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PubMed1979

[Semi-automatic assay of post-heparin plasma lipoprotein lipase activity (author's transl)].

A simple method for the assay of post-heparin plasma lipoprotein lipase activity is described. The substrate was a stable intralipid solution. The amount of fatty acids released in the 37 degrees C incubation medium was measured several time during the reaction course, by light absorption on a Technicon auto-analyzer. By plotting these values on a graph paper, the curve of the post-heparin plasma lipoprotein lipase activity was obtained.

Autoanalysis↗
PubMed1987

Activation of lipoprotein lipase by apolipoprotein C-II is modulated by the COOH terminal region of apolipoprotein C-III.

The in vitro effect of apolipoprotein C-II (apo C-II) on the apolipoprotein C-III (apo C-III) induced activation of bovine milk lipoprotein lipase (LPL) was studied in vitro using a synthetic substrate. Apo C-III effectively inhibited, in a dose-dependent manner, the activation of lipoprotein lipase induced by apo C-II. A 3-fold molar apo C-III excess decreased the lipoprotein lipase activity by 25%. Thrombin cleavage of apo C-III produced two fragments: only fragment 41-79 retained the inhibitory activity and was equipotent to native apo C-III1 on a molar basis. Neither displacement of apo C-II from the substrate, as determined using 125I-labeled apo C-II, nor the charge carried by sialic residues of apo C-III, as demonstrated in experiments performed after neuraminidase treatment, accounted for this effect. I speculate that apo C-III may act by inhibiting the apo C-II-LPL interaction.

Animals↗
PubMed1979

Enzyme immunoassay for measuring lipoprotein lipase activator in milk.

A method for determining the relative amount of lipoprotein lipase activator in milk was developed. The activator was measured in arbitrary units which were based on a standard curve for high density lipoprotein. Activator varied between cows not only in whole milk but also in skim milk and milk serum. Most of the activator was in the skim milk, and the amount of activator in milk serum varied between 32 and 91% of that in skim milk. In seven of eight cows, free fatty acids of milk increased with increasing units of activator.

Animals↗
PubMed1989

Effects of doxazosin and other antihypertensives on serum lipid levels and lipoprotein lipase in the C57BR/cdJ mouse.

Doxazosin has been shown to lower serum cholesterol levels in the cholesterol-fed (0.75% in a synthetic diet that contains sucrose and cholic acid) C57BR/cdJ mouse. These studies show that the drug's main effect is to lower low-density lipoprotein (LDL) cholesterol and leave high-density lipoprotein (HDL) cholesterol levels unchanged. The drug had cholesterol-lowering effects in this model at doses down to 3 mg/kg. In order to determine if these effects are unique to selective alpha 1-inhibitors, other antihypertensives including hydralazine, papaverine, and captopril were investigated. None of the drugs has any effects on the plasma lipid metabolite levels. The effects of propranolol and polythiazide on plasma lipid levels were also examined in these mice. Propranolol had no effect, whereas the diuretic increased plasma cholesterol levels. Both propranolol and polythiazide increased plasma triglycerides. Doxazosin has been shown to inhibit cGMP phosphodiesterase in the laboratory. The effects of zaprinast, a cGMP phosphodiesterase inhibitor, were tested in order to determine if this property of the drug could be responsible for its lipid-lowering activity. The data show that there are no effects on plasma lipids in zaprinast-treated animals. Doxazosin treatment increased heparin-releasable lipoprotein lipase in fasted chow-fed mice. The drug was without effect on the activity of hepatic lipase present in the plasma after heparin release. No effects were observed on the tissue levels of either hepatic or lipoprotein lipases (heart or adipose tissue).

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

Triglyceride-lowering effect of dietary vitamin E in streptozocin-induced diabetic rats. Increased lipoprotein lipase activity in livers of diabetic rats fed high dietary vitamin E.

High vitamin E supplementation in the diets of streptozocin-induced diabetic rats eliminates accumulation of lipid peroxides in the plasma and the liver, returns the plasma triglycerides toward normal levels, and increases the activity of lipoprotein lipase. Vitamin E has no effect on the levels of insulin or glucose. These findings suggest that vitamin E increases the total hepatic triglyceride lipase activity by increasing the lipoprotein lipase activity possibly by protecting the membrane-bound lipase against peroxidative damage.

Animals↗
PubMed1993

Prevention of raised low-density lipoprotein cholesterol in a patient with familial hypercholesterolaemia and lipoprotein lipase deficiency.

