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 The role of acetyl-CoA carboxylase phosphorylation in the control of mammary gland fatty acid synthesis during the starvation and re-feeding of lactating rats

1986 ◽  
Vol 237 (1) ◽  
pp. 85-91 ◽  
Author(s):  
M R Munday ◽  
D G Hardie
Keyword(s):  
Mammary Gland ◽  
Kinetic Parameters ◽  
Protein Phosphatase ◽  
Mammary Glands ◽  
Phosphate Content ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity

Activation of acetyl-CoA carboxylase during incubation of crude extracts of lactating rat mammary gland with Mg2+ and citrate can be blocked by NaF, suggesting that it represents a dephosphorylation of the enzyme. The greater extent of activation in extracts from 24 h-starved rats (200%) compared with fed controls (70%) implies that the decrease in acetyl-CoA carboxylase activity in response to 24 h starvation may involve increased phosphorylation of the enzyme. Acetyl-CoA carboxylase was purified from the mammary glands of lactating rats in the presence of protein phosphatase inhibitors by avidin-Sepharose chromatography. Starvation of the rats for 24 h increased the concentration of citrate giving half-maximal activation by 75%, and decreased the Vmax. of the purified enzyme by 73%. This was associated with an increase in the alkali-labile phosphate content from 3.3 +/- 0.2 to 4.5 +/- 0.4 mol/mol of enzyme subunit. Starvation of lactating rats for 6 h, or short-term insulin deficiency induced by streptozotocin injection, did not effect the kinetic parameters or the phosphate content of acetyl-CoA carboxylase purified from mammary glands. The effects of 24 h starvation on the kinetic parameters and phosphate content of the purified enzyme were completely reversed by re-feeding for only 2.5 h. This effect was blocked if the animals were injected with streptozotocin before re-feeding, suggesting that the increase in plasma insulin that occurs on re-feeding was responsible for the activation of the enzyme. The effects of re-feeding 24 h-starved rats on the kinetic parameters and phosphate content of acetyl-CoA carboxylase could be mimicked by treating enzyme purified from 24 h-starved rats with protein phosphatase-2A in vitro. Our results suggest that, in mammary glands of 24 h-starved lactating rats, insulin brings about a dephosphorylation of acetyl-CoA carboxylase in vivo, which may be at least partly responsible for the reactivation of mammary lipogenesis in response to re-feeding.

Prolactin-stimulated polymerization of acetyl-CoA carboxylase in explants of mid-pregnant rat mammary gland

2001 ◽  
Vol 68 (3) ◽  
pp. 351-355 ◽  
Author(s):  
JULIUS E. OBEN ◽  
RAYMOND R. DILS
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Specific Activity ◽  
Acid Synthesis ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Pregnant Rat ◽  
Rat Mammary Gland ◽  
Total Enzyme

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.

The role of growth hormone, prolactin and insulin-like growth factors in the regulation of rat mammary gland and adipose tissue metabolism during lactation

1992 ◽  
Vol 135 (2) ◽  
pp. 195-202 ◽  
Author(s):  
M. C. Barber ◽  
R. A. Clegg ◽  
E. Finley ◽  
R. G. Vernon ◽  
D. J. Flint
Keyword(s):  
Adipose Tissue ◽  
Mammary Gland ◽  
Lipid Metabolism ◽  
Weight Gain ◽  
Lipoprotein Lipase ◽  
Milk Production ◽  
Secretory Cells ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Litter Weight

