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

The mRNA for human hormone-sensitive lipase (HSL) was identified using Northern blot analysis and a cDNA-probe for rat HSL. As in the rat, human adipose tissue expresses a single mRNA species of 3.3 kb. Using Western blotting with a polyclonal rabbit antibody towards rat adipose tissue HSL, the corresponding enzyme in human adipose tissue was identified with an apparent 88 kDa polypeptide, thus slightly larger than the rat and bovine 84 kDa, and the mouse and guinea-pig 82 kDa species. Additional evidence for the identification was provided by the inhibition of HSL diacylglycerol lipase activity by the anti-rat HSL antibody, and by NaF, DFP and Hg2+, known inhibitors of HSL. The concentration of the enzyme, as reflected by its activity per g tissue and the specific activity was about two thirds of that in the rat adipose tissue (200 g rats). The identification of the human enzyme protein made it possible to directly demonstrate its phosphorylation by cAMP-dependent protein kinase, thus extending the previous report regarding activation of the lipase with this kinase and ATP-Mg2+ in human adipose tissue extracts (Khoo, J.C., Aquino, A.A. and Steinberg, D. (1974) J. Clin. Invest. 53, 1124-1131).
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PMID:Human adipose tissue hormone-sensitive lipase: identification and comparison with other species. 255 74

Effects of capsaicin, a pungent principle of hot red pepper, were studied in experiments using male rats fed a diet containing 30% lard. Capsaicin was supplemented at 0.014% of the diet. The level of serum triglyceride was lower when capsaicin was present in the diet than when it was not. Levels of serum cholesterol and pre-beta-lipoprotein were not affected by the supplementation of capsaicin. The perirenal adipose tissue weight was lower when capsaicin was present in the diet than when it was not. Hepatic enzyme activities of glucose-6-phosphate dehydrogenase and adipose lipoprotein lipase were lower in rats fed the 30% lard diet than in those fed a nonpurified diet. Activities of these two enzymes were higher when capsaicin was added to the diet than when it was not. Hepatic acetyl-CoA carboxylase, beta-hydroxyacyl-CoA dehydrogenase, and adipose hormone-sensitive lipase activities were not affected by capsaicin feeding. Lipid absorption was not affected by the supplementation of capsaicin. The perirenal adipose tissue weight and serum triglyceride were decreased as the level of capsaicin in the diet increased up to 0.021%. These results suggest that capsaicin stimulates lipid mobilization from adipose tissue and lowers the perirenal adipose tissue weight and serum triglyceride concentration in lard-fed rats.
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PMID:Effects of capsaicin on lipid metabolism in rats fed a high fat diet. 287 41

Lipolysis of intracellular triglycerides in the heart has been shown to be regulated by hormones. However, activation of myocardial triglyceride lipase in a cell-free system has not been directly demonstrated. In the present studies, initial attempts to demonstrate cAMP-dependent activation of triglyceride lipase using the 1,000 X g supernatant fraction (S1) of mouse heart homogenate were unsuccessful, presumably due to the masking effects of high levels of lipoprotein lipase activity even when assayed at pH 7.4 and in the absence of apolipoprotein C-II. Myocardial lipoprotein lipase in the 40,000 X g supernatant fraction was then removed by heparin-Sepharose affinity chromatography. The lipoprotein lipase-free fractions were shown to contain neutral triglyceride lipase and neutral cholesterol esterase of about equal activities. The triglyceride lipase and cholesterol esterase activities fell progressively during preincubation in the presence of 5 mM Mg2+. Additions of cAMP and ATP resulted in 40-70% activation of both triglyceride lipase and cholesterol esterase. The activation was blocked by protein kinase inhibitor and was restored by the addition of exogenous cAMP-dependent protein kinase. Since lipoprotein lipase has no activity toward cholesteryl oleate, activation of cholesterol esterase in untreated S1 was readily demonstrable. Both triglyceride lipase and cholesterol esterase activities were present in homogenates prepared from isolated rat heart myocytes. We conclude that the myocardium contains a hormone-sensitive lipase that is regulated in a fashion similar to that of the adipose tissue enzyme.
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PMID:Activation of myocardial neutral triglyceride lipase and neutral cholesterol esterase by cAMP-dependent protein kinase. 298 7

Cultured rat epididymal preadipocytes exposed for 24-72 h to either bezafibrate or clofibrate added to the culture medium were extensively converted to fat-loaded adipocytes. Adipocyte conversion increased during the first 5-7 days following plating, reaching a level of 100% and 60% conversion with bezafibrate and clofibrate, respectively, as compared to 10% conversion in their absence. Adipocyte conversion in culture was a saturable function of the hypolipidemic effectors and was associated with an increase in the incorporation rate of exogenous palmitate into triacylglycerols, in glycerol-3-phosphate dehydrogenase and hormone-sensitive lipase activities but not in lipoprotein lipase activity. Adipocyte conversion by hypolipidemic drugs was much more prominent than that exerted by dibutyryl cAMP, and the relative conversion efficiency of the two fibrate drugs did not correlate with their respective cAMP content of the culture. Hence, hypolipidemic drugs and dibutyryl cAMP appear to act independently in initiating adipose conversion in primary epididymal preadipocytes.
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PMID:Adipose conversion of cultured rat primary preadipocytes by hypolipidemic drugs. 301 19

