D-Galactose

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Stanton Segal - One of the best experts on this subject based on the ideXlab platform.

  • Evidence for function of UDP galactose pyrophosphorylase in mice with absent galactose-1-phosphate uridyltransferase
    Molecular Genetics and Metabolism, 2007
    Co-Authors: Suzanne L. Wehrli, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract Mice with deletion of the galactose-1-phosphate uridyltransferase (GALT) gene were examined for their ability to form 13 C labeled hepatic UDP glucose from administered 1- 13 C galactose. NMR analysis of urinary acetaminophen glucuronide, which is derived from hepatic UDP glucose showed 13 C enrichment after concomitant administration of 13 C galactose and acetaminophen. The finding is consistent with the function of UDP galactose pyrophosphorylase as an alternate pathway of galactose metabolism.

  • UDP-galactose pyrophosphorylase in mice with galactose-1-phosphate uridyltransferase deficiency.
    Molecular Genetics and Metabolism, 2005
    Co-Authors: Nancy D Leslie, Claire Yager, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract UDP-glucose pyrophosphorylase (E.C. 2.7.7.9), encoded by ugp , provides UDP-glucose which is critical to the synthesis of glycogen, and also catalyzes the reaction between UTP and galactose-1-phosphate, yielding UDP-galactose. This activity of UDP-gal pyrophosphorylase (UDP-galPP) suggests a role in an alternate pathway for galactose metabolism in patients with deficiency of galactose-1-phosphate uridyltransferase (GALT). We examined the effects of GALT deficiency and dietary galactose on UDP-glucose pyrophosphorylase (UDP-gluPP) and UDP-galactose pyrophosphorylase activity and ugp expression in liver of mice with homozygous deletion of the critical regions of galt. Activity with glucose-1-phosphate as substrate was significantly higher than that with galactose-1-phosphate. In liver from mice with GALT deficiency (G/G), UDP-galPP activity appeared to be lower than that measured in liver from control (N/N) animals. This difference disappeared when the N/N tissue homogenate was dialyzed to remove residual UDP-glucose, confirming that careful elimination of residual GALT activity is necessary, since GALT has 1000-fold greater activity toward galactose-1-phosphate than that of UDP-galPP in liver homogenates. Prior exposure to conventional mouse chow, high galactose chow, and high glucose chow did not alter UDP-glu PP or UDP-galPP activity. Steady state UGP mRNA levels were determined in tissues from normal and G/G animals. UGP expression was highest in liver, and did not differ by genotype or exposure to high galactose chow. UDP-galPP activity may account for unexplained ability to oxidize galactose in animals with no GALT activity, but is insufficient to alter accumulation of galactose metabolites.

  • Galactose Metabolism in Mice with Galactose-1-Phosphate Uridyltransferase Deficiency: Sucklings and 7-Week-Old Animals Fed a High-Galactose Diet
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Cong Ning, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    Abstract Mice deficient in galactose-1-phosphate uridyltransferase (GALT) demonstrate abnormal galactose metabolism but no obvious clinical phenotype. To further dissect the pathways of galactose metabolism in these animals, galactose oxidation and metabolite levels were studied in 16-day-old sucklings and the effect of a 4 week prior exposure to a 40% glucose or 40% galactose diet was determined in 7-week-old mice. Suckling GALT-deficient (G/G) mice slowly oxidized [1- 14 C]galactose to 14 CO 2 , 4.0% of the dose when fed and 7.9% when fasted compared to normal animals 38.3 and 36.4% in 4 h, respectively. Plasma of G/G sucklings contained 11.1 mM galactose and erythrocyte galactose 1-phosphate levels were 28.2 and 31.9 mg/dl packed cells. Galactose, galactitol, galactonate, and galactose 1-phosphate were found in G/G suckling mouse tissues. The tissue galactose concentrations were 10% or less of that in plasma, suggesting that there was limited cellular entry of galactose. In 7-week-old fasted mice with 4 weeks prior exposure to glucose or galactose-containing diet, 4-h oxidation was 12.9 and 15.0% of the administered radiolabeled galactose, respectively. Normal animals oxidized 33.9 and 37.9% of the dose when fed the same diets, respectively. The ability of G/G mice to oxidize galactose in the absence of GALT activity suggests the presence of alternate metabolic pathways for galactose disposition. G/G mice fed the galactose-free 40% glucose diet had erythrocyte galactose 1-phosphate levels ranging from 6.4 to 17.7 mg/dl packed cells and detectable galactose and galactose metabolites in tissues, suggesting that these animals endogenously produced galactose. The plasma of 40% galactose-fed G/G mice contained 9.1 mM galactose with red blood cell galactose 1-phosphate averaging 43.6 mg/dl. Tissues of these animals also contained high levels of galactose and galactose 1-phosphate. Liver contained over 4 μmol/g galactonate but little galactitol. Despite the elevated galactose and galactose 1-phosphate, the animals tolerated the high-galactose diet and were indistinguishable from normal animals, exhibiting no manifestations of galactose toxicity seen in human GALT-deficient galactosemia. The data suggest that high galactose 1-phosphate levels do not cause galactose toxicity and that high galactitol in combination with galactose 1-phosphate may be a prerequisite. Absence of GALT appears necessary but insufficient to produce human galactosemic phenotype.

