scholarly journals The glycerol phosphate, dihydroxyacetone phosphate and monoacylglycerol pathways of glycerolipid synthesis in rat adipose-tissue homogenates

1976 ◽  
Vol 160 (3) ◽  
pp. 693-700 ◽  
Author(s):  
P F Dodds ◽  
M I Gurr ◽  
D N Brindley
Keyword(s):  
Adipose Tissue ◽  
Dihydroxyacetone Phosphate ◽  
Glycerol Phosphate ◽  
Epididymal Fat ◽  
Tissue Homogenates ◽  
Glycerolipid Synthesis ◽  
Acyl Acceptors ◽  
Rat Adipose Tissue ◽  
Fat Pads

1. Fat-free homogenates from the epididymal fat-pads of rats were used to measure the rate of palmitate esterification with different substrates. The effectiveness of the acyl acceptors decreased in the order glycerol phosphate, dihydroxyacetone phosphate, 2-octadecenyl-glycerol and 2-hexadecylglycerol. 2. Glycerol phosphate and dihydroxyacetone phosphate inhibited their rates of esterification in a mutually competitive manner. 3. The esterification of glycerol phosphate was also inhibited in a partially competitive manner by 2-octadecenylglycerol and to a lesser extent by 2-hexadecylglycerol. However, glycerol phosphate did not inhibit the esterification of 2-octadecenylglycerol. 4. The esterification of dihydroxyacetone phosphate and 2-hexadecylglycerol was more sensitive to inhibition by clofenapate than was that of glycerol phosphate. Norfenfluramine was more effective in inhibiting the esterification of 2-hexadecylglycerol than that of glycerol phosphate or dihydroxyacetone phosphate. 5 It is concluded that rat adipose tissue can synthesize glycerolipids by three independent routes.

scholarly journals The effects of diet on the esterification of glycerol phosphate, dihydroxyacetone phosphate and 2-hexadecylglycerol by homogenates of rat adipose tissue

1976 ◽  
Vol 160 (3) ◽  
pp. 701-706 ◽  
Author(s):  
P F Dodds ◽  
D N Brindley ◽  
M I Gurr
Keyword(s):  
Adipose Tissue ◽  
Beef Tallow ◽  
Corn Oil ◽  
Specific Activity ◽  
Body Weight Gain ◽  
Male Rats ◽  
Dihydroxyacetone Phosphate ◽  
Glycerol Phosphate ◽  
Triacylglycerol Content ◽  
Rat Adipose Tissue

1. Male rats were fed for 5 weeks after weaning on a diet containing (by weight) 59% of starch or on diets that contained 39% of starch and 20% of either sucrose, beef tallow or corn oil. 2. The rats fed on the beef tallow consumed more energy than did the rats fed on the starch and sucrose diets. The rats fed on the corn oil drank less water than did the other groups of rats. 3. There were no significant differences between the four groups in terms of body-weight gain, epididymal-fat-pad weight and in the size, number and triacylglycerol content of the adipocytes in the fat-pads. 4. There was a significant correlation (P < 0.001) between the activities of glycerol phosphate acyltransferase and monoacylglycerol acyltransferase in individual rats. Both of these activities were highest in the group fed on the high-starch diet and both correlated with the consumption of glucose by individual rats in the four groups. 5. The percentage of glycerol phosphate converted into diacylglycerol and triacylglycerol was positively correlated with the mean diameters, surface area and triacylglycerol content of the adipocytes for individual rats and was greates in the sucrose-fed rats. 6. The specific activity of dihydroxyacetone phosphate acyltransferase was highest in the rats fed on beef tallow. This activity was positively correlated with the energy intake for all dietary groups over the 5-week feeding period. 7. The results are discussed in terms of the functions of the three routes of glycerolipid synthesis in adipose tissue.

scholarly journals Rat epididymal adipose tissue acetyl-CoA carboxylase

1970 ◽  
Vol 48 (8) ◽  
pp. 915-921 ◽  
Author(s):  
P. R. Desjardins ◽  
K. Dakshinamurti
Keyword(s):  
Adipose Tissue ◽  
Epididymal Adipose Tissue ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
Epididymal Fat ◽  
Ph Dependent ◽  
Rat Adipose Tissue ◽  
Cold Inactivation ◽  
Fat Pads

