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Interest in human and experimental animal metabolism of substrates containing an odd number of carbons capable of fueling the tricarboxylic acid cycle such as heptanoic acid has motivated us to develop and validate a selective and specific liquid chromatographytandem mass spectrometric method for the simultaneous, quantitative determination of the ketone body byproducts 3-hydroxypentanoic acid and 3-oxopentanoic acid in plasma. Human plasma samples were protein-precipitated with methanol containing 0.2% formic acid. Chromatographic resolution was achieved on a Phenomenex Luna C18 column using gradient elution with mobile phases of water containing 0.1% formic acid and methanol containing 0.1% formic acid at 0.3 mL/min flow rate. The retention times of 3-hydroxypentanoic acid, 3-oxopentanoic acid and sulbactam (internal standard) were 3.85, 4.23, and 5.11 min, respectively. Validation was conducted in accordance with United States Food and Drug Administration guidance. The validated range of 3-hydroxypentanoic acid was 0.078-5 µg/mL and 0.156-10 µg/mL for 3-oxopentanoic acid. The method was accurate and precise over this range and exhibited 10-fold dilution integrity in human plasma. Recovery> 88% was achieved for analytes and internal standard. There was no matrix effect observed in human plasma. Both 3-hydroxypentanoic acid and 3-oxopentanoic acid were stable across conditions including autosampler, benchtop and freeze-thaw, as well as demonstrated long-term stability at -80 °C. The method was applied to the measurement of 3-hydroxypentanoic acid and 3-oxopentanoic acid concentrations in plasma from subjects receiving the triglyceride triheptanoin (as a source of heptanoate) for the experimental treatment of glucose transporter type I deficiency (G1D) syndrome., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Proteoglycans consist of proteins linked to sulfated glycosaminoglycan chains. They constitute a family of macromolecules mainly involved in the architecture of organs and tissues as major components of extracellular matrices. Some proteoglycans also act as signaling molecules involved in inflammatory response as well as cell proliferation, adhesion, and differentiation. Inborn errors of proteoglycan metabolism are a group of orphan diseases with severe and irreversible skeletal abnormalities associated with multiorgan impairments. Identifying the gene variants that cause these pathologies proves to be difficult because of unspecific clinical symptoms, hardly accessible functional laboratory tests, and a lack of convenient blood biomarkers. In this review, we summarize the molecular pathways of proteoglycan biosynthesis, the associated inherited syndromes, and the related biochemical screening techniques, and we focus especially on a circulating proteoglycan called bikunin and on its potential as a new biomarker of these diseases.

Inborn errors of metabolism (IEM) involving the non-oxidative pentose phosphate pathway (PPP) include the two relatively rare conditions, transketolase deficiency and transaldolase deficiency, both of which can be difficult to diagnosis given their non-specific clinical presentations. Current biochemical testing approaches require an index of suspicion to consider targeted urine polyol testing. To determine whether a broad-spectrum biochemical test could accurately identify a specific metabolic pattern defining IEMs of the non-oxidative PPP, we employed the use of clinical metabolomic profiling as an unbiased novel approach to diagnosis. Subjects with molecularly confirmed IEMs of the PPP were included in this study. Targeted quantitative analysis of polyols in urine and plasma samples was accomplished with chromatography and mass spectrometry. Semi-quantitative unbiased metabolomic analysis of urine and plasma samples was achieved by assessing small molecules via liquid chromatography and high-resolution mass spectrometry. Results from untargeted and targeted analyses were then compared and analyzed for diagnostic acuity. Two siblings with transketolase (TKT) deficiency and three unrelated individuals with transaldolase (TALDO) deficiency were identified for inclusion in the study. For both IEMs, targeted polyol testing and untargeted metabolomic testing on urine and/or plasma samples identified typical perturbations of the respective disorder. Additionally, untargeted metabolomic testing revealed elevations in other PPP metabolites not typically measured with targeted polyol testing, including ribonate, ribose, and erythronate for TKT deficiency and ribonate, erythronate, and sedoheptulose 7-phosphate in TALDO deficiency. Non-PPP alternations were also noted involving tryptophan, purine, and pyrimidine metabolism for both TKT and TALDO deficient patients. Targeted polyol testing and untargeted metabolomic testing methods were both able to identify specific biochemical patterns indicative of TKT and TALDO deficiency in both plasma and urine samples. In addition, untargeted metabolomics was able to identify novel biomarkers, thereby expanding the current knowledge of both conditions and providing further insight into potential underlying pathophysiological mechanisms. Furthermore, untargeted metabolomic testing offers the advantage of having a single effective biochemical screening test for identification of rare IEMs, like TKT and TALDO deficiencies, that may otherwise go undiagnosed due to their generally non-specific clinical presentations., Competing Interests: Declaration of Competing Interest BJS, VRS, QS, JX, and SHE are employees of Baylor College of Medicine. CG is an employee of Baylor Genetics. Baylor Genetics generates genetic testing revenue in a partnership with Baylor College of Medicine. ADK and KLP are employees of Metabolon, Inc. and, as such, have affiliations with or financial involvement with Metabolon, Inc. HTB is a consultant for Millennium Therapeutics. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the article apart from those disclosed., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The effect of intensive insulin therapy on hyperglucagonemia in newly diagnosed type 2 diabetes (T2DM), and its associations with β-cell function, has not been elucidated. This study assessed the effect of 12 weeks of intensive insulin therapy on hyperglucagonemia in newly diagnosed T2DM and its associations with β-cell function, with reference to the effects of 12 weeks of oral hypoglycemic agents (OHAs).One hundred eight patients with newly diagnosed T2DM were enrolled from January 2015 to December 2015. The patients were randomly divided to receive, for 12 weeks, either intensive insulin therapy or OHAs. Meal tolerance tests were conducted at baseline before treatment (0 week), at 12 weeks (end of treatment), and 12 months after the initiation of treatment. The levels of glucagon, proinsulin, C-peptide (CP), and blood glucose were measured at timepoints 0, 30, and 120 minutes during the meal tolerance test.Intensive insulin treatment was associated with a decrease in glucagon levels (at 0, 30, and 120 minutes) and proinsulin/CP, and an increase in the insulin-secretion index ΔCP30/ΔG30 and ΔCP120/ΔG120, at 12 weeks and 12 months during the follow-up, compared with the corresponding effects of OHAs. Intensive insulin therapy could reduce but failed to normalize glucagon levels at 12 weeks. There were no correlations between the change of percentages in total area under the curve of glucagon and other glycemic parameters (proinsulin/CP; ΔCP30/ΔG30; or ΔCP120/ΔG120). Patients who received intensive insulin therapy were more likely to achieve their target glycemic goal and remission, compared with those who received OHAs.Short-term intensive insulin therapy facilitates the improvement of both β-cell and α-cell function in newly diagnosed T2DM mellitus. Decline of β-cell secretion and concomitant α-cell dysfunction may both be involved in the pathogenesis of T2DM.

