scholarly journals Association between Hydrogen Peroxide-Dependent Byproducts of Ascorbic Acid and Increased Hepatic Acetyl-CoA Carboxylase Activity

2005 ◽  
Vol 51 (8) ◽  
pp. 1462-1471 ◽  
Author(s):  
Laurent Knafo ◽  
Philippe Chessex ◽  
Thérèse Rouleau ◽  
Jean-Claude Lavoie
Keyword(s):  
Ascorbic Acid ◽  
Lipid Metabolism ◽  
Guinea Pig ◽  
Dehydroascorbic Acid ◽  
Biologically Active ◽  
Urinary Concentration ◽  
Acetyl Coa Carboxylase ◽  
High Concentration ◽  
Acetyl Coa ◽  
Carboxylase Activity

Abstract Background: Parenteral multivitamin preparation (MVP) induces fatty liver in neonatal guinea pig pups; this is prevented by photoprotection. Photo-excited riboflavin present in MVP generates H2O2 and molecules with masses of 136 and 208. We hypothesized that H2O2 initiates the peroxidation of ascorbic acid (AA), producing biologically active byproducts affecting hepatic lipid metabolism. Methods: Mass spectrometry (MS) documented the participation of H2O2 and photo-excited riboflavin (Ribo) in the formation of AA byproducts. Sixteen 3-day-old guinea pig pups received an intravenous solution (50 g/L dextrose + 4.5 g/L NaCl + 1 kIU/L heparin) at 240 mL · kg−1 · day−1, enriched with control or test mixtures, for 4 days. The control mixture was photo-protected AA + Ribo (without byproducts or H2O2), and the test mixture was AA + Ribo treated to generate AA byproducts without H2O2. Hepatic acetyl-CoA carboxylase (ACC) activity was determined after 4 days. Fourth-day urine samples were analyzed by MS. Data were treated by ANOVA (α = 0.05). Results: H2O2 did not influence the classic degradation of AA, as the generation of 2,3-diketogulonic acid was not affected. In contrast, the formation of molecules with masses of 136 and 208 was H2O2 and time dependent. ACC activity was higher (P <0.01) in animals receiving high concentration of these molecules; its hepatic activation correlated (P <0.01) with the urinary concentration of molecule-208. Conclusions: H2O2 at concentrations found in the clinical setting of total parenteral nutrition induce the transformation of dehydroascorbic acid into compounds that have the potential to affect lipid metabolism. These molecules have peroxide and aldehyde functions.

Effects of the Herbicide Sethoxydim and the Safener Dichlormid on Lipid Synthesis and Acetyl-CoA Carboxylase Activity of Grain Sorghum

1991 ◽  
Vol 46 (11-12) ◽  
pp. 934-938
Author(s):  
Kriton K. Hatzios
Keyword(s):  
Combined Treatment ◽  
Lipid Synthesis ◽  
Grain Sorghum ◽  
Combined Effects ◽  
Acetyl Coa Carboxylase ◽  
Total Lipids ◽  
High Concentration ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Leaf Protoplasts

The effects of individual or combined treatment of the cyclohexanedione herbicide sethoxydim and the safener dichlormid on total lipid synthesis, protein synthesis and acetyl-CoA carboxylase (ACCase, EC 6.4.1.12) activity of grain sorghum [Sorghum bicolor (L.) M oench, var. G623] were investigated. Sethoxydim and dichlormid were tested at concentrations of 0, 5, 50, and 100 μM each. Sethoxydim applied alone at 50 and 100 μm , inhibited the incorporation of [14C]acetate into total lipids of sorghum leaf protoplasts by more than 50%, following a 4 h incubation. Dichlormid antagonized partially the inhibitory effects of sethoxydim on the incorporation of acetate into total lipids of sorghum protoplasts only when it was used at 100 μM . Sethoxydim applied alone inhibited the incorporation of [14C]leucine into sorghum leaf protoplasts only at 100 μm. Dichlormid was not inhibitory of this process at any concentration. The combined effects of sethoxydim and dichlormid on this process were mainly additive indicating no interactions of the two chemicals. Sethoxydim applied alone at 5 and 50 μM inhibited the activity of ACCase extracted from leaf tissues of grain sorghum seedlings by 58 and 90%, respectively. Addition of the safener dichlormid to the assay medium did not inhibit ACCase activity of sorghum leaves even at the high concentration of 50 μM . The combined effects of sethoxydim and dichlormid on the activity of sorghum ACCase were similar to those observed when sethoxydim was used alone. These results indicate that the protection conferred by dichlormid on grain sorghum against sethoxydim injury can not be explained on the basis of an antagonistic interaction of the two chemicals on target metabolic processes (lipid synthesis) or target enzymes (ACCase).

scholarly journals Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats

1991 ◽  
Vol 274 (3) ◽  
pp. 739-744 ◽  
Author(s):  
A Zhou ◽  
J H Nielsen ◽  
O Farver ◽  
N A Thorn
Keyword(s):  
Ascorbic Acid ◽  
Pancreatic Islet ◽  
Islet Cells ◽  
Secretory Granules ◽  
Dehydroascorbic Acid ◽  
Pancreatic Tissue ◽  
Biologically Active ◽  
Pancreatic Islet Cells ◽  
High Concentration ◽  
Old Rats

Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.

scholarly journals Critical phosphorylation sites for acetyl-CoA carboxylase activity.

