The concentration of blood components related to fuel metabolism during prolonged fasting in children

Idiopathic Pathological Ketotic Hypoglycemia: Finding the Needle in a Haystack

Sick children often have a decreased appetite and experience vomiting and diarrhea; however, hypoglycemia (plasma glucose concentration ≤50 mg/dL or 2.8 mmol/L) is rare. Ketotic hypoglycemia (KH) is the most common cause of hypoglycemia presenting to an Emergency Department in a previously healthy child between 6 months and 6 years of age. Ketosis and hypoglycemia are now well understood to be normal physiologic responses of young children to prolonged fasting.There is now substantial evidence that the term KH describes a variety of conditions including both the lower end of the normal distribution of fasting tolerance in young children as well as numerous rare disorders that impair fasting adaptation. Recent advances in molecular genetic testing have led to the discovery of these rare disorders. Idiopathic pathological KH is a diagnosis of exclusion that describes rare children who have abnormally limited fasting tolerance, experience recurrent episodes of KH, or develop symptoms of hypoglycemia despite elevated ketone levels, and in whom an explanation cannot be found despite extensive investigation. This review provides an approach to distinguishing between physiological KH and pathological KH and includes recommendations for management.

Dynamic Methods for Childhood Hypoglycemia Phenotyping: A Narrative Review

Hypoglycemia results from an imbalance between glucose entering the blood compartment and glucose demand, caused by a defect in the mechanisms regulating postprandial glucose homeostasis. Hypoglycemia represents one of the most common metabolic emergencies in childhood, potentially leading to serious neurologic sequelae, including death. Therefore, appropriate investigation of its specific etiology is paramount to provide adequate diagnosis, specific therapy and prevent its recurrence. In the absence of critical samples for biochemical studies, etiological assessment of children with hypoglycemia may include dynamic methods, such as in vivo functional tests, and continuous glucose monitoring. By providing detailed information on actual glucose fluxes in vivo, proof-of-concept studies have illustrated the potential (clinical) application of dynamic stable isotope techniques to define biochemical and clinical phenotypes of inherited metabolic diseases associated with hypoglycemia. According to the textbooks, individuals with glycogen storage disease type I (GSD I) display the most severe hypoglycemia/fasting intolerance. In this review, three dynamic methods are discussed which may be considered during both diagnostic work-up and monitoring of children with hypoglycemia: 1) functional in vivo tests; 2) in vivo metabolic profiling by continuous glucose monitoring (CGM); 3) stable isotope techniques. Future applications and benefits of dynamic methods in children with hypoglycemia are also discussed.

Towards enhanced understanding of idiopathic ketotic hypoglycemia: a literature review and introduction of the patient organization, Ketotic Hypoglycemia International

BACKGROUND

Idiopathic Ketotic hypoglycemia (IKH) is a diagnosis of exclusion. Although considered as the most frequent cause of hypoglycemia in childhood, little progress has been made to advance the understanding of IKH since the medical term was coined in 1964. We aimed to review the literature on ketotic hypoglycemia (KH) and introduce a novel patient organization, Ketotic Hypoglycemia International (KHI).

RESULTS

IKH may be diagnosed after the exclusion of various metabolic and hormonal diseases with KH. Although often mild and self-limiting, more severe and long-lasting IKH occurs. We therefore divide IKH in physiological KH and pathological KH, the latter defined as recurrent symptomatic, or occasionally symptomatic, episodes with beta-hydroxybutyrate ≥ 1.0 mmol/L and blood glucose < 70 mg/dL (3.9 mol/L), in the absence of prolonged fasting, acute infections and chronic diseases known to cause KH. Pathological KH may represent undiscovered diseases, e.g. glycogen storage disease IXa, Silver-Russel syndrome, and ketone transporter defects, or suggested novel disease entities identified by exome sequencing. The management of KH aims to prevent hypoglycemia, fatty acid oxidation and protein deficiency by supplying adequate amounts of carbohydrates and protein, including nutritional therapy, uncooked cornstarch, and sometimes continuous tube feeding by night. Still, intravenous dextrose may be needed in acute KH episodes. Failure to acknowledge that IKH can be more than normal variation may lead to under-treatment. KHI is a non-profit, patient-centric, global organization established in 2020. The organization was created by adult IKH patients, patient family members, and volunteers. The mission of KHI is to enhance the understanding of IKH while advocating for patients, their families and the continued research into KH.

CONCLUSION

IKH is a heterogeneous disorder including physiological KH and pathological KH. IKH may represent missed diagnoses or novel disease entities, but shares common management principles to prevent fatty acid oxygenation. KHI, a novel patient organization, aims to enhance the understanding of IKH by supporting IKH families and research into IKH.

