86 - Disorders of Carbohydrate Metabolism in the Neonate

Abstract

Glucose, a six-carbon sugar, is the most important source of energy for all cells and is a universal currency for energy (ATP) production. It is also an essential source of energy for brain metabolism. The fasting blood glucose concentration in the adult is regulated within a rather narrow range (70-100 mg/dL), representing a balance between utilization of glucose to fuel cellular metabolic processes and availability of glucose to sustain the fetus via maternal–placental transport, transitioning in the newborn by glycogenolysis and gluconeogenesis while nutritional intake is established. After separation from the placenta, disturbances in the glucose homeostasis resulting in hypoglycemia are common occurrences in the preterm and term newborn infants. Yet uncertainty regarding the definition of hypoglycemia and long-term untoward effects of transient or recurrent hypoglycemia remain. The pancreatic beta cell maintains steady state blood glucose by a complex feedback mechanism involving the glucose sensing KATP channels toward regulating insulin secretion. Mutations in KATP channel genes can result in hyperinsulinemia due to loss of KATP function and continuous opening of Ca+ channels facilitating insulin release or neonatal diabetes due to gain of KATP channel function and closure of Ca+ channels that deters insulin release. Adequate storage of glucose and function of skeletal muscle, cardiac muscle, and white adipose tissue requires hormonal regulation by insulin and glucagon. Hepatic glycogen storage is essential for successful glycogenolysis, a process necessary for maintaining glucose homeostasis during the fasting state encountered between milk intake in the newborn. In this chapter we discuss various congenital and acquired conditions in the neonate that perturb glucose homeostasis.