Lipoprotein Lipase Deficiency Research Articles

A novel lipoprotein lipase mutation in familial chylomicronemia syndrome - two case reports

A novel lipoprotein lipase mutation in familial chylomicronemia syndrome - two case reports

Familial chylomicronemia syndrome: case reports of siblings with deletions of the GPIHBP1 gene

BackgroundFamilial chylomicronemia syndrome (FCS) is a rare monogenic form of severe hypertriglyceridemia, caused by mutations in genes involved in triglyceride metabolism. Herein, we report the case of a Korean family with familial chylomicronemia syndrome caused by compound heterozygous deletions of glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1).Case presentationA 4-year-old boy was referred for the evaluation of severe hypertriglyceridemia (3734 mg/dL) that was incidentally detected 4 months prior. His elder brother also demonstrated an elevated triglyceride level of 2133 mg/dL at the age of 9. Lipoprotein electrophoresis revealed the presence of chylomicrons, an increase in the proportion of pre-beta lipoproteins, and low serum lipoprotein lipase levels. The patient’s parents and first elder brother had stable lipid profiles. For suspected FCS, genetic testing was performed using the next-generation sequencing-based analysis of 31 lipid metabolism-associated genes, which revealed no pathogenic variants. However, copy number variant screening using sequencing depth information suggested large heterozygous deletion encompassing all the coding exons of GPIHBP1. A real-time quantitative polymerase chain reaction was performed to validate the deletion site. The results showed that the siblings had two heterozygous copy number variants consisting of the whole gene and an exon 4 deletion, each inherited from their parents. During the follow-up period of 17 months, the patient did not develop pancreatitis, following dietary intervention.ConclusionThese siblings’ case of familial chylomicronemia syndrome caused by rare GPIHBP1 deletions highlight the implementation of copy number variants—beyond next-generation sequencing—as an important consideration in diagnosis. Accurate genetic diagnosis is necessary to establish the etiology of severe hypertriglyceridemia, which increases the risk of pancreatitis.

Olezarsen, Acute Pancreatitis, and Familial Chylomicronemia Syndrome.

Familial chylomicronemia syndrome is a genetic disorder associated with severe hypertriglyceridemia and severe acute pancreatitis. Olezarsen reduces the plasma triglyceride level by reducing hepatic synthesis of apolipoprotein C-III. In a phase 3, double-blind, placebo-controlled trial, we randomly assigned patients with genetically identified familial chylomicronemia syndrome to receive olezarsen at a dose of 80 mg or 50 mg or placebo subcutaneously every 4 weeks for 53 weeks. There were two primary end points: the difference between the 80-mg olezarsen group and the placebo group in the percent change in the fasting triglyceride level from baseline to 6 months, and (to be assessed if the first was significant) the difference between the 50-mg olezarsen group and the placebo group. Secondary end points included the mean percent change from baseline in the apolipoprotein C-III level and an independently adjudicated episode of acute pancreatitis. A total of 66 patients underwent randomization; 22 were assigned to the 80-mg olezarsen group, 21 to the 50-mg olezarsen group, and 23 to the placebo group. At baseline, the mean (±SD) triglyceride level among the patients was 2630±1315 mg per deciliter, and 71% had a history of acute pancreatitis within the previous 10 years. Triglyceride levels at 6 months were significantly reduced with the 80-mg dose of olezarsen (-43.5%; 95% confidence interval [CI], -69.1 to -17.9; P<0.001) but not with the 50-mg dose (-22.4%; 95% CI, -47.2 to 2.5; P = 0.08). The difference in the mean percent change in the apolipoprotein C-III level from baseline to 6 months in the 80-mg group as compared with the placebo group was -73.7% (95% CI, -94.6 to -52.8) and between the 50-mg group as compared with the placebo group was -65.5% (95% CI, -82.6 to -48.3). By 53 weeks, 11 episodes of acute pancreatitis had occurred in the placebo group, and 1 episode had occurred in each olezarsen group (rate ratio [pooled olezarsen groups vs. placebo], 0.12; 95% CI, 0.02 to 0.66). Adverse events of moderate severity that were considered by a trial investigator at the site to be related to the trial drug or placebo occurred in 4 patients in the 80-mg olezarsen group. In patients with familial chylomicronemia syndrome, olezarsen may represent a new therapy to reduce plasma triglyceride levels. (Funded by Ionis Pharmaceuticals; Balance ClinicalTrials.gov number, NCT04568434.).

