scholarly journals Forms of lipoprotein lipase in rat tissues: in adipose tissue the proportion of inactive lipase increases on fasting

1996 ◽  
Vol 313 (3) ◽  
pp. 893-898 ◽  
Author(s):  
Martin BERGÖ ◽  
Gunilla OLIVECRONA ◽  
Thomas OLIVECRONA
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Translational Regulation ◽  
Specific Activity ◽  
Catalytic Efficiency ◽  
Rat Tissues ◽  
Tissue Extracts ◽  
Significant Difference ◽  
Lpl Mass ◽  
Fasted Rats

Previous studies have shown that the ratio of lipoprotein lipase (LPL) catalytic activity to LPL mass in tissues differs in different conditions, but it is not clear whether this occurs by a change in the catalytic efficiency of the LPL molecules, or because of a shift in the relation between active and inactive forms of the enzyme. To explore this, we have measured LPL activity and mass in detergent extracts of rat tissues. LPL specific activity was high and similar in heart, skeletal muscle, lung and brain. The liver had significantly lower specific activity, which is in accord with previous findings that the liver takes up and catabolizes LPL. The specific activity was also low in adipose tissue from fasted rats. When tissue extracts were applied to columns of heparin–agarose and eluted by a gradient of NaCl, a peak of active LPL was eluted at 1.0 M NaCl, but there was also a peak of inactive LPL protein, which was eluted at 0.6 M NaCl. In adipose tissue, LPL activity decreased by 70–80% during an overnight fast, whereas LPL mass decreased by only 20–40%. The mass ratio between inactive and active LPL, as separated by heparin–agarose chromatography, increased from 0.5 to over 2 during the fast. In hearts there was no significant difference between fed and fasted rats in total LPL activity, LPL mass or in the distribution between inactive and active forms. The results indicate that the relation between inactive (probably monomeric) and active (dimeric) forms of LPL is a target for post-translational regulation in adipose tissue.

scholarly journals Post-translational regulation of lipoprotein lipase activity in adipose tissue

1978 ◽  
Vol 176 (3) ◽  
pp. 865-872 ◽  
Author(s):  
P Ashby ◽  
D P Bennett ◽  
I M Spencer ◽  
D S Robinson
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Translational Regulation ◽  
Progressive Increase ◽  
Lipoprotein Lipase Activity ◽  
Dependent Part ◽  
Adipose Tissue Lipoprotein Lipase ◽  
Energy Dependent

Changes in adipose-tissue lipoprotein lipase activity that are independent of protein synthesis were investigated in an incubation system in vitro. Under appropriate conditions at 25 degrees C a progressive increase in the enzyme activity occurs that is energy-dependent. Part of the enzyme is rapidly inactivated when the tissue is incubated with adrenaline or adrenaline plus theophylline. The mechanism of this inactivation appears to be distinct from, and to follow, the activation of the enzyme. A hypothesis is presented to account for the results in terms of an activation of the enzyme during obligatory post-translational processing and a catecholamine-regulated inactivation of the enzyme as an alternative to secretion from the adipocyte.

scholarly journals Effects of Physiological Hypercortisolemia on the Regulation of Lipolysis in Subcutaneous Adipose Tissue1

1998 ◽  
Vol 83 (2) ◽  
pp. 626-631 ◽  
Author(s):  
Jaswinder S. Samra ◽  
Mo L. Clark ◽  
Sandy M. Humphreys ◽  
Ian A. MacDonald ◽  
Peter A. Bannister ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Sodium Succinate ◽  
Hormone Sensitive Lipase ◽  
Whole Body ◽  
Constant Infusion ◽  
Nonesterified Fatty Acid ◽  
Significant Difference ◽  
Hormone Sensitive ◽  
Subcutaneous Adipose

