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Test tube that says IGF-1 test

PAPPA2: A genetic mystery

Test tube that says IGF-1 test

What would happen if you suddenly stopped growing at age 12 or 13?

Solving genetic growth mysteries and scheduling regular appointments with pediatric endocrinologists is atypical for most parents and pediatricians.

However, for children with growth disorders – a classification that typically describes children below the third or above the 97th percentile of growth charts for their age – receiving a diagnosis is half the battle to reaching average height. Understanding and creating treatment for a growth disorder, which could stem from an underlying medical illness, a genetic mutation or a problem with endocrine function, such as the production or action of growth hormone, is often the next step.

For Andrew Dauber, M.D., MMSc., the chief of endocrinology at Children’s National Health System, a third step is to use these clues to create larger datasets and blueprints to identify risk factors for rare growth disorders. By understanding genetic markers of growth disorders, endocrinologists can identify solutions and create plans for multidisciplinary care to help children reach developmental milestones and receive coordinated care throughout their lifespan.

A case study that Dauber and his research team continue to explore is how to correct for mutations in the PAPPA2 gene, which regulates human growth by releasing a key growth factor called insulin-like growth factor 1 (IGF-1). Dauber and his colleagues recently described a mutation in PAPPA2, observed in two families with multiple children affected with significant short stature. He found that this mutation decreased the bioavailability of IGF-1, stunting the growth and development of the children who carry this mutation.

While the PAPPA2 mutation is rare, endocrinologists, like Dauber, who understand its function and dysregulation can create solutions to support IGF-1 bioavailability, thereby supporting healthy growth and development in children.

Understanding barriers to IGF-1 function can also help researchers gain insight into the relationship between PAPPA2, levels of circulating insulin in the body, which could cause insulin resistance, and other growth hormones. For now, Dauber and his research team are exploring how to use PAPPA2 to increase IGF-1 in circulation among people with height disorders in the hopes of improving their growth.

“The population of children who have PAPPA2 mutations is small and we’re finding out that two children could respond to the same treatment in different ways,” says Dauber. “One medication could work modestly in one child and support short growth spurts, such as growing by 5 or 6 cm a year. It could also create undesirable side effects, such as headaches and migraines in another, and render it ineffective. However, the clues we walk away with enable us to test new solutions, and confirm or dissolve our hunches, about what may be preventing the bioactive release of essential growth hormones.”

To generate controls for healthy patterns of growth and development, Dauber and his research team are analyzing the relationship between PAPPA2, STC2 and IGFBP-3 concentrations among 838 relatively healthy pediatric participants, ages 3-18, with traditional growth patterns.

They are studying PAPPA2, STC2 and intact IGFBP-3 concentrations throughout childhood and the researchers are already surprised to find PAPPA2, a positive modulator of growth and IGF- bioavailability, decreased with age, while STC2, a negative modulator and traditional growth inhibitor, increased with age.

“As pediatric endocrinology researchers and clinicians, we’re looking at the pathology of traditional growth patterns and growth disorders with an open mind,” says Dr. Dauber. “These data sets are invaluable as they confirm or challenge our theories, which enable us to create and test new forms of personalized treatments. We’ll continue to share this knowledge, which informs other researchers and accelerates the field of pediatric endocrinology.”

This research was presented at the annual meeting of the European Society of Pediatric Endocrinology in Athens on Sept. 28, 2018.

Dauber and his research team will present their findings at endocrinology conferences and grand rounds throughout 2018 and 2019.

To view Dr. Dauber’s most recent research and pediatric endocrinology reviews, visit PubMed.

Andrew Dauber

Growth disorder study starts by analyzing DNA

The National Institutes of Health has awarded Andrew Dauber, M.D., MMSc, the chief of endocrinology at Children’s National Health System, a five-year grant that will allow four pediatric health systems to compile and study clinical and genetic markers of severe pediatric growth disorders.

The study will use the electronic health records of large health systems combined with DNA samples from dozens of children, with the goal of enabling endocrinologists to detect children with previously undiagnosed severe genetic growth disorders.

“If you’re a pediatrician treating an 8-year-old patient who has stopped growing, the first thing you’ll want to do is determine the underlying cause, which could be due to many factors including a genetic mutation,” says Dr. Dauber. “There are many reasons why children grow poorly and it is often very difficult to figure out what is causing the problem. However, the various causes may be treated quite differently and may alert us to other medical issues that we need to watch out for. We need to be able to identify clues from the patient’s clinical presentation that may point us to the right diagnosis.”

Dr. Dauber and endocrinology researchers from Children’s National Health System, Cincinnati Children’s Hospital Medical Center, Boston Children’s Hospital and The Children’s Hospital of Philadelphia will use electronic health records to identify children who likely have rare genetic growth disorders. They will then use cutting-edge DNA sequencing technologies, whole exome sequences, to identify novel genetic causes of severe growth disorders. Patients with growth hormone resistance, resistance to insulin-like growth factor 1 (IGF-I) and severe short stature inherited from a single parent will be recruited for the initial phases of the study.

“It’s rare to find patients meeting criteria for each of these subgroups, which is why it’s critical to work collaboratively across institutions,” says Dr. Dauber. “This type of genetic sorting and sharing brings us closer to identifying new markers for severe or treatment-resistant growth disorders, which will help alert pediatricians and parents to potential risks earlier on in a child’s life.”

In addition to assessing genetic markers for short stature, the endocrinologists will conduct pilot studies of targeted interventions, such as IGF-I therapy in patients with mutations in the growth hormone pathway, based on these genetic underpinnings.

“Ideally, by identifying markers of severe growth disorders first, we’ll be able to provide targeted treatments and therapies later on to help patients throughout their lifespan,” adds Dr. Dauber.

