Galactose metabolites in blood from neonates with and without hypergalactosaemia detected by mass screening.

UNLABELLED: Concentrations of galactose (Gal) in plasma and galactose metabolites in red blood cells (RBC) were determined in 18 normal neonates and 249 others with hypergalactosaemia according to the Paigen method. Normal neonatal values for plasma Gal, RBC galactose-1-phosphate (Gal-1-P), RBC uridine diphosphate glucose (UDP-Glc), and RBC uridine diphosphate galactose (UDP-Gal) were 0.96 +/- 0.71 mg/dl, 1.69 +/- 1.45 mg/dl of packed RBC, 1.00 +/- 0.45 mg/dl of packed RBC, and 1.44 +/- 0.45 mg/dl of packed RBC, respectively. The UDP-Gal concentration was higher and the UDP-Glc concentration lower than previously reported in normal children. Of the 249 cases with excessive Gal in whole blood, 23 showed high Gal concentrations in plasma; among these, four portacaval shunts and one case of congenital biliary atresia were diagnosed. In subjects homozygous or heterozygous for UDP-Gal-4 epimerase deficiency, concentrations of UDP-Gal and Gal-1-P were elevated only in RBC, corresponding to restriction of the metabolic abnormality to these cells. Most cases of hypergalactosaemia detected by the Paigen method have large excesses of Gal-1-P in RBC. Although a specific diagnosis based solely on blood Gal metabolites is difficult, individual concentrations reflect underlying conditions to some extent. CONCLUSION: In neonates, uridine diphosphate galactose concentrations were higher and uridine diphosphate glucose concentrations were lower than previously reported paediatric values. Patients with high plasma galactose concentrations should be investigated by hepatic imaging.

Insulin and glucosamine infusions increase O-linked N-acetyl-glucosamine in skeletal muscle proteins in vivo.

O-linked N-acetylglucosamine (O-GlcNAc) is an abundant posttranslational modification of serine/threonine residues of nuclear and cytoplasmic proteins. We determined whether insulin or coinfusion of glucosamine (GlcN) with insulin alters O-GlcNAc of skeletal muscle proteins. Three groups of conscious fasted rats received 6-hour infusions of either saline (BAS), insulin 18 mU/kg.min and saline (INS), or insulin and GlcN 30 micromol/kg.min (GLCN) during maintenance of normoglycemia. At 6 hours, the concentrations of muscle UDP-GlcNAc, UDP-N-acetylgalactosamine (UDP-GalNAc), UDP-glucose (UDP-Glc), UDP-galactose (UDP-Gal), glycogen, and N and O-linked GlcNAc (galactosyltransferase labeling followed by beta elimination) were measured in freeze-clamped abdominis muscle. Insulin increased whole-body glucose uptake from 49 +/- 5 to 239 +/- 8 micromol/kg.min (P < .001) and glycogen in abdominis muscle from 138 +/- 11 to 370 +/- 26 mmol/kg dry weight (P < .001). Insulin increased the amount of cytosolic N - and O-linked GlcNAc by 56% from 362 +/- 30 to 564 +/- 45 dpm/microg protein . 100 min (P < .02), and O-GlcNAc from 221 +/- 16 to 339 +/- 27 dpm/microg . 100 min (P < .02). Glycogen content was positively correlated with the amount of total (r = .90, P < .005) and O-linked GlcNAc in insulin-infused animals. Coinfusion of GlcN with insulin increased muscle UDP-GlcNAc about fourfold (100 +/- 6 nmol/g) compared with insulin (27 +/- 1, P < .001) or saline (25 +/- 1, P < .001) infusion. GlcN also decreased glucose uptake over 6 hours by 30% to 168 +/- 8 micromol/kg . min (P < .001 for GLCN v INS) and muscle glycogen to 292 +/- 24 mmol/kg dry weight (P < .05 for GLCN v INS). Both total (635 +/- 60 dpm/microg . 100 min, P < .002) and O-linked GlcNAc (375 +/- 36 dpm/microg . 100 min, P < .002) in the cytosol were significantly higher in GLCN rats (635 +/- 60 dpm/microg) versus BAS rats (P < .002). As in INS rats, muscle glycogen and O-GlcNAc were positively correlated in GLCN rats (r = .54, P < .05). Variation in total and O-linked GlcNAc in GLCN rats was due both to GlcN (P < .02) and to variation in the glycogen content (P < .005).