Changes in pediatric plasma acylcarnitines upon fasting for refined interpretation of metabolic stress

BACKGROUND

Childhood fasting intolerance is a life-threatening problem associated with various inborn errors of metabolism. Plasma acylcarnitines reflect fatty acid oxidation and help determine fasting intolerance etiology. Pediatric reference values of plasma acylcarnitines upon fasting are not available, complicating interpretation of stress samples.

METHODS

Retrospective analysis of supervised clinical fasting studies between 01/2005-09/2012. Exclusion criteria involved patients with (suspected) disorders, repeated tests or incomplete results. Remaining children were grouped according to age: group A (≤24 months), B (25-84 months) and C (≥85 months). Median and 2.5^th to 97.5^th percentiles of basic metabolic parameters and acylcarnitines were determined at start and end of testing on the ward and analyzed for significant differences (p<0.05).

RESULTS

Out of 127 fasting studies, 48 were included: group A (n=13), B (n=23) and C (n=12). Hypoglycemia occurred in 21%. Children from group C demonstrated significantly higher end glucose concentrations while end ketone body concentrations were significantly lower compared to younger children. In all groups, free carnitine and C3-carnitine significantly decreased upon fasting, while C2-, C6-, C12:1-, C12-, C14:1-, C14-, C16:1- and C16-carnitine significantly increased. End concentrations of C6-, C12:1-, C12-, C14:1-, C14-, C16:1-, C16- and C18:1-carnitine were significantly lower in children ≥85 months compared to younger children.

CONCLUSIONS

Fasting-induced counter-regulatory mechanisms to maintain energy homeostasis are age-dependent. This influences the changes in basic metabolic parameters and acylcarnitine profiles. Our data enable improved interpretation of the individual fasting response and may support assessment of minimal safe fasting times or treatment responses in patients.

Metabolic profiles in children during fasting

BACKGROUND

Hypoglycemia is one of the most common metabolic derangements in childhood. To establish the cause of hypoglycemia, fasting tolerance tests can be used. Currently available reference values for fasting tolerance tests have limitations in their use in daily practice.

OBJECTIVE

The aim of this study was to determine the reference values of metabolites involved in glucose homeostasis during fasting in healthy children.

METHODS

This study included a retrospective analysis of 488 fasting tests. All tests of patients (n = 321) with disorders, including metabolic and endocrine disorders, were excluded, as were tests performed in children who were over- or underweight.

RESULTS

In 167 fasting tests performed in the study, hypoglycemia was reached in 52 (31%) tests. On the basis of the time until hypoglycemia was reached, 3 age groups could be defined: (1) children aged 0 to 24 months (median 15 months) (n = 49); (2) children aged 25 to 84 months (median 45 months) (n = 79); (3) and children aged 85 to 216 months (median 106 months) (n = 39). In all groups, a significant increase in ketone body levels and a significant decrease in glucose levels in plasma were observed during fasting. Younger children had a faster increase in ketone body levels and a faster decrease in glucose levels in plasma than older children.

CONCLUSIONS

Reference values of the metabolites involved in glucose homeostasis during fasting in children were generated. Those values can be used to determine whether a child has a normal fasting response. For high-risk children, guidelines concerning maximum fasting time and dietary intervention during illness are of the utmost importance.

Safe and unsafe duration of fasting for children with MCAD deficiency

OBJECTIVE

To study the safe and unsafe duration of fasting in children with medium chain acyl-Coenzyme A dehydrogenase (MCAD) deficiency, the literature and the database on Dutch MCAD-deficient patients were searched for data on fasting studies in patients with MCAD deficiency.

MATERIALS AND METHODS

These data were extended with information on fasting studies performed on our patients with MCAD deficiency known in the Beatrix Children's Hospital, UMC Groningen, The Netherlands. The data reflect considerable inter-individual variation and overlap between safe and unsafe duration of fasting.

RESULTS

In six out of 35 fasting tests, symptoms were reported before hypoglycaemia was observed. Until 1 year of age, the median safe and unsafe duration of fasting was 12 hours (n=7, range 8-19 hours) and 18 hours (n=5, range 15-20 hours), respectively. After the first year of life, the median safe and unsafe duration of fasting was 18 hours (n=17, range 10-24 hours) and 20 hours (n=9, range 13-32 hours), respectively.

CONCLUSION

Therefore, to conclude, we recommend a maximum duration of fasting in children with MCAD deficiency of 8 hours between 6 months and 1 year of age, 10 hours in the second year of life and 12 hours thereafter. From this study, no conclusions can be drawn on the duration of fasting during situations of intercurrent illness, especially with fever.

