About the National Urea Cycle Disorders Foundation

(From NUCDF Newsletter Winter 2000)

NUCDF Conference 2000 Highlights©

By Cindy Le Mons

Over a hundred parents, children and medical professionals from across the country and as far as England came together to participate in the 2000 Annual NUCDF Conference held at the Doubletree Hotel in Philadelphia in August. For some, it was their first opportunity to meet other families dealing with UCDs and to meet some of the top medical experts in the field. For others, it was a time to see old friends and make ones, but everyone was excited to hear about the latest developments in management and treatment.

Focus on NBS

One of the highlights of the Friday evening welcome reception was a press conference to announce that the Virtua Health system would be the first in New Jersey to offer supplemental comprehensive newborn screening for the nearly 7,000 babies born in their hospitals annually. Conference participants and members of the Philadelphia and New Jersey media gathered to hear Leonard Goldsmith, M.D., head of neonatology at Virtua, explain how Virtua became involved in the idea of screening through the efforts of NUCDF co-president, Mindy Rosen, and how Virtua’s NBS program could serve as a leader and model for other health systems considering NBS. Dr. Ed Naylor, President and Director of Neo Gen Screening Laboratories in Pittsburgh, also took the podium to talk about Neo Gen’s role as one of two screening labs involved (the other being Baylor) in the research and development of supplemental newborn screening and Neo Gen’s advocacy efforts for this life-saving technology for urea cycle and other metabolic disorders.

The press interviewed several NUCDF families, including a family whose infant daughter had been caught on the screen for citrullinemia in Pennsylvania and treated swiftly, thereby avoiding possible brain damage. For hours, parents exchanged stories, enjoyed the food, and talked with many of the physicians in attendance, while kids made fast friends.

The Big Day Begins

On Saturday morning, everyone gathered outside the conference room to visit, pick up information, and sample lo-pro foods from the exhibition tables set up by Ross Pediatrics, Montiff Incorporated, Scientific Hospital Supplies, and Dietary Specialties. Wendy Nawn of Tyler for Life Foundation was on hand with T-Shirts and pamphlets of information on newborn screening which parents could take home to pass on to their pediatricians. Our NUCDF registration table was loaded with handouts on UCDs, and board members Jill Olmack, Florie Enders, Joanie Fischback and Leafy Wilson worked to sign up volunteers and sell raffle tickets for baskets of lo-pro treats. With bagels and coffee in hand, the participants found seats in the conference room and waited for the presentations to begin.

Mendel Tuchman, M.D.

Dr. Tuchman, Chairman of Metabolism and Director of the Clinical Research Center at Children’s National Medical Center in Washington, D.C., presented a summary of the findings and conclusions of the Urea Cycle Disorders Consensus Meeting held in April 2000. Dr. Tuchman was co-chair of the Consensus Meeting, a gathering of the leading urea cycle disorder researchers and clinicians, including Drs. Mark Batshaw, Marshall Summar, Brendan Lee, Gerald Berry, Stephen Cederbaum, Robert Steiner, and J. V. Leonard of England, as well as experts in pathology and pharmakinetics. Other panel members included Sharon Vonachen, R.N., Pediatric Nurse Coordinator, and Mary Ahrens, genetic counselor, both from University of Minnesota, Maureen Varner, R.N., of Ucyclyd Pharma, Cindy LeMons and Mindy Rosen, co-presidents of NUCDF. Joe Cooper, President of Ucyclyd and Barbara Wuebbels, Clinical Director of Ucyclyd, lent their invaluable support to this important endeavor, which was sponsored by Ucyclyd Pharma in an effort to bring experts together towards the goal of obtaining a consensus for a new protocol on diagnostic and therapeutic guidelines for UCDs. These include treatment of acute neonatal hyperammonemia and recurrent hyperammonemia, chronic therapy, future therapeutic strategies, as well as establishing a collaborative network of centers for diagnosis and treatment, and ultimately to collect data on the therapeutic outcomes. The results of the Consensus meeting will be contained in eleven articles will appear in the Journal of Pediatrics in January 2001, one of the two leading pediatric journals with a wide readership among medical professionals dealing with children. The articles should have a major impact in terms of increased diagnoses and appropriate treatment for UCDs.