Sugar nucleotide concentrations in red blood cells of patients on protein- and lactose-limited diets: effect of galactose supplementation.

Uridine diphosphate (UDP) galactose, a pivotal compound in the metabolism of galactose, is the obligate donor of galactose in the formation of complex glycoconjugates. The cellular UDPgalactose concentration has been thought to be maintained by the interconversion of UDPglucose and UDPgalactose by UDPgalactose-4-epimerase. However, recent findings of lower average red blood cell (RBC) UDPgalactose concentrations in galactose-1-phosphate uridyltransferase-deficient patients suggest that other factors play a role in determining its concentration. To test the hypothesis that the amount of galactose traversing the Leloir pathway contributes to the cellular UDPgalactose pool, we determined RBC UDPgalactose in patients with maple syrup urine disease (MSUD), phenylketonuria (PKU), and other metabolic diseases who were treated with a low-protein, and consequently, low-lactose diet. Six patients with MSUD were also supplemented with 19 g galactose/d and their UDPhexose concentrations were measured at intervals. We show that young patients with MSUD or PKU have decreased average RBC UDPgalactose concentrations when compared with similarly aged healthy subjects. Galactose supplementation of MSUD patients significantly increased their UDPgalactose concentrations in both RBCs and white blood cells (WBCs) from 29.5 +/- 1.5 to 42.3 +/- 5.8 nmol/g hemoglobin and from 69.0 +/- 7.5 to 193.0 +/- 49.0 nmol/g protein, respectively. Discontinuation of supplementation was associated with a return to basal values in RBCs and a reattainment of the pretreatment ratio of UDPglucose to UDPgalactose in WBCs. These observations demonstrate that dietary galactose is a factor in establishing the steady state concentrations of the uridine sugar nucleotides and imply that galactose metabolism modulates the achievement of an epimerase-mediated equilibrium.

Effect of glucose and galactose loading in normal subjects on red and white blood cell uridine diphosphate sugars.

In order to test the assumption that red blood cell (RBC) uridine diphosphate galactose content is regulated in part by dietary galactose and to help comprehend factors influencing RBC and white blood cell (WBC) uridine diphosphate hexose concentrations in vivo, oral loading studies were performed with 50 g of galactose or 75 g of glucose in normal adults. While elevations of blood glucose did not influence RBC or WBC UDPhexose levels, increased blood galactose concentrations caused transient increases in both RBC and WBC UDPgalactose. In both RBC and WBC, the UDPgalactose-4-epimerase was rate limiting. In comparison to RBC, WBC had larger changes in UDPgalactose levels, synthesized additional UDPglucose through the action of UDPglucose pyrophosphorylase and began to restore the equilibrium ratio between UDPglucose and UDPgalactose concentrations while the plasma galactose level was still increasing. Thus, galactose ingestion alters the steady-state levels of UDPhexoses in circulating cells. The modulation of UDPglucose and UDPgalactose concentrations, occurring after the presentation of galactose to cells, as a result of the combined actions of GALT and UDPgalactose-4-epimerase, may be important in determining rates of synthesis of complex glycoconjugates.

Comparison of erythrocyte uridine sugar nucleotide levels in normals, classic galactosemics, and patients with other metabolic disorders.

By limiting galactosylation mechanisms, a cellular deficiency of the uridine sugar nucleotide, UDPgalactose, has been implicated as a cause of the long-term complications seen in patients with classic galactosemia despite dietary treatment. As a result, great interest has been generated in the accurate assessment of UDPgalactose, as well as UDPglucose, from which UDPgalactose may be derived by the function of a ubiquitous, active UDPgalactose-4-epimerase. Since several series of values for the concentration of these compounds in red blood cells (RBCs) of galactosemics have been flawed by the use of methods subsequently shown to be unsuitable, we have quantified erythrocyte UDPgalactose and UDPglucose levels by an accurate high-performance liquid chromatography (HPLC) assay in 116 normals, 76 galactosemics, and 39 patients with other metabolic disorders. These large groups have permitted the evaluation of age, diet, and genotype as influential factors in the steady-state RBC levels of the sugar nucleotides. The data show that age is an important determinant of RBC levels, with children younger than 10 years having higher values than individuals older than 10 years. Mean UDPgalactose levels in galactosemic children younger than 10 years and those older than 10 years were 30% and 18% lower, respectively, than levels in comparable normals. Although the mean differences were highly significant, there was considerable overlap of individual values. There was no difference in UDPglucose levels between galactosemics and normals.(ABSTRACT TRUNCATED AT 250 WORDS)

Defective galactosylation in galactosemia: is low cell UDPgalactose an explanation?

