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. Preliminary data show that Vitamin E (alpha-tocopherol) inhibits GDH activity in cell lines and improves hypoglycemia in a GDH HI mouse model. Based on these preclinical studies, Investigators hypothesize that Vitamin E will inhibit GDH activity and may impact hyperinsulinemic hypoglycemia and hyperammonemia in subjects with HI/HA syndrome. This hypothesis will be tested in a future study. In this initial pilot study, investigators will assess the tolerability of oral Vitamin E supplementation in subjects with HI/HA syndrome.
Investigators will assess the tolerability of oral Vitamin E supplementation in subjects with congenital hyperinsulinism (HI) and hyperammonemia (HA) syndrome.