During his presentation, Dr. Tuchman explained many of the challenges which were ultimately raised at the Consensus Meeting, and were included in the Consensus statement. It was the consensus that most patients with UCDs remain undiagnosed, and that the population with UCDs in the United States is estimated to be in excess of 10,000 -- with the diagnosed population representing only a fraction of this number. At the same time, the number of specialists available to treat UCDs is decreasing. Additionally, only a few academic centers are conducting research for UCDs. Other than the Orphan Drug Act (under which Buphenyl was developed), there is little incentive for pharmaceutical companies to develop new drugs and therapies for treating hyperammonemia, and lobbying power for federal funding is weak. There are also reimbursement problems for the specialized care required by urea cycle disorder patients, with many families having problems, particularly within managed care programs, receiving coverage for formulas, drugs and supplements. Dr. Batshaw, Dr. Tuchman, Dr. Summar and others have proposed that a Urea Cycle Consortium be established to address these issues, as well as to accelerate the development of new research and treatment strategies. NUCDF will be lending its full support to this goal.

Dr. Tuchman also introduced the preliminary findings in the blood spot assay study. This study, as described in the last NUCDF newsletter, is designed to help in developing a method to measure levels of the drug Buphenyl from blood spots collected on filter paper. Dr. Tuchman explained how this study may assist in identifying therapeutic and/or toxic levels of the medications, and how the study will be expanded in the coming year. He also provided blood spot kits to families who wished to participate in the study.

Shideh Mofidi, M.S., R.D.

Shideh Mofidi, M.S., R.D., an expert nutritionist specializing in the treatment of urea cycle disorders, spoke next to the families about nutritional strategies for managing UCDs. Ms. Mofideh was recently elected to our NUCDF Board of Medical Advisors as our nutritional expert. She explained how the normal urea cycle serves to detoxify ammonia and make arginine, and how this function is interrupted when there is a defect in any one of the urea cycle enzymes, resulting in a buildup of ammonia. She cited some of the hallmarks of increased ammonia in children with urea cycle defects -- poor feeding, lethargy, confusion, disorientation, irritability, ataxia, and eventually coma -- and indicated that in many cases the onset of symptoms is related to change innutritional status, such as an increase in protein, fasting, infection, or trauma. She explained how the protein tolerance of children with UCDs can differ depending on age, growth needs, activity, the amount of residual enzyme activity the child has, and the child’s current state of health. She outlined the goals of therapy; first, to provide a diet sufficient in protein, arginine or citrulline (depending on the enzyme deficiency present) and energy to promote optimal physical and intellectual growth while maintaining metabolic balance. This metabolic balance involves maintaining ammonia and serum amino acid levels at as near normal as possible. The second goal of therapy is to provide symptomatic control and avoidance of acute episodes. There are several considerations in achieving these goals. A reduction of accumulated toxic metabolites, like ammonia, is necessary through the restriction of total protein. This restriction, however, is a fine art -- we must allow enough protein for growth, but not restrict protein to the point where a catabolic state is created. Catabolism occurs when the body does not have adequate protein intake and begins to break down its own lean muscle tissue to obtain energy and amino acids. This catabolic process creates ammonia in much the same way as ingesting dietary protein does. Since protein requirements change with age, development, and activity, protein and calorie allowances need to be assessed and properly adjusted on a regular basis by the nutritionist and metabolic specialist. It is often necessary to use medical foods, such as the amino acid formulas Cyclinex and Mead-Johnson UCD I and II. Without them, it can be difficult to get adequate growth while still maintaining metabolic balance.

The importance of caloric support was underscored. Ms. Mofidi explained that when a child gets sick with a cold or virus and does not eat, the body uses energy from the breakdown of muscle, again catabolizing. Adding adequate calories from carbohydrate and fat sources prevents and/or stops this catabolism. The children also require extra calories to ensure that their protein allowance is used for its essential function -- growth -- not for energy. Ultimately, extra calories provide energy, promote weight gain, preserve amino acids for growth, and help to minimize the level of toxic metabolites in the body.

Fluid support is also an important component in nutritional management. Ms. Mofidi indicated the importance of making sure the child receives all of the prescribed formula, not just parts of it; failure to consume all the formula results in a loss of protein, calories, essential vitamins and minerals, and fluid (water). It is important that the prescribed amount of water is used in the formula; if the formula is too concentrated (hyperosmolar), it can cause abdominal cramping, diarrhea, dehydration, nausea and vomiting. Any changes in the formula need to be made very gradually to ensure the child can tolerate the addition or subtraction of fluid or other ingredients.

Ms. Mofidi also explained how alternate pathways for waste nitrogen can be created to help rid the body of excess ammonia. The urea cycle is encouraged to "turn" by supplementing arginine or citrulline, which may not be adequately produced (again depending on the enzyme deficiency being treated), thereby helping eliminate ammonia from the body. Conjugating agents -- drugs like Buphenyl, sodium phenylacetate and sodium benzoate -- are also used to facilitate the removal of ammonia, each utilizing a different pathway. For example, sodium benzoate conjugates with glycine and is excreted as hippuric acid to create an alternative pathway for nitrogen (ammonia) removal. If amino acid formulas such as Cyclinex or Mead Johnson UCD I or II are not being used, folate and B6 may need to be supplemented during sodium benzoate therapy due to their potential loss through transamination.