There is circumstantial evidence that defective galactosylation of complex glycoconjugates exists in tissues from galactosemic patients. Whether this is an etiologic factor in the long-term complications of the disorder is not known. Also not evident is the basis for the impaired galactosylation. The hypothesis that abnormally low cellular uridine diphosphate galactose (UDPgal) content is responsible has not been established. There is a tendency for galactosemic red cell UDPgal to be in the low normal range with a high uridine diphosphate glucose to UDP-gal ratio. This may reflect an inability of red cell UDPgal-4'-epimerase to maintain a normal ratio and consequently higher levels of UDPgal. In the more complex white blood cells and cultured fibroblasts, the UDPgal content and the uridine diphosphate glucose to UDPgal ratio of galactosemics are normal. Therefore, defective galactosylation observed in galactosemic fibroblasts must result from a defect in the transfer of galactose from UDPgal to these moieties.

Measurements of uridine diphosphate glucose and uridine diphosphate galactose--an appraisal.

The recent disproof of a major deficiency of uridine diphosphate galactose in galactosemia should not lead investigators to assume either that enzymatic methods are unreliable for uridine sugar assays or that a defect in galactosylation in galactosemia has been excluded.

Uridine diphosphate hexoses in leukocytes and fibroblasts of classic galactosemics and patients with other metabolic diseases.

To examine uridine diphosphate hexose (UDPhexose) content of cells that have more complete metabolic patterns than erythrocytes, which have been commonly used in the study of galactosemia, the concentrations of uridine diphosphate galactose (UDPgalactose) and uridine diphosphate glucose (UDPglucose) were determined in white blood cells (WBC) and fibroblasts cultured from skin biopsies. Leukocyte UDPgalactose and UDPglucose values were determined in 60 normal individuals, 14 classic galactosemics, and 18 patients with other metabolic diseases on protein-restricted and low-lactose diets. There was no difference in the average concentration of these compounds between any of these groups. There was no relationship between age and WBC UDPhexose content or correlation of WBC and erythrocyte UDPhexose levels in the same blood specimens. WBC from galactosemic individuals differ from their red blood cells because the former do not show the low average UDPgalactose levels and abnormal UDPglucose to UDPgalactose ratio previously reported for erythrocytes from galactose-1-phosphate uridyltransferase-deficient individuals. Fibroblast cell lines from 10 normal and 10 galactosemic individuals, cultured and grown to confluence in glucose medium, also showed no difference in nucleotide sugar concentrations. Thus far, of the cell types easily available, red blood cells appear to be unique in showing an abnormality in nucleotide sugar metabolism. The fact that galactosemic fibroblasts demonstrate no abnormality in the concentration of these compounds suggests that the defective galactosylation that has been observed in galactosemic fibroblasts is not due to unavailability of UDPgalactose.

Biochemical and molecular studies of 132 patients with galactosemia.

We evaluated 132 galactosemia patients for the Q188R (glutamine-188 to arginine) mutation in the human galactose-1-phosphate uridyltransferase (GALT) gene and for GALT activity in their hemolysates by a sensitive radioisotopic method. In those without any detectable GALT activity (GG), the Q188R mutation constituted 67% of the alleles. In patients with detectable GALT activity (GV), only 16% of the alleles were accounted for by Q188R. In all patients who were homozygous for the Q188R mutation, no erythrocyte GALT activity could be demonstrated. There was an extensive variation in the amount of detectable GALT activity ranging from 0.1% to 5% of the normal values among the GV patients. There was a difference in the frequency of Q188R mutation in the GALT alleles among patients belonging to different racial and ethnic groups. In Caucasian and Hispanic patients, the frequency was not far different (64% and 58%, respectively). On the other hand, only 12% of the GALT alleles with Q188R were found in African-American patients.

Uridine diphosphoglucose content of human erythrocytes: assessment by conversion to uridine diphosphoglucuronate.

