scholarly journals Insulin-like activity of proteases. VIII. Stimulation of lipogenesis and pyruvate dehydrogenase and suppression of epinephrine-sensitive lipolysis in rat epididymal adipose tissue by an N-succinyl-L-trialanine p-nitroanilide-hydrolyzing protease from Pronase.

1984 ◽  
Vol 32 (11) ◽  
pp. 4539-4544
Author(s):  
HIROSHI UEKI ◽  
YUKO MATSUNAMI ◽  
AIICHIRO MOTOSHIMA ◽  
TAKAYUKI FUNAKOSHI ◽  
SHOZO SHOJI ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Epididymal Adipose Tissue ◽  
Stimulation Of ◽  
Insulin Like Activity

Insulin activates Pyruvate Dehydrogenase in Rat Epididymal Adipose Tissue

1971 ◽  
Vol 231 (21) ◽  
pp. 115-116 ◽  
Author(s):  
R. M. DENTON ◽  
H. G. COORE ◽  
B. R. MARTIN ◽  
P. J. RANDLE
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Epididymal Adipose Tissue

scholarly journals Role of calcium ions in the regulation of intramitochondrial metabolism. Properties of the Ca2+-sensitive dehydrogenases within intact uncoupled mitochondria from the white and brown adipose tissue of the rat

1980 ◽  
Vol 190 (1) ◽  
pp. 95-105 ◽  
Author(s):  
J G McCormack ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Epididymal Adipose Tissue ◽  
Ionophore A23187 ◽  
Mitochondrial Inner Membrane ◽  
Brown Adipose ◽  
Oxoglutarate Dehydrogenase

1. Increasing concentrations of both Ca2+ and Sr2+ (generated by using EGTA buffers) resulted in 4-fold increases in the initial activity of pyruvate dehydrogenase within intact uncoupled mitochondria from rat epididymal adipose tissue incubated in the presence of the ionophore A23187, ATP, Mg2+ and oligomycin. The k0.5 values (concentrations required for half-maximal effects) for Ca2+ and Sr2+ were 0.54 and 7.1 microM respectively. In extracts of the mitochondria, pyruvate dehydrogenase phosphate phosphatase activity was stimulated about 4-fold by Ca2+ and Sr2+, with k0.5 values of 1.08 and 6.4 microM respectively. 2. NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase appeared to be rate-limiting in the oxidation of threo-Ds-isocitrate and oxoglutarate by uncoupled mitochondria from brown adipose tissue of cold-adapted rats. Ca2+ (and Sr2+) diminished the Km for the oxidation of both threo-Ds-isocitrate and oxoglutarate. The kinetic constants for these oxidations were very similar to those obtained for the activities of NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of the mitochondria. In particular, the k0.5 values for Ca2+ were all in the range 0.2–1.6 microM and Sr2+ was found to mimic Ca2+, but with k0.5 values about 10 times greater. 3. Overall, the results of this study demonstrate that the activities of pyruvate dehydrogenase, NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase may all be increased by Ca2+ and Sr2+ within intact mitochondria. In all cases the k0.5 values are close to 1 and 10 microM respectively, as found for the separated enzymes. Experiments on brown-adipose-tissue mitochondria incubated in the presence of albumin suggest that it may be possible to use the sensitivity of the dehydrogenases to Ca2+ as a means of assessing the distribution of Ca2+ across the mitochondrial inner membrane.

scholarly journals Pyruvate Dehydrogenase Activity in the Liver, Brain and Adipose-Tissue of Lipid-Deprived Developing Rats. Effect of Minute Amounts of Polyunsaturated Fatty Acids

1982 ◽  
Vol 9 (2) ◽  
pp. 221-229 ◽  
Author(s):  
C. Loriette ◽  
M. Launay ◽  
D. Lapous ◽  
J. Raulin
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Tetraenoic Acid ◽  
Female Progeny ◽  
Adipose Tissues ◽  
Minute Amount ◽  
Acid Ratio ◽  
The Brain ◽  
Stimulation Of