Ms. Mofidi went on to describe how glutamine, a "storage form" of ammonia, relates to elevation of ammonia. When glutamine levels rise, plasma ammonia levels can also rise; often high glutamine levels are followed by high ammonia levels. One of the goals of therapy is to maintain plasma glutamine at as near normal levels as possible. Buphenyl conjugates with glutamine to form phenylacetylglutamine, thus removing two nitrogen (ammonia) molecules with each molecule of phenylacetylglutamine. This drug therapy can help to maintain both glutamine and ammonia at appropriate levels.

After her presentation, Ms. Mofidi fielded questions from the parents in the audience. Several of the questions involved how to provide high-calorie, low-protein diets to their children. Ms. Mofidi indicated that oils, such as canola oil, have a high caloric content and could be used as a supplement in the diet. She also suggested the addition of carbohydrate modules, such as Mead-Johnson 80056 or Ross ProPhree, as sources of extra calories, vitamins and minerals.

Dr. Batshaw Answers Questions

Many parents raised concerns about lack of appetite and "picky eating" in their children. Dr. Mark Batshaw offered several reasons why children with UCDs present with various degrees of anorexia, or did not want to eat. He indicated that UCD children have a high level of serotonin, a brain chemical which turns off appetite. Normally, serotonin levels increase about 20 minutes after eating and essentially give us the signal that we are full. In UCD children, serotonin levels are consistently high throughout the day because glutamine, another brain chemical that accumulates with UCDs, serves as a carrier transport mechanism in the brain for tryptophan, which becomes serotonin. The second factor in this anorexia, Dr. Batshaw indicates, is behavioral. Essentially, the children do not like food because it makes them feel sick. He likened this feeling to something we all may have experienced - having the flu or vomiting a food, and then having an aversion to that food. For these children, the feeling of being sick from eating high-protein foods is then generalized to other foods. He suggested that in some cases the use of nasogastric or G-tubes may be necessary in order to facilitate feedings. He also suggested obtaining the help of a behavioral psychologist who could assist in identifying and addressing the behavioral factors.

Both Dr. Batshaw and Ms. Mofidi stressed the importance that medications should be given with/during feedings to ensure that the medications help appropriately remove the ammonia created by the feedings. Dr. Marshall Summar then addressed several questions regarding the reflux that affects some children. He indicated that this is the result of acids rising into the esophagus from the stomach and is often painful. He reported that reflux sometimes requires the use of medications (H2 blockers) to reduce acid production or, in severe cases, surgery to tighten the sphincter at the top of the stomach and lower end of the esophagus (fundoplication).

Marshall Summar, M.D.

Dr. Summar, from Vanderbilt Medical Center in Nashville, Tennessee, began his presentation by speaking to the families about the importance of the Urea Cycle Consensus Meeting (for which he served as co-chair with Dr. Tuchman) and several research studies -- basically branch-offs of UCD research -- which show how the urea cycle is being implicated in other diseases. Our experts believe that if we make UCD research relevant to common mainstream diseases, the resources for our research will multiply dramatically. Dr. Summar has become involved in new research in areas in which the urea cycle has proven to be of vital importance, including newborn pulmonary hypertension, postcardiac surgery, liver disease, and bone marrow transplantation.

In underscoring the importance of UCD research now and in the future, he reflected on the important role that NUCDF has played in much of the work and in the directions CPS1 research has taken over the years. He indicated that the research had largely been encouraging by and/or partially funded by our foundation. Beginning with the early stages, he outlined the progress of this CPS1 research, from the determination of the gene sequence and functional code in the 1980s, to his latest projects investigating common polymorphisms (spontaneous changes) in the enzyme which may be relevant to the general population and relate to other fields of medicine.

Dr. Summar explained how the mutational analysis for CPS1 has evolved over the years, and the important discovery that there were no common mutations for CPS1, as there are in OTC deficiency, for example. Progress in the method for analysis has moved from requiring liver tissue in the ‘80s to the current standard of utilizing DNA from a blood sample, and has resulted in about 48 mutations being identified. However, because there are no common mutations (only 3 patients have been found with the same mutation on one gene) Dr. Summar indicated that mutational analysis for CPS1 is extremely time-consuming and expensive, and therefore probably not feasible for urgent prenatal diagnosis or for neonatal diagnosis.