  • Evidence for Alternate Galactose Oxidation in a Patient with Deletion of the Galactose-1-Phosphate Uridyltransferase Gene
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Gerard T Berry, Claire Yager, Robert Reynolds, Nancy D Leslie, Stanton Segal
    Abstract:

    Abstract The persistent, dietary-independent elevation of galactose metabolites in patients with galactose-1-phosphate uridyltransferase (GALT) deficiency is probably secondary to de novo synthesis of galactose. Relatively constant steady-state levels of galactose metabolites in patients also suggest that non-GALT metabolic pathways must function to dispose of the galactose synthesized each day. The discovery of a patient with a rare deletion of the GALT gene provided a unique opportunity to examine the availability of any alternate galactose oxidative capacity both in vivo and in vitro. Utilizing genomic DNA from the patient, Southern blot data demonstrated that 10 of the 11 GALT exons were homozygously deleted. By measurement of 13CO2 in expired air for up to 24 h after an oral bolus of [1-13C]galactose, it was demonstrated that 17% of the galactose was metabolized, a value comparable to the 3-h elimination rate in a control subject. Furthermore, lymphoblasts prepared from the patient could also convert [1-14C]galactose to 14CO2. This unique study provides the first unambiguous evidence that another pathway exists in man that can be responsible for galactose disposal. Further knowledge of this alternate galactose oxidative route and its regulation may aid in formulating new strategies for the treatment of galactosemia.

  • Galactose Metabolism by the Mouse with Galactose-1-Phosphate Uridyltransferase Deficiency
    Pediatric Research, 2000
    Co-Authors: Cong Ning, Pamela D. Mcnamara, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 μmol of [1-13C]galactose, normal animals excrete small amounts of labeled galactose and galactonate but no galactitol in urine whereas GALT-deficient mice excrete significant amounts of all of these as labeled compounds in urine. When challenged with galactose, only about 20% of the dose is excreted in urine, and even on the chow diet, significant amounts of galactose, galactonate, and galactitol are excreted in urine. These compounds are also found to be present in liver, kidney, and brain, except that galactonate is not found in brain. Galactose-1-phosphate accumulates in red blood cells to levels found in humans exposed to large amounts of galactose, and galactose-1-phosphate is found in increased amounts in liver, kidney, and brain of GALT-deficient animals. There was no difference in the hepatic concentration of uridine diphosphate galactose and uridine diphosphate glucose between normal and GALT-deficient mice. The explanation for the presence of galactose and its conversion products in tissues and urine of affected mice appears to be related to the presence of approximately 1.75% of galactose-containing carbohydrates in the chow, which becomes bioavailable to mice. Despite the presence of galactose and its metabolites in tissues and urine and impaired ability to oxidize the sugar, the GALT-deficient animals are indistinguishable from normal animals and do not exhibit the phenotype of humans with GALT-deficiency galactosemia.

