Elevated serum biotinidase activity in hepatic glycogen storage disorders--a convenient biomarker.

An elevated serum biotinidase activity in patients with glycogen storage disease (GSD) type Ia has been reported previously. The aim of this work was to investigate the specificity of the phenomenon and thus we expanded the study to other types of hepatic GSDs. Serum biotinidase activity was measured in a total of 68 GSD patients and was compared with that of healthy controls (8.7 +/- 1.0; range 7.0-10.6 mU/ml; n = 26). We found an increased biotinidase activity in patients with GSD Ia (17.7 +/- 3.9; range: 11.4-24.8; n = 21), GSD I non-a (20.9 +/- 5.6; range 14.6-26.0; n = 4), GSD III (12.5 +/- 3.6; range 7.8-19.1; n = 13), GSD VI (15.4 +/- 2.0; range 14.1-17.7; n = 3) and GSD IX (14.0 +/- 3.8; range: 7.5-21.6; n = 22). The sensitivity of this test was 100% for patients with GSD Ia, GSD I non-a and GSD VI, 62% for GSD III, and 77% for GSD IX, indicating reduced sensitivity for GSD III and GSD IX, respectively. In addition, we found elevated biotinidase activity in all sera from 5 patients with Fanconi-Bickel Syndrome (15.3 +/- 3.7; range 11.0-19.4). Taken together, we propose serum biotinidase as a diagnostic biomarker for hepatic glycogen storage disorders.

Case report: liver glycogen synthase deficiency--a cause of ketotic hypoglycemia.

Glycogen synthase deficiency is a rare inborn error of metabolism, characterized by fasting hypoglycemia, hypoglycemic seizures, and ketonuria. Only 7 families with 14 affected children have been reported. Here, we report an additional patient with this deficiency. Findings in this patient were clinically and biochemically consistent with those reported in patients with ketotic hypoglycemia and may alert the clinician to consider glycogen synthase deficiency.

A founder mutation in the GK1 gene is responsible for galactokinase deficiency in Roma (Gypsies).

Galactokinase deficiency is an inborn error in the first step of galactose metabolism. Its major clinical manifestation is the development of cataracts in the first weeks of life. It has also been suggested that carriers of the deficiency are predisposed to presenile cataracts developing at age 20-50 years. Newborn screening data suggest that the gene frequency is very low worldwide but is higher among the Roma in Europe. Since the cloning of the galactokinase gene (GK1) in 1995, only two disease-causing mutations, both confined to single families, have been identified. Here we present the results of a study of six affected Romani families from Bulgaria, where index patients with galactokinase deficiency have been detected by the mass screening. Genetic linkage mapping placed the disease locus on 17q, and haplotype analysis revealed a small conserved region of homozygosity. Using radiation hybrid mapping, we have shown that GK1 is located in this region. The founder Romani mutation identified in this study is a single nucleotide substitution in GK1 resulting in the replacement of the conserved proline residue at amino acid position 28 with threonine (P28T). The P28T carrier rate in this endogamous population is approximately 5%, suggesting that the mutation may be an important cause of early childhood blindness in countries with a sizeable Roma minority.

Molecular diagnosis of type 1c glycogen storage disease.

Glycogen storage disease type 1 (GSD 1) results from deficiency of the microsomal multicomponent glucose-6-phosphatase system. Malfunction of the catalytic subunit characterises GSD 1a. GSD 1b and GSD 1c are characterised by defective microsomal glucose-6-phosphate or pyrophosphate/phosphate transport, respectively. Recently, a gene encoding a microsomal transporter protein has been found to be mutated in GSD 1b and 1c patients. Here, we report the genomic sequence of the transporter gene and the detection of a homozygous 2-bp deletion (1211delCT) and a homozygous donor splice site mutation (317+1G-->T) in two GSD 1c patients, confirming that GSD 1c is allelic to GSD 1b.

Missense mutations in SGLT1 cause glucose-galactose malabsorption by trafficking defects.

