Patients with apoE3 deficiency (E2/2, E3/2, and E4/2) who manifest with hyperlipidemia have increased frequency of an Asn 291-->Ser mutation in the human LPL gene

Exercise Delays Brain Ageing Through Muscle-Brain Crosstalk

Ageing is often accompanied by cognitive decline and an increased risk of dementia. Exercise is a powerful tool for slowing brain ageing and enhancing cognitive function, as well as alleviating depression, improving sleep, and promoting overall well-being. The connection between exercise and healthy brain ageing is particularly intriguing, with exercise-induced pathways playing key roles. This review explores the link between exercise and brain health, focusing on how skeletal muscle influences the brain through muscle-brain crosstalk. We examine the interaction between the brain with well-known myokines, including brain-derived neurotrophic factor, macrophage colony-stimulating factor, vascular endothelial growth factor and cathepsin B. Neuroinflammation accumulates in the ageing brain and leads to cognitive decline, impaired motor skills and increased susceptibility to neurodegenerative diseases. Finally, we examine the evidence on the effects of exercise on neuronal myelination in the central nervous system, a crucial factor in maintaining brain health throughout the lifespan.

Presence of the apolipoprotein E-ε4 allele is associated with an increased risk of sepsis progression

Growing evidence indicated that single nucleotide polymorphisms (SNPs) in the apolipoprotein E (APOE) gene are related to increase the risk of many inflammatory-related diseases. However, few genetic studies have associated the APOE gene polymorphism with sepsis. This study was to investigate the clinical relevance of the APOE gene polymorphism in the onset and progression of sepsis. A multicenter case–control association study with a large sample size (601 septic patients and 699 healthy individuals) was conducted. Clinical data showed that the APOEε4 allele was overrepresented among all patients with septic shock (p = 0.031) compared with sepsis subtype, suggesting that APOEε4 allele may associated with increased susceptibility to the progression of sepsis. Moreover, the APOE mRNA levels decreased after lipopolysaccharide (LPS) stimulation in cells in culture. Then 21 healthy individuals to extract PBMC for genotype grouping (APOE4+ group 8; APOE4− group 13) was selected to evaluate the effect on APOE level, and results showed that the expression level of APOE in APOE4+ group and APOE4− group did not differ in mRNA levels after an LPS challenge, but the protein levels in APOE4+ group decreased slower than that in APOE4− group, and this process was accompanied by the upregulation of proinflammatory cytokines. These results provide evidence that the APOEε4 allele might be associated with the development of sepsis and a potential risk factor that can be used in the prognosis of sepsis.

Metabolic syndrome and its components in postmenopausal women living in southern Italy, Apulia region

OBJECTIVES

The goal of our study was to determine the prevalence of metabolic syndrome (MetS) and all its components, in a population of postmenopausal women aged over 45 years, consecutively accessed to our Heart Station, during 2014, for their first cardiac examination,furthermore to estimate their cardiovascular risk and the achievement of target blood values of main risk factors, according to current Guidelines.

METHODS

We screened 1257 postmenopausal women. MetS was assessed according to the National-Cholesterol-Education-Program-Adult-Treatment-Panel III definition. Cardiovascular risk was calculated by the Systematic Coronary Risk Evaluation (<65 years).

RESULTS

MetS was assessed on 834 women (66.4%). Prevalence of each component was: hypertension on 767 women (91.9%), central obesity 758 women (90.9%), low high-density lipoproteins cholesterol (HDLc) increased levels 612 women (73.3%), high triglyceride levels 428 women (51.3%), glucose levels higher than 110mg/dl or diabetes 404 women (48.5%). Cardiovascular risk was moderate until 65 years, but it increases after. Metabolic control in postmenopausal women was poor for glucose, only 82 women (9.8%) presented glucose levels lower than 110mg/dl, it was better for systolic blood pressure, that was normal in 564 women (67.6%) and worse for lipid levels.

CONCLUSION

The prevalence of metabolic syndrome in our population of postmenopausal women is high. Hypertension and central obesity are the more common components. The cardiovascular risk is moderate-high, the achievement of target values for glycemic and lipid levels is unsatisfactory, while systolic blood pressure is enough well controlled but however it is mandatory to improve this goal. An early MetS diagnosis and an early educational intervention are useful to decrease cardiovascular risk of postmenopausal women affected by metabolic syndrome.

The prevalence of metabolic syndrome and its predominant components among pre-and postmenopausal Ghanaian women

BACKGROUND

Metabolic Syndrome (MetS) is a clump of risk factors for development of type 2 diabetes mellitus and cardiovascular diseases. Menopause and age are thought to predispose women to the development of metabolic syndrome. This study aimed to estimate the prevalence of MetS and identify its predominant components among pre-and postmenopausal women in the Kumasi Metropolis, Ghana.Two hundred and fifty (250) Ghanaian women were randomly selected for the study. They were evaluated for the prevalence of metabolic syndrome using the World Health Organization (WHO), National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III), International Diabetes Federation (IDF) and Harmonization (H_MS) criteria.

RESULTS

Out of the total subjects, 143 (57.2%) were premenopausal and 107 (42.8%) menopausal. The study population was between the ages of 20-78 years. The overall percentage prevalence of MetS were 14.4%, 25.6%, 29.2% and 30.4% according to the WHO, NCEP-ATP III, IDF and H_MS criteria, respectively. The prevalence was found to increase with age, irrespective of criterion used. Generally, MetS was significantly higher among postmenopausal women (p < 0.05 by all criteria) compared to their premenopausal cohort, but with marked inter-criteria variations. Abdominal obesity, blood pressure, fasting blood glucose, triglyceride, very low density lipoprotein cholesterol, and triglyceride-high density lipoprotein cholesterol ratio were significantly (p < 0.05) different among the two groups of women.Central obesity, higher blood pressure and raised fasting blood glucose were the predominant components that contributed to the syndrome in Ghanaian women.