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., Competing Interests: International Patent # PCT/US2014/031237, University of South Florida for DPD: Compositions and Methods for Producing Elevated and Sustained Ketosis. Patent pending: No. 11001-018-US1 for CA and DPD: Administration of Exogenous Ketone to Lower Blood Glucose”. D.P. D`Agostino and C. Ari are co-owners of the company Ketone Technologies LLC. DMD is a paid consultant and member of the science advisory board for Axcess Global Sciences and Real Ketones. These interests have been reviewed and managed by the University in accordance with its Institutional and Individual Conflict of Interest policies. All authors declare that there are no additional conflicts of interest.

The classical ketogenic diet (cKD) is an isocaloric, high fat, very low-carbohydrate diet that induces ketosis, strongly influencing leptin and ghrelin regulation. However, not enough is known about the impact of a long-term cKD. This study evaluated the effects of a 12-month cKD on ghrelin and leptin concentrations in children, adolescents and adults affected by the GLUT1-Deficiency Syndrome or drug resistant epilepsy (DRE). We also investigated the relationship between the nutritional status, body composition and ghrelin and leptin variations. We carried out a longitudinal study on 30 patients: Twenty-five children and adolescents (15 females, 8 ± 4 years), and five adults (two females, 34 ± 16 years). After 12-monoths cKD, there were no significant changes in ghrelin and leptin, or in the nutritional status, body fat, glucose and lipid profiles. However, a slight height z-score reduction (from -0.603 ± 1.178 to -0.953 ± 1.354, p ≤ 0.001) and a drop in fasting insulin occurred. We found no correlations between ghrelin changes and nutritional status and body composition, whereas leptin changes correlated positively with variations in the weight z-score and body fat ( ρ = 0.4534, p = 0.0341; ρ = 0.5901, p = 0.0135; respectively). These results suggest that a long-term cKD does not change ghrelin and leptin concentrations independently of age and neurological condition.

Glucose transporter type 1 deficiency syndrome (GLUT1DS) causes central nervous system dysfunction including intractable epilepsy caused by impaired glucose transport to the brain. To prevent convulsions and maintain an energy source for the brain in patients with GLUT1DS, the maintenance of adequate ketone body concentrations, compensation of metabolic acidosis, and reduction of surgical stress are essential. We here report the perioperative management of a child with GLUT1DS.

In this study, we performed a genome-wide N-ethyl-N-nitrosourea (ENU) mutagenesis screen in mice to identify novel genes or alleles that regulate erythropoiesis. Here, we describe a recessive mouse strain, called RBC19, harbouring a point mutation within the housekeeping gene, Tpi1 , which encodes the glycolysis enzyme, triosephosphate isomerase (TPI). A serine in place of a phenylalanine at amino acid 57 severely diminishes enzyme activity in red blood cells and other tissues, resulting in a macrocytic haemolytic phenotype in homozygous mice, which closely resembles human TPI deficiency. A rescue study was performed using bone marrow transplantation of wild-type donor cells, which restored all haematological parameters and increased red blood cell enzyme function to wild-type levels after 7 weeks. This is the first study performed in a mammalian model of TPI deficiency, demonstrating that the haematological phenotype can be rescued., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

