Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
 2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acetyl coenzyme A carboxylase and fatty acid synthetase activities were studied to determine the biochemical basis of the markedly impaired capacity of fat cells from spontaneously obese, old rats to convert glucose to fatty acids relative to cells from lean, young rats. Michaelis constants for the substrates of both enzymes were similar in large and small adipocyte homogenates. In contrast, Vmax values were over 80% less in homogenates from large relative to small cells on a per cell basis. Long-term dialysis or the presence of albumin during the assays failed to restore the activities of these enzymes in homogenates of large fat cells. The combination of equal volumes of homogenates from the two cell types resulted in carboxylase and synthetase activities intermediate between activities found in the two homogenates alone. Therefore, the presence of endogenous allosteric inhibitors does not appear to account for the markedly blunted fatty acid synthesis enzyme activities in large fat cells. These results suggest that the fatty acid synthesis impairment, which is a primary defect in the insulin resistance of the large cells, is at least partly due to diminished cellular contents of acetyl coenzyme A carboxylase and fatty acid synthetase.
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PMID:Diminished activities of fatty acid synthesis enzymes in insulin-resistant adipocytes from spontaneously obese rats. 3 25

Rat epididymal fat-pads were incubated for 30min with glucose (2mg/ml) in the presence or absence of insulin. A twofold or greater increase in acetyl-CoA carboxylase activity was observed in extracts from insulin-treated tissue provided that assays were performed rapidly after extraction. This effect of insulin was evident whether or not extracts were prepared with albumin, and was not noticeably diminished by the presence of citrate or albumin or both in the assay. Incubation of extracts before assay led to activation of acetyl-CoA carboxylase and a marked diminution in the insulin effect. The enzyme in extracts was very sensitive to reversible inhibition by palmitoyl-CoA even in the presence of albumin (10mg/ml); inhibition persisted on dilution of enzyme and inhibitor. It is suggested that the observed activation of acetyl-CoA carboxylase by insulin may reflect changes in enzyme activity in the fat-cell resulting from the reduction of long-chain fatty-acyl-CoA that occurs in the presence of insulin. Activation of the enzyme with loss of the insulin effect on incubation of the extracts may be due to the slow dissociation of long-chain fatty acyl-CoA from the enzyme.
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PMID:Insulin and the regulation of adipose tissue acetyl-coenzyme A carboxylase. 414 98

1. Acetyl-CoA carboxylase activity was measured in extracts of rat epididymal fat-pads either on preparation of the extracts (initial activity) or after incubation of the extracts with citrate (total activity). In the presence of glucose or fructose, brief exposure of pads to insulin increased the initial activity of acetyl-CoA carboxylase; no increase occurred in the absence of substrate. Adrenaline in the presence of glucose and insulin decreased the initial activity. None of these treatments led to a substantial change in the total activity of acetyl-CoA carboxylase. A large decrease in the initial activity of acetyl-CoA carboxylase also occurred with fat-pads obtained from rats that had been starved for 36h although the total activity was little changed by this treatment. 2. Conditions of high-speed centrifugation were found which appear to permit the separation of the polymeric and protomeric forms of the enzyme in fat-pad extracts. After the exposure of the fat-pads to insulin (in the presence of glucose), the proportion of the enzyme in the polymeric form was increased, whereas exposure to adrenaline (in the presence of glucose and insulin) led to a decrease in enzyme activity. 3. These changes are consistent with a role of citrate (as activator) or fatty acyl-CoA thioesters (as inhibitors) in the regulation of the enzyme by insulin and adrenaline; no evidence that the effects of these hormones involve phosphorylation or dephosphorylation of the enzyme could be found. 4. Changes in the whole tissue concentration of citrate and fatty acyl-CoA thioesters were compared with changes in the initial activity of acetyl-CoA carboxylase under a variety of conditions of incubation. No correlation between the citrate concentration and the initial enzyme activity was evident under any condition studied. Except in fat-pads which were exposed to insulin there was little inverse correlation between the concentration in the tissue of fatty acyl-CoA thioesters and the initial activity of acetyl-CoA carboxylase. 5. It is suggested that changes in the concentration of free fatty acyl-CoA thioesters (which may not be reflected in whole tissue concentrations of these metabolites) may be important in the regulation of the activity of acetyl-CoA carboxylase. The possibility is discussed that the concentration of free fatty acyl-CoA thioesters may be controlled by binding to a specific protein with properties similar to albumin.
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PMID:Hormonal regulation of adipose-tissue acetyl-Coenzyme A carboxylase by changes in the polymeric state of the enzyme. The role of long-chain fatty acyl-Coenzyme A thioesters and citrate. 415 93