CONCLUSION

The higher prevalence of the metabolic syndrome in postmenopausal women is an indication that they are at risk of developing cardiovascular disease and type 2 diabetes. Therefore women in that group should be monitored for the two conditions and also be advised to adopt healthy lifestyles to minimize the incidence of these conditions.

Genetic variants at the APOE, lipoprotein lipase (LpL), cholesteryl ester transfer protein (CETP), and endothelial nitric oxide (eNOS) genes and coronary artery disease (CAD): CETP Taq1 B2B2 associates with lower risk of CAD in Asian Indians

Coronary artery disease (CAD) arises due to a complex interplay between the environment and genetic factors. Alterations in many of the biomarkers such as lipids and lipoprotein levels are characteristic of CAD. The phenotypes themselves have genetic determinants, and many single-nucleotide polymorphisms (SNPs) have been identified which influence them. The current study aims to evaluate the effect of six common polymorphisms at four loci, lipoprotein lipase (D9N, N291S, S447X), apolipoprotein E (APOE), cholesteryl ester transfer protein (C277T), and endothelial nitric oxide synthase (E298D), on lipid and lipoprotein levels and its association with CAD. Genotyping for the SNPs was done in 240 Indians of which 90 had proven CAD. The other 150 were clinically free from CAD and acted as controls. Relation of genetic variants, clinical history, and biochemical parameters with CAD were analyzed by multiple regression analysis. The frequency of the B2 allele in the CETP gene was significantly lower in cases than in controls (0.40 vs 0.49, P = 0.042). Significant association of CETP Taq1B SNP was seen with total cholesterol and low density lipoprotein cholesterol. Multivariate analysis accounting for clinical and metabolic predictors of CAD showed smoking to be a significant risk factor (odds ratio (OR) 4.347, 95% confidence interval (CI) 1.888-10.012, P = 0.001) and the CETP B2 variant imparting atheroprotection (OR 0.312, 95% CI 0.116-0.841, P = 0.021) possibly through a favorable lipid profile. None of the other SNPs were associated with the risk of CAD.

The expression of type III hyperlipoproteinemia: involvement of lipolysis genes

Type III hyperlipoproteinemia (HLP) is mainly found in homozygous apolipoprotein (APO) E2 (R158C) carriers. Genetic factors contributing to the expression of type III HLP were investigated in 113 hyper- and 52 normolipidemic E2/2 subjects, by testing for polymorphisms in APOC3, APOA5, HL (hepatic lipase) and LPL (lipoprotein lipase) genes. In addition, 188 normolipidemic Dutch control panels (NDCP) and 141 hypertriglyceridemic (HTG) patients were genotyped as well. No associations were found for four HL gene polymorphisms and two LPL gene polymorphisms and type III HLP. The frequency of the rare allele of APOC3 3238 G>C and APOA5 -1131 T>C (in linkage disequilibrium) was significantly higher in type III HLP patients when compared with normolipidemic E2/2 subjects, 15.6 vs 6.9% and 15.1 vs 5.8%, respectively, (P<0.05). Furthermore, the frequencies of the APOA5 c.56 G>C polymorphism and LPL c.27 G>A mutation were higher in type III HLP patients, though not significant. Some 58% of the type III HLP patients carried either the APOA5 -1131 T>C, c.56 G>C and/or LPL c.27 G>A mutation as compared to 27% of the normolipidemic APOE2/2 subjects (odds ratio 3.7, 95% confidence interval=1.8-7.5, P<0.0001). The HTG patients showed similar allele frequencies of the APOA5, APOC3 and LPL polymorphisms, whereas the NDCP showed similar allele frequencies as the normolipidemic APOE2/2. Patients with the APOC3 3238 G>C/APOA5 -1131 T>C polymorphism showed a more severe hyperlipidemia than patients without this polymorphism. Polymorphisms in lipolysis genes associate with the expression and severity of type III HLP in APOE2/2.

APOA5 genetic variants are markers for classic hyperlipoproteinemia phenotypes and hypertriglyceridemia

BACKGROUND

Several known candidate gene variants are useful markers for diagnosing hyperlipoproteinemia. In an attempt to identify other useful variants, we evaluated the association of two common APOA5 single-nucleotide polymorphisms across the range of classic hyperlipoproteinemia phenotypes.

METHODS

We assessed plasma lipoprotein profiles and APOA5 S19W and -1131T>C genotypes in 678 adults from a single tertiary referral lipid clinic and in 373 normolipidemic controls matched for age and sex, all of European ancestry.

RESULTS

We observed significant stepwise relationships between APOA5 minor allele carrier frequencies and plasma triglyceride quartiles. The odds ratios for hyperlipoproteinemia types 2B, 3, 4 and 5 in APOA5 S19W carriers were 3.11 (95% CI 1.63-5.95), 4.76 (2.25-10.1), 2.89 (1.17-7.18) and 6.16 (3.66-10.3), respectively. For APOA5 -1131T>C carriers, the odds ratios for these hyperlipoproteinemia subtypes were 2.23 (95% CI 1.21-4.08), 3.18 (1.55-6.52), 3.95 (1.85-8.45) and 4.24 (2.64-6.81), respectively. The overall odds ratio for the presence of either allele in lipid clinic patients was 2.58 (95% CI 1.89-3.52).

CONCLUSIONS

A high proportion of patients with four classic hyperlipoproteinemia phenotypes are carriers of either the APOA5 S19W or -1131T>C variant or both. These two variants are robust genetic biomarkers of a range of clinical hyperlipoproteinemia phenotypes linked by hypertriglyceridemia.

