Two common mutations (D9N, N291S) in lipoprotein lipase: a cumulative analysis of their influence on plasma lipids and lipoproteins in men and women

We assessed the effect of two common mutations in the lipoprotein lipase gene (LPL), D9N and N291S, which have been shown to modulate plasma lipids in a wide spectrum of patients. A total of 1114 men and 1 144 women from the Framingham Offspring Study (FOS) were analyzed for these two LPL variants. Subsequently, the association with fasting plasma lipids and risk of coronary artery disease (CHD) was determined. We extended our study by calculating weighed means of lipids and lipoproteins in carriers and non-carriers for these LPL mutations in patients with genetic dyslipidemias, CHD patients and healthy controls. In the FOS sample, the D9N and N291S alleles were associated with lower high-density lipoprotein-cholesterol (HDL-C) (delta = - 0.07 mmol/ 1, p = 0.03) and a trend towards increased triglycerides (delta = 0.25 mmol/ 1, p = 0.07). In women, a trend towards the high triglyceride, low HDL-C phenotype was evident (delta = - 0.02 mmol/1 for HDL-C and delta = 0.14 mmol/l for triglycerides, respectively). Cumulative analysis of other studies of male carriers of the D9N and N291S revealed higher levels of triglycerides (D291N; 2.60(1.85) mmol/l vs. 1.62(1.18) mmol/l: p < 0.0001) (D9N; 1.94 (1.19) mmol/l vs. 1.74(1.17) mmol/l: p < 0.001) and lower HDL-C (N291S; 1.04(0.32) mmol/l vs. 1.15(0.28) mmol/l: p < 0.0001) (D9N; 1.08(0.24) mmol/l vs. 1.16(0.28) mmol/l: p < 0.0001). In females, results differed with higher TG levels (N291S; 1.70(0.99) mmol/l vs. 1.10(0.63) mmol/l: p < 0.001) (D9N; 1.08(0.76) mmol/l vs. 0.96(0.51) mmol/l: p < 0.01) and lower HDL-C levels (N291S; 1.27(0.33) mmol/l vs. 1.51(0.32) mmol/l: p < 0.0001); however, the HDL-C levels for D9N carriers were similar to non-carriers (D9N; 1.52(0.29) mmol/l vs. 1.53(0.35) mmol/l: p = 0.83). Our data provide evidence that common variants of the LPL gene are significant modulators of lipid and lipoprotein levels in both men and women.     

The Asn9 variant of lipoprotein lipase is associated with the — 93G promoter mutation and an increased risk of coronary artery disease

Two mutations in the lipoprotein lipase (LPL) gene, a T to G transition at position −93 of the proximal promoter region and an Asp9Asn substitution in exon 2, were examined in 762 Dutch males with angiographically-diagnosed coronary artery disease (CAD) and 296 healthy normolipidemic Dutch males. The two mutations exhibited strong linkage disequilibrium (D'=0.975). A significantly higher proportion of cases (4.86%) than controls (1.37%) carried the −93G/Asn9 allele (p=0.008). In the combined sample of cases and controls, adjusted mean plasma total cholesterol (TC) levels were significantly higher in −93G/Asn9 carriers (6.20±0.13 mmol/l) than in non-carriers (5.93±0.03 mmol/l; p=0.048), while mean high-density lipoprotein cholesterol (HDL-C) levels were lower in carriers (0.88±0.03 mmol/l) than in non-carriers (0.98±0.01 mmol/l; p=0.002). There was a trend towards higher triglyceride (TG) levels in carriers (1.96±0.14 mmol/l) compared with non-carriers (1.73±0.03 mmol/l) (p=0.08). Additionally, carrier frequencies in tertiles of TC, HDL-C, TG, and LPL activity, suggested an association of the −93G/Asn9 variant with higher TC and TG levels, and with lower HDL-C and LPL activity levels. Logistic regression revealed a significant odds ratio (OR) for the combined −93G/Asn9 genotype in CAD cases relative to controls (OR: 5.36; 95% CI: 1.57–18.24), with age, body mass index (BMI), smoking, and plasma total- and HDL-cholesterol levels included in the model. In conclusion, we show that the LPL Asp9Asn mutation is in non-random association with a T→G substitution at position −93 of the proximal promoter region and that the combined −93G/Asn9 genotype predisposes to decreased HDL-C levels and an increased risk of CAD.     

