Our Research

Division of Endocrinology Research

Research in the division of pediatric endocrinology includes basic science, translational and clinical research. The division is host to a wide variety of research programs encompassing various aspects of the endocrine system of relevance to children. Topics of research include hypoglycemia, type 1 and type 2 diabetes, growth disorders, disorders of bone and mineral metabolism and obesity.

Stanely Lab

Resources

HI-mouse models, isolation and culture of islets from mice, rats, islet perifusion, enzyme kinetics, isolation of ?-cells, multiplex immunoassays, CAP-certified insulin assays, EBV transformed lymphocytes. mutation detection.

Research

I am a Pediatric Endocrinologist with a long-standing interest in translational and basic research related to disorders of insulin secretion in infants and children. My main interests have been centered on investigations into the causes of hypoglycemia in infants and children. Hypoglycemia in infants and children can lead to seizures, developmental delay, and permanent brain damage. Over the years, our work has shown that Hyperinsulinism (HI) is the most common cause of both transient and permanent disorders of hypoglycemia. HI is characterized by dysregulated insulin secretion, which results in persistent mild to severe hypoglycemia. Hyperinsulinism can also be associated with perinatal stress such as birth asphyxia, maternal toxemia, prematurity, or intrauterine growth retardation, resulting in prolonged neonatal hypoglycemia. The various forms of HI represent a group of clinically, genetically, and morphologically heterogeneous disorders.

Early in my research career, I described methods for diagnosis and treatment of infants with hyperinsulinism and was actively involved in the discovery of many of the known genetic disorders of ketogenesis and fatty acid oxidation. Over the past 15 years, I have contributed to the identification of the four major genetic loci for hyperinsulinism, GLUD-1, GCK, SUR-1, and KIR6.2. More recently, I have been characterizing defects in other genes that lead to HI, including SCHAD and MCT1. SUR-1 and Kir6.2 combine to form the ?-cell plasma membrane KATP channel. The channel is a heterooctameric complex comprising 4 Kir6.2 subunits which form the ion pore, coupled to 4 SUR-1 regulatory subunits. Inactivating mutations in the KATP channel result in constitutive closure of the channel allowing membrane depolarization and calcium influx into the ?-cell, resulting in constitutive insulin secretion from the ?-cell. These mutations cause KATP channel hyperinsulinism (KATP-HI), the most common and severe form of HI. More than 100 mutations of SUR-1 and 20 mutations of KIR6.2 have been found. Most of the mutations are recessive, but a few dominantly expressed mutations have been reported. There are two distinct histological forms of KATPHI, diffuse HI and focal HI. The preoperative differentiation of these two forms is very important because the surgical management is radically different. The focal form of the disease can be cured if the focal lesion can be localized accurately and completely resected with surgery. One of my ongoing research interests has been to assess the reliability of [18F]DOPA PET scans in its accuracy in localizing focal lesions to aid in their surgical excision.

My lab discovered glutamate dehydrogenase HI (GLUD-1), the second most common form of HI. It is also known as the hyperinsulinism and hyperammonemia (HI/HA) syndrome. It is caused by activating mutations in GDH, a mitochondrial enzyme (9 ), and a key regulator of amino acid and ammonia metabolism in ?-cells, liver, and brain. A mutation in HADH, the gene encoding the mitochondrial enzyme SCHAD, is also associated with HI. SCHAD catalyzes the third of 4 steps in the mitochondrial fatty acid oxidation pathway by catalyzing the oxidation of short-chain substrates. My laboratory has recently shown that dysregulation of insulin secretion associated with SCHAD deficiency is due to an activation of GDH enzyme activity, reflecting the loss of an inhibitory protein-protein interaction of SCHAD upon GDH, which has not previously been recognized.

More recently, my laboratory has begun to focus on HI in children that involves both novel molecular defects of known loci, as well as, previously unrecognized new genetic loci. Using linkage analysis and NexGen sequencing techniques, we have characterized a family with HI that formed the basis for the identification of idiopathic hypoglycemia of infancy in 1954. We have found no mutations in the known HI loci, however, our analysis has identified a novel 8.2Mb locus in chromosome 10 containing 49 genes. Gene capture and next-gen sequencing techniques are being used to identify disease-causing mutations in this region.

I also serve as the Medical Director of the Translational Core Laboratory (TCL), which is part of the Clinical and Translational Research Center (formerly the General Clinical Research Center) here at the Childrenís Hospital of Philadelphia (CHOP). The Clinical and Translational Research Center is part of a integrated strategy to support clinical and translational research and education by the University of Pennsylvania, (CHOP), the Wistar Institute, and University of the Sciences in Philadelphia. The functions of the CHOP-TCL are grouped into four sub-cores: (1) Specimen Collection, Processing and Shipping Core, (2) Biochemistry Core, (3) DNA Isolation-Cell Culture Core, and (4) Molecular Biology-Genetics Core. The TCL provides CTRC investigators with access to a wide range of unique assays and services for patient-oriented research. This includes help with protocol design, specimen collection, processing, tracking, and storage, immunoassays (single and multi-plex), DNA isolation and re-sequencing, cell culture services, PCR-based assays (SNP, real-time PCR gene expression), and mutation detection. The CHOP TCL is focused on performing these clinical research-quality assays in a cost effective manner.

Publications