Raised low-density lipoprotein (LDL) cholesterol is believed to predispose to development of atherosclerosis and coronary heart disease. Increased plasma LDL concentrations and premature coronary heart disease are present in familial hypercholesterolemia (FH), and the enzyme lipoprotein lipase (LPL) seems to have a key role in production of LDL. We describe a unique French Canadian individual who is both heterozygous for FH and homozygous for LPL deficiency (FH/LPL). In this patient, LDL cholesterol was strikingly low compared with both his FH (0.65 vs 5.84 mmol/L) and normolipidaemic (2.77 mmol/L) age-matched relatives despite the defect of LDL-receptor-mediated removal. No LDL peak was present in the cholesterol profile of the FH/LPL-deficient subject, as determined by density-gradient ultracentrifugation. Our results suggest that most LDL particles, in vivo, originate from triglyceride-rich lipoproteins, that LPL plays a vital part in this process, and that absence of LPL activity protects FH subjects against the increase in LDL cholesterol.

Adolescent↗
PubMed2001

Lipoprotein lipase and cholesterol transfer activities of lean and obese Zucker rats.

Adult female lean and obese Zucker rats maintained under standard conditions were used for the estimation of plasma, liver and white adipose tissue (WAT) activity of lipoprotein lipase, plasma and liver hepatic lipase and plasma lecithin-cholesterol acyltransferase. No differences in plasma or tissue levels of lipoprotein lipase between lean and obese rats were detected, but the larger WAT size of the obese rats resulted in higher lipase activity per unit of rat weight. Hepatic lipase levels in plasma were higher in the obese, but in liver, the higher activity was found in lean rats. No significant differences were found for lecithin-cholesterol acyltransferase activity, except when the levels in the HDL fraction were expressed per unit of protein weight, showing lower activity in the obese rats. In conclusion, the essentially maintained enzyme activities in obese rat tissues suggest that they cannot explain the deficient lipoproteins processing of obese rats, and, consequently their dislipidaemia.

Adipose Tissue↗
PubMed1995

Heparan sulfate proteoglycans are primarily responsible for the maintenance of enzyme activity, binding, and degradation of lipoprotein lipase in Chinese hamster ovary cells.

Various aspects of lipoprotein lipase (LPL) metabolism, including cell surface binding, degradation, and enzymatic activity, were compared between Chinese hamster ovary (CHO) cells and two distinct proteoglycan-deficient CHO cell lines. The contribution of low density lipoprotein receptor-related protein in binding LPL was also analyzed by the use of a 39-kDa receptor-associated protein expressed as a glutathione S-transferase fusion protein (GST-RAP). Equilibrium binding data with 125I-LPL revealed the presence of a class of high affinity binding sites with a KD of 7.8 nM in CHO cells, whereas no high affinity binding was observed for proteoglycan-deficient cells. The high affinity binding of LPL in CHO cells appeared to be concentrated in cell surface projections and was not effectively inhibited by GST-RAP. Moreover, degradation of endogenous and exogenous LPL was significantly greater in control CHO cells than in proteoglycan-deficient cells. Degradation of LPL in CHO cells was not affected by GST-RAP, suggesting that proteoglycans and not low density lipoprotein receptor-related protein are responsible for the majority of binding and degradation of LPL in these cells. Our data also show that proteoglycan binding is not essential for the assembly of active LPL homodimers, although proteoglycan binding controls the distribution of LPL activity. Furthermore, LPL produced by CHO cells was more stable than LPL produced by proteoglycan-deficient cells.

Animals↗
PubMed1990

Phenotypic expression of heterozygous lipoprotein lipase deficiency in the extended pedigree of a proband homozygous for a missense mutation.

Familial lipoprotein lipase (LPL) deficiency is a rare genetic disorder accompanied by well-characterized manifestations. The phenotypic expression of heterozygous LPL deficiency has not been so clearly defined. We studied the pedigree of a proband known to be homozygous for a mutation resulting in nonfunctional LPL. Hybridization of DNA from 126 members with allele-specific probes detected 29 carriers of the mutant allele. Adipose tissue LPL activity, measured previously, was reduced by 50% in carriers, but did not reliably distinguish them from noncarriers. Carriers were prone to the expression of a form of familial hypertriglyceridemia characterized by increased plasma triglyceride, VLDL cholesterol and apolipoprotein B, and decreased LDL and HDL cholesterol concentrations. These manifestations were age modulated, with conspicuous differences between carriers and noncarriers observed only after age 40. Several noncarriers exhibited similar lipid abnormalities, but without the inverse relationship between VLDL cholesterol and LDL cholesterol noted among carriers. In addition to age and carrier status, the potentially reversible conditions, obesity, hyperinsulinemia and lipid-raising drug use were contributory. Thus heterozygous lipoprotein lipase deficiency, together with age-related influences, may account for a form of familial hypertriglyceridemia.

