Red blood cells as glucose carriers to the human brain: Modulation of cerebral activity by erythrocyte exchange transfusion in Glut1 deficiency (G1D)

Red blood cells circulating through the brain are briefly but closely apposed to the capillary endothelium. We hypothesized that this contact provides a nearly direct pathway for metabolic substrate transfer to neural cells that complements the better characterized plasma to endothelium transfer. While brain function is considered independent of normal fluctuations in blood glucose concentration, this is not borne out by persons with glucose transporter I (GLUT1) deficiency (G1D). In them, encephalopathy is often ameliorated by meal or carbohydrate administration, and this enabled us to test our hypothesis: Since red blood cells contain glucose, and since the red cells of G1D individuals are also deficient in GLUT1, replacing them with normal donor cells via exchange transfusion could augment erythrocyte to neural cell glucose transport via mass action in the setting of unaltered erythrocyte count or plasma glucose abundance. This motivated us to perform red blood cell exchange in 3 G1D persons. There were rapid, favorable and unprecedented changes in cognitive, electroencephalographic and quality-of-life measures. The hypothesized transfer mechanism was further substantiated by in vitro measurement of direct erythrocyte to endothelial cell glucose flux. The results also indicate that the adult intellect is capable of significant enhancement without deliberate practice.      ClinicalTrials.gov registration: NCT04137692 https://clinicaltrials.gov/ct2/show/NCT04137692.

Exogenous Ketone Supplements Improved Motor Performance in Preclinical Rodent Models

Nutritional ketosis has been proven effective for neurometabolic conditions and disorders linked to metabolic dysregulation. While inducing nutritional ketosis, ketogenic diet (KD) can improve motor performance in the context of certain disease states, but it is unknown whether exogenous ketone supplements—alternatives to KDs—may have similar effects. Therefore, we investigated the effect of ketone supplements on motor performance, using accelerating rotarod test and on postexercise blood glucose and R-beta-hydroxybutyrate (R-βHB) levels in rodent models with and without pathology. The effect of KD, butanediol (BD), ketone-ester (KE), ketone-salt (KS), and their combination (KE + KS: KEKS) or mixtures with medium chain triglyceride (MCT) (KE + MCT: KEMCT; KS + MCT: KSMCT) was tested in Sprague-Dawley (SPD) and WAG/Rij (WR) rats and in GLUT-1 Deficiency Syndrome (G1D) mice. Motor performance was enhanced by KEMCT acutely, KE and KS subchronically in SPD rats, by KEKS and KEMCT groups in WR rats, and by KE chronically in G1D mice. We demonstrated that exogenous ketone supplementation improved motor performance to various degrees in rodent models, while effectively elevated R-βHB and in some cases offsets postexercise blood glucose elevations. Our results suggest that improvement of motor performance varies depending on the strain of rodents, specific ketone formulation, age, and exposure frequency.

Exogenous Ketones Lower Blood Glucose Level in Rested and Exercised Rodent Models

Diseases involving inflammation and oxidative stress can be exacerbated by high blood glucose levels. Due to tight metabolic regulation, safely reducing blood glucose can prove difficult. The ketogenic diet (KD) reduces absolute glucose and insulin, while increasing fatty acid oxidation, ketogenesis, and circulating levels of β-hydroxybutyrate (βHB), acetoacetate (AcAc), and acetone. Compliance to KD can be difficult, so alternative therapies that help reduce glucose levels are needed. Exogenous ketones provide an alternative method to elevate blood ketone levels without strict dietary requirements. In this study, we tested the changes in blood glucose and ketone (βHB) levels in response to acute, sub-chronic, and chronic administration of various ketogenic compounds in either a post-exercise or rested state. WAG/Rij (WR) rats, a rodent model of human absence epilepsy, GLUT1 deficiency syndrome mice (GLUT1D), and wild type Sprague Dawley rats (SPD) were assessed. Non-pathological animals were also assessed across different age ranges. Experimental groups included KD, standard diet (SD) supplemented with water (Control, C) or with exogenous ketones: 1, 3-butanediol (BD), βHB mineral salt (KS), KS with medium chain triglyceride/MCT (KSMCT), BD acetoacetate diester (KE), KE with MCT (KEMCT), and KE with KS (KEKS). In rested WR rats, the KE, KS, KSMCT groups had lower blood glucose level after 1 h of treatment, and in KE and KSMCT groups after 24 h. After exercise, the KE, KSMCT, KEKS, and KEMCT groups had lowered glucose levels after 1 h, and in the KEKS and KEMCT groups after 7 days, compared to control. In GLUT1D mice without exercise, only KE resulted in significantly lower glucose levels at week 2 and week 6 during a 10 weeks long chronic feeding study. In 4-month and 1-year-old SPD rats in the post-exercise trials, blood glucose was significantly lower in KD and KE, and in KEMCT groups, respectively. After seven days, the KSMCT group had the most significantly reduced blood glucose levels, compared to control. These results indicate that exogenous ketones were efficacious in reducing blood glucose levels within and outside the context of exercise in various rodent models of different ages, with and without pathology.