ABSTRACT Inhibition of prolactin secretion with bromocriptine and neutralization of GH action with a specific antiserum to rat GH (rGH) were used to explore the modes of action of GH and prolactin in maintaining lactation in the rat. Treatment of dams with anti-rGH caused a small reduction in litter weight gain whilst bromocriptine reduced litter weight gain by 50%. When both treatments were combined, however, milk yield ceased completely and this wasaccompanied by a wide variety of effects on mammary lipid metabolism including decreases in the mRNA concentrations of acetyl CoA carboxylase, fatty acid synthase, malic enzyme and lipoprotein lipase. Activities of acetyl CoA carboxylase and lipoprotein lipase were also significantly reduced. Reciprocal changes were evident in adipose tissue with increases in acetyl CoA carboxylase and lipoprotein lipase activities. In conjunction with a decreased lipolytic response to noradrenaline in adipose tissue of animals given the combined treatment of bromocriptine and anti-rGH, this represented a co-ordinated series of changes to reduce lipid synthesis in the mammary gland and enhance lipogenesis and triglyceride storage in adipose tissue as milk production ceased. All of these effects could be prevented in part by concurrent treatment with GH, but insulin-like growth factor-I (IGF-I) and IGF-II failed to affect any of the parameters measured. Taken as a whole, these data suggest that (1) both prolactin and GH induce a co-ordinated series of changes in the mammary gland, (2) the intracellular controls involved clearly operate at the level of gene transcription although post-translational controls are also probably involved, (3) the effects of GH on the mammary gland could not be mimicked by IGFs and (4) although GH clearly regulates lipid metabolism in adipose tissue in a manner which should favour nutrient utilization by the mammary gland, these effects are probably too small to account for the effects of GH on milk production. Since GH receptors have not been reported to be present on mammary secretory cells, the precise mode of action of GH remains uncertain. Journal of Endocrinology (1992) 135, 195–202

scholarly journals Regulation of acetyl-CoA carboxylase in rat mammary gland. Effects of incubation with Ca2+, Mg2+ and ATP on enzyme activity in tissue extracts

1981 ◽  
Vol 200 (3) ◽  
pp. 639-644 ◽  
Author(s):  
E M McNeillie ◽  
R A Clegg ◽  
V A Zammit
Keyword(s):  
Mammary Gland ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Kinase Inhibitor ◽  
Enzyme Activation ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Rat Mammary Gland ◽  
Subsequent Activation

1. The effect of preincubation of extracts of lactating rat mammary gland with ATP, Mg2+ and micromolar concentrations of Ca2+ on the activity of acetyl-CoA carboxylase was studied. 2. Both Mg2+ and Ca2+ activated the enzyme. Activation with Mg2+ (5 mM) was larger than that with Ca2+ (calculated free Ca2+ concentration = 20-50 microM), but the activity decreased after reaching a peak. The activation obtained with Ca2+ was stable for up to 180 min. 3. Incubation with Ca2+ and Mg2+ together resulted in an activation that was slightly higher than that with Mg2+ only and was stable (compare the results for Ca2+ alone). 4. Preincubation in the absence of Mg2+, but not in the absence of Ca2+, resulted in the impairment of subsequent activation with either Mg2+ (when preincubation was with Ca2+ alone) or Mg2+ plus Ca2+. 5. KF (50 mM) prevented the activation of acetyl-CoA carboxylase by Ca2+ and Mg2+. 6. MgATP2- reversed (Mg2+ + Ca2+)-mediated activation and decreased the activity of acetyl-CoA carboxylase to about 10% of initial activity. Inhibition by ATP was unaffected by addition of cyclic AMP or cyclic AMP-dependent protein kinase inhibitor. 7. 32P was incorporated into acetyl-CoA carboxylase when incubations were carried out in the presence of [gamma-32P]ATP. Subsequent removal of ATP from the incubation medium resulted in rapid loss of 32P from acetyl-CoA carboxylase. 8. It is suggested that extracts of rat mammary gland contain endogenous protein kinase and phosphatase activities that modulate acetyl-CoA carboxylase activity through reversible phosphorylation and dephosphorylation. The phosphatase activity is sensitive to both Mg2+ and micromolar concentrations of Ca2+, whereas the kinase does not appear to be cyclic AMP-dependent.

scholarly journals Protein-serine kinase from rat epididymal adipose tissue which phosphorylates and activates acetyl-CoA carboxylase. Possible role in insulin action

1990 ◽  
Vol 270 (3) ◽  
pp. 795-801 ◽  
Author(s):  
A C Borthwick ◽  
N J Edgell ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Insulin Action ◽  
Kinase Activity ◽  
Potent Inhibitor ◽  
Fold Increase ◽  
Epididymal Adipose Tissue ◽  
Acetyl Coa Carboxylase ◽  
Serine Kinase ◽  
Acetyl Coa ◽  
Carboxylase Activity