Adipose Tissue↗
PubMed2003

Plasma lipoprotein lipase, hepatic lipase activities, VLDL, LDL compositions at different times of hemodialysis.

The effects of hemodialysis duration (HD) on lipoprotein lipase (LPL) and hepatic lipase (HL) activities and very low density lipoprotein (VLDL), low density lipoproteins (LDL) amounts and compositions were investigated in 58 patients, divided according to HD: GI: under 1 year, GII: 1-5 years, GIII: 5-13 years. HL and LPL activities were reduced in GIII versus GI (P<0.01) and 47% of GIII patients had negligible HL activity. LPL and HL activities were correlated with HD (r=-0.80, P<0.001). Apo C-III concentrations were correlated with HD (r=0.58, P<0.05). Compared with controls, triacylglycerols (TG) were increased in GI, GII (P<0.01) and GIII (P<0.001), and were correlated with HD (r=0.75, P<0.05). VLDL amounts and VLDL-cholesteryl esters (CE) were enhanced in GIII versus GI and GII (P<0.05). VLDL-TG and VLDL-phospholipids (PL) were correlated with HD (r=0.60, P<0.05). LDL-apolipoproteins and unesterified cholesterol (UC) were increased in GII versus GI (P<0.05) and in GIII versus GII and GI (P<0.01). LDL-PLs were decreased in GIII versus GI (P<0.05). Compared with controls, LDL-TGs were higher in GI and GII (P<0.01) and in GIII (P<0.05). Long-term treatment with acetate hemodialysis using cuprophane membrane does not improve lipolytic activity decrease and lipoprotein alterations generated by chronic renal failure (CRF).

Adult↗
PubMed2000

A newly identified lipoprotein lipase (LPL) gene mutation (F270L) in a Japanese patient with familial LPL deficiency.

We have systematically investigated the molecular defects resulting in a primary lipoprotein lipase (LPL) deficiency in a Japanese male infant (proband SH) with fasting hyperchylomicronemia. Neither LPL activity nor immunoreactive LPL mass was detected in pre- or postheparin plasma from proband SH. DNA sequence analysis of the LPL gene of proband SH revealed homozygosity for a novel missense mutation of F270L (Phe(270)-->Leu/TTT(1065)-->TTG) in exon 6. The function of the mutant F270L LPL was determined by both biochemical and immunocytochemical studies. In vitro expression experiments on the mutant F270L LPL cDNA in COS-1 cells demonstrated that the mutant LPL protein was synthesized as a catalytically inactive form and its total amount was almost equal to that of the normal LPL. Moreover, the synthesized mutant LPL was non-releasable by heparin because the intracellular transport of the mutant LPL to the cell surface - by which normal LPL becomes heparin-releasable - was impaired due to the abnormal structure of the mutant LPL protein. These findings explain the failure to detect LPL activities and masses in pre- and postheparin plasma of the proband. The mutant F270L allele generated an XcmI restriction enzyme site in exon 6 of the LPL gene. The carrier status of F270L in the proband's family members was examined by digestion with XcmI. The proband was ascertained to be homozygous for the F270L mutation and his parents and sister were all heterozygous. The LPL activities and masses of the parents and the sister (carriers) were half or less than half of the control values. Regarding the phenotype of the carriers, the mother with a sign of hyperinsulinemia manifested hypertriglyceridemia (type IV hyperlipoproteinemia), whereas the healthy father and the sister were normolipidemic. Hyperinsulinemia may be a strong determinant of hypertriglyceridemia in subjects with heterozygous LPL deficiency.

Alleles↗
PubMed2006

A polymorphism in lipoprotein lipase affects the severity of Alzheimer's disease pathophysiology.

