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At least 1,351 records · Page 75Linked to original sources
PubMed1984

Separation of bovine brain mono- and diacylglycerol lipases by heparin sepharose affinity chromatography.

Mono- and diacylglycerol lipases are differentially inhibited by heparin. No other glycosaminoglycan resembles heparin in this respect. Mono- and diacylglycerol lipases can be separated by heparin Sepharose affinity chromatography. Diacylglycerol lipase was completely retained on a heparin--Sepharose column and was eluted with either 0.5 M NaCl or 2-5 mg/ml heparin, whereas monoacylglycerol lipase was recovered in the washings. Adenosine phosphates markedly affected the activity of diacylglycerol lipase in a concentration dependent manner. ATP was the most potent inhibitor followed by ADP. AMP had no effect and cAMP slightly stimulated the diacylglycerol lipase.

Adenine Nucleotides↗
PubMed1993

Effect of glutamate and its analogs on diacylglycerol and monoacylglycerol lipase activities of neuron-enriched cultures.

Neuron-enriched cultures from fetal mouse spinal cord contain diacylglycerol and monoacylglycerol lipases. The treatment of neuron-enriched cultures with glutamate or NMDA resulted in a dose- and time-dependent stimulation in diacylglycerol and monoacylglycerol lipase activities. The elevation in the activities of lipases was blocked by the NMDA receptor antagonists, dextrorphan and MK-801, suggesting that lipase stimulation is a receptor-mediated process. The treatment of neuron-enriched cultures with kainate had no effect on diacylglycerol and monoacylglycerol lipase activities. The stimulation of diacylglycerol and monoacylglycerol lipase activities by glutamate and NMDA suggests that these enzymes may play an important role in processes mediated by the NMDA type of the glutamate receptors.

Animals↗
PubMed1982

Plasma high density lipoproteins HDL2, HDL3 and postheparin plasma lipases in relation to parameters of physical fitness.

A number of studies has shown that the plasma levels of high density lipoprotein (HDL) are increased by regular aerobic exercise. The plasma HDL, particularly HDL2, is regulated by the activity of 2 endothelial lipases, viz. lipoprotein lipase (LPL) and hepatic lipase (HL), which both can be assayed in postheparin plasma. In the present study the plasma levels of HDL2 and HDL3 cholesterol and the postheparin plasma lipase activities were related to parameters of physical fitness obtained from a pulse conducted maximal bicycle ergometer test. There was a significant positive correlation between HDL2 cholesterol and physical fitness (r = 0.52, P less than 0.01). On the other hand, the postheparin plasma hepatic lipase activity showed a significant negative correlation to physical fitness (r = -0.57, P less than 0.01). The HDL2 cholesterol was inversely correlated with the HL activity (r = 0.57, P less than 0.001). Application of partial correlation analysis to the data showed that the relationship between HDL2 cholesterol and fitness disappeared by keeping the HL activity constant whereas the correlation between HDL2 and HL was not influenced by fitness. The relation of HDL2 to fitness was independent in body fat and basal plasma insulin level; in addition the relationship between HL and fitness was not accounted for by body fatness. No relationship was found between physical fitness and LPL activity or between HDL3 and fitness. The results support the hypothesis that hepatic endothelial lipase has a role in the regulation of plasma HDL2 cholesterol and that the activity of this enzyme decreases upon increase of physical fitness.

Adult↗
PubMed1988

Inhibition of myocardial lipase by palmityl CoA.

The lipase activity of the adult rat heart consists of at least two components; a lipoprotein lipase and a "hormone-sensitive" or triglyceride lipase. The control of the triglyceride lipase by intermediates of lipid metabolism was studied in rat heart homogenates. Perfusion of hearts with fatty acids, glucose or no exogenous substrate did not alter lipase activity. Bovine serum albumin (BSA) stimulated the in vitro lipase activity whereas palmityl-coenzyme A (CoA) was a potent inhibitor. Other fatty acid intermediates such as acetyl-CoA, acetyl-carnitine, palmityl-carnitine and palmitate had little or no effect. Long-chain acyl CoA may be an important intermediate for matching triglyceride hydrolysis with the supply of extracellular fatty acids and the rates of fatty acid oxidation.

Acyl Coenzyme A↗
PubMed2005

Activity and tissue-specific expression of lipases and tumor-necrosis factor alpha in lean and obese cats.