ABSTRACT:The present experiment was carried out using the following diets:FF, fat-free, andLPthe same diet with 0.7% sunflower oil - given to the progeny of females kept on theFFdiet since the mating. After 10 mM Mg2+ activation of the PDH phosphatase, the rate of [1-14C] pyruvate decarboxylation into acetyl-CoA ester units was determined in the liver, brain and adipose-tissue of the pair-fed developing rats.Results: In the male progeny, pyruvate dehydrogenase (PDH) activity was higher (61%) in theLPgroup livers than in theFFgroup livers, at the end of the 13 week experiment. Such a difference was not observed in the two group brains up to the 91 days postweaning, but was even larger (94%) between adipose-tissues of theLPandFFgroups. In the female progeny kept 12 weeks on the diets, PDH activity in theLPgroup tissues was also higher than in theFFgroup tissues: 63% in the liver, 43% in adipose-tissues, and less than 10% in the brain. Therefore, a minute amount of lipids high in linoleic acid appeared to increase PDH activity, and especially in the liver and adipose-tissues of animals kept on a strictly fat-free diet. This stimulation of the PDH activity seems closely related to the phospholipid rehabilitation in the tissues (decrease in the trienoic: tetraenoic acid ratio values).

PANCREATIC AND SERUM INSULIN IN THE NEW ZEALAND STRAIN OF OBESE MICE

1964 ◽  
Vol 28 (2) ◽  
pp. 163-172 ◽  
Author(s):  
J. G. T. SNEYD
Keyword(s):  
Adipose Tissue ◽  
New Zealand ◽  
Glucose Uptake ◽  
Serum Insulin ◽  
Porcine Insulin ◽  
Equivalent Amount ◽  
Obese Mice ◽  
Normal Controls ◽  
Stimulation Of ◽  
Insulin Like Activity

SUMMARY The insulin content of the pancreas and the insulin-like activity of the blood serum are considerably higher in mice of the New Zealand obese strain than in normal controls. The rate of glucose uptake by adipose tissue and hemi-diaphragms incubated in the absence of added insulin did not differ significantly in tissues from obese and normal mice and the stimulation of glucose uptake caused by addition of insulin was similar in tissues from the two strains. Insulin extracted from the pancreas of New Zealand obese mice stimulated glucose uptake by adipose tissue and muscle from obese mice to the same extent as an equivalent amount of porcine insulin.

scholarly journals Use of toluene-permeabilized mitochondria to study the regulation of adipose tissue pyruvate dehydrogenase in situ. Further evidence that insulin acts through stimulation of pyruvate dehydrogenase phosphate phosphatase

1986 ◽  
Vol 238 (1) ◽  
pp. 93-101 ◽  
Author(s):  
A P Thomas ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Phosphatase Activity ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Kinase ◽  
Epididymal Adipose Tissue ◽  
Ionophore A23187 ◽  
Dilute Suspensions ◽  
Dehydrogenase System ◽  
Pyruvate Dehydrogenase Phosphatase

Rat epididymal-adipose-tissue mitochondria were made selectively permeable to small molecules without the loss of matrix enzymes by treating the mitochondria with toluene under controlled conditions. With this preparation the entire pyruvate dehydrogenase system was shown to be retained within the mitochondrial matrix and to retain its normal catalytic activity. By using dilute suspensions of these permeabilized mitochondria maintained in the cuvette of a spectrophotometer, it was possible to monitor changes of pyruvate dehydrogenase activity continuously while the activities of the interconverting kinase and phosphatase could be independently manipulated. Permeabilized mitochondria were prepared from control and insulin-treated adipose tissue, and the properties of both the pyruvate dehydrogenase kinase and the phosphatase were compared in situ. No difference in kinase activity was detected, but increases in phosphatase activity were observed in permeabilized mitochondria from insulin-treated tissue. Further studies showed that the main effect of insulin treatment was a decrease in the apparent Ka of the phosphatase for Mg2+, in agreement with earlier studies with mitochondria made permeable to Mg2+ by using the ionophore A23187 [Thomas, Diggle & Denton (1986) Biochem. J. 238, 83-91]. No effects of spermine were detected, although spermine diminishes the Ka of purified phosphatase preparations for Mg2+. Since effects of insulin on pyruvate dehydrogenase phosphatase activity are not evident in mitochondrial extracts, it is concluded that insulin may act by altering some high-Mr component which interacts with the pyruvate dehydrogenase system within intact or permeabilized mitochondria, but not when the mitochondrial membranes are disrupted.