Identification of a common variant in the lipoprotein lipase gene in a large Utah kindred ascertained for coronary heart disease: the -93G/D9N variant predisposes to low HDL-C/high triglycerides

Defects in the lipoprotein lipase (LPL) gene are associated with dyslipidemia in the general population. Several rare mutations in the gene, as well as two common coding region polymorphisms, D9N and N291S, exhibit deleterious effects on circulating lipid levels. Using a linkage-based approach, we have identified a large Utah kindred segregating the D9N variant in the LPL gene. The kindred was ascertained for premature coronary heart disease and was expanded based on familial dyslipidemia. A genomic scan identified a region of linkage including LPL, and mutation screening identified the segregating variant. In the kindred, the variant shows high penetrance for a hypoalphalipoproteinemia phenotype, but is also associated with hypertriglyceridemia and elevated insulin levels. The strength of linkage was dependent on the combination of phenotype definition and model parameters, favoring the use of a MOD score approach. Most other studies of LPL have proceeded by mutation screening of randomly chosen individuals or selected affected probands; this is the first example identifying a segregating LPL mutation using direct linkage.     

Pseudodominance of lipoprotein lipase (LPL) deficiency due to a nonsense mutation (Tyr302>Term) in exon 6 of LPL gene in an Italian family from Sardinia (LPL(Olbia))

We analyzed the molecular defect in the lipoprotein lipase (LPL) gene of a young boy from Sardinia who had primary hyperchylomicronemia, pancreatitis, and a complete LPL deficiency in post-heparin plasma. Analysis of LPL gene was performed by using single strand conformation polymorphism (SSCP) and direct sequencing of SSCP-positive region. The proband was homozygous for a C > A transversion in exon 6, which converts the codon for tyrosine at position 302 into a termination codon and eliminates an RsaI restriction site; this allowed the rapid screening of the proband's family members, among whom nine heterozygotes and one additional homozygote were identified. The homozygote was the proband's paternal grandmother who had shown the first clinical manifestation (recurrent pancreatitis) of LPL deficiency at the age of 54 years. LPL mutation carriers showed a mild dyslipidemic phenotype characterized by a reduction of high density lipoprotein-cholesterol (HDL-C) levels, HDL-C/total cholesterol ratio, and low density lipoprotein (LDL) size, associated with a variable increase of triglyceride levels. Five of these carriers were also heterozygotes for beta-thalassemia (Q39X mutation). In these double mutation carriers, plasma HDL-C levels were higher and plasma triglycerides tended to be lower than in carriers of LPL mutation alone. The Tyr302 > Term mutation encodes a truncated protein of 301 amino acids that is probably not secreted by the LPL producing cells. This is the first mutation of LPL gene found in Sardinians.     

Stimulating effect of intermediate-density lipoproteins (IDL) from hyperlipemic plasma on hepatic lipase

Summary The main lipoprotein density classes, namely very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), high-density lipoproteins₂ (HDL₂) and HDL₃ were investigated with respect to their influence on hepatic lipase (HTGL) activity in vitro.Lipoproteins from pooled normal plasma (NP) and from pooled hyperlipemic plasma (HP) were prepared by means of sequential ultracentrifugation. Hepatic lipase was determined radioenzymatically after preincubation with protamine sulfate. It could be demonstrated that IDL from HP were able to stimulate HTGL activity by approximately 100% above the baseline value. HDL₃ from both NP and HP revealed an inhibiting effect on HTGL activity. VLDL, LDL, and HDL₂ exhibited no significant effect on HTGL activity.It is speculated that HTGL could possibly represent a second pathophysiological pathway for the catabolism of IDL in hyperlipemia but this presumption is supported by only a few investigations in vivo.