Deborah J. Burns - One of the best experts on this subject based on the ideXlab platform.

  • formation of nucleoside diphosphate monosaccharides ndp sugars by the agarophyte pterocladia capillacea rhodophyceae 1
    Journal of Phycology, 1991
    Co-Authors: Steven L. Manley, Deborah J. Burns
    Abstract:

    The following nucleoside diphosphate monosaccharides (sugar nucleotides) were identified by HPLC from Pterocladia capillacea Born and Thur.: ADP-glucose, UDP-glucose, UDP-D-Galactose, and GDP-glucose + mannose. GDP-l-galactose was not identified due to the lack of a standard. Several extraction methods were evaluated for their efficacy. A freeze/ thaw (liquid N2) step fallowed by formic acid (1 M) extraction, reduced pressure evaporation, and solubilization in water was the preferred method. Differences in media nitrate that resulted in different tissue-N levels (1.8, 2.3, and 3.5% dry wt) and agar yields (34, 31, and 28% dry wt, respectively) also resulted in a marked difference in UDP-D-Galactose and ADP-glucose tissue levels (decrease with increasing tissue-N) while the levels of the other sugar nucleotide agar precursors remained unchanged. Activities of UDP-glucose, GDP-glucose, and GDP-mannose pyrophosphorylases, and UDP-D-glucose-4-epimerase were detected in cell-free extracts using unlabeled and 14C-labeled substrates. This study-strongly supports the proposition that the D-Galactose component of agar is synthesized via G-1-P UDP-glucose UDP-D-Galactose and that, the l-galactoae component is produced via mannose-1-P GDP-mannose GDP-l-galactose.

  • FORMATION OF NUCLEOSIDE DIPHOSPHATE MONOSACCHARIDES (NDP‐SUGARS) BY THE AGAROPHYTE PTEROCLADIA CAPILLACEA (RHODOPHYCEAE)1
    Journal of Phycology, 1991
    Co-Authors: Steven L. Manley, Deborah J. Burns
    Abstract:

    The following nucleoside diphosphate monosaccharides (sugar nucleotides) were identified by HPLC from Pterocladia capillacea Born and Thur.: ADP-glucose, UDP-glucose, UDP-D-Galactose, and GDP-glucose + mannose. GDP-l-galactose was not identified due to the lack of a standard. Several extraction methods were evaluated for their efficacy. A freeze/ thaw (liquid N2) step fallowed by formic acid (1 M) extraction, reduced pressure evaporation, and solubilization in water was the preferred method. Differences in media nitrate that resulted in different tissue-N levels (1.8, 2.3, and 3.5% dry wt) and agar yields (34, 31, and 28% dry wt, respectively) also resulted in a marked difference in UDP-D-Galactose and ADP-glucose tissue levels (decrease with increasing tissue-N) while the levels of the other sugar nucleotide agar precursors remained unchanged. Activities of UDP-glucose, GDP-glucose, and GDP-mannose pyrophosphorylases, and UDP-D-glucose-4-epimerase were detected in cell-free extracts using unlabeled and 14C-labeled substrates. This study-strongly supports the proposition that the D-Galactose component of agar is synthesized via G-1-P UDP-glucose UDP-D-Galactose and that, the l-galactoae component is produced via mannose-1-P GDP-mannose GDP-l-galactose.

Robert Reynolds - One of the best experts on this subject based on the ideXlab platform.

  • Evidence for function of UDP galactose pyrophosphorylase in mice with absent galactose-1-phosphate uridyltransferase
    Molecular Genetics and Metabolism, 2007
    Co-Authors: Suzanne L. Wehrli, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract Mice with deletion of the galactose-1-phosphate uridyltransferase (GALT) gene were examined for their ability to form 13 C labeled hepatic UDP glucose from administered 1- 13 C galactose. NMR analysis of urinary acetaminophen glucuronide, which is derived from hepatic UDP glucose showed 13 C enrichment after concomitant administration of 13 C galactose and acetaminophen. The finding is consistent with the function of UDP galactose pyrophosphorylase as an alternate pathway of galactose metabolism.

