The response of blood glucose, ketones, and plasma nonesterified fatty acids to fasting and epinephrine injection in infants and children

Emerging routes to the generation of functional β-cells for diabetes mellitus cell therapy

Diabetes mellitus, which affects more than 463 million people globally, is caused by the autoimmune ablation or functional loss of insulin-producing β-cells, and prevalence is projected to continue rising over the next decades. Generating β-cells to mitigate the aberrant glucose homeostasis manifested in the disease has remained elusive. Substantial advances have been made in producing mature β-cells from human pluripotent stem cells that respond appropriately to dynamic changes in glucose concentrations in vitro and rapidly function in vivo following transplantation in mice. Other potential avenues to produce functional β-cells include: transdifferentiation of closely related cell types (for example, other pancreatic islet cells such as α-cells, or other cells derived from endoderm); the engineering of non-β-cells that are capable of modulating blood sugar; and the construction of synthetic 'cells' or particles mimicking functional aspects of β-cells. This Review focuses on the current status of generating β-cells via these diverse routes, highlighting the unique advantages and challenges of each approach. Given the remarkable progress in this field, scalable bioengineering processes are also discussed for the realization of the therapeutic potential of derived β-cells.

Recapitulating endocrine cell clustering in culture promotes maturation of human stem-cell-derived β cells

Despite advances in the differentiation of insulin-producing cells from human embryonic stem cells, the generation of mature functional β cells in vitro has remained elusive. To accomplish this goal, we have developed cell culture conditions to closely mimic events occurring during pancreatic islet organogenesis and β cell maturation. In particular, we have focused on recapitulating endocrine cell clustering by isolating and reaggregating immature β-like cells to form islet-sized enriched β-clusters (eBCs). eBCs display physiological properties analogous to primary human β cells, including robust dynamic insulin secretion, increased calcium signalling in response to secretagogues, and improved mitochondrial energization. Notably, endocrine cell clustering induces metabolic maturation by driving mitochondrial oxidative respiration, a process central to stimulus-secretion coupling in mature β cells. eBCs display glucose-stimulated insulin secretion as early as three days after transplantation in mice. In summary, replicating aspects of endocrine cell clustering permits the generation of stem-cell-derived β cells that resemble their endogenous counterparts.

Poor specificity of low growth hormone and cortisol levels during fasting hypoglycemia for the diagnoses of growth hormone deficiency and adrenal insufficiency

OBJECTIVES

Fasting tests are used to identify the cause of hypoglycemia in children. The purposes of this study were to (1) determine whether growth hormone and cortisol levels obtained at the time of hypoglycemia in such tests can identify children with growth hormone and/or cortisol deficiency and (2) identify potential clinical factors that influence growth hormone and cortisol responses to hypoglycemia.

STUDY DESIGN

The design consisted of chart review of all diagnostic fasting tests conducted over a 3-year period (n = 151). A normal growth hormone level was defined as >/=7.5 ng/mL, and a normal cortisol level was defined as >/=18 mug/dL.

RESULTS

During the fasting tests, 84 children (median age: 1.3 years [2 days to 14.3 years]), became hypoglycemic, with blood glucose </=50 mg/dL. Diagnoses included normal, ketotic hypoglycemia, hyperinsulinism, fatty acid-oxidation defects, glycogen-storage disease, and late dumping hypoglycemia. A total of 70% had growth hormone and cortisol levels less than the "normal" thresholds regardless of diagnosis. Of various factors (age, diagnosis, fast duration, duration blood glucose level of <60 mg/dL, and blood glucose nadir), only age was positively associated with cortisol, and none were consistently related to growth hormone.

CONCLUSIONS

A singe low growth hormone or cortisol value at the time of fasting hypoglycemia has poor specificity for the respective diagnoses of growth hormone deficiency and adrenal insufficiency.

Energy metabolism in mammalian brain during development

Production of energy for the maintenance of ionic disequilibria necessary for generation and transmission of nerve impulses is one of the primary functions of the brain. This review attempts to link the plethora of information on the maturation of the central nervous system with the ontogeny of ATP metabolism, placing special emphasis on variations that occur during development in different brain regions and across the mammalian species. It correlates morphological events and markers with biochemical changes in activities of enzymes and pathways that participate in the production of ATP. The paper also evaluates alterations in energy levels as a function of age and, based on the tenet that ATP synthesis and utilization cannot be considered in isolation, investigates maturational profiles of the key processes that utilize energy. Finally, an attempt is made to assess the relevance of currently available animal models to improvement of our understanding of the etiopathology of various disease states in the human infant. This is deemed essential for the development and testing of novel strategies for prevention and treatment of several severe neurological deficits.