1. Most of the cyclic-nucleotide-independent acetyl-CoA carboxylase kinase activity in an extract of rat epididymal adipose tissue was evaluated from a Mono Q column by 0.175 M-NaCl at pH 7.4. The activity of the kinase in this fraction (fraction 1) was increased after exposure of intact tissue to insulin. 2. Incubation of purified adipose-tissue acetyl-CoA carboxylase with [gamma-32P]ATP and samples of fraction 1 led to the incorporation of up to 0.4 mol of 32P/mol of enzyme subunit. Most of the phosphorylation was on serine residues within a single tryptic peptide. This peptide, on the basis of two-dimensional t.l.c. analysis, h.p.l.c. and Superose 12 chromatography, appeared to be the same as the acetyl-CoA carboxylase peptide (‘I’-peptide) which exhibits increased phosphorylation in insulin-treated tissue. 3. Phosphorylation of purified acetyl-CoA carboxylase by the kinase in fraction 1 was found to be associated with a parallel 4-fold increase in activity. However, increases in both phosphorylation and activity were much diminished if fraction 1 was treated by Centricon centrifugation to remove low-Mr components. Among these components was a potent inhibitor of acetyl-CoA carboxylase activity which appeared to be necessary for the kinase in fraction 1 to be fully active. 4. The inhibitor remains to be identified, but inhibition requires MgATP, although the inhibitor itself does not cause any phosphorylation of the carboxylase. No effects of insulin were observed on the activity of the inhibitor. 5. It is concluded that the kinase probably plays an important role in the mechanism whereby insulin brings about the well-established increases in phosphorylation and activation of acetyl-CoA carboxylase in adipose tissue.

scholarly journals Acute effects in vivo of anti-insulin serum on rates of fatty acid synthesis and activities of acetyl-coenzyme A carboxylase and pyruvate dehydrogenase in liver and epididymal adipose tissue of fed rats

1976 ◽  
Vol 160 (2) ◽  
pp. 413-416 ◽  
Author(s):  
D Stansbie ◽  
R W Brownsey ◽  
M Crettaz ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Pyruvate Dehydrogenase ◽  
Acid Synthesis ◽  
Epididymal Adipose Tissue ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity

Plasma insulin concentrations in fed rats were altered acutely by administration of glucose or anti-insulin serum. Rates of fatty acid synthesis in adipose tissue and liver were estimated from the incorporation of 3H from 3H2O. In the adipose tissue dehydrogenase and acetyl-CoA carboxylase were evident. In liver, although changes in rates of fatty acid synthesis were found, the initial activity of pyruvate dehydrogenase did not alter, but small parallel changes in acetyl-CoA carboxylase activity were observed.

scholarly journals Evidence that noradrenaline increases pyruvate dehydrogenase activity and decreases acetyl-CoA carboxylase activity in rat interscapular brown adipose tissue in vivo

1985 ◽  
Vol 228 (3) ◽  
pp. 751-755 ◽  
Author(s):  
J M Gibbins ◽  
R M Denton ◽  
J G McCormack
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Acid Synthesis ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose

The rate of fatty acid synthesis in interscapular brown adipose tissue of female cold-adapted rats, as measured by the incorporation of 3H from 3H2O into tissue lipid, was decreased by about 70% after injection of noradrenaline. There was a similar decrease in the activity of acetyl-CoA carboxylase. In contrast, the proportion of pyruvate dehydrogenase in its active non-phosphorylated form was greatly increased after injection of noradrenaline. This finding suggests that the oxidation of glucose may be important in noradrenaline-induced thermogenesis in rat brown adipose tissue.

