Postheparin Plasma Hepatic Lipase Activity Research Articles

In vivo structure-function studies of human hepatic lipase: the catalytic function rescues the lean phenotype of HL-deficient (hl-/-) mice.

The lean body weight phenotype of hepatic lipase (HL)–deficient mice (hl−/−) suggests that HL is required for normal weight gain, but the underlying mechanisms are unknown. HL plays a unique role in lipoprotein metabolism performing bridging as well as catalytic functions, either of which could participate in energy homeostasis. To determine if both the catalytic and bridging functions or the catalytic function alone are required for the effect of HL on body weight, we studied (hl−/−) mice that transgenically express physiologic levels of human (h)HL (with catalytic and bridging functions) or a catalytically-inactive (ci)HL variant (with bridging function only) in which the catalytic Serine 145 was mutated to Alanine. As expected, HL activity in postheparin plasma was restored to physiologic levels only in hHL-transgenic mice (hl−/−hHL). During high-fat diet feeding, hHL-transgenic mice exhibited increased body weight gain and body adiposity relative to hl−/−ciHL mice. A similar, albeit less robust effect was observed in female hHL-transgenic relative to hl−/−ciHL mice. To delineate the basis for this effect, we determined cumulative food intake and measured energy expenditure using calorimetry. Interestingly, in both genders, food intake was 5–10% higher in hl−/−hHL mice relative to hl−/−ciHL controls. Similarly, energy expenditure was ∼10% lower in HL-transgenic mice after adjusting for differences in total body weight. Our results demonstrate that (1) the catalytic function of HL is required to rescue the lean body weight phenotype of hl−/− mice; (2) this effect involves complementary changes in both sides of the energy balance equation; and (3) the bridging function alone is insufficient to rescue the lean phenotype of hl−/−ciHL mice.

Hepatic lipase activity is decreased in Japanese patients with type III hyperlipoproteinemia

BackgroundType III hyperlipoproteinemia (HLP), a disorder associated with a high incidence of premature cardiovascular diseases, is characterized by the accumulation of remnant lipoproteins in the plasma. The primary genetic defect in patients with type III HLP is the presence of apolipoprotein E2 (apoE2), an isoform of apoE, and accumulation of remnant lipoproteins in the plasma has been thought to be attributable to the presence of apoE2, which bind poorly to low density lipoprotein receptors, resulting in defective remnant lipoprotein clearance. On the other hand, the activity of hepatic lipase (HL), the enzyme that plays a pivotal role in the removal of remnant lipoproteins, in type III HLP has not been investigated. MethodsWe examined post-heparin plasma lipoprotein lipase (LPL) and HL activities in 7 patients with type III HLP. The activities of HL and LPL in post-heparin plasma were measured separately by an immunochemical method using antiserum specifically directed against HL. ResultsThe post-heparin plasma HL activity was significantly reduced, while the LPL activity was normal. ConclusionsReduced HL activity may account, at least in part, for the accumulation of remnant lipoproteins in the plasma, a characteristic feature of type III HLP.

MS407 REDUCED MYOCARDIAL GLUCOSE UTILIZATION AFTER FASTING AND HEPARIN INJECTION IN RATS

Type III hyperlipoproteinemia (HLP), a disorder associated with a high incidence of premature cardiovascular diseases, is characterized by the accumulation of remnant lipoproteins in the plasma. The primary genetic defect in patients with type III HLP is the presence of apolipoprotein E2 (apoE2), an isoform of apoE, and accumulation of remnant lipoproteins in the plasma has been thought to be attributable to the presence of apoE2, which bind poorly to low density lipoprotein receptors, resulting in defective remnant lipoprotein clearance. On the other hand, the activity of hepatic lipase (HL), the enzyme that plays a pivotal role in the removal of remnant lipoproteins, in type III HLP has not been investigated.We examined post-heparin plasma lipoprotein lipase (LPL) and HL activities in 7 patients with type III HLP. The activities of HL and LPL in post-heparin plasma were measured separately by an immunochemical method using antiserum specifically directed against HL.The post-heparin plasma HL activity was significantly reduced, while the LPL activity was normal.Reduced HL activity may account, at least in part, for the accumulation of remnant lipoproteins in the plasma, a characteristic feature of type III HLP.