To settle the ongoing controversy regarding differential uridine diphosphoglucose (UDPG) and uridine diphosphogalactose (UDPGal) content of erythrocytes, which may be important in evaluating the metabolic abnormality in patients with galactosemia, we derived a combined enzymatic-high-performance liquid chromatography (HPLC) assay. Uridine diphosphoglucuronate (UDPGA), the unique product of UDPG dehydrogenase activity, was separated and quantified by HPLC in extracts of human erythrocytes. The quantity of UDPGA produced in cell filtrates incubated with the enzyme corresponds to the amount of UDPG directly determined by HPLC. The amount of UDPGA produced was independent of the enzyme purity or activity used. On the other hand, the amounts of UDPG estimated by fluorometric measurement of the production of reduced nicotinamide adenine dinucleotide varied with the enzyme purity and activity. The combined enzymatic-HPLC method confirms the direct determinations of UDPG content of normal erythrocytes. The results indicate that, under appropriate conditions, the fluorometric-based assay will give accurate estimates of UDPG, but the direct HPLC method yields consistent and correct UDPG and UDPGal determinations.

The investigation of UDPGlucose and UDPGalactose concentration in red blood cells of patients with classical galactosaemia.

UDPGlucose (UDPGlc) and UDPGalactose (UDPGal) are nucleotide sugars formed via the galactose metabolic pathway and are essential cofactors for the incorporation of galactose and glucose into complex glycoproteins and glycolipids. It has been proposed that in classical galactosaemia, where the enzyme galactose-1-phosphate uridyl transferase is deficient, the reaction product UDPGal is reduced leading to the long-term complications associated with the disease. We have measured the concentration of UDPGal and UDPGlc in red blood cells by high performance liquid chromatography (HPLC) in 16 children and 15 adult galactosaemics and compared the results with 30 and 27 control children and adults, respectively. The results indicate that UDPGal levels were found to be significantly reduced in galactosaemic patients and UDPGlc/UDPGal ratios significantly increased.

Estimates of uridine diphosphate hexoses in erythrocytes: implications for galactosemia.

Impurities in a reagent dehydrogenase caused overestimates of erythrocytic uridine diphosphate glucose and accounted for clinically important differences in results between those of one group of investigators using enzymatic methods and those of two other groups using enzymatic methods, high-performance liquid chromatography, and nuclear magnetic resonance. These data have relevance for the current debate regarding the pathophysiologic changes in galactosemia.

Concentration of white blood cell UDPgalactose and UDPglucose determined by high performance liquid chromatography.

We have applied a HPLC method to separate and quantitate UDPgalactose (UDPGal) and UDPglucose (UDPGlu) in human white blood cells (WBCs). Trichloroacetic acid-treated, protein-free filtrates were chromatographed on an anion-exchange column (Dionex CarboPac PA-1) using a gradient of 20-40% potassium phosphate buffer (pH 4.5). Recoveries of UDPGal and UDPGlu ranged from 93 to 106%, and the method was linear over a wide range of WBC protein concentrations. Volumes of blood as low as 2.5 ml (2.2 mg WBC protein) could be used to achieve quantitative recovery of the sugar nucleotides. The mean values and standard deviations of UDPGal and UDPGlu in 33 normal individuals ranging in age from 1 day to 65 years were 12.4 +/- 4.2 and 31.5 +/- 9.3 mumol/100 g protein, respectively. No statistical differences in UDPGal and UDPGlu values were observed between children and adults. No correlation was established between the concentrations of UDPGal and UDPGlu and either total WBC count or the number of lymphocytes obtained from Coulter counter analysis. There was no relationship between the concentrations of UDPGal and UDPGlu in WBCs and RBCs which were prepared from the same blood specimen.

Long-term outcome in 134 patients with galactosaemia.

In a retrospective study 134 galactosaemic patients, born between 1955 and 1989 in the Federal Republic of Germany were traced and their long-term outcome evaluated. We investigated 83 galactosaemic patients (78 homozygotes, 5 compound heterozygotes) by clinical, psychometric and laboratory testing; 31 patients were evaluated by medical history, the remaining 20 patients had died due to sequelae of the underlying disease. In 48 out of 78 classical galactosaemia patients galactose-free therapy had been started before the 15th day, in 19 between days 15 and 56 and in 11 patients after the 56th day. Physical findings revealed that puberty was delayed in 1 out of 18 males and 6 out of 11 females. Neurological abnormalities included ataxia (n = 6), intention tremor (n = 11) and microcephaly (n = 10). Speech abnormalities were found in 43 out of 66 patients over 3 years of age and disturbance of visual perception and/or arithmetic deficits in 29. Intelligence declined with age, i.e., a DQ or IQ less than 85 was found in 4 out of 34 patients less than 6 years of age (12%), in 10 out of 18 between 7 and 12 years (56%) and in 20 out of 24 older than 12 years (83%). Metabolite patterns (RBC galactose-1-phosphate and UDP-galactose, plasma and urinary galactitol) did not correlate with DQ or IQ. Dietary compliance was good in almost all patients. Compound heterozygotes (n = 5) had normal mental and growth development and all laboratory parameters were in the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Red blood cell uridine sugar nucleotide levels in patients with classic galactosemia and other metabolic disorders.