Association of lymphocytic colitis and lactase deficiency in pediatric population

Characterized by colonic mucosa intraepithelial lymphocytosis, lymphocytic colitis is primarily an entity presented in the middle-aged to elderly patient population. Very few large series of lymphocytic colitis of childhood occurrence are available in the medical literature. Ten cases each of lymphocytic colitis and of colonic lymphocytosis of other diagnosis, all with duodenal disaccharidases analysis data, were collected from the files of our institution. The electronic medical records were reviewed and multiple variables were analyzed. The ten patients with lymphocytic colitis presented with diarrhea. Of these, three had abdominal pain. The age range was 2-18 years. Nearly all patients were Caucasian (90%) and 70% were female. Endoscopically, most had normal appearing colonic mucosa. Significant past medical history, family medical history and associated comorbidities included celiac disease, Down syndrome, juvenile arthritis and other autoimmune diseases. Interestingly, the most revealing observation was that the majority of cases (80%) were associated with lactase deficiency and, for the most part, gastrointestinal symptoms improved simply by treatment with Lactaid or avoidance of dairy products. This association is statistically significant. Our clinicopathological study indicates that the typical pediatric patient is a female Caucasian. A large of portion of the patients had associated lactase deficiency and improved on Lactaid supplement alone.

[Clinical and genetic characteristics of glucose transporter type 1 deficiency syndrome]

OBJECTIVE

To analyze the clinical and SLC2A1 gene mutation characteristics of glucose transporter type 1 deficiency syndrome.

METHOD

The detailed clinical manifestations of six cases were recorded. The laboratory tests including EEG, MRI, blood chemistry, and lumbar puncture were performed. SLC2A1 gene mutations were analyzed by PCR, DNA sequencing and multiplex ligation-dependent probe amplification (MLPA).

RESULT

Patient 1, 2 and 3 had classical clinical symptoms including infantile onset seizures, development delay. Patient 4, 5 and 6 had non-classical clinical symptoms including paroxysmal behavior disturbance, weakness, ataxia, lethargy, especially after fasting or exercise, without severe seizures. The plasma glucose levels were normal. The CSF glucose levels decreased in all the six cases, ranged from 1.10 mmol/L to 2.45 mmol/L, the mean level was 1.68 mmol/L. The CSF glucose/plasma glucose ratios decreased, ranged from 0.16 to 0.51, the mean ratio was 0.34. Four patients had normal EEG. Two patients had focal and diffuse epileptiform discharge, and one of them also had paroxysmal occipital or generalized high-amplitude slow waves during awake and sleep time. MRI abnormalities were found in three patients, patient 1 with mild brain atrophy, patient 3 with bilateral ventricle plump, and patient 4 with high signals in T2 in the frontal and occipital white matter, interpreted as hypomyelination. SLC2A1 gene mutations were found in six cases. Patient 1 has large scale deletion in exon 2. In patient 2 to 6, the mutations were c.741 G>A (E247K), 599delA, 761delA, c.1148 C>A (P383H), c.1198 C>T (R400C) respectively. Two patients were treated with ketogenic diet. The seizures disappeared and development became normal. Three patients responded to frequent meals with snacks. One patient refused any treatments, the symptoms continued to exist.

CONCLUSION

The clinical manifestations of glucose transporter type 1 deficiency syndrome are varied. The common symptoms included infantile onset seizures and various paroxysmal events. These neurologic symptoms generally fluctuated and were influenced by factors such as fasting or fatigue. This feature could be a very important clue for the diagnosis of GLUT1-DS. Lumbar puncture is recommended in patients with episodic CNS symptoms especially after fasting. GLUT1-DS is a treatable neurometabolic disorder, early diagnosis and treatment may improve the prognosis of the patients.

