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PubMed1998

Hepatic lipase activity is lower in African American men than in white American men: effects of 5' flanking polymorphism in the hepatic lipase gene (LIPC).

Plasma high density lipoprotein cholesterol (HDL-C) concentrations are higher in African American men than in white men, but the mechanism(s) responsible for this ethnic difference has not been elucidated. This study examined the relationship between hepatic lipase activity, plasma HDL-C concentrations, and a hepatic lipase polymorphism (-514T) in African American and white American men. Consistent with previous reports, plasma HDL-C concentrations were significantly higher in African American men than in white American men. Mean post-heparin plasma hepatic lipase activity was significantly lower in African American than in white American men (27 +/- 12 vs. 44 +/- 17 mmol x h(-1) x l(-1), P < 0.001). The -514T hepatic lipase allele was associated with low hepatic lipase activity in both populations, and was 3-fold more common among African Americans than white Americans. Taken together, these data suggest that genetic differences in hepatic lipase activity contribute to the differences in plasma HDL-C concentrations between African American men and white American men.

Adult↗
PubMed1981

Lipoprotein lipase and monoacylglycerol lipase activities during maturation of ob17 preadipocytes.

Lipoprotein lipase and monoacylglycerol lipase activities of developing ob17 preadipocytes were assayed through the selective inhibition of the former activity by 0.4% Triton X-100. After confluence both enzymes rose tao a peak activity around 13--15 days which was enhanced in insulin-treated cells. Inclusion of differentiation-blocking agents (bromodeoxyuridine, prostaglandin F2 alpha and bovine retinal extract) in the culture medium led in both enzymes to levels similar to those obtained in exponentially growing cells, in contrast to unspecific monoester hydrolase. Marked changes in the relative proportion of released to intracellular lipoprotein lipase activities were observed during adipose conversion. Our studies indicate that lipoprotein lipase and monoacylglycerol lipase are integral part of the program of differentiation of adipose cells.

Adipose Tissue↗
PubMed1983

Measurement of lipoprotein lipase and hepatic triacylglycerol lipase in post-heparin plasma of the cynomolgus monkey.

Conditions for measurement of the lipolytic activities, lipoprotein lipase and hepatic triacylglycerol lipase in cynomolgus monkey postheparin plasma are described. The two activities are separable by heparin-Sepharose chromatography. Goat anti-human hepatic triacylglycerol lipase serum inhibits monkey hepatic triacylglycerol lipase activity and allows direct measurement of lipoprotein lipase in post-heparin plasma. While both human and homologous serum can be used as a source of activator apolipoprotein, homologous serum produces a much greater activation.

Animals↗
PubMed1980

The validation and use of specific methods for the estimation of lipoprotein lipase and hepatic lipase activities in post-heparin plasma of children with hyperlipidaemia.

The methods proposed by Nilsson-Ehle and Ekman [8] for the specific estimation of lipoprotein lipase and hepatic lipase activities in post-heparin plasma were investigated. The procedure for hepatic lipase was found to be specific, but the lipoprotein lipase assay required modification to abolish hepatic lipase interference. The modified procedures were fully validated and found to be relatively simple, rapid and specific and were used to investigate children with primary and secondary hyperlipidaemic states.

Adolescent↗
PubMed1981

Effect of probucol on the activity of postheparin plasma lipoprotein lipase and hepatic lipase.

The effect of discontinuation of long term (34-56 months) probucol treatment on serum lipids, lipoproteins and on the activity of postheparin plasma lipoprotein and hepatic lipase ahs been studied in 10 healthy males participating in a primary prevention programme of coronary heart disease. A significant increase was observed in the activity of postheparin plasma lipoprotein lipase, in the total serum cholesterol concentration and in the serum concentrations of high density lipoprotein (HDL) cholesterol, HDL phospholipids and apoprotein AI after withdrawal of the drug No changes were seen in the serum triglyceride levels or in the activity of postheparin plasma hepatic lipase. The activity of postheparin plasma hepatic lipase tended to correlate with the serum concentration of HDL. No correlations were present between the individual changes in the serum levels of HDL and in the activity of postheparin plasma triglyceride lipases.

Apolipoprotein A-I↗
PubMed1995

Influence of lipoprotein lipase and hepatic lipase on the transformation of VLDL and HDL during lipolysis of VLDL.