The effect of dietary ethanol on metabolic fates of glucose and ethanol, and activities of lipoprotein lipase and hormone-sensitive lipase in several tissues of miniature pigs were determined in vitro. Ethanol and glucose were used at similar rates for fatty acid synthesis in liver and brain and CO2 production in liver. Ethanol was preferred over glucose for fatty acid and CO2 production in ileal mucosal cells. Glucose was the preferred substrate for lipogenesis and oxidation to CO2 in adipose tissue and skeletal muscle, and for oxidation to CO2 in brain. Dietary ethanol decreased glucose and ethanol conversion to fatty acids in ileal mucosa and brain, respectively. Dietary ethanol had no effect on the capacity of liver, adipose tissue, and skeletal muscle to convert either glucose or ethanol to long-chain fatty acids. The capacity to oxidize ethanol, but not glucose, to CO2 in liver was increased by dietary ethanol. No dietary ethanol effect was observed in other tissues. The capacity for removal of plasma triglycerides (based on lipoprotein lipase activity) tended to increase in adipose tissue and skeletal muscle of pigs fed ethanol. Mobilization of long-chain fatty acids from adipose tissue (based on hormone-sensitive lipase activity), triglyceride concentration in plasma, and percentage of lipid in liver remained unchanged when ethanol was fed. Livers of ethanol-fed pigs, however, were larger than livers of control pigs. Our results indicate that feeding miniature pigs 21-37% of total caloric intake as ethanol causes significant metabolic adaptations of lipid metabolism in liver and ileal mucosa, but not in adipose tissue, skeletal muscle, and brain. The ethanol feeding, however, did not cause fatty livers or hyperlipidemia.
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PMID:Adaptation of lipogenesis and lipolysis to dietary ethanol. 311 29

Progressive weight loss and anorexia are frequent phenomena in cancer patients. Although cachexia is an expected occurrence in the terminal stages of nearly all malignancies, it may be a presenting sign when the tumor burden is quite small. Lipid depletion occurs out of proportion to the protein loss and accounts for most of the weight loss in cancer. Lipids, more specifically fatty acids, are the major source of fuel in mammals and may also be used in the synthesis of new cell products. Lipolysis and lipogenesis are under the influence of several important enzymes and peptide hormones that may be modulated by a variety of exogenous factors. There is evidence that cancer patients have lost the normal homeostatic responses to decreased energy intake or starvation that allow a decrease in oxygen consumption and protein sparing. An increase in Cori cycle activity or futile recycling of metabolic products occurs with a net energy expenditure rather than energy production. Clinical studies have shown that the body lipid depletion accompanying tumor progression is not solely secondary to decreased food intake and may be reproduced by the transplantation of certain noninvasive tumors to normal hosts. Elevated basal lipolysis has occasionally been seen early in tumor growth. Such findings suggest the presence of a tumor-associated factor responsible for this increase in lipid mobilization. Some of the potential mechanisms for the altered lipid metabolism seen in cancer have been discussed. Metabolic substrates may be remodeled and directed away from fuel-efficient into energy-requiring pathways. An increased energy expenditure may occur as a result of the energy costs of tumor synthesis, an uncoupling of oxidative phosphorylation, or energy-requiring futile cycling. An overall depletion of lipid may be the final outcome of the inhibition of lipid deposition. TNF/cachectin has recently been found to suppress the activity and synthesis of several key lipogenic enzymes, including lipoprotein lipase. Abnormalities in insulin secretion or sensitivity may be involved in the decrease of fat storage in malignancy. Insulin also exerts a significant antilipolytic effect by its antagonism of hormone-sensitive lipase. Mediators of lipolysis and abnormal lipid metabolism may occur in a number of clinical conditions and include ectopic hormone production, growth factors, and tumor-associated lipolytic factors (lipid mobilizing factor, toxohormone).
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PMID:Fat metabolism and cancer. 353 75

A polyclonal rabbit antibody was used to detect hormone-sensitive lipase in rat organs other than white adipose tissue. Inhibition of tissue diacylglycerol lipase activity by the anti-hormone-sensitive lipase, and by NaF, Hg2+ and diisopropyl fluorophosphate, known inhibitors of the hormone-sensitive lipase, demonstrated its presence in the adrenals, ovaries, testes, heart and skeletal muscle, but not in the liver and kidneys. After enrichment by immunoprecipitation an immunoreactive protein, corresponding to the adipose tissue hormone-sensitive lipase 84 kDa subunit, and some additional, higher Mrapp proteins, were detected by Western blotting in the same tissues. The adipose tissue contained greater than 80% of the total hormone-sensitive lipase, with 5-10- and 50-100-fold lower specific activity in the steroid-producing and the muscle tissues, respectively.
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PMID:Immunological evidence for the presence of hormone-sensitive lipase in rat tissues other than adipose tissue. 367 97

