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)

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.
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PMID:Growth-hormone-prolactin interactions in the regulation of mammary and adipose-tissue acetyl-CoA carboxylase activity and gene expression in lactating rats. 135 48

The activities of lipogenic enzymes, such as acetyl-CoA carboxylase, fatty acid synthetase and glucose-6-phosphate dehydrogenase, and glycerolipid synthesis increased significantly in mammary explants of 11-day-pseudopregnant rabbits in response to prolactin, in the presence of near-physiological concentrations of insulin and corticosterone in culture. Increasing the concentration of progesterone in culture resulted in suppression of glycerolipid synthesis and activities of acetyl-CoA carboxylase and fatty acid synthetase, but not the pentose phosphate dehydrogenases. However, at near-physiological concentration of progesterone, only acetyl-CoA carboxylase activity was decreased. Injection of prolactin intraductally into 11-day-pseudopregnant rabbits stimulated glycerolipid synthesis, fatty acid synthesis and enzymes involved in fatty acid synthesis, after 3 days. Intraductal injection of progesterone separately or together with prolactin had no significant effect on basal or stimulated lipogenesis in mammary glands. Intramuscular injection of progesterone at 10 mg/day did not suppress fatty acid synthesis stimulated when prolactin was injected intraductally, but a significant inhibition was observed at a higher dose (80 mg/day).
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PMID:The effect of progesterone on prolactin stimulation of fatty acid synthesis, glycerolipid synthesis and lipogenic-enzyme activities in mammary glands of pseudopregnant rabbits, after explant culture or intraductal injection. 406 99

The activities of acetyl-CoA carboxylase, ATP citrate-lyase and fatty acid synthetase remained low until parturition at 22 days of gestation and increased significantly within 1 day post partum. Administration of progesterone on days 20 and 21 and at parturition abolished the increases for at least 48 h after parturition. Removal of the pups of normal rats prevented the increases in activities of acetyl-CoA carboxylase and ATP citrate-lyase, but not of fatty acid synthetase, and administration of prolactin corticosterone or insulin did not stimulate activity. Tissue from suckled glands in which the ducts had been ligated at parturition showed no increase in the activities of acetyl-CoA carboxylase and ATP citrate-lyase within 24 h, whereas fatty acid synthetase activity was similar to that in the sham-operated contralateral glands. Foetoplacentectomy on day 18 increased the activity of fatty acid synthetase but not of acetyl-CoA carboxylase and ATP citrate-lyase; suckling of these dams by foster pups increased both acetyl-CoA carboxylase and ATP citrate-lyase.
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PMID:Initiation of lipogenic enzyme activities in rat mammary glands. 611 81

The ;initial' (I), endogenous phosphatase-activated (A) and citrate-activated (C) activities of acetyl-CoA carboxylase were measured in mammary-gland extracts of pregnant and lactating rats. There was a 10-fold increase in the A and C enzyme activities in the transition from early to peak lactation [cf. data of Mackall & Lane (1977) Biochem. J.162, 635-642], but there was no significant increase in the ratio of the initial activity to the A and C activities of the enzyme. Starvation (24h) or short-term (3h) streptozotocin-induced diabetes both resulted in a 40% decrease in I/A and I/C activity ratios. In starvation this was accompanied by a decrease in the absolute values of the A and C activities such that the initial activity in mammary glands of starved animals was 45% that in glands from fed animals. Insulin treatment of starved or diabetic animals 60min before killing increased the I activity without affecting the A or C enzyme activities. Removal of the pups for 24h from animals in peak lactation (weaning) resulted in a marked but similar decrease in all three activities such that, although the initial activity was only 10% of that in suckled animals, the I/A and I/C activity ratios remained high and unaltered. Inhibition of prolactin secretion by injection of 2-bromo-alpha-ergocryptine gave qualitatively similar results to those during weaning. Simultaneous administration of ovine prolactin completely prevented the effects of bromoergocryptine. It is suggested that the initial activity of acetyl-CoA carboxylase in rat mammary gland is regulated by at least two parallel mechanisms: (i) an acute regulation of the proportion of the enzyme in the active state and (ii) a longer-term modulation of enzyme concentration in the gland. Insulin appeared to mediate its acute effects through mechanism (i), whereas prolactin had longer-term effects on enzyme concentration in the gland. A comparison of initial enzyme activities (I) obtained in the present study with rates of lipogenesis measured in vivo [Agius & Williamson (1980) Biochem. J.192, 361-364; Munday & Williamson (1981) Biochem. J.196, 831-837] gave good agreement between the two sets of data for all conditions studied except for 24h-starved and streptozotocin-diabetic animals. It is suggested that acetyl-CoA carboxylase activity is rate-limiting for lipogenesis in the mammary gland in normal, fed, suckled or weaned animals but that in starved and short-term diabetic animals changes in the activity of the enzyme by covalent modification alone may not be sufficient to maintain the enzyme in its rate-limiting role.
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PMID:Regulation of acetyl-CoA carboxylase in rat mammary gland. Effects of starvation and of insulin and prolactin deficiency on the fraction of the enzyme in the active form in vivo. 612 84