In order to study the relative effects of lipolytic enzymes on the removal of lipids and apolipoproteins, in particular apolipoprotein (apo) E and cholesteryl ester, from human very low density lipoprotein (VLDL) during its conversion to product lipoproteins, the action of lipoprotein lipase (LPL) and the combined action of lipoprotein lipase and hepatic lipase (HL) were studied in the presence of physiological proportions of high density lipoprotein (HDL) (10 mg protein), VLDL (2 mg protein) and albumin in an amount sufficient for the binding of all released fatty acids. The HDL used in the incubation was free of apo E in order to facilitate assessment of apo E transfer from VLDL to HDL. The redistribution of lipid and apolipoprotein mass and the movement of labeled cholesteryl ester from VLDL to other lipoprotein fractions was assessed by density gradient ultracentrifugation. Following 90%-95% lipolysis of VLDL triglycerides by rat heart LPL in 2 h, there was an almost complete transfer of apo C-II and apo C-III to HDL but only 20% of VLDL apo E was transferred to HDL. There was significant augmentation of HDL unesterified cholesterol and phospholipid mass during LPL action despite a substantial overall phospholipid hydrolysis (30%). The transfer of cholesteryl ester mass to HDL was variable (0%-13%) with a mean transfer of 7% of VLDL cholesteryl ester. Transfer of labeled VLDL cholesteryl ester to HDL was 3%-6%. A considerable amount of the VLDL lipid mass appeared in the light fraction of the low density lipoprotein (LDL) region, but a substantial amount remained in the VLDL/intermediate density lipoprotein (IDL) region. The post-lipolysis particles that were isolated in the VLDL-LDL density range were larger than LDL and contained a high ratio of surface lipids relative to core lipids as compared to plasma LDL. The inclusion of human HL with LPL did not alter the redistribution of apolipoproteins proteins or lipids from VLDL to LDL or to HDL. The major effect of HL, relative to that observed with LPL alone, was a marked hydrolysis of HDL triglycerides (68%). Despite the combined action of LPL and HL on VLDL in the presence of HDL and over 90% lipolysis of triglycerides, a major portion of residual VLDL mass remained in fractions lighter than normal LDL density and retained apo E. It is concluded that lipoprotein lipase of LPL in combination with HL are ineffective in bringing about the complete conversion of plasma VLDL to LDL. Lipoprotein lipase was effective in substantially augmenting the HDL mass including cholesteryl while the major effect of HL was the selective hydrolysis of HDL triglycerides.

Animals↗
PubMed2004

Lipoprotein lipase and endothelial lipase expression in mouse brain: regional distribution and selective induction following kainic acid-induced lesion and focal cerebral ischemia.

Lipoprotein and endothelial lipases are members of the triglyceride lipase gene family. These genes are expressed in the brain, where the encoded proteins are fulfilling functions that have yet to be elucidated. In this study, we examined the distribution of their respective mRNAs in the C57BL/6 mouse brain by in situ hybridization. In control mice, we observed widespread expression of lipoprotein lipase (LPL) mRNA mainly in pyramidal cells of the hippocampus (CA1, CA2 and CA3 areas), in the striatum and in several cortical areas. Endothelial lipase (EL) mRNA expression was restricted to CA3 pyramidal cells of the hippocampus, to ependymal cells in the ventral part of the third ventricle and to some cortical cell layers. To gain insight into the role played by lipases in the brain, neurodegeneration was induced by intraperitoneal injection of kainic acid (KA) or by occlusion of the middle cerebral artery (MCA). Upon injection of KA, a rapid increase in EL mRNA expression was observed in the piriform cortex, hippocampus, thalamus and neocortex. However, the levels of LPL mRNA were unaffected by KA injection. Remarkably, after focal cerebral ischemia, the expression of EL was unaffected whereas a dramatic increase in LPL expression was observed in neocortical areas of the lesioned side of the brain. These results show that LPL and EL transcripts are selectively upregulated in function of the type of brain injury. LPL and EL could thus fulfill a function in the pathophysiological response of the brain to injury.

Animals↗
PubMed2000

Linkage and association studies of the lipoprotein lipase gene with postheparin plasma lipase activities, body fat, and plasma lipid and lipoprotein concentrations: the HERITAGE Family Study.

