👤 Miguel Pocoví

Most primary severe hypertriglyceridemias (HTGs) are diagnosed in adults, but their molecular foundations have not been completely elucidated. We aimed to identify rare dysfunctional mutations in genes encoding regulators of lipoprotein lipase (LPL) function in patients with familial and non-familial primary HTG. We sequenced promoters, exons, and exon-intron boundaries of LPL, APOA5, LMF1, and GPIHBP1 in 118 patients with severe primary HTG (triglycerides >500 mg/dL) and 53 normolipidemic controls. Variant functionality was analyzed using predictive software and functional assays for mutations in regulatory regions. We identified 29 rare variants, 10 of which had not been previously described: c.(-16A>G), c.(1018+2G>A), and p.(His80Arg) in LPL; p.(Arg143Alafs*57) in APOA5; p.(Val140Ile), p.(Leu235Ile), p.(Lys520*), and p.(Leu552Arg) in LMF1; and c.(-83G>A) and c.(-192A>G) in GPIHBP1. The c.(1018+2G>A) variant led to deletion of exon 6 in LPL cDNA, whereas the c.(-16A>G) analysis showed differences in the affinity for nuclear proteins. Overall, 20 (17.0%) of the patients carried at least one allele with a rare pathogenic variant in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant was not associated with lipid values, family history of HTG, clinical diagnosis, or previous pancreatitis. Less than one in five subjects with triglycerides >500 mg/dL and no major secondary cause for HTG may carry a rare pathogenic mutation in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant is not associated with a differential phenotype. Show less

The majority of hypertriglyceridemias are diagnosed as familial combined hyperlipidemia (FCHL) and primary isolated hypertriglyceridemias. The contribution of common genetic variants in primary hypertriglyceridemias and the genetic difference between FCHL and isolated hypertriglyceridemias have not been thoroughly examined. This study involved 580 patients with hypertriglyceridemias and 403 controls. Of the 37 single nucleotide polymorphisms examined, 12 located in 10 genes showed allelic and genotype frequency differences between hypertriglyceridemias and controls. The minor alleles of APOE, APOA5, GALNTN2, and GCKR variants were positively correlated with plasma triglycerides, whereas minor alleles of ADIPOR2, ANGPTL3, LPL, and TRIB1 polymorphisms were inversely associated. Body mass index, glucose, sex, rs328 and rs7007797 in LPL, rs662799 and rs3135506 in APOA5, and rs1260326 in GCKR explained 36% of the variability in plasma triglycerides, 7.3% of which was attributable to the genetic variables. LPL, GCKR, and APOA5 polymorphisms fit dominant, recessive, and additive inheritance models, respectively. Variants more frequently identified in isolated hypertriglyceridemias were rs7412 in APOE and rs1800795 in IL6; rs2808607 in CYP7A1 and rs3812316 and rs17145738 in MLXIPL were more frequent in FCHL. The other 32 single nucleotide polymorphisms presented similar frequencies between isolated hypertriglyceridemias and FCHL. Common genetic variants found in LPL, APOA5, and GCKR are associated with triglycerides levels in patients with primary hypertriglyceridemias. FCHL and isolated hypertriglyceridemias are probably trace to an accumulation of genetic variants predisposing to familial and sporadic hypertriglyceridemias or to hypertriglyceridemias and hypercholesterolemia in case of FCHL. Show less

Apolipoprotein A4 (apoA4) plays a role in intestinal lipid absorption. Several experimental interventions have shown that common variations at residues 347 (Thr --> Ser) and 360 (Gln --> His) on apoA4 are associated with differences in plasma lipid response to dietary fat; however, association studies between these variants and plasma lipid concentrations in populations reveal mixed results. We examined the effects of these polymorphisms in 758 randomly selected subjects (mean age 36.7+/-9.5 years) from 2 Spanish regions differing in latitude and fat intake: Aragón and Comunidad Valenciana. Subjects were matched one to one by sex and age. Frequencies for the less common alleles were similar in both regions: 0.096 (95% CI: 0.111-0.081) for codon 360 and 0.196 (95% CI: 0.216-0.176) for codon 347. In men and women there was no association between the codon 360 polymorphism and total cholesterol or triglyceride levels. However, subjects carrying the 360His allele had low-density lipoprotein (LDL) cholesterol concentrations statistically lower than homozygotes for the 360Gln allele, even after further adjustment for sex, age, region, body mass index, and APOE polymorphism (p = 0.043). The less common allele at codon 347 (the 347Ser allele) was associated with increased LDL-cholesterol concentrations with a clear gene-dosage effect after multivariate adjustment (p = 0.029). Although these polymorphisms showed no heterogeneity by geographic region, the magnitude of the effect was higher in subjects from Aragón compared with the Comunidad Valenciana, suggesting a possible influence of the higher fat intake in Aragón. In the combined association analysis subjects with the 360Gln/347Ser pseudohaplotype had the highest LDL-cholesterol concentrations, supporting the antagonistic effect between the 360His and the 347Ser alleles on this trait. Show less