1. Methods are described for the extraction and assay of acetyl-CoA and of total acid-soluble and total acid-insoluble CoA derivatives in rat epididymal adipose tissue. 2. The concentration ranges of the CoA derivatives in fat pads incubated in vitro under various conditions were: total acid-soluble CoA, 0.20-0.59mm; total acid-insoluble CoA, 0.08-0.23mm; acetyl-CoA, 0.03-0.14mm. 3. An investigation was made of some postulated mechanisms of control of fatty acid and triglyceride synthesis in rat epididymal fat pads incubated in vitro. The concentrations of intermediates of possible regulatory significance were measured at various rates of fatty acid and triglyceride synthesis produced by the addition to the incubation medium (Krebs bicarbonate buffer containing glucose) of insulin, adrenaline, albumin, palmitate or acetate. 4. The whole-tissue concentrations of glucose 6-phosphate, l-glycerol 3-phosphate, citrate, acetyl-CoA, total acid-soluble CoA and total acid-insoluble CoA were assayed after 30 or 60min. incubation. The rates of fatty acid and triglyceride synthesis, calculated from the incorporation of [U-(14)C]glucose into fatty acids and glyceride glycerol respectively, and the rates of glucose uptake, lactate plus pyruvate output and glycerol output were measured over a 60min. incubation. 5. The rate of triglyceride synthesis could not be correlated with the concentrations of either l-glycerol 3-phosphate or long-chain fatty acyl-CoA (measured as total acid-insoluble CoA). Factor(s) other than the whole-tissue concentrations of these recognized precursors appear to be involved in the determination of the rate of triglyceride synthesis. 6. No relationship was found between the rate of fatty acid synthesis and the whole-tissue concentrations of the intermediates, citrate or acetyl-CoA, or with the two proposed effectors of acetyl-CoA carboxylase, citrate (as activator) or long-chain fatty acyl-CoA (as inhibitor). The control of fatty acid synthesis appears to reside in additional or alternative factors.
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PMID:The control of fatty acid and triglyceride synthesis in rat epididymal adipose tissue. Roles of coenzyme A derivatives, citrate and L-glycerol 3-phosphate. 574 24

Digitonin treatment of chick liver cells in monolayer culture results in plasma membrane perforations due to digitonin removal of membrane cholesterol. The amount and rate of acetyl-CoA carboxylase activity that escapes from the hepatocyte during digitonin treatment is positively related to the amount of protomeric carboxylase in the cells. Incubation of chick liver cells in culture with albumin-bound linoleate (60 min) caused a 3-fold increase in the amount of carboxylase activity released during exposure of cells to digitonin. Concomitant with the enhanced release of carboxylase activity was an 85% reduction in fatty acid synthesis induced by linoleate. Apparently, acute suppression of hepatocyte fatty acid synthesis by media free fatty acids resulted, in part, from a change in carboxylase conformation from the active polymeric state to the inactive protomeric form.
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PMID:Suppression of hepatocyte fatty acid synthesis by albumin-bound linoleate involves depolymerization of acetyl-CoA carboxylase filaments. 611 35

Hepatocytes isolated from 9-week-old chickens were cultured in a serum-free, hormonally defined medium. Relative amounts of mRNAs coding for lipogenic enzymes (acetyl-CoA carboxylase, fatty acid synthase, delta 9 desaturase, malic enzyme) and apoproteins (apoprotein A1 and apoprotein B) were determined until the 12th day. beta-actin and albumin mRNA, as well as albumin secretion, were also assessed. Cellular metabolic activity appeared to be very low for the first days of culture, but increased after the 7th day. All the mRNAs studied, except for that of malic enzyme, were present from this time throughout the culture lifespan. The biological significance of the observed results and the relevance of this chicken hepatocyte culture system for long-term metabolic and genetic studies are discussed.
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PMID:Lipogenic enzyme and apoprotein messenger RNAs in long-term primary culture of chicken hepatocytes. 810 Feb 36

The possible role played by albumin in regulating brain metabolism during development has been studied. The effects of fatty acid-free BSA on lactate, glucose, 3-hydroxybutyrate, and glutamine oxidation and lipogenesis by rat neurons and astrocytes from primary culture were studied. The rate of lactate oxidation and lipogenesis by neurons and astrocytes in the presence of BSA greatly exceeded that observed for glucose, 3-hydroxybutyrate, or glutamine, suggesting that lactate may be a key substrate for brain development. BSA strongly stimulated the rate of lactate, 3-hydroxybutyrate, and glutamine incorporation into lipids in both neurons (677%, 726%, and 250%, respectively) and astrocytes (415%, 393%, and 215%, respectively), possibly by binding long-chain acyl-CoA excesses, potent inhibitors of acetyl-CoA carboxylase. However, BSA decreased the rate of lipogenesis from glucose in both neurons (34%) and astrocytes (55%), probably by inhibiting glycerol-borne phospholipid synthesis. BSA significantly increased the rates of lactate (61%) and glucose (32%) oxidation by astrocytes but not those of 3-hydroxybutyrate and glutamine, suggesting that BSA may stimulate pyruvate oxidation. However, in neurons BSA did not affect the rate of oxidation of any of the substrates tested, which suggests that pyruvate oxidation is regulated differently in neurons and astrocytes. The results suggest that lactate is the most important substrate for both neurons and astrocytes, stressing the role played by lactate in brain development. Our results also suggest that serum albumin may control brain development by fostering metabolism for growth and differentiation purposes.
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PMID:Regulation of lactate metabolism by albumin in rat neurons and astrocytes from primary culture. 810 80