Lipoprotein lipase (LPL) is responsible for the hydrolysis of triglyceride (TG)-rich lipoproteins. The aims of the present study were (1) to test for potential linkages (sib-pair method) between postheparin plasma lipase (lipoprotein and hepatic lipase) activities, body fatness, plasma lipid concentrations, and LPL polymorphisms (Ser447Ter and a tetranucleotide repeat) and microsatellite markers flanking the LPL locus (D8S261 and D8S258); and (2) to investigate associations between the LPL Ser447Ter (S447X) polymorphism and these phenotypes. Data on 190 parents and 312 adult offspring from 99 Caucasian families participating in the HERITAGE Family Study were available for this study. Data were adjusted for the effects of age within sex, and lipases, lipid variables, and abdominal visceral fat were further adjusted for fat mass. A suggestive linkage was observed only between the S447X polymorphism and very-low-density (VLDL)-apolipoprotein B (apo B) (332 sib-pairs, P = .013). The S447X polymorphism was not associated with body fat phenotypes or postheparin plasma LPL (PH-LPL) activity (men, P = .19; women, P = .47). In contrast, the X447 allele carriers had lower plasma TG (men and women, P = .01), VLDL-TG (men and women, P = .01), and VLDL-apo B (men and women, P = .009). The relationships between the X447 allele and plasma TG, VLDL-TG, and VLDL-apo B in both genders were observed in obese (body mass index [BMI] > or = 30 kg/m2) but not in normal-weight (BMI < 25 kg/m2) subjects. Thus, the S447X polymorphism of the LPL gene is not associated with body fatness and postheparin plasma lipase activities. However, the obese carriers of the X447 allele have plasma TG, VLDL-TG, and plasma cholesterol/high-density lipoprotein cholesterol (HDL-C) levels equivalent to those of normal-weight sedentary adults.

Adipose Tissue↗
PubMed1979

Properties of salt-resistant lipase and lipoprotein lipase purified from human post-heparin plasma.

Lipoprotein lipase and salt-resistant lipase were isolated from human post-heparin plasma. The proteins of human post-plasma lipoprotein lipase and salt-resistant lipase were identified and demonstrated to be immunologically different. Significant differences between the two enzymes in their relative amino acid composition were demonstrated, which indicates that the two enzymes are different proteins. When analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the enzymes seemed to have monomer molecular weights similar to that of lipoprotein lipase purified from bovine milk.

Amino Acids↗
PubMed1986

Effect of diabetes on acid and neutral triacylglycerol lipase and on lipoprotein lipase activities in isolated myocardial cells from rat heart.

A neutral triacylglycerol lipase activity that is separate and distinct from lipoprotein lipase (LPL) could be measured in homogenates of myocardial cells if protamine sulphate and high concentrations of albumin were included in the assay. This neutral lipase was predominantly particulate, with the highest relative specific activity in microsomal subcellular fractions. The induction of diabetes by the administration of streptozotocin to rats resulted in a decrease in LPL activity in myocyte homogenates and in particulate subcellular fractions, but the percentage of cellular LPL activity that was released during incubation of myocytes with heparin was normal. In contrast, neutral lipase activity was increased in diabetic myocyte homogenates and microsomal fractions. Acid triacylglycerol lipase activity was not changed in diabetic myocytes. The decrease in LPL in myocytes owing to diabetes may result in the decreased functional LPL activity at the capillary endothelium of the diabetic heart.

Animals↗
PubMed1978

Effect of acute ethanol load on postheparin plasma lipoprotein lipase and hepatic lipase activities and intravenous fat tolerance.

This study aimed to examine the possibility that ethanol-induced rise of serum triglyceride concentration in man is partly due to an impaired removal of triglycerides from the circulation. Acute ethanol loads given to normal human subjects after an overnight fast reduced the postheparin plasma lipoprotein lipase activity by an average of 25% but did not influence the postheparin plasma hepatic lipase activity or fractional removal of Intralipid triglyceride. When alcolhol was administered to fed subjects in the evening the postheparin plasma hepatic lipase was significantly decreased in the next morning as compared to corresponding control value but the lipoprotein lipase and Intralipid clearance were not changed. It is concluded that the slight decrease of lipoprotein lipase during alcohol intoxication may contribute to the hyperlipemic effect of ethanol.

Ethanol↗
PubMed1983

Experimental hyperthyroidism in man: effects on plasma lipoproteins, lipoprotein lipase and hepatic lipase.

We have studied the effects of triiodothyronine administration (20-40 micrograms three times daily over one week) in six healthy young men, on the activities of lipoprotein lipase and hepatic lipase and on plasma lipoprotein concentrations. Hepatic lipase activity in post-heparin plasma rose by 46 +/- 25% (p less than 0.025), whereas the activity of lipoprotein lipase did not change significantly. Plasma cholesterol concentrations decreased by about 20% (p less than 0.025), whereas there was no change in plasma triglyceride levels. The fall in plasma cholesterol could be accounted for by a reduction of HDL cholesterol (-11%, p less than 0.025) as well as LDL cholesterol (-27%, p less than 0.025). The data emphasize the role of hepatic lipase in the lipoprotein alterations associated with thyroid dysfunction.