Serine biosynthesis defects are autosomal recessive metabolic disorders resulting from the deficiency of any of the three enzymes involved in de novo serine biosynthesis, specifically phosphoglycerate dehydrogenase (PGDH), phosphoserine aminotransferase (PSAT), and phosphoserine phosphatase (PSP). In this study, we performed metabolomic profiling on 4 children with serine biosynthesis defects; 3 with PGDH deficiency and 1 with PSAT deficiency. The evaluations were performed at baseline and with serine and glycine supplementation. Metabolomic profiling performed at baseline showed low phospholipid species, including glycerophosphocholine, glycerophosphoethanolamine, and sphingomyelin. All children had low serine and glycine as expected. Low glycerophosphocholine compounds were found in 4 children, low glycerophosphoethanolamine compounds in 3 children, and low sphingomyelin species in 2 children. Metabolic profiling with serine and glycine supplementation showed normalization of most of the low phospholipid compounds in the 4 children. Phospholipids are the major component of plasma and intracellular membranes, and phosphatidylcholine is the most abundant phospholipid of all mammalian cell types and subcellular organelles. Phosphatidylcholine is of particular importance for the nervous system, where it is essential for neuronal differentiation. The observed low phosphatidylcholine species in children with serine biosynthesis defects that improved after serine supplementation, supports the role of serine as a significant precursor for phosphatidylcholine. The vital role that phosphatidylcholine has during neuronal differentiation and the pronounced neurological manifestations in serine biosynthesis defects suggest that phosphatidylcholine deficiency occurring secondary to serine deficiency may have a significant contribution to the development of the neurological manifestations in individuals with serine biosynthesis defects., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Glucose transporter type 1 (GLUT1) deficiency syndrome (GLUT1-DS) leads to a wide range of neurological symptoms. Ketogenic diets are very efficient to control epilepsy and movement disorders. We tested a novel simple and rapid blood test in 30 patients with GLUT1-DS with predominant movement disorders, 18 patients with movement disorders attributed to other genetic defects, and 346 healthy controls. We detected significantly reduced GLUT1 expression only on red blood cells from patients with GLUT1-DS (23 patients; 78%), including patients with inconclusive genetic analysis. This test opens perspectives for the screening of GLUT1-DS in children and adults with cognitive impairment, movement disorder, or epilepsy. Ann Neurol 2017;82:133-138., (© 2017 The Authors. Annals of Neurology published by Wiley Periodicals, Inc. on behalf of American Neurological Association.)

Objectives: Carbohydrate intolerance or malabsorption has been suggested as a cause of chronic abdominal pain (CAP) in a subset of patients. We aimed to evaluate disaccharidase deficiencies in children with functional CAP and to correlate deficiencies with clinical features., Method: Patients presenting to the gastroenterology clinic at Children's Hospital of Wisconsin with abdominal pain prospectively completed a detailed demographic, history, and symptom questionnaire. The CAP cohort included those with at least 1 month of symptoms. Data on disaccharidase activity and histology of endoscopic biopsies were collected retrospectively. Only patients with normal histology were included in the study. The association between groups with low disaccharidases and clinical features was examined., Results: A total of 203 pediatric patients with CAP were included. The mean (SD) age was 11.5 (3.1) years, and 32.5% were male. The percentages of abnormally low disaccharidase levels using the standard laboratory cutoffs were lactase, 37%; sucrase, 21%; glucoamylase, 25%; and palatinase, 8%. Thirty-nine percent of the patients with low lactase also had low sucrase, and 67% of the patients with low sucrase had low lactase. There was no significant difference in the activities of any of the disaccharidases or sucrase/lactase ratio in relation to age. Also, no association was found between stool consistency, stool frequency, or location of pain and low disaccharidase activity., Conclusions: A large proportion of patients with CAP have deficiencies in disaccharidases. Bowel frequency, vomiting, or location of pain was no different between groups, suggesting that these clinical features cannot be used to predict disaccharidase deficiencies.

The analysis was applied to indices of IgE-mediated immunological reaction (total IgE) in patients with disorders of carbohydrate metabolism and diabetes and different blood groups (AB0) (n=93). The coefficient of pair correlation established a direct relationship between blood group 0 (I) and risk of development of diabetes type II (r=0.8) and higher risk of development of diabetes type I in patients with blood group A (II) (r=1). The average values of indices of total IgE in patients with blood groups 0 (I) and A (II) were compared and significantly differed the level of total IgE of blood group B (III). In case of expressed disorder of carbohydrate metabolism patients with blood groups 0 (I) and A (II) had indices of total IgE 43,61±15,12 и 86,2±42,61 kIU/l correspondingly that in average is four times lower than indices of patients with blood group B (III) who in case of diabetes type II had total IgE increased twice relatively to upper limit of standard amounting to 209,65±52,5 кIU/l., Competing Interests: The authors declare no conflict of interest.

Background/aims: Glucose-galactose malabsorption (GGM) is a rare and potentially fatal disorder. The autosomal recessive mutation of the SGLT1 gene interferes with the active glucose transport in the gut resulting in osmotic diarrhea and failure to thrive (FTT). Two nonrelated infants with GGM are presented as well as a novel mutation in SGLT1., Case Presentation: The first case consulted for FTT and presented with hypercalcemia and hypercalciuria. His mother had self-medicated with high doses of vitamin D. The second case consulted for macroscopic hematuria, and presented with dehydration and secondary acute kidney injury. In both cases, the profuse diarrhea, initially mistaken for polyuria, promptly resolved after the introduction of glucose-galactose-free milk. Investigations showed bilateral nephrocalcinosis and high levels of 1,25(OH)2D3 in both patients. We hypothesize that the upregulation of epithelial calcium channels (TRPV6) and 1,25(OH)2D3 are possible factors involved in the pathophysiology of nephrocalcinosis sometimes seen in GGM. Furthermore, a novel intronic SGLT1 mutation (c.207+2dup) is described., Conclusion: These 2 cases demonstrate that a malabsorption disorder such as GGM can present with nephrocalcinosis and/or hypercalcemia, with increased 1,25(OH)2D3 levels in infants. Prompt recognition of GGM is sometimes difficult but crucial.
., (© 2017 S. Karger AG, Basel.)