Significant but partial lipoprotein lipase functional loss caused by a novel occurrence of rare LPL biallelic variants

BackgroundLipoprotein lipase (LPL) plays a crucial role in triglyceride hydrolysis. Rare biallelic variants in the LPL gene leading to complete or near-complete loss of function cause autosomal recessive familial chylomicronemia syndrome. However, rare biallelic LPL variants resulting in significant but partial loss of function are rarely documented. This study reports a novel occurrence of such rare biallelic LPL variants in a Chinese patient with hypertriglyceridemia-induced acute pancreatitis (HTG-AP) during pregnancy and provides an in-depth functional characterization.MethodsThe complete coding sequences and adjacent intronic regions of the LPL, APOC2, APOA5, LMF1, and GPIHBP1 genes were analyzed by Sanger sequencing. The aim was to identify rare variants, including nonsense, frameshift, missense, small in-frame deletions or insertions, and canonical splice site mutations. The functional impact of identified LPL missense variants on protein expression, secretion, and activity was assessed in HEK293T cells through single and co-transfection experiments, with and without heparin treatment.ResultsTwo rare LPL missense variants were identified in the patient: the previously reported c.809G > A (p.Arg270His) and a novel c.331G > C (p.Val111Leu). Genetic testing confirmed these variants were inherited biallelically. Functional analysis showed that the p.Arg270His variant resulted in a near-complete loss of LPL function due to effects on protein synthesis/stability, secretion, and enzymatic activity. In contrast, the p.Val111Leu variant retained approximately 32.3% of wild-type activity, without impacting protein synthesis, stability, or secretion. Co-transfection experiments indicated a combined activity level of 20.7%, suggesting no dominant negative interaction between the variants. The patient’s post-heparin plasma LPL activity was about 35% of control levels.ConclusionsThis study presents a novel case of partial but significant loss-of-function biallelic LPL variants in a patient with HTG-AP during pregnancy. Our findings enhance the understanding of the nuanced relationship between LPL genotypes and clinical phenotypes, highlighting the importance of residual LPL function in disease manifestation and severity. Additionally, our study underscores the challenges in classifying partial loss-of-function variants in classical Mendelian disease genes according to the American College of Medical Genetics and Genomics (ACMG)’s variant classification guidelines.

Drug target Mendelian randomization supports apolipoprotein C3-lowering for lipoprotein-lipid levels reductions and cardiovascular diseases prevention

Background and aimsInhibitors of apolipoprotein C-III (apoC3) are currently approved for the reduction of triglyceride levels in patients with Familial Chylomicronemia Syndrome. We used drug target Mendelian randomization (MR) to assess the effect of genetically predicted decrease in apoC3 blood protein levels on cardiometabolic traits and diseases. MethodsWe quantified lifelong reductions in apoC3 blood levels by selecting all genome wide significant and independent (r2<0.1) single nucleotide polymorphisms (SNPs) in the APOC3 gene region ±1 Mb, from three genome-wide association studies (GWAS) of apoC3 blood protein levels (deCODE, n = 35,378, Fenland, n = 10,708 and ARIC, n = 7213). We included the largest GWASes on 18 cardiometabolic traits and 9 cardiometabolic diseases as study outcomes. ResultsA one standard deviation lowering in apoC3 blood protein levels was associated with lower triglycerides, apolipoprotein B, low-density lipoprotein cholesterol, alanine aminotransferase, and glomerular filtration rate as well as higher high-density lipoprotein cholesterol levels. ApoC3 lowering was also associated with lower risk of acute pancreatitis (odds ratio [OR] = 0.91 95% CI = 0.82 to 1.00), aortic stenosis (OR = 0.82 95% CI = 0.73 to 0.93), and coronary artery disease (OR = 0.86 95% CI = 0.80 to 0.93), and was associated with increased parental lifespan (0.06 95% CI = 0.03–0.09 years). These results were concordant across robust MR methods, the three protein datasets and upon adjustment for APOA1, APOA4 and APOA5 using a multivariable MR framework. ConclusionsThese results provide evidence that apoC3 lowering could result in widespread benefits for cardiometabolic health and encourage the launch of trials on apoC3 inhibition for coronary artery disease prevention.

