Pathways of NADPH in rat liver. Evidence favoring a single cytosolic pool

Rognstad, Robert

doi:10.1016/0003-9861(80)90266-0

Cited by 10 publications

(3 citation statements)

References 16 publications

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“…The pentose cycle is thought to play at least two important roles. Radioisotopic studies in liver (Wadke et al, 1973;Lakshmanan & Veech, 1977), liver cells (Rognstad, 1980) and adipocytes (Flatt & Ball, 1964;Jungas, 1968;Rognstad & Katz, 1966) indicate that the pentose cycle supplies approximately half of the required cytoplasmic NADPH. The pentose cycle also supplies ribose 5-P for nucleotide synthesis (Dickens, 1938b;Marks & Feigelson, 1957).…”

Section: Introductionmentioning

confidence: 99%

The content of pentose-cycle intermediates in liver in starved, fed ad libitum and meal-fed rats

Casazza¹,

Veech²

1986

Biochemical Journal

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Liver content of pentose-cycle intermediates and the activity of the three major cytoplasmic NADPH-producing enzymes and pentose-cycle enzymes were measured in three dietary states: 48 h-starved rats, rats fed on a standard diet ad libitum, and rats meal-fed with a low-fat high-carbohydrate diet. Measured tissue contents of pentose-cycle intermediates in starved liver were: 6-phosphogluconate, 4.7 +/- 0.5 nmol/g; ribulose 5-P, 3.7 +/- 0.5 nmol/g; xylulose 5-P, 4.3 +/- 0.4 nmol/g; sedoheptulose 7-P, 25.5 +/- 1.3 nmol/g; and combined sedoheptulose 7-P and ribose 5-P, 30.6 +/- 0.7 nmol/g. These values were in good agreement with values calculated from fructose 6-P and free glyceraldehyde 3-P, assuming the major transketolase, transaldolase, ribulose-5-P 3-epimerase and ribose-5-P isomerase reactions were all in near-equilibrium. Similar results were found in animals fed ad libitum. These relationships were not valid in animals fed on a low-fat high-carbohydrate diet, with tissue contents of metabolites in some cases being more than an order of magnitude higher than the calculated values. Measured tissue contents of pentose-cycle intermediates in these animals were: 6-phosphogluconate, 124.2 +/- 13.9 nmol/g; ribulose 5-P, 44.8 +/- 7.1 nmol/g; xylulose 5-P, 77.2 +/- 9.4 nmol/g; sedoheptulose 7-P, 129.9 +/- 10.1 nmol/g; and combined sedoheptulose 7-P and ribose 5-P, 157.0 +/- 11.3 nmol/g. In all animals, regardless of dietary state, tissue content of erythrose 4-P was less than 2 nmol/ml. Liver activities of glucose-6-P dehydrogenase and 6-phosphogluconate dehydrogenase were increased from 3.5 +/- 0.9 mumol/g and 7.3 +/- 0.5 mumol/min per g in starved animals to 13.2 +/- 1.1 and 10.5 +/- 0.7 mumol/min per g in low-fat high-carbohydrate-fed animals. Despite these changes, the activities of transaldolase (3.4 +/- 0.3 mumol/min per g), transketolase (7.8 +/- 0.2 mumol/min per g) and ribulose-5-P 3-epimerase (7.5 +/- 0.4 mumol/min per g) were not increased in meal-fed animals above those observed in starved animals (3.4 +/- 0.2, 7.1 +/- 0.3 and 8.6 +/- 0.4 mumol/min per g respectively). The increase in the activity of oxidative pentose-cycle enzymes in the absence of any change in the non-oxidative pentose cycle appeared to contribute to the observed disequilibrium in the pentose cycle in animals meal fed on a low-fat high-carbohydrate diet.

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Section: Introductionmentioning

confidence: 99%

The content of pentose-cycle intermediates in liver in starved, fed ad libitum and meal-fed rats

Casazza¹,

Veech²

1986

Biochemical Journal

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“…Furthermore, NADPH can maintain glutathione reduction and prevent cell membrane oxidation (Agledal et al, 2010). Therefore, the high expression of 6gpd may be used to produce NADPH to reduce the oxidative stress of fish caused by high levels of n-3 LC-PUFA, or to synthesis of sterols and amino acids (Rognstad, 1980), but it needs further study. In the muscle, dietary n-3 LC-PUFA significantly decreased fas activity; the expression of cpt-1, atgl and pparα genes reached the maximum in the 1.70% and 1.35% groups, respectively.…”