Cortisol is known to increase whole body lipolysis, yet chronic hypercortisolemia results in increased fat mass. The main aim of the study was to explain these two apparently opposed observations by examining the acute effects of hypercortisolemia on lipolysis in subcutaneous adipose tissue and in the whole body. Six healthy subjects were studied on two occasions. On one occasion hydrocortisone sodium succinate was infused iv to induce hypercortisolemia (mean plasma cortisol concentrations, 1500 ± 100 vs. 335± 25 nmol/L; P < 0.001); on the other occasion (control study) no intervention was made. Lipolysis in the sc adipose tissue of the anterior abdominal wall was studied by measurement of arterio-venous differences, and lipolysis in the whole body was studied by constant infusion of[ 1,2,3-2H5]glycerol for measurement of the systemic glycerol appearance rate. Hypercortisolemia led to significantly increased arterialized plasma nonesterified fatty acid (NEFA; P < 0.01) and blood glycerol concentrations (P < 0.05), with an increase in systemic glycerol appearance (P < 0.05). However, in sc abdominal adipose tissue, hypercortisolemia decreased veno-arterialized differences for NEFA (P < 0.05) and reduced NEFA efflux (P < 0.05). This reduction was attributable to decreased intracellular lipolysis (P < 0.05), reflecting decreased hormone-sensitive lipase action in this adipose depot. Hypercortisolemia caused a reduction in arterialized plasma TAG concentrations (P < 0.05), but without a significant change in the local extraction of TAG (presumed to reflect the action of adipose tissue lipoprotein lipase). There was no significant difference in plasma insulin concentrations between the control and hypercortisolemia study. Site-specific regulation of the enzymes of intracellular lipolysis (hormone-sensitive lipase) and intravascular lipolysis (lipoprotein lipase) may explain the ability of acute cortisol treatment to increase systemic glycerol and NEFA appearance rates while chronically promoting net central fat deposition.

Diurnal rhythms and effects of fasting and refeeding on rat adipose tissue lipoprotein lipase

1996 ◽  
Vol 271 (6) ◽  
pp. E1092-E1097 ◽  
Author(s):  
M. Bergo ◽  
G. Olivecrona ◽  
T. Olivecrona
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Specific Activity ◽  
Early Morning ◽  
Diurnal Rhythms ◽  
Mrna Levels ◽  
Short Term ◽  
Early Afternoon ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase

The activity of lipoprotein lipase (LPL) in adipose tissue is modulated by changes in the nutritional status. We have measured LPL activity, mass, and mRNA levels in rat adipose tissue during normal feeding cycles, during short- and long-term fasting, and during refeeding after fasting. LPL activity displayed a diurnal rhythm. The activity was highest during the night and early morning, decreased to a minimum during the early afternoon, and then increased again. These changes corresponded to the feeding pattern. The increases and/or decreases resulted from changes in LPL synthetic rate compounded by posttranslational mechanisms. During short-term fasting, LPL specific activity decreased to < 30% of control. The specific activity was restored within 4 h by refeeding. On longer fasting, LPL mRNA decreased. This became significant from 36 h. On refeeding, it took 12 h to restore the mRNA levels, whereas tissue LPL activity and mass could not be fully restored by 36 h of refeeding. These data show that LPL activity during short-term fasting is regulated posttranscriptionally, which allows for quick upregulation after refeeding. On longer fasting, other mechanisms affecting LPL transcription and synthesis come into play, and upregulation after refeeding is slowed down.

scholarly journals Effects of glucose and insulin on the activation of lipoprotin lipase and on protein-synthesis in rat adipose tissue

1980 ◽  
Vol 188 (1) ◽  
pp. 193-199 ◽  
Author(s):  
S M Parkin ◽  
K Walker ◽  
P Ashby ◽  
D S Robinson
Keyword(s):  
Protein Synthesis ◽  
Enzyme Activity ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Specific Activity ◽  
The Other ◽  
Lipoprotein Lipase Activity ◽  
Fat Bodies ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase

Glucose, and certain sugars that can readily be converted to glucose 6-phosphate, bring about an activation of adipose-tissue lipoprotein lipase when epididymal fat-bodies from starved rats are incubated in the presence of cycloheximide. Other substrates do not support the activation. If the tissue is preincubated in the presence of cycloheximide for longer than 2h, the ability of added glucose to activate the enzyme is lost. On the other hand, the addition of glucose still brings about an increase in lipoprotein lipase activity after preincubation in the absence of cycloheximide for as long as 4h. The magnitude of the increase in enzyme activity brought about by the addition of glucose is increased when protein synthesis is stimulated during the preincubation period by insulin. The results are interpreted in terms of the existence in adipose tissue of a proenzyme pool of lipoprotein lipase that is normally maintained by protein synthesis and that is converted to complete enzyme of higher specific activity by a process that specifically requires glucose.

scholarly journals Immunochemical studies with soluble and mitochondrial pyruvate carboxylase activities from rat tissues

1970 ◽  
Vol 119 (4) ◽  
pp. 735-742 ◽  
Author(s):  
F. J. Ballard ◽  
R. W. Hanson ◽  
Lea Reshef
Keyword(s):  
Adipose Tissue ◽  
Mammary Gland ◽  
Brown Adipose Tissue ◽  
Rat Liver ◽  
White Adipose Tissue ◽  
Pyruvate Carboxylase ◽  
Specific Activity ◽  
Rat Liver Mitochondria ◽  
Rat Tissues ◽  
Brown Adipose

1. Pyruvate carboxylase (EC 6.4.1.1), purified from rat liver mitochondria to a specific activity of 14 units/mg, was used for the preparation of antibodies in rabbits. 2. Tissue distribution studies showed that pyruvate carboxylase was present in all rat tissues that were tested, with considerable activities both in gluconeogenic tissues such as liver and kidney and in tissues with high rates of lipogenesis such as white adipose tissue, brown adipose tissue, adrenal gland and lactating mammary gland. 3. Immunochemical titration experiments with the specific antibodies showed no differences between the inactivation of pyruvate carboxylase from mitochondrial or soluble fractions of liver, kidney, mammary gland, brown adipose tissue or white adipose tissue. 4. The antibodies were relatively less effective in reactions against pyruvate carboxylase from sheep liver than against the enzyme from rat tissues. 5. Pyruvate carboxylase antibodies did not inactivate either propionyl-CoA carboxylase or acetyl-CoA carboxylase from rat liver. 6. It is concluded that pyruvate carboxylase in lipogenic tissues is similar antigenically to the enzyme in gluconeogenic tissues and that the soluble activities of pyruvate carboxylase detected in many rat tissues do not represent discrete enzymes but are the result of mitochondrial damage during tissue homogenization.

Extravascular Albumin Mass and Exchange in Rat Tissues

1970 ◽  
Vol 39 (6) ◽  
pp. 705-724 ◽  
Author(s):  
J. Katz ◽  
G. Bonorris ◽  
Sybil Golden ◽  
A. L. Sellers
Keyword(s):  
Body Weight ◽  
Ascitic Fluid ◽  
Specific Activity ◽  
The Body ◽  
Rat Tissues ◽  
Extracellular Water ◽  
Tissue Extracts ◽  
Albumin Content ◽  
Multicompartmental Analysis ◽  
Specific Activities