The D9N, N291S and S447X variants in the lipoprotein lipase (LPL) gene are not associated with Type III hyperlipidemia

BACKGROUND

Type III hyperlipidemia (Type III HLP) is associated with homozygosity for the epsilon2 allele of the APOE gene. However only about 10% of epsilon2 homozygotes develop Type III HLP and it is assumed that additional genetic and/or environmental factors are required for its development. Common variants in the LPL gene have been proposed as likely genetic co-factors.

METHODS

The frequency of the LPL SNPs D9N, N291S and S447X in 100 patients with hyperlipidemia and APOE2/2 genotype has been determined and compared to that in healthy blood donors and patients with hyperlipidemia.

RESULTS

There were no statistically significant difference in the frequencies of the variants between APOE2/2 patients and controls.

CONCLUSION

It is unlikely that the D9N, N291S or S447X variants in the LPL gene play an important role in the development of Type III HLP.

The lipoprotein lipase gene serine 447 stop variant influences hypertension-induced left ventricular hypertrophy and risk of coronary heart disease

LVH [LV (left ventricular) hypertrophy] is an independent risk factor for CHD (coronary heart disease). During LVH, the preferred cardiac energy substrate switches from FAs (fatty acids) to glucose. LPL (lipoprotein lipase) is the key enzyme in triacylglycerol (triglyceride) hydrolysis and supplies FAs to the heart. To investigate whether substrate utilization influences cardiac growth and CHD risk, we examined the association between the functional LPL S447X (rs328) variant and hypertension-induced LV growth and CHD risk. LPL-X447 has been shown to be more hydrolytically efficient and would therefore release more free FAs than LPL-S477. In a cohort of 190 hypertensive subjects, LPL X447 was associated with a greater LV mass index [85.2 (1.7) in S/S compared with 91.1 (3.4) in S/X+X/X; P=0.01], but no such association was seen in normotensive controls (n=60). X447 allele frequency was higher in hypertensives with than those without LVH {0.14 [95% CI (confidence interval), 0.08-0.19] compared with 0.07 (95% CI, 0.05-0.10) respectively; odds ratio, 2.52 (95% CI, 1.17-5.40), P=0.02}. The association of LPL S447X with CHD risk was then examined in a prospective study of healthy middle-aged U.K. men (n=2716). In normotensive individuals, compared with S447 homozygotes, X447 carriers were protected from CHD risk [HR (hazard ratio), 0.48 (95% CI, 0.23-1.00); P=0.05], whereas, in the hypertensives, X447 carriers had increased risk [HR, 1.54 (95% CI, 1.13-2.09) for S/S (P=0.006) and 2.30 (95% CI, 1.53-3.45) for X447+ (P<0.0001)] and had a significant interaction with hypertension in CHD risk determination (P=0.007). In conclusion, hypertensive LPL X447 carriers have increased risk of LVH and CHD, suggesting that altered FA delivery constitutes a mechanism through which LVH and CHD are associated in hypertensive subjects.

A systematic review and meta-analysis of the relationship between lipoprotein lipase Asn291Ser variant and diseases

This systematic review attempted to summarize the associations between the Asn291Ser variant in the lipoprotein lipase (LPL) gene and dyslipidemia, the risk of type 2 diabetes mellitus (T2DM), and coronary heart disease (CHD). In addition, the relationships between the Asn291Ser variant and other metabolic diseases such as obesity and high blood pressure were also investigated in this systematic review. We systematically reviewed the literature by means of a meta-analysis. Twenty-one articles, including 19,246 white subjects, were selected for this meta-analysis. The summary standardized mean difference (SMD) of plasma triglyceride (TG) for carriers compared with noncarriers of the Asn291Ser variant was 3.23 (P < 0.00001). The summary SMD of plasma HDL-cholsterol (HDL-C) for carriers compared with noncarriers of the Asn291Ser variant was -3.42 (P < 0.0001). The summary SMD of the association of the Asn291Ser variant with plasma TG increased with increasing age and weight gain. Significant interactions between the LPL Asn291Ser variant and fasting glucose, T2DM, and CHD were seen (P = 0.02, 0.04, and 0.01, respectively). No significant interactions were seen between the LPL Asn291Ser variant and body mass index, waist-hip ratio, and blood pressure (P > 0.05). This meta-analysis indicates that the Asn291Ser variant in the LPL gene is a risk factor for dyslipidemia, characterized by hypertriglyceridemia and low HDL-C levels. And the Asn291Ser variant in the LPL gene predisposes to more severe dyslipidemia with increasing age and weight gain. Also, this meta-analysis shows that the LPL Asn291Ser variant is associated with CHD and T2DM.

Polymorphisms in the apolipoprotein A5 (APOA5) gene and type III hyperlipidemia

The great majority of patients with type III hyperlipidemia (type III HLP) are homozygous for the epsilon2 allele of the APOE gene. However, only about 10% of epsilon2 homozygotes develop type III HLP, and it has been proposed that additional genetic factors are required for the development of the condition. The frequency of two polymorphisms in the APOA5 gene, -1131T>C and S19W, has been determined in 72 hyperlipidemic patients with APOE2/2 genotype attending a lipid clinic. The frequency of both polymorphisms was significantly higher in APOE2/2 patients than in the normal population. Fifty-three percent of APOE2/2 patients were carriers of one of the polymorphisms compared to 19.7% of controls. Thus, genetic variation in the APOA5 gene is an important cofactor in the development of type III HLP.