The properties of a partially purified acetyl-CoA carboxylase (acetyl-CoA:CO2 ligase (ADP), EC 6.4.1.2) from rat epididymal fat pads have been studied. The properties of the rat adipose tissue enzyme are similar to those of the liver in regard to the pH optimum and affinity for substrates and inhibitors. The rat adipose tissue carboxylase shows a pH-dependent, reversible cold inactivation.

scholarly journals Evidence that insulin activates casein kinase 2 in rat epididymal fat-cells and that this may result in the increased phosphorylation of an acid-soluble 22 kDa protein

1991 ◽  
Vol 279 (2) ◽  
pp. 545-551 ◽  
Author(s):  
T A Diggle ◽  
C Schmitz-Peiffer ◽  
A C Borthwick ◽  
G I Welsh ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Casein Kinase ◽  
Casein Kinase 2 ◽  
Fat Cells ◽  
Isolated Fat Cells ◽  
Peptide Substrate ◽  
Heat Stable ◽  
Epididymal Fat ◽  
Rat Adipose Tissue ◽  
Fat Pads

Casein kinase 2 activity as measured by phosphorylation of the peptide substrate Arg-Arg-Arg-Glu-Glu-Glu-Thr-Glu-Glu-Glu is increased by about 50% in extracts from insulin-treated epididymal fat-pads or isolated fat-cells after purification by Mono Q chromatography. Insulin acts to increase the Vmax. of the kinase. An acid-soluble protein with an apparent subunit molecular mass of about 22 kDa appears to be a substrate for casein kinase 2. The protein possesses a number of properties in common with the acid-soluble heat-stable 22 kDa protein which exhibits increased phosphorylation in rat adipose tissue exposed to insulin.

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.

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.

Factors Affecting the Inactivation of Insulin-125I by Rat Adipose Tissue

1971 ◽  
Vol 49 (5) ◽  
pp. 457-463 ◽  
Author(s):  
Alfred Fessler ◽  
Bernard Rubinstein ◽  
David Rubinstein ◽  
John C. Beck
Keyword(s):  
Adipose Tissue ◽  
Free Fraction ◽  
Tissue Homogenate ◽  
Immunoreactive Insulin ◽  
Insulin Degradation ◽  
Factors Affecting ◽  
Free Iodine ◽  
Tissue Homogenates ◽  
Rat Adipose Tissue ◽  
Tissue Fraction

The degradation of insulin-125I by adipose tissue was determined by the appearance of 125I in the trichloroacetic acid (TCA) soluble tissue fraction. A maximum of 30% of the 125I appears as TCA-soluble material following incubation with adipose tissue homogenates. Destruction of immunoreactive insulin and insulin-like activities is, however, complete. The appearance of TCA-soluble 125I is due to proteolysis rather than to deiodination since it can be decreased by the addition of unlabelled insulin to the incubation mixture. No increase in free iodine could be detected. The degradation of insulin by intact adipose tissue is greater than by free adipocytes. Tissue homogenization greatly increases the rate of insulin degradation. Most of the insulin-degrading activity is found in the "fat-free" fraction of the tissue homogenate, but this activity is rapidly lost during incubation at 37 °C. In contrast the lesser activity in the fat layer remains stable at 37°. N-Ethylmaleimide, which inhibits breakdown of the hormone by homogenates, increases the degradation of insulin by adipocytes. These results indicate that caution must be employed in interpreting binding and destruction of iodinated insulin and raise the possibility that insulin may penetrate the cell prior to its destruction.