1994 ◽  
Vol 269 (35) ◽  
pp. 22162-22168 ◽  
Author(s):  
J. Ha ◽  
S. Daniel ◽  
S.S. Broyles ◽  
K.H. Kim
Keyword(s):  
Phosphorylation Sites ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity

Relative Activities of Acetyl-CoA Carboxylase and Fatty Acid Synthetase in Chick Liver: Effects of Dietary Fat

1973 ◽  
Vol 51 (7) ◽  
pp. 1029-1033 ◽  
Author(s):  
Gregory I. Liou ◽  
W. E. Donaldson
Keyword(s):  
Fatty Acid ◽  
Corn Oil ◽  
Fatty Acid Synthetase ◽  
Basal Diet ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Cytosol Fraction ◽  
Activity Concentrations

The specific activities of acetyl-CoA carboxylase and fatty acid synthetase were measured in the cytosol fraction of livers from chicks fed various levels of corn oil, cottonseed oil, corn-oil free fatty acids, or crude (79%) oleic acid. Activities of both enzymes were depressed by the addition of fat to a fat-free basal diet. The ratios of synthetase to carboxylase activity were greater than unity when up to 4% fat was fed, but less than unity when 8% or higher levels of fat were fed. The depressions of the activities of these enzymes appeared to be unrelated to the dietary level of linoleate. In in vitro experiments, 2 μM concentrations of palmityl-CoA or oleoyl-CoA depressed acetyl-CoA carboxylase activity. Concentrations of 20 μM of these acyl-CoA esters did not affect the activity of fatty acid synthetase.

scholarly journals Growth-hormone-prolactin interactions in the regulation of mammary and adipose-tissue acetyl-CoA carboxylase activity and gene expression in lactating rats

1992 ◽  
Vol 285 (2) ◽  
pp. 469-475 ◽  
Author(s):  
M C Barber ◽  
M T Travers ◽  
E Finley ◽  
D J Flint ◽  
R G Vernon
Keyword(s):  
Adipose Tissue ◽  
Mammary Gland ◽  
Serum Prolactin ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Total Enzyme Activity ◽  
Mrna Concentration ◽  
Total Enzyme ◽  
Activation Status

The factors and mechanisms responsible for the reciprocal changes in lipogenesis in rat mammary gland and adipose tissue during the lactation cycle have been investigated. Lactation decreased the activation status and mRNA concentration of acetyl-CoA carboxylase in adipose tissue. Litter removal decreased the mRNA concentration of acetyl-CoA carboxylase in the mammary gland and increased the enzyme's mRNA concentration and activation status in adipose tissue. Lowering serum prolactin concentration in lactating rats decreased the amount of mammary acetyl-CoA carboxylase mRNA and increased that of adipose tissue, and increased the activation status of the enzyme in adipose tissue. Decreasing serum growth hormone (GH) alone had little effect on acetyl-CoA carboxylase in lactating rats, although it did lower pup growth rate and serum concentration of insulin-like growth factor-I. Lowering serum GH concentration exacerbated the effects of decreasing serum prolactin on mammary-gland (but not adipose-tissue) acetyl-CoA carboxylase mRNA and further increased the rise in activation status of the adipose-tissue enzyme induced by decreasing serum prolactin. Changes in acetyl-CoA carboxylase mRNA in both mammary and adipose tissue were paralleled by changes in total enzyme activity except after litter removal, when there was a disproportionately large decrease in total enzyme activity of the mammary gland. Thus prolactin has a major and GH a minor role in the regulation of acetyl-CoA carboxylase activity during lactation. Changes in mammary activity in response to prolactin and GH are primarily due to alterations in gene transcription, whereas adaptation in adipose tissue involves both changes in gene transcription and activation status.

scholarly journals Vitamin C and the Role of Citrus Juices as Functional Food

2009 ◽  
Vol 4 (5) ◽  
pp. 1934578X0900400 ◽  
Author(s):  
Nuria Martí ◽  
Pedro Mena ◽  
Jose Antonio Cánovas ◽  
Vicente Micol ◽  
Domingo Saura
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Dehydroascorbic Acid ◽  
Antioxidant Response ◽  
Intestinal Wall ◽  
Processing Temperature ◽  
High Concentration ◽  
Citrus Juices ◽  
Citrus Extract