Sweet dreams?--nocturnal hypoglycemia in children with type 1 diabetes

Hypoglycemia is an inevitable consequence of the treatment of type 1 diabetes in childhood. Nocturnal hypoglycemia is often considered as merely the submerged part of this serious complication yet there are reasons to believe that hypoglycemia occurring during sleep may be different in physiological terms. Glucose homeostasis during fasting, delayed effects of exercise and alterations in sleep physiology, itself, may not only affect the risk of nocturnal hypoglycemia but may influence the ability to correct glucose concentration as it falls, leading to episodes of hypoglycemia which are both profound and prolonged. The etiology and potential repercussions are incompletely understood and the most appropriate defense remains unclear. A greater understanding of this enigmatic phenomenon is essential before appropriate methods for hypoglycemia avoidance can be developed.

Preanalytical and analytical factors affecting laboratory results

The results of laboratory tests have a substantial role in the diagnostics of diseases. However, laboratory results do not always correspond with the patient's clinical status. They may be unexpected and surprising. On the other hand, an abnormal laboratory result may be accepted as such and interpreted as a sign of a disease. However, an abnormal result may result from several factors other than disease. Conventionally, these interfering factors have been divided into preanalytical and analytical factors and furthermore into factors acting in vivo and in vitro. The list of these factors is long and laborious to bear in mind. In this review we focus on the factors which, in practice, most often affect laboratory results in healthy individuals and which explain an unexpected result.

Hypoglycaemia: principles of diagnosis and treatment in children

The diagnostic approach to children with suspected hypoglycaemia is facilitated by the fact that two clinically distinct groups exist with little overlap: 1. Hypoglycaemias characterized by a fuel deficit only. 2. Hypoglycaemias in which the fuel deficit is overshadowed by symptoms of intoxication. This differentiation is used when taking the medical history, performing the physical examination, and planning the laboratory investigations. The latter may encompass tolerance tests, a fasting test or the use of a non-radioactive glucose isotope. Protocols for such tests are given.

Problems with the biochemical diagnosis in mitochondrial (encephalo-)myopathies

Patients suffering from a mitochondrial (encephalo-)myopathy have a remarkable clinical heterogeneity. A reliable and extensive investigation must be performed in order to obtain a correct diagnosis, but many factors may influence the ultimate results of these investigations leading, under certain circumstances, to an incorrect diagnosis. Patients selection is of crucial importance. Metabolic examination of body fluids, particularly with respect to lactate accumulation, is used as a selection criterion for further examinations. Numerous aspects associated with this metabolic examination have been critically evaluated, including the phenomenon of other causes of lactic acidaemia apart from mitochondrial disorders. Correct performance of in vivo function tests may contribute to a reduction of the number of missed diagnoses. Selection of the controls for biochemical investigations must be accurately be performed to obtain reliable reference values. Knowledge of the age-dependency of the biochemical parameters is necessary for a correct interpretation. It goes without saying that the choice of the tissue for biochemical investigations is of utmost importance. Knowledge of the tissue-specific occurrence of some defects in the mitochondrial respiratory chain is necessary. The biochemical examinations can be performed both in biopsy and autopsy material but only under certain conditions. Diagnostic approach requires application of reliable biochemical methods which are described. One of the most intriguing aspects in the diagnosis of mitochondrial disorders is the significance of a defect in relation to the residual enzyme activity found in the patient. Moreover, attention is paid to relevant items such as the occurrence of multiple and secondary defects.(ABSTRACT TRUNCATED AT 250 WORDS)

The fasting test in paediatrics: application to the diagnosis of pathological hypo- and hyperketotic states

A 24-h fasting test was performed in 48 control children, in 9 hypoketotic patients with inherited defects of fatty acid oxidation and in 2 hyperketotic patients with inherited defects of ketolysis. The control group was then divided into three age groups on the basis of different adaptation to fasting. Concentrations of blood glucose, lactate, free fatty acids (FFA), 3-hydroxybutyrate, acetoacetate and carnitine were measured after 15 h, 20 h and 24 h of fasting. Significant negative correlations were found in the control group between plasma total ketone bodies (KB) and plasma glucose (P less than 0.001), plasma carnitine (P less than 0.005) and the amplitude of glycaemic response to glucagon at the end of the fast (P less than 0.01). FFA/KB ratio and the product of final fasting values of glucose and ketones were useful to differentiate between hypoketotic or hyperketotic patients and normal subjects. In children with a suspected or definite hyperketotic or hypoketotic disorder, a fasting test must only be performed in healthy patients, in good nutritional condition with non-diagnostic basal biochemical investigations. Carefully supervised fasting should be continued sufficiently to allow ketogenesis and ketolysis to become activated.