  • UDP-galactose pyrophosphorylase in mice with galactose-1-phosphate uridyltransferase deficiency.
    Molecular Genetics and Metabolism, 2005
    Co-Authors: Nancy D Leslie, Claire Yager, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract UDP-glucose pyrophosphorylase (E.C. 2.7.7.9), encoded by ugp , provides UDP-glucose which is critical to the synthesis of glycogen, and also catalyzes the reaction between UTP and galactose-1-phosphate, yielding UDP-galactose. This activity of UDP-gal pyrophosphorylase (UDP-galPP) suggests a role in an alternate pathway for galactose metabolism in patients with deficiency of galactose-1-phosphate uridyltransferase (GALT). We examined the effects of GALT deficiency and dietary galactose on UDP-glucose pyrophosphorylase (UDP-gluPP) and UDP-galactose pyrophosphorylase activity and ugp expression in liver of mice with homozygous deletion of the critical regions of galt. Activity with glucose-1-phosphate as substrate was significantly higher than that with galactose-1-phosphate. In liver from mice with GALT deficiency (G/G), UDP-galPP activity appeared to be lower than that measured in liver from control (N/N) animals. This difference disappeared when the N/N tissue homogenate was dialyzed to remove residual UDP-glucose, confirming that careful elimination of residual GALT activity is necessary, since GALT has 1000-fold greater activity toward galactose-1-phosphate than that of UDP-galPP in liver homogenates. Prior exposure to conventional mouse chow, high galactose chow, and high glucose chow did not alter UDP-glu PP or UDP-galPP activity. Steady state UGP mRNA levels were determined in tissues from normal and G/G animals. UGP expression was highest in liver, and did not differ by genotype or exposure to high galactose chow. UDP-galPP activity may account for unexplained ability to oxidize galactose in animals with no GALT activity, but is insufficient to alter accumulation of galactose metabolites.

  • Galactose Metabolism in Mice with Galactose-1-Phosphate Uridyltransferase Deficiency: Sucklings and 7-Week-Old Animals Fed a High-Galactose Diet
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Cong Ning, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    Abstract Mice deficient in galactose-1-phosphate uridyltransferase (GALT) demonstrate abnormal galactose metabolism but no obvious clinical phenotype. To further dissect the pathways of galactose metabolism in these animals, galactose oxidation and metabolite levels were studied in 16-day-old sucklings and the effect of a 4 week prior exposure to a 40% glucose or 40% galactose diet was determined in 7-week-old mice. Suckling GALT-deficient (G/G) mice slowly oxidized [1- 14 C]galactose to 14 CO 2 , 4.0% of the dose when fed and 7.9% when fasted compared to normal animals 38.3 and 36.4% in 4 h, respectively. Plasma of G/G sucklings contained 11.1 mM galactose and erythrocyte galactose 1-phosphate levels were 28.2 and 31.9 mg/dl packed cells. Galactose, galactitol, galactonate, and galactose 1-phosphate were found in G/G suckling mouse tissues. The tissue galactose concentrations were 10% or less of that in plasma, suggesting that there was limited cellular entry of galactose. In 7-week-old fasted mice with 4 weeks prior exposure to glucose or galactose-containing diet, 4-h oxidation was 12.9 and 15.0% of the administered radiolabeled galactose, respectively. Normal animals oxidized 33.9 and 37.9% of the dose when fed the same diets, respectively. The ability of G/G mice to oxidize galactose in the absence of GALT activity suggests the presence of alternate metabolic pathways for galactose disposition. G/G mice fed the galactose-free 40% glucose diet had erythrocyte galactose 1-phosphate levels ranging from 6.4 to 17.7 mg/dl packed cells and detectable galactose and galactose metabolites in tissues, suggesting that these animals endogenously produced galactose. The plasma of 40% galactose-fed G/G mice contained 9.1 mM galactose with red blood cell galactose 1-phosphate averaging 43.6 mg/dl. Tissues of these animals also contained high levels of galactose and galactose 1-phosphate. Liver contained over 4 μmol/g galactonate but little galactitol. Despite the elevated galactose and galactose 1-phosphate, the animals tolerated the high-galactose diet and were indistinguishable from normal animals, exhibiting no manifestations of galactose toxicity seen in human GALT-deficient galactosemia. The data suggest that high galactose 1-phosphate levels do not cause galactose toxicity and that high galactitol in combination with galactose 1-phosphate may be a prerequisite. Absence of GALT appears necessary but insufficient to produce human galactosemic phenotype.

