Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 kinetics of thermal inactivation of cow's milk lipoprotein lipase (LPL) was studied. LPL inactivation can be described by the first order q equation. Thermodynamic parameters of LPL inactivation were calculated. In the range of physiological temperatures LPL existed as two conformers. The temperature of conformation conversion was 41.5 degrees C. Glycerol increased thermal stability of milk, whereas water dilution of milk, pH shift to the acid or alkaline zone, and glycine addition to milk decreased it. It is suggested that casein micellae stabilize milk LPL.
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PMID:[Thermal inactivation of milk lipoprotein lipase]. 4 51

1. When fat-cells are isolated from the epididymal adipose tissue of 24h-starved rats and incubated at 25 degrees C in the presence of dialysed serum, glucose, insulin, amino acids and heparin, the total clearing-factor lipase acitivity of the incubation system increases progressively over a period of several hours. 2. All of the increase in activity is accounted for by the appearance of enzyme in the appearance of enzyme in the incubation medium and the fat-cell activity does not change significantly. Cycloheximids, at a concentration that prevents protein synthesis, does not affect the appearance of enzyme in the incubation medium, but the fat-cell enzyme activity is decreased in its presence. 3. The magnitude of the increase in total clearing factor lipase activity is unaffected by the omission of heparin from the medium. However, less enzyme is extracted in tis absence and the fat-cell activity increases. Cycloheximide again only affects the rise in cell activity and does not alter the activity in the incubation medium. 4. When serum in the incubation medium is replaced by casein, the distribution of enzyme between the cells and the medium is changed, but the magnitudes of the increases in total enzyme activity are similar. 5. These characteristics of the clearing-factor lipase response of isolated fat-cells differ in several respects from those observed earlier with intact adipose tissue from 24h-starved rats (Robinson & Wing, 1971; Cryer et al., 1973). The differences could be due, in part, to changes in the relative amounts of two different molecular forms of the enzyme that occur during the isolation of the fat-cells.
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PMID:The clearing-factor lipase activity of isolated fat-cells. 80 20

Rabbits were fed purified diets consisting of casein (CA), fish protein (FP), and soy protein (SP) combined with MaxEpa oil (ME) or corn oil (CN) to determine the effects of dietary protein and lipid sources on serum total, lipoprotein, and hepatic lipid levels. Dietary proteins and lipids exerted significant (p < 0.05) separate effects on serum total cholesterol (TC) (p < 0.005), very-low-density lipoprotein cholesterol (VLDL-C) (p < 0.001), and high-density lipoprotein cholesterol (HDL-C) (p < 0.001), whereas only dietary proteins significantly affected low-density lipoprotein cholesterol (LDL-C) (p < 0.001) and the LDL-C/HDL-C ratio (p < 0.05). Hence, FP induced serum TC (233 mg/dl), VLDL-C (22 mg/dl), and LDL-C (151 mg/dl) intermediary to hypercholesterolemic CA (TC, 319 mg/dl; VLDL-C, 57 mg/dl; LDL-C, 204 mg/dl) and cholesterol-lowering SP (TC, 129 mg/dl; VLDL-C 19 mg/dl; LDL-C, 84 mg/dl). The twofold rise in HDL-C on feeding FP (35 mg/dl), compared with CA (20 mg/dl) and SP (16 mg/dl), resulted in a drop in LDL-C/HDL-C to a level similar to that of SP groups. The cholesterol-lowering action of ME (188 mg/dl), in contrast to CN (266 mg/dl), was reflected mainly in VLDL (ME, 15 mg/dl; CN, 50 mg/dl) but also in HDL (ME, 16 mg/dl; CN, 31 mg/dl) fractions. Compared with CN, the significant (p < 0.05) ME-induced rise in serum and VLDL triglycerides was accompanied by a significant (p < 0.001) drop in lipoprotein lipase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Factorial experiment to determine influence of fish protein and fish oil on serum and liver lipids in rabbits. 142 81

