Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.34 (lipoprotein lipase)
 7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ob17 preadipocyte clonal line has been established from the adipocyte fraction of the epididymal fat pads of adult C57 BL/6J ob/ob mice. In vivo, injection of ouabain-resistant mutant cells (ob 17OR11 cell line) into athymic mice is followed by the formation of fat pads containing ouabain-resistant mature fat cells. In vitro, ob17 cells develop after confluence biochemical and morphological characteristics of adipocytes. The adipose conversion process is best represented by a stochastic model in which a pool of stem cells (adipoblasts) give rise to clusters of adipose cells and to additional stem cells that remain in the population. The role of the different factors involved in such conversion is discussed; (1) factors that enhance the number of susceptible cells (ACF or ACF-like compounds), (2) factors without which no adipose conversion takes place (triiodothyronine, growth hormone and other factors still to be characterized), (3) factors that enhance the expression of the differentiation program (insulin). The early emergence of lipoprotein lipase occurs normally in insulin-depleted medium. The separation of ob17 cells by isopycnic centrifugation shows that lipoprotein lipase is present at high levels in early differentiating cells which are still devoid of late markers, ie glycerol-3-phosphate dehydrogenase and triglycerides. These results are discussed with respect to the determination of cellularity during development of adipose tissue in vivo.
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PMID:Adipose conversion of ob17 cells and hormone-related events. 390 48

A novel method is described for measuring the incorporation of radiolabelled amino acids into rat adipose tissue lipoprotein lipase (LPL) in vitro. Following the incubation of epididymal fat-bodies in the presence of [3H]leucine, the radiolabelled enzyme was isolated from extracts of the delipidated tissue, in a single step, by affinity chromatography on heparin-Sepharose, SDS-PAGE of such purified enzyme preparations revealed the presence of a single radiolabelled polypeptide of molecular weight 56 000, corresponding to LPL. In the presence of insulin, the rates of incorporation into LPL and into total tissue protein were increased respectively by 2.3 fold and 1.7 fold, compared to controls. It is concluded that part of the increase in incorporation into LPL is due to the general stimulus of protein synthesis in the tissue by insulin. Additionally insulin may either specifically increase the rate of synthesis or decrease the rate of degradation of the enzyme.
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PMID:The effect of insulin on the synthesis of lipoprotein lipase in rat adipose tissue. 391 May 29

Brown fat thermogenesis is increased after a single test meal. This study was conducted to determine whether lipoprotein lipase activity is higher in brown adipose and other tissues after a single large meal. Rats were trained to eat two large meals per day. Two hours after consuming a test meal, lipoprotein lipase activity was measured in interscapular brown adipose tissue, retroperitoneal and epididymal white adipose tissue, gastrocnemius and soleus skeletal muscles and heart. After a high carbohydrate test meal, lipoprotein lipase activity in white adipose tissue pads was higher (P less than 0.05) and that in brown adipose tissue was lower (P less than 0.05) than in these tissues from the meal-deprived group. Muscle lipoprotein lipase did not change significantly. A high fat test meal did not significantly alter lipoprotein lipase activity in brown adipose tissue, white adipose tissue, gastrocnemius or soleus when compared to the meal-deprived control, but heart lipoprotein lipase activity was significantly elevated. These findings indicate that after a single test meal lipoprotein lipase activity in brown adipose tissue is not higher than that from the meal-deprived group and therefore, lipoprotein lipase may not play a rate-limiting role in moving free fatty acids into this tissue in the postprandial state.
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PMID:Meal-induced changes in lipoprotein lipase activity in brown fat and other tissues of rats. 395 Jul 70

Human adipose tissue was shown to contain carboxylesterase activity when measured by methylbutyrate as substrate. The enzyme has the same characteristics as carboxylesterase purified from rat epididymal adipose tissue. Like lipoprotein lipase, carboxylesterase activity was higher in large than in small fat cells. Both cell size and carboxylesterase activity were greater in human subcutaneous than in omental adipose tissue. However, the linear regression lines between the enzyme activity and cell volume in the two tissues were almost superimposable, suggesting that cell size is a determinant of enzyme activity. Although the physiological significance of adipose tissue carboxylesterase must await further clarification, it is possible that the enzyme is related to the hydrolysis of long-chain monoacylglycerols.
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PMID:Regional differences in carboxylesterase activity between human subcutaneous and omental adipose tissue. 398 21