High hsCRP concentration is associated with acute pancreatitis in multifactorial chylomicronemia syndrome.

Multifactorial chylomicronemia syndrome (MCS) is a severe form of hypertriglyceridemia (hyperTG) associated with an increased risk of acute pancreatitis (AP). However, the risk of AP is very heterogenous in MCS. Previous studies suggested that inflammation might promote disease progression in hyperTG-induced AP. To determine if low-grade inflammation is associated with AP in MCS. This study included 102 subjects with MCS for which high-sensitivity C-reactive protein (hsCRP) concentration was measured at their first visit at the Montreal Clinical Research Institute. MCS subjects with a previous history of AP had a significant higher hsCRP concentration (4.62 mg/L vs. 2.61 mg/L; p=0.003) and high hsCRP concentration (≥3mg/L) was independently associated with AP prevalence (p<0.05). Up to 64% of the variability in AP prevalence was explained by the maximal TG concentration, hsCRP concentration, the presence of rare variants in TG-related genes, and fructose intake based on a stepwise multivariate regression model (p<0.0001). This retrospective study showed for the first time that hsCRP concentration is strongly associated with AP prevalence in MCS. It also suggests that low-grade inflammation may be a driver of AP in severe hypertriglyceridemia. Prospective studies could help determine the causality of this association and assess whether medication known to reduce low-grade inflammation could help prevent AP in individuals with severe hypertriglyceridemia.

Cell Culture Media Optimization for Increased Production of Recombinant Proteins in Insect Cells

The insect cell/baculovirus expression system (IC-BEVS) has been at the forefront of biotechnologicalresearch, and has served as a tool to produce several human therapeutics such asCervavix ® (preventative vaccine against the human papilloma Virus), Flublok ® (preventativevaccine against seasonal influenza virus), Provenge ® (therapeutic treatment against prostatecancer) and Glybera ® (gene therapy treatment for lipoprotein lipase deficiency). IC-BEVS isan attractive alternative to mammalian cells for biomanufacturing as it offers advantages suchas easy adaptation to serum-free media, high levels of protein expression and post-translationalmodifications, and is appropriately scalable for manufacturing 2. Despite these advantages,the use of IC-BEVS to produce recombinant proteins can be costly and time-consuming.As the demand for new therapeutic increases, efficient, and robust methods to improvethe production and screening processes of recombinant proteins in this expression systemare necessary to respond to large-scale manufacturing needs. Research has shown that tailoredmedia supplementation and optimization is an efficient, and useful strategy to reachhigh density cultures and increase protein production in-vitro. Therefore, this project aimed toevaluate the effects of two macromolecules (glucose in high concentration, and glutathione)as potential cell culture additives or boosters to increase the production of therapeutic proteinsin the baculovirus/insect cell expression system. It was demonstrated that glutathioneaddition resulted in a more rapid, universal production of protein compared to minimal media,suggesting this to be a valuable addition to IC-BEVS media.

Breaking the chains of lipoprotein lipase deficiency: A pediatric perspective on the efficacy and safety of Volanesorsen

RationaleLipoprotein lipase (LPL) deficiency, a rare inherited metabolic disorder, is characterized by high triglyceride (TG) levels and life-threatening acute pancreatitis. Current treatment for pediatric patients involves a lifelong severely fat-restricted diet, posing adherence challenges. Volanesorsen, an EMA-approved RNA therapy for adults, effectively reduces TG levels by decreasing the production of apolipoprotein C-III. This 96-week observational open-label study explores Volanesorsen's safety and efficacy in a 13-year-old female with LPL deficiency. MethodsThe patient, with a history of severe TG elevations, 53 hospital admissions, and life-threatening recurrent pancreatitis despite dietary restrictions, received weekly subcutaneous Volanesorsen injections. We designed a protocol for this investigator-initiated study, primarily focusing on changes in fasting TG levels and hospital admissions. ResultsWhile the injections caused occasional pain and swelling, no other adverse events were observed. TG levels decreased during treatment, with more measurements below the pancreatitis risk threshold compared to pre-treatment. No hospital admissions occurred in the initial 14 months of treatment, contrasting with 21 admissions in the 96 weeks before. In the past 10 months, two pancreatitis episodes may have been linked to dietary noncompliance. Dietary restrictions were relaxed, increasing fat intake by 65% compared to baseline. While not fully reflected in the PedsQL, both parents and the patient narratively reported an improved quality of life. ConclusionThis study demonstrates, for the first time, that Volanesorsen is tolerated in a pediatric patient with severe LPL deficiency and effectively lowers TG levels, preventing life-threatening complications. This warrants consideration for expanded access in this population.