  • Evidence for Alternate Galactose Oxidation in a Patient with Deletion of the Galactose-1-Phosphate Uridyltransferase Gene
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Gerard T Berry, Claire Yager, Robert Reynolds, Nancy D Leslie, Stanton Segal
    Abstract:

    Abstract The persistent, dietary-independent elevation of galactose metabolites in patients with galactose-1-phosphate uridyltransferase (GALT) deficiency is probably secondary to de novo synthesis of galactose. Relatively constant steady-state levels of galactose metabolites in patients also suggest that non-GALT metabolic pathways must function to dispose of the galactose synthesized each day. The discovery of a patient with a rare deletion of the GALT gene provided a unique opportunity to examine the availability of any alternate galactose oxidative capacity both in vivo and in vitro. Utilizing genomic DNA from the patient, Southern blot data demonstrated that 10 of the 11 GALT exons were homozygously deleted. By measurement of 13CO2 in expired air for up to 24 h after an oral bolus of [1-13C]galactose, it was demonstrated that 17% of the galactose was metabolized, a value comparable to the 3-h elimination rate in a control subject. Furthermore, lymphoblasts prepared from the patient could also convert [1-14C]galactose to 14CO2. This unique study provides the first unambiguous evidence that another pathway exists in man that can be responsible for galactose disposal. Further knowledge of this alternate galactose oxidative route and its regulation may aid in formulating new strategies for the treatment of galactosemia.

  • Galactose Metabolism by the Mouse with Galactose-1-Phosphate Uridyltransferase Deficiency
    Pediatric Research, 2000
    Co-Authors: Cong Ning, Pamela D. Mcnamara, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 μmol of [1-13C]galactose, normal animals excrete small amounts of labeled galactose and galactonate but no galactitol in urine whereas GALT-deficient mice excrete significant amounts of all of these as labeled compounds in urine. When challenged with galactose, only about 20% of the dose is excreted in urine, and even on the chow diet, significant amounts of galactose, galactonate, and galactitol are excreted in urine. These compounds are also found to be present in liver, kidney, and brain, except that galactonate is not found in brain. Galactose-1-phosphate accumulates in red blood cells to levels found in humans exposed to large amounts of galactose, and galactose-1-phosphate is found in increased amounts in liver, kidney, and brain of GALT-deficient animals. There was no difference in the hepatic concentration of uridine diphosphate galactose and uridine diphosphate glucose between normal and GALT-deficient mice. The explanation for the presence of galactose and its conversion products in tissues and urine of affected mice appears to be related to the presence of approximately 1.75% of galactose-containing carbohydrates in the chow, which becomes bioavailable to mice. Despite the presence of galactose and its metabolites in tissues and urine and impaired ability to oxidize the sugar, the GALT-deficient animals are indistinguishable from normal animals and do not exhibit the phenotype of humans with GALT-deficiency galactosemia.

Gerard T Berry - One of the best experts on this subject based on the ideXlab platform.