Typical treatments for atypical growth patterns include growth hormone or less commonly insulin-like growth factor, or IGF-1, for short stature and hormone-inhibiting treatments for precocious puberty.

The multicenter clinical trial is funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), under grant Ro1HD093622, and runs through June 30, 2023.

boy on a treadmil

Therapeutic targets in African-American youth with type 2 diabetes

boy on a treadmil

Ongoing research is helping to define the broad spectrum and multi-faceted nature of type 2 diabetes in terms of its presentation, its rapidity of progression and its underlying genetic susceptibilities. In a recent study of 8,980 adults published in The Lancet, diabetes was further classified into five clusters, ranging from insulin-deficient, typically referred to as type 1, to groups of patients with primary insulin-resistance, traditionally classified as type 2 diabetes, with the caveat that each cluster had a distinct risk profile for disease progression and risk for diabetes complications.

Moreover, investigators have recently demonstrated, through the Restoring Insulin Secretion (RISE) Consortium, that youth compared to adults with early type 2 diabetes have greater insulin resistance relative to insulin secretion. Understanding variances on the diabetes spectrum, especially as it relates to risk for disease progression in youth, helps researchers develop targeted therapies that may help reduce complications and the burden of this chronic disease.

Ongoing research

Stephanie Chung, M.B.B.S., a pediatric endocrinologist at the National Institutes of Health and an adjunct assistant professor of pediatrics at Children’s National, is one researcher who hopes to use this knowledge to transform public health outcomes. Dr. Chung is studying how teens and young adults with severe insulin-resistant diabetes (SIRD) respond to new treatment, paired with lifestyle-based interventions.

Here is a Q&A with Dr. Chung about her latest research:

Tell Innovation District readers more about your diabetes research. How has your previous research influenced this study?

My research and publications are focused on understanding how genes, environment and lifestyle factors contribute to the pathology of diabetes, obesity and insulin resistance in populations of African descent and on identifying more effective screening and treatment options.

We know that African-American youth with type 2 diabetes have the highest complication and treatment failure rates among minority youth. However, the reasons underlying this health disparity are still not fully understood. Metformin, the only approved oral diabetes treatment for youth with type 2 diabetes, works less than half of the time in African-American youth. Although new evidence suggests that gut bacteria and genetics may influence the efficacy of metformin, this data is insufficient in African-American youth.

What is your goal with this diabetes clinical study?

The primary objective of this new study, entitled Therapeutic Targets in African-American Youth with Type 2 Diabetes, is to compare the combination of metformin and liraglutide versus metformin alone to reduce excess glucose produced by the liver in African-American youth with type 2 diabetes.

Additional objectives will evaluate the mechanism of action in the liver of these two agents and the influence of genetics and gut bacteria. This project brings together the research expertise of the National Institute of Diabetes and Digestive and Kidney Diseases, the National Human Genome Research Institute and the Children’s National Medical Center.

Do you envision this type of dual therapy, a combination of drugs and lifestyle interventions, will serve as a bridge to optimal insulin function?

While metformin, diet and lifestyle changes remain the mainstay of diabetes treatment, our study will evaluate whether this combination regimen could help to slow the progression of type 2 diabetes in African American youth. Our ultimate goal is the development of new precision medicine treatment options that can address the disparities in outcomes for African-American youth with type 2 diabetes.

What lessons do you see participants learning as they progress through the trial?

Our patients and their families are equal partners in care. Our comprehensive team of doctors, nurses, dietitians and counselors work closely with the patients and their families to help empower them to take charge of managing their diabetes. We teach them skills that include regularly monitoring their blood glucose levels and understanding how their activity and foods affect these levels. They are coached on making healthy food choices and incorporating exercise into their daily lives.

How do you teach children and teens about how their body responds to different foods?

This education starts as soon as participants enter the study. While patients are at the NIH for the inpatient study, we provide them with meals containing different ratios of carbohydrates, proteins, and fats and help them to analyze how their blood sugar responds to these levels, both before and after they take the medication. This type of education is important since participants will also have to monitor their blood sugar twice a day at home during the study. Most of the time, we use real-life situations as teaching moments. For example, if a participant had pizza for dinner, we will discuss with them why their blood sugar spiked and suggest alternative food choices. We provide this type of coaching every week. I often joke that after three months they become tired of hearing from us. But one of the strengths of this study is that participants receive personalized feedback that enables them to make healthy food choices for the rest of their life.

Can you tell us more about targeted food choices for teens?

A very enlightening procedure that we conduct on all of our study participants is measuring their basal metabolic rate (energy expenditure at rest). We show them how many calories they need to consume each day to maintain their body’s normal functions and compare that number with an estimate of how many calories they usually consume in a day. For many participants this is the first time that they have insight into the reasons for their weight gain.

How does this lab work help with meal planning?

After we create a participant’s metabolic chart we make food plans that support their lifestyle and caloric needs and are realistic to follow. For example, a 2,000 calorie per day diet can be separated into 400 calories for breakfast, 600 calories for lunch, 200 calories for snack and 800 calories for dinner.

How do you envision personalizing the field of diabetes research and treatment?

A precision medicine approach to type 2 diabetes will help us to better explore if and how factors like genes, environment and lifestyle impact insulin and glucose metabolism in populations with significant treatment outcomes disparities. With this approach we hope to uncover novel targeted treatment and prevention strategies that demonstrate more efficacy and cost-efficiency than current treatment approaches for high-risk populations.

Where can people learn more about the trial?

Learn more about the study by watching this informational video. If you’re interested in joining the study, please contact the NIH Office of Clinical Trial Recruitment at 866-999-1116.