Rare variants in PKHD1 associated with Caroli syndrome: Two case reports

Caroli disease (CD, OMIM #600643) is a rare autosomal recessive disorder characterized by polycystic segmental dilatation of the intrahepatic bile ducts and extreme variability in age of onset and clinical manifestations. When congenital hepatic fibrosis is associated with the polycystic dilatation of the biliary tract, the condition is referred as Caroli syndrome. The disease is thought to be caused by pathogenic variants in the PKHD1 gene (OMIM *606702)

Characterization of two novel pathogenic variants at compound heterozygous status in lipase maturation factor 1 gene causing severe hypertriglyceridemia

BACKGROUND: Severe hypertriglyceridemia is a rare disease characterized by triglyceride levels higher than 1000 mg/dL (11.3 mmol/L) and acute pancreatitis. The disease is caused by pathogenic variants in genes encoding lipoprotein lipase (LPL), apolipoprotein A5, apolipoprotein C2, glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1, and lipase maturation factor 1 (LMF1). OBJECTIVE: We aim to identify the genetic cause of severe hypertriglyceridemia and characterize the new variants in a patient with severe hypertriglyceridemia. METHODS: The proband was a male showing severe hypertriglyceridemia (triglycerides 1416 mg/dL, 16.0 mmol/L); proband's relatives were also screened. Genetic screening included direct sequencing of the above genes and identification of large rearrangements in the LPL gene. Functional characterization of mutant LMF1 variants was performed by complementing LPL maturation in transfected LMF1-deficient mouse fibroblasts. RESULTS: The proband and his affected brother were compound heterozygotes for variants in the LMF1 gene never identified as causative of severe hypertriglyceridemia c.[157delC;1351C>T];[410C>T], p.[(Arg53Glyfs*5)];[(Ser137Leu)]. Functional analysis demonstrated that the p.(Arg53Glyfs*5) truncation completely abolished and the p.(Ser137Leu) missense variant dramatically diminished the lipase maturation activity of LMF1. CONCLUSIONS: In addition to a novel truncating variant, we describe for the first time a missense variant functionally demonstrated affecting the lipase maturation function of LMF1. This is the first case in which compound heterozygous variants in LMF1 were functionally demonstrated as causative of severe hypertriglyceridemia

EXPRESSION OF ADIPONECTIN RECEPTORS IN HUMAN CAROTID ATHEROSCLEROTIC PLAQUES Abstracts from the 12th National Congress of the Italian Society of Cardiovascular Prevention (SIPREC), Naples, 6–8 March 2014

Introduction: Adiponectin is a protein secreted by the adipose tissue with pleiotropic effects on metabolism. This adipokine play different anti-atherogenic action, such as the improvement of endothelial function and anti-inflammatory status in arterial walls. Two receptors ubiquitously expressed, AdipoR1 and AdipoR2, are involved in its action which. In obesity a mechanism of adiponectin resistance was demonstrated. Aim: To verify if adiponectin-resistance occurs in human atherosclerotic plaques. Methods: RNA from 49 carotid atherosclerotic plaques (advanced lesions), their respective adjacent regions (witha low grade lesions) and 7 healthy arteries (iliac and mesenteric) was extracted, reverse-transcribed and used for real-time PCR by specific TaqMan assays (Applied Biosystems). In vitro experiments for gene regulation studies were performed on primary Human Aortic Endothelial Cells and Smooth Muscle Cells (Lonza) co-cultured with the macrophage cell line THP-1. Results: Expression levels of AdipoR1 were lower in advanced plaques as well as in their respective adjacent regions than in healthy arteries (p = 0.020 and p = 0.001 respectively). AdipoR2 levels gradually decreased from healthy arteries to plaque adjacent regions and to advanced plaques (all comparisons p\0.0001). In both cell types, expression of AdipoR1 was not affected by the co-culture with THP-1. The presence of THP-1 decreased AdipoR2 expression in Smooth Muscle Cells (p = 0.040), whereas a not statistically significant decrease was observed in Endothelial Cells. Conclusions: We demonstrated a decreased expression of adiponectin receptors in initial and advanced plaques, suggesting a mechanism of adiponectin-resistance during atherosclerotic process. A local adiponectin-resistance could be a main cause of the lack of atheroprotective effects mediated by adiponectin. Presence of macrophages could be a contributory cause of AdipoR2 decrease

The Intrinsic Cardiac Nervous System: From Pathophysiology to Therapeutic Implications

