👤 Gregorio Fariña

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive disorder characterized by extreme hypertriglyceridemia (>1000 mg/dL), recurrent pancreatitis, and lipoprotein lipase (LPL) deficiency. FCS is caused by biallelic loss-of-function variants in LPL or in 4 other genes encoding its cofactors and regulators, including LMF1 (lipase maturation factor 1). Variants in LMF1 are rare and present only in 1% to 2% of the FCS cases. To assess in 3 patients with severe hypertriglyceridemia and recurrent pancreatitis and in whom a homozygous LMF1 duplication, initially classified as a variant of uncertain significance (VUS) was identified, post-heparin LPL activity. We collected demographics, fasting lipid profiles, and body mass index, and performed next-generation sequencing using a targeted panel that included canonical FCS genes. A homozygous in-frame duplication in LMF1 (c.914₉₂₈dup; p.Ser309_Phe310dup) was identified. Variants were classified according to American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines and cross-referenced with public archive of reports of the relationships among human variations and phenotypes (ClinVar), The Human Gene Mutation Database at the Institute of Medical Genetics in Cardiff (HGMD), Leiden Open Variation Database (LOVD), The Single Nucleotide Polymorphism database (dbSNP), The Genome Aggregation Database (gnomAD), and in-house databases. LPL activity was assessed in post-heparin plasma using a radiometric assay. All 3 patients were homozygous for c.914₉₂₈dup (this variant was classified as a VUS) and exhibited markedly reduced LPL activity (<20% of normal). Clinical manifestations were consistent with FCS, including extreme triglyceride elevations and recurrent pancreatitis. One patient died from fulminant pancreatitis. The combined clinical, biochemical, and genetic evidence supports the reclassification of LMF1 c.914₉₂₈dup (p.Ser309_Phe310dup) as likely pathogenic according to ACMG/AMP guidelines and indicates its association with severe pancreatitis. Show less

A case of a 29-year-old female patient with a history of a single episode of hypertriglyceridemia-induced pancreatitis 4 years prior is reported. She had been treated with fibrates until 2 months before conception and required hospitalization at 33 weeks of gestation due to severe hypertriglyceridemia (6690 mg/dL) and gestational diabetes. Upon hospital admission, there was no evidence of pancreatitis. A comprehensive treatment approach was initiated, combining a low-fat diet, fibrates, omega-3 fatty acids (2 g/d), and continuous insulin infusion. This regimen resulted in a significant reduction of triglyceride levels to 960 mg/dL. The pregnancy progressed to full term without any maternal-fetal complications. Genetic analysis revealed 2 compound heterozygous mutations in the APOA5 gene, which encodes apolipoprotein AV. Notably, these specific mutations have not been previously reported as causative factors for familial chylomicronemia syndrome (FCS). The diagnosis of FCS was confirmed by the patient's markedly reduced lipoprotein lipase activity of 3.2%. Show less

Intestinal remnant chylomicrons (CMs) are involved in cardiovascular residual risk and the atherogenic process. Microsomal triglyceride transfer protein (MTTP) catalyzes the assembly of lipids to apolipoprotein B48, generating CMs. Dysbiosis could alter this behavior. This study investigated the chemical composition of CMs and their associations with intestinal MTTP and gut fat depots in a diet-induced dysbiosis animal model. Male Wistar rats were fed either a standard diet (control, n=10) or a high-fat high-sucrose diet (HFSD, n=10) for 14 weeks. Measurements included serum glucose, lipid-lipoprotein profile, free fatty acids (FFAs), lipopolysaccharide (LPS) and the Compared to control, HFSD rats showed higher levels of LPS, triglycerides (TGs), non-high-density lipoprotein cholesterol (HDL-C) levels, TG/HDL-C ratio, FFAs, and the F/B ratio. HFSD CMs showed increased TG and phospholipids. TJ proteins levels were lower in the HFSD group, while histological scores showed no differences. CIF was increased in the HFSD group. No significant differences in apoB mRNA were found. MTTP expression was higher in the HFSD group, and directly correlated with CM-TG and inversely correlated with CIF. Our findings imply that gut TG content may constitute an important determinant of the secretion of TG-rich CMs, promoted by MTTP, with increased atherogenic potential. Show less

Given that lipoprotein lipase (LPL) activity assays are not standardized for clinical use, we aimed to define reference values applicable to our clinical setting and identify a cut-off point to help distinguish Familial Chylomicronemia Syndrome from Multifactorial Chylomicronemia Syndrome, particularly in patients with inconclusive genetic findings. We evaluated 28 patients with a history of TG levels above 880 mg/dL (10 mmol/L), and assessed their likelihood of FCS using the Moulin score. LPL activity was measured in post-heparin plasma using a radiometric assay. Thirty normotriglyceridemic controls were used to define reference values. Genetic testing for FCS canonical genes and lipid profile was performed in all sHTG patients. The reference value for LPL activity was 33.3 (18.7-70.3) mIU, with a cut-off of 8.42 mIU (25 % of the median of NTG) to distinguish FCS from MCS. Eighteen patients without genetic variants in canonical genes, a Moulin score <9 and LPL activity >25 % of NTG, were classified as MCS. Five genetic diagnosed FCS patients, with a Moulin score>10 presented LPL activity <25 % of NTG. Four patients with inconclusive genetic results and a Moulin score>10 were classified as FCS according to LPL activity. LPL activity in patients with sHTG could be useful for differentiating FCS and MCS, particularly in patients with ambiguous or negative genetic findings, highlighting the need for specialized laboratory support in diagnostics. Show less

Familial chylomicronemia syndrome (FCS) is a rare monogenic disorder characterized by severe hypertriglyceridemia caused by pathogenic variants in genes involved in triglyceride metabolism. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) plays a critical role in the lipolytic processing of triglyceride-rich lipoproteins. We present 3 unrelated cases of FCS with a newly identified homozygous complex insertion-deletion variant in GPIHBP1, namely c.460₄₆₁delinsAAA, p.Ala154Lysfs*153. All 3 cases presented with severe hypertriglyceridemia, a high FCS clinical score, and significantly reduced lipoprotein lipase (LPL) activity (being 6.6 mUI the value corresponding to 20% of normal activity). These observations expand the spectrum of pathogenic GPIHBP1 variants in FCS. The identification of GPIHBP1 variant reinforces the causal link between GPIHBP1 mutations and LPL deficiency, as evidenced by diminished LPL activity, and further expands the genetic landscape of FCS. Show less

This study aims to investigate if a mixture of functional lipids (FLs), containing conjugated linoleic acid (CLA), tocopherols (TPs), and phytosterols (PSs), prevents some lipid alterations induced by high-fat (HF) diets, without adverse effects. Male CF1 mice (n = 6/group) were fed (4 weeks) with control (C), HF, or HF + FL diets. FL prevented the overweight induced by the HF diet and reduced the adipose tissue (AT) weight, associated with lower energy efficiency. After the intervention period, the serum triacylglycerol (TAG) levels in both HF diets underwent a decrease associated with an enhanced LPL activity (mainly in muscle). The beneficial effect of the FL mixture on body weight gain and AT weight might be attributed to the decreased lipogenesis, denoted by the lower mRNA levels of SREBP1-c and ACC in AT, as well as by an exacerbated lipid catabolism, reflected by increased mRNA levels of PPARα, ATGL, HSL, and UCP2 in AT. Liver TAG levels were reduced in the HF + FL group due to an elevated lipid oxidation associated with a higher CPT-1 activity and mRNA levels of PPARα and CPT-1a. Moreover, genes linked to fatty acid biosynthesis (SREBP1-c and ACC) showed decreased mRNA levels in both HF diets, this finding being more pronounced in the HF + FL group. The administration of an FL mixture (CLA + TP + PS) prevented some lipid alterations induced by a HF diet, avoiding frequent deleterious effects of CLA in mice through the modulation of gene expression related to the regulation of lipid metabolism. Show less