Search

Background and aims Familial hypercholesterolemia (FH) is a monogenic disease characterized by high levels of low-density lipoprotein cholesterol and premature atherosclerotic cardiovascular disease. FH is caused by loss of function mutations in genes encoding LDL receptor (LDLR), and Apolipoprotein B (APOB) or gain of function (GOF) mutations in proprotein convertase subtilisin/kexin type 9 (PCSK9). In this