Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Previous studies have shown that the rate of fatty acid synthesis is elevated by more than 20-fold in livers of transgenic mice that express truncated nuclear forms of sterol regulatory element-binding proteins (SREBPs). This was explained in part by an increase in the levels of mRNA for the two major enzymes of fatty acid synthesis, acetyl-CoA carboxylase and fatty acid synthase, whose transcription is stimulated by SREBPs. Fatty acid synthesis also requires a source of acetyl-CoA and NADPH. In the current studies we show that the levels of mRNA for ATP citrate lyase, the enzyme that produces acetyl-CoA, are also elevated in the transgenic livers. In addition, we found marked elevations in the mRNAs for malic enzyme, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase, all of which produce NADPH. Finally, we found that overexpressing two of the SREBPs (1a and 2) led to elevated mRNAs for stearoyl-CoA desaturase 1 (SCD1), an isoform that is detectable in nontransgenic livers, and SCD2, an isoform that is not detected in nontransgenic livers. This stimulation led to an increase in total SCD activity in liver microsomes. Together, all of these changes would be expected to lead to a marked increase in the concentration of monounsaturated fatty acids in the transgenic livers, and this was confirmed chromatographically. We conclude that expression of nuclear SREBPs is capable of activating the entire coordinated program of unsaturated fatty acid biosynthesis in mouse liver.
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PMID:Nuclear sterol regulatory element-binding proteins activate genes responsible for the entire program of unsaturated fatty acid biosynthesis in transgenic mouse liver. 985 71

The transcription of genes encoding proteins involved in the hepatic synthesis of lipids from glucose is strongly stimulated by carbohydrate feeding. It is now well established that in the liver, glucose is the main activator of the expression of this group of genes, with insulin having only a permissive role. While ADD1/SREBP-1 has been implicated in lipogenic gene expression through temporal association with food intake and ectopic gain-of-function experiments, no genetic evidence for a requirement for this factor in glucose-mediated gene expression has been established. We show here that the transcription of ADD1/SREBP-1c in primary cultures of hepatocytes is controlled positively by insulin and negatively by glucagon and cyclic AMP, establishing a link between this transcription factor and carbohydrate availability. Using adenovirus-mediated transfection of a powerful dominant negative form of ADD1/SREBP-1c in rat hepatocytes, we demonstrate that this factor is absolutely necessary for the stimulation by glucose of L-pyruvate kinase, fatty acid synthase, S14, and acetyl coenzyme A carboxylase gene expression. These results demonstrate that ADD1/SREBP-1c plays a crucial role in mediating the expression of lipogenic genes induced by glucose and insulin.
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PMID:ADD1/SREBP-1c is required in the activation of hepatic lipogenic gene expression by glucose. 1020 99

The mRNAs encoding mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mtHMG-CoA synthase), the rate limiting enzyme in ketone body production, are highly expressed in subcutaneous (SC) and, to a lesser extent, in peri-epididymal (PE) rat adipose tissues. This atypical mtHMG-CoA synthase gene expression is dependent on the age (from 9 weeks of age) and sex (higher in male than in female) of the rats. In contrast, the expression of mtHMG-CoA synthase in SC adipose deposit is independent of the nutritional state (fed versus starved) or of the thermic environment (24 degrees C versus 4 degrees C). The expression of mtHMG-CoA synthase is suppressed in SC fat pads of castrated male rats whereas treatment of castrated rats with testosterone restores a normal level of expression. Moreover, testosterone injection induces the expression mtHMG-CoA synthase in SC adipose tissue of age-matched females. The presence of the mtHMG-CoA synthase immunoreactive protein confers to mitochondria isolated from SC adipose deposits, the capacity to produce ketone bodies at a rate similar to that found in liver mitochondria (SC = 13.7 +/- 0.7, liver = 16.4 +/- 1.4 nmol/min/mg prot). mtHMG-CoA synthase is expressed in the stromal vascular fraction (SVF) whatever the adipose deposit considered. While acetyl-CoA carboxylase (ACC) is only expressed in mature adipocytes, the other lipogenic enzymes, fatty acid synthase (FAS) and citrate cleavage enzyme (CCE), are expressed both in SVF cells and mature adipocytes. The expression of lipogenic enzyme genes is markedly reduced in adipocytes but not in SVF cells isolated from 48-h starved male rats. When SVF is subfractionated, mtHMG-CoA synthase mRNAs are mainly recovered in two fractions containing poorly digested structures such as microcapillaries whereas the lowest expression is found in the pre-adipocyte fraction. Interestingly, FAS and CCE mRNAs co-segregate with mtHMG-CoA synthase mRNA. The possible physiological relevance of such atypical expression of mtHMG-CoA synthase is discussed.
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PMID:Atypical expression of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase in subcutaneous adipose tissue of male rats. 1035 39