To study the relationships between lipolytic activities and plasma lipoprotein levels in rats, three diets were given for 8 weeks: a semipurified diet (based on sucrose, casein and lard) and this diet enriched with 5% cystine or with 1% cholesterol. Both supplemented diets induced hypercholesterolemia. Lipoprotein analysis by density gradient ultracentrifugation of plasma indicated that hypercholesterolemia of cystine-fed rats (+52%) was characterized by an increased cholesterol level in high-density lipoprotein (HDL; +131%) and low-density lipoprotein 2 (LDL2; +147%), the lipoprotein fraction containing essentially apolipoprotein-E-rich high-density lipoproteins (HDL1), and was associated with a decreased cholesterol level in triglyceride-rich lipoproteins (TRL: -69%). That obtained by cholesterol feeding (+28%) was due to a large increase in the TRL cholesterol level (+315%) whereas cholesterol was reduced in HDL (-40%) and in LDL2 (-60%). Under these dietary conditions, the activity of hepatic lipase (HL) was measured in liver homogenates and those of both HL and lipoprotein lipase were measured in plasma after heparin injection. The activity of HL (1,783 +/- 132 mU/g liver in control rats) was increased by 48% in cystine-fed rats and decreased by 40% in cholesterol-fed rats. Similar changes were observed in the activity of both lipases measured in postheparin plasma. Highly significant positive correlations linked each lipolytic activity with the level of cholesterol, phospholipids and proteins in LDL2 (HDL1-rich fraction) and in HDL. In contrast, significant negative correlations were found between all of the TRL components and the activity of the lipases.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lipolytic activities in rats fed a sucrose-rich diet supplemented with either cystine or cholesterol: relationships with lipoprotein profiles. 195 17

The principal lactogenic hormone, prolactin, secreted by the anterior pituitary is critical to the establishment of lactation, milk macronutrient content and milk production. The concentration of circulating prolactin increases during pregnancy so that by the end of gestation, levels are 10 to 20 times over normal amounts. However, prolactin is prevented from exerting its effect on milk secretion by elevated levels of progesterone. Following clearance of progesterone and estrogen at parturition, copious milk secretion begins. The minimal hormonal requirements for normal lactation to occur are prolactin, insulin and hydrocortisone. Prolactin stabilizes and promotes transcription of casein mRNA; may stimulate synthesis of alpha-lactalbumin, the regulatory protein of the lactose synthetase enzyme system; and increases lipoprotein lipase activity in the mammary gland. Prolactin levels decrease as lactation is established but nursing stimulates prolactin release from the pituitary which promotes continued milk production. Prolactin is secreted into milk at levels representative of the average circulating concentration. The physiological significance of milk prolactin to the infant is uncertain. Prolactin exists in three heterogenic forms which possess varying biological activity. The monomer with a molecular weight of 23 kDa is found in greatest quantity and is the principal biologically active form. The pattern of heterogeneity changes during pregnancy to favor even more monomer in proportion to the dimer. However, during lactation, the proportion of the monomer in circulation decreases in response to selective uptake of the monomer by the mammary gland. Over 90 percent of the prolactin in milk is present as the monomer. Prolactin may exert some of its biological effect by a shift in the ratio of active to less active forms of the molecule.
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PMID:A review of the hormone prolactin during lactation. 209 40

The ability of lipoprotein lipase to move across the mammary epithelium by a paracellular route was investigated. Five goats were milked hourly to activate the paracellular pathway. Three goats responded to hourly milking with a fivefold increase in milk lipoprotein lipase activity as compared with nonresponding goats. Massage of the mammary gland was necessary in the two nonresponding goats too cause increased lipoprotein lipase activity in milk. Oxytocin treatment during hourly milking also increased enzyme activity in milk from a nonresponding goat. Activation of the paracellular pathway by hourly milking increased milk sodium and protein and decreased potassium and lactose concentrations. After a 12-h milking interval, lipoprotein lipase activity was distributed primarily in the serum (48%) and cream (40%) fractions and, to a lesser extent, in the casein (12%) fraction. Hourly milking increased enzyme activity distributed in the serum fraction (62%), whereas enzyme activity associated with the cream (32%) and casein (6%) fractions decreased. Possible mechanisms for the origin of lipoprotein lipase in milk are discussed.
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PMID:Paracellular leakage of lipoprotein lipase across the mammary epithelium of the goat. 274 24

The effects of ligand binding to the scavenger receptor on the secretion of lipoprotein lipase by murine macrophages were examined. Inflammatory macrophages exposed to acetylated low-density lipoprotein (AcLDL) exhibited a dose-dependent, 40-80% increase in lipoprotein lipase secretion. This stimulation appeared to be unrelated to intracellular cholesterol and triacylglycerol levels and to phagocytosis in general. Resident and inflammatory macrophages treated with maleylated bovine serum albumin (Mal-BSA) showed a 3-fold increase in lipoprotein lipase secretion in a dose-dependent and time-dependent fashion. In contrast, dextran sulfate, which is another ligand recognized by the scavenger receptor, caused a dose-dependent decrease in lipoprotein lipase secretion. Casein, a ligand recognized by the Mal-BSA receptor, did not affect lipoprotein lipase secretion nor the ability of Mal-BSA to stimulate the enzyme, while dextran sulfate abolished the stimulatory effects of Mal-BSA. Since ethylamine, an inhibitor of receptor-mediated endocytosis, attenuated the increase in lipoprotein lipase secretion induced by AcLDL and Mal-BSA, but did not affect the inhibition induced by dextran sulfate, it is suggested that receptor-mediated endocytosis of ligands via the scavenger receptor might play a key role in the stimulation of lipoprotein lipase secretion in macrophages. This study reveals another mechanism for regulation of macrophage lipoprotein lipase secretion.
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PMID:Regulation of macrophage lipoprotein lipase secretion by the scavenger receptor. 317 35