A 52-year-old man with a longstanding history of hypertriglyceridaemia (approximately 7 mmol/L (600 mg/dL)), unresponsive to treatment, presented to a lipid-specialty clinic. Additional triglyceride-lowering therapies were added with no effect. It was then noted that despite the apparent hypertriglyceridaemia, his serum sample was clear. A 'glycerol blank' was then requested from an advanced lipid laboratory, which reported a triglyceride value of 0.7 mmol/L (62 mg/dL). These findings suggest isolated asymptomatic glycerol kinase deficiency (GKD) or 'pseudohypertriglyceridaemia'. The falsely elevated triglyceride values in such individuals are a result of excess serum glycerol and clinical laboratories measuring glycerol to report triglyceride concentrations. After discontinuation or modification of the patient's primary triglyceride-lowering agents, the lipid panels and triglyceride values remained comparable to previous readings. Recognition of asymptomatic GKD is important to prevent unnecessary treatment and overestimated cardiovascular risk., (2015 BMJ Publishing Group Ltd.)

Objective: The aim of this study was to evaluate the effects of a 12-wk ketogenic diet (KD) on inflammatory status, adipose tissue activity biomarkers, and abdominal visceral (VAT) and subcutaneous fat (SAT) in children affected by glucose transporter 1 deficiency syndrome GLUT1 DS., Methods: We carried out a short-term longitudinal study on 10 children (mean age: 8.4 y, range 3.3-12 y, 5 girls, 5 boys) to determine fasting serum proinflammatory cytokines (high sensitivity C-reactive protein, tumor necrosis factor-α interleukin-6), adipocyte-derived chemokines (leptin and adiponectin), lipid profile, homeostatic model assessment-insulin resistance (HOMA-IR), quantitative insulin sensitivity index (QUICKI), anthropometric measurements, and VAT and SAT (by ultrasonography)., Results: Children showed no significant changes in inflammatory and adipose tissue activity biomarkers, blood glucose, lipid profile, anthropometric measurements, VAT, and SAT. Fasting insulin decreased (6 ± 3.2 μU/mL versus 3 ± 2 μU/mL; P = 0.001), and both HOMA-IR and QUICKI indexes were significantly modified (1.2 ± 0.6 versus 0.6 ± 0.4; P = 0.002; 0.38 ± 0.03 versus 0.44 ± 0.05; P = 0.002, respectively)., Conclusions: Only HOMA-IR and QUICKI indexes changed after 12 wk on a KD, suggesting that over a short period of time KD does not affect inflammatory cytokines production and abdominal fat distribution despite being a high-fat diet. Long-term studies are needed to provide answers concerning adaptive metabolic changes during KD., (Copyright © 2015 Elsevier Inc. All rights reserved.)

OBJECTIVE Previous studies have demonstrated aberrant glucagon physiology in the setting of type 1 diabetes (T1D) but have not addressed the potential impact of ambient glycemia on this glucagon response. Thus, our objective was to evaluate the impact of euglycemia versus hyperglycemia on the glucagon response to an oral glucose challenge in T1D. RESEARCH DESIGN AND METHODS Ten adults with T1D (mean age 56.6 ± 9.0 years, duration of diabetes 26.4 ± 7.5 years, HbA1c 7.5% ± 0.77, and BMI 24.1 kg/m(2) [22.6-25.4]) underwent 3-h 50-g oral glucose tolerance tests (OGTTs) on two separate days at least 24 h apart in random order under conditions of pretest euglycemia (plasma glucose [PG] between 4 and 6 mmol/L) and hyperglycemia (PG between 9 and 11 mmol/L), respectively. RESULTS Glycemic excursion on the OGTT was similar between the euglycemic and hyperglycemic tests (P = 0.72 for interaction between time postchallenge and glycemic setting). Interestingly, glucagon levels increased in response to the OGTT under both glycemic conditions (P < 0.001) and there were no differences in glucagon response between the euglycemic and hyperglycemic days (P = 0.40 for interaction between time postchallenge and glycemic setting). In addition, the incretin responses to the OGTT (glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1, glucagon-like peptide-2) were also not different between the euglycemic and hyperglycemic settings. CONCLUSIONS In patients with T1D, there is a paradoxical increase in glucagon in response to oral glucose that is not reversed when euglycemia is achieved prior to the test. This abnormal glucagon response likely contributes to the postprandial hyperglycemia in T1D irrespective of ambient glycemia.

Importance: GLUT1 deficiency syndrome is a treatable neurometabolic disorder, characterized by a low concentration of glucose in cerebrospinal fluid (CSF) and a decreased CSF to blood glucose ratio. Reports of patients with apparently normal CSF glucose levels, however, have raised the question whether CSF analysis is a reliable screening tool for GLUT1 deficiency syndrome., Objective: To determine the value of CSF analysis in the workup of GLUT1 deficiency syndrome., Evidence Review: PubMed was searched until July 2012 by using the terms glucose transporter 1 (GLUT-1) deficiency syndrome, glucose transporter defect, and SLC2A1-gene. Relevant references mentioned in the articles were also included. The CSF results of all patients with genetically proven GLUT1 deficiency syndrome described in literature were reevaluated., Findings: The levels of glucose in CSF, the CSF to blood glucose ratios, and the levels of lactate in CSF were reported for 147 (94%), 152 (97%), and 73 (46%) of 157 patients, respectively. The CSF glucose levels ranged from 16.2 to 50.5 mg/dL and were at or below the 10th percentile for all 147 patients. The CSF to blood glucose ratios ranged from 0.19 to 0.59 and were at or below the 10th percentile for 139 of 152 patients (91%), but they could be within the normal range as well. The CSF lactate levels ranged from 5.4 to 13.5 mg/dL and were at or below the 10th percentile for 59 of 73 patients (81%). A typical CSF profile for GLUT1 deficiency syndrome, which is defined as a CSF glucose level at or below the 10th percentile, a CSF to blood glucose ratio at or below the 25th percentile, and a CSF lactate level at or below the 10th percentile, was found in only 35 of 4099 CSF samples (0.9%) present in our CSF database of patients who received a diagnosis other than GLUT1 deficiency syndrome., Conclusions and Relevance: We conclude that if age-specific reference values are applied, CSF glucose and lactate levels are adequate biomarkers in the diagnostic workup of GLUT1 deficiency syndrome. Future availability of whole-exome sequencing in clinical practice will make the existence of a reliable biomarker for GLUT1 deficiency syndrome even more important, in order to interpret genetic results and, even more importantly, not to miss SLC2A1-negative patients with GLUT1 deficiency syndrome.

