevation of blood ketone bodies, a
normal response to fasting, can increase mitochondrial citrate
and isocitrate contents, thus overcoming the block in aconitase
found in FRDA. In addition, ketone bodies increase
the electric potential between mitochondria and cytoplasm,
and with that, the energy contained in ATP. At the same time,
ketone bodies oxidize coenzyme Q, thus decreasing the major
source of mitochondrial free radicals. Ketone bodies also
reduce the free NADP + ,which is the major source of the detoxification
of free radicals. It is proposed that a diet containing ketone
bodies might prove an effective therapy for this currently
untreatable disease. Such dietary therapy could provide an
earlier treatment for this group of patients than attempting
to transfect the gene for frataxin into heart, muscle, and
GLUT1 is the enzyme responsible for the transport
of glucose from blood into the brain across the blood-brain
barrier. The activity of this enzyme is not responsive to
insulin. GLUT1-deficient epilepsy results from several
types of mutation in the gene of GLUT1, located on
the short arm of chromosome 1. The phenotypic expression of
this mutation is infantile seizures (often refractory to anti-epileptic
medication), delay of development, and acquired microcephaly
with subsequent mental retardation. Under most conditions,
the brain is entirely dependent upon blood glucose for all
its energy needs; however, ketone bodies can provide a source
of energy that can enter the cell on its own transporter,
which differs from the glucose transporter. With the transport
of glucose blocked as it is in these patients, ketone bodies
provide the only physiologically normal alternative nutrient
for the brain. Administering a diet rich in ketone bodies
can provide a way to maintain normal brain growth and development
and reduce or eliminate seizures. Feeding high-fat diets,
the normal procedure for the treatment of drug-resistant epilepsy,
can lead to elevation of blood cholesterol with consequently
accelerated atherosclerosis. Therefore, a high-fat diet cannot
be continued past age 17. A diet high in ketone bodies cannot
lead to increased cholesterol synthesis, because ketone bodies
are not utilized by the liver (the source of cholesterol synthesis).
High-ketone diet therapy may therefore become a practical
method for lifelong treatment of these patients.
Leprechaunism and Rabson-Mendenhall Syndrome
Leprechaunism and Rabson-Mendenhall syndrome are rare syndromes
that result from mutations in the gene for the insulin receptor,
which leave it incapable of binding insulin. These mutations
produce the most extreme form of insulin resistance, leading
to persistent hyperglycemia and attendant pathology and retardation
of growth. The current treatment consists of administration
of increasing doses of insulin (up to several thousand units
per day). This treatment, if producing a result at all, yields
only a very partial result due to the absence of insulin binding
by its receptor. Treatment with insulin-like growth factor,
while potentially effective, is unavailable to these children.
Survival into the teens is rare. Ketone bodies in physiological
amounts have been shown to mimic the effects of insulin's
stimulation of the PDH multienzyme complex. Ketone bodies
can increase the Krebs TCA cycle metabolite contents, increase
the energy of ATP, and enhance metabolic efficiency. A ketone-rich,
low-carbohydrate diet might prove an effective treatment of
these conditions, which are currently without effective therapy.
Lafora Body Disease
Lafora body disease is an autosomal recessive form of progressive
myoclonic epilepsy resulting from a mutation on chromosome
6 in a region encoding a calcium-activated protein phosphatase.
Lafora body disease is pathologically characterized by the
deposition of polyglucan inclusion bodies in the skin, liver,
and brain. Patients present with progressive myoclonic epilepsy,
mild liver disease, rapid intellectual deterioration, and
insulin resistance, usually without frank diabetes; death
results within 10 years of the onset of clinical symptoms.
Currently, there is no treatment other than the administration
of a high-fat, ketogenic diet. However, because the patients
are often in their teens at presentation, the use of the ketogenic
diet is not desirable due to its long-term atherogenic potential.
A diet high in ketone bodies may prove an effective palliative
step in the treatment of these patients.
Fetal Alcohol Syndrome (FAS)
FAS is a set of specific birth defects caused by maternal
alcohol consumption during pregnancy. Unlike most other birth
defects, FAS has the potential to be entirely preventable,
because its direct cause, maternal drinking, is presumed to
be a controllable behavior.
Scientists have shown that exposure to alcohol at critical
times during brain development can induce excessive cell death
during normal programmed death (apoptosis) or trigger apoptosis
at inappropriate times. The result is smaller or abnormal
brain structures with fewer connections between brain cells.
This type of damage translates into developmental delays and
permanent cognitive and behavioral disabilities. Because normal
cell death is triggered by a highly regulated biochemical
pathway inside the cells, researchers have examined alcohol's
effects on various steps in the pathway in sensitive cells.
Evidence from several models and different neuronal cell populations
showed that alcohol reduces the availability or effectiveness
of regulatory molecules (neurotrophic factors) that promote
cell growth and survival by inhibiting the cell death pathway.
When certain sensitive neuronal cells were removed from the
brain and grown in culture in the presence of alcohol, their
survival rate was diminished. The survival rate was restored
to control levels by the addition of specific neurotrophic
factors. Current research continues to elucidate the exact
mechanisms by which alcohol interacts with these growth factors.
Furthermore, scientists are now testing whether alcohol's
deleterious effects can be prevented in the living animal
by treatments that restore the effectiveness of these regulatory
Recent advances in FAS research have been related to this
general theme of potential in vivo treatments for amelioration
of alcohol's effects on factors that support cell survival.