While dietary galactose restriction eliminates the life-threatening complications of classic galactosemia, central nervous system and ovarian disease are still evident in these patients, despite milk restriction. Because of the possibility that reduced tissue levels of uridine diphosphate galactose (UDPgalactose), the product of the deficient enzyme, galactose-1-phosphate uridyltransferase, are the cause of these unexplained complications, we have measured the concentration of red blood cell (RBC) uridine sugar nucleotides in these patients, comparing their values not only with those of normal subjects, but also with those of children who have other metabolic disorders. RBC UDPgalactose and uridine diphosphate glucose (UDPglucose) levels were measured by high-performance liquid chromatography (HPLC) in 35 control subjects, 24 galactosemic patients, and 19 patients with inborn errors of amino acid, organic acid, or ammonia metabolism. The last group of patients served as dietary controls, as they were all on special low-protein diets that restricted milk intake. The mean levels of UDPgalactose in galactosemic children and adults were 38% and 54% lower, respectively, than the levels in normal children and adults. While only six of 19 galactosemic children had levels below the 95% confidence limit for normals, four of five galactosemic adults had levels of UDPgalactose in the low range. The mean UDPgalactose level in children with other metabolic diseases who were on a low-milk diet was also reduced by 38%, with a mean not significantly different from galactosemics. Compared with normal adults, the level of UDPglucose in galactosemic adults was also reduced by 29%, with three of five affected adults having UDPglucose values below the 95% confidence limit.(ABSTRACT TRUNCATED AT 250 WORDS)

31P NMR analysis of red blood cell UDPGlucose and UDPGalactose: comparison with HPLC and enzymatic methods.

The levels of uridine diphosphogalactose (UDPGal) and uridine diphosphoglucose (UDPGlu) in trichloroacetic acid extracts of human red blood cells (RBC) were measured by 31P NMR spectroscopy. Individual determinations were compared to results obtained by enzymatic and high-pressure liquid chromatographic (HPLC) methods. The characteristic doublet of the P beta resonance signals of both UDPGal and UDPGlu were detected in proton-decoupled spectra of extracts. Quantitative analyses were obtained by employing a standard, methylene diphosphonate, in an external capillary tube during data acquisition for periods of 14 to 24 h using an "inverse-gated" pulse sequence. The ratio of the integrated area of each of the uridine sugar nucleotide doublets to the area of the external reference peak was linear with concentrations between 0.03 and 0.50 mM. There was no difference between the mean value obtained by 31P NMR of 6.6 +/- 1.4 mumol UDPGlu/100 g Hgb or 2.1 +/- 0.6 mumol UDPGal/100 gHgb and the corresponding levels determined enzymatically or by HPLC in identical RBC extracts. When analyzed as paired data, only UDPGlu by NMR was found to be lower than the value obtained by HPLC. As a quantitative analytical tool, NMR spectrometry validated both the enzymatic and HPLC methods used for measurement of uridine sugar nucleotides in our laboratories.

Erythrocytic uridine diphosphate galactose in galactosaemia.

An earlier claim of a deficiency of uridine diphosphate galactose in erythrocytes of galactosaemia patients was not confirmed. Enzymic techniques similar to those of the earlier investigators were used to determine not only the concentration of uridine diphosphate galactose but also the ratio of this concentration to the sum of the uridine sugar diphosphates (uridine diphosphate galactose and uridine diphosphate glucose). The values in erythrocytes of galactosaemic subjects were similar to those of non-galactosaemic children on a galactose-restricted diet and to those of normal adults. These results cast doubt on the claim of a major deficiency of uridine diphosphate galactose in galactosaemia and on the need for treating galactosaemic children with uridine.