Post-heparin plasma activity of lipoprotein lipase (LPL) and hepatic lipase (HL), and fat and muscle activity of LPL were measured in neutered lean and obese cats. Lipoprotein lipase, hormone-sensitive lipase (HSL), and tumor necrosis factor a (TNF) mRNA were measured in muscle and fat tissue with real-time PCR using primers for feline LPL, HSL, and TNF. Lipoprotein lipase plasma and fat activity and fat mRNA levels were significantly lower (50, 80, and 50%, respectively) in obese cats than lean cats, whereas the muscle/fat ratio of LPL was significantly higher in obese compared to lean cats. The activity of HL was not different between the groups. Hormone-sensitive lipase mRNA levels were significantly higher in obese than lean cats. The level of fat TNF also was significantly higher in obese cats than in lean cats, whereas the level in muscle was not different. The lower LPL activity and mRNA expression in fat and the higher LPL and HSL mRNA expression in muscle in obese cats compared to lean cats expectedly favor a redistribution of fatty acids from fat to muscle tissue where they can be deposited or used for energy in times of need. Tumor necrosis factor alpha may regulate this repartitioning process through suppression of adipocyte LPL.

Adipose Tissue↗
PubMed1984

Pulmonary macrophage: a major source of lipoprotein lipase in the lung.

The lipase released by heparin infusion into perfused rat lungs is shown to be identical with lipoprotein lipase on the basis of the following characteristics: 1) it required plasma for full activity; 2) it was largely inhibited by 1 M NaCl; and 3) it bound to a heparin-Sepharose gel and eluted with buffer containing 1.5 M NaCl. Macrophages prepared from rat lungs released a considerable amount of lipoprotein lipase, with characteristics similar to those of the lipoprotein lipase released from heparin-perfused rat lungs. Pulmonary surfactant-producing type II pneumocytes did not cause a significant release of lipoprotein lipase. No apparent lipoprotein lipase activities were detected in the conditioned medium of other lung cells from which macrophages had been selectively removed.

Animals↗
PubMed1999

Plasma post-heparin lipase activities in the HERITAGE Family Study: the reproducibility, gender differences, and associations with lipoprotein levels. HEalth, RIsk factors, exercise Training and GEnetics.

OBJECTIVES: Examine the reproducibility of plasma lipid and lipoprotein measurements in the HERITAGE Family Study. DESIGN AND METHODS: In a sample of 379 subjects (191 men and 188 women), reproducibility was determined for lipids, lipoproteins (done on two occasions) and post-heparin lipase assays using an Intracenter Quality Control study by generating split samples from an additional 60 subjects (35 men and 25 women), which were assayed in a blind fashion by the lipid core laboratory. Reproducibility was estimated using intraclass correlation coefficients (ICC) for the selected variables. Analytical error (ANER) and coefficient of variation (CV) were also calculated. Day-to-day variation for 10 variables including plasma cholesterol and triglycerides (TG), HDL-cholesterol and its subfractions HDL2-cholesterol and HDL3-cholesterol, LDL-cholesterol and VLDL-cholesterol, as well as apoprotein (apo) A-I, apo B, and LDL-apo B were assessed. RESULTS: In the HERITAGE study, all lipid and lipoprotein variables had ICC above 0.79. Plasma VLDL-cholesterol (31 %) and TG (23%) levels, which are well known to be highly variable from one day to another, had CVs greater than 20%. Other variables had CVs lower than 10% except for HDL2-cholesterol which reached 16%. In the intracenter reliability sub-study, the measurement errors were found to be low except for HDL2-cholesterol. For the lipases, the reproducibility of repeated samples was very high, with ICC over 0.95. The within-assay CV corresponded to 2.1 and 5.3% for hepatic lipase (HL) and lipoprotein lipase (LPL), respectively, whereas the between-assay CV reached 8-12% for HL and about 15% for LPL. Due to the complexity of these two assays, the results are considered to be quite satisfactory. CONCLUSIONS: The reproducibility of plasma lipid and lipoprotein measurements, as well as of post-heparin lipase activities, is good in the multicenter HERITAGE Family Study. In addition, the well-documented gender difference in the plasma lipoprotein profile was confirmed in the present study, women having lower fasting triglyceride and LDL-cholesterol levels than men as well as reduced cholesterol/HDL-cholesterol and increased HDL2-cholesterol/ HDL3-cholesterol ratios compared to men. Results of the present study support the notion that the higher LPL and low HL activities found in women compared to men are important factors contributing to explain gender difference in the lipoprotein profile. However, additional factors not examined in the present study are involved beyond the contribution of post-heparin lipase to the sex dimorphism in plasma lipoprotein levels.