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Abbreviations HDL₂ High-density lipoproteins₂ - HDL₃ High-density lipoproteins₃ - HP Hyperlipemic plasma pool - HTGL Hepatic lipase - IDL Intermediate-density lipoproteins - LDL Low-density lipoproteins - NP Normal plasma pool - VLDL Very low-density lipoproteins     

脂蛋白酶酶基因多态性对单纯肥胖症儿童血脂、体重指数及皮下脂肪分布的影响

目的　探讨脂蛋白酯酶 (lipoprotein lipase,L PL)基因中常见多态位点 Hind 基因多态性对单纯肥胖症儿童血脂、体重指数 (body m ass index,BMI)及皮下脂肪分布的影响。方法　应用聚合酶链反应和限制性内切酶片段长度多态性技术 ,检测了 92例单纯肥胖症儿童的 Hind - L PL基因多态性 ,并测定了血脂、BMI及机体 3个测量部位 (肱二头肌、肩胛下、腹壁 )的皮褶厚度等。结果　 H H - L PL基因型肥胖儿童的血甘油三酯 (TG)、L DL- C、Apo B含量及 BMI、肱二头肌皮褶厚度、肩胛下皮褶厚度、皮褶均数等 ,均明显高于 H H- - L PL 基因型肥胖儿童。结论　L PL- Hind 基因多态性对单纯肥胖症儿童的血脂与BMI水平 ,总胆固醇 (TC)以及皮下脂肪在机体各部位的分布具有重要影响。     

Effects of a brisk walk on lipoprotein lipase activity and plasma triglyceride concentrations in the fasted and postprandial states

This study aimed to determine whether changes in plasma heparin-releasable lipoprotein lipase (LPL) activity following a brisk walk were associated with decreases in fasting and/or postprandial triglyceride (TG) concentrations. Two groups of pre-menopausal women participated. In one group (fasting study group, n=10), TG concentrations and post-heparin plasma LPL activity were measured in the fasted state on two occasions: ~18 h after a 2-h treadmill walk at 50% maximal oxygen uptake (exercise trial); and after a day of no exercise (control trial). The other group (postprandial study group, n=9) undertook two oral fat tolerance tests (blood samples taken fasting and for 6 h after a high-fat meal), with plasma LPL activity measured 6 h after meal ingestion. Pre-conditions were the same as for the fasting study group (i.e. control and prior exercise). Prior exercise reduced fasting TG concentrations by 23 (7)% (fasting study group) [mean (SEM)] and by 18 (9)% (postprandial study group) (both P<0.05), and the postprandial TG response by 23 (6)% (postprandial study group) (P<0.01). Plasma LPL activity was not significantly increased by exercise in either the fasting or postprandial study groups. However, exercise-induced changes in both fasting and postprandial LPL activity were significantly correlated with the respective exercise-induced changes in fasting TG concentration and the postprandial TG response (r=−0.70 and −0.77 respectively, P<0.05 for both). These data suggest that increased LPL activity may contribute to the hypotriglyceridaemic effect of moderate exercise, although other mechanisms are also likely to be involved. Electronic Publication     

Prevalence, geographical distribution and genealogical investigations of mutation 188 of lipoprotein lipase gene in the French Canadian population of Québec

Familial lipoprotein lipase deficiency (FLD) is of particular interest to the French Canadian population of Québec since the largest concentration of homozygotes and carriers of this genetic disease in the world resides in this area. We have previously described a missense mutation (M-188) in the lipoprotein lipase (LPL) gene which was present in FLD patients belonging to different ancestries, including a number of French Canadians (Monsalve MV et al. J Clin Invest 1990: 86: 728-734). In the present report, we show that this mutation, although found in largest absolute numbers among French Canadians as compared to other groups in the world, accounts for only a small proportion (24%) of all the LPL mutant alleles in this population. The M-188 occurs either in the homozygote state or as a compound heterozygote with another LPL mutation. Analysis of geographic distribution indicates that the M-188 is more prevalent in western Québec, with the highest carrier rate in the Mauricie region. Genealogical reconstruction leads to the recognition of four founders for M-188, all emigrants from France to Québec in the 17th century.     