Acrolein consumption induces systemic dyslipidemia and lipoprotein modification

Aldehydes such as acrolein are ubiquitous pollutants present in automobile exhaust, cigarette, wood, and coal smoke. Such aldehydes are also constituents of several food substances and are present in drinking water, irrigation canals, and effluents from manufacturing plants. Oral intake represents the most significant source of exposure to acrolein and related aldehydes. To study the effects of short-term oral exposure to acrolein on lipoprotein levels and metabolism, adult mice were gavage-fed 0.1 to 5 mg acrolein/kg bwt and changes in plasma lipoproteins were assessed. Changes in hepatic gene expression related to lipid metabolism and cytokines were examined by qRT-PCR analysis. Acrolein feeding did not affect body weight, blood urea nitrogen, plasma creatinine, electrolytes, cytokines or liver enzymes, but increased plasma cholesterol and triglycerides. Similar results were obtained with apoE-null mice. Plasma lipoproteins from acrolein-fed mice showed altered electrophoretic mobility on agarose gels. Chromatographic analysis revealed elevated VLDL cholesterol, phospholipids, and triglycerides levels with little change in LDL or HDL. NMR analysis indicated shifts from small to large VLDL and from large to medium-small LDL with no change in the size of HDL particles. Increased plasma VLDL was associated with a significant decrease in post-heparin plasma hepatic lipase activity and a decrease in hepatic expression of hepatic lipase. These observations suggest that oral exposure to acrolein could induce or exacerbate systemic dyslipidemia and thereby contribute to cardiovascular disease risk.

Cyclosporine A and Rapamycin induce in vitro cholesteryl ester transfer protein activity, and suppress lipoprotein lipase activity in human plasma

Purpose Cyclosporine A (CsA), Rapamycin (RAPA), Tacrolimus (FK-506) and Mycophenolate mofetil (MMF) are immunosuppressants that are widely used in solid organ transplant patients. However, some of these drugs have been reported to cause dyslipidemia in patients. Our aim was to determine the effects of these drugs on in vitro cholesteryl ester transfer protein (CETP), hepatic lipase (HL) and lipoprotein lipase (LPL) activity within human plasma. Methods We measured CETP activity in human normolipidemic plasma with and without drug treatment, by measuring the incorporation of labeled cholesteryl ester into lipoproteins. To further confirm the result, we also measured recombinant CETP (rCETP) activity with and without drug treatment. We measured HL and LPL activity in post-heparin normal human plasma in the presence and absence of the drugs by measuring the release of fatty acids from radiolabeled triolein. Results We found an increase in CETP activity in human normolipidemic plasma and rCETP treated with CsA and RAPA. By contrast, CETP activity was not altered significantly in the presence of FK-506 and MMF. LPL activity in post-heparin normal human plasma was suppressed following the co-incubation with CsA, RAPA, FK-506 or MMF whereas HL activity remained unaffected. Conclusions The increase in CETP activity and suppression in LPL activity following CsA and RAPA treatment observed in the present study may be associated with elevated LDL cholesterol levels and hypertriglyceridemia seen in patients administered these drugs.

PO2-30 APO A-I ISOFORMS DISPLAY DIFFERENT EFFICIENCIES IN INDUCING ABCA1-DEPENDENT CHOLESTEROL EFFLUX FROM MOUSE PERITONEAL MACROPHAGES