The cardiac autonomic nervous system (CANS) plays a pivotal role in cardiac homeostasis as well as in cardiac pathology. The first level of cardiac autonomic control, the intrinsic cardiac nervous system (ICNS), is located within the epicardial fat pads and is physically organized in ganglionated plexi (GPs). The ICNS system does not only contain parasympathetic cardiac efferent neurons, as long believed, but also afferent neurons and local circuit neurons. Thanks to its high degree of connectivity, combined with neuronal plasticity and memory capacity, the ICNS allows for a beat-to-beat control of all cardiac functions and responses as well as integration with extracardiac and higher centers for longer-term cardiovascular reflexes. The present review provides a detailed overview of the current knowledge of the bidirectional connection between the ICNS and the most studied cardiac pathologies/conditions (myocardial infarction, heart failure, arrhythmias and heart transplant) and the potential therapeutic implications. Indeed, GP modulation with efferent activity inhibition, differently achieved, has been studied for atrial fibrillation and functional bradyarrhythmias, while GP modulation with efferent activity stimulation has been evaluated for myocardial infarction, heart failure and ventricular arrhythmias. Electrical therapy has the unique potential to allow for both kinds of ICNS modulation while preserving the anatomical integrity of the system

Cerebrotendinous xanthomatosis, a metabolic disease with different neurological signs: two case reports

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive inborn error of bile acids synthesis and lipid accumulation caused by a deficiency of the mitochondrial cytochrome P450 sterol 27-hydroxylase enzyme encoded by CYP27A1. Pathogenic variants in CYP27A1 cause elevated cholestanol levels in the body, which leads to a variable clinical presentation that often includes cataracts, intellectual disability, neurological features, tendon xanthomas, and chronic diarrhea. Herein we describe the cases of two unrelated adult CTX patients. Case 1 is a patient with neurological dysfunction, including moderate intellectual disability, cataract of right eye, and xanthomas; Case 2 is a patient with tendon xanthomas without neurological symptoms. Plasma sterols profile obtained from both cases showed higher levels of cholestanol and cholesterol biosynthetic precursors compared to unaffected subjects. Case 1 and Case 2 were homozygous for the c.1263 + 5G > T (p.Leu396Profs29X) and c.1435C > G (p.Arg479Gly) pathogenic variants, respectively, in the CYP27A1 gene. Interestingly, for the first time, Case 2 variant has been identified in a homozygous state. Our results highlight that the sterol profile and genetic analyses are essential to make the diagnosis of CTX and to exclude other dyslipidemias

Identification and in vitro characterization of two new PCSK9 Gain of Function variants found in patients with Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by pathogenic variants in genes encoding for LDL receptor (LDLR), Apolipoprotein B and Proprotein convertase subtilisin/kexin type 9 (PCSK9). Among PCSK9 variants, only Gain-of- Function (GOF) variants lead to FH. Greater attention should be paid to the classification of variants as pathogenic. Two hundred sixty nine patients with a clinical suspect of FH were screened for variants in LDLR and the patients without pathogenic variants were screened for variants in PCSK9 and APOB. Functional characterization of PCSK9 variants was performed by assessment of protein secretion, of LDLR activity in presence of PCSK9 variant proteins as well as of the LDLR affinity of the PCSK9 variants. Among 81 patients without pathogenic variants in LDLR, 7 PCSK9 heterozygotes were found, 4 of whom were carriers of variants whose role in FH pathogenesis is still unknown. Functional characterization revealed that two variants (p.Ser636Arg and p.Arg357Cys) were GOF variants. In Conclusions, we demonstrated a GOF effect of 2 PCSK9 variants that can be considered as FH-causative variants. The study highlights the important role played by functional characterization in integrating diagnostic procedures when the pathogenicity of new variants has not been previously demonstrated

Correlation between low adenosine A2A receptor expression and hypercholesterolemia: A new component of the cardiovascular risk?