Glucose-galactose malabsorption (GGM) is an autosomal recessive disorder caused by defects in the Na+/glucose cotransporter (SGLT1). Neonates present with severe diarrhea while on any diet containing glucose and/or galactose [1]. This study focuses on a patient of Swiss and Dominican descent. All 15 exons of SGLT1 were screened using single stranded conformational polymorphism analyses, and aberrant PCR products were sequenced. Two missense mutations, Gly318Arg and Ala468Val, were identified. SGLT1 mutants were expressed in Xenopus laevis oocytes for radiotracer uptake, electrophysiological experiments, and Western blotting. Uptakes of [14C]alpha-methyl-d-glucoside by the mutants were 5% or less than that of wild-type. Two-electrode voltage-clamp experiments confirmed the transport defects, as no noticeable sugar-induced current could be elicited from either mutant [2]. Western blots of cell protein showed levels of each SGLT1 mutant protein comparable to that of wild-type, and that both were core-glycosylated. Presteady-state current measurements indicated an absence of SGLT1 in the plasma membrane. We suggest that the compound heterozygote missense mutations G318R and A468V lead to GGM in this patient by defective trafficking of mutant proteins from the endoplasmic reticulum to the plasma membrane.

Clinical, biochemical and molecular findings in a patient with X-linked liver glycogenosis followed for 40 years.

UNLABELLED: Phosphorylase kinase (PHK) is a regulatory enzyme in glycogen metabolism. Mutations in the gene encoding the alpha subunit of PHK (PHKA2) have been shown to be responsible for X-linked liver glycogenosis (XLG). XLG, a frequent type of glycogen storage disease, is characterised by hepatomegaly and growth retardation. Two subtypes of XLG have been described: XLG type I patients have a clear-cut PHK deficiency in liver and blood cells, whereas XLG type II patients have a normal or residual activity. Here, we present clinical, biochemical and molecular findings on a liver glycogenosis patient in whom the diagnosis XLG II only became clear after enzyme assays in the liver and identification of the disease-causing mutation. A missense mutation replacing arginine at amino acid position 186 by histidine (R186H) was identified in the PHKA2 gene. Mutations of the same arginine residue have been previously found in at least four other unrelated XLG II patients. CONCLUSION: Arginine at position 186 of the alpha subunit seems to play an important role in the structure or the regulation of PHK. In patients with XLG having normal or residual PHK activity where XLG II is suspected, the identification of mutations in PHKA2 leads to the final classification.

Mutations in the liver glycogen synthase gene in children with hypoglycemia due to glycogen storage disease type 0.

Glycogen storage disease type 0 (GSD-0) is a rare form of fasting hypoglycemia presenting in infancy or early childhood and accompanied by high blood ketones and low alanine and lactate concentrations. Although feeding relieves symptoms, it often results in postprandial hyperglycemia and hyperlactatemia. The glycogen synthase (GS) activity has been low or immeasurable in liver biopsies, whereas the liver glycogen content has been only moderately decreased. To investigate whether mutations in the liver GS gene (GYS2) on chromosome 12p12.2 were involved in GSD-0, we determined the exon-intron structure of the GYS2 gene and examined nine affected children from five families for linkage of GSD-0 to the GYS2 gene. Mutation screening of the 16 GYS2 exons was done by single-strand conformational polymorphism (SSCP) and direct sequencing. Liver GS deficiency was diagnosed from liver biopsies (GS activity and glycogen content). GS activity in the liver of the affected children was extremely low or nil, resulting in subnormal glycogen content. After suggestive linkage to the GYS2 gene had been established (LOD score = 2.9; P < 0.01), mutation screening revealed several different mutations in these families, including a premature stop codon in exon 5 (Arg246X), a 5'-donor splice site mutation in intron 6 (G+1T--> CT), and missense mutations Asn39Ser, Ala339Pro, His446Asp, Pro479Gln, Ser483Pro, and Met491Arg. Seven of the affected children carried mutations on both alleles. The mutations could not be found in 200 healthy persons. Expression of the mutated enzymes in COS7 cells indicated severely impaired GS activity. In conclusion, the results demonstrate that GSD-0 is caused by different mutations in the GYS2 gene.

Lysosomal enzyme activities in serum and leukocytes from patients with carbohydrate-deficient glycoprotein syndrome type IA (phosphomannomutase deficiency).

