👤 Sofía Pérez-Calahorra

Familial chylomicronemia syndrome (FCS) is an extremely rare lipoprotein disorder caused by mutations in at least 5 genes of the lipoprotein lipase (LPL) complex. This work shows the molecular analysis of patients diagnosed with FCS, who attended the Spanish Arteriosclerosis Society lipid units and were included in the National Dyslipidemia Registry. Among the 238 patients registered with severe hypertriglyceridemia (fasting triglycerides >1000 mg/dL), 26 were diagnosed with FCS as they had confirmed postheparin plasma LPL activity deficiency and/or homozygosity for loss-of-function mutations in LPL, GPIHBP1, APOC2, LMF1, or Apolipoprotein A5 (APOA5). Among the 26 FCS cases, 23 had mutations in the homozygous state: 19 in LPL and 4 in the GPIHBP1 gene. The molecular analysis revealed 3 novel mutations: 2 in LPL, in 2 unrelated patients (c.312delA; p.Asp105Thrfs*66 and c.629A>G; p.His210Arg), and 1 in GPHIBP1 in a third patient (c.502delC; p.Leu168Serfs*83). These 3 patients had confirmed lack of LPL activity. Three additional patients with confirmed LPL activity deficiency were heterozygous carriers of mutations in the genes analyzed. Among these, we found 2 novel mutations in APOA5 (c.50-1G>A and c.326₃₂₇insC; p.Tyr110Leufs*158). We have identified 5 novel pathogenic mutations: 2 in LPL, 1 in GPIHBP1, and 2 in the APOA5 gene. The genetic defaults accounting for the LPL activity deficiency of 23 of them have been clearly identified and 3 patients, who harbored mutations in heterozygosity, were diagnosed based on LPL activity deficiency, which raises the question of the involvement of new genes in the manifestation of FCS. Show less

Hypertriglyceridemia (HTG) is a common complex metabolic trait that results of the accumulation of relatively common genetic variants in combination with other modifier genes and environmental factors resulting in increased plasma triglyceride (TG) levels. The majority of severe primary hypertriglyceridemias is diagnosed in adulthood and their molecular bases have not been fully defined yet. The prevalence of HTG is highly variable among populations, possibly caused by differences in environmental factors and genetic background. However, the prevalence of very high TG and the frequency of rare mutations causing HTG in a whole non-selected population have not been previously studied. The total of 23,310 subjects over 18 years from a primary care-district in a middle-class area of Zaragoza (Spain) with TG >500 mg/dL were selected to establish HTG prevalence. Those affected of primary HTG were considered for further genetic analysis. The promoters, coding regions and exon-intron boundaries of LPL, LMF1, APOC2, APOA5, APOE and GPIHBP1 genes were sequenced. The frequency of rare variants identified was studied in 90 controls. One hundred ninety-four subjects (1.04%) had HTG and 90 subjects (46.4%) met the inclusion criteria for primary HTG. In this subgroup, nine patients (12.3%) were carriers of 7 rare variants in LPL, LMF1, APOA5, GPIHBP1 or APOE genes. Three of these mutations are described for the first time in this work. The presence of a rare pathogenic mutation did not confer a differential phenotype or a higher family history of HTG. The prevalence of rare mutations in candidate genes in subjects with primary HTG is low. The low frequency of rare mutations, the absence of a more severe phenotype or the dominant transmission of the HTG would not suggest the use of genetic analysis in the clinical practice in this population. Show less