Emerging evidences indicate a role for lipoprotein lipase (LPL) in degenerative states. Genetic variations in the LPL gene were previously associated to lipid imbalance and coronary artery disease (CAD) risk and severity, a condition that shares pathological features with common Alzheimer's disease (AD). To evaluate whether these genetic variations associate with the risk and pathophysiology of common AD, autopsy-confirmed patients (242 controls, 153 AD) were genotyped for a PvuII single nucleotide polymorphism (SNP; rs285; referred to as the P+ allele) of LPL. Brain LPL mRNA levels, cholesterol levels, amyloid concentration, senile plaques and neurofibrillary tangles density counts were measured and contrasted with specific LPL genotypes. When adjusted for age and sex, homozygosity for the P+ allele resulted in an odds ratio of 2.3 for the risk of developing AD. More importantly, we report that the presence of the P+ allele of LPL significantly affects its mRNA expression level (n = 51; P = 0.026), brain tissue cholesterol levels (n = 55; P = 0.0013), neurofibrillary tangles (n = 52; P = 0.025) and senile plaque (n = 52; P = 0.022) densities. These results indicate that a common polymorphism in the lipoprotein lipase gene modulates the risk level for sporadic AD in the eastern Canadian population but more importantly, indirectly modulates the pathophysiology of the brain in autopsy-confirmed cases.

Aged↗
PubMed1980

Evidence against the involvement of cyclic GMP in the insulin-stimulation of lipoprotein lipase activity in fat cells.

Under in vitro experimental conditions in which insulin increases adipose tissue lipoprotein lipase, cyclic GMP or dibutyryl cyclic GMP has no effect on this enzyme in rat adipose tissue fragments, or on either the intra- or extracellular forms of this enzyme in isolated fat cells. These results do not support the involvement of cyclic GMP in the insulin-stimulation of lipoprotein lipase in adipose tissue.

Adipose Tissue↗
PubMed2002

Identification of factors regulating lipoprotein lipase catalyzed hydrolysis in rats with the aid of monoacid-rich lipoprotein preparations(1).

To identify the substrate specificity and regulatory factors in lipoprotein lipase (LPL) catalyzed hydrolysis of triacylglycerol-rich lipoprotein, monoacid-rich lipoproteins were used to study the kinetic parameters of LPL. Feeding growing rats with diets rich in palmitic acid (16:0), oleic acid (18:1) or linoleic acid (18:2) for 10 days increased the corresponding acid content in the triacylglycerols of the lipoproteins. Force-feeding the monoacid-rich triacylglycerols, particularly 16:0 or 18:1, increased the respective fatty acid content in both chylomicrons and VLDLs. Major apolipoproteins and lipid compositions were essentially similar among all lipoproteins differing in monoacid species, except for apo A-IV. The Vmax of LPL for 16:0-rich chylomicrons and VLDLs were higher than for 18:1- or 18:2-rich lipoproteins. Order parameter (S), an indicator of the surface fluidity of lipoproteins, decreased with the chain length and unsaturation of monoacid in similar manner as the Vmax. The Vmax of LPL increased linearly (P < 0.05) with an increase in either the palmitic acid content of the lipoprotein triacylglycerols or order parameter (S) of the lipoproteins. The order parameter (S) and Vmax of LPL were higher in 16:0 triacylglycerol emulsions with apo B than with 18:1 or 18:2 triacylglycerols. The apo A-IV in triacylglycerol emulsions stimulated Vmax of LPLs in the presence of apo B and apo C-II. The binding of apo A-IV to 16:0 triacylglycerol emulsions was higher than to other triacylglycerol emulsions. These findings suggest that lipoprotein catalysis by LPL is modulated by the 16:0 level in the lipoprotein triacylglycerol, which affects the surface fluidity and apo A-IV content of lipoproteins.

Journal Article↗
PubMed1998

Lipoprotein lipase and the disposition of dietary fatty acids.

Lipoprotein lipase (EC 3.1.1.34; LPL) is a key enzyme regulating the disposal of lipid fuels in the body. It is expressed in a number of peripheral tissues including adipose tissue, skeletal and cardiac muscle and mammary gland. Its role is to hydrolyse triacylglycerol (TG) circulating in the TG-rich lipoprotein particles in order to deliver fatty acids to the tissue. It appears to act preferentially on chylomicron-TG, and therefore may play a particularly important role in regulating the disposition of dietary fatty acids. LPL activity is regulated according to nutritional state in a tissue-specific manner according to the needs of the tissue for fatty acids. For instance, it is highly active in lactating mammary gland; in white adipose tissue it is activated in the fed state and suppressed during fasting, whereas the reverse is true in muscle. Such observations have led to the view of LPL as a metabolic gatekeeper, especially for dietary fatty acids. However, closer inspection of its action in white adipose tissue reveals that this picture is only partially true. Normal fat deposition in adipose tissue can occur in the complete absence of LPL, and conversely, if LPL activity is increased by pharmacological means, increased fat storage does not necessarily follow. LPL appears to act as one member of a series of metabolic steps which are regulated in a highly coordinated manner. In white adipose tissue, it is clear that there is a major locus of control of fatty acid disposition downstream from LPL. This involves regulation of the pathway of fatty acid uptake and esterification, and appears to be regulated by a number of factors including insulin, acylation-stimulating protein and possibly leptin.