Section: Discussionmentioning

confidence: 99%

Dietary n‐3 long chain polyunsaturated fatty acids affect the serum biochemical parameters, lipid‐metabolism‐related of gene expression and intestinal health of juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatu )

Dong

Tan

et al. 2021

Aquacult Nutr

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To determine the effects of dietary n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) on lipid metabolism and intestinal health of juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatu), an 8-week feeding experiment was carried out using six isoproteic and isolipidic formula diets containing 0.65% (control), 1.00%, 1.35%, 1.70%, 2.05% and 2.40% n-3 LC-PUFA (dry matter). The results showed that the serum triglyceride and cholesterol reached the minimum in the 1.70% group and 1.35% group, respectively. The serum glucose content of the control group was significantly lower than that of the other groups (p < 0.05). Compared with the control group, the expression of hepatic cpt-1 gene in the 2.05% group and atgl, apob-100 genes in the 2.40% group reached the maximum and increased significantly, while fas, accα and pparγ genes in the 2.05% and 2.40% groups decreased significantly (p < 0.05). The cpt-1, atgl and pparα gene expression in the muscle increased first and then decreased, reaching the maximum in the 1.70% and 1.35% groups, while the expression of fas and pparγ significantly decreased (p < 0.05), reaching the minimum in the 2.40% and 2.05% groups, respectively. Intestinal lipase and trypsin activities in the 2.05% group reached the maximum. In the intestine microbiota, Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla. The

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“…This metabolic pathway connects hexose metabolism, mainly of glucose, with pentose metabolism. There are several metabolic functions of these pathways, the two most important being to generate reducing equivaients, in the form of NADPH, necessary in the reductive biosynthetic reactions involving fatty-acid and cholesterol synthesis (Eggleston & Krebs 1974;Lakshmanan & Veech 1977;Rognstad 1980;Tomlinson et al 1988) and to convert hexoses into pentoses, particularly ribose 5-phosphate for its incorporation into nucleotides, especially important during cell growth (Srere et al 1955;Boss 1984;Pilz et al 1984).…”

Section: Introductionmentioning

confidence: 99%

Long-term nutritional effects on the primary liver and kidney metabolism in rainbow trout (Oncorhynchus mykiss). II. Adaptive response of glucose 6-phosphate dehydrogenase activity to high-carbohydrate/low-protein and high-fat/non-carbohydrate diets

Sánchez‐Muros¹,

Garcia-Rejon²,

Lupiáñez³

et al. 1996

Aquaculture Nutrition

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The influence of long‐term administration of high‐carbohydrate/low‐protein and high‐fat/non‐carbohydrate diets were studied in relation to kinetic behaviour of glucose 6‐phosphate dehydrogenase in liver and kidney of rainbow trout. In all cases studied, the saturation curves of these enzyme showed typical hyperbolic kinetics without evidence of sigmoidicity. After 30 days of feeding with a high‐fat diet (170 g kg−1), there was a significant decrease in Vmax and specific activity (45%) as well as catalytic efficiency (39%) without changes in Km or activity ratio of hepatic glucose 6‐phosphate dehydrogenase. These changes agree more with a clearly decreased cell concentration than with an inhibition of the pre‐existing enzyme. The administration of a high‐carbohydrate diet (60 g kg−1), contrary to what was previously thought, decreased Vmax by 21% and specific activity and catalytic efficiency by 30%, without significant changes in the other kinetic parameters of the hepatic enzyme. The kinetic behaviour under these nutritional conditons was due to the rejection of this diet by the fish and thus could be considered a low‐feeding situation. On the other hand, no variations in the kinetics of renal glucose 6‐phosphate dehydrogenase were found, clearly demonstrating that in this organ, the pentosephosphate pathway showed no adaptive response related to fattyacid and other lipid synthesis. The activity of the renal enzyme was consistently half that of the hepatic enzyme.

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Pathways of NADPH in rat liver. Evidence favoring a single cytosolic pool

Cited by 10 publications

References 16 publications

The content of pentose-cycle intermediates in liver in starved, fed ad libitum and meal-fed rats

The content of pentose-cycle intermediates in liver in starved, fed ad libitum and meal-fed rats

Dietary n‐3 long chain polyunsaturated fatty acids affect the serum biochemical parameters, lipid‐metabolism‐related of gene expression and intestinal health of juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatu )

Long-term nutritional effects on the primary liver and kidney metabolism in rainbow trout (Oncorhynchus mykiss). II. Adaptive response of glucose 6-phosphate dehydrogenase activity to high-carbohydrate/low-protein and high-fat/non-carbohydrate diets

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