The sequence of alterations in the concentration and composition of different plasma lipoproteins following alcohol intake is not known. We therefore monitored the concentrations of cholesterol, triglycerides, phospholipids, and proteins in the major lipoprotein fractions (VLDL, LDL, HDL2, and HDL3) in ten nonalcoholic healthy male volunteers who were given 5.5 g of alcohol per kilogram of body weight during 212days (a weekend). In addition, lipoprotein lipase activity was measured in post-heparin plasma and in adipose tissue and hepatic lipase activity was measured in post-heparin plasma before and after the experiment. In a separate control experiment, the same subjects received meals and liquids without alcohol. Blood alcohol levels remained below 1.5 g/L. Alcohol caused a progressive increase in the fasting VLDL triglyceride and phospholipid concentrations, both of which were doubled during the experiment (P < 0.001). In contrast, the VLDL cholesterol levels remained unchanged until the third morning, when there was a slight increase. The LDL triglyceride and phospholipid concentrations also rose without simultaneous changes in the LDL cholesterol concentration. Consistent with these changes, the HDL cholesterol concentration showed no response to alcohol during the experiment, but the HDL phospholipid level rose from 76 to 99 mg/dL (P < 0.001). This was reflected as an increase in the HDL2 concentration from 124 to 158 mg/dL (P < 0.01), whereas no change occurred in the HDL3 level. The increment of HDL2 concentration was due to a rise of its triglycerides, phospholipids, and apoproteins A-I and A-II but not to a rise of cholesterol. Thus, the VLDL, LDL and HDL2 fractions all became relatively depleted of cholesterol during alcohol intake. Alcohol potentiated the postprandial rise of plasma triglycerides with an increase in triglyceride concentrations in all lipoprotein fractions. During alcohol intake the HDL2 concentration increased postprandially (P < 0.05) whereas the HDL3 concentration decreased slightly, the fall being accounted for by a decrease in the HDL3 cholesterol level. The lipoprotein lipase activity of adipose tissue increased by an average of 2.3-fold (P < 0.01) over the alcohol-intake period, whereas the postheparin plasma hepatic lipase activity fell by 28% (P < 0.01). The results support the hypothesis that alcohol initially stimulates the secretion of VLDL particles that contain less cholesterol than “normal” VLDL. As a consequence of this and of a concomitant induction of lipoprotein lipase, alcohol intake is followed by an accelerated transfer of the VLDL catabolic products to HDL and by a subsequent rise in the levels of HDL2 triglycerides, phospholipids, and apoproteins but not of cholesterol. The suppression of hepatic lipase activity by alcohol may contribute further to the rise of HDL2 phospholipids. It thus appears that the increase of HDL cholesterol is a late phenomenon being expressed only after more prolonged use of alcohol.

PO2-33 THE INCREASE OF APOA-V DURING POSTPRANDIAL LIPEMIA FOLLOWS THE RESPONSE OF TRIGLYCERIDE-RICH LIPOPROTEINS (TRL) IN TYPE 2 DIABETES

The sequence of alterations in the concentration and composition of different plasma lipoproteins following alcohol intake is not known. We therefore monitored the concentrations of cholesterol, triglycerides, phospholipids, and proteins in the major lipoprotein fractions (VLDL, LDL, HDL2, and HDL3) in ten nonalcoholic healthy male volunteers who were given 5.5 g of alcohol per kilogram of body weight during 212days (a weekend). In addition, lipoprotein lipase activity was measured in post-heparin plasma and in adipose tissue and hepatic lipase activity was measured in post-heparin plasma before and after the experiment. In a separate control experiment, the same subjects received meals and liquids without alcohol. Blood alcohol levels remained below 1.5 g/L. Alcohol caused a progressive increase in the fasting VLDL triglyceride and phospholipid concentrations, both of which were doubled during the experiment (P < 0.001). In contrast, the VLDL cholesterol levels remained unchanged until the third morning, when there was a slight increase. The LDL triglyceride and phospholipid concentrations also rose without simultaneous changes in the LDL cholesterol concentration. Consistent with these changes, the HDL cholesterol concentration showed no response to alcohol during the experiment, but the HDL phospholipid level rose from 76 to 99 mg/dL (P < 0.001). This was reflected as an increase in the HDL2 concentration from 124 to 158 mg/dL (P < 0.01), whereas no change occurred in the HDL3 level. The increment of HDL2 concentration was due to a rise of its triglycerides, phospholipids, and apoproteins A-I and A-II but not to a rise of cholesterol. Thus, the VLDL, LDL and HDL2 fractions all became relatively depleted of cholesterol during alcohol intake. Alcohol potentiated the postprandial rise of plasma triglycerides with an increase in triglyceride concentrations in all lipoprotein fractions. During alcohol intake the HDL2 concentration increased postprandially (P < 0.05) whereas the HDL3 concentration decreased slightly, the fall being accounted for by a decrease in the HDL3 cholesterol level. The lipoprotein lipase activity of adipose tissue increased by an average of 2.3-fold (P < 0.01) over the alcohol-intake period, whereas the postheparin plasma hepatic lipase activity fell by 28% (P < 0.01). The results support the hypothesis that alcohol initially stimulates the secretion of VLDL particles that contain less cholesterol than “normal” VLDL. As a consequence of this and of a concomitant induction of lipoprotein lipase, alcohol intake is followed by an accelerated transfer of the VLDL catabolic products to HDL and by a subsequent rise in the levels of HDL2 triglycerides, phospholipids, and apoproteins but not of cholesterol. The suppression of hepatic lipase activity by alcohol may contribute further to the rise of HDL2 phospholipids. It thus appears that the increase of HDL cholesterol is a late phenomenon being expressed only after more prolonged use of alcohol.