Female↗
PubMed1977

Characterization of two triacylglycerol lipase activities in pig post-heparin plasma.

Two triacylglycerol lipase activities were characterized after partial purification from pig post-heparin plasma. These two lipase activities were eluted sequentially with a NaCl gradient from columns containing Sepharose with covalently linked heparin. The first lipase activity, which was eluted at 0.75M-NaCl, was not inhibited at 28 degrees C in the presence of 1M-NaCl and was not further activated by plasma apolipoproteins. The absence of this lipase activity from post-heparin plasma from hepatectomized pigs indicates that the liver plays a role in the synthesis of this enzyme. A second lipase activity, which was eluted at 1.2M-NaCl, was inhibited when assayed in the presence of 1.0M-NaCl and was activated 14-fold by an apolipoprotein isolated from human very-low-density lipoprotein. The characteristics are identical with those of lipoprotein lipase purified from pig adipose tissue.

Adipose Tissue↗
PubMed2003

Exaggerated postprandial lipaemia and lower post-heparin lipoprotein lipase activity in middle-aged men.

An exaggerated postprandial lipaemic response is thought to play a central role in the development of an atherogenic lipoprotein phenotype, a recognized lipid risk factor for coronary heart disease. A small number of limited studies have compared postprandial lipaemia in subjects of varying age, but have not investigated mechanisms underlying age-associated changes in postprandial lipaemia. In order to test the hypothesis that impaired lipaemia in older subjects is associated with loss of insulin sensitivity, the present study compared the postprandial lipaemic and hormone responses for 9 h following a standard mixed meal in normolipidaemic healthy young and middle-aged men. Lipoprotein lipase (LPL) and hepatic lipase (HL) activities were determined in post-heparin plasma 9 h postprandially and on another occasion under fasting conditions. Postprandial plasma glucose (P<0.02), retinyl ester (indirect marker for chylomicron particles; P<0.005) and triacylglycerol (TAG)-rich lipoprotein (density<1.006 g/ml fraction of plasma) TAG (P<0.05) and retinyl ester (P<0.005) responses were higher in middle-aged men, whereas plasma insulin responses were lower in this group (P<0.001). Fasting and 9 h postprandial LPL and HL activities were also significantly lower in the middle-aged men compared with the young men (P<0.006). In conclusion, the higher incremental postprandial TAG response in middle-aged men than young men was attributed to the accumulation of dietary-derived TAG-rich lipoproteins (density<1.006 g/ml fraction of plasma) and occurred in the absence of marked differences in fasting TAG levels between the two groups. Fasting and postprandial LPL and HL activities were markedly lower in middle-aged men, but lack of statistical associations between measures of insulin response and post-heparin lipase activities, as well as between insulin and measures of postprandial lipaemia, suggest that this lower activity cannot be attributed to lack of sensitivity of lipases to activation by insulin. Alternatively, post-heparin lipase activities may not be good markers for the insulin-sensitive component of lipase that is activated postprandially.

Adolescent↗
PubMed1985

Regulation of lipases involved in the supply of substrate fatty acids for the heart.

Evidence is presented that all lipase activities present in the vascular and myocardial tissue from rat heart are regulated by product inhibition. Lipoprotein lipase activity, which plays a role in the uptake of circulating triglycerides, is determined by its reaction products, e.g. fatty acids and, predominantly, monoglycerides. Tissue acid and neutral lipase activities are regulated by product fatty acids and their coenzyme A (CoA) and carnitine ester derivatives. The order of potency is palmitoyl CoA approximately palmitoyl carnitine greater than palmitate for neutral lipase and palmitoyl carnitine greater than palmitoyl CoA palmitate for acid lipase activity. Product inhibition of extracellular and intracellular lipolytic processes warrants a close coupling between the supply of substrate fatty acids and the rate of fatty acid oxidation as determined by cardiac contractile activity. None of the lipases studied was directly affected by catabolic hormones (norepinephrine, glucagon) or their intracellular second messengers (cyclic AMP, protein kinase, Ca2+, calmodulin).

Animals↗
PubMed1987

Human lipoprotein lipase complementary DNA sequence.