Fructose, trehalose and sorbitol malabsorption

Carbohydrate malabsorption is a frequent clinical condition, often associated with abdominal symptoms. Although lactose represents the most commonly malabsorbed sugar, also other carbohydrates, such as fructose, trehalose and sorbitol may be incorrectly absorbed in the small intestine. Fructose malabsorption seems more common in patients with functional bowel disease, even if randomized and controlled studies on these topic were few and on small samples. Interpretation of breath hydrogen testing is difficult. In particular, neither studies comparing this test with a gold standard, nor validated doses and concentrations to be used, are available. Trehalose malabsorption due to trehalase deficiency represents a very rare condition and available studies do not support its relevance in clinical practice. Sorbitol absorption is dose and concentration related, and depends on the entity of intestinal absorption surface. Nevertheless, the finding of its malabsorption is not expression of a specific cause of intestinal bowel damage. From available data, it is not possible to draw definite conclusions about clinical relevance of fructose, trehalose and sorbitol malabsorption, as well as, about diagnostic accuracy of commonly used tests to detect all these conditions. On the other hand, in patients who refer abdominal discomfort after ingestion of different carbohydrate-containing foods, a small intestinal bacterial overgrowth, should be promptly considered. This is because the large amount of intestinal bacteria may unspecifically ferment sugars, causing an abnormal H2 production and consequently a misleading diagnosis of sugar malabsorption.

The diagnostic difficulties of complex glycerol kinase deficiency

We describe 2 siblings with the contiguous X-linked gene deletion syndrome, complex glycerol kinase deficiency. The elder sibling demonstrated the difficulties diagnosing this rare condition. Affected children have the combined complications of congenital adrenal hypoplasia, Duchenne muscular dystrophy, and glycerol kinase deficiency. These patients illustrate the importance of genetic testing and prepregnancy counseling. In addition, they demonstrate the need for a multidisciplinary team approach in their management.

Towards a therapy for phosphomannomutase 2 deficiency, the defect in CDG-Ia patients

Phosphomannomutase (PMM2, Mannose-6-P--> Mannose-1-P) deficiency is the most frequent glycosylation disorder affecting the N-glycosylation pathway. There is no therapy for the hundreds of patients who suffer from this disorder. This review describes previous attempts at therapeutic interventions and introduces perspectives emerging from the drawing boards. Two approaches aim to increase Mannose-1-P: small membrane permeable molecules that increase the availability or/and metabolic flux of precursors into the impaired glycosylation pathway; and, phosphomannomutase enhancement and/or replacement therapy. Glycosylation-deficient cell and animal models are needed to determine which individual or combined approaches improve glycosylation and may be suitable for preclinical evaluation.

Immunizations for patients with metabolic disorders

Individuals with underlying metabolic disorders are a potential high-risk group for vaccine-preventable diseases. Newborn metabolic screening has provided a means of early identification and treatment for many of these disorders, whereas childhood immunization is one of the most effective means of decreasing the morbidity and mortality resulting from communicable diseases worldwide. There are very few contraindications to the routine administration of vaccines to the healthy, immunocompetent individual. In certain high-risk groups, such as immunocompromised patients, gravid females, and those with a history of previous anaphylactic reaction to a vaccine or its components, selective withholding of immunizations must be considered to decrease potential adverse events. A detailed analysis of the medical literature revealed few specific recommendations regarding appropriate immunization techniques for patients with metabolic disorders. In this review we detail the major metabolic disorder subtypes, elaborate on the available literature on immunizations for patients with these disorders, and provide suggested vaccine recommendations.

Recurrent infections and immunological dysfunction in congenital disorder of glycosylation Ia (CDG Ia)

Congenital disorder of glycosylation Ia is the most common defect of glycosylation and is due to mutations in phosphomannomutase 2. This leads to aberrant N-linked oligosaccharides. The phenotype of CDG Ia reflects the essential nature of glycosylation and patients typically present with multiple organs affected, with hypotonia, developmental delay, inverted nipples and abnormal fat pads. Later features include retinitis pigmentosa, stroke, cerebellar atrophy and malabsorption. Approximately 20% of patients die in the first year of life and infection is the most common cause of death. Immunological function has not previously been investigated in these patients and the critical role of oligosaccharides on adhesion molecules suggested that haematopoietic cell migration and communication could be disrupted by mutations in phosphomannomutase 2. We characterized the clinical features, performed standard immunological evaluations, and performed specific analyses of neutrophil adhesion molecules on two patients to address this question. Patient neutrophils had diminished chemotaxis but expressed comparable levels of adhesion molecules and rolled on artificial endothelium equivalently to control neutrophils. The most significant feature of the patients' immunological function was poor vaccine responses. These two affected patients were begun on intravenous immunoglobulin with some improvement in their infections.