  • Galactose Metabolism in Mice with Galactose-1-Phosphate Uridyltransferase Deficiency: Sucklings and 7-Week-Old Animals Fed a High-Galactose Diet
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Cong Ning, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    Abstract Mice deficient in galactose-1-phosphate uridyltransferase (GALT) demonstrate abnormal galactose metabolism but no obvious clinical phenotype. To further dissect the pathways of galactose metabolism in these animals, galactose oxidation and metabolite levels were studied in 16-day-old sucklings and the effect of a 4 week prior exposure to a 40% glucose or 40% galactose diet was determined in 7-week-old mice. Suckling GALT-deficient (G/G) mice slowly oxidized [1- 14 C]galactose to 14 CO 2 , 4.0% of the dose when fed and 7.9% when fasted compared to normal animals 38.3 and 36.4% in 4 h, respectively. Plasma of G/G sucklings contained 11.1 mM galactose and erythrocyte galactose 1-phosphate levels were 28.2 and 31.9 mg/dl packed cells. Galactose, galactitol, galactonate, and galactose 1-phosphate were found in G/G suckling mouse tissues. The tissue galactose concentrations were 10% or less of that in plasma, suggesting that there was limited cellular entry of galactose. In 7-week-old fasted mice with 4 weeks prior exposure to glucose or galactose-containing diet, 4-h oxidation was 12.9 and 15.0% of the administered radiolabeled galactose, respectively. Normal animals oxidized 33.9 and 37.9% of the dose when fed the same diets, respectively. The ability of G/G mice to oxidize galactose in the absence of GALT activity suggests the presence of alternate metabolic pathways for galactose disposition. G/G mice fed the galactose-free 40% glucose diet had erythrocyte galactose 1-phosphate levels ranging from 6.4 to 17.7 mg/dl packed cells and detectable galactose and galactose metabolites in tissues, suggesting that these animals endogenously produced galactose. The plasma of 40% galactose-fed G/G mice contained 9.1 mM galactose with red blood cell galactose 1-phosphate averaging 43.6 mg/dl. Tissues of these animals also contained high levels of galactose and galactose 1-phosphate. Liver contained over 4 μmol/g galactonate but little galactitol. Despite the elevated galactose and galactose 1-phosphate, the animals tolerated the high-galactose diet and were indistinguishable from normal animals, exhibiting no manifestations of galactose toxicity seen in human GALT-deficient galactosemia. The data suggest that high galactose 1-phosphate levels do not cause galactose toxicity and that high galactitol in combination with galactose 1-phosphate may be a prerequisite. Absence of GALT appears necessary but insufficient to produce human galactosemic phenotype.

  • Evidence for Alternate Galactose Oxidation in a Patient with Deletion of the Galactose-1-Phosphate Uridyltransferase Gene
    Molecular Genetics and Metabolism, 2001
    Co-Authors: Gerard T Berry, Claire Yager, Robert Reynolds, Nancy D Leslie, Stanton Segal
    Abstract:

    Abstract The persistent, dietary-independent elevation of galactose metabolites in patients with galactose-1-phosphate uridyltransferase (GALT) deficiency is probably secondary to de novo synthesis of galactose. Relatively constant steady-state levels of galactose metabolites in patients also suggest that non-GALT metabolic pathways must function to dispose of the galactose synthesized each day. The discovery of a patient with a rare deletion of the GALT gene provided a unique opportunity to examine the availability of any alternate galactose oxidative capacity both in vivo and in vitro. Utilizing genomic DNA from the patient, Southern blot data demonstrated that 10 of the 11 GALT exons were homozygously deleted. By measurement of 13CO2 in expired air for up to 24 h after an oral bolus of [1-13C]galactose, it was demonstrated that 17% of the galactose was metabolized, a value comparable to the 3-h elimination rate in a control subject. Furthermore, lymphoblasts prepared from the patient could also convert [1-14C]galactose to 14CO2. This unique study provides the first unambiguous evidence that another pathway exists in man that can be responsible for galactose disposal. Further knowledge of this alternate galactose oxidative route and its regulation may aid in formulating new strategies for the treatment of galactosemia.