1. Extravascular albumin in carcass, skin and gut of rats was extracted and the albumin content estimated by several methods. Assay by electrophoresis on acrylamide gel, by immunodiffusion and by radioimmunoassay were in essential agreement. The method used previously, precipitation with antibody followed by alcohol-TCA extraction, underestimates the amount of albumin in tissue extracts, because extraction from the antibody precipitate is not complete. This method is valid, however, for specific activity determination. 2. Normal rats contain from 500 to 650 mg of albumin per 100 g body weight. Of this, 20–25% is in the circulation, 35–40% in the carcass (mainly but not exclusively muscle), 20–25% in skin and 10% in gut. 3. The extracellular water of muscle, carcass, skin and gut was estimated from the distribution of mannitol and sulphate. With the exception of gut, both methods agreed closely. Extracellular, extravascular water constitutes about 23% of the body weight of 150–200 g rats. The extracellular water in muscle is about 20% and in skin, 40%. In gut the extracellular water cannot be estimated reliably by these compounds. 4. Muscle contains about 3·5 mg/g of extravascular albumin; skin and gut, 7–8 mg/g. The concentration of extravascular albumin in extracellular water of muscle and skin is 1620 mg/ml, or 5060% of the concentration in plasma. In the small intestine the concentration of albumin is higher, possibly similar to that in plasma. 5. In rats with severe aminonucleoside nephrosis, body albumin was depleted to 100–200 mg/100 g. Of this, 15–25% was in plasma, 50% in carcass, and about 15% in skin. Ascitic fluid contained only a few mg of albumin. 6. The specific activity of extravascular albumin of tissues was followed after intravascular injection of 125I- or 131I-labelled albumin. The specific activity of carcass albumin increases rapidly, becoming equal to that in plasma after less than 2 days. The specific activity of albumin in skin increases much more slowly and becomes equal to that of plasma after 4 days. Labelling of albumin of gut is even slower. The specific activities in tissue never exceed that in plasma. 7. In severely nephrotic rats, specific activities in carcass and skin become equal to that in plasma within 2–3 days and remain equal thereafter. Specific activity of albumin in ascitic fluid increases to reach values as much as sixteen-fold those in plasma. 8. The extravascular pool, as calculated by multicompartmental analysis from the slopes and intercepts of the plasma curve, is about equal to that in plasma and in severely nephrotic rats is less than that in plasma. Discrepancies between calculated and observed extravascular albumin masses is by a factor of 3 in normal rats and 10 or more in severely nephrotic rats. 9. Specific activity of extravascular albumin as calculated from multicompartmental analysis is 1·5 times that in plasma in normal rats and at least six times that in plasma in severely nephrotic rats. Actually, the specific activities in extravascular and vascular albumin ultimately become and remain equal. 10. It is concluded that the multicompartmental model of vascular pool exchange with one or two extravascular pools is not valid for rats and probably not for other animal species.

Lipoprotein lipase: from gene to obesity

2009 ◽  
Vol 297 (2) ◽  
pp. E271-E288 ◽  
Author(s):  
Hong Wang ◽  
Robert H. Eckel
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Fatty Acids ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Insulin Action ◽  
Specific Activity ◽  
Neutral Lipids ◽  
Specific Substrate ◽  
Tissue Specific

Lipoprotein lipase (LPL) is a multifunctional enzyme produced by many tissues, including adipose tissue, cardiac and skeletal muscle, islets, and macrophages. LPL is the rate-limiting enzyme for the hydrolysis of the triglyceride (TG) core of circulating TG-rich lipoproteins, chylomicrons, and very low-density lipoproteins (VLDL). LPL-catalyzed reaction products, fatty acids, and monoacylglycerol are in part taken up by the tissues locally and processed differentially; e.g., they are stored as neutral lipids in adipose tissue, oxidized, or stored in skeletal and cardiac muscle or as cholesteryl ester and TG in macrophages. LPL is regulated at transcriptional, posttranscriptional, and posttranslational levels in a tissue-specific manner. Nutrient states and hormonal levels all have divergent effects on the regulation of LPL, and a variety of proteins that interact with LPL to regulate its tissue-specific activity have also been identified. To examine this divergent regulation further, transgenic and knockout murine models of tissue-specific LPL expression have been developed. Mice with overexpression of LPL in skeletal muscle accumulate TG in muscle, develop insulin resistance, are protected from excessive weight gain, and increase their metabolic rate in the cold. Mice with LPL deletion in skeletal muscle have reduced TG accumulation and increased insulin action on glucose transport in muscle. Ultimately, this leads to increased lipid partitioning to other tissues, insulin resistance, and obesity. Mice with LPL deletion in the heart develop hypertriglyceridemia and cardiac dysfunction. The fact that the heart depends increasingly on glucose implies that free fatty acids are not a sufficient fuel for optimal cardiac function. Overall, LPL is a fascinating enzyme that contributes in a pronounced way to normal lipoprotein metabolism, tissue-specific substrate delivery and utilization, and the many aspects of obesity and other metabolic disorders that relate to energy balance, insulin action, and body weight regulation.

scholarly journals Heterologous expression, purification and characterization of rat class theta glutathione transferase T2-2