Requirement for enzymatically active lipoprotein lipase in neuronal differentiation: a site-directed mutagenesis study

Lipoprotein lipase (LPL) is well known for its role in the catabolism of plasma triglyceride (Tg)-rich lipoproteins, such as very low density lipoproteins (VLDL) and chylomicrons. The action of LPL on Tg-rich lipoproteins provides free fatty acids to skeletal muscle and adipose tissues, the main sites of LPL synthesis. Several studies have demonstrated that LPL is widely expressed in the parenchyma of brain tissues. We have recently shown that LPL expression is essential for promoting VLDL-stimulated differentiation of Neuro-2A cells. In the present study, we have generated stably transfected Neuro-2A cell lines expressing either wild-type LPL or various LPL mutants, including three enzymatically inactive variants (Asp156Asn, Gly188Glu and Pro207Leu), an enzymatically defective variant (Asn291Ser) and a variant known to express increased LPL activity (Ser447Ter). In Neuro-2A cells expressing enzymatically inactive LPL variants, VLDL-stimulated differentiation and neurite extension were not observed. However, in Neuro-2A cells expressing partially active or overactive LPL variants, VLDL added to the cultured medium was able to induce the phenotypic differentiation similar to that observed in Neuro-2A cells expressing wild-type LPL. In summary, these data show that the availability of fatty acids, resulting from the catabolism of VLDL by LPL, is required to promote the phenotypical differentiation of neuroblastoma cells. These findings may have significant relevance to lipoprotein metabolism in the brain as well as to the maturation and regeneration of nervous tissues in carriers of mutant LPL.

The association of the R219K polymorphism in the ATP-binding cassette transporter 1 ( ABCA1) gene with coronary heart disease and hyperlipidaemia

The R219K polymorphism in the ATP-binding cassette transporter 1 gene ( ABCA1) has been associated with reduced severity of atherosclerosis, fewer coronary events, decreased triglycerides and a trend to increased HDL in men with coronary heart disease (CHD). This study examined the frequency and the effect on CHD and plasma lipids of the polymorphism in patients of both sexes attending a lipid out-patient clinic. The overall frequency of the K allele was 0.26. It was lower in patients with CHD (0.21) than in those without (0.27) but this was not statistically significant. Amongst patients with elevated Lp(a) the frequency of the K allele was significantly lower in those with CHD (0.16) than in those without (0.29). There were no statistically significant differences in total cholesterol, LDL, HDL, apoB or apoAI between carriers and non-carriers. When patients with probable secondary hypertriglyceridaemia (triglycerides >1000 mg/dl), type 2 diabetes and carriers of lipoprotein lipase polymorphisms associated with hypertriglyceridaemia were excluded, the K allele was significantly associated with reduced triglycerides but only in patients with apoE 3/3 genotype. In conclusion, we provide additional evidence that the R219K polymorphism in the ABCA1 gene either directly or as a result of linkage disequilibrium with additional functional variant(s), has a protective effect against CHD and is associated with lower plasma triglycerides in sub-groups of patients with hyperlipidaemia.

Common Variants in the Lipoprotein Lipase Gene in Brazil: Association with Lipids and Angiographically Assessed Coronary Atherosclerosis

Lipoprotein lipase is the rate-limiting enzyme in the lipolysis of plasma triglyceride-rich lipoproteins. We studied six variants (T-93G, D9N, N291S, PvuII, HindIII and S447X) in the lipoprotein lipase (LPL) gene in 309 non-diabetic patients with angiographically assessed coronary artery disease and in 197 controls in a southern Brazilian population of European descent. The HindIII H-allele was associated with lower triglycerides (p < 0.01) and higher high-density lipoprotein cholesterol (p = 0.03) levels, and the S447X mutation was associated with lower triglyceride levels (p < 0.01) in males, but not females. No other significant lipid associations were observed. Haplotypes were derived from these two sites (HindIII/S447X), and carriers of H-S and H-X haplotypes showed lower triglycerides (p < 0.01) and increased high-density lipoprotein cholesterol (p = 0.01) levels when compared to the H+S haplotype in males. In this gender, the H-X haplotype was associated with a protective effect (OR = 0.36, 95%CI = 0.13-0.97) for significant disease (> or = 60% of luminal coronary stenosis), even controlling for other classical risk factors.

Structure-function analysis of D9N and N291S mutations in human lipoprotein lipase using molecular modelling

Lipoprotein lipase (LPL) plays a central role in lipid metabolism. The D9N and N291S mutations in the LPL gene are associated with elevated triglyceride and decreased HDL-cholesterol levels. Published in vitro expression studies suggest that these two mutations are associated with reduced LPL enzymatic activity. We sought to gain further insight on the impact of these two mutations on the LPL structure and function by molecular modelling techniques. Homology modelling was used to develop a three-dimensional (3D) structure of LPL from human pancreatic lipase. Two separate LPL models for the D9N and N291S substitutions were constructed and compared with the wild type LPL for differences in hydrophobicity, atomic burial, hydrogen bond pattern, and atomic mobility. In comparison to the wild type model, the 9N model was associated with significantly increased atomic mobility of its neighboring residues, but the catalytic site was not affected. The region near residue 9 in the upper part of the N-domain was considered a candidate site for protein-protein interaction. In the N291S model, alterations in H-bonds and constrained atomic mobility were among conformational changes in the region where the substitution had occurred. These are hypothesized to cause an increase in the rate of dissociation in LPL dimerization, subsequently affecting the LPL enzymatic activity. We also modelled the C-domain of apoCII, the obligatory cofactor of LPL, from 2D NMR data and docked the model with LPL to explore their interaction site. These docking experiments suggest that the C-domain of apoCII interacts with the interface of N- and C-domains of LPL and part of the lid structure that covers the catalytic site. In summary, we provide molecular modelling data on two well-known mutations in the LPL gene to help explain the published in vitro expression findings and propose a possible LPL-apoCII interaction site. Our data indicate that molecular modelling of LPL mutations could provide a valuable tool to understand the effects of a mutation on the structure-function of this important enzyme.