Hypoglycemia during diarrhea in childhood. Prevalence, pathophysiology, and outcome

To determine the frequency and outcome of hypoglycemia during diarrhea in childhood, we screened 2003 consecutive patients less than 15 years of age who were admitted to a diarrhea treatment center in Dhaka, Bangladesh. Hypoglycemia, defined as a blood glucose concentration less than 2.2 mmol per liter, was found in 91 patients (4.5 percent), 39 (42.9 percent) of whom died. We also measured the plasma concentrations of glucoregulatory hormones and gluconeogenetic substrates in 46 of the patients with hypoglycemia who were 2 to 15 years old and in 25 normoglycemic patients matched with them for age and weight. The patients with hypoglycemia had had diarrhea for less time than the normoglycemic patients (median, 12 vs. 72 hours; P less than 0.05), and their last feeding had been 18 hours before admission, as compared with 9 hours for the normoglycemic patients (P less than 0.05). The groups were similar in terms of nutritional status, the proportion of patients who had fever, and the types of pathogens recovered from stool samples. The plasma C-peptide concentrations were low (less than 0.30 nmol per liter) in all the hypoglycemic patients. As compared with the normoglycemic patients, the patients with hypoglycemia had elevated median plasma concentrations of glucagon (44 vs. 11 pmol per liter; P = 0.001), epinephrine (3400 vs. 1500 pmol per liter; P = 0.012), norepinephrine (7500 vs. 2900 pmol per liter; P = 0.002), and lactate (3.5 vs. 2.1 mmol per liter; P = 0.020) and similar alanine and beta-hydroxybutyrate concentrations. Eighteen hypoglycemic patients with severe malnutrition had been ill longer than 26 better-nourished patients with hypoglycemia (median duration of illness, 18 vs. 10 hours; P = 0.023) and had lower median plasma concentrations of lactate (1.9 vs. 3.9 mmol per liter; P = 0.021) and alanine (173 vs. 293 micromol per liter; P = 0.040). We conclude that hypoglycemia is a major cause of death in association with diarrhea. Because the glucose counterregulatory hormones were appropriately elevated in the children with diarrhea and hypoglycemia, whereas the gluconeogenetic substrates were inappropriately low, we further conclude that the hypoglycemia observed in such patients is most often due to the failure of gluconeogenesis.

Pyruvate metabolism in Lafora disease

Lafora disease is an autosomal recessive and progressive degenerative disorder of the central nervous system (CNS). The pathogenic mechanism has been presumed to be an inborn error of carbohydrate metabolism, although this has never been proved. In a case of proven Lafora disease, pyruvate metabolism, which has a central position in carbohydrate metabolism, was studied in body fluids under various conditions and in brain biopsy material. No abnormalities in this metabolic pathway were found. This finding plus earlier reports in the literature exclude a defect in glycolysis; thus, a disturbance of carbohydrate metabolism as the pathogenic mechanism of Lafora disease is unlikely.

CSF concentration and CSF/blood ratio of fuel related components in children after prolonged fasting

In order to obtain information about blood and cerebrospinal fluid (CSF) concentrations, and CSF/blood ratio data of fuel related substrates at the end of a prolonged fast in children, we have selected biochemical data from fasting test procedures in 11 control children aged 3-5 yr, fasted 24 h, and 58 control children aged 6-15 yr, fasted 40 h. There was a good correlation between blood and CSF concentrations for glucose, acetoacetate and beta-hydroxybutyrate. The relation with age and sex has been analyzed only in the older children. CSF and blood values for glucose are positively related with age, and both ketones are negatively related with age. Lactate, pyruvate and alanine concentrations in blood and CSF are not related with age, except for CSF pyruvate. With respect to the CSF/blood ratio for the above mentioned components, only the value for acetoacetate is sex and age related. The calculated median caloric values for the sum of glucose, lactate, pyruvate and ketones in CSF are independent of age at the end of a 40-h fast. The diminished glucose contribution on the CSF caloric homeostasis in younger children is fully compensated by the ketone bodies.

Familial Leigh's syndrome: association with a defect in oxidative metabolism probably restricted to brain

Four siblings with Leigh's syndrome are described. The diagnosis was confirmed by pathological examination in one case. Chemical and biochemical investigations of serum and urine revealed no abnormalities of pyruvate metabolism, but all patients had marked elevations of CSF pyruvate and lactate concentrations. In three of the siblings, [1-14C]pyruvate oxidation rates were normal in fibroblasts and leucocytes. In one patients, extensive biochemical and histochemical studies of liver and muscle tissue revealed no mitochondrial dysfunction. A defect of oxidative metabolism restricted to brain seems probable.