1996 ◽  
Vol 316 (1) ◽  
pp. 131-136 ◽  
Author(s):  
Per JEMTH ◽  
Gun STENBERG ◽  
Grigoriy CHAGA ◽  
Bengt MANNERVIK
Keyword(s):  
Glutathione Transferase ◽  
Specific Activity ◽  
Catalytic Efficiency ◽  
Exchange Chromatography ◽  
Rat Tissues ◽  
Low Concentrations ◽  
Km Value ◽  
Micromolar Range ◽  
Uncatalysed Reaction

Rat glutathione transferase (GST) T2-2 of class Theta (rGST T2-2), previously known as GST 12-12 and GST Yrs-Yrs, has been heterologously expressed in Escherichia coli XL1-Blue. The corresponding cDNA was isolated from a rat hepatoma cDNA library, ligated into and expressed from the plasmid pKK-D. The sequence is the same as that of the previously reported cDNA of GST Yrs-Yrs. The enzyme was purified using ion-exchange chromatography followed by affinity chromatography with immobilized ferric ions, and the yield was approx. 200 mg from a 1 litre bacterial culture. The availability of a stable recombinant rGST T2-2 has paved the way for a more accurate characterization of the enzyme. The functional properties of the recombinant rGST T2-2 differ significantly from those reported earlier for the enzyme isolated from rat tissues. These differences probably reflect the difficulties in obtaining fully active enzyme from sources where it occurs in relatively low concentrations, which has been the case in previous studies. 1-Chloro-2,4-dinitrobenzene, a substrate often used with GSTs of classes Alpha, Mu and Pi, is a substrate also for rGST T2-2, but the specific activity is relatively low. The Km value for glutathione was determined with four different electrophiles and was found to be in the range 0.3 mM–0.8 mM. The Km values for some electrophilic substrates were found to be in the micromolar range, which is low compared with those determined for GSTs of other classes. The highest catalytic efficiency was obtained with menaphthyl sulphate, which gave a kcat/Km value of 2.3×106 s-1·M-1 and a rate enhancement over the uncatalysed reaction of 3×1010.

scholarly journals Post-transcriptional mechanisms are responsible for the reduction in lipoprotein lipase activity in cardiomyocytes from diabetic rat hearts

1995 ◽  
Vol 310 (1) ◽  
pp. 67-72 ◽  
Author(s):  
R Carroll ◽  
L Liu ◽  
D L Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Total Protein ◽  
Specific Activity ◽  
Inhibitory Effect ◽  
Diabetic Rat ◽  
Mrna Levels ◽  
Rat Hearts ◽  
Mrna Content ◽  
Enzyme Specific Activity ◽  
Lpl Mass

Lipoprotein lipase (LPL) activity is reduced in cardiomyocytes from rat hearts following the acute (4-5 day) induction of diabetes with 100 mg/kg streptozotocin. The molecular basis for this inhibitory effect of diabetes on LPL activity was investigated by measuring steady-state LPL mRNA content and the synthesis and turnover of LPL protein ([35S]methionine incorporation into immunoprecipitable LPL protein in pulse and pulse-chase experiments) in control and diabetic cardiomyocytes. LPL activity was reduced to approx. 50% of control in diabetic cardiomyocytes, but LPL mRNA levels and turnover (degradation) of newly synthesized LPL were unchanged. Synthesis of total protein and LPL were reduced to 72% and 71% of control respectively; therefore, relative rates of LPL synthesis were the same in control and diabetic cardiomyocytes. The diabetes-induced reduction in LPL synthesis was accompanied by a decrease in LPL mass to 78% of control, and a decrease in enzyme specific activity (0.48 to 0.33 m-unit/ng of LPL protein) since the decline in catalytic activity was greater than the decrease in LPL synthesis and mass. Thus, post-transcriptional mechanisms involving a reduction in LPL synthesis as part of a generalized decrease in total protein synthesis, together with a post-translational mechanism(s) that result in accumulation of inactive LPL protein, are responsible for the decreased LPL activity in cardiomyocytes from diabetic rat hearts.

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.

Sign in / Sign up

Export Citation Format

Share Document