Parental history of myocardial infarction: lipid traits, gene polymorphisms and lifestyle

To investigate the relationship between parental history of myocardial infarction (MI), lipid traits and gene polymorphisms involved in lipid metabolism, we examined Dutch men and women, who were selected from a large population-based study. Subjects whose father (n=112), mother (n=115) or both parents (n=115) suffered from a premature MI presented with significantly higher apolipoprotein B (apo B) levels than subjects without a parental history (n=114). Genetic analyses revealed that the apo E4 isoform and the D9N mutation of lipoprotein lipase (LPL) were more frequent among subjects with a parental history (P< or =0.05). A similar trend was found for the LPL N291S mutation. In contrast, the LPL S447X mutation and polymorphisms at the cholesteryl ester transfer protein (TaqIB) and apo CIII (SstI) loci proved to be noninformative. Body mass index and lifestyle could not explain differences in apo B levels between parental history groups. In contrast, the apo E polymorphism and the LPL D9N mutation accounted for some, but not all, of the higher apo B levels in subjects with a parental history. Therefore, other genetic or lifestyle-related factors must be responsible for the increased levels of apo B in individuals with a family history of myocardial infarction.

Roles for lipoprotein lipase in Alzheimer's disease: an association study

Lipoprotein lipase (LPL) assists lipid transport by transferring lipids between lipoprotein particles and cells. LPL binds apolipoprotein E (apoE) lipoprotein particles and a major apoE receptor, low density lipoprotein receptor related protein (LRP). Because apoE and LRP polymorphisms alter Alzheimer's disease (AD) risk, and LPL itself is found in AD amyloid plaques, we examined whether LPL variants also affect AD risk. In case-control studies in the United States and Canada, the frequencies of two LPL alleles known to affect LPL enzymatic activity were measured in Caucasian AD or elderly normal (N) subjects. Pathologically confirmed subjects in both studies exhibited similar trends toward fewer 447Ter and more 291Ser alleles in AD. Combining results from both countries gave allele frequencies for 447Ter of 13.7% (26/190) in N and 9.4% (80/852) in AD (P = 0.10), and for 291Ser of 0.0% (0/184) in N and 1. 3% (8/636) in AD (P = 0.21). The trend appeared even greater for homozygous 447Ter subjects: 4.2% (4/95) of N vs. 1.4% (6/426) of AD (P = 0.09). These trends are consistent with a putative protective effect of 447Ter and causative effect of 291Ser on AD. Furthermore, brains of AD patients with 447Ter showed trends toward fewer plaques, tangles, and glia, and more neurons and cortical thickness than AD patients without 447Ter. Hippocampal plaques were significantly reduced. LPL might affect hippocampal function and thus dementia via its role as supplier of membrane components or antioxidants to neurons. Alternatively, LPL may play a part in plaque formation through its interaction with apoE and LRP.

A single Ser259Arg mutation in the gene for lipoprotein lipase causes chylomicronemia in Moroccans of Berber ancestry

Lipoprotein lipase (LPL) is the rate-limiting enzyme for the hydrolysis of triglyceride-rich lipoproteins. Numerous LPL gene mutations have been described as a cause of familial chylomicronemia in various populations. In general, allelic heterogeneity is observed in LPL deficiency in different populations. However, a founder effect has been reported in certain populations, such as French Canadians. Although familial chylomicronemia is observed in Morocco, the molecular basis for the disease remains unknown. Here, we report two unrelated Moroccan families of Berber ancestry, ascertained independently in Holland and France. In both probands, familial chylomicronemia manifested in infancy and was complicated with acute pancreatitis at age 2 years. Both probands were homozygous for a Ser259Arg mutation, which results in the absence of LPL catalytic activity both in vivo and in vitro. In heterozygous relatives, a partial decrease in plasma LPL activity was observed, sometimes associated with combined hyperlipidemia. This mutation previously unreported in other populations segregated on an identical haplotype, rarely observed in Caucasians, in both families. Therefore, LPL deficiency is a cause of familial chylomicronemia in Morocco and may result from a founder effect in patients of Berber ancestry.

Genetics of type III hyperlipoproteinemia

One hundred forty-seven relatives of 43 patients with "classical" type III hyperlipoproteinemia (HLP) having the apolipoprotein (apo) E2/2 phenotype were studied to determine the occurrence of hyperlipidemia and the presence of further possible genes for lipoprotein disorders in these families. In 12 pedigrees primary dyslipidemia was prevalent among patients and respective blood-relatives. In these kindreds the coexistent presence of genes for familial combined hyperlipidemia (n = 6), familial hypertriglyceridemia (n = 5), and familial hypercholesterolemia (n = 1), respectively, was supposed. Our results, therefore, confirm and extend previous data on the multifactorial genesis of the diseases. Besides homozygosity for a receptor binding-defective isoform of apo E (apo E2), additional genes for familial lipoprotein disorders might operate in the pathogenesis of type III HLP. This is the largest family study performed so far in this primary lipoprotein disorder.