The congenital disorders of glycosylation: a multifaceted group of syndromes

The congenital disorders of glycosylation (CDG) are a rapidly expanding group of metabolic syndromes with a wide symptomatology and severity. They all stem from deficient N-glycosylation of proteins. To date the group contains 18 different subtypes: 12 of Type I (disrupted synthesis of the lipid-linked oligosaccharide precursor) and 6 of Type II (malfunctioning trimming/processing of the protein-bound oligosaccharide). Main features of CDG involve psychomotor retardation; ataxia; seizures; retinopathy; liver fibrosis; coagulopathies; failure to thrive; dysmorphic features, including inverted nipples and subcutaneous fat pads; and strabismus. No treatment currently is available for the vast majority of these syndromes (CDG-Ib and CDG-IIc are exceptions), even though attempts to synthesize drugs for the most common subtype, CDG-Ia, have been made. In this review we will discuss the individual syndromes, with focus on their neuronal involvement, available and possible treatments, and future directions.

Stabilization of hypoglycosylation in a patient with congenital disorder of glycosylation type Ia

A follow-up over 7 years on a patient with congenital disorder of glycosylation type Ia showed a significant normalization of hypoglycosylated transferrin. Isoelectric focusing for serum transferrin is a widely used screening method but there could be a limit of detection and the subtle changes can be also overlooked. Re-test with a different method is desirable, especially when the clinical suspicion for congenital disorder of glycosylation is high.

GLUT1 deficiency and other glucose transporter diseases

We review the three genetically determined disorders of glucose transport across cell membranes. Diseases such as glucose-galactose malabsorption, Fanconi-Bickel syndrome and De Vivo disease (GLUT1 deficiency syndrome (GLUT1DS)) arise from heritable mutations in transporter-encoding genes that impair monosaccharide uptake, which becomes rate-limiting in tissues where the transporters serve as the main glucose carrier systems. We focus in greater detail on De Vivo disease as a prototype of a brain energy failure syndrome, for which the greatest pathophysiological detail is known, but which presents the most therapeutic challenges. The study of these diseases illustrates fundamental aspects of energetic metabolism, while providing the basis for their diagnosis by simple metabolic screening and for their treatment by dietary modification.

Hematopoietic cell transplantation for inherited metabolic diseases: an overview of outcomes and practice guidelines

For the past two decades, hematopoietic cell transplantation (HCT) has been used as effective therapy for selected inherited metabolic diseases (IMD) including Hurler (MPS IH) and Maroteaux-Lamy (MPS VI) syndromes, childhood-onset cerebral X-linked adrenoleukodystrophy (X-ALD), globoid-cell leukodystrophy (GLD), metachromatic leukodystrophy (MLD), alpha-mannosidosis, osteopetrosis, and others. Careful pre-HCT evaluation is critical and coordinated, multidisciplinary follow-up is essential in this field of transplantation. The primary goals of HCT for these disorders have been to promote long-term survival with donor-derived engraftment and to optimize the quality of life. Guidelines for HCT and monitoring are provided; a brief overview of long-term results is also presented.

American Academy of Pediatrics. Committee on Nutrition. Soy protein-based formulas: recommendations for use in infant feeding

The American Academy of Pediatrics is committed to the use of maternal breast milk as the ideal source of nutrition for infant feeding. Even so, by 2 months of age, most infants in North America are formula-fed. Despite limited indications, the use of soy protein-based formula has nearly doubled during the past decade to achieve 25% of the market in the United States. Because an infant formula provides the largest, if not sole, source of nutrition for an extended interval, the nutritional adequacy of the formula must be confirmed and the indications for its use well understood. This statement updates the 1983 Committee on Nutrition review and contains some important recommendations on the appropriate use of soy protein-based formulas.

Disorders of gluconeogenesis

Gluconeogenesis, or the formation of glucose from mainly lactate/ pyruvate, glycerol and alanine, plays an essential role in the maintenance of normoglycaemia during fasting. Inborn deficiencies are known of each of the four enzymes of the glycolytic-gluconeogenic pathway that ensure a unidirectional flux from pyruvate to glucose: pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase, and glucose-6-phosphatase. In this paper, the clinical picture, pathophysiology, diagnostic tests, genetics, treatment and prognosis of the deficiencies of fructose-1,6-bisphosphatase and phosphoenolpyruvate carboxykinase are reviewed.

