Properties of a phosphoprotein phosphatase from rat epididymal fat pads: deactivation of hormone-sensitive triglyceride lipase and activation of glycogen synthase in adipose tissue

1980 ◽  
Vol 58 (3) ◽  
pp. 243-250 ◽  
Author(s):  
David L. Severson ◽  
Shellie Sloan
Keyword(s):  
Adipose Tissue ◽  
Phosphatase Activity ◽  
Glycogen Synthase ◽  
Adenine Nucleotides ◽  
Fat Pad ◽  
Phosphoprotein Phosphatase ◽  
Triglyceride Lipase ◽  
Epididymal Fat ◽  
Hormone Sensitive ◽  
Fat Pads

A phosphoprotein phosphatase has been partially purified from rat epididymal fat pads by a procedure utilizing ammonium sulfate and ethanol precipitations and chromatography on DEAE-Sephadex A-50. The phosphatase was eluted from Sephadex G-75 columns with an apparent molecular weight of 28 000. The phosphoprotein phosphatase catalyzed the reversible deactivation of protein kinase activated chicken adipose tissue hormone-sensitive triglyceride lipase. Phosphatase activity measured with activated triglyceride lipase as substrate was completely dependent upon the presence of metal ions (Mg2+, Ca2+, or Mn2+) and was inhibited by inorganic phosphate and adenine nucleotides. The fat pad phosphatase increased the rate of activation of glycogen synthase in rat adipose tissue infranatant fractions from fed and 24-h-fasted rats but had little or no effect on synthase activity in infranatant fractions from rats fasted for 48 h. Fasting had no effect on rat fat pad phosphatase activity measured with triglyceride lipase as substrate, but phosphatase activity was decreased in preparations from diabetic rats.

Alterations of lipolysis and lipoprotein lipase in chronically nicotine-treated rats

1996 ◽  
Vol 270 (2) ◽  
pp. E215-E223 ◽  
Author(s):  
C. Sztalryd ◽  
J. Hamilton ◽  
B. A. Horwitz ◽  
P. Johnson ◽  
F. B. Kraemer
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Hormone Sensitive Lipase ◽  
Mrna Levels ◽  
Cellular Mechanisms ◽  
Fed State ◽  
Epididymal Fat ◽  
Hormone Sensitive ◽  
Lpl Mass ◽  
Fat Pads

These studies examined the cellular mechanisms for lower adiposity seen with nicotine ingestion. Rats were infused with nicotine or saline for 1 wk and adipocytes isolated from epididymal fat pads. Nicotine-infused rats gained 37% less weight and had 21% smaller fat pads. Basal lipolysis was 78% higher, whereas the maximal lipolytic response to isoproterenol was blunted in adipocytes from nicotine-infused rats. The antilipolytic actions of adenosine and the levels of serum catecholamines were unaffected by nicotine. The nicotine-induced alteration in lipolysis was not associated with any changes in hormone-sensitive lipase. Nicotine caused a 30% decrease in lipoprotein lipase (LPL) activity, without any changes in LPL mass or mRNA levels, in epididymal fat in the fed state. In contrast, LPL activity, mass, and mRNA levels in heart were increased by nicotine whether animals were fed or fasted. These studies provide evidence for multiple mechanistic events underlying nicotine-induced alterations in weight and suggest that nicotine diverts fat storage away from adipose tissue and toward utilization by muscle.

scholarly journals The effects of food deprivation and re-feeding on bovine adipose-tissue glycogen synthase

1979 ◽  
Vol 184 (2) ◽  
pp. 229-232 ◽  
Author(s):  
R D Eichner ◽  
R J Arnold
Keyword(s):  
Adipose Tissue ◽  
Phosphatase Activity ◽  
Food Deprivation ◽  
Glycogen Content ◽  
Specific Activity ◽  
Glycogen Synthase ◽  
Glycogen Metabolism ◽  
Phosphoprotein Phosphatase ◽  
Tissue Extracts ◽  
Rat Adipose Tissue

Bovine adipose-tissue glycogen metabolism was studied during food deprivation and re-feeding. Changes in the specific activity of adipose-tissue glycogen synthase paralleled changes in tissue glycogen content: both parameters increased during food deprivation and remained so during the first 10 days of re-feeding. The values for the A0.5 (activation constant) for glucose 6-phosphate of the freshly isolated enzyme from adipose tissue from fed and starved steers were 2.9 +/- 0.1 mM and 0.90 +/- 0.05 mM respectively. Additionally, whereas incubation of adipose-tissue extracts from fed steers did not activate endogenous glycogen synthase (through a presumed phosphoprotein phosphatase mechanism), the enzyme from starved or re-fed (up to 3 days re-feeding) steers was reversibly activated as measured by changes in the value for the A0.5 for glucose 6-phosphate. Thus activation of bovine adipose-tissue glycogen synthase during food deprivation appears to be related to expression of glycogen synthase phosphatase activity. These effects of food deprivation on bovine glycogen metabolism contrast markedly with the effects observed in rat adipose tissue.