Adipose Tissue↗
PubMed1998

Suppression of carcass weight loss in cachexia in rats bearing Leydig cell tumor by the novel compound NO-1886, a lipoprotein lipase activator.

The Leydig cell tumor has been reported to produce tumor necrosis factor (TNF) and induce cachexia in rats. TNF is thought to reduce lipoprotein lipase (LPL) activity, decrease fat deposits, induce emaciation, and worsen cachexia. Therefore, we thought emaciation might be prevented and thus cachexia improved by increasing LPL activity. We administered NO-1886, a lipoprotein lipase activator, to rats bearing Leydig cell tumor and observed its effect on improving the cachexia induced by the tumor. In Leydig cell tumor-bearing rats, the emaciation progressed after tumor inoculation and the general condition worsened daily. Plasma levels of total protein, albumin, and glucose, which are biological parameters of malnutrition, were found to decrease soon after tumor inoculation in tumor-bearing rats. In contrast, rats given NO-1886 showed less malnutrition than tumor-bearing rats. LPL activity of rat adipose tissue was decreased, the weight of adipose tissue was decreased, carcass weight was reduced, and food consumption was decreased after Leydig cell tumor inoculation. NO-1886 increased adipose tissue LPL activity and suppressed the decrease in the weight of adipose tissue, carcass weight, and food consumption due to cachexia without influencing tumor growth. The present results suggest that the novel compound NO-1886 may suppress carcass weight loss in rats bearing Leydig cell tumor by suppressing the decrease in food consumption and LPL activity.

Adipose Tissue↗
PubMed1991

Effects of transforming growth factor beta 1 and basic fibroblast growth factor on lipoprotein lipase activity in primary cultures of chicken (Gallus domesticus) adipocyte precursors.

1. The effect of TGF-beta and bFGF on lipoprotein lipase activity in chicken adipocyte precursors was investigated. 2. Lipoprotein lipase activity was reduced by up to 80% by incubation with TGF-beta whereas bFGF had no effect. 3. Contrary to that found with the 3T3-L1 preadipocyte cell line it was not necessary for TGF-beta to be present prior to the start of differentiation in order to be effective. 4. Incubation of adipocyte precursors with actinomycin D abolished the effect of TGF-beta suggesting that synthesis of a protein effector is required. 5. These results indicate differences in responsiveness to TGF-beta and bFGF between primary chicken adipocyte precursors and some preadipocyte cell lines.

Adipose Tissue↗
PubMed1978

Lipoprotein lipase of cultured mesenchymal rat heart cells. I. Synthesis, secretion and releasability by heparin.

Cell suspensions prepared from rat hearts were separated by replating into F1, F2 and M cultures, and cultured for 3--11 days. Lipoprotein lipase activity was highest in the F1 cultures which consisted mainly of non-beating, mesenchymal cells. The enzyme activity was released into the medium only after addition of heparin. The release occurred by an initial rapid phase and a continuous slow phase. Both the rapid and the slow release of enzyme activity by heparin were inhibited by about 70% after a 4 h pretreatment with colchicine. Thus, it seems that the vesicular transport is responsible for the translocation of lipoprotein lipase to the cell surface also during the slow process of release. The residual activity in the colchicine treated cultures was higher than in the controls indicating that no inhibition of enzyme synthesis occurred. The slow phase of enzyme release continued also after removal of heparin from the medium but was reduced markedly when protein synthesis was inhibited by cycloheximide. Thus the increase in total enzyme activity encountered after exposure to heparin resulted from stimulation of new enzyme synthesis. The half-time of lipoprotein lipase in the F1 cultures was 35 min and full restoration of enzyme activity was found 60 min after complete removal of cycloheximide from the system. These data indicate that the culture system can be used to study regulation of new enzyme synthesis and its turnover.

Animals↗