Polyunsaturated fatty acids (PUFA) coordinately suppress the transcription of a wide array of hepatic lipogenic genes including fatty acid synthase (FAS) and acetyl-CoA carboxylase. Interestingly, the over-expression of sterol regulatory element binding protein-1 (SREBP-1) induces the expression of all of the enzymes suppressed by PUFA. This observation led us to hypothesize that PUFA coordinately inhibit lipogenic gene transcription by suppressing the expression of SREBP-1. Our initial studies revealed that the SREBP-1 and FAS mRNA contents of HepG2 cells were reduced by 20:4(n-6) in a dose-dependent manner (i.e. EC(50) approximately 10 microM), whereas 18:1(n-9) had no effect. Similarly, supplementing a fat-free, high glucose diet with oils rich in (n-6) or (n-3) PUFA reduced the hepatic content of precursor and nuclear SREBP-1 60 and 85%, respectively; however, PUFA had no effect on the nuclear content of upstream stimulatory factor (USF)-1. The PUFA-dependent decrease in nuclear content of mature SREBP-1 was paralleled by a 70-90% suppression in FAS gene transcription. In contrast, dietary 18:1(n-9), i.e. triolein, had no inhibitory influence on the expression of SREBP-1 or FAS. The decrease in hepatic expression of SREBP-1 and FAS associated with PUFA ingestion was mimicked by supplementing the fat-free diet with the PPARalpha-activator, WY 14, 643. Interestingly, nuclear run-on assays revealed that changes in SREBP-1 mRNA abundance were not accompanied by changes in SREBP-1 gene transcription. These results support the concept that PUFA coordinately inhibit lipogenic gene transcription by suppressing the expression of SREBP-1 and that the PUFA regulation of SREBP-1 appears to occur at the post-transcriptional level.
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PMID:Sterol regulatory element binding protein-1 expression is suppressed by dietary polyunsaturated fatty acids. A mechanism for the coordinate suppression of lipogenic genes by polyunsaturated fats. 1043 39

The hypothesis is advanced that NADP(+)-malic enzyme (ME; EC 1.1.1.40) is an important activity in regulating the extent of lipid accumulation in filamentous fungi. In Mucor circinelloides, a fungus capable of accumulating only 25% (w/w, dry wt) lipid, even under the most propitious conditions, ME disappears 15-20 h after nitrogen exhaustion, coincident with the cessation of lipid accumulation. In contrast, ME in Mortierella alpina, a fungus capable of accumulating 50% (w/w, dry wt) lipid, remains active for over 60 h after N-exhaustion during which time lipid accumulation continues. No other enzyme activity studied, including the lipogenic enzymes acetyl-CoA carboxylase, fatty acid synthase, diacyglycerol acyltransferase, ATP: citrate lyase and the NADPH-generating enzymes glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP+:isocitrate dehydrogenase, demonstrated any correlation with the accumulation of storage lipid in either fungus. Full activity of ME is restored in Mr. circinelloides within 4 h by adding NH4+ to the cultures, but this is prevented by adding cycloheximide as an inhibitor of protein synthesis. This suggests that the decrease in ME activity occurs due to down-regulation of the ME gene.
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PMID:The role of malic enzyme in the regulation of lipid accumulation in filamentous fungi. 1046 57