From 10 patients with carbohydrate-deficient glycoprotein (CDG) syndrome due to phosphomannomutase (PMM) deficiency, out of 10 lysosomal enzymes, 7 enzyme activities were measured in serum and 9 in leukocytes. In serum there was a 2-fold to 4-fold increase in activity of beta-glucuronidase, beta-hexosaminidase, beta-galactosidase, and arylsulphatase A. In leukocytes, however, several enzymes had reduced activity, particularly alpha-fucosidase, beta-glucuronidase and alpha-mannosidase. These abnormalities could result from missorting, defective reuptake and/or reduced stability of the enzymes due to the defective glycosylation.

Mucolipidosis type II in a domestic shorthair cat.

A seven-month-old, female domestic shorthair cat was presented to the Veterinary Teaching Hospital, University of Zurich, with abnormal facial features, retarded growth and progressive hindlimb paresis. On physical examination the cat had a flat, broad face with hypertelorism, frontal bossing, small ears and thickened upper and lower eyelids. The corneas of both eyes were clear and the pupils were dilated. The skin was generally thickened, most prominently on the dorsal aspect of the neck. Radiography of the entire skeleton revealed a severely deformed spinal column, bilateral hip luxation with hip dysplasia, an abnormally shaped skull and generalised decreased bone opacity. The clinical features and radiographic changes were suggestive of mucopolysaccharidosis. The toluidine blue spot test on a urine sample, however, was negative for glycosaminoglycans. Further biochemical investigations revealed a deficiency of the enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase, EC 2.7.8.17) in peripheral leukocytes and an elevation of many lysosomal enzymes in the serum of the cat which is diagnostic for mucolipidosis type II. Histology and electron microscopy of different tissues are briefly summarised. The findings of this cat, the first reported case of mucolipidosis type II are compared with other similar storage diseases described in the cat.

Liver glycogen synthase deficiency: a rarely diagnosed entity.

UNLABELLED: Three children from two German families are described and the observation compared with the previously published three families comprising eight patients. The two index cases presented with morning fatigue, had ketotic hypoglycaemia when fasting which rapidly disappeared after eating, and hepatic glycogen deficiency and absent or very low hepatic glycogen synthase activity. Metabolic profiles comprising glucose, lactate, alanine, and ketones in blood were typical for hepatic glycogen synthase deficiency. Symptoms were rapidly relieved and chemical signs corrected by introducing frequent protein-rich meals and night-time feedings of suspension of uncooked corn (maize) starch. The discovery of oligosymptomatic and asymptomatic siblings suggests that there are more persons with undiagnosed hepatic glycogen synthase deficiency. CONCLUSION: Liver glycogen synthase deficiency is likely to be more common than is believed today. It should be sought in children who, before the first meal of the day, present with drowsiness, lack of attention, pallor, uncoordinated eye movements, disorientation or convulsions and who have hypoglycaemia and acetone in urine.

[Adult form of GM2-gangliosidosis: a man and 2 sisters with hexosaminidase-A and -B deficiency (Sandhoff disease) and literature review]. / Adulte Form der GM2-Gangliosidose: drei Geschwister mit Hexosaminidase-A- und -B-Mangel (Morbus Sandhoff) und Literaturübersicht.

Three adult siblings had atypical progressive spinal muscular atrophy of the limb-girdle type, predominantly sensory polyneuropathy and cerebellar ataxia. Hexosaminidase A and B activity was profoundly decreased in serum, leukocytes and cultured fibroblasts. GM2-gangliosidosis, variant O (Sandhoff disease) was diagnosed. Mechano-allodynia was the presenting symptom in two of the patients. After 50 years of disease evolution, the patients led an independent life and were intellectually normal. The literature on the adult form of GM2-gangliosidosis is reviewed.

Spontaneous mucolipidosis in a cat: an animal model of human I-cell disease.