Defect in alpha-ketobutyrate metabolism: a new inborn error

A pair of siblings with clinical symptoms of cyclic vomiting and ketoacidosis were found to have a biochemical triad of normoglycemia, ketoacidosis and elevated levels of alpha-hydroxy- and alpha-aminobutyrate in plasma and urine. Methionine loading studies in both sibs produced prompt rises in plasma methionine and alpha-aminobutyrate levels, with a subsequent increase in urinary alpha-hydroxybutyrate, as well. Leukocytes from both siblings showed normal oxidation of [3-14C]propionate. Increased inorganic sulfate excretion after methionine loading implied an intact transsulfuration pathway in both siblings. On the basis of the studies detailed in this report, we conclude that these siblings suffer from a defect in alpha-ketobutyrate oxidation, a newly described defect of organic acid metabolism.

Variation in plasma ketone bodies during a 24-hour fast in normal and in hypoglycemic children: relationship to age

The variations in blood ketone bodies, blood glucose, and insulin were studied in 19 normal and 14 hypoglycemic children, 4 months to 13 years of age, during a 24-hour fast. Except in four patients (two with hyperinsulinism and two with congenital defect in ketogenesis), a significant increase in blood ketone bodies was observed in both controls and patients. A progressive decrease in glucose concentrations was observed up to but not after 20 hours. A highly negative correlation between blood ketone bodies and blood glucose was found, with a large dispersion of blood ketone bodies, especially for those corresponding to the blood glucose between 45 and 65 mg/dl. This dispersion was consistently reduced in a homogenous age group of 4 to 6 years with similar glucose values. There was a positive correlation between age and blood glucose from hour 21 on, and an inverse relationship between age and blood ketone bodies from hour 15 on. The same high inverse relationship between age and blood ketone bodies was again observed when the variable of glucose concentration was factored out, demonstrating that the variation in blood ketone bodies is indeed related to age. These findings need to be taken into account in the interpretation of fasting blood ketone bodies, especially when used as an aid in the diagnosis of the various forms of childhood hypoglycemia, and of hypoketotic states.

Hepatic glycogen synthetase deficiency. Further studies on a family

A family with hepatic glycogen synthetase deficiency originally studied in 1962, was restudied 7 years later. Blood glucose concentrations were measured after glucagon administration, and both blood glucose and plasma cortisol were measured during periods of prolonged fasting and isocaloric carbohydrate-free diets. The twins on whom the original diagnosis was made had an improved ability to maintain a normal blood glucose concentration, but still had episodes of hypoglycaemia; their ability to store glycogen in the liver remained extremely poor. Two sibs still had both frequent episodes of hypoglycaemia, and a diminished capacity to convert glucose to glycogen; their ability to store glycogen in the liver was variable. A third sib was normal. No decrease in plasma cortisol concentrations was noted at any time in any of the children. An increase in blood lactate concentrations after oral administration of glucose, and more particularly, of galactose, is a useful test in the differential diagnosis of hepatic glycogen synthetase deficiency. For definitive diagnosis a liver biopsy with assay of individual enzymes is essential.

Diagnosis of ketotic hypoglycaemia of childhood

Twenty cases of ketotic hypoglycaemia have been diagnosed in one medical unit in the past 8 years. Typically the children were `dysmature' at birth, with a history suggesting hypoglycaemia in the first 36 hours of life, and they have remained small and thin. 4 are the smaller of non-identical twins. Most presented acutely with recurrent early morning convulsions after the age of 1 year. A dietary ketogenic provocation test, which is the standard diagnostic procedure, induced hypoglycaemia in the 19 cases in which it was done, but the children frequently remained asymptomatic. This contrasts with the original description of the test. Treatment with carbohydrate supplements at bedtime has been successful in controlling symptoms in 16 of the 19 children followed up. Of the failures, 1 is attributable to parental non-co-operation, while in 2 others the original diagnosis was possibly erroneous.

Childhood status asthmaticus. Recent clinical and laboratory observations and their application in treatment

The complications of bronchial asthma are increasing. This paper presents clini cal and laboratory data obtained from a group of children admitted in status asthmaticus to Children's Hospital of Philadelphia and describes in detail the program of management which emerged from study of these data. Speculations are also made regarding the pathophysi ology of this illness.