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 Regulation of fructose 2,6-bisphosphate concentration in white adipose tissue

1985 ◽  
Vol 225 (2) ◽  
pp. 421-428 ◽  
Author(s):  
M H Rider ◽  
L Hue
Keyword(s):  
Adipose Tissue ◽  
White Adipose Tissue ◽  
Insulin Treatment ◽  
Lactate Production ◽  
Diabetic Rats ◽  
Epididymal Fat ◽  
Lactate Output ◽  
Concentration Changes ◽  
Dose Dependent ◽  
Fat Pads

Injection of insulin to fed rats diminished the concentration of fructose 2,6-bisphosphate in white adipose tissue. Incubation of epididymal fat-pads or adipocytes with insulin stimulated lactate release and sugar detritiation and also decreased fructose 2,6-bisphosphate concentration. Such a decrease was, however, not observed in fat-pads from starved or alloxan-diabetic rats. Incubation of adipocytes from fed rats with various concentrations of glucose or fructose led to a dose-dependent rise in fructose 2,6-bisphosphate which correlated with lactate output and detritiation of 3-3H-labelled sugar. In adipocytes from fed rats, palmitate stimulated the detritiation of [3-3H]glucose without affecting lactate production and fructose 2,6-bisphosphate concentration. Incubation of epididymal fat-pads from fed rats in the presence of antimycin stimulated lactate output but decreased fructose 2,6-bisphosphate concentration. Changes in lipolytic rates brought about by noradrenaline, insulin, adenosine and corticotropin in adipocytes from fed rats were not related to changes in fructose 2,6-bisphosphate or to rates of lactate output. In fed rats, the activity of 6-phosphofructo-2-kinase was not changed after treatment of adipocytes with insulin, noradrenaline or adenosine. It is suggested that the decrease in fructose 2,6-bisphosphate concentration observed after insulin treatment can be explained by the increase in sn-glycerol 3-phosphate, an inhibitor of 6-phosphofructo-2-kinase.

scholarly journals Effects of glucose-containing peritoneal-dialysis solutions on rates of lipogenesis in vivo in the liver, brown and white adipose tissue of chronic uraemic rats

1983 ◽  
Vol 214 (2) ◽  
pp. 459-464 ◽  
Author(s):  
R A Klim ◽  
D H Williamson
Keyword(s):  
Adipose Tissue ◽  
Peritoneal Dialysis ◽  
Food Intake ◽  
Plasma Insulin ◽  
Interscapular Brown Adipose Tissue ◽  
Epididymal Fat ◽  
Dialysis Solution ◽  
Brown Adipose ◽  
Peritoneal Dialysis Solution ◽  
Fat Pads

Chronic uraemic rats had decreased food intake, and this was accompanied by decreased weight of the epididymal fat-pads and interscapular brown adipose tissue. Normal rats whose food intake was restricted to an amount similar to that of the uraemic rats showed similar decreases in weight of the adipose-tissue depots. In addition, the food-restricted rats had decreased liver weight compared with normal or uraemic rats. The basal rate of lipogenesis was decreased in liver and epididymal fat-pads of food-restricted and uraemic rats and in interscapular brown adipose tissue of uraemic rats. Administration of a low-glucose-containing (1.36%) peritoneal-dialysis solution slightly increased lipogenesis in liver of uraemic rats, but had no significant effect in epididymal fat-pads. For brown fat, the rate of lipogenesis was increased in normal, food-restricted and uraemic groups, but the values for the last group were 4-5-fold lower than for the food-restricted or control groups. A high-glucose-containing (3.86%) peritoneal-dialysis solution gave similar rates of lipogenesis in liver, epididymal fat-pads and brown fat of all three groups, but for brown fat moderately uraemic rats showed a considerably lower rate of lipogenesis than did mildly uraemic rats. The basal plasma insulin concentration was lower in the food-restricted (50%) and uraemic (70%) groups than in the control group. The low-glucose peritoneal-dialysis solution increased plasma insulin to control values in the food-restricted rats, but had no significant effect on plasma insulin in the uraemic rats, despite a significant increase in blood glucose in this group. It is concluded that there is an impairment of the lipogenic response to intraperitoneal glucose loads in interscapular brown adipose tissue of uraemic rats, and that this is not due to the accompanying decrease in food intake. The hypoinsulinaemia may be an important factor. The possible relevance of this finding to the obesity observed in some uraemic patients treated by peritoneal dialysis with glucose-containing solutions is discussed.

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