Heparin can dissociate lipoprotein lipase from casein micelles, and addition of heparin enhances lipolysis in bovine but not in caprine milk. Heparin shortened the lag-time for binding of lipoprotein lipase to milk fat globules and for lipolysis. Heparin counteracted the inhibitory effects of skim milk on binding of lipase and on lipolysis. Heparin stimulated lipolysis in all bovine milk samples when added before cooling and in spontaneously lipolytic milk samples also when added after cooling. Heparin enhanced lipolysis of isolated milk fat globules. Hence, its effect is not solely due to dissociation of lipoprotein lipase from the casein micelles. Cooling of goat milk caused more marked changes in the distribution of lipase than cooling of bovine milk; the fraction of added 125I-labeled lipase that bound to cream increased from about 8 to 60%. In addition, caprine skim milk caused less inhibition of lipolysis than bovine skim milk. These observations provide an explanation for the high degree of cold storage lipolysis in goat milk. Heparin had only small effects on the distribution of lipoprotein lipase in caprine milk, which explains why heparin has so little effect on lipolysis in caprine milk. The distribution of 35S-labeled heparin in bovine milk was studied. In warm milk less than 10% bound to the cream fraction, but when milk was cooled, binding of heparin to cream increased to 45%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hydrolysis of bovine and caprine milk fat globules by lipoprotein lipase. Effects of heparin and of skim milk on lipase distribution and on lipolysis. 344 3

The present study was undertaken to compare plasma lipoprotein lipid composition, as well as white adipose tissue lipoprotein lipase activity, in rats fed purified diets high in either sucrose or corn oil. The experimental diets (65% of calories as sucrose or corn oil, 15% as the opposite nutrient, and 20% as casein) were given ad libitum for 4 weeks. An additional group was fed a nonpurified diet as a reference diet. Both sucrose and oil diets were spontaneously consumed in isocaloric amounts by the animals. Despite energy intakes that were 35% lower than that of the reference group, the sucrose and oil groups exhibited final body weights that were only 6 and 9% lower, respectively, than that of the reference group, and accumulated more fat in the epididymal depots. Postprandial as well as fasting total cholesterol levels were similar in the sucrose and oil groups, while the high-density lipoprotein to total cholesterol ratio was highest in the animals fed corn oil. In both the fasted and fed states, plasma total triglyceride levels were 73% higher in the sucrose group than in the corn oil group. The largest triglyceride differences due to diet were observed in the chylomicron + very-low-density lipoprotein fraction. The oil-fed rats accumulated large amounts of triglycerides in their livers. Postprandial lipoprotein lipase activity in epididymal adipose tissue was almost twice as high in the sucrose group as in the oil group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasma lipoprotein cholesterol and triglycerides and lipoprotein lipase activity in epididymal white adipose tissue of rats fed high sucrose or high corn oil diets. 353 41

Little is known about the effects of pre- and early postnatal protein malnutrition on energy storage (e.g., carcass lipid) and expenditure (e.g., brown adipose tissue [BAT] thermogenesis) and their reversibility by nutritional rehabilitation. Therefore, the purpose of these experiments was to examine the permanence of prenatal and early postnatal protein malnutrition on energy balance in rats. Five weeks before mating and through gestation adult female rats were fed either a 25 or 8% casein diet (designated 25 or 8). Diet reversals were performed at birth and/or at weaning (designated B or W) and the pups were cross-fostered at birth. Thus, the groups were: 25-25B (controls), 8-25W (gestational and lactational protein malnutrition, 8-25B (gestational protein malnutrition), and 25-8B-25W (lactational protein malnutrition). Animals were weighed and sacrificed 200-250 days postpartum for carcass composition. Retroperitoneal white adipose tissue (RWAT) and interscapular BAT (IBAT) wet weights and lipoprotein lipase (LPL) activity were also measured in the 25-25B and 8-25W groups. Nutritional rehabilitation at birth (8-25B) resulted in normal body weights as adults. Lactational protein malnutrition (25-8B-25W) resulted in intermediate body weights to the controls (25-25W), which had the greatest weights, and the 8-25W group, which had the lowest weights. The 8-25W and 25-8B-25W rats also had significantly decreased carcass wet weight and total body water, fat and fat-free dry mass relative to the 25-25B and 8-25B groups, the latter two of which did not differ in their carcass composition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of pre- and early postnatal protein malnutrition on carcass composition and lipoprotein lipase activity in male rats. 360 24


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