1. The activity of acetyl-CoA carboxylase (EC 6.4.1.2) in extracts of freeze-clamped liver samples from fed or 24 h-starved virgin, pregnant, lactating and weaned rats was measured (i) immediately after preparation of extracts (;I activity'), (ii) after incubation of extracts with partially purified preparations of either rabbit muscle protein phosphatase 1 [Antoniw, Nimmo, Yeaman & Cohen (1977) Biochem. J.162, 423-433] or rabbit liver phosphatase [Brandt, Capulong & Lee (1975) J. Biol. Chem.250, 8038-8044] (;A activity') and (iii) after incubation with 20mm-potassium citrate before or after incubation with phosphatases (;C activity'). 2. Incubation of liver extracts at 30 degrees C without any additions resulted in activation of acetyl-CoA carboxylase that was shown to be due to dephosphorylation of the enzyme by endogenous protein phosphatase activity. This latter activity was not stimulated by Ca(2+) and/or Mg(2+) but was stimulated by 1 mm-Mn(2+). Incubation of extracts with either of the partially purified phosphatases (0.2-0.5 unit) resulted in faster dephosphorylation and activation. The activity achieved after incubation with either of the exogenously added phosphatases was similar. 3. The A and C activities increased during late pregnancy, were lower than in the virgin rat liver during early lactation and increased by 2-fold in liver of mid-lactating rats. Weaning of mid-lactating rats for 24 h resulted in no change in A and C activities but after 48 h weaning they were significantly lower than those in livers from suckled mothers. 4. The I activity followed a similar pattern of changes as the A and C activities during pregnancy and lactation such that, although the I/A and I/C activity ratios tended to be lower during late pregnancy and early lactation, there were no significant changes in I/A and I/C ratios between lactating and virgin animals. However, these ratios were significantly higher in liver from fed 24 h-weaned animals. 5. Starvation (24 h) resulted in a marked decrease in I activity for all animals studied except early-lactating rats. This was due to a combination of a decrease in the concentration of acetyl-CoA carboxylase in liver of starved animals (A and C activities) and a decrease in the fraction of the enzyme in the active form (lower I/C and I/A ratios). The relative importance of the two forms of regulation in mediating the starvation-induced fall in I activity was about equal in livers of virgin, pregnant and lactating animals. However, the decrease in I/A and I/C ratios was of dominating importance in livers of weaned animals. The A/C activity ratios were the same for livers from all animals studied. 6. The maximal activity of fatty acid synthase was also measured in livers and was highly and positively correlated with the A and C activities of acetyl-CoA carboxylase, suggesting that the concentrations of the two enzymes in the liver were controlled coordinately. 7. It is suggested that the lack of correlation between plasma insulin levels and rates of lipogenesis in the transition from the virgin to the lactating state may be explained by different effects of insulin and prolactin on the concentration of acetyl-CoA carboxylase in the liver and on the fraction of the enzyme in the active form.
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PMID:Changes in the proportion of acetyl-CoA carboxylase in the active form in rat liver. Effect of starvation, lactation and weaning. 612 71