scholarly journals Dephosphorylation and activation of exogenous glycogen synthase by adipose-tissue phosphatase

1980 ◽  
Vol 188 (1) ◽  
pp. 221-228 ◽  
Author(s):  
Joan Heller Brown ◽  
Ronald D. Eichner ◽  
Barbara Thompson ◽  
Steven Mayer
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Protein Kinase ◽  
Phosphatase Activity ◽  
Muscle Glycogen ◽  
Glycogen Synthase ◽  
Enzyme Activation ◽  
Phosphoprotein Phosphatase ◽  
Tissue Extracts ◽  
Lag Period

Exogenous purified rabbit skeletal-muscle glycogen synthase was used as a substrate for adipose-tissue phosphoprotein phosphatase from fed and starved rats in order to (1) compare the relationship between phosphate released from, and the kinetic changes imparted to, the substrate and (2) ascertain if decreases in adipose-tissue phosphatase activity account for the apparent decreased activation of endogenous glycogen synthase from starved as compared with fed rats. Muscle glycogen synthase was phosphorylated with [γ-32P]ATP and cyclic AMP-dependent protein kinase alone, or in combination with a cyclic AMP-independent protein kinase, to 1.7 or 3mol of phosphate per subunit. Adipose-tissue phosphatase activity determined with phosphorylated skeletal-muscle glycogen synthase as substrate was decreased by 35–60% as a consequence of starvation. This decrease in phosphatase activity had little effect on the capacity of adipose-tissue extracts to activate exogenous glycogen synthase (i.e. to increase the glucose 6-phosphate-independent enzyme activity), although there were marked differences in the activation profiles for the two exogenous substrates. Glycogen synthase phosphorylated to 1.7mol of phosphate per subunit was activated rapidly by adipose-tissue extracts from either fed or starved rats, and activation paralleled enzyme dephosphorylation. Glycogen synthase phosphorylated to 3mol of phosphate per subunit was activated more slowly and after a lag period, since release of the first mol of phosphate did not increase the glucose 6-phosphate-independent activity of the enzyme. These patterns of enzyme activation were similar to those observed for the endogenous adipose-tissue glycogen synthase(s): the glucose 6-phosphate-independent activity of the endogenous enzyme from fed rats increased rapidly during incubation, whereas that of starved rats, like that of the more highly phosphorylated muscle enzyme, increased only very slowly after a lag period. The observations made here suggest that (1) changes in glucose 6-phosphate-independent glycogen synthase activity are at best only a qualitative measure of phosphoprotein phosphatase activity and (2) the decrease in glycogen synthase phosphatase activity during starvation is not sufficient to explain the differential glycogen synthase activation in adipose tissue from fed and starved rats. However, alterations in the phosphorylation state of glycogen synthase combined with decreased activity of phosphoprotein phosphatase, both as a consequence of starvation, could explain the apparent markedly decreased enzyme activation.

Catecholaminergic innervation of white adipose tissue in Siberian hamsters

1995 ◽  
Vol 268 (3) ◽  
pp. R744-R751 ◽  
Author(s):  
T. G. Youngstrom ◽  
T. J. Bartness
Keyword(s):  
Adipose Tissue ◽  
White Adipose Tissue ◽  
Neural Control ◽  
Fat Pad ◽  
Anterograde Transport ◽  
Siberian Hamsters ◽  
Lipid Stores ◽  
Catecholaminergic Innervation ◽  
Fat Pads

When Siberian hamsters are transferred from long summerlike days (LDs) to short winterlike days (SDs) they decrease their body weight, primarily as body fat. These SD-induced decreases in lipid stores are not uniform. Internally located white adipose tissue (WAT) pads are depleted preferentially of lipid, whereas the more externally located subcutaneous WAT pads are relatively spared. These data suggest a possible differential sympathetic neural control over catecholamine-induced lipolysis and that lipolytic rates are greater for internal vs. external WAT pads. Moreover, if these differential rates of lipolysis are due to differential sympathetic nervous system (SNS) drives on the pads, then fat pad-specific catecholaminergic innervation may exist. Therefore, we tested whether inguinal WAT (IWAT; an external pad) and epididymal WAT (EWAT; an internal pad) were innervated differentially. In addition, we tested whether norepinephrine (NE) turnover (TO) reflected the presumed greater SNS drive on EWAT vs. IWAT after SD exposure. Injections of fluorescent tract tracers [Fluoro-Gold or indocarbocyanine perchlorate (DiI)] demonstrated projections from the SNS ganglia T13-L3 to both fat pads. Retrograde labeling revealed a relatively separate pattern of distribution of labeled neurons in the ganglia projecting to each pad. In vivo anterograde transport of DiI resulted in labeling in both IWAT and EWAT that included staining around individual adipocytes and occasionally retrogradely labeled cells. The proportionately greater decrease in EWAT compared with IWAT mass after 5 wk of SD exposure was reflected in greater EWAT NE TO than found in their LD counterparts for this pad.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Effects of PKB/Akt inhibitors on insulin-stimulated lipogenesis and phosphorylation state of lipogenic enzymes in white adipose tissue