For the first time, a mammalian model (mouse) has demonstrated
that enhanced endogenous expression of a neurotrophic factor
(nerve growth factor [NGF]) can protect against ethanol-induced
cell death in a sensitive neuronal cell population of the
cerebellum. The results provide strong in vivo evidence that
the neurotoxic effects of ethanol on this cell population
are mediated by interactions with a neurotrophic factor that
is known to regulate apoptosis.
Another recent discovery is that performance on a learning
discrimination task is normal in animals exposed to ethanol
prenatally when their diet is supplemented with choline shortly
after birth. Choline is a nutrient that has multiple actions
on prenatal and early postnatal brain development, including
elevation of NGF. As expected, ethanol-exposed animals with
no choline treatment performed much more poorly than non-exposed
animals. Importantly, ethanol-exposed animals who received
the choline treatment performed at a level equal to that of
the non-exposed animals, with or without choline. The mechanisms
by which choline enhances learning are unknown. However, the
importance of choline in development has led to a recent recommendation
by the Institute of Medicine for a minimum amount of choline
in the diets of pregnant and lactating women.
During brain development, the neurotransmitter serotonin
stimulates the release of S100, which promotes serotonergic
neuron differentiation and growth of connective projections.
Scientists had previously shown that alcohol reduces the level
of serotonin during a critical period of development. New
findings suggest that during ethanol exposure, insufficient
serotonin levels diminish the ability of the serotonin receptor
to release S100, thus causing further loss of neurons and
glia. Treatment of the mother with serotonin agonists enhances
the ability of the remaining receptor-containing cells to
mediate S100 release.
N-methyl-D-aspartate (NMDA) receptors are critical for growth,
proliferation, differentiation, migration, and programmed
death of neurons in the developing brain. Recent research
has resulted in the first report that alcohol's well-documented
deleterious actions on the NMDA receptor may be mediated through
selective inhibition of neurosteroids. The findings may explain
the previously reported diminished behavioral response of
alcohol-exposed rat pups to maternal separation-induced stress
after treatment with an exogenous neurosteroid.
In an advance related to genetic influences on apoptosis
in FAS, a series of chick strains expressing differential
sensitivity to ethanol has provided major insights into the
relationship between alcohol-induced apoptotic events and
variability in expression of craniofacial dysmorphology, one
of the landmarks of FAS. After exposure to ethanol during
early embryogenesis, changes in facial morphology were correlated
with severity of ethanol-induced apoptosis. Ethanol treatment
resulted in multiple facial alterations that varied from strain
to strain; however, the responses to ethanol were consistent
and reproducible within strains. Thus, the genetic background
modulated the ethanol response. The study demonstrates the
power of using genetically distinct strains of animals with
differential sensitivity to ethanol as tools to tease out
the complex relationships between ethanol-induced molecular
insults and manifestations of the FAS phenotype.
Ongoing, New, and Planned Research Initiatives in Rare
Diseases in Children
Attempts are now being made to encourage the production of
sufficient quantities of palatable ketone body esters, which
can be used in an artificial diet for use in FRDA, GLUT1-deficient
epilepsy, leprechaunism, Rabson-Mendenhall syndrome, and lafora
body disease. Because it is estimated that patients may require
100 to 200 g per day of these ketones, industrial collaboration
will be required. Attempts to obtain this collaboration are
now under way. Trials of this therapy in selected cases of
this type are being planned for when collaboration is obtained
and animal toxicity tests performed.
Fetal Alcohol Syndrome (FAS)
More than 110 projects now contribute to the NIAAA FAS portfolio,
many of them with a particular focus on minority health and
health disparity issues. In addition, an ongoing RFA on DNA
microarrays has recently garnered a number of FAS proposals.
Many of the NIAAA's FAS-related projects and initiatives are
funded through FY 2004. Funding has not yet been allocated
for FY 2005 research.
Rare Disease-Specific Workshops, Symposia, and Meetings
A workshop seeking to identify candidate biomarkers of maternal
alcohol use and/or fetal ethanol exposure that can be used
to identify women at high risk of giving birth to a child
with FAS is scheduled for June 2001. Because early diagnosis
and intervention have been shown to improve developmental
outcomes for many birth defects, a prenatal or neonatal screen
would be desirable for patient counseling and identifying
high-risk infants before or at birth. Approaches to be discussed
include identifying metabolites, hormones, or proteins altered
by ethanol and using DNA arrays to identify altered gene expression
patterns. In addition, developmental stages and/or processes
that would be likely targets for in utero intervention will
be identified and potential in utero intervention strategies
discussed. A research agenda to help focus efforts to advance
this area of research will be developed.
In either the presence or the absence of diagnosable FAS,
other significant medical and behavioral problems may arise
from prenatal alcohol exposure and the resulting damage to
the developing brain, spinal cord, and central nervous system.
A conference to address the possible link observed between
sudden infant death syndrome (SIDS) and drinking during pregnancy
is planned for 2001. The conference will cover the scope of
these health problems in specific American Indian/Alaskan
Native communities, which exhibit a very high prevalence of
maternal drinking during pregnancy. Goals are to define the
research questions applicable to addressing the prenatal alcohol
use/SIDS connection to design a research study using a collaborative