Adult↗
PubMed1986

Homology of lipoprotein lipase to pancreatic lipase.

Bovine milk lipoprotein lipase was subjected to amino acid sequence analysis. The first 19 amino-terminal residues were Asp-Arg-Ile-Thr-Gly-Gly-Lys-Asp-Phe-Arg-Asp-Ile-Glu-Ser-Lys-Phe-Ala-Leu- Arg. In addition, reversed-phase high-performance liquid chromatography of a tryptic digest of reduced and alkylated lipase resolved a number of peptides, five of which contained cysteine. Sequence analysis of the tryptic peptides revealed in most instances a close homology to porcine pancreatic lipase. Based on this homology, the relative alignment of the sequenced lipoprotein lipase peptides can be made. In addition, a potential binding site for the triacylglycerol substrate and a carbohydrate-binding domain for lipoprotein lipase are postulated.

Amino Acid Sequence↗
PubMed1992

Bradykinin stimulates arachidonic acid release through the sequential actions of an sn-1 diacylglycerol lipase and a monoacylglycerol lipase.

In cultured dorsal root ganglion (DRG) neurons prelabeled with [3H]arachidonic acid [( 3H]AA), bradykinin (BK) stimulation resulted in increased levels of radioactive diacylglycerol, monoacylglycerol, and free AA. The transient increases in content of radioactive diacylglycerol and monoacylglycerol preceded the increase in level of free AA, suggesting the contribution of a diacylglycerol lipase pathway to AA release. An analysis of the molecular species of diacylglycerols in unstimulated cultures revealed the presence of two primary [3H]AA-containing species, 1-palmitoyl-2-arachidonoyl and 1-stearoyl-2-arachidonoyl diacylglycerol. BK stimulation resulted in a preferential increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. When DRG cultures were labeled with [3H]stearic acid, treatment with BK increased the amount of label in diacylglycerol and free stearic acid, but not in monoacylglycerol. This result suggested that AA release occurred through the successive actions of an sn-1 diacylglycerol lipase and monoacylglycerol lipase. Other data supporting a diacylglycerol lipase pathway was the significant inhibition of [3H]AA release and consequent accumulation of diacylglycerol by RG 80267, which preferentially inhibits diacylglycerol lipase. Analysis of the molecular species profiles of individual phospholipids in DRG neurons indicated that phosphoinositide hydrolysis may account for a significant portion of the rapid increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. We were unable to obtain evidence that the phospholipase A2 pathway makes a significant contribution to BK-stimulated AA release in DRG cultures. Under our assay conditions there were no BK-stimulated increases in levels of radioactive lysophosphatidylinositol, lysophosphatidylcholine, or lysophosphatidylethanolamine in cultures prelabeled with [3H]inositol, [3H]choline, or [3H]-ethanolamine, respectively.

Animals↗
PubMed2000

Lipoprotein lipase- and hepatic triglyceride lipase- promoted very low density lipoprotein degradation proceeds via an apolipoprotein E-dependent mechanism.

Apolipoprotein E (apoE) is the primary recognition signal on triglyceride-rich lipoproteins responsible for interacting with low density lipoprotein (LDL) receptors and LDL receptor-related protein (LRP). It has been shown that lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) promote receptor-mediated uptake and degradation of very low density lipoproteins (VLDL) and remnant particles, possibly by directly binding to lipoprotein receptors. In this study we have investigated the requirement for apoE in lipase-stimulated VLDL degradation. We compared binding and degradation of normal and apoE-depleted human VLDL and apoE knockout mouse VLDL in human foreskin fibroblasts. Surface binding at 37 degrees C of apoE knockout VLDL was greater than that of normal VLDL by 3- and 40-fold, respectively, in the presence of LPL and HTGL. In spite of the greater stimulation of surface binding, lipase-stimulated degradation of apoE knockout mouse VLDL was significantly lower than that of normal VLDL (30, 30, and 80%, respectively, for control, LPL, and HTGL treatments). In the presence of LPL and HTGL, surface binding of apoE-depleted human VLDL was, respectively, 40 and 200% of normal VLDL whereas degradation was, respectively, 25 and 50% of normal VLDL. LPL and HTGL stimulated degradation of normal VLDL in a dose-dependent manner and by a LDL receptor-mediated pathway. Maximum stimulation (4-fold) was seen in the presence LPL (1 microgram/ml) or HTGL (3 microgram/ml) in lovastatin-treated cells. On the other hand, degradation of apoE-depleted VLDL was not significantly increased by the presence of lipases even in lovastatin-treated cells. Surface binding of apoE-depleted VLDL to metabolically inactive cells at 4 degrees C was higher in control and HTGL-treated cells, but unchanged in the presence of LPL. Degradation of prebound apoE-depleted VLDL was only 35% as efficient as that of normal VLDL. Surface binding of apoE knockout or apoE-depleted VLDL was to heparin sulfate proteoglycans because it was completely abolished by heparinase treatment. However, apoE appears to be a primary determinant for receptor-mediated VLDL degradation. Our studies suggest that overexpression of LPL or HTGL may not protect against lipoprotein accumulation seen in apoE deficiency.