Glucose transporter type 1 deficiency syndrome (Glut-1DS) is caused by autosomal dominant haplodeficiency or autosomal recessive with homozygous mutation of the glucose transporter 1 (SLC2A1) gene and is characterized by severe seizures, developmental delay, ataxia and acquired microcephaly. We describe the first known Korean patient with glucose transporter 1 deficiency syndrome, who had a novel mutation in the splice site. The patient began having intractable seizures at 4 days of age that initially presented as eye blinking and apnea, evolving into generalized tonic seizures. A lumbar puncture revealed low glucose concentration in the cerebrospinal fluid (CSF) in the setting of normoglycemia (blood glucose, 106 mg/dl; CSF glucose 21 mg/dl, and CSF to blood glucose ratio 0.20). The results of a 3-O-methylglucose uptake study in erythrocytes (RBC) revealed that glucose uptake reduced to 48% of his parents in the patient. The patient responded to a ketogenic diet that was initiated at 4 months of age and currently is on the modified Atkins diet (MAD) without seizures. He does not require antiepileptic medication. We diagnosed the first Glut-1 patient in Korea with a novel splice site mutation on the basis of clinical features, deficient glucose uptake and a mutation in the SLC2A1 gene., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The National Cholesterol Educational Program Adult Treatment Panel's third report define borderline-high, high, and very high triglycerides as serum levels of 150-199 mg/dL, 200-499 mg/dL, and ≥500 mg/dL, respectively. Hypertriglyceridemia (HTG) is generally very responsive to both therapeutic lifestyle changes (TLC), and drug therapy, with niacin, omega-3 fatty acids, fibrates, and statins, each reducing levels by ~10-50%. This paper presents two cases of patients who were aggressively treated for significant HTG with little response to therapy. Although most measured triglyceride (TG) values in these patients were markedly elevated, periodic concentrations were reported as normal. When this occurs, the clinician must immediately think of the diagnosis 'pseudohypertriglyceridemia' or as it is more aptly termed 'glycerolemia' secondary to glycerol kinase deficiency (GKD)., (Copyright © 2012 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Apolipoprotein C-III (apoCIII) is a small glycoprotein with a single mucin-type core-1 oligosaccharide and is analyzed by isoelectric focusing (IEF) for the diagnosis of genetic defects in O-glycan biosynthesis such as congenital disorders of glycosylation. In the present study, mass spectrometry of apoCIII, after a simple procedure for sample preparation using a small amount of serum, was demonstrated to be a reliable alternative to IEF. It allows reproducible glycan profiling and detection of unglycosylated species. This method was applied to an autosomal recessive cutis laxa type-2 patient and demonstrated decreased site occupancy by O-glycosylation.

Camelids develop a number of disturbances related to energy metabolism. Some are similar to disorders seen in other species, but most relate to camelids' unusual characteristics of poor glucose tolerance, partial insulin resistance, and low concentrations of circulating insulin. Camelids are especially prone to abnormalities related to stimuli that inhibit insulin release or activity, or that promote activities normally antagonized by insulin. These include stimuli that mobilize glycogen or fat stores, or inhibit glucose uptake or intravascular glycolysis. These stimuli are generally more important than negative energy balance in triggering these disorders. Treatment must concentrate on the hormonal aspects, and not just provision of energy. Treatments related to hormonal aspects include those to decrease catecholamine release and to provide exogenous insulin until the camelid is again able to maintain appropriate energy substrate homeostasis.

Glucose transporter type 1 (Glut1) deficiency syndrome (Glut1 DS, OMIM: #606777) is characterized by infantile seizures, acquired microcephaly, developmental delay, hypoglycorrhachia (CSF glucose <40 mg/dL), and decreased erythrocyte glucose uptake (56.1 +/- 17% of control). Previously, we reported two patients with a mild Glut1 deficiency phenotype associated with a heterozygous GLUT1 T295M mutation and normal erythrocyte glucose uptake. We assessed the pathogenicity of T295M in the Xenopus laevis oocyte expression system. Under zero-trans influx conditions, the T295M Vmax (590 pmol/min/oocyte) was 79% of the WT value and the Km (14.3 mM) was increased compared with WT (9.6 mM). Under zero-trans efflux conditions, both the Vmax (1216 pmol/min/oocyte) and Km (8.8 mM) in T295M mutant Glut1 were markedly decreased in comparison to the WT values (7443 pmol/min/oocyte and 90.8 mM). Western blot analysis and confocal studies confirmed incorporation of the T295M mutant protein into the plasma membrane. The side chain of M295 is predicted to block the extracellular "gate" for glucose efflux in our Glut-1 molecular model. We conclude that the T295M mutation specifically alters Glut1 conformation and asymmetrically affects glucose flux across the cell by perturbing efflux more than influx. These findings explain the seemingly paradoxical findings of Glut1 DS with hypoglycorrhachia and "normal" erythrocyte glucose uptake.