Dietary fish oil induces hepatic peroxisomal and microsomal fatty acid oxidation by peroxisome proliferator-activator receptor alpha activation, whereas it down-regulates lipogenic gene expression by unknown mechanism(s). Because sterol regulatory element-binding proteins (SREBPs) up-regulated lipogenic genes, investigation was made on the effects of fish oil feeding on SREBPs and sterol regulatory element (SRE)-dependent gene expression in C57BL/6J mice. Three forms of SREBPs, SREBP-1a, -1c, and -2, are expressed in liver, and their truncated mature forms activate transcription of sterol-regulated genes. C57BL/6J mice were divided into three groups; the first group was given a high carbohydrate diet, and the other two groups were given a high fat diet (60% of total energy), with the fat in the form of safflower oil or fish oil, for 5 months. Compared with safflower oil feeding, fish oil feeding decreased triglyceride and cholesterol concentrations in liver. There were no differences in amount of SREBP-1 and -2 in both precursor and mature forms between carbohydrate- and safflower oil-fed mice. However, compared with safflower oil feeding, fish oil feeding reduced the amounts of precursor SREBP-1 in membrane fraction by 90% and of mature SREBP-1 in liver nuclei by 57%. Fish oil feeding also reduced precursor SREBP-2 by 65% but did not alter the amount of mature SREBP-2. Compared with safflower oil feeding, fish oil feeding decreased liver SREBP-1c mRNA level by 86% but did not alter SERBP-1a mRNA. Consistent with decrease of mature SREBP-1, compared with safflower oil feeding, fish oil feeding down-regulated the expression of liver SRE-dependent genes, such as low density lipoprotein receptor, 3-hydroxy-3-methylglutaryl-CoA reductase, 3-hydroxy-3-methylglutaryl-CoA synthase, fatty acid synthase, acetyl-CoA carboxylase, and stearoyl-CoA desaturase-1. These data suggested that in liver, fish oil feeding down-regulates the mature form of SREBP-1 by decreasing SREBP-1c mRNA expression, with corresponding decreases of mRNAs of cholesterologenic and lipogenic enzymes.
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PMID:Fish oil feeding decreases mature sterol regulatory element-binding protein 1 (SREBP-1) by down-regulation of SREBP-1c mRNA in mouse liver. A possible mechanism for down-regulation of lipogenic enzyme mRNAs. 1046 32

We introduced methyl or ethyl groups to the 2- or 3-position of the eicosapentaenoic acid (EPA) molecule to investigate whether the branching of EPA could influence its hypolipidemic effect in rats. The most effective branching involved two methyl groups in the 2-position and one methyl group in the 3-position. These EPA derivatives increased hepatic mitochondrial and peroxisomal beta-oxidation and decreased plasma lipids concomitant with suppressed acetyl-coenzyme A (CoA) carboxylase (EC 6.4.1.2) and fatty acid synthase (EC 2.3.1.85) activities. This was followed by elevated activities of camitine O-palmitoyltransferase (EC 2.3.1.21) and possibly 2,4-dienoyl-CoA reductase (EC 1.3.1.34), as well as induced mRNA levels of these enzymes and fatty acyl-CoA oxidase. The fatty acid composition in liver changed, with an increased 18:1 n-9 content, whereas the expression of delta9-desaturase remained unchanged. We investigated the flux of fatty acids in cultured hepatocytes, and found that oxidation of [1-14C]-labeled palmitic acid increased but the secretion of palmitic acid-labeled triglycerides decreased after addition of 2-methyl-EPA. The fatty acyl-CoA oxidase (EC 1.3.3.6) activity in these cells remained unchanged. A significant negative correlation was obtained between palmitic acid oxidation and palmitic acid-labeled synthesized triglycerides. To investigate whether the hypolipidemic effect occurred independently of induced peroxisomal beta-oxidation, we fed rats 2-methyl-tetradecylthioacetic acid. This compound increased the peroxisomal but not the mitochondrial beta-oxidation, and the plasma lipid levels were unchanged. In conclusion, EPA methylated in the 2- or 3-position renders it more potent as a hypolipidemic agent. Furthermore, this study supports the hypothesis that the mitochondrion is the primary site for the hypolipidemic effect.
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PMID:Methylated eicosapentaenoic acid and tetradecylthioacetic acid: effects on fatty acid metabolism. 1048 71