The literature on the content and stability of vitamin C (ascorbic acid, AA) in citrus juices in relation to industrial practices is reviewed. The role of vitamin C from citrus juices in human diet is also reviewed. Citrus fruits and juices are rich in several types of bioactive compounds. Their antioxidant activity and related benefits derive not only from vitamin C but also from other phytochemicals, mainly flavonoids. During juice processing, temperature and oxygen are the main factors responsible for vitamin C losses. Nonthermal processed juices retain higher levels of vitamin C, but economic factors apparently delay the use of such methods in the citrus industry. Regarding packing material, vitamin C in fruit juice is quite stable when stored in metal or glass containers, whereas juice stored in plastic bottles has a much shorter shelf-life. The limiting step for vitamin C absorption in humans is transcellular active transport across the intestinal wall where AA may be oxidized to dehydroascorbic acid (DHAA), which is easily transported across the cell membrane and immediately reduced back to AA by two major pathways. AA bioavailability in the presence of flavonoids has yielded controversial results. Whereas flavonoids seem to inhibit intestinal absorption of AA, some studies have shown that AA in citrus extract was more available than synthetic ascorbic acid alone. DHAA is reported to possess equivalent biological activity to AA, so recent studies often consider the vitamin C activity in the diet as the sum of AA plus DHAA. However, this claimed equivalence should be carefully reexamined. Humans are one of the few species lacking the enzyme (L-gulonolactone oxidase, GLO) to convert glucose to vitamin C. It has been suggested that this is due to a mutation that provided a survival advantage to early primates, since GLO produces toxic H2O2. Furthermore, the high concentration of AA (and DHAA) in neural tissues could have been the key factor that caused primates (vertebrates with relative big brain) to lose the capacity to synthesize vitamin C. Oxidative damage has many pathological implications in human health, and AA may play a central role in maintaining the metabolic antioxidant response. The abundance of citrus juices in the Mediterranean diet may provide the main dietary source for natural vitamin C.

scholarly journals Both insulin and epidermal growth factor stimulate lipogenesis and acetyl-CoA carboxylase activity in isolated adipocytes. Importance of homogenization procedure in avoiding artefacts in acetyl-CoA carboxylase assay

1986 ◽  
Vol 234 (2) ◽  
pp. 279-284 ◽  
Author(s):  
T A Haystead ◽  
D G Hardie
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Maximal Effect ◽  
Acetyl Coa Carboxylase ◽  
Homogenization Procedure ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Epidermal Growth ◽  
Isolated Adipocytes ◽  
Significant Interference

Epidermal growth factor (EGF) stimulates lipogenesis by 3-4-fold in isolated adipocytes, with a half-maximal effect at 10 nM-EGF. In the same batches of cells insulin stimulated lipogenesis by 15-fold. Freezing and prolonged homogenization of adipocytes results in release of large quantities of pyruvate carboxylase from broken mitochondria, and sufficient pyruvate can be carried through into assays for this enzyme to cause significant interference with assays of acetyl-CoA carboxylase in crude adipocyte extracts. This may account for the high amount of citrate-independent acetyl-CoA carboxylase activity reported to be present in adipocyte extracts in some previous publications. This problem may be eliminated by homogenizing very briefly without freezing. By using the modified homogenization procedure, EGF treatment of adipocytes was shown to produce an effect on acetyl-CoA carboxylase activity almost identical with that of insulin. Both messengers increase Vmax. without significant effect on the Ka for the allosteric activator, citrate.

scholarly journals Insulin activation of lipogenesis in isolated mammary acini from lactating rats fed on a high-fat diet. Evidence that acetyl-CoA carboxylase is a site of action

1987 ◽  
Vol 242 (3) ◽  
pp. 905-911 ◽  
Author(s):  
M R Munday ◽  
D H Williamson
Keyword(s):  
Glucose Uptake ◽  
High Fat Diet ◽  
Acetyl Coa Carboxylase ◽  
High Fat ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Glucose Incorporation ◽  
Site Of Action ◽  
A Site

Feeding lactating rats on high-fat cheese crackers in addition to laboratory chow increased the dietary intake of fat from 2 to 20% of the total weight of food eaten and decreased mammary-gland lipogenesis in vivo by approx. 50%. This lipogenic inhibition was also observed in isolated mammary acini, where it was accompanied by decreased glucose uptake. These inhibitions were completely reversed by incubation with insulin. Insulin had no effect on the rate of glucose transport into acini, nor on pyruvate dehydrogenase activity as estimated by the accumulation of pyruvate and lactate, suggesting that these are not the sites of lipogenic inhibition. Insulin stimulated the incorporation of [1-14C]acetate into lipid in acini from high-fat-fed rats. In the presence of alpha-cyanohydroxycinnamate, a potent inhibitor of mitochondrial pyruvate transport, and with glucose as the sole substrate, neither [1-14C]glucose incorporation into lipid nor glucose uptake were stimulated by insulin. Insulin did stimulate the incorporation of [1-14C]acetate into lipid in the presence of alpha-cyanohydroxycinnamate, and this was accompanied by an increase in glucose uptake by the acini. This indicated that increased glucose uptake was secondary to the stimulation of lipogenesis by insulin, which therefore must occur via activation of a step in the pathway distal to mitochondrial pyruvate transport. Insulin stimulated acetyl-CoA carboxylase activity measured in crude extracts of acini from high-fat-fed rats, restoring it to values close to those of chow-fed controls. The effects of insulin on acetyl-CoA carboxylase activity and lipogenesis were not antagonized by adrenaline or dibutyryl cyclic AMP.

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