We describe an infant girl with psychomotor retardation, growth retardation, mild facial dysmorphy, evidence of liver involvement and a type 2 pattern of serum sialotransferrins. Serum transferrin glycan analysis with MALDI-TOF showed an extremely altered N-glycan pattern with a large number of truncated asialoglycans pointing to a severely defective N-glycan processing. The basic defect in this patient with CDG-IIx has not yet been identified.

This report describes a female infant with cutis laxa, short stature, microcephaly, wide anterior fontanel and bifrontal cortical malformation. Isoelectrofocusing of plasma transferrin and apolipoprotein C-III showed abnormal patterns suggesting defective N- and O-glycosylation. Together with recently reported patients, this patient represents a novel type of congenital disorder of glycosylation.

Objectives: Glycosylation analysis provides many opportunities for diagnostics, but its complexity hampers its routine application. Aiming to alleviate this problem, we developed a simple assay that can measure sialylation of transferrin directly from serum., Design and Methods: Transferrin samples with different levels of sialylation were prepared by desialylation. Enzyme-linked-lectin assay (ELLA) and high-performance anion-exchange chromatography (HPAEC) have been used to analyze transferrin sialylation. Periodate oxidation was used to oxidize carbohydrates on antibodies., Results: ELLA was developed for the analysis of serum transferrin sialylation. Antibodies oxidized in situ with periodate have been used to capture transferrin from serum samples. Sialic acid on transferrin has been detected with Sambucus nigra agglutinin (SNA) lectin. Transferrin samples with different sialylation levels prepared by differential desialylation have been used as standards. Accuracy of the method has been confirmed by comparison to HPAEC analysis., Conclusions: A rapid and simple ELLA that can be routinely used for the analysis of serum transferrin sialylation has been developed.

Glycosylation of proteins is a very complex process which involves numerous factors such as enzymes or transporters. A defect in one of these factors in glycan biosynthetic pathways leads to dramatic disorders named congenital disorders of glycosylation (CDG). CDG can affect the biosynthesis of not only protein N-glycans but also O-glycans. The structural analysis of glycans on serum glycoproteins is essential to solving the defect. For this reason, we propose in this paper a strategy for the simultaneous characterization of both N- and O-glycan chains isolated from the serum glycoproteins. The serum (20 microL) is used for the characterization of N-glycans which are released by enzymatic digestion with PNGase F. O-glycans are chemically released by reductive elimination from whole serum glycoproteins using 10 microL of the serum. Using strategies based on mass spectrometric analysis, the structures of N- and O-glycan chains are defined. These strategies were applied on the sera from one patient with CDG type IIa, and one patient with a mild form of congenital disorder of glycosylation type II (CDG-II) that is caused by a deficiency in the Cog1 subunit of the complex.

The glucose transporter type 1 deficiency syndrome (GLUT-1 SD) (OMIM 606777) is an inborn error of metabolism of brain glucose transport. The characteristic clinical manifestations are seizures, hypotonia, developmental delay, microcephaly and hypoglycorrhachia. We report a girl with normal weight and height at birth. At 6 weeks of age she started with convulsions reaching up to 20 myoclonic seizures a day. She was treated with valproate, phenobarbital and carbamazepine without response. Blood analysis including aminoacids and acylcarnitines were all normal. The brain MRI showed frontal atrophy with an increased subarachnoidal space and Electroencephalography was abnormal. Blood glucose was 84 mg/dl and spinal fluid glucose 26 mg/dl with a ratio of 0.31 (Normal Ratio >0.65+/-00.1). These results suggested the diagnosis of GLUT-1 SD, and was confirmed with erythrocyte glucose uptake of 44% (Normal range 80-100%). A molecular study found the mutation 969del, C971T in exon 6 of the gene Glut-1. Treatment with a ketogenic diet was started immediately and after 7 days with this diet seizures ceased. Anticonvulsants were progressively suspended. At present, the patient is 6 years old, she continues on a ketogenic diet and supplements with L-carnitine, lipoic acid, vitamins and minerals. Growth and development are normal with an intelligence quotient of 103. It is concluded that it is necessary to include GLUT-1 SD in the differential diagnosis of children with early seizures that are non responsive to pharmacological treatment.

We report three Japanese patients with glucose transporter type 1 deficiency syndrome (Glut1DS). Two patients had a normal erythrocyte 3-O-methylglucose (3OMG) uptake, one with a previously reported T295M substitution and the other with a novel 12-bp insertion at nt 1034-1035, ins CAGCAGCTGTCT. The third patient, with deficient 3OMG uptake, had a previously reported hot-spot mutation, R333W. All three patients responded to a ketogenic diet. All patients showed a significant improvement in ataxia, with blood beta-hydroxybutyrate (BOHB) levels ranging from 0.1 to 3mM. BOHB levels of at least 3mM were necessary to control seizures, and higher ketone levels are recommended to meet brain energy needs during development. FDG-PET scan, performed before and after a ketogenic diet in the R333W patient, did not change despite a clinical improvement. This clinical condition is treatable and early diagnosis is important.