The hepatic lipase gene C‐480T polymorphism in the development of early coronary atherosclerosis: the Helsinki Sudden Death Study

The T allele of the hepatic lipase (HL) C-480T polymorphism was previously found to be associated with lower post-heparin plasma HL activity, atherosclerosis and risk of coronary artery disease. We studied the association of HL C-480T polymorphism with the extent of atherosclerosis at vessel-wall level in an autopsy series of middle-aged men. An autopsy cohort of 700 Caucasian Finnish men aged 33-70 years (mean 53 years), which comprised two autopsy series, collected 10 years apart during 1981-82 and 1991-92, were analysed. Areas of coronary wall covered with fatty streaks and fibrotic and complicated lesions were measured using computer-assisted planimetry and related to HL C-480T genotypes (CC, CT, and TT). There was a significant age-by-genotype interaction on the mean percentage area of fatty streaks (P = 0.01). The HL C-480T polymorphism was a significant explanatory factor for fatty streak area in men under 53 years of age with or without age, body mass index, hypertension, diabetes, smoking, alcohol consumption, apolipoprotein E genotype, and series number as covariates. Men carrying the TT genotype had two times larger areas of fatty streaks compared to the CC carriers (8.8% vs. 4.3%, P = 0.009). However, this association disappeared in men over 53 years. The areas of more advanced atherosclerotic lesions did not vary significantly among the genotype groups. Our results suggest that the HL C-480T polymorphism affects the formation of early coronary atherosclerotic lesions in men in their early middle age.

A novel method for measuring human hepatic lipase activity in postheparin plasma

The objective of this study was to establish a hepatic lipase (HL) assay method that can be applied to automatic clinical analyzers. Seventy-four hyperlipidemic subjects (men/women 45/29) were recruited. Lipase activity was assayed measuring the increase in absorbance at 546 nm due to quinonediimine dye production. Reaction mixture R-1 contained 50 mM Tris-HCl (pH 9.5), 0.5 mM glycerol-1,2-dioleate, 0.4% (unless otherwise noted) polyoxyethylene-nonylphenylether, 3 mM ATP, 3 mM MgCl(2), 1.5 mM CaCl(2), monoacylglycerol-specific lipase, glycerol kinase, glycerol-3-phosphate oxidase, 0.075% N,N-bis-(4-sulfobutyl)-3-methylaniline-2 Na, peroxidase, ascorbic acid oxidase. Reaction mixture R-2 contained 50 mM Tris-HCl (pH9.5), 0.15% 4-aminoantypirine. Automated assay for activity was performed with a Model 7080 Hitachi analyzer. In the lipase assay, 160 microl of R-1 was incubated at 37 degrees C with 3 microl of samples for 5 min, and 80 microl of R-2 was added. Within-run coefficient of variations was 0.9-1.0%. Calibration curve of lipase activity was linear (r = 0.999) between 0 and 320 U/l. Analytical recoveries of purified HL added to plasma were 96.6-99.8%. HL activity in postheparin plasma measured in this method had a closer correlation with HL mass by a sandwich ELISA (r = 0.888, P < 0.0001) than those in the conventional method using [(14)C-]triolein (r = 0.730, P < 0.0001). This assay method for HL activity can be applied to an automatic clinical analyzer.

