Fat-derived fuels during a 24-hour fast 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.

Fasting ketone levels vary by age: implications for differentiating physiologic from pathologic ketotic hypoglycemia

OBJECTIVES

Ketone production is a physiological phenomenon that occurs during beta-oxidation of free fatty acids. Distinguishing physiologic ketosis from pathologic over-production/underutilization of ketones is critical as part of the diagnostic evaluation of disorders of carbohydrate metabolism, but there is limited literature on normal ketone production with fasting. Our aim is to measure fasting serum beta-hydroxybutyrate (BHB) concentrations in healthy children after an overnight fast.

METHODS

Children ≤18 years of age were prospectively recruited from elective procedures through our surgery centers. Exclusion criteria included a history of diabetes, hypopituitarism, adrenal, metabolic or inflammatory disorders, dietary restrictions, trauma, or use of medications that might affect blood glucose. Serum glucose, cortisol, and BHB were assessed after an overnight fast.

RESULTS

Data from 94 participants (mean 8.3 ± 5.7 years, 54 % male, 46 % female, were analyzed. Children ≤3 years of age (19) have significantly higher mean (0.40 ± 0.06 mmol/L) and median (0.4, IQR 0.2-0.6 mmol/L) BHB concentrations compared to children >3 years of age (75) with mean (0.21 ± 0.02 mmol/L) and median BHB (0.1, IQR 0.1-0.2 mmol/L) (p<0.0001). Fasting BHB levels of >1.0 mmol/L was rare (2 %, N=2) and 74 % (N=70) of participants had BHB levels <0.3 mmol/L.

CONCLUSIONS

BHB concentrations are significantly higher in young children (≤3 years of age) compared to older children. Fasting BHB levels >1.0 mmol/L are rare within our population and therefore may identify a value above which there may a greater concern for pathologic ketotic hypoglycemia. It is imperative to establish the normative range in children to differentiate physiological from pathological ketotic hypoglycemia.

Severe neuroglycopenic symptoms due to nonketotic hypoglycemia in children with cardio-facio-cutaneous syndrome

Cardio-facio-cutaneous syndrome (CFC) (OMIM 115150) is a congenital disease caused by constitutive activation of the Raf/MEK/ERK signaling cascade. Unlike aspects of morphological anomalies, metabolic functions related to the disease have garnered little attention. We present severe neuroglycopenic symptoms due to nonketotic hypoglycemia in two children with CFC (Case 1, a 4-year-old male with c.389A > G heterozygous variant in MAP2K1; Case 2, a 3-year-old male with c.770A > G heterozygous variant in BRAF). Case 1 exhibited a nonketotic hypoglycemic coma and clustered left-hemispheric convulsions despite receiving infusion therapy, leading to severe sequelae with choreoathetosis. Brain magnetic resonance imaging of Case 1 showed T2-elongation with restricted diffusion on the bilateral basal ganglia and thalamus, with the dominance of the right putamen. Case 2 presented a prolonged generalized seizure as an initial clinical symptom but fully recovered. The presence of growth hormone and cortisol deficiency was ruled out in both cases. Blood spots acylcarnitine profiles excluded the co-occurrence of mitochondrial HMG-CoA synthase deficiency and HMG-CoA lyase deficiency. These cases demonstrate the potential vulnerability to nonketotic hypoglycemia, especially during lipid shortages. As children with CFC frequently have difficulties feeding, we suggest great attention should be paid to the potential risk of severe nonketotic hypoglycemia.

Correlation between blood ketones and exhaled acetone measured with a semiconducting gas sensor