Tri[14C]acylglycerol-labelled chylomicrons, obtained from cannulated mesenteric lymph of streptozotocin-diabetic donor rats, when intravenously injected into non-diabetic recipient rats, disappeared from the circulation at a significantly slower rate than similarly prepared tri[14C]acylglycerol chylomicrons from non-diabetic donor rats (t1/2, 5.6 +/- 0.7 vs. 3.2 +/- 0.5 min-1, P less than 0.02). The appearance of labelled lipolysis products among plasma lipids (free fatty acid, cholesterol ester and phospholipid fractions) was delayed, indicating decreased availability for lipolysis of the chylomicron-borne triacylglycerol of diabetic origin. Tissue distribution of triacylglycerol, 15 min after the injection of chylomicrons to recipient rats, disclosed a 4-5-fold increase in uptake by muscles (heart and diaphragm) in relation to adipose tissues (epididymal and perirenal sites), in the case of chylomicrons of diabetic derivation. Since a large share of the chylomicron triacylglycerol was taken up by the liver, this tissue was perfused with chylomicron 'remnants' prepared by partial in vitro lipolysis with purified lipoprotein lipase. The 'remnants' of diabetic derivation were taken up by the liver at a 2-3-fold slower rate than those of non-diabetic origin. Chylomicrons derived from diabetic rats were found to be similar in size but markedly depleted of E apolipoproteins as determined by SDS-polyacrylamide gel electrophoresis, isoelectric focussing and a specific immunoassay. Decreases were also seen in A-I apolipoproteins by immunoassay and isoelectric focussing. Chylomicron 'remnants' were also markedly apolipoprotein E-deficient. In vitro incubation of the 'diabetic remnants' with high-density lipoproteins raised their apolipoprotein E content approx. 3-fold and considerably increased their hepatic uptake. Injection of intact chylomicrons preincubated with high-density lipoproteins likewise increased their in vivo removal rate toward the range of that of 'non-diabetic' chylomicrons. We conclude that diabetes-induced changes in the apolipoprotein composition of the chylomicrons and chylomicron remnants play an important role in their removal from the circulation. It appears that their recognition pattern is altered, reducing their ability to interact with receptor sites in the peripheral tissues and the liver, respectively.
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PMID:Composition, removal and metabolic fate of chylomicrons derived from diabetic rats. 399 73

Pulse-chase studies have shown that the lipoprotein lipase protein of rat epididymal fat bodies is apparently rapidly degraded (43% in 3 h) during incubation at 37 degrees C under conditions where little degradation of the total adipose tissue protein is taking place.
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PMID:Degradation of lipoprotein lipase in rat adipose tissue. 400 96

Mechanisms for hypercholesterolemia and hypertriglyceridemia and the effects of KCD-232, a new hypolipidemic agent, on them were studied in male Wistar rats with daunorubicin (DR)-induced nephrosis. Single intravenous injection of DR dose-dependently increased urinary protein loss and serum lipid levels (0,3,6 and 12 mg/kg). Twenty-four days after the injection of DR (6 mg/kg), serum cholesterol (Ch) and triglyceride (TG) levels markedly increased and free fatty acid level tended to decrease with no effects on liver lipid levels. Hepatic Ch synthesis from [14C]acetate in vitro increased by 2.1-fold, while exogenous Ch absorption slightly decreased. The clearance of intravenously injected [3H]Ch from the circulation was delayed. Hepatic fatty acid (FA) synthesis also increased by 2.7-fold, and hepatic TG lipase activity tended to decrease. KCD-232 improved the hypercholesterolemia and hypertriglyceridemia of DR-treated rats. The drug inhibited the elevated hepatic Ch synthesis and exogenous Ch absorption and thus improved the delayed Ch clearance from the circulation. KCD-232 markedly inhibited the elevated hepatic FA synthesis and stimulated both hepatic FA oxidation and lipoprotein lipase activity from the epididymal adipose tissue of the nephrotic rats. These results suggest that 1. DR-induced hypercholesterolemia is due to both an increased Ch synthesis in the liver and delayed clearance of Ch from the circulation; 2. DR-induced hypertriglyceridemia is caused by both an increased hepatic FA synthesis and depressed TG hydrolysis in the circulation; 3. KCD-232 improves the hypercholesterolemia by inhibiting the elevated Ch synthesis and Ch absorption from the gut; and 4. KCD-232 improves the hypertriglyceridemia by inhibiting the elevated hepatic FA synthesis and by stimulating both hepatic FA oxidation and TG hydrolysis activity in the circulation.
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PMID:[Experimental nephrotic hyperlipidemia induced in rats by daunorubicin and effects of KCD-232[4-(4'-chlorobenzyloxy)benzyl nicotinate] on lipid metabolism]. 402 7

Fasted rats injected with actinomycin or fed glucose show increased lipoprotein lipase activity of epididymal adipose tissue. Data from the actinomycin-treated animals showed a direct correlation between the lipoprotein lipase activity and the uptake of lipoprotein triglyceride by the epididymal fat pad in vitro and in vivo. Data from the animals fed glucose confirmed these findings in vitro. These data strongly suggest that lipoprotein lipase plays a major role in triglyceride deposition in adipose tissue.
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PMID:Relationship of lipoprotein lipase activity to triglyceride uptake in adipose tissue. 416 85

Sucrose gradient centrifugation has been used to examine the triglyceride lipases present in extracts of rat epididymal adipose tissue. The aqueous infranatant recovered between the pellet and fat cake of tissue homogenates which had been centrifuged at 40,000 g was shown to contain two types of triglyceride lipase activity. One of these appears in the 15s region and has been identified as the active form of the "hormone-sensitive lipase" believed to be responsible for initiating the hydrolysis of tissue triglyceride stores in response to lipolytic stimuli. The activity of this enzyme was selectively increased in extracts prepared from tissue exposed to epinephrine and decreased in extracts of insulin-treated tissue. The increased lipolytic activity of extracts of tissue from fasted or fasted-refed rats was also found largely in this region. When the tissue was incubated with orthophosphate-(32)P, radioactivity was incorporated into a protein migrating at 15s. A second peak of triglyceride lipase activity appeared in the 6s region coincident with the location of the monoglyceride and diglyceride lipase activities. The amount of 6s triglyceride lipase activity did not correlate with changes in the lipolytic activity of the tissue from which the extracts were prepared, and its physiological function remains to be elucidated. The lipoprotein lipase and the short-chain triglyceride lipase ("tributyrinase") each moved more slowly in the gradient than the 6s triglyceride lipase. Both the 6s and 15s enzymes were shown to be present in washed adipocytes isolated from the tissue by collagenase digestion.
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PMID:Studies on the hormone-sensitive lipase of adipose tissue. 432 8

1. The relationships between nutritional state, lipoprotein lipase activity in epididymal fat-pads, and the concentrations of glucose, insulin and unesterified fatty acids in the plasma were studied in rats that had been adapted for 3 weeks to one of two controlled feeding schedules. In one of these, rats had access to food for 14h during each 24h period, and in the other, they had access to food for 14h during each 48h period. Groups of animals were killed at different times during the 14h when they had access to food and during the following period when they were deprived of food. 2. Low lipoprotein lipase activity, low concentrations of plasma glucose and insulin and high concentrations of plasma unesterified fatty acids were found in rats deprived of food for 34h. Feeding resulted in increases in lipoprotein lipase activity and in the concentrations of glucose and insulin in the plasma. Enzyme activity continued to increase during the first 6-9h of the feeding period. 3. After adapted rats had been deprived of food for 12-16h there was a marked and unexpected increase in lipoprotein lipase activity; this occurred even when the rats were kept in an isolated environment. 4. The findings suggest that factors other than the absolute concentrations of insulin and glucose in the blood can exert a considerable influence on lipoprotein lipase activity in the epididymal fat-pad of a rat.
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PMID:Lipoprotein lipase activity in the adipose tissue of rats adapted to controlled feeding schedules. 508 62


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