The effect of vigorous physical activity at work on serum lipids with a special reference to serum high-density lipoprotein cholesterol

Serum lipid concentrations of lumberjacks whose occupational physical activity is most vigorous were compared with those of electricians. The lumberjacks had significantly higher serum HDL-cholesterol and significantly lower triglyceride and free fatty acid concentrations hut there were no significant differences in total cholesterol levels. The favourable effect of vigorous physical activity at work on lipid metabolism is, however, epidemiologically not seen, obviously due to negative risk factors in lumberjacks' life.     

Lipoprotein lipase and hepatic triglyceride lipase reduce the infectivity of hepatitis C virus (HCV) through their catalytic activities on HCV-associated lipoproteins

The effect of lipolysis by lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) on hepatitis C virus (HCV) infection was evaluated. First, medium from HuH7.5 cells bearing HCV genome replication was treated with LPL. LPL treatment led to reduced HCV infectivity, shifted HCV to higher densities, and lowered the amount of apolipoprotein E-associated HCV. The effect of endogenous HTGL secreted from HuH7.5 on HCV infectivity was next examined. Neutralization of HTGL by an anti-HTGL antibody resulted in suppression of LPL-induced reduction in infectivity of HCV-bearing medium, while knockdown of HTGL by siRNA led to increased HCV infectivity irrespective of LPL. HCV in medium from HTGL knockdown cells was found in fractions with a lower density. These results indicate that changes in the nature of HCV-associated lipoproteins by LPL and/or HTGL affect HCV infectivity, suggesting that association of HCV with specific lipoproteins is important for HCV infectivity.     

Changes in the ratio between apolipoprotein (a) and lipids in human plasma during interaction with polyclonal sheep antibodies against lipoprotein (a)

Plasma contents of apolipoprotein (a), apolipoprotein B 100, cholesterol, triglycerides, and vitamin E were measured in 2 patients with lipoprotein (a) concentration >100 mg/dl during the interaction with the anti-lipoprotein (a) immunosorbent. Intraindividual heterogeneity of apolipoprotein (a)-containing particles in the plasma was demonstrated. Polyclonal antibodies against lipoprotein (a) immobilized on Sepharose CL-4B more effectively removed free apolipoprotein (a) than complexes containing apolipoproteins B 100, apolipoprotein (a), lipids, and vitamin E.     

Maximal low density lipoprotein receptor activity and the effect of lipid lowering diet on total serum cholesterol

This study was undertaken to test if the effect of lipid lowering diet on total serum cholesterol, is influenced by maximal low density lipoprotein (LDL) receptor activity. LDL receptor activity was determined in cultured skin fibroblasts from hypercholesterolemic, male subjects after lipid lowering diet intervention. The LDL receptor values from 15 subjects (responders) who had responded well to a lipid lowering diet and from 14 subjects (non-responders) who had responded poorly, were compared. The responders had a reduction in total serum cholesterol of 29.4%, and the non-responders had a reduction of 8.2% (p less than 0.0001). The higher values for LDL receptor activity among the responders did not reach statistical significance. For all 29 subjects there were non-significant positive correlations between reductions in total serum cholesterol and values for association or degradation of 125I-LDL at 37 degrees C (r = 0.16, p = 0.40 and r = 0.17, p = 0.38, respectively). Thus, it seems that maximal LDL receptor activity is not a major predictor for the response of lipid lowering diet on total serum cholesterol levels in hypercholesterolemic subjects without autosomal dominant familial hypercholesterolemia.     