Triacylglycerols make up 98% of the lipid content of milk, ranging in different species from 0 to 50% of the total milk volume. The fatty aid composition of the triacylglycerols depends on the species, the dietary fatty acid composition, and the carbohydrate-to-lipid ratio of the diet. The rate of lipid synthesis in the lactating mammary gland depends on the stage of mammary development and is decreased by fasting and starvation in ruminants and rodents but not in species that fast during lactation, such as seals and hibernating bears. Regulatory agents include insulin, prolactin, and non-esterified fatty acids. Dietary trans fatty acids may depress milk lipid synthesis under certain conditions. Evidence is presented that fatty acids may play a major regulatory role in acute changes in de novo mammary fatty acid synthesis, acting primarily on the activity of acetyl coenzyme A carboxylase.
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PMID:Regulation of milk lipid secretion and composition. 924 Sep 24

Exogenous GH is used extensively in the USA to stimulate milk production in dairy cattle but its effectiveness is reduced in undernourished animals. It has been proposed that GH increases milk yield by stimulating IGF-I secretion and that this IGF-I-response is nutritionally sensitive and thus acts as a 'sensor' of energy balance. To investigate this possibility, we placed lactating rats on three planes of nutrition, ad libitum, 50% or 25% of ad libitum for 48 h. Subgroups of these animals were treated for 48 h with bromocriptine, to suppress prolactin secretion, and anti-rat GH, to neutralize GH action. From 24 to 48 h some of the treated animals were assessed for their milk yield response to prolactin or GH. Food restriction reduced milk yield in control rats by approximately 50% and was accompanied by a catabolic state, as judged by lipid mobilization from adipose tissue and by low concentrations of serum insulin, IGF-I, triiodothyronine and thyroxine, and increased serum nonesterified fatty acid concentrations. In animals fed ad libitum, anti-rat GH plus bromocriptine treatment produced an 80% decrease in milk yield and a dramatic fall in the activity of acetyl-CoA carboxylase in mammary tissue. GH was able to stimulate milk yield when given from 24 to 48 h; however, its effectiveness decreased progressively as food intake was reduced. The milk yield response to GH was accompanied by an increase in serum IGF-I concentrations and this response also decreased progressively with reduction of food intake, consistent with the hypothesis that IGF-I determines the milk yield response to GH and thus regulates GH action on the mammary gland in a nutritionally dependent fashion. However, the milk yield response to prolactin and the milk yield of control rats decreased in line with food intake without any changes in serum IGF-I concentrations. This clearly indicates that factors other than IGF-I are responsible for restricting milk yield. In order to assess other possible candidates for this role, we monitored serum glucose, non-esterified fatty acids, insulin triiodothyronine and thyroxine concentrations, but found no evidence for any simple relationship between these parameters and the milk yield response to prolactin and GH. Surprisingly we found that the ability of GH or prolactin to prevent epithelial cell loss in in the mammary gland was completely insensitive to nutrient intake, despite the fact that IGF-I is considered to be an important survival factor for mammary epithelial cells. Finally, we also demonstrated that, at least during short-term food restriction, the lactating rat is capable of mobilizing significant amounts of lipid from adipose tissue, such that it could provide the total output of triglyceride in milk, which is much greater than has previously been proposed.
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PMID:Effects of food restriction on the responses of the mammary gland and adipose tissue to prolactin and growth hormone in the lactating rat. 951 76