Low Plasma Adiponectin Levels Are Associated With Increased Hepatic Lipase Activity In Vivo: Response to Schneider et al.

Recently, close attention has been given to the relationships between plasma adiponectin levels and lipolytic enzymes such as hepatic lipase and lipoprotein lipase activities in an effort to understand the possible mechanism of hyperlipidemia in low adiponectin. The cross-sectional study by Schneider et al. (1) has concluded that postheparin plasma hepatic lipase activity is inversely associated with plasma …

Low Plasma Adiponectin Levels Are Associated With Increased Hepatic Lipase Activity In Vivo

Recently, close attention has been given to the relationships between plasma adiponectin levels and lipolytic enzymes such as hepatic lipase and lipoprotein lipase activities in an effort to understand the possible mechanism of hyperlipidemia in low adiponectin. The cross-sectional study by Schneider et al. (1) has concluded that postheparin plasma hepatic lipase activity is inversely associated with plasma …

Low Plasma Adiponectin Levels Are Associated With Increased Hepatic Lipase Activity In Vivo

Hepatic lipase plays a key role in hydrolyzing triglycerides and phospholipids present in circulating plasma lipoproteins. Plasma hepatic lipase activity is known to be regulated by several hormonal and metabolic factors, but hepatic lipase responsiveness to insulin is still controversial. Hypoadiponectinemia is known to be associated with insulin resistance, diabetes, and obesity. These conditions are often characterized by high plasma triglyceride and low HDL cholesterol levels, and they have been shown to be associated with high plasma hepatic lipase activity. We therefore raised the question whether adiponectin may be associated with plasma hepatic lipase activity in vivo. We measured plasma adiponectin and postheparin hepatic lipase activity in 206 nondiabetic men and in a second group of 110 patients with type 2 diabetes. The correlation of these parameters with markers of insulin resistance and systemic inflammation was investigated. In nondiabetic patients, adiponectin levels were significantly inversely correlated with plasma hepatic lipase activity (r = -0.4, P < 0.01). These results were confirmed in the group of patients with type 2 diabetes (r = -0.32, P = 0.004). Multivariate analysis revealed that adiponectin was the strongest factor influencing hepatic lipase activity. The association was independent of age, sex, BMI, plasma triglycerides, insulin, HDL cholesterol, and high-sensitivity C-reactive protein and accounted for approximately 10 and 12% of the variation in hepatic lipase activity in the two different patient cohorts, respectively. These results demonstrate for the first time a significant inverse association between adiponectin and postheparin plasma hepatic lipase activity that is independent of other factors such as markers of insulin resistance or inflammation. Therefore, adiponectin, rather than insulin, may represent an important factor contributing to the regulation of hepatic lipase activity in both nondiabetic individuals and patients with type 2 diabetes. The effect of adiponectin on hepatic lipase activity may also help to explain the HDL cholesterol-elevating action of adiponectin.

Hepatic Lipase mRNA, Protein, and Plasma Enzyme Activity Is Increased in the Insulin-Resistant, Fructose-Fed Syrian Golden Hamster and Is Partially Normalized by the Insulin Sensitizer Rosiglitazone