Does hyperinsulinemia in ob/ob mice cause an insulin-stimulated adipose tissue?

1976 ◽  
Vol 230 (3) ◽  
pp. 602-607 ◽  
Author(s):  
EG Loten ◽  
Y Le Marchand ◽  
F Assimacopoulos-Jeannet ◽  
RM Denton ◽  
B Jeanrenaud
Keyword(s):  
Adipose Tissue ◽  
Glucose Metabolism ◽  
Pyruvate Dehydrogenase ◽  
Serum Insulin ◽  
Acetyl Coa Carboxylase ◽  
Obese Mice ◽  
Lipogenic Enzymes ◽  
Insulin Stimulation ◽  
Endogenous Insulin ◽  
Stimulation Of

After a 1-h preincubation to remove endogenous insulin, adipose tissue of obese mice (C57BL/L4 ob/ob) had a lower rate of glucose metabolism than tissue which was not preincubated. In contrast, preincubation did not change the metabolism of adipose tissue from lean mice (C57B1/6J +/+). The preincubation effect was abolished in obese mice which had had their serum insulin levels lowered toward normal by streptozotocin treatment. Injection of anti-insulin serum to obese mice caused adipose tissue removed 15 min after the injection to display a rate of glucose metabolsim lower than that of tissue removed before the injection. No such effect was seen in lean mice. These data are consistent with the hypothesis that hyperinsulinemia in the obese mice causes a chronic state of insulin stimulation of their adipose tissue, possibly contributing to their high rates of lipogenesis and their obesity. Several lipogenic enzymes were measured in adipose tissue of both lean and obese mice, and no single enzymatic abnormality was detected which might explain the hyperlipogenesis. Pyruvate dehydrogenase and acetyl-CoA carboxylase were both insulin-sensitive enzymes in lean and obese mice.

scholarly journals Role of Ca2+ ions in the regulation of intramitochondrial metabolism in rat epididymal adipose tissue. Evidence against a role for Ca2+ in the activation of pyruvate dehydrogenase by insulin

1984 ◽  
Vol 218 (1) ◽  
pp. 249-260 ◽  
Author(s):  
S E Marshall ◽  
J G McCormack ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Active Form ◽  
Ruthenium Red ◽  
Epididymal Adipose Tissue ◽  
High Concentration ◽  
Fat Cell ◽  
Mitochondrial Inner Membrane ◽  
Oxoglutarate Dehydrogenase

The sensitivity of rat epididymal-adipose-tissue pyruvate dehydrogenase phosphate phosphatase, NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase to Ca2+ ions was studied both in mitochondrial extracts and within intact coupled mitochondria. It is concluded that all three enzymes may be activated by increases in the intramitochondrial concentration of Ca2+ and that the distribution of Ca2+ across the mitochondrial inner membrane is determined, as in rat heart mitochondria, by the relative activities of a uniporter (which transports Ca2+ into mitochondria and is inhibited by Mg2+ and Ruthenium Red) and an antiporter (which allows Ca2+ to leave mitochondria in exchange for Na+ and is inhibited by diltiazem). Previous studies with incubated fat-cell mitochondria have indicated that the increases in the amount of active non-phosphorylated pyruvate dehydrogenase in rat epididymal tissue exposed to insulin are the result of activation of pyruvate dehydrogenase phosphate phosphatase. In the present studies, no changes in the activity of the phosphatase were found in extracts of mitochondria, and thus it seemed likely that insulin altered the intramitochondrial concentration of some effector of the phosphatase. Incubation of rat epididymal adipose tissue with medium containing a high concentration of CaCl2 (5mM) was found to increase the active form of pyruvate dehydrogenase to much the same extent as insulin. However, the increases caused by high [Ca2+] in the medium were blocked by Ruthenium Red, whereas those caused by insulin were not. Moreover, whereas the increases resulting from both treatments persisted during the preparation of mitochondria and their subsequent incubation in the absence of Na+, only the increases caused by treatment of the tissue with insulin persisted when the mitochondria were incubated in the presence of Na+ under conditions where the mitochondria are largely depleted of Ca2+. It is concluded that insulin does not act by increasing the intramitochondrial concentration of Ca2+. This conclusion was supported by finding no increases in the activities of the other two Ca2+-responsive intramitochondrial enzymes (NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase) in mitochondria prepared from insulin-treated tissue compared with controls.