Single proteins, when analyzed with 2-D-PAGE, often show multiple spots due to PTMs. In gels of human body fluids, the spot patterns facilitate the assignment and identification of the proteins. We analyzed serums from patients with congenital disorders of glycosylation (CDG) in which glycoproteins are strongly impacted and exhibit highly distinguishable spot patterns compared to healthy controls. We detected a typical protein pattern for alpha1-acid glycoprotein (AGP) and transferrin (Trf) that are markers for CDG. AGP contains five glycosylation sites which results in a complex microheterogeneity of the glycoprotein. On the other hand, in Trf, a glycoprotein with only two glycosylation sites, mainly biantennary complex-type-N-linked glycans are bound. We used 2-D-PAGE, MALDI-TOF-MS, and ESI-MS for the analysis of these glycoproteins and their corresponding glycans. In AGP, the heterogenic glycosylation of the different glycosylation sites is responsible for the complex spot pattern. In contrast to AGP, the protein spots of Trf cannot be explained by glycosylation. We found strong evidence that oxidation of cysteine is responsible for the spot pattern. This study contradicts the commonly accepted assumption that the multiple protein spots of Trf observed in 2-D-PAGE are due, as in AGP, to the glycosylation of the protein.

Intracranial hemorrhage in a term neonate is a rare event in the absence of an identifiable precipitating factor such as severe thrombocytopenia, mechanical trauma, asphyxia, infections, or congenital vascular malformations. Congenital disorders of glycosylation are a genetically and clinically heterogeneous group of multisystem disorders characterized by the abnormal glycosylation of a number of glycoproteins. Although bleeding caused by abnormal glycosylation of various coagulation factors is a well-known clinical complication of several types of congenital disorders of glycosylation, intracranial hemorrhage has not been reported as an initial manifestation of this entity. Here we report the detailed history of a family with 2 consecutive male infants, both born at term with intracranial hemorrhage diagnosed within the first 24 hours of life. The diagnosis of a congenital disorder of glycosylation was established in the second infant by an abnormal glycosylation of serum transferrin detected by electrospray-ionization mass spectrometry. Both infants showed significant neurologic deterioration during the first month of life, and both died at 5 months of age. Intracranial hemorrhage in a term neonate without a potential precipitating factor represents yet another clinical feature that should raise the suspicion for a congenital disorder of glycosylation.

A method for the diagnosis of the congenital disorders of glycosylation type I (CDG-I) by SELDI-TOF-MS of serum transferrin immunocaptured on protein chip arrays is described. The underglycosylation of glycoproteins in CDG-I produces glycoforms of transferrin with masses lower than that of the normal fully glycosylated transferrin. Immobilisation of antitransferrin antibodies on reactive-surface protein chip arrays (RS100) selectively enriched transferrin by at least 100-fold and allowed the detection of patterns of transferrin glycoforms by SELDI-TOF-MS using approximately 0.3 microL of serum/plasma. Abnormal patterns of immunocaptured transferrin were detected in patients with known defects in glycosylation (CDG-Ia, CDG-Ib, CDG-Ic, CDG-If and CDG-Ih) and in patients in whom the basic defect has not yet been identified (CDG-Ix). The correction of the N-glycosylation defect in a patient with CDG-Ib after mannose therapy was readily detected. A patient who had an abnormal transferrin profile by IEF but a normal profile by SELDI-TOF-MS analysis was shown to have an amino acid polymorphism by sequencing transferrin by quadrupole-TOF MS. Complete agreement was obtained between analysis of immunocaptured transferrin by SELDI-TOF-MS and the IEF profile of transferrin, the clinical severity of the disease and the levels of aspartylglucosaminidase activity (a surrogate marker for the diagnosis of CDG-I). SELDI-TOF-MS of transferrin immunocaptured on protein chip arrays is a highly sensitive diagnostic method for CDG-I, which could be fully automated using microtitre plates and robotics.

Elevated plasma aspartylglucosaminidase activity was found in 21/25 cases of CDG Ia, in single cases of CDG Ib, Ic and If, and in 15/16 cases of CDG Ix. The CDG I patients in whom the activity was not raised were either atypical clinically (CDG Ia) or very young (CDG Ih).

We report a new patient with CDG Ig and review the five other known patients. From the data on this small number of patients, it seems that the association of psychomotor retardation, male hypogenitalism and decreased serum IgG in a patient with a type 1 pattern of serum sialotransferrins might be a clue to the diagnosis of CDG Ig.

Congenital disorders of glycosylation (CDG) represent a group of inherited multiorgan diseases caused by defects in the biosynthesis of glycoproteins. We report on two dysmorphic siblings with severe liver disease who died at the age of a few weeks. Increased activities of lysosomal enzymes in plasma were found, though total sialic acid in plasma was strongly decreased. Isoelectric focusing of serum sialotransferrins showed a type 2-like CDG pattern. Some of the known CDG subtypes were excluded. O-Glycosylation was investigated by isoelectric focusing of apolipoprotein C-III, which showed increased fractions of hyposialylated isoforms. In a consecutive study a defect in the conserved oligomeric Golgi complex was established at the level of subunit COG-7, leading to disruption of multiple glycosylation functions of the Golgi. This report on patients with a new variant of CDG, due to a multiple Golgi defect, emphasizes in addition to sialotransferrins the importance of analysis of a serum O-linked glycoprotein, e.g. apolipoprotein C-III, in unclassified CDG-X cases.

The fundamental importance of correct protein glycosylation is abundantly clear in a group of diseases known as congenital disorders of glycosylation (CDGs). In these diseases, many biological functions are compromised, giving rise to a wide range of severe clinical conditions. By performing detailed analyses of the total serum glycoproteins as well as isolated transferrin and IgG, we have directly correlated aberrant glycosylation with a faulty glycosylation processing step. In one patient the complete absence of complex type sugars was consistent with ablation of GlcNAcTase II activity. In another CDG type II patient, the identification of specific hybrid sugars suggested that the defective processing step was cell type-specific and involved the mannosidase III pathway. In each case, complementary serum proteome analyses revealed significant changes in some 31 glycoproteins, including components of the complement system. This biochemical approach to charting diseases that involve alterations in glycan processing provides a rapid indicator of the nature, severity, and cell type specificity of the suboptimal glycan processing steps; allows links to genetic mutations; indicates the expression levels of proteins; and gives insight into the pathways affected in the disease process.