Triamcinolone or triiodothyronine (T3) was administered to rats with nephrosis induced by aminonucleoside of puromycin and to control nontreated rats. Triamcinolone produced hyperglycemia, hyperinsulinemia and liver glycogen deposition in control rats and to a lesser extent in nephrotic rats. Triamcinolone treatment did not affect plasma protein and albumin levels but increased the level of plasma triglycerides and cholesterol in the very low density lipoprotein (VLDL) and LDL but not high density lipoprotein fractions. The exacerbation of hyperlipoproteinemia was attributed both to increase hepatic lipid synthesis and delayed removal, since it was associated with the induction of hepatic acetyl-CoA carboxylase, the regulatory enzyme of lipogenesis, as well as with marked suppression of adipose tissue lipoprotein lipase (LPL). The hepatic lipase activity was found to be elevated in nephrotic rats but was suppressed by triamcinolone treatment, indicating a reduced capacity of VLDL to LDL conversion. T3 treatment resulted in serum glucose and insulin increases similar to triamcinolone, but more moderate in nephrotic vs. control rats, and in marked reduction in liver glycogen content. Plasma protein levels were not affected, but contrary to control rats, T3 treatment produced an elevation in serum triglycerides and cholesterol in nephrotic rats. The activity of several hepatic lipogenic enzymes, including acetyl-CoA carboxylase, was markedly elevated, as was the activity of gluconeogenic enzymes. Thus, the hyperlipoproteinemia on T3 treatment appeared to be mainly due to predomination of lipid synthesis over removal, since the activities of enzymes responsible for plasma lipid disposal, adipose tissue LPL and hepatic lipase were enhanced both in control and nephrotic rats. It is remarkable that both T3 and triamcinolone induce the lipogenic enzymes and apolipoproteins in the liver of nephrotic rats, already pronouncedly stimulated to replace the excreted plasma proteins. Thus, the nephrotic liver is able to respond to hormonal stimulation with further specific protein and lipid synthesis. It is also pertinent that the recovery from immunosuppressive treatment of human nephrosis, developing on an immune background, may result in more impressive amelioration of proteinuria and hypoproteinemia than of hyperlipoproteinemia because of the lipidemic effect of glucocorticoids.
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PMID:Hyperlipoproteinemia of aminonucleoside-induced nephrotic syndrome--modulation by glucocorticoids and triiodothyronine. 868 44

Ranolazine is an novel investigational antianginal agent that stimulates glucose oxidation in isolated rat hearts. This study determined its effects on metabolic substrate and O2 utilization in an in vitro skeletal muscle preparation, the rat epitrochlearis muscle. Muscles were superfused with Krebs-Henseleit buffer containing 3% albumin, 0.4 mM palmitate, 5.5 mM glucose, 0.5 mM lactate, and a physiological amino acid mixture. Perfusate also contained either 1) [U-14C]glucose for measurement of glucose oxidation or 2) [9,10-3H]palmitate and [U-14C]lactate for measurement of palmitate and lactate oxidation. Addition of ranolazine (10 microM) significantly stimulated glucose oxidation and decreased palmitate oxidation but had no effect on lactate oxidation. Overall, the calculated relative contribution of glucose oxidation to aerobic ATP production increased from 12 to 33%, whereas from palmitate it decreased from 55 to 26%. Ranolazine did not alter tissue malonyl-CoA contents, making it unlikely that the decrease in palmitate oxidation caused by ranolazine is due to a decrease in the activity of acetyl-CoA carboxylase. These data demonstrate that ranolazine can shift energy substrate preference in skeletal muscle, which could potentially prove useful in ischemic disorders of skeletal muscle.
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PMID:Effects of ranolazine on oxidative substrate preference in epitrochlearis muscle. 887 62

Avian lipogenesis was studied in the chicken hepatocarcinoma LMH cell line. The differentiated and lipogenic status of these cells was evidenced by the presence of the albumin mRNA as well as of some mRNA coding for enzymes involved in lipogenesis (acetyl-CoA carboxylase, fatty acid synthase, delta 9 desaturase) and for apoproteins (apoprotein B and A1). These results were further confirmed by the analysis of triglyceride synthesis and secretion rates in growing cells. A time course analysis showed that triglyceride metabolism was affected by cell density. Hormone responsiveness of triglyceride production was also analyzed. Insulin, triiodothyronine and glucagon to a lesser extent were shown to regulate lipogenesis of LMH cells. The results were compared with those obtained in primary cultures of chicken hepatocytes.
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PMID:Triglyceride synthesis and secretion and lipogenesis implicated gene expression in the chicken hepatocarcinoma cell line LMH. 940 72


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