Postheparin plasma hepatic lipase (HL) activity has been shown to correlate with features of the metabolic syndrome and type 2 diabetes in humans. We examined HL postheparin plasma enzyme activity, hepatocyte mRNA, and protein mass in the insulin-resistant, fructose-fed Syrian golden hamster, and the response of the insulin-sensitizing peroxisome proliferator-activated receptor-gamma agonist rosiglitazone. Male Syrian golden hamsters were treated for 5 weeks with 1) normal diet (DIET group), 2) 60% fructose diet (FRUC group), or 3) 60% fructose and rosiglitazone (20 mmol . kg(-1) . day(-1)) (FRUC+RSG group). Hepatocyte HL mRNA, protein mass, and postheparin plasma HL activity were increased in FRUC compared with DIET hamsters. FRUC+RSG hamsters had partial normalization of HL mRNA, mass, and activity. There was a shift in the size of LDL particles from large to small in FRUC animals and a shift back to large LDL size in FRUC+RSG. This is the first demonstration that HL hepatocyte mRNA, mass, and plasma enzymatic activity increase concomitantly with induction of an insulin-resistant state and can be partially normalized by treatment with an insulin sensitizer. The increase in HL in insulin-resistant states may play an important role in the typical dyslipidemia of these conditions, and reduction of HL could explain some of the beneficial effects of insulin sensitizers on the plasma lipid profile.

Effect of the −514 polymorphism in the hepatic lipase gene on postheparin plasma hepatic lipase activity in chinese subjects

Effect of the −514 polymorphism in the hepatic lipase gene on postheparin plasma hepatic lipase activity in chinese subjects

Functional characterization of 4 polymorphisms in promoter region of hepatic lipase gene.

Hepatic lipase (HL) is a lipolytic enzyme involved in the metabolism of plasma lipoproteins, especially high density lipoproteins. Association studies have provided strong evidence for relations of common mutations in the promoter region of the HL gene to postheparin plasma HL activity and the plasma high density lipoprotein cholesterol concentration, but the functional relevance of these polymorphisms has not been evaluated to date. We analyzed the physiological significance of 4 common polymorphisms (-250G/A, -514C/T, -710T/C, and -763A/G, all in strong linkage disequilibrium) in the promoter of the HL gene by use of electrophoretic mobility shift assays and transient transfection studies in HepG2 cells. No consistent evidence was found for a significant contribution of any of these polymorphisms to the basal rate of transcription of the HL gene. These data suggest that the 4 polymorphisms in the promoter region of the HL gene are in linkage disequilibrium with >/=1 as-yet-unknown functional polymorphisms in the HL gene locus with a significant effect on HL metabolism and/or enzymatic activity.

Hepatic lipase (LIPC) promoter polymorphism in men with coronary artery disease. Allele frequency and effects on hepatic lipase activity and plasma HDL-C concentrations.

Hepatic lipase is an important determinant of plasma HDL concentration and LDL subclass distribution and may therefore influence susceptibility to coronary artery disease (CAD). To assess the effect of genetic variation in hepatic lipase activity on CAD susceptibility, we determined the frequency of the -514T allele of hepatic lipase in white men with CAD and in controls who did not have CAD. In men with CAD, postheparin plasma hepatic lipase activity was 15% to 20% lower in heterozygotes and 30% lower in homozygotes for the -514T allele. Allele frequencies were similar in cases and controls, however, and were consistent with Hardy-Weinberg expectation in both groups. This finding was confirmed in a second group comprising cases with premature symptomatic CAD and controls who were free of disease. These data indicate that a primary decrease in hepatic lipase activity of as much as 30% does not influence susceptibility to CAD in white men.

Three polymorphisms associated with low hepatic lipase activity are common in African Americans

We have shown previously that a hepatic lipase allele (designated –514T) is common among African Americans and contributes to low hepatic lipase activity in this population. To identify other hepatic lipase alleles associated with low hepatic lipase activity in this population, the coding region and intron–exon boundaries of the hepatic lipase gene were sequenced in 20 African American men with low hepatic lipase activity. Two polymorphisms (N193S and L334F) were associated with low post-heparin plasma hepatic lipase activity and were much more common in African Americans than in whites. This finding, together with our previous data on the –514T allele, indicates that at least three different hepatic lipase polymorphisms associated with low hepatic lipase activity are common among African Americans. Analysis of hepatic lipase haplotypes revealed that 97% of African Americans have at least one hepatic lipase allele that is associated with low hepatic lipase activity.—Nie, L., S. Niu, G. L. Vega, L. T. Clark, A. Tang, S. M. Grundy, and J. C. Cohen. Three polymorphisms associated with low hepatic lipase activity are common in African Americans.