The N-glycans present on the total mixture of serum glycoproteins (serum N-glycome) were analyzed in 24 subjects with congenital disorder of glycosylation type I (CDG-I) and 7 healthy, age-matched individuals. No new N-glycan structures were observed in the sera of CDG-I patients as compared with normal sera. However, we observed in all subtypes a significantly increased degree of core alpha-1,6-fucosylation of the biantennary glycans as compared to normal, as well as a significant decrease in the amount of triantennary glycans. These serum N-glycome changes appear to be a milder manifestation of some of the changes observed in adult liver cirrhosis patients, which is compatible with the reported steatosis and fibrosis in CDG-I patients. In the CDG-Ia subgroup, the extent of the serum N-glycome changes correlates with the aberration of the serum transferrin isoelectric focusing pattern, which measures the severity of the lack of entire N-glycan chains (primary consequence of CDG-I) in the liver and is the standard diagnostic test for this category of inherited diseases.

Conditions under which the glycosylation capacity of cells is limited provide an opportunity for studying the efficiency of site-specific glycosylation and the role of glycosylation in the maturation of glycoproteins. Congenital disorders of glycosylation type 1 (CDG-I) provide such a system. CDG-I is characterized by underglycosylation of glycoproteins due to defects in the assembly or transfer of the common dolichol-pyrophosphate-linked oligosaccharide precursor of asparagine-linked glycans. Human plasma alpha1-antitrypsin is normally fully glycosylated at three asparagine residues (46, 83, and 247), but un-, mono-, di-, and fully glycosylated forms of alpha1-antitrypsin were detected by 2D PAGE in the plasma from patients with CDG-I. The state of glycosylation of the three asparagine residues was analyzed in all the underglycosylated forms of alpha1-antitrypsin by peptide mass fingerprinting using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. It was found that asparagine 46 was always glycosylated and that asparagine 83 was never glycosylated in the underglycosylated glycoforms of alpha1-antitrypsin. This showed that the asparagine residues are preferentially glycosylated in the order 46>247>83 in the mature underglycosylated forms of alpha1-antitrypsin found in plasma. It is concluded that the nonoccupancy of glycosylation sites is not random under conditions of decreased glycosylation capacity and that the efficiency of glycosylation site occupancy depends on structural features at each site. The implications of this observation for the intracellular transport and sorting of glycoproteins are discussed.

Unlabelled: Facilitated glucose transporter protein type 1 (GLUT1) deficiency syndrome (MIM 138140) defines a prototype of a novel group of disorders resulting from impaired glucose transport across blood-tissue barriers. It is caused by a defect in glucose transport into brain, mediated by the facilitative glucose transporter GLUT1. Since 1991, more than 70 patients have been identified. The hallmark of the disease is a low glucose concentration in the CSF (hypoglycorrhachia) in the presence of normoglycaemia (CSF/blood glucose ratio <0.4). Clinical features are variable and include seizures, developmental delay, acquired microcephaly, hypotonia, and a complex motor disorder with elements of ataxia, dystonia, and spasticity. The GLUT1 defect can be confirmed in erythrocytes by glucose uptake studies and GLUT1 immunoreactivity, and by molecular analysis of the GLUT1 gene. Several heterozygous mutations resulting in GLUT1 haploinsufficiency have been identified. An effective treatment is available by means of a ketogenic diet as ketone bodies serve as an alternative fuel for the developing brain., Conclusion: this treatable condition should be suspected in children with unexplained neurological disorders associated with epilepsy and developmental delay and confirmed by a lumbar puncture.

Increased fucosylation of the type (sialyl) Lewis(x) was detected on the acute-phase plasma protein alpha(1)-acid glycoprotein (AGP) in patients with the congenital disorder of glycosylation type IA. This is remarkable, because in these patients the biosynthesis of guanosine 5'-diphosphate (GDP)-D-mannose is strongly decreased, and GDP-D-mannose is the direct precursor for GDP-L-fucose, the substrate for fucosyltransferases. The concomitantly occurring increased branching of the glycans of AGP and the increased fucosyltransferase activity in plasma suggest that a chronic hepatic inflammatory reaction has induced the increase in fucosylation.

Haptoglobin is one of acute phase glycoproteins often used as markers in glycopathology studies. In this work the oligosaccharide structures of haptoglobin from 'healthy' subjects have been studied in detail, taking into consideration the possible dependence of glycosylation on the phenotype. About 75% of charged haptoglobin glycans were of biantennary complex structure, and some of them lacked one terminal sialic acid molecule. Triantennary structures made up almost 25% of the charged glycans pool, and highly branched tetrasialylated oligosaccharides did not exceed 1%. The main difference between haptoglobin derived from the sample of pooled 44 sera and from the 2-2 phenotype individual concerned the relative content of trisialylated oligosaccharide with one 2-3 linked sialic acid residue. The oligosaccharide profile of haptoglobin derived from serum of a patient suffering from congenital disorder of glycosylation was compared to 'healthy' controls. It was shown, that four main glycans are identical in patient and 'normal' haptoglobins. Some alterations were found in the relative content of mono-, bi-, and trisialylated glycans as well as in the appearance of some tracely abundant oligosaccharides in haptoglobin of the patient with congenital disorder of glycosylation.