Gene Therapy With Lipoprotein Lipase Variant S447X

Genetic polymorphism of S447X lipoprotein lipase (LPL) and the susceptibility to hypertension

INTRODUCTION

Lipoprotein lipase (LPL) is a rate-limiting enzyme responsible for the hydrolysis of triacylglycerol-rich lipoproteins releasing monoglycerides and free fatty acids, which are taken up by skeletal muscles and adipose tissue. S447X polymorphism in exon 9 of LPL gene on chromosome 8 p22 results from replacement of serine amino acid with a stop codon creating a restriction site. It has been hypothesized that the more common SS genotype is associated with a lower LPL activity compared with the infrequent SX/XX genotype.

OBJECTIVES

To investigate the effect of genetic polymorphism of LPL S447X in blood pressure and its atherogenic phenotype.

MATERIALS AND METHODS

S447X variant genotype of LPL were determined by polymerase reaction (PCR) restriction fragment length polymorphism assay in 50 hypertensive patients and 50 normotensive as a control group. Anthropometric measurements and serum lipoproteins were also determined in both groups.

RESULTS

The frequency of (SS) genotype was 78% in hypertensive group compared to 66% in normotensive group. Carrier of (SS) genotype were at higher risk of developing hypertension (OR, 1.8; 95% CI, 0.8-4.4) when compared with carrier of other genotypes. Furthermore, they showed atherogenic phenotype manifested by central obesity and dyslipidemia. Odds ratios were 1.8 and 2.6, respectively.

CONCLUSION

It was found that carriers of (SS) genotype were at high risk of developing hypertension.

Novel LPL mutations associated with lipoprotein lipase deficiency: two case reports and a literature review

Lipoprotein lipase (LPL) is a key enzyme involved with hydrolysis and removal of triglycerides from plasma. LPL deficiency is a rare condition with an estimated prevalence of 1 in 106. It is characterized biochemically by elevated triglycerides and lowered HDL in the plasma and clinically by a constellation of signs and symptoms during childhood including failure to thrive, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly, and acute pancreatitis. Nearly 100 mutations in the LPL gene have been associated with LPL deficiency. Here we report 2 unrelated pedigrees with LPL deficiency from 2 novel disease-causing LPL mutations: a Gly159Glu missense mutation in exon 5 and a 4-bp ACGG deletion at the 3' boundary of exon 2. We present molecular findings of these 2 cases and review the biochemical, clinical, and genetic features of LPL deficiency.

Genetic differences between the determinants of lipid profile phenotypes in African and European Americans: the Jackson Heart Study

Genome-wide association analysis in populations of European descent has recently found more than a hundred genetic variants affecting risk for common disease. An open question, however, is how relevant the variants discovered in Europeans are to other populations. To address this problem for cardiovascular phenotypes, we studied a cohort of 4,464 African Americans from the Jackson Heart Study (JHS), in whom we genotyped both a panel of 12 recently discovered genetic variants known to predict lipid profile levels in Europeans and a panel of up to 1,447 ancestry informative markers allowing us to determine the African ancestry proportion of each individual at each position in the genome. Focusing on lipid profiles -- HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), and triglycerides (TG) -- we identified the lipoprotein lipase (LPL) locus as harboring variants that account for interethnic variation in HDL-C and TG. In particular, we identified a novel common variant within LPL that is strongly associated with TG (p = 2.7 x 10(-6)) and explains nearly 1% of the variability in this phenotype, the most of any variant in African Americans to date. Strikingly, the extensively studied "gain-of-function" S447X mutation at LPL, which has been hypothesized to be the major determinant of the LPL-TG genetic association and is in trials for human gene therapy, has a significantly diminished strength of biological effect when it is found on a background of African rather than European ancestry. These results suggest that there are other, yet undiscovered variants at the locus that are truly causal (and are in linkage disequilibrium with S447X) or that work synergistically with S447X to modulate TG levels. Finally, we find systematically lower effect sizes for the 12 risk variants discovered in European populations on the African local ancestry background in JHS, highlighting the need for caution in the use of genetic variants for risk assessment across different populations.

Association of lipase lipoprotein polymorphisms with myocardial infarction and lipid levels

BACKGROUND

Lipoprotein lipase has an important role in lipid metabolism. Elevated levels of very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) are associated with increased risk of coronary artery disease and low levels of high-density lipoprotein (HDL) are potentially atherogenic. The HindIII and S447X polymorphisms of the lipoprotein lipase (LPL) gene are associated with cardiovascular disease in some populations.

METHODS

LPL HindIII and S447X polymorphisms were analyzed in 343 individuals of 66-97 years of age from a cohort of a Brazilian elderly longitudinal study. Allele frequencies, genotype distribution and allele association with major morbidities and with serum lipid, urea, creatinine and albumin levels were also investigated. The whole sample was genotyped by PCR-restriction fragment length polymorphism (RFLP). Descriptive statistics, logistic regression analysis and t-test were used.

RESULTS

Allele frequencies were H(+)=0.652 and H(-)=0.348 for LPL HindIII and S=0.824 and X=0.176 for LPL S447X polymorphism. Both polymorphisms have frequencies similar to those in some European populations. LPL HindIII polymorphism showed significant association of the H(+) allele with myocardial infarction. The H(-) allele showed a tendency to associate with higher HDL levels. The LPL S447X S allele was associated with higher triglyceride levels.

CONCLUSIONS

These findings may help to identify risk factors for subjects and families and clarify the physiopathological role of these polymorphisms in age-related diseases.