2020 ◽  
Vol 477 (8) ◽  
pp. 1373-1389
Author(s):  
Nusrat Hussain ◽  
Sheng-Ju Chuang ◽  
Manuel Johanns ◽  
Didier Vertommen ◽  
Gregory R. Steinberg ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
White Adipose Tissue ◽  
Acute Effects ◽  
Lipogenic Enzymes ◽  
Atp Citrate Lyase ◽  
Phosphorylation State ◽  
Epididymal Fat ◽  
Citrate Lyase ◽  
Fat Pads

We investigated acute effects of two allosteric protein kinase B (PKB) inhibitors, MK-2206 and Akti-1/2, on insulin-stimulated lipogenesis in rat epididymal adipocytes incubated with fructose as carbohydrate substrate. In parallel, the phosphorylation state of lipogenic enzymes in adipocytes and incubated epididymal fat pads was monitored by immunoblotting. Preincubation of rat epididymal adipocytes with PKB inhibitors dose-dependently inhibited the following: insulin-stimulated lipogenesis, increased PKB Ser473 phosphorylation, increased PKB activity and decreased acetyl-CoA carboxylase (ACC) Ser79 phosphorylation. In contrast, the effect of insulin to decrease the phosphorylation of pyruvate dehydrogenase (PDH) at Ser293 and Ser300 was not abolished by PKB inhibition. Insulin treatment also induced ATP-citrate lyase (ACL) Ser454 phosphorylation, but this effect was less sensitive to PKB inhibitors than ACC dephosphorylation by insulin. In incubated rat epididymal fat pads, Akti-1/2 treatment reversed insulin-induced ACC dephosphorylation, while ACL phosphorylation by insulin was maintained. ACL and ACC purified from white adipose tissue were poor substrates for PKBα in vitro. However, effects of wortmannin and torin, along with Akti-1/2 and MK-2206, on recognized PKB target phosphorylation by insulin were similar to their effects on insulin-induced ACL phosphorylation, suggesting that PKB could be the physiological kinase for ACL phosphorylation by insulin. In incubated epididymal fat pads from wild-type versus ACC1/2 S79A/S212A knockin mice, effects of insulin to increase lipogenesis from radioactive fructose or from radioactive acetate were reduced but not abolished. Together, the results support a key role for PKB in mediating insulin-stimulated lipogenesis by decreasing ACC phosphorylation, but not by decreasing PDH phosphorylation.

Effect of cold stress on lipogenesis by adipose tissue

1960 ◽  
Vol 198 (5) ◽  
pp. 1123-1125 ◽  
Author(s):  
E. J. Masoro ◽  
Edith Porter ◽  
Judith Patkin
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Cold Stress ◽  
Incubation Medium ◽  
Acetate Metabolism ◽  
Hepatic Lipogenesis ◽  
Acetate Oxidation ◽  
Fat Pad ◽  
Striking Finding ◽  
Epididymal Fat

The effect of cold stress on acetate metabolism by adipose tissue was investigated. Cold stress did not affect the ability of the epididymal fat pad to oxidize acetate-1-C14 to C14O2. The addition of unlabeled glucose to the incubation medium did not influence the rate of acetate oxidation in the case of adipose tissue obtained from either control or cold-stressed rats. In the absence of unlabeled glucose, more fatty acids from acetate-1-C14 were synthesized by the adipose tissue from control rats than by that from cold-stressed rats, although very little was synthesized by either. The addition of unlabeled glucose to the incubation medium at the physiologic concentration of 100 mg % caused the adipose tissue from both normal and cold-stressed rats to form fatty acids at high rates. It is a striking finding that cold stress, which almost abolishes hepatic lipogenesis, does not appreciably alter adipose tissue lipogenesis.