Breath acetone (BrAce) has been reported to be useful for monitoring the pathophysiology of patients with diabetes. However, devices that measure BrAce are expensive, complex and uncommon. The FM-001, originally designed to monitor a marker of weight loss in healthy people, is a device for measuring BrAce. The FM-001 is a loading semiconducting gas sensor that is a simple and reusable device. The aim of this study was to evaluate the correlation between blood total ketone bodies (TKB) and BrAce measured with the FM-001 in patients with diabetes. Furthermore, through evaluation of that correlation, we sought to detect patients at high risk of developing diabetic ketoacidosis (DKA). Thirty-five participants (Age 52 [40-57], T2DM 32, T1DM 3) were enrolled. Scatter plots and linear regression lines relating BrAce to TKB and the correlation coefficients were calculated. Receiver-operating characteristic (ROC) analysis was performed to determine the cut-off for predicting patients prone to DKA. The results showed that BrAce strongly correlates with TKB (R=0.828), and the correlation was stronger in patients whose serum C-peptide was not low. The optimal BrAce cut-off for predicting risk of developing DKA was 3,400 ppb (AUC 0.924, sensitivity 73.3%, specificity 100%), which corresponds to a TKB ≥ 1,000 µmol/L. BrAce also weakly correlated with free fatty acid. Thus, BrAce levels measured with the FM-001 strongly correlate with TKB, even in patients with diabetes. This suggests the FM-001 is a simple and potentially useful method for detecting diabetic ketosis. (UMIN-ID: UMIN000038086).

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.

Capillary Blood Ketone Levels as an Indicator of Inadequate Breast Milk Intake in the Early Neonatal Period

OBJECTIVE

To determine the utility of capillary blood ketone levels as an indicator of inadequate intake of breast milk in the early postnatal period.

STUDY DESIGN

Levels of capillary blood beta-hydroxybutyrate (βOHB), the main ketone body in the blood, were measured with a bedside ketone meter in 585 full-term neonates aged 48-95 hours who were breastfed exclusively. Relationships between weight-loss percentage, blood sodium, glucose, pH, partial pressure of carbon dioxide, base-deficit levels, and βOHB levels were investigated. The diagnostic accuracy of βOHB for predicting excessive weight loss (weight loss ≥10% of birth weight) and hypernatremic dehydration (blood sodium level ≥150 mEq/L) was determined.

RESULTS

βOHB levels were correlated positively with weight-loss percentage and blood sodium levels and were correlated negatively with blood glucose levels. The diagnostic accuracy of βOHB was 0.846 (optimal cut off, 1.55 mmol/L; sensitivity, 80.9%, specificity, 74.0%) for predicting excessive weight loss and 0.868 (optimal cut off, 1.85 mmol/L; sensitivity, 94.3%; specificity, 69.9%) for predicting hypernatremic dehydration according to the area under the receiver operating characteristic curve. Multiple logistic analysis revealed that βOHB and weight loss percentage were the only independent predictors of hypernatremic dehydration. Increases in βOHB levels also were associated with worsening metabolic acidosis and hypocapnia.

CONCLUSION

High βOHB levels were associated with inadequate intake of breast milk in the early postnatal period. The use of bedside capillary blood ketone levels may be clinically useful as an indicator of dehydration, energy depletion, and acid-base imbalance in breastfeeding infants in the early postnatal period.

Lacticacidosis after short-term infusion of propofol for anaesthesia in a child with osteogenesis imperfecta

We describe the case of a 7-year-old boy with osteogenesis imperfecta, who underwent anaesthesia with propofol-fentanyl-nitrous oxide-suxamethonium for orthopaedic surgery of a distal femur fracture. He developed lacticacidosis after short-term propofol infusion (150 min, mean infusion rate 13.5 mg.kg-1.h-1) associated with a prolonged recovery time without serious haemodynamic changes. The highest lactate concentration was 9.2 mmol.l-1 at 160 min after discontinuation of propofol. There was no significant increase in body temperature. The boy fully recovered.

Oral beta-hydroxybutyrate supplementation in two patients with hyperinsulinemic hypoglycemia: monitoring of beta-hydroxybutyrate levels in blood and cerebrospinal fluid, and in the brain by in vivo magnetic resonance spectroscopy