A 7-month-old female cat was seen for abnormal facial features and abnormality of gait. Facial dysmorphism, large paws in relation to body size, dysostosis multiplex, and poor growth were noted, and mucopolysaccharidosis was suspected. A negative urine test for sulfated glycosaminoglycans and extreme stiffness of skin indicated a mucolipidosis hitherto unknown in animals. Deficiency of UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase, EC 2.7.8.17) activity was demonstrated in leukocytes and cultured fibroblasts, which had the appearance of inclusion cells (I-cells). Activities of a set of lysosomal hydrolases were abnormally low in fibroblasts and excessive in blood plasma. Postmortem morphology revealed lysosomal inclusions predominantly in fibroblasts but also in endothelial cells and chondrocytes, i.e., in cells of mesenchymal origin. Storage lysosomes contained oligosaccharides, mucopolysaccharides, and lipids. Tissues most affected were bones, cartilage, skin, and other connective tissues such as those in heart valves, aortic wall, and vocal cords. Parenchymal cells of liver and kidney were unaffected, as was skeletal muscle. Only a few of the cerebral cortical neurons had lipid inclusions; in sciatic nerve some axons were affected, but other peripheral nerves were normal. There were striking clinical, biochemical, and morphologic similarities between the disorder in this cat and the human I-cell disease.

Early and severe sensory loss in three adult siblings with hexosaminidase A and B deficiency (Sandhoff disease).

Three siblings in their sixth and seventh decade with hexosaminidase A and B deficiency (adult form of GM2-gangliosidosis, variant O) developed early and severe sensory loss in addition to chronic motor neuron disease and cerebellar ataxia. Prominent mechanoallodynia was a manifesting symptom in two siblings. It is suggested that sensory deficits are due to a central-peripheral dying back axonopathy. The early and dominant sensory disturbances extend the clinical range of GM2-gangliosidosis.

Partial deficiency of galactose-1-phosphate uridyltransferase.

In screening programmes testing newborns for galactose-1-phosphate uridyltransferase and/or galactose, partial enzyme deficiency is frequently discovered. This is shown for one laboratory in Switzerland where 104 newborns were singled out from a total of 476,000. Of these, 72 had partial transferase deficiency below 9 mumol/h per g Hb and were assumed to be compound heterozygotes for "classical" galactosemia and the Duarte variant. Present day management of compound heterozygotes consisting of lactose-free diet for 4 months is described and discussed in the light of published opinion. The appropiateness of this pragmatic approach can at present not be judged according to objective criteria.

Feline mucopolysaccharidosis VII due to beta-glucuronidase deficiency.

A male cat 12-14 weeks old had walking difficulties and an enlarged abdomen. Facial dysmorphism, plump paws, corneal clouding, granulation of neutrophils, vacuolated lymphocytes, and a positive urine test for sulfated glycosaminoglycans suggested mucopolysaccharidosis. Cultured fibroblasts incorporated 35SO4 into mucopolysaccharides more actively than did fibroblasts of a feline control, and degradation was far inferior. Activity of beta-glucuronidase was absent in leukocytes and markedly reduced in fibroblasts, thus establishing the diagnosis of mucopolysaccharidosis VII, a disorder previously described in humans, dogs, and mice. Light microscopic examination revealed foam cells in virtually all organs examined, and electron microscopic examination showed pancytic storage of floccular material characteristic of mucopolysaccharides. Stored sphingolipids in the form of zebra bodies were seen in ganglion cells of the central nervous system and in smooth muscle cells of blood vessels. This case represents another animal model of mucopolysaccharidosis VII with the full disease characteristics known in human patients.

Defective neutrophil and monocyte functions in glycogen storage disease type Ib: a literature review.

A summary review of leukocyte function in 42 published cases of glycogen storage disease Ib is presented. Polymorphonuclear and monocyte dysfunctions were evidenced in the majority of cases, whereas lymphocytes appeared to be unaffected. Phagocyte dysfunctions comprised in vivo mobilization and motility, in vitro random and directed migration, and one or several component functions of the "metabolic" ("respiratory") burst. On the basis of the available data it is impossible to know whether a primary functional deficit of the glucose 6-phosphate transport protein of the microsomal glucose 6-phosphatase system, as demonstrated in liver, also exists in these phagocytic cells and is responsible for this dysfunction.

Comparison of chromosomal protein patterns of thymus and liver in cattle, sheep, goats and pigs.

Chromosomal proteins in the thymus and liver tissues of cattle, sheep, goats and pigs were analyzed electrophoretically. Only minor differences in histone H1 subfractions could be detected between the four species. In the 300 mM NaCl soluble fraction of nonhistone chromosomal proteins (NHCP), tissue- and species-specific qualitative and quantitative differences were found in the protein patterns. The potential practical application of the study of chromosomal proteins to animal breeding is discussed.