Detection of missense mutations in the genes for lipoprotein lipase and hepatic triglyceride lipase in patients with dyslipidemia undergoing coronary angiography

Coronary events have a close association with a low HDL/hypertriglyceridemia (LHDL/HTG) phenotype. As enzymes that hydrolyze triglyceride-rich lipoproteins are associated with a modulation of both HDL cholesterol and triglycerides, we have tested the hypothesis that mutations in the genes encoding lipoprotein lipase (LPL) or hepatic lipase (HTGL) may contribute to the formation of coronary atherosclerosis and, thus, of coronary heart disease (CHD). The entire coding and boundary regions of LPL and HTGL genes were analyzed by direct sequencing in 20 patients with both LHDL/HTG and diagnosed CHD. In the LPL gene six different polymorphisms were identified with same frequencies observed in the general population. In the HTGL gene, besides several polymorphisms, we identified three missense mutations: Asn37His, Val73Met, and Ser267Phe. Population screening using allele specific PCR identified Val73Met as a polymorphism while the two others were absent from 100 control individuals. One of the mutations (Ser267Phe) is known to cause HTGL deficiency and is associated with type III hyperlipoproteinemia. Since this dyslipoproteinemia meets the criteria of LHDL/HTG, it is intriguing to speculate that missense mutations in HTGL may play a role in the pathogenesis of this atherogenic phenotype.

A multilocus genotyping assay for candidate markers of cardiovascular disease risk

A number of chronic diseases, including cardiovascular disease, appear to have a multifactorial genetic risk component. Consequently, techniques are needed to facilitate evaluation of complex genetic risk factors in large cohorts. We have designed a prototype assay for genotyping a panel of 35 biallelic sites that represent variation within 15 genes from biochemical pathways implicated in the development and progression of cardiovascular disease. Each DNA sample is amplified using two multiplex polymerase chain reactions, and the alleles are genotyped simultaneously using an array of immobilized, sequence-specific oligonucleotide probes. This multilocus assay was applied to two types of cohorts. Population frequencies for the markers were estimated using 496 unrelated individuals from a family-based cohort, and the observed values were consistent with previous reports. Linkage disequilibrium between consecutive pairs of markers within the apoCIII, LPL, and ELAM genes was also estimated. A preliminary analysis of single and pairwise locus associations with severity of atherosclerosis was performed using a composite cohort of 142 individuals for whom quantitative angiography data were available; evaluation of the potentially interesting associations observed will require analysis of an independent and larger cohort. This assay format provides a research tool for studies of multilocus genetic risk factors in large cardiovascular disease cohorts, and for the subsequent development of diagnostic tests.

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.

Functional variants in the lipoprotein lipase gene and risk cardiovascular disease

The current report is a quantitative review of the relationship between lipoprotein lipase gene variants and cardiovascular disease based on published population-based studies. Sixteen studies, representing 17,630 individuals, report allelic distribution for lipoprotein lipase gene variants among patients and control individuals. Patient outcomes included clinical cardiovascular disease events, documented coronary disease based on angiography, or intimal media thickening by B-mode ultrasonography. Mantel-Haenszel stratified analysis was used to compute a summary odds ratio and 95% confidence intervals for the association between rare allele in the lipoprotein lipase gene and disease status. Because of potential differing effects associated with different lipoprotein lipase variants, each lipoprotein lipase mutant allele was considered separately. The lipoprotein lipase D9N/-93G to T allele has a summary odds ratio of 2.03 (95% confidence interval 1.30-3.18), indicating a twofold increase in risk of coronary disease for carriers with this allelic variant. The summary odds ratio for the relationship of the rare lipoprotein lipase G188E variant with cardiovascular disease is 5.25 (95% confidence interval 1.54-24.29). The lipoprotein lipase N291S allele is associated with a marginal increase in cardiovascular disease (summary odds ratio 1.25, 95% confidence interval 0.99-1.60, P = 0.07). However, there is stronger evidence for a positive association in certain populations. The summary odds ratio for lipoprotein lipase S447X allele is 0.81 (95% confidence interval 0.65-1.0), which indicates a cardioprotective effect of this lipoprotein lipase gene variant. Thus, lipoprotein lipase gene variants are associated with differential susceptibility to cardiovascular disease.

A novel frameshift mutation in exon 6 (the site of Asn 291) of the lipoprotein lipase gene in type I hyperlipidemia

A new heterozygous lipoprotein lipase gene defect has been identified in a type I hyperlipidemic patient at the position of notable amino acid Asn 291. The patient is a 33-year-old male. His body mass index (BMI) was 18.5 kg/m2. The total cholesterol (TC), triglycerides (TG) and high density lipoprotein-cholesterol (HDL-C) concentration from his fasting plasma were 4.8, 11.9 and 0.4 mmol/l, respectively. The lipoprotein lipase (LPL) activity and mass in the postheparin plasma (PHP) from the patient were 0.58 mmol/ml/h (normal range: 7.7+/-2.6) and 244 ng/ml (normal range: 192+/-30), respectively. The hepatic lipase activity of the PHP from the patient was 10.6 mmol/ml/h (normal range: 9.9+/-3.6). DNA analysis of the LPL gene revealed that this patient had a heterozygous one nucleotide deletion of A coding Asn 291, resulting in a premature termination of the LPL protein at amino acid residue 303. The other abnormality in the LPL gene of the proband was an amino acid residue 194 defect (Ile194-->Thr), which is known to cause a defective enzyme. A medium-chain triglyceride (MCT) loading test was conducted to find how this triglyceride affects plasma lipoprotein metabolism in this patient in a short term (Fig. 3). The plasma total cholesterol (TC) or high density lipoprotein (HDL)-C levels did not change significantly after oral administration of a fatty meal containing long chain triglycerides (LCT) or MCT. The plasma TG level, on the other hand, increased from 11.9 to 19.2 mmol/l (+61%) at 6 h after loading a fatty meal containing LCT, whereas the plasma TG levels tended to even decrease at 6 h after oral administration of an MCT, tricaprin (from 11.6 to 10.5 mmol/l (-9.4%)). These results suggest that MCT, as opposed to LCT, is useful for treatment of type I hyperlipidemia with a novel mutation at the notable amino acid Asn 291 of the LPL gene.