Biological activities of estrogen molecules are altered by fluorination of ring A, and the resulting impairment to form catechols. 2-fluoroestradiol (2-F-E2) has been found to be devoid of carcinogenic action despite its high estrogenic potency; its metabolic effects are so far unknown. This study was designed to investigate the effects of 2-F-E2 on lipid metabolism, as compared to those of estradiol-17 beta(E2). Ovariectomized rats received E2 or 2-F-E2 by s.c. injection at a dose of 60 micrograms for three consecutive days. Parameters measured were weights of parametrial fat depots, fat cell volumes, levels of triacylglycerol and acylcholesterol in plasma, and enzymatic responses to the estrogens in isolated parametrial fat cells as evaluated in terms of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities. 2-F-E2 and E2 were found to produce comparable decreases in fat depots, cell volumes and plasma levels of acylcholesterol whereas plasma triacylglycerol was unchanged. Both estrogens decreased LPL, and increased HSL activities to the same extent. Thus, 2-F-E and E2 exhibited comparable effects on lipid metabolism. These effects appeared to depend mainly on the estrogenic potency of these molecules, and to be distinct from their carcinogenic action. Despite its high estrogenic potency, 2-F-E2 was found to be slightly less estrogenic than E2.
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PMID:Effects of 2-fluoroestradiol on lipid metabolism in the ovariectomized rat. 377 28

Colchicine injection was used as a tool to potentiate the increase in intracellular lipoprotein lipase (type L hormone-sensitive lipase) activity normally seen with fasting to determine if elevation of enzyme activity by this method produced a reduction in endogenous triacylglycerol (TG) in rat heart. Both fasting and fasting+colchicine treatment increased total lipoprotein lipase (LPL) activity from a control value of 80 units/g to approx. 144 units/g. The initial control value was obtained at 08:00 h after overnight feeding and the final values were obtained at 17:00 h, after 9 h of fasting. Fasting alone increased activity in both the capillary-bound LPL and type L hormone-sensitive lipase (HSL) fractions of cardiac muscle. In contrast, colchicine treatment, by blocking the export of enzyme from the cell as a result of microtubular disruption, restricted the increase in enzyme activity to the intracellular fraction of the heart. There was a highly significant (P less than 0.001) negative relationship (r = -0.73) between type L HSL activity and TG content in hearts of fasting and fasting+colchicine-treated rats. At a time when type L HSL activity was increased and TG content decreased, the cyclic AMP concentration of heart remained unchanged, ruling out the possibility that cyclic AMP might be activating any one of the identified cardiac TG lipases. These data provided indirect evidence that type L HSL is 'seeing the intracellular TG droplet' and that this enzyme may play a role in the regulation of myocardial lipolysis.
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PMID:Relationship between type L hormone-sensitive lipase activity and endogenous triacylglycerol in the hearts of colchicine-treated rats. 609 67

We have compared the effects of cellular cyclic AMP modulation on the regulation of lipoprotein lipase in cultures of rat epididymal pad preadipocytes and mesenchymal heart cells. Addition of dibutyryl cyclic AMP (dibutyryl cAMP) or 3-isobutyl-1-methylxanthine (IBMX) to preadipocytes grown in serum-containing culture medium resulted in a progressive decrease in lipoprotein lipase activity released into the culture medium so that at 6-8 h enzyme activity ranged between 20 and 30% of that recovered in the control dishes. Similar short-term (6-8 h) studies of the heart cell cultures showed a variable and much less pronounced depression of lipoprotein lipase activity. Thus, following dibutyryl cAMP and IBMX treatment, lipoprotein lipase activity ranged between 70 and 95% of control values. Incubation for 6 h with cholera toxin was followed by a 4-fold rise in the concentration of cellular cyclic AMP in both types of culture, but while in heart cell cultures enzyme activity was unchanged, lipoprotein lipase activity in preadipocytes decreased to 30% of control value. After 24 h incubation with all three effectors, an increase in lipoprotein lipase activity was seen. In the preadipocytes the increase ranged between 50 and 150% above control value, in the heart cell cultures it was 100-250%. 24-h incubation of heart cell cultures with dibutyryl cAMP resulted in a 6-fold increase of heparin-releasable lipoprotein lipase activity while residual activity was doubled. The rise in surface-bound lipoprotein lipase was evidenced also by an increase in the lipolysis of chylomicron triacylglycerol. In the presence of cycloheximide, the dibutyryl cAMP-induced heparin-releasable and residual lipoprotein lipase activity declined at the same rate as the basal activity. The reason for the difference in response of cultured preadipocytes and heart cells to the effectors during the first 8 h of incubation has not been elucidated, but could be related to a possible absence of hormone-sensitive lipase in the heart cells, and hence in a difference in intracellular metabolism of triacylglycerol. On the other hand, a common mechanism can be postulated for the long-term effect of cyclic AMP on the induction of lipoprotein lipase activity in both types of cultures. It probably involves mRNA and protein synthesis, which culminates in an increase in enzyme activity.
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PMID:Modulation of lipoprotein lipase activity in cultured rat mesenchymal heart cells and preadipocytes by dibutyryl cyclic AMP, cholera toxin and 3-isobutyl-1-methylxanthine. 618 19


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