In persistent hyperinsulinemic hypoglycemia of infancy, ketone body concentrations are abnormally low at times of hypoglycemia, depriving the brain of its most important alternative fuel. The neuroprotective effect of endogenous ketone bodies is evidenced by animal and human studies, but knowledge about exogenous supply is limited. Assuming that exogenous ketone body compounds as a dietetic food might replace this alternative energy source for the brain, we have monitored the fate of orally supplemented DL sodium beta-hydroxybutyrate (beta-OHB) in two 6-mo-old infants with persistent hyperinsulinemic hypoglycemia for 5 and 7 mo, while on frequent tube-feedings and treatment with octreotide. Near total (95%) pancreatectomy had been ineffective in one patient and was refused in the other. In blood, concentrations of beta-OHB increased to levels comparable to a 16- to 24-h fast while on DL sodium beta-OHB 880 to 1000 mg/kg per day. In cerebrospinal fluid, concentrations of beta-OHB increased to levels comparable to a 24- to 40-h fast, after single dosages of 4 and 8 g, respectively. High ratios of beta-OHB to acetoacetate indicated exogenous origin of beta-OHB. An increase of intracerebral concentrations of beta-OHB could be demonstrated by repetitive single-voxel proton magnetic resonance spectroscopy by a clear doublet at 1.25 ppm. Oral DL sodium beta-OHB was tolerated without side effects. This first report on oral supplementation of DL sodium beta-OHB in two patients with persistent hyperinsulinemic hypoglycemia demonstrates effective uptake across the blood-brain barrier and could provide the basis for further evaluation of the neuroprotective effect of beta-OHB in conditions with hypoketotic hypoglycemia.

Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes

Ketone bodies are produced by the liver and used peripherally as an energy source when glucose is not readily available. The two main ketone bodies are acetoacetate (AcAc) and 3-beta-hydroxybutyrate (3HB), while acetone is the third, and least abundant, ketone body. Ketones are always present in the blood and their levels increase during fasting and prolonged exercise. They are also found in the blood of neonates and pregnant women. Diabetes is the most common pathological cause of elevated blood ketones. In diabetic ketoacidosis (DKA), high levels of ketones are produced in response to low insulin levels and high levels of counterregulatory hormones. In acute DKA, the ketone body ratio (3HB:AcAc) rises from normal (1:1) to as high as 10:1. In response to insulin therapy, 3HB levels commonly decrease long before AcAc levels. The frequently employed nitroprusside test only detects AcAc in blood and urine. This test is inconvenient, does not assess the best indicator of ketone body levels (3HB), provides only a semiquantitative assessment of ketone levels and is associated with false-positive results. Recently, inexpensive quantitative tests of 3HB levels have become available for use with small blood samples (5-25 microl). These tests offer new options for monitoring and treating diabetes and other states characterized by the abnormal metabolism of ketone bodies.

Tolerance to starvation in children on long-term total parenteral nutrition

To evaluate the consequences of long-term cyclic total parenteral nutrition (TPN) on metabolic pathways which contribute to energy metabolism, adaptation to starvation was studied in a group of seven children 2-7 years old, on long-term cyclic TPN. In addition to clinical monitoring, the following biological parameters were measured: blood levels of glucose, free fatty acids, ketone bodies and carnitine, and urinary excretion of dicarboxylic acids. Five of the seven children had good clinical tolerance up to 30 h of fasting. This indicated that metabolic changes arising from prolonged cyclic TPN are easily reversed when such children are fasting. The other two children had to be refed after 22 and 24 h, respectively. Both had metabolic signs of impaired hepatic fatty acid oxidation or ketogenesis. These metabolic changes might reflect the liver failure caused by TPN in these children, and stresses the fact that prolonged starvation has to be carefully monitored in patients with liver dysfunction secondary to TPN.

Evaluation of fasts for investigating hypoglycaemia or suspected metabolic disease

AIM

To assess the value and safety of fasts for investigating hypoglycaemia or suspected metabolic disease.

STUDY DESIGN

Review of all diagnostic fasts performed over a 2.5 year period.

SETTING

The neonatal intensive care unit and programmed investigation unit at a tertiary referral centre for endocrinology and metabolic disease.

RESULTS

138 diagnostic fasts were performed during the study period. Hypoglycaemia (< 2.6 mmol/l) occurred in 54 cases but in only four did the blood glucose concentration fall below 1.5 mmol/l. One patient became unwell as a result of a fast, but prompt treatment averted any sequelae. Specific endocrine or metabolic defects were identified in 30 cases, the most common being hyperinsulinism and beta-oxidation defects.