While doing these CPS analyses, Dr. Summar found a number of common changes in the CPS enzyme, "polymorphisms," spread throughout the normal population. One of these changes has proven to be particularly interesting. It affects the function of the enzyme. In other words, if one sampled the general population on the street, Dr. Summar reports, and looked at the CPS function in their liver, some would have more function than others. He postulates that these changes may drop urea cycle function as much as 50% or more. Under normal conditions, these patients may never become symptomatic, but when exposed to environmental stressors such as chemotherapy, you begin to see symptoms of a urea cycle disorder.

Dr. Summer began to wonder if you have a compromise in the urea cycle in a normal person, such that it decreases flow through the cycle, what else would it affect? A few years ago, nitrous oxide research became very important in physiology and medical studies involving blood vessels. Nitrous oxide affects the dilation (opening) of arteries and blood vessels, and is dependent upon the urea cycle. One of the requirements for nitrous oxide production is that citrulline be processed to arginine. Dr. Summar began to question if there was a decrease in the flow of citrulline through the urea cycle, would that affect arginine availability and result in a decrease in nitrous oxide production? He wondered what role that might play in certain disease conditions.

Dr. Summar started investigating what types of conditions would then affect the urea cycle. The first one he looked at was valproic acid therapy, an anticonvulsant, which interferes with urea cycle enzyme production. Similarly, chronic cirrhosis of the liver causes damage to the urea cycle enzymes and often results in hyperammonemia. He also began looking at complications, including hyperammonemia, in patients undergoing chemotherapy and bone marrow transplantation to see if these complications might be related to disrupted function of the urea cycle.

To this end, Dr. Summar embarked on a study with bone marrow transplant (BMT) patients to determine the effect of high-dose chemotherapy on urea cycle flow. The study found that the pretransplant status of the urea cycle could be used as a predictor of which patients would be more likely to suffer complications and death. Dr. Summar genotyped 198 BMT patients and found correlations between the genotypes and the ultimate toxicity of the chemotherapy for those patients. He took this data and obtained an NIH grant. This project serves as a stepping stone to mainstream the research and draw more attention to urea cycle disorders.

With further investigation, the BMT study showed that nitrous oxide production was decreased by 40-50% after the patients received chemotherapy, which led to acute lung injury and occluded veins in the liver. Dr. Summar then began a pilot study supplementing citrulline in ten high-dose chemotherapy patients to determine whether this would increase nitrous oxide production. The current plan is to step this study up by adding arginine and seeing whether this will also increase nitrous oxide production. The results of this study will hopefully serve to stimulate more interest in the urea cycle, thereby increasing resources and funding and stepping up research.

One of the conditions Dr. Summar has looked at very recently is persistent pulmonary hypertension in the newborn (PPHN). This involves infants born with stress and asphyxia (a result of inadequate oxygen) who develop lung disease and pulmonary hypertension. Newborns possess less than one-half of their normal urea cycle function at birth. Since PPHN responds to nitrous oxide, this suggested that decreased nitrous oxide synthesis in the urea cycle might be an underlying cause of PPHN. Dr. Summar hypothesized that children developing PPHN have a difference in urea cycle enzyme production and/or nitrous oxide precursor availability, and therefore have a genetic predisposition involving the urea cycle. He discovered that arginine, citrulline and nitrous oxide levels were all decreased before treatment. A study has been initiated using supplemental citrulline to prevent PPHN in at-risk children. All of these new studies were based on previous research on urea cycle disorders. Dr. Summar believes this work will encourage further research, which he hopes will ultimately benefit children with UCDs.

Dr. Summar has also been working on some very preliminary studies involving prenatal cell transplants in mice. Last year, fetal surgery specialists at Vanderbilt became interested in collaborating with Dr. Summar on research for liver-based disorders, specifically urea cycle disorders. The concept revolved around the fact that during fetal life there is a window of opportunity during which "self and non-self recognition" has not yet occurred. This means that the immune system of the fetus will not react to cells from an outside source or donor. Urea cycle disorders are ideal candidates for this research since liver transplant restores normal metabolic function in these diseases and most UCDs can be diagnosed prenatally in at-risk families. The study involves obtaining normal liver cells from adult mice and infusing them into the livers of fetal sparse fur mice, which have OTC deficiency. The goal is to establish enough engrafted normal liver cells in the OTC-deficient fetal liver to restore a portion of the urea cycle activity. Although encouraged by the initial findings, Dr. Summar cautioned that the results of these animal studies are preliminary, but hopes that the technology may some day be applicable to humans.

Editor’s note: Highlights from Dr. Batshaw’s presentation will be included in an article on the treatment protocol update in the next issue of the Newsletter, as will information from Dr. Lee’s presentation on nitrogen flux studies and helper-dependent adenoviral vectors for use in gene transfer.