The effect of percutaneous oestrogen replacement therapy on Lp(a) and other lipoproteins

Objectives: To determine the effect of percutaneous oestrogen replacement therapy on lipoprotein (a) and other plasma lipoproteins. Methods: Open longitudinal prospective study conducted at the hormone replacement clinic of the Prince of Wales Hospital, New Territories, Hong Kong. Thirty women who had undergone a total abdominal hysterectomy and bilateral salpingo-oophorectomy for benign gynaecological conditions were treated with 1.5 mg of percutaneous 17β-oestradiol gel applied daily for a period of 12 consecutive months. Measurements of plasma lipoproteins were made before the commencement of treatment and repeated at 6- and 12-month intervals. Results: There was a significant reduction in the concentrations of Lp(a) during the first 6 months of treatment, with median values falling from 7.87 mg dL⁻¹ to 6.16 mg dL⁻¹ (P = 0.004, 0–6 months). During the second 6 months, the median concentration increased to 9.38 mg dL⁻¹, (P = 0.072, 66-12 months), which did not significantly differ from the baseline level (P = 0.545, 0–12 months). Significant reductions in the concentrations of apoprotein A-I (apo A-I), apoprotein B (apo B), high density lipoprotein cholesterol (HDL-C), and HDL₃-C were also present after 6 months (P = 0.043, 0.049, 0.028, 0.013, respectively), but there were no differences between the baseline values of these lipoproteins and those at the completion of the study (P = 0.948, 0.244, 0.839, 0.117 respectively). Drug compliance was maintained throughout the study, with similar mean oestradiol concentrations at 6 and 12 months. Conclusions: The percutaneous administration of 17β-oestradiol has variable short term effects on plasma lipoproteins which are not maintained over a longer duration of treatment. By avoiding the ‘first pass’ effect on the liver, this method of delivery does not appear to produce the sustained changes in lipoproteins seen with oral treatment.     

In vitro studies of the interaction of calcium ions and other divalent cations with the Lp(a) lipoprotein and other isolated serum lipoproteins

The interaction of isolated Lp(a) lipoprotein with different divalent cations was studied and compared to that of other isolated lipoprotein classes.
Purified Lp(a) lipoprotein was found to be most sensitive to the metal ions tested, and the Lp(a) lipoprotein was the only lipoprotein which was precipitated by calcium ions alone. The precipitation apparently depends on the ionic radii of the cations used as well as on the lipoprotein class tested. The precipitation reaction between calcium ions and the Lp(a) lipoprotein, and the interaction between calcium ions and LDL (without precipitation) seem to follow the known rules for small ion - macromolecule interaction reasonably well. The calcium ion - Lp(a) lipoprotein interaction results in a small aggregate. The binding is of ionic type and the precipitation reaction is initially reversible. It was estimated that LDL particles have a mean of 290 equivalent and non-interacting binding sites for calcium ions.
The above observations concerning the Lp(a) lipoprotein may be of interest in view of the significantly higher frequency of early coronary heart disease in Lp(a+) than in Lp(a-) individuals, and in view of the previously reported biochemical differences between individuals of different Lp phenotype.     

一例儿童轻型人感染H7N9禽流感确诊病例调查

目的 分析2013年北京市海淀区一例人感染H7N9禽流感病例的发病、诊治和感染来源情况,提出疫情控制措施调整意见.方法 采集患儿标本进行实验室检测,应用《人感染H7 N9禽流感个案调查表》与患儿及其家属面对面问卷调查,获得现场资料.结果 患儿以上呼吸道症状为首发症状,经门诊治疗痊愈,传染源不明.患儿无肺部感染,经过抗炎、抗病毒治疗,未服用达菲.结论 人感染H7 N9禽流感是一种新出现的传染病,传染和流行特征未明,要加强流感样病例监测、流感病原学监测、不明原因肺炎监测等传染病监测工作,及时发现病例,及早采取防治措施.     

In vitro studies of the interaction of isolated Lp(a) lipoprotein and other serum lipoproteins with glycosaminoglycans

The interaction of isolated Lp(a) lipoprotein or other lipoprotein classes with different glycosaminoglycans (GAG) bound to activated Sepharose was studied. In contrast to LDL, the Lp(a) lipoprotein did not bind to the GAG tested if sodium was used as a buffer cation. In the presence of Ca++, however, even the Lp(a) lipoprotein was bound to GAG. This type of binding, probably mediated by divalent cation bridges, is apparently not a simple function of the GAG used. Addition of GAG in solution revealed that this binding may be the only one existing under physiological conditions, and it appears possible that the Lp(a) lipoprotein is bound more firmly to GAG than is LDL under such conditions.