Repression of the acetyl-CoA carboxylase gene in ovine adipose tissue during lactation: the role of insulin responsiveness

1997 ◽  
Vol 19 (2) ◽  
pp. 99-107 ◽  
Author(s):  
MT Travers ◽  
RG Vernon ◽  
MC Barber
Keyword(s):  
Enzyme Activity ◽  
Adipose Tissue ◽  
Late Pregnancy ◽  
Active State ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Alpha Tubulin ◽  
Total Enzyme Activity ◽  
Adipose Tissue Depots

We have investigated the mechanisms whereby lipogenesis is markedly suppressed in adipose tissue depots of lactating sheep. Expression of the gene encoding acetyl-CoA carboxylase (ACC), the flux-determining enzyme of the lipogenic pathway, is reduced approximately threefold in both omental and subcutaneous adipose tissue depots during late pregnancy and remains so into lactation when compared with non-pregnant, non-lactating animals. By comparison, total ACC enzyme activity in these adipose depots is suppressed approximately 25- to 30-fold in lactation. Culture of explants from the subcutaneous depot of lactating sheep with insulin plus dexamethasone for 72 h resulted in an approximately sevenfold increase in ACC mRNA, a fivefold increase in total enzyme activity and a marked increase in the proportion of the enzyme in the active state when compared with explants cultured with no added hormones for the same period. However, there was a lag of between 32 and 48 h before marked induction of any of these parameters by insulin plus dexamethasone was observed. Induction of the alpha-tubulin gene paralleled that of the ACC gene, suggesting that cytoskeletal rearrangements are associated with the aquisition of sensitivity to insulin plus dexamethasone. These results demonstrate that the reduction in lipogenic capacity in ovine adipose tissue during lactation is related to repression of the ACC gene, both at the level of steady-state mRNA abundance and possibly at translation, as well as to suppression of the mechanisms that regulate the proportion of ACC in the active state, and these are further related to the marked insensitivity of these parameters to insulin plus dexamethasone in vitro.

GH inhibition of lipogenesis and stimulation of lipolysis in sheep adipose tissue: involvement of protein serine phosphorylation and dephosphorylation and phospholipase C

1996 ◽  
Vol 150 (1) ◽  
pp. 129-140 ◽  
Author(s):  
R G Vernon
Keyword(s):  
Adipose Tissue ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Phorbol Ester ◽  
Okadaic Acid ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Kinase C ◽  
Activation Status

Abstract The intracellular signalling systems involved in the chronic insulin-antagonistic, anti-lipogenic effects and also the lipolytic effect of GH have been investigated in sheep adipose tissue in an in vitro tissue culture system. During culture, chronic exposure to GH decreased the rate of lipogenesis and prevented the increase in lipogenesis induced by insulin. GH also increased glycerol release into the culture medium. GH had no acute, insulin-like effect on lipogenesis in sheep adipose tissue. Pretreatment with phorbol ester to down-regulate isoforms of protein kinase C or addition of the protein serine kinase inhibitor staurosporine decreased the anti-lipogenic effect of GH while the protein serine kinase inhibitor H7 eliminated it completely. Pretreatment with phorbol ester or addition of H7 also decreased the insulin-antagonistic effect of GH on lipogenesis. Addition of the protein serine phosphatase inhibitor okadaic acid or the phosphatidyl choline phospholipase C inhibitor D609 both diminished the anti-lipogenic and insulin-antagonistic effects of GH. Chronic exposure of adipose tissue to GH had no effect on the total activity of acetyl CoA carboxylase or its activation status but it did diminish the increase in activation status induced by insulin. H7 and okadaic acid also diminished the increase in activation status of acetyl CoA carboxylase induced by insulin but did not alter the effect of GH on this variable. Okadaic acid decreased total acetyl CoA carboxylase activity. Pretreatment with phorbol ester or the addition of H7, staurosporine or okadaic acid increased glycerol release into the culture medium to the same extent as GH itself; the effects of GH and these various agents were not additive. These studies suggest that the anti-lipogenic, insulin-antagonistic effects of GH involve both protein serine kinases and phosphatases, possibly including one or more isoforms of protein kinase C, and a phosphatidyl choline-specific phospholipase C. Comparison with studies by others on the GH enhancement of preadipocyte differentiation and prolactin stimulation of lipogenesis in mammary tissue suggests involvement of protein kinase C at an early stage in all three systems. In contrast, effects of okadaic acid vary with the system, suggesting the involvement of protein serine phosphatase activity in a late stage of the action of GH. The effects of GH on lipogenesis and lipolysis do not occur via identical mechanisms. Journal of Endocrinology (1996) 150, 129–140

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