[Therapy of metabolic myopathies]

Metabolic myopathies are subdivided into disturbances of anaerobic cytoplasmic and aerobic mitochondrial metabolism. With the exception of carnitine deficiency these myopathies are based on enzymopathies. Since gene therapy is not yet available no causal therapy is possible. This paper discusses possibilities for symptomatic therapy. Good results are found with carnitine substitution. Enzymopathies can be improved by using other metabolic pathways or by addition of co-factors of the impaired pathways. This leads to a reduction of myalgia, cramps, and endurance exercise intolerance.

Inborn errors of organic acid metabolism

Organic acid disorders are an important group of inborn errors which present in the neonatal period or early infancy and are associated with high morbidity and mortality. Some of these disorders respond well to treatment, and others can be diagnosed in utero.

Enzyme-substitution therapy with the yeast Saccharomyces cerevisiae in congenital sucrase-isomaltase deficiency

Sucrase-isomaltase deficiency is an inherited disaccharidase deficiency that leads to malabsorption of sucrose, with resulting diarrhea and abdominal distention and cramps. We investigated the sucrose-splitting effect of viable yeast cells in eight children with congenital sucrase-isomaltase deficiency, by means of the sucrose hydrogen breath test. This test is based on the fact that hydrogen is released from the malabsorbed sucrose by the colonic microflora. We found that 0.3 g of lyophilized Saccharomyces cerevisiae, given after loading with 2 g of sucrose per kilogram of body weight, reduced hydrogen excretion in all patients, on average by 70 percent, in parallel with a complete loss or evident reduction of clinical symptoms. In vitro, lyophilized and fresh S. cerevisiae (fresh baker's yeast) had appreciable sucrase activity, a low isomaltase and maltase activity, and virtually no lactase activity. The sucrase activity was more inhibited by undiluted than by diluted gastric juice. We conclude that patients with congenital sucrase-isomaltase deficiency who intentionally or unintentionally consume sucrose can ameliorate the malabsorption by subsequently ingesting a small amount of viable yeast cells, preferably on a full stomach.

Parenteral galactose therapy in the glucose-intolerant premature infant

Blood galactose concentrations were measured in 55 neonates consuming at least 80 ml/kg/day of lactose-containing formula. The range of galactose concentration immediately after feeding was 0.8 to 4.2 mg/dl, with a mean of 1.5 +/- 0.2 mg/dl. Galactose concentration fell rapidly after feeding, and normal values for the population fell with a half-life of 45 minutes. Considering galactose as a potential intravenous nutrient, six glucose-intolerant premature infants were given galactose-containing solutions intravenously using a double-blind randomized crossover protocol. Infants were chosen who had sustained hyperglycemia (150 mg/dl) and glucosuria (2+ Clinitest) requiring glucose infusion at a rate below 7 mg/kg/minute for more than 24 hours. Compared to the control glucose period, intravenous alimentation with a solution containing carbohydrate as 50% glucose and 50% galactose resulted in a 65% increase in total carbohydrate infusion rate, normalization of the blood glucose concentration, and decreased glucosuria. Blood galactose concentration averaged 15 mg/dl, and no clinical or biochemical evidence of galactose toxicity was noted.

[Parenteral feeding of infants with prolonged diarrhea and intolerance to monosaccharides]

The study in 14 patients with severe and protracted infectious gastroenteritis is reported. In all cases, intolerance to monosaccharides was present and in 13 cases, third degree malnutrition was evident. The period of evolution of the diarrhea was, as an average, 67.6 days at the moment when parenteral feeding was initiated. Eight of the cases had shown sepsis, intestinal pneumatosis and hypoglycemia in six and gastrointestinal hemorrhage was found in another six patients. They were managed with parenteral feeding for an average period of 21.5 days, during which, they gained an average of 14.6 g/day. Six episodes of sepsis were seen during the procedure, but in no case did it follow infection through the central catheter. Four of the patients died, but in no case was there any direct relationship to the procedure. In this type of severely ill patients with protracted diarrhea, parenteral feeding is a resource that allows the defunctionalization of the intestine and recovery of these patients.

[Severe metabolic diseases in neonates. Diagnosis and treatment (author's transl)]

Life-threatening diseases in the newborn period might be due to rare inborn errors of metabolism. Clincal symptoms, diagnostic approach and therapy are outlined in some inherited diseases of amino acid-, carbohydrate and organic acid metabolism. A proposual for initial management in a suspected case is made.