Hyperinsulinemic Hypoglycemia, Familial, 6

Congenital hyperinsulinism (HI) is a rare disorder of pancreatic beta cell insulin secretion that causes persistent and severe hypoglycemia starting at birth. Hyperinsulinism/hyperammonemia (HI/HA) syndrome is the second most common type of congenital HI and is caused by activating mutations in glutamate dehydrogenase (GDH). Patients with HI/HA exhibit fasting hyperinsulinemic hypoglycemia, protein-induced hypoglycemia, hyperammonemia, seizures, and intellectual disability independent of hypoglycemia. These effects result from abnormal GDH activity in the beta cells, liver and kidney cells, neurons, and astrocytes. The only available treatment for HI/HA syndrome is diazoxide, which acts on the beta cells to decrease insulin secretion but has no effect on GDH activity itself or on other cell types. Thus, there remains a significant unmet need for improved therapies for this disorder. Pre-clinical data show that vitamin E inhibits GDH activity in human cell lines and improves fasting hypoglycemia in a GDH HI mouse model. Pilot study data show that vitamin E supplementation with a moderate dose is well-tolerated in children and adults with HI/HA syndrome, while continuing diazoxide treatment. However, most subjects continued to exhibit protein-induced hyperinsulinemic hypoglycemia. We hypothesize that a higher vitamin E dose will inhibit GDH over-activity in subjects with HI/HA syndrome, resulting in improved hyperinsulinemic hypoglycemia, reduced blood ammonia concentration, and decreased seizure activity.

Investigators will assess the tolerability of oral Vitamin E supplementation in subjects with congenital hyperinsulinism (HI) and hyperammonemia (HA) syndrome.

Early Check provides voluntary screening of newborns for a selected panel of conditions. The study has three main objectives: 1) develop and implement an approach to identify affected infants, 2) address the impact on infants and families who screen positive, and 3) evaluate the Early Check program. The Early Check screening will lead to earlier identification of newborns with rare health conditions in addition to providing important data on the implementation of this model program. Early diagnosis may result in health and development benefits for the newborns. Infants who have newborn screening in North Carolina will be eligible to participate, equating to over 120,000 eligible infants a year. Over 95% of participants are expected to screen negative. Newborns who screen positive and their parents are invited to additional research activities and services. Parents can enroll eligible newborns on the Early Check electronic Research Portal. Screening tests are conducted on residual blood from existing newborn screening dried blood spots. Confirmatory testing is provided free-of-charge for infants who screen positive, and carrier testing is provided to mothers of infants with fragile X. Affected newborns have a physical and developmental evaluation. Their parents have genetic counseling and are invited to participate in surveys and interviews. Ongoing evaluation of the program includes additional parent interviews.