  • Galactose Metabolism by the Mouse with Galactose-1-Phosphate Uridyltransferase Deficiency
    Pediatric Research, 2000
    Co-Authors: Cong Ning, Pamela D. Mcnamara, Claire Yager, Robert Reynolds, Nancy D Leslie, Gerard T Berry, Jie Chen, Stanton Segal
    Abstract:

    The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 μmol of [1-13C]galactose, normal animals excrete small amounts of labeled galactose and galactonate but no galactitol in urine whereas GALT-deficient mice excrete significant amounts of all of these as labeled compounds in urine. When challenged with galactose, only about 20% of the dose is excreted in urine, and even on the chow diet, significant amounts of galactose, galactonate, and galactitol are excreted in urine. These compounds are also found to be present in liver, kidney, and brain, except that galactonate is not found in brain. Galactose-1-phosphate accumulates in red blood cells to levels found in humans exposed to large amounts of galactose, and galactose-1-phosphate is found in increased amounts in liver, kidney, and brain of GALT-deficient animals. There was no difference in the hepatic concentration of uridine diphosphate galactose and uridine diphosphate glucose between normal and GALT-deficient mice. The explanation for the presence of galactose and its conversion products in tissues and urine of affected mice appears to be related to the presence of approximately 1.75% of galactose-containing carbohydrates in the chow, which becomes bioavailable to mice. Despite the presence of galactose and its metabolites in tissues and urine and impaired ability to oxidize the sugar, the GALT-deficient animals are indistinguishable from normal animals and do not exhibit the phenotype of humans with GALT-deficiency galactosemia.

  • Apparent Galactose Appearance Rate in Human Galactosemia Based on Plasma [13C]Galactose Isotopic Enrichment
    Molecular Genetics and Metabolism, 2000
    Co-Authors: Cong Ning, P. Thomas Fenn, Ian A. Blair, Gerard T Berry, Stanton Segal
    Abstract:

    Abstract Determination of endogenous galactose formation in galactosemic subjects provides important information in understanding the etiology of the long-term complications. To accomplish this task a sensitive method for measurement of isotopic enrichment of plasma galactose was developed. The aldononitrile pentaacetate derivative of galactose was utilized for gas chromatography/mass spectrometry analysis. Using a phenyl-methylsilicone capillary column, adequate separation of galactose from glucose was obtained by temperature programming of the chromatography. The specific fragmentation pattern of m/z 212, 225, 314 from d-[ 12 C]galactose and m/z 213, 226, 315 from l-[ 13 C]galactose was used for the galactose enrichment measurement by atom percent excess (APE). There was good correlation between expected enrichment and determined APEs at galactose concentrations of 1, 2, and 5 μmol/L with a coefficient of variation ranging from 0.22 to 7.17%. The method provides an accurate estimation of plasma [ 13 C]galactose enrichment from which the galactose production rate can be calculated. The steady-state plasma l-[ 13 C]galactose isotopic enrichment of three individuals with galactosemia, two males ages 33 and 13, and one female age 9, during constant infusion of l-[ 13 C]galactose was 55, 41, and 55%, allowing the estimation of the apparent galactose appearance rate of 0.62, 1.09, and 0.82 mg/kg/h, respectively. The reanalysis of three previous studies by the present method found that APE values determined by the method then employed, butylboronate acetate derivatization, were systemically lower than those determined with aldononitrile pentaacetate derivatization, making for an overestimation of the apparent galactose appearance rate. The small plasma sample volumes needed make it feasible to perform these studies in infants and young children with galactosemia.

  • elevation of erythrocyte redox potential linked to galactonate biosynthesis elimination by tolrestat
    Metabolism-clinical and Experimental, 1998
    Co-Authors: Robert Reynolds, Suzanne Wehrli, Gerard T Berry, Michael J Palmieri
    Abstract:

    Alternate pathways of galactose metabolism were explored in erythrocytes from normal subjects and patients with galactose-1-phosphate uridylyltransferase (GALT) deficiency incubated with galactose. Micromolar quantities of galactonate accumulated in both normal and mutant cells linearly with time up to 5 hours and with concentrations of galactose up to 25 mmol/L. Galactitol also was found at levels less than one third of the galactonate level, while galactose-1-phosphate concentrations comparable to those of galactonate were found in galactosemic cells. Concomitant with the formation of these galactose metabolites, the erythrocyte redox potential based on measurement of lactate and pyruvate increased fourfold in both cell types. This was due to a 60% to 72% decrease in pyruvate and a 24% to 26% increase in lactate. The oxidation of galactose to galactonate, which is known to generate NADH, is the most likely explanation for the increase in the redox state. The aldose reductase inhibitor (ARI), Tolrestat (Wyeth Ayerst Research, Princeton, NJ), at 70 μmol/L inhibited the formation of both galactonate and galactitol in both cell types without affecting galactose-1-phosphate, and eliminated the increase in the redox potential as indicated by restoration of pyruvate and lactate levels to the levels obtained before exposure of the cells to galactose. A functioning galactonate pathway is a route of galactose disposal in patients with GALT deficiency, but by altering the cellular redox potential, it may also contribute to galactose toxicity.

Steven L. Manley - One of the best experts on this subject based on the ideXlab platform.

  • formation of nucleoside diphosphate monosaccharides ndp sugars by the agarophyte pterocladia capillacea rhodophyceae 1
    Journal of Phycology, 1991
    Co-Authors: Steven L. Manley, Deborah J. Burns
    Abstract:

    The following nucleoside diphosphate monosaccharides (sugar nucleotides) were identified by HPLC from Pterocladia capillacea Born and Thur.: ADP-glucose, UDP-glucose, UDP-D-Galactose, and GDP-glucose + mannose. GDP-l-galactose was not identified due to the lack of a standard. Several extraction methods were evaluated for their efficacy. A freeze/ thaw (liquid N2) step fallowed by formic acid (1 M) extraction, reduced pressure evaporation, and solubilization in water was the preferred method. Differences in media nitrate that resulted in different tissue-N levels (1.8, 2.3, and 3.5% dry wt) and agar yields (34, 31, and 28% dry wt, respectively) also resulted in a marked difference in UDP-D-Galactose and ADP-glucose tissue levels (decrease with increasing tissue-N) while the levels of the other sugar nucleotide agar precursors remained unchanged. Activities of UDP-glucose, GDP-glucose, and GDP-mannose pyrophosphorylases, and UDP-D-glucose-4-epimerase were detected in cell-free extracts using unlabeled and 14C-labeled substrates. This study-strongly supports the proposition that the D-Galactose component of agar is synthesized via G-1-P UDP-glucose UDP-D-Galactose and that, the l-galactoae component is produced via mannose-1-P GDP-mannose GDP-l-galactose.

  • FORMATION OF NUCLEOSIDE DIPHOSPHATE MONOSACCHARIDES (NDP‐SUGARS) BY THE AGAROPHYTE PTEROCLADIA CAPILLACEA (RHODOPHYCEAE)1
    Journal of Phycology, 1991
    Co-Authors: Steven L. Manley, Deborah J. Burns
    Abstract:

    The following nucleoside diphosphate monosaccharides (sugar nucleotides) were identified by HPLC from Pterocladia capillacea Born and Thur.: ADP-glucose, UDP-glucose, UDP-D-Galactose, and GDP-glucose + mannose. GDP-l-galactose was not identified due to the lack of a standard. Several extraction methods were evaluated for their efficacy. A freeze/ thaw (liquid N2) step fallowed by formic acid (1 M) extraction, reduced pressure evaporation, and solubilization in water was the preferred method. Differences in media nitrate that resulted in different tissue-N levels (1.8, 2.3, and 3.5% dry wt) and agar yields (34, 31, and 28% dry wt, respectively) also resulted in a marked difference in UDP-D-Galactose and ADP-glucose tissue levels (decrease with increasing tissue-N) while the levels of the other sugar nucleotide agar precursors remained unchanged. Activities of UDP-glucose, GDP-glucose, and GDP-mannose pyrophosphorylases, and UDP-D-glucose-4-epimerase were detected in cell-free extracts using unlabeled and 14C-labeled substrates. This study-strongly supports the proposition that the D-Galactose component of agar is synthesized via G-1-P UDP-glucose UDP-D-Galactose and that, the l-galactoae component is produced via mannose-1-P GDP-mannose GDP-l-galactose.