Prolactin significantly increased the rate of fatty acid synthesis in explants of mid-pregnant rat mammary gland cultured for 96 h with insulin plus corticosterone. Under these conditions, prolactin increased the specific activity of total acetyl-CoA carboxylase in nuclear-free homogenates of explants by 2.6, and increased the proportion of the enzyme in the active polymeric form from 0.44 to 0.89. Removal of prolactin after 48 h in culture decreased the specific activity of the total enzyme by about half. and decreased the proportion as polymer to 0.52. The results show that prolactin plays a major role in mid-pregnant rat mammary gland in the polymerization which accompanies increased activity of the total enzyme and increased rate of fatty acid synthesis.
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PMID:Prolactin-stimulated polymerization of acetyl-coA carboxylase in explants of mid-pregnant rat mammary gland. 1169 38

Activity of acetyl-CoA carboxylase (ACC)-alpha is rate limiting for de novo synthesis of fatty acids. The encoding gene is expressed by three different promoters. We characterized promoter III (PIII) from cow, previously only known from sheep. Quantitation of transcripts by RNAse protection assays and real time PCR revealed that PIII is primarily expressed and strongly induced ( approximately 28-fold) in the lactating mammary gland. PIII transcripts are expressed in mammary epithelial cells (MEC) as shown by in situ hybridization. A 2999 bp segment of the PIII promoter conferred prolactin and dexamethasone inducibility to a luciferase reporter gene in stably transfected mouse MEC cells. Lactogenic induction was abolished if a unique signal transducer and activator of transcription (STAT)-binding site at position -797 was inactivated by two point mutations. An oligonucleotide probe harboring this STAT-site specifically bound nuclear proteins from the lactating mammary gland. Binding was abolished by those two point mutations and super-shift analyses showed that STAT5A factors are present in this complex. Hence, prolactin, acting through STAT5, contributes to the activation of ACC expression in the milk producing cells of the lactating mammary gland. We discuss that STAT5 might be important in determining the milk composition by coordinating fatty acid and protein synthesis during lactation.
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PMID:STAT5 binding contributes to lactational stimulation of promoter III expressing the bovine acetyl-CoA carboxylase alpha-encoding gene in the mammary gland. 1220 Feb 30

The heterozygous prolactin (PRL) receptor (PRLR(+/-)) mouse fails to develop a fully functional mammary gland at the end of the first pregnancy and shows markedly impaired lobuloalveolar development and milk secretion in young females. PRL and GH, acting through the IGF system, have interactive effects to enhance epithelial cell survival. Thus, we propose that a reduction in the expression of the PRLR may lead to increased IGFBP-5 expression (proapoptotic) and that GH may rescue mammary development by increasing IGF-I, an important mitogen and survival factor for the mammary epithelium. Mammary IGF-binding protein-5 (IGFBP-5) concentrations and plasmin activity in PRLR(+/-) mice were increased on d 2 postpartum, indicative of increased cell death and extracellular matrix remodeling. After GH treatment, a restoration of mammary alveolar development and a reduction in the activities of IGFBP-5 and plasmin were observed. Despite the severely impaired mammary development in PRLR(+/-) mice, both mRNA and protein expression for caseins and acetyl-coenzyme A (acetyl-CoA) carboxylase and acetyl-CoA caboxylase-alpha mRNA increased at parturition, although not to the extent in wild-type animals. Surprisingly, GH treatment actually led to a further decrease in milk protein and acetyl-CoA carboxylase-alphaexpression when expressed per cell. This was confirmed by the smaller alveolar size, the relative paucity of milk in the mammary glands of GH-treated animals, and the inability of their pups to gain weight. In a subsequent study IGFBP-5 was administered to wild-type mice and produced a 45% decrease in mammary DNA content, a 30% decrease in parenchymal tissue, and impaired lactation. These results suggest that GH can improve mammary development in PRLR(+/-) mice, but that it fails to enhance metabolic activity. This may be due to the maintenance by GH/IGF-I of a proliferative, rather than a differentiative, phenotype.
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PMID:Growth hormone, acting in part through the insulin-like growth factor axis, rescues developmental, but not metabolic, activity in the mammary gland of mice expressing a single allele of the prolactin receptor. 1239 27


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