To elucidate the physiological role of sterol regulatory element-binding protein-1 (SREBP-1), the hepatic mRNA levels of genes encoding various lipogenic enzymes were estimated in SREBP-1 gene knockout mice after a fasting-refeeding treatment, which is an established dietary manipulation for the induction of lipogenic enzymes. In the fasted state, the mRNA levels of all lipogenic enzymes were consistently low in both wild-type and SREBP-1(-/-) mice. However, the absence of SREBP-1 severely impaired the marked induction of hepatic mRNAs of fatty acid synthetic genes, such as acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase, that was observed upon refeeding in the wild-type mice. Furthermore, the refeeding responses of other lipogenic enzymes, glycerol-3-phosphate acyltransferase, ATP citrate lyase, malic enzyme, glucose-6-phosphate dehydrogenase, and S14 mRNAs, were completely abolished in SREBP-1(-/-) mice. In contrast, mRNA levels for cholesterol biosynthetic genes were elevated in the refed SREBP-1(-/-) livers accompanied by an increase in nuclear SREBP-2 protein. When fed a high carbohydrate diet for 14 days, the mRNA levels for these lipogenic enzymes were also strikingly lower in SREBP-1(-/-) mice than those in wild-type mice. These data demonstrate that SREBP-1 plays a crucial role in the induction of lipogenesis but not cholesterol biosynthesis in liver when excess energy by carbohydrates is consumed.
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PMID:Sterol regulatory element-binding protein-1 as a key transcription factor for nutritional induction of lipogenic enzyme genes. 1058 67

Dietary polyunsaturated fatty acids (PUFA) are negative regulators of hepatic lipogenesis that exert their effects primarily at the level of transcription. Sterol regulatory element-binding proteins (SREBPs) are transcription factors responsible for the regulation of cholesterol, fatty acid, and triglyceride synthesis. In particular, SREBP-1 is known to play a crucial role in the regulation of lipogenic gene expression in the liver. To explore the possible involvement of SREBP-1 in the suppression of hepatic lipogenesis by PUFA, we challenged wild-type mice and transgenic mice overexpressing a mature form of SREBP-1 in the liver with dietary PUFA. In the liver of wild-type mice, dietary PUFA drastically decreased the mature, cleaved form of SREBP-1 protein in the nucleus, whereas the precursor, uncleaved form in the membranes was not suppressed. The decreases in mature SREBP-1 paralleled those in mRNAs for lipogenic enzymes such as fatty acid synthase and acetyl-CoA carboxylase. In the transgenic mice, dietary PUFA did not reduce the amount of transgenic SREBP-1 protein, excluding the possibility that PUFA accelerated the degradation of mature SREBP-1. The resulting sustained expression of mature SREBP-1 almost completely canceled the suppression of lipogenic gene expression by PUFA in the SREBP-1 transgenic mice. These results demonstrate that the suppressive effect of PUFA on lipogenic enzyme genes in the liver is caused by a decrease in the mature form of SREBP-1 protein, which is presumably due to the reduced cleavage of SREBP-1 precursor protein.
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PMID:A crucial role of sterol regulatory element-binding protein-1 in the regulation of lipogenic gene expression by polyunsaturated fatty acids. 1058 68

When two copies of the sequences spanning -57 to -35 of the fatty acid synthase (FAS) or -64 to -41 of the ATP citrate-lyase (ACL) gene linked to a reporter gene were transfected into primary cultured hepatocytes, the reporter activities significantly increased in response to insulin/glucose treatment. In cotransfection experiments of the FAS(-57/-35) with the Sp1 or Sp3 expression vector, the reporter activities of transcription were suppressed by Sp1 and stimulated by Sp3. In the cotransfection experiments of ACL(-64/-41), the activities were suppressed by Sp1 but were unchanged by Sp3. A similar effect of Sp1 and Sp3 on transcription was seen in mRNA concentrations and enzyme activities of endogenous FAS and ACL. Moreover, the mRNA concentrations and enzyme activities of endogenous acetyl-CoA carboxylase were suppressed by Sp1 and greatly increased by Sp3. Gel mobility super shift assays using antibodies against Sp1 or Sp3 revealed the binding of the transcription factors Sp1 and Sp3 with the GC rich regions located within FAS(-57/-35) and ACL(-64/-41) genes. The formation of DNA-protein complexes was decreased in rats fed a high-carbohydrate diet in comparison with that in fasted rats, but feeding the corn oil diet inhibited this decrease. In Western immunoblotting assay, however, the amount of Sp1 and Sp3 remained unchanged in the dietary conditions. Therefore, the binding of DNA-protein complexes was not due to changes in the amount of Sp1 and Sp3 but to changes in the binding activity, suggesting that these transcription factors may be an important determinant of lipogenic enzyme expression.
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PMID:Transcriptional regulation of fatty acid synthase gene and ATP citrate-lyase gene by Sp1 and Sp3 in rat hepatocytes(1). 1061 88


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