Lipoprotein lipase compensates for the defective function of apo E variants in vitro by interacting with proteoglycans and lipoprotein receptors

Lipoprotein lipase (LPL) and apolipoprotein E (apo E) independently enhance binding and uptake of lipoproteins to cells. A coordinate effect of LPL and apo E has been previously described in human hepatozytes where simultaneous addition of both proteins resulted in an additive increase of chylomicron binding and uptake. The role of lipoprotein receptors and proteoglycans in this coordinate effect was now analysed using various cell types and heparinase treatment. To investigate a pathophysiological relevance, the effect of LPL and normal apo E-3 was compared to LPL and four apo E variants, associated with type III hyperlipoproteinemia (HLP). Apo E-3 and LPL increased the binding and uptake of chylomicrons and beta-very low density lipoproteins (VLDL) in an additive way in all cell types analysed, except proteoglycan deficient Chinese hamster ovary (CHO)-cells. Heparinase treatment almost completely abolished the effect of apo E and LPL. Addition of LPL to the apo E variants resulted in significant compensation of their defective function in mediating beta-VLDL binding to low density lipoprotein (LDL)-receptor defective fibroblasts. These findings indicate that the coordinate effect of apo E and LPL is mediated by proteoglycans and lipoprotein receptors, independent of the LDL receptor. LPL may compensate for the defective function of apo E variants by enhancing lipoprotein binding to these receptors. Defects in this mechanism may explain how mutations in the LPL molecule contribute to the manifestation of type III HLP in addition to the presence of a defective apo E.

Lipoprotein lipase mutations and Alzheimer's disease

Lipoprotein lipase (LPL) helps transfer lipids from lipoprotein particles to cells. In the brain, LPL is present in Alzheimer's disease (AD) amyloid plaques. LPL binds apolipoprotein E (ApoE) lipoprotein particles and low-density lipoprotein receptor-related protein (LRP), an ApoE receptor. Since polymorphisms in both ApoE and LRP influence AD risk, we sought to determine whether LPL mutations also affect AD risk. In a case-control study, the frequencies of two of the most common known LPL mutations were measured in European-Americans either clinically diagnosed or pathologically confirmed as AD or normal control (N) subjects. In clinically diagnosed subjects, the Ser447Ter mutation comprised 9.8% (62/630) of alleles in N and 3.8% (9/238) in AD, a significant difference (P = 0.0057), while the Asn291Ser mutation comprised 1.1% (5/460) of alleles in N and 5.1% (8/158) in AD, also a significant difference (P = 0.0073), though in pathologically confirmed subjects the allele frequencies for AD did not significantly differ from N for either mutation. In clinically diagnosed subjects, LPL mutations were associated with altered AD risk, suggesting a potential role for LPL in the causation of AD. Further studies in different populations should help clarify the questions raised by these results.

Influence of apolipoprotein E polymorphism on serum lipids and lipoprotein changes from childhood to adulthood: the Bogalusa Heart Study

The influence of apolipoprotein (apo) E polymorphism on serum lipoproteins from childhood to adulthood was examined in 1520 individuals, aged 5-14 years at baseline, followed over a 16-year period. At both times, the e2 allele associated with lower LDL cholesterol (P < 0.001) and higher HDL cholesterol (P < 0.05-0.01), the e4 allele with higher LDL cholesterol (P < 0.001). The e2 allele lowered the adulthood LDL cholesterol level to a greater extent than the childhood level (P < 0.05). With respect to tracking, at the lowest quartile of LDL cholesterol distribution, the persistence in ranks over time was higher in the apoE2 group with E2/3 and E2/2 phenotypes compared with the apoE3 group with E3/3 phenotype and the apoE4 group with E3/4 and E4/4 phenotypes (P = 0.001). Longitudinal increases in the ponderal index (weight/height3) lowered the adulthood HDL cholesterol to a larger extent in e2 carriers (P = 0.017). The interindividual variability in LDL cholesterol due to childhood and adulthood ponderal index was 1.8- to 2.3-fold greater in the apoE2 group versus the apoE3 group. Likewise, cigarette smoking, alcohol use and oral contraceptive use in adulthood explained greater variability in triglycerides (5.3-fold), VLDL cholesterol (7.8-fold) and HDL cholesterol (2.9-fold) in the apoE2 group versus the apoE3 group. Thus, the apoE locus influences not only the levels and tracking of certain lipoproteins from childhood to adulthood but also modulates the association between lifestyle-related factors and lipoproteins.

Receptor-mediated mechanisms of lipoprotein remnant catabolism

Chylomicron and VLDL are triglyceride-rich lipoprotein particles assembled by the intestine and liver respectively. These particles are not metabolized by the liver in their native form. However, upon entry into the plasma, their triglyceride component is rapidly hydrolyzed by lipoprotein lipase and they are converted to cholesterol-rich remnant particles. The remnant particles are recognized by the liver and rapidly cleared from the plasma. This process is believed to occur in two steps. (i) An initial sequestration of remnant particles on hepatic cell surface proteoglycans, and (ii) receptor-mediated endocytosis of remnants by hepatic parenchymal cells. The initial binding to proteoglycans may be facilitated by lipoprotein lipase and hepatic lipase which possess both lipid- and heparin-binding domains. The subsequent endocytic process may be mediated by LDL receptors and/or LRP. Both receptors have a high affinity for apoE, a major apolipoprotein component of remnant particles. The lipases may also serve as ligands for these receptors. An impairment of any component of this complex process may result in an accumulation of remnant particles in the plasma leading to atherosclerosis and coronary heart disease.