CONCLUSIONS

Fasting is safe if conducted on an experienced unit with appropriate guidelines. It continues to provide useful information for diagnosis and management, particularly in cases of hyperinsulinism. Diagnoses should, however, be established by lower risk procedures whenever possible. Thus specimens for metabolic and endocrine studies should be obtained during the presenting episode and blood acylcarnitine species should be analysed prior to fasting.

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.

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.

Hypoglycemia: a pathophysiologic approach

An exploration of the factors that sustain glucose levels in the normal fasting subject reveals that the single major component is conservation of glucose rather than gluconeogenesis. Conservation is achieved by recycling of glucose carbon as lactate, pyruvate and alanine, and a profound decrease in the oxidation of glucose by the brain brought about by the provision and use of ketones. What glucose continues to be oxidized is for the most part formed from glycerol. Gluconeogenesis from protein plays little part in the process. Fasting hypoglycemia results from disorders affecting either one of the two critical sustaining factors--the recycling process or the availability and use of ketones. Individual hypoglycemic entities are examined against this background.

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.

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

In order to study the relationship between sex, age and glucose, and the concentrations of various fuel related blood substrates in children during prolonged fasting, we have selected data of fasting procedures in 13 control children aged 3-5 yr, fasted 24 h, and 58 control children aged 6-15 yr, fasted 40 h. Compared to the blood results after overnight fast, glucose is decreased, and lactate, pyruvate, ketones and non-esterified fatty acids (NEFA's) are all clearly increased at the end of fast. The concentrations of alanine and triglycerides remain unchanged. The relation with sex, age and glucose has only been analyzed in the older children group. A sex-dependency is indicated for the ketones. Ketones are negatively related with age. NEFA's pyruvate and alanine are not age-related, whereas glucose, lactate and triglycerides are moderately age-dependent. Ketones are negatively related with glucose, whereas pyruvate, NEFA's and triglycerides are not glucose-related. Lactate and alanine are weakly related to glucose. The data demonstrate diminished glucose homeostasis and increased ketogenesis in younger children compared to older ones during prolonged fasting.

Reference values of blood components related to fuel metabolism in children after an overnight fast

The interrelation between blood components, involved in fuel metabolism, and age, sex and glucose was studied in 72 control children (26 girls and 46 boys, aged between 3 and 15 yr) after an overnight fast (14 h). Glucose, lactate, pyruvate, triglycerides and cholesterol are age-independent. Alanine is positively correlated, whereas beta-hydroxybutyrate, acetoacetate and NEFA's are negatively correlated with age. With respect to blood sugar, acetoacetate, NEFA's and cholesterol are glucose-independent. Lactate, pyruvate, alanine and triglycerides are positively correlated with glucose, and beta-hydroxybutyrate--and total ketone bodies--are negatively correlated with glucose. Except for triglycerides, no differences in the concentrations of the above mentioned blood substrates are seen between boys and girls. These data demonstrate that after an overnight fast lipolysis and ketogenesis already are active in young children, probably related to inadequate gluconeogenesis and improvement of carbohydrate regulation with age.

Hypoketonemia and age-related fasting hypoglycemia in growth hormone deficiency

Body fuels were measured in 45 normal children and 17 growth hormone-deficient patients after 24 hours of fasting. After three months of therapy with human Growth Hormone (hGH) 16 of the patients were restudied. In all groups, beta-hydroxybutyrate (BOHB) concentrations correlated inversely with age and with glucose concentrations. When adjusted for these factors, the concentrations of BOHB were significantly lower in the growth hormone-deficient patients than in the control children, before (P less than 0.01) as well as after therapy (P less than 0.01). Only the five youngest patients became hypoglycemic. During fasting, ketones, which serve as an alternative fuel for the brain, spare glucose. Thus, a shortage of ketones would compromise the ability of the patient to conserve glucose and predispose the patient to fasting hypoglycemia. Accordingly, we propose that hypoketonemia is a critical factor in the genesis of fasting hypoglycemia in growth hormone deficiency.