Animals↗
PubMed1989

Effects of weight loss and weight maintenance on the serum lipids, lipoprotein lipase and hepatic triglyceride lipase activities in obese rats.

The effects of obesity, weight loss and weight maintenance on the serum lipid levels and lipoprotein lipase and hepatic triglyceride lipase were investigated in rats. Obesity induced by high-fat (HF) feeding was associated with decreased serum triglyceride levels (HF: 70.3 +/- 8.2, control (CON): 140.0 +/- 26.9 mg/dl, P less than 0.05), increased lipoprotein lipase (LPL, HF: 593.2 +/- 10.6 vs CON: 280 +/- 19.5 nmol FFA/min per mg tissue, P less than 0.05) and suppressed hepatic triglyceride lipase activities (HTGL, HF: 14.2 +/- 0.5 vs CON: 18.0 +/- 0.4 nmol FFA/min per mg tissue, P less than 0.01). After a weight loss to the level of control rats, weight maintenance was achieved either by high-protein (HP) or chow feedings (CH). Both high-protein (HFHP) and chow (HFHC) groups had similar weights but only high-protein feeding restored the normal body compositions. Both groups of rats had higher total (TC, HFHP: 146 +/- 10.7; HFCH: 104.8 +/- 5.1 mg/dl), and high density lipoprotein cholesterol levels (HDL-C, HFHP: 100.8 +/- 15.6; HFCH: 75.5 +/- 5.5 mg/dl) and lower lipoprotein lipase (HFHP: 238.2 +/- 15.8, HFCH: 354.8 +/- 34.9 nmol FFA/min per mg tissue) and hepatic triglyceride activities (HFHP: 16.3 +/- 1.1; HFCH: 14.5 +/- 0.6 nmol FFA/min per mg tissue) than control rats (TC: 70.1 +/- 4.7 mg/dl; HDL-C: 14.2 +/- 4.3 mg/dl; LPL: 742.4 +/- 82.3 nmol FFA/min per mg tissue; HTGL: 20.5 +/- 1.0 nmol FFA/min per mg tissue, P less than 0.05 to 0.005) or the rats who regained weight by resuming high-fat feeding (TC: 59.5 +/- 6.7 mg/dl; HDL-C: 10.2 +/- 6.7 mg/dl; LPL: 1284.3 +/- 90 nmol FFA/min per mg tissue; HTGL: 22.2 +/- 1.9 nmol FFA/min per mg tissue, P less than 0.05 to 0.005). The high protein-group had significantly higher total and high-density-lipoprotein cholesterol levels than the chow fed animals despite comparable body weights in both groups. The findings of this study suggest that weight maintenance induced by high protein feeding is more successful in restoring the normal body composition. However, high protein feeding is also associated with high serum cholesterol levels. The clinical applications of these findings need to be evaluated further.

Animals↗
PubMed1978

A comparison of molecular properties of hepatic triglyceride lipase and lipoprotein lipase from human post-heparin plasma.

Hepatic triglyceride lipase was isolated from human post-heparin plasma by the method of Ehnholm et al. using modifications which increased the specific activity 12-fold to approximately 3,000 mumol of free fatty acid/h/mg of protein. Lipoprotein lipase with similar specific activity was prepared from the same plasma samples using heparin and concanavalin A affinity chromatography. The molecular weight of hepatic triglyceride lipase (69,000) was slightly greater than that of lipoprotein lipase (67,000) as determined by polyacrylamide electrophoresis in sodium dodecyl sulfate-containing buffers. These proteins had identical amino acid compositions, terminal amino acid residues, and tryptic peptide maps. However, the differences previously described regarding optima of pH and ionic strength and the requirement for apolipoprotein CII (only for lipoprotein lipase) were maintained in the highly purified state. It was found that both proteins contain approximately 8% carbohydrate. Antisera prepared in goats selectively precipitated each activity. Other antisera prepared in chickens reacted with both enzymes, suggesting a common antigenic determinant.

Adult↗