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 • h–1 •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.—Vega, G. L., L. T. Clark, A. Tang, S. Marcovina, S. M. Grundy, and J. C. Cohen. 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). J. Lipid Res. 1998. 39: 228–232.

Responses of HDL subclasses, Lp(A-I) and Lp(A-I:A-II) levels and lipolytic enzyme activities to continuous oral estrogen–progestin and transdermal estrogen with cyclic progestin regimens in postmenopausal women

Seventy postmenopausal women took part in the study. Subjects received either continuous oral 17 β-estradiol 2 mg/day combined with norethisterone acetate 1 mg/day (E2/NETA, Kliogest®) or transdermal treatment consisting of 28 day cycles with patches delivering 17 β-estradiol 50 μg/day (Estraderm®) combined with cyclic medroxyprogesterone acetate 10 mg/day (E2/MPA, Provera®), on days 17–28. At baseline the serum lipid and lipoprotein concentrations, composition and concentrations of high density lipoprotein (HDL) subclasses, lipoprotein (Lp)(AI) and Lp(A-I:A-II) levels were comparable in the two groups. In the E2/NETA group, after 12 months hormone replacement therapy (HRT), the HDL2 cholesterol concentration decreased by 17% ( P<0.01) and the HDL3 cholesterol remained unchanged. The concentrations of HDL2b, HDL2a and HDL3a were reduced by 30, 26 and 15%, respectively, P<0.001, and the cholesterol:triglyceride ratio decreased significantly in all HDL subclasses. Apolipoprotein (apo) A-I concentration decreased by 5% ( P<0.05), but apo A-II, Lp(A-I) and Lp(A-I:A-II) concentrations remained unchanged. In the E2/MPA group the HDL2 and HDL3 cholesterol levels were both reduced by 6% ( P<0.05) and the HDL3a, HDL3b and HDL3c concentrations decreased by 14, 12 and 17% during the E2/MPA phase compared with baseline ( P<0.01). No major changes in the composition of HDL subclasses occurred in the E2/MPA group during treatment. The apo A-I and Lp(A-I) levels were not changed, but apo A-II and Lp(A-I:A-II) concentrations decreased by 8 and 5%, P<0.001 and P<0.05, respectively. At 12 months the postheparin plasma hepatic lipase (HL) activity decreased only in the E2/NETA group (by 12%, P<0.05). The cholesteryl ester transfer protein (CETP) activity was not affected by either HRT regimen. The results of our study show that the 2 HRT regimens have multiple effects on HDL particles and HRT induced changes in HDL are not associated with changes in activities of lipolytic enzymes or CETP.

Heterozygous hepatic lipase deficiency, due to two missense mutations R186H and L334F, in the HL gene

Hepatic lipase (HL) is an endothelial enzyme involved in the metabolism of intermediate density lipoproteins (IDL) and high density lipoproteins (HDL) in plasma. In a Finnish pedigree consisting of 18 members belonging to three generations two missense mutations RI86H and L334F in exons 5 and 7 of the HL gene co-segregated with low post-heparin HL activity. Haplotype analysis of the HL gene in family members revealed a high degree of genetic variation and demonstrated that the two missense mutations reside on the same chromosome. In vitro site-directed mutagenesis and expression of the cDNA constructs in COS-1 cells revealed that the R186H mutation leads to a protein that is not secreted while the L334F mutation results in the production of a HL protein that is secreted but has only about 30% of wild type HL activity. Carriers of the mutated HL gene exhibited clearly reduced HL activity and mass in post-heparin plasma. Probably due to their heterozygous carrier status they had only moderate elevation of total triglycerides, IDL, and LDL-triglycerides. The LDL-particles were enriched in triglycerides and depleted of cholesterol. Also their HDL 2- and HDL 3-particles were enriched in triglycerides.