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Causative mutations and premature cardiovascular disease in patients with heterozygous familial hypercholesterolaemia

Background Familial Hypercholesterolemia (FH) is a common autosomal dominant disease, caused by mutations leading to elevated LDL cholesterol and, if untreated to premature cardiovascular disease (CVD). Methods Patients (young adults with family history of hypercholesterolemia or premature CVD) with an LDL cholesterol concentration > 4.9 mmol/L, after excluding Familial Combined Hyperlipidemia, were evaluated for causative mutations, MedPed and WHO score calculation and non-invasive ultrasound examination of carotid arteries. Results Among the 263 patients, 210 were heterozygotes for LDL receptor (LDLR) mutations, 4 had apo B gene mutations, 1 PCSK9 gene mutation, while 48 had no evidence of mutations. Among 194 unrelated index cases 149 heterozygotes had mutations (77 %). Among patients with LDLR mutations (n= 145), we found 9 compound heterozygotes, 75 patients with radical mutations and 65 with missense mutations. We performed follow-up and treatment ( statin + ezetimibe ) of 178 patients: a mean reduction of 49 % was achieved, with 21 % of patients reaching the LDL target of 2.6 mmol/L. In a multivariate analysis, carotid plaques, at ultrasound examination, were associated with the presence of mutation (p = 0.014), LDL cholesterol (p< 0.001), MedPed and WHO score (p< 0.001), independently of age, gender, smoking habits , blood pressure. LDL cholesterol (p< 0.003), MedPed and WHO score (p < 0.001) and Carotid plaque (p= 0.017). were independently associated with premature CVD. Conclusions We identified patients with causative mutations in 82 % of cases under study. In addition to LDL Cholesterol and MEDPed and WHO score, carotid plaques at ultrasound evaluation provides direct evidence of premature vascular disease and high risk for cardiovascular events

Lipid profile and genetic status in a familial hypercholesterolemia pediatric population: exploring the LDL/HDL ratio

Background Familial hypercholesterolemia (FH) is a genetic disorder caused by mutations in genes involved in low-density lipoprotein (LDL) uptake (LDLR, APOB and PCSK9). Genetic diagnosis is particularly useful in asymptomatic children allowing for the detection of definite FH patients. Furthermore, defining their genetic status may be of considerable importance as the compound heterozygous status is much more severe than the heterozygous one. Our study aims at depicting the genetic background of an Italian pediatric population with FH focusing on the correlation between lipid profile and genetic status. Methods Out of 196 patients with clinically suspected FH (LDL-cholesterol [LDL-C] levels above 3.37 mmol/L, cholesterol level above 6.46 mmol/L in a first-degree relative or the presence of premature cardiovascular acute disease in a first/second-degree relative), we screened 164 index cases for mutations in the LDLR, APOB and PCSK9 genes. Results Patients with mutations (129/164) showed increased levels of LDL-C, 95th percentile-adjusted LDL-C and LDL/high-density lipoprotein (HDL) ratio and decreased levels of HDL-C, adjusted HDL-C. The association of the LDL/HDL ratio with the presence of mutations was assessed independently of age, (body mass index) BMI, parental hypercholesterolemia, premature coronary artery disease (CAD), triglycerides by multivariate logistic regression (odds ratio [OR]=1.701 [1.103-2.621], p=0.016). The LDL/HDL ratio gradually increased from patients without mutations to patients with missense mutations, null mutations and compound heterozygotes. Conclusions In conclusion, the LDL/HDL ratio proved to be a better parameter than LDL-C for discriminating patients with from patients without mutations across different genetic statuses

A Real-World Experience of Clinical, Biochemical and Genetic Assessment of Patients with Homozygous Familial Hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH), the severest form of familial hypercholesterolemia (FH), is characterized by very high LDL-cholesterol levels and a high frequency of coronary heart disease. The disease is caused by the presence of either a pathogenic variant at homozygous status or of two pathogenic variants at compound heterozygous status in the LDLR, APOB, PCSK9 genes. We retrospectively analyzed data of 23 HoFH patients (four children and 19 adults) identified during the genetic screening of 724 FH patients. Genetic screening was performed by sequencing FH causative genes and identifying large rearrangements of LDLR. Among the HoFH patients, four out of 23 (17.4%) were true homozygotes, whereas 19 out of 23 (82.6%) were compound heterozygotes for variants in the LDLR gene. Basal LDL-cholesterol was 12.9 ± 2.9 mmol/L. LDL-cholesterol levels decreased to 7.2 ± 1.8 mmol/L when treated with statin/ezetimibe and to 5.1 ± 3.1 mmol/L with anti-PCSK9 antibodies. Homozygous patients showed higher basal LDL-cholesterol and a poorer response to therapy compared with compound heterozygotes. Since 19 unrelated patients were identified in the Campania region (6,000,000 inhabitants) in southern Italy, the regional prevalence of HoFH was estimated to be at least 1:320,000. In conclusion, our results revealed a worse phenotype for homozygotes compared with compound heterozygotes, thereby highlighting the role of genetic screening in differentiating one genetic status from the other