Common variation in the lipoprotein lipase gene: effects on plasma lipids and risk of atherosclerosis

The importance of the enzyme lipoprotein lipase (LPL) in the development of dyslipidaemia and atherosclerosis is increasingly recognised. Variations in the LPL gene which are common in the general population have been shown to be associated with alterations in plasma lipids. D9N and N291S both occur at carrier frequencies of up to about 5% and have been associated with increased plasma triacylglycerol and decreased high density lipoprotein cholesterol concentrations, effects which seem to be magnified in more obese individuals. S447X carrier frequency is approximately 20%, but unlike carriers of N9 or S291, X447 carriers appear to have a more favourable lipid profile. A transition within the LPL promoter at position-93 may lead to increased LPL activity and have a beneficial effect on plasma lipids. Greater knowledge of the underlying mechanisms of these variations within the LPL gene may be of considerable importance in understanding genetic predisposition to atherosclerosis and heart disease.

A common substitution (Asn291Ser) in lipoprotein lipase is associated with increased risk of ischemic heart disease

Lipoprotein lipase degrades triglycerides in plasma and as a byproduct produces HDL particles. Genetic variation in lipoprotein lipase may therefore affect cardiovascular risk. We tested 9,214 men and women from a general population sample and 948 patients with ischemic heart disease for the Asn291Ser substitution in lipoprotein lipase. The allele frequency in the general population was 0.024 and 0.026 for women and men, respectively. In comparison with noncarriers, female heterozygous probands had increased plasma triglycerides (delta = 0.23 mmol/liter), while HDL cholesterol was reduced in both female and male carriers (delta = 0.18 mmol/liter and delta = 0.11 mmol/liter, respectively). A similar phenotype was found in six homozygous carriers. On multiple logistic regression analysis, plasma triglycerides and HDL cholesterol were independent predictors of ischemic heart disease in both genders. On univariate analysis, odds ratios for ischemic heart disease in probands were 1.89 in women (95% CI: 1.19-3.01) and 0.90 in men (95% CI: 0.62-1.31), and on multivariate analysis were 1.98 in women (95% CI: 1.11-3.53) and 1.02 in men (95% CI: 0.65-1.60). This study demonstrates that a single common mutation in the lipoprotein lipase gene is associated with elevated plasma triglycerides and reduced HDL cholesterol levels, whereby carriers, in particular women, seem to be predisposed to ischemic heart disease. It cannot be excluded, however, that male carriers of this substitution may represent a subset of low-HDL individuals without raised triglycerides not predisposed to ischemic heart disease.

Lipoprotein lipase gene variants and risk of coronary disease: a quantitative analysis of population-based studies

The purpose of this study is to quantify the magnitude of the association between common variants in the lipoprotein lipase gene and coronary disease, based on published population-based studies. Fourteen studies, representing 15,708 subjects, report allelic distribution for lipoprotein lipase gene variants among coronary disease patients and control subjects. Patient outcomes included clinical coronary disease events and documented coronary disease based on angiography. Allele frequencies are estimated for disease and non-disease groups within each study. A 2 x 2 contingency table is used to compute individual study odds ratios and 95% confidence intervals, relating the presence of the rare allele to disease status. Mantel-Haenszel-stratified analysis of each allelic variant results in a summary odds ratio and 95% confidence interval for the association between each rare allele in the lipoprotein lipase gene and coronary disease. The lipoprotein lipase D9N allele has a summary odds ratio of 1.59 (95% confidence interval 1.03-2.55), indicating a 59% increase in risk of coronary disease for carriers with this allelic variant. The lipoprotein lipase N291S allele showed no association with coronary disease (summary odds ratio 0.93, 95% confidence interval 0.73-1.19). The summary odds ratio for lipoprotein lipase S447Ter allele is 0.81 (95% confidence interval 0.65-1.0), indicating a marginal negative association between this variant and coronary disease. The common lipoprotein lipase Pvu II polymorphism shows no relation to coronary disease (summary odds ratio 0.90, 95% confidence interval 0.80-1.01). The rare allele of the lipoprotein lipase HindIII polymorphism is negatively associated with coronary disease (summary odds ratio 0.84, 95% confidence interval 0.73-0.96). The lipoprotein lipase D9N allele is associated with high levels of triglyceride and low levels of high-density lipoprotein. Similar atherogenic lipid levels are observed in subjects with structural mutations lipoprotein lipase C188E and P207L. Carriers of the S447Ter allele have low levels of triglyceride. The lipoprotein, lipase gene variants which decrease lipoprotein lipase catalytic activity are associated with familial combined hyperlipidemia, but not the elevation of apolipoprotein B seen in this disorder. In conclusion, allelic variants in the lipoprotein lipase gene are associated with altered lipid levels and differential coronary disease risk.

Common sequence variants of lipoprotein lipase: standardized studies of in vitro expression and catalytic function

We have assessed the functional activity of three common sequence variants of human lipoprotein lipase (LPL). Two of these, Asn291Ser and Asp9Asn arise from missense mutations while the third, Ser447Ter, derives from a nonsense mutation, truncating LPL by two residues. As previous in vitro studies have produced conflicting results, we have re-analyzed the catalytic function of these variants using the COS cell transfection system, under optimized and standardized experimental protocols. We found the Asn291Ser variant to manifest with a decrease in catalytic activity (57% of normal) due to a reduction in secretion and stability of the active homodimeric form. The Asp9Asn variant also showed a significant decrease in catalytic activity (85% of normal), but this was found to be due to a decreased rate of secretion only, as the homodimeric form was stable. The findings for these mutants contrasted with those of the Ser447Ter truncation variant which proved to be catalytically normal; this variant also manifested normal homodimer stability. The truncated variant did however, present with a higher total secreted mass level (131%) than control LPL. This was most likely due to enhanced secretion of the monomeric form. None of these mutations exhibited defects in binding affinity to cell surface proteoglycans. Each of these variants deviated significantly from normal as regards to their secreted activity or mass levels in the COS cell transfection system.