Lipogenesis in adipose tissue of rats fed different diets

1961 ◽  
Vol 201 (6) ◽  
pp. 1041-1043 ◽  
Author(s):  
J. M. Khanade ◽  
M. C. Nath
Keyword(s):  
Adipose Tissue ◽  
Glucose Uptake ◽  
Alloxan Diabetes ◽  
High Protein ◽  
Vitamin B ◽  
High Fat ◽  
Epididymal Fat ◽  
Increase Glucose Uptake ◽  
Fat Pads

Lipogenesis and glucose uptake by epididymal fat pads of rats fed different diets have been investigated. Lipogenesis was found to be depressed in rats fed high fat, high fat and high protein, thyroid, thiouracil, and thiamine-deficient diets. The same dose of insulin causes varying degrees of lipogenesis in the tissues, depending on the type of diet fed previously. Lipogenesis is above normal in hydrolyzed glucose-cycloacetoacetate-fed rats but glucose uptake is not appreciably affected. The glucose uptake of adipose tissue is significantly depressed in rats fed high fat, high fat with high protein, and vitamin B1 deficient diets, and in rats with hypothyroidism. Both hyperthyroidism and hydrolyzed glucose-cycloacetoacetate feeding increase glucose uptake by the tissue. Alloxan diabetes reduces lipogenesis as well as glucose uptake.

Effect of exercise on hormone-sensitive lipase activity in rat adipocytes

1976 ◽  
Vol 230 (2) ◽  
pp. 385-388 ◽  
Author(s):  
JA McGarr ◽  
LB Oscai ◽  
J Borensztajn
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Adipose Tissue ◽  
Free Fatty Acids ◽  
Lipase Activity ◽  
Exercise Program ◽  
Treadmill Running ◽  
Hormone Sensitive Lipase ◽  
Hormone Sensitive ◽  
Fat Pads

Hormone-sensitive lipase activity was measured in adipocytes of rats subjected to a 12-wk program of treadmill running. Enzyme activity in the runners sacrificed immediately after exercise increased 2.5-fold (P less than 0.001) in tissue exposed to epinephrine and threefold (P less than 0.001) in tissue not exposed to epinephrine, when the results were expressed per gram of adipose tissue. Increases of almost the same magnitude were observed in runners sacrificed 24 h after their last bout of work. These significant increases in enzyme activity, however, were the result of a significant reduction in the size of cells in the epididymal fat pads of the exercisers compared with those of the freely eating sedentary animals (68.7 +/- 2.7 mum vs. 82.0 +/- 2.7 mum; P less than 0.01). When the results were expressed on a per-cell basis, therefore, hormone-sensitive lipase activity, assayed in the presence or absence of epinephrine, was unaffected by the exercise program. These results provide evidence that the lipolytic capacity of adipocytes of normal, untrained rats is sufficiently large to meet the increased demand for free fatty acids imposed by the exercise program without the need for an adaptive increase in enzyme activity.

scholarly journals The biosynthesis of squalene and sterols by the adipose tissue of rat, sheep and man

1966 ◽  
Vol 98 (1) ◽  
pp. 317-320 ◽  
Author(s):  
I F Durr
Keyword(s):  
Adipose Tissue ◽  
Mevalonic Acid ◽  
Omental Adipose Tissue ◽  
Fat Tail ◽  
Epididymal Fat ◽  
Fat Pads

1. The subcutaneous and omental adipose tissue of man, the epididymal fat pads of the rat and the fat tail of the Syrian sheep incorporate mevalonic acid into non-saponifiable lipids. 2. Time studies showed that the rates of decarboxylation of mevalonic acid and synthesis of non-saponifiable lipids slightly decline after 20min. but subsequently remain linear for 6hr. 3. About one-half of the incorporated radioactivity in the non-saponifiable lipids was in squalene, 20% in lanosterol and cholesterol, and the remainder in unidentified substances.

scholarly journals Coenzyme A is a potent inhibitor of acetyl-CoA carboxylase from rat epididymal fat-pads

1992 ◽  
Vol 283 (1) ◽  
pp. 35-38 ◽  
Author(s):  
S K Moule ◽  
N J Edgell ◽  
A C Borthwick ◽  
R M Denton
Keyword(s):  
Potent Inhibitor ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Acetyl Coa Carboxylase ◽  
Inhibitory Effects ◽  
Fat Pad ◽  
Maximal Inhibition ◽  
Acetyl Coa ◽  
Epididymal Fat ◽  
Fat Pads

Rat epididymal fat-pad extracts have previously been shown to contain an insulin-stimulated acetyl-CoA carboxylase kinase, which is co-eluted from Mono Q ion-exchange chromatography with a potent inhibitor of acetyl-CoA carboxylase [Borthwick, Edgell & Denton (1990) Biochem. J. 270, 795-801]. A variety of tests, including reactivity with thiol reagents, identify this inhibitor as CoA. Inhibition requires the presence of MgATP, but is independent of any phosphorylation of the enzyme. The effect is complete in about 5 min and is associated with depolymerization of acetyl-CoA carboxylase. Half-maximal inhibition is observed at about 40 nM-CoA. The inhibitory effects of CoA can be partially reversed by incubation with citrate and more fully overcome by treatment of the enzyme with the insulin-stimulated acetyl-CoA carboxylase kinase.

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