scholarly journals Activation of pyruvate dehydrogenase in adipose tissue by insulin. Evidence for an effect of insulin on pyruvate dehydrogenase phosphate phosphatase

1975 ◽  
Vol 148 (2) ◽  
pp. 229-235 ◽  
Author(s):  
C Mukherjee ◽  
R L Jungas
Keyword(s):  
Creatine Kinase ◽  
Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Insulin Treatment ◽  
Creatine Phosphate ◽  
Epididymal Adipose Tissue ◽  
Crude Extracts ◽  
Rate Of Increase

1. The mechanism by which insulin activates pyruvate dehydrogenase in rat epididymal adipose tissue was further investigated. 2. When crude extracts, prepared from tissue segments previously exposed to insulin (2m-i.u/ml) for 2min, were supplemented with Mg-2+, Ca-2+, glucose and hexokinase and incubated at 30 degrees C, they displayed an enhanced rate of increase in pyruvate dehydrogenase activity compared with control extracts. 3. When similar extracts were instead supplemented with fluoride, ADP, creatine phosphate and creatine kinase, the rate of decrease in pyruvate dehydrogenase activity observed during incubation at 30 degrees C was unaffected by insulin treatment. 4. It is suggested that insulin increases the fraction of pyruvate dehydrogenase present in the tissue in the active dephospho form by increasing the activity of pyruvate dehydrogenase phosphate phosphatase.

scholarly journals Sensitivity of pyruvate dehydrogenase phosphate phosphatase to magnesium ions. Similar effects of spermine and insulin

1986 ◽  
Vol 238 (1) ◽  
pp. 83-91 ◽  
Author(s):  
A P Thomas ◽  
T A Diggle ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Major Effect ◽  
Maximum Activity ◽  
Close Similarity ◽  
Epididymal Adipose Tissue ◽  
Kinetic Properties ◽  
Ionophore A23187 ◽  
Magnesium Ions ◽  
Dehydrogenase System

The effects of Mg2+ on the activity of pyruvate dehydrogenase phosphate phosphatase within intact mitochondria prepared from control and insulin-treated rat epididymal adipose tissue was explored by incubating the mitochondria in medium containing the ionophore A23187. The apparent Ka for Mg2+ was approximately halved in the mitochondria derived from insulin-treated tissue in both the absence and the presence of Ca2+. In this system, the major effect of Ca2+ was also to decrease the apparent Ka for Mg2+, rather than to change the Vmax. of the phosphatase. Damuni, Humphreys & Reed [(1984) Biochem. Biophys. Res. Commun. 124, 95-99] have reported that spermine activates ox kidney pyruvate dehydrogenase phosphate phosphatase. Studies were carried out on phosphatase from pig heart and rat epididymal adipose tissue which confirm and extend this observation. The major effect of spermine is shown to be a decrease in the Ka for Mg2+, which is apparent in both the presence and the absence of Ca2+. Spermine did not affect the sensitivity of the phosphatase to Ca2+ at saturating concentrations of Mg2+. Other polyamines tested were not as effective as spermine. No alteration in the maximum activity or Mg2+-sensitivity of pyruvate dehydrogenase phosphate phosphatase was apparent in extracts of mitochondria from insulin-treated tissue. The close similarity of the effects of spermine and the changes in kinetic properties of pyruvate dehydrogenase phosphate phosphatase within mitochondria from insulin-treated adipose tissue suggests that insulin may activate pyruvate dehydrogenase by increasing the concentration of spermine within the mitochondria. However, it is concluded that insulin is more likely to alter the interaction of the pyruvate dehydrogenase system with some other polybasic intramitochondrial component whose action can be mimicked by spermine.

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