Lipoprotein lipase is a key enzyme of lipid metabolism that acts to hydrolyze triglycerides, providing free fatty acids for cells and affecting the maturation of circulating lipoproteins. It has been proposed that the enzyme plays a role in the development of obesity and atherosclerosis. The human enzyme has been difficult to purify and its protein sequence was heretofore undetermined. A complementary DNA for human lipoprotein lipase that codes for a mature protein of 448 amino acids has now been cloned and sequenced. Analysis of the sequence indicates that human lipoprotein lipase, hepatic lipase, and pancreatic lipase are members of a gene family. Two distinct species of lipoprotein lipase messenger RNA that arise from alternative sites of 3'-terminal polyadenylation were detected in several different tissues.

Amino Acid Sequence↗
PubMed1983

Combined lipase deficiency (cld): a lethal mutation on chromosome 17 of the mouse.

Two triglyceride lipases, lipoprotein lipase and hepatic triglyceride lipase, participate in the metabolism of plasma lipoproteins. A single recessive mutation, cld, on mouse chromosome 17 causes an apparent deficiency of both lipoprotein lipase and hepatic triglyceride lipase activities. Mice homozygous for this defect develop lethal hyperchylomicronemia within 2 days postpartum as a consequence of nursing. Plasma triglyceride values in affected mice often reach 20,000 milligrams per deciliter (100 times higher than that in normal littermates), and total lipase activity in plasma or tissues is 5 to 20 percent of that in controls.

Animals↗
PubMedDate not supplied

Neutral triglyceride lipase in macrophages.

High levels of neutral triglyceride lipase activity have been demonstrated in several types of macrophages (J774 cells, human monocyte/macrophages, rabbit alveolar macrophages, and resident mouse peritoneal macrophages). The pH optima ranged from 6.5 to 7.4 depending upon the buffer and the conditions of incubation. The addition of bovine serum albumin stimulated activity at low concentrations, as expected for a fatty acid-releasing reaction, but strongly inhibited at higher concentrations; maximal activity was observed in the presence of 0.625 mg/ml of bovine serum albumin. The enzyme was remarkably thermostable, showing no apparent loss of activity at 50 degrees C for as long as 6 hours. The lipase was inhibited 80% by 0.1 M NaCl. Assayed under optimal conditions, the specific activity of the neutral triglyceride lipase from J774 cells was more than 100-fold greater than the activity of lipoprotein lipase or neutral cholesterol esterase from those cells; this activity was 10-fold greater than the levels of hormone-sensitive lipase from 3T3-L1 adipocytes. This neutral triglyceride lipase may play an important role in the degradation and mobilization of cytosolic triglyceride in macrophage-derived foam cells.

Animals↗
PubMed1984

Effect of heparin on serum and tissue lipases in the developing rat.

The frequent inclusion of heparin in fluids used for total parenteral nutrition in infants, prompted an investigation of the ability of heparin to release lipoprotein lipase (LPL) and hepatic lipase (HL) from the endothelial surface into the circulation, and of the effect of heparin on tissue stores of lipase in the postnatal period. In rat pups, plasma postheparin lipolytic activity (PHLA) released by IP administration of heparin (0.5 unit/g body wt) was 15% of adult values at birth and increased rapidly to reach 60% on day 10. Repeated doses of heparin (in adult rats, given 0.1 unit/g IV) at 1 and 4 h after the initial dose did not affect the maximal response to heparin. In all age groups 80% of PHLA was inhibited by 0.5 M NaCl, suggesting a mostly nonhepatic origin for the released enzyme. Heart, lung, and liver lipase activities of rat pups were not significantly different from controls not given heparin. The pattern of change in tissue enzyme content was similar for heart and lung, but different from hepatic lipase. LPL activity in the former increased from 10 and 30% to 60 and 100% of adult values between birth and 10 days while in the latter enzyme activity exceeded adult levels at birth and decreased to 50% of adult values during the latter half of the suckling period (days 10-21). Our results demonstrate that heparin does not cause depletion of tissue lipases in the postnatal period. The parallel increases in LPL content of peripheral tissues and PHLA suggest that in all age groups heparin-induced release of LPL into the circulation is proportional to tissue lipolytic activity.

Age Factors↗
PubMed2000

Sib-pair linkage analysis of longitudinal changes in lipoprotein risk factors and lipase genes in women twins.

Based on longitudinal twin data in women, we have previously demonstrated a genetic influence on changes in lipoprotein risk factors, blood pressure measurements, and body mass index over a decade. The present study examined the linkage between changes in lipoprotein variables and candidate genes encoding the hormone-sensitive lipase (HSL), hepatic lipase (HL), and lipoprotein lipase (LPL). The sample consisted of 126 dizygotic (DZ) pairs of women twins who participated in the two examinations of the Kaiser Permanente Women Twins Study, performed a decade apart. Using quantitative sib-pair linkage analysis, a linkage was demonstrated between the locus for hormone-sensitive lipase and age-adjusted changes in plasma triglyceride (P = 0.015), which became more significant after adjustment for environmental factors and the exam-1 level (P = 0.005). There was also evidence suggesting linkage between the locus for hepatic lipase and changes in triglyceride (P = 0.023), but no linkage was detected for lipoprotein lipase and changes of lipid levels with time. These findings suggest that variation at these candidate gene loci may underlie a portion of the intraindividual variations in these coronary heart disease (CHD) risk factors, and that studies to identify the functional variants could provide new insights into genetic susceptibility to cardiovascular disease.

Adult↗
PubMedDate not supplied

Lipoprotein lipase in experimental diabetic rats: beneficial effect of vanadate treatment.

Elevated values of circulating triglycerides were observed in streptozotocin-hyperglycemic rat while cholesterol concentrations did not differ from controls. Daily oral administration of sodium metavanadate to these diabetic animals normalized blood glucose values without raising the reduced levels of insulin. Concomitant with the normalization of the glycemia, the elevated triglyceride values found in diabetic rats were also corrected. Lipoprotein lipase activity in adipose and cardiac tissues was significantly decreased in the streptozotocin-diabetic animals. Similarly, the hepatic lipase activity was also depressed. After vanadate treatment, lipoprotein lipase as well as hepatic lipase activities were corrected towards normal values. Thus, vanadate treatment of streptozotocin-diabetic animals induces normalization of blood glucose and triglycerides levels, while maintaining low amounts of circulating insulin. It also restores the depressed activities of adipose and cardiac lipoprotein lipase and hepatic lipase.

Adipose Tissue↗
PubMed1984

Acute inhibition of hepatic lipase and increase in plasma lipoproteins after alcohol intake.

Chronic alcohol intake is associated with an increase in fasting plasma high density lipoproteins (HDL). To study alcohol's acute effects on plasma lipoproteins, we measured plasma lipoprotein concentrations and activities of postheparin plasma lipases in nine normolipemic males after ingestion of 40 g of ethanol (as whiskey). After alcohol there was no change in lipoprotein lipase activity but hepatic lipase was decreased to 67% of baseline at 6 hr. There were associated increases in HDL phospholipids (12 mg/dl) and cholesterol (10 mg/dl) resulting in prominence of larger, lipid-enriched HDL particles. Changes were most pronounced in the HDL3 and HDL2a subclasses. Very low density lipoprotein (VLDL) phospholipids and cholesterol were also increased by 13 and 9 mg/dl, respectively, with no significant change in triglycerides. Changes in lipoproteins and lipase were largely reversed 10 hr after alcohol intake. The transient increases in VLDL and HDL lipids after alcohol may result in part from acute inhibition of hepatic lipase activity. The results suggest a role of hepatic lipase in the catabolism of phospholipids of VLDL and possibly HDL.

Adult↗
PubMed1977

Hormone-sensitive lipase of adipose tissue.

Some physiologic aspects of the mobilization and fate of free fatty acids are reviewed. The molecular mechanism of the activation of hormone-sensitive lipase in adipose tissue is then discussed. Recent evidence established that hormone-sensitive lipase, concerned with fat mobilization, is both functionally and immunochemically distinct from lipoprotein lipase, concerned with uptake of plasma triglycerides. Lipoprotein lipase activity is not altered by cyclic AMP-dependent protein kinase. The latter enzyme enhances not only triglyceride hydrolase but also monoglyceride, diglyceride and cholesterol ester hydrolase activities in chicken adipose tissue. Finally, it is shown that the activation of all four acyl hydrolases is reversible, the deactivation being magnesium-dependent. Protein phosphatase fractions from heart and liver active against phosphorylase a can reversibly deactivate adipose tissue hormone-sensitive lipase, implying a low degree of substrate specificity for lipase phosphatase.

Adipose Tissue↗