Cross-Sectional Quantitative Evaluation of a Novel Patient-Reported Outcome Measure in Familial Chylomicronemia Syndrome.

Familial chylomicronemia syndrome (FCS) is a rare metabolic disorder that impacts physical, emotional, social, and cognitive functioning. The FCS-Symptom and Impact Scale (FCS-SIS) patient-reported outcome (PRO) measure assesses common symptoms and impacts of FCS. This study was conducted to evaluate cross-sectional psychometric properties of the FCS-SIS and its scoring method. This multisite, cross-sectional, observational study of individuals with FCS was conducted in the United States and Canada. Participants completed a survey composed of 7 PRO measures, including the FCS-SIS, and questions about clinical characteristics and demographics. The structure of the FCS-SIS was evaluated using inter-item and item-scale correlations and internal consistency reliability. Construct, known-groups, and criterion validity were evaluated by examining associations between FCS-SIS item and composite scores and other measures included within the survey. Most of the 33 participants were female (63.6%) and White (78.1%). On average, participants reported first noticing FCS symptoms at ~16 years, with abdominal pain the most frequently reported initial symptom (n=20). Participants reported 2.5 acute pancreatitis attacks on average over the past year. Average FCS-SIS symptom item scores ranged from 1.8 to 3.9 (on a 0-to-10 scale [none-to-worst-possible]) within the 24-hour recall period, with an average Symptom composite score of 2.7. The average impact item scores on the FCS-SIS ranged from 1.6 to 3.0 (on a 0-to-4 scale), with an average Impact composite score of 2.1. Inter-item correlations between the FCS-SIS Symptom items ranged from 0.32 to 0.78. Corrected item-total correlations were highly satisfactory for Impact items, ranging from 0.62 to 0.85. All a priori validity hypotheses were supported by observed correlations and score differences between known groups. The results of this study support the structure, reliability, and validity of the FCS-SIS, laying the psychometric groundwork for longitudinal evaluation of its utility in assessing treatment benefit in FCS clinical studies.

Validation of the familial chylomicronaemia syndrome (FCS) score in an ethnically diverse cohort from UK FCS registry: Implications for diagnosis and differentiation from multifactorial chylomicronaemia syndrome (MCS)

Background and aimsPrognosis and management differ between familial chylomicronaemia syndrome (FCS), a rare autosomal recessive disorder, and multifactorial chylomicronaemia syndrome (MCS) or severe mixed hyperlipidaemia. A clinical scoring tool to differentiate these conditions has been devised but not been validated in other populations. The objective of this study was to validate this score in the UK population and identify any additional factors that might improve it. MethodsA retrospective validation study was conducted using data from 151 patients comprising 75 FCS and 76 MCS patients. All participants had undergone genetic testing for genes implicated in FCS. Validation was performed by standard methods. Additional variables were identified from clinical data by logistic regression analysis. ResultsAt the recommended FCS score threshold ≥10 points, the sensitivity and specificity of the score in the UK population were 96% and 75%, respectively. The receiver operating characteristic (ROC) curve analysis yielded an area under the curve (AUC) of 0.88 (95% CI 0.83–0.94, p < 0.001). This study identified non-European (predominantly South Asian) ethnicity, parental consanguinity, body mass index (BMI) < 25 kg/m2, and recurrent pancreatitis as additional positive predictors, while BMI >30 kg/m2 was found to be a negative predictor for FCS. However, inclusion of additional FCS predictors had no significant impact on performance of standard FCS score. ConclusionsOur study validates the FCS score in the UK population to distinguish FCS from MCS. While additional FCS predictors were identified, they did not improve further the score diagnostic performance.

Long-term clinical outcomes and management of hypertriglyceridemia in children with Apo-CII deficiency

Background and aimAPO CII, one of several cofactors which regulate lipoprotein lipase enzyme activity, plays an essential role in lipid metabolism. Deficiency of APO CII is an ultra-rare autosomal recessive cause of familial chylomicronemia syndrome. We present the long-term clinical outcomes of 12 children with APO CII deficiency. Methods and resultsThe data of children with genetically confirmed APO CII deficiency were evaluated retrospectively. Twelve children (8 females) with a mean follow-up of 10.1 years (±3.9) were included. At diagnosis, the median age was 60 days (13 days-10 years). Initial clinical findings included lipemic serum (41.6%), abdominal pain (41.6%), and vomiting (16.6%). At presentation, the median triglyceride (TG) value was 4341 mg/dL (range 1277–14,110). All patients were treated with a restricted fat diet, medium-chain triglyceride (MCT), and omega-3-fatty acids. In addition, seven patients (58.3%) received fibrate. Fibrate was discontinued in two patients due to rhabdomyolysis and in one patient because of cholelithiasis. Seven (58.3%) patients experienced pancreatitis during the follow-up period. One female experienced recurrent pancreatitis and was treated with fresh frozen plasma (FFP). ConclusionsApo CII deficiency is an ultra-rare autosomal recessive condition of hypertriglyceridemia associated with significant morbidity and mortality. Low-fat diet and MCT supplementation are the mainstays of therapy, while the benefit of TG-lowering agents are less well-defined.

Pancreatitis polygenic risk score is associated with acute pancreatitis in multifactorial chylomicronemia syndrome

Multifactorial chylomicronemia syndrome (MCS) is a severe form of hypertriglyceridemia associated with an increased risk of acute pancreatitis (AP). The risk of AP is heterogenous and is associated with increased level of triglycerides (TG) and presence of rare variants in TG metabolism-related genes. To determine if the accumulation of common variants in pancreatitis susceptibility genes, measured with a weighted polygenic risk score (PRS), is associated with AP in MCS patients. A total of 114 patients with MCS underwent genetic testing for eight single nucleotide polymorphisms (SNPs) in known pancreatitis susceptibility genes (ABCG8, CLDN2, CTRB1/2, CTRC, PRSS1, PRSS2, SPINK1 and TWIST2). A weighted PRS was calculated to account for the phenotypic effect of each SNP locus. A high pancreatitis-PRS score (≥ 0.44) was associated with a 2.94-fold increase risk of AP (p = 0.02) among patients with MCS. MCS patients with a high pancreatitis-PRS and a rare variant in TG metabolism-related gene have a 9.50-fold increase risk of acute pancreatitis (p = 0.001), compared to those with a low-PRS and no rare variant. A multivariate analysis including the presence of rare variants, the maximal TG values and a high pancreatitis-PRS explained 26% of the variability in AP in MCS patients. This study shows for the first time that the accumulation of common variants in pancreatitis susceptibility genes is associated with AP in MCS patients. Pancreatitis-PRS could help clinicians to identify MCS patients who may be at higher risk of AP and who may benefit from more aggressive treatment.

Acute pancreatitis risk in multifactorial chylomicronemia syndrome depends on the molecular cause of severe hypertriglyceridemia

Multifactorial chylomicronemia syndrome (MCS) is a severe form of hypertriglyceridemia (hyperTG) associated with an increased risk of acute pancreatitis (AP). Severe hyperTG is mainly polygenic in nature, either caused by the presence of heterozygous pathogenic variants (PVs) in TG-related metabolism genes or by accumulation of common variants in hyperTG susceptibility genes. This study aims to determine if the risk of AP is similar amongst MCS patients with different molecular causes of severe hyperTG. This study included 114 MCS patients who underwent genetic testing for PVs in TG-related metabolism genes and 16 single nucleotide polymorphisms (SNPs) in hyperTG susceptibility genes. A weighted TG-polygenic risk score (TG-PRS) was calculated. A TG-PRS score ≥ 90th percentile was used to define a high TG-PRS. Overall, 66.7% of patients had severe hyperTG of polygenic origin. MCS patients with only a PV and those with both a PV and high TG-PRS were more prone to have maximal TG concentration ≥ 40mmol/L (OR 5.33 (1.55-18.36); p=0.008 and OR 5.33 (1.28-22.25); p=0.02), as well as higher prevalence of AP (OR 3.64 (0.89-14.92); p=0.07 and OR 11.90 (2.54-55.85); p=0.002) compared to MCS patients with high TG-PRS alone. This is the first study to show that MCS caused by a high TG-PRS and a PV is associated with higher risk of AP, similar to what is seen in the monogenic form of severe hyperTG. This suggests that determining the molecular cause of severe hyperTG could be useful to stratify the risk of pancreatitis in MCS.

Understanding Hypertriglyceridemia: Integrating Genetic Insights.

Hypertriglyceridemia is an exceptionally complex metabolic disorder characterized by elevated plasma triglycerides associated with an increased risk of acute pancreatitis and cardiovascular diseases such as coronary artery disease. Its phenotype expression is widely heterogeneous and heavily influenced by conditions as obesity, alcohol consumption, or metabolic syndromes. Looking into the genetic underpinnings of hypertriglyceridemia, this review focuses on the genetic variants in LPL, APOA5, APOC2, GPIHBP1 and LMF1 triglyceride-regulating genes reportedly associated with abnormal genetic transcription and the translation of proteins participating in triglyceride-rich lipoprotein metabolism. Hypertriglyceridemia resulting from such genetic abnormalities can be categorized as monogenic or polygenic. Monogenic hypertriglyceridemia, also known as familial chylomicronemia syndrome, is caused by homozygous or compound heterozygous pathogenic variants in the five canonical genes. Polygenic hypertriglyceridemia, also known as multifactorial chylomicronemia syndrome in extreme cases of hypertriglyceridemia, is caused by heterozygous pathogenic genetic variants with variable penetrance affecting the canonical genes, and a set of common non-pathogenic genetic variants (polymorphisms, using the former nomenclature) with well-established association with elevated triglyceride levels. We further address recent progress in triglyceride-lowering treatments. Understanding the genetic basis of hypertriglyceridemia opens new translational opportunities in the scope of genetic screening and the development of novel therapies.

Advances in Dyslipidaemia Treatments: Focusing on ApoC3 and ANGPTL3 Inhibitors.

Apolipoprotein C3 (apoC3) and angiopoietin-like protein 3 (ANGPTL3) inhibit lipolysis by lipoprotein lipase and may influence the secretion and uptake of various lipoproteins. Genetic studies show that depletion of these proteins is associated with improved lipid profiles and reduced cardiovascular events so it was anticipated that drugs which mimic the effects of loss-of-function mutations would be useful lipid treatments. ANGPTL3 inhibitors were initially developed as a treatment for severe hypertriglyceridaemia including familial chylomicronaemia syndrome (FCS), which is usually not adequately controlled with currently available drugs. However, it was found ANGPTL3 inhibitors were also effective in reducing low-density lipoprotein cholesterol (LDL-C) and they were studied in patients with homozygous familial hypercholesterolaemia (FH). Evinacumab targets ANGPTL3 and reduced LDL-C by about 50% in patients with homozygous FH and it has been approved for that indication. The antisense oligonucleotide (ASO) vupanorsen targeting ANGPTL3 was less effective in reducing LDL-C in patients with moderate hypertriglyceridaemia and its development has been discontinued but the small interfering RNA (siRNA) ARO-ANG3 is being investigated in Phase 2 studies. ApoC3 can be inhibited by the ASO volanesorsen, which reduced triglycerides by >70% in patients with FCS and it was approved for FCS in Europe but not in the United States because of concerns about thrombocytopaenia. Olezarsen is an N-acetylgalactosamine-conjugated ASO targeting apoC3 which appears as effective as volanesorsen without the risk of thrombocytopaenia and is undergoing Phase 3 trials. ARO-APOC3 is an siRNA targeting apoC3 that is currently being investigated in Phase 3 studies.

Hipertrigliceridemia grave em lactente: um caso de síndrome de quilomicronemia familiar

Familial chylomicronemia syndrome (FCS) is a rare, autosomal recessive monogenic disease, affecting 1:1,000,000000. A hallmark of the disease is the severe hypertriglyceridemia caused by either lipoprotein lipase (LPL) enzyme deficiency or one of its cofactors, compromising triglycerides (TG) metabolism. The index case is a 2 months old male infant with severe hypertriglyceridemia, level at presentation was extremely high 33280 mg/dL, hepatomegaly, steatosis and lipemia retinalis. Exchange transfusion blood was performed to reduce triglycerides to acceptable levels and to minimize the potential for acute pancreatitis and clinical signs related to hypertriglyceridemia. Sequencing of the LPL gene revealed a compound heterozygous pathogenic variants. This report highlights the importance of clinical suspicion for early diagnosis of severe hypertriglyceridemia, which is needed for prompt management and prevention of severe complications and risk of death.

Identification of a Compound Heterozygous LMF1 Variants in a Patient with Severe Hypertriglyceridemia - Case Report and Literature Review.

Familial chylomicronemia syndrome (FCS) and multifactorial chylomicronemia (MCM), characterized by highly variable triglyceride levels with acute episodes of severe hypertriglyceridemia (HTG), are caused by rare variants in genes associated with the catabolism of circulating lipoprotein triglycerides, mainly including LPL, APOC2, APOA5, GPIHBP1, and LMF1. Among them, the LMF1 gene only accounts for 1%. This study described a Chinese patient with severe HTG carrying compound heterozygous variants of a rare nonsense variant p.W168X in exon 3 and a missense variant p.R416Q in exon 9 in the LMF1 gene. These heterozygous variants account for his family's decreased lipase activity and mass, which caused the FCS phenotype.

Uloga varijanti lipoprotein lipaze u metaboličkim poremećajima i kardiovaskularnim oboljenjima

Lipoprotein lipase (LPL) is a glycoprotein that is produced and secreted into the interstitial space in various tissues, including the cardiac muscle, adipose tissue, macrophages, and skeletal muscle. LPL activity could be affected by genetic alterations which result in changes in lipid metabolism. This review article only focuses on reporting the recent studies which mainly explain the role of the LPL gene variants in metabolic syndrome and cardiovascular diseases. There are over 100 LPL gene variants, but this review article reported rs1801177, rs118204069, rs118204057, rs118204060, rs118204068, rs268, and rs328 as the most common in metabolic syndrome patients. In cardiovascular diseases, LPL variants rs1801177, rs268 and rs328 were the most prevalent. Therefore, it is suggested that further studies should be conducted to identify the LPL gene variants in other cardiovascular diseases, including cardiac arrhythmia. This review article concludes that LPL deficiency and dysfunction are associated with many diseases, such as obesity, insulin resistance, diabetes, chylomicronemia, atherosclerosis, myocardial infarction, coronary artery disease, and stroke.

Genetic variation in apolipoprotein A-V in hypertriglyceridemia.

While biallelic rare APOA5 pathogenic loss-of-function (LOF) variants cause familial chylomicronemia syndrome, heterozygosity for such variants is associated with highly variable triglyceride phenotypes ranging from normal to severe hypertriglyceridemia, often in the same individual at different time points. Here we provide an updated overview of rare APOA5 variants in hypertriglyceridemia. Currently, most variants in APOA5 that are considered to be pathogenic according to guidelines of the American College of Medical Genetics and Genomics are those resulting in premature termination codons. There are minimal high quality functional data on the impact of most rare APOA5 missense variants; many are considered as variants of unknown or uncertain significance. Furthermore, particular common polymorphisms of APOA5 , such as p.Ser19Trp and p.Gly185Cys in Caucasian and Asian populations, respectively, are statistically overrepresented in hypertriglyceridemia cohorts and are sometimes misattributed as being causal for chylomicronemia, when they are merely risk alleles for hypertriglyceridemia. Both biallelic and monoallelic LOF variants in APOA5 are associated with severe hypertriglyceridemia, although the biochemical phenotype in the monoallelic state is highly variable and is often exacerbated by secondary factors. Currently, with few exceptions, the principal definitive mechanism for APOA5 pathogenicity is through premature truncation. The pathogenic mechanisms of most missense variants in APOA5 remain unclear and require additional functional experiments or family studies.

Familial Chylomicronaemia Syndrome (FCS) Score Validation in United Kingdom FCS Registry: Can Additional Variables Improve the FCS Score Performance?

Familial Chylomicronaemia Syndrome (FCS) Score Validation in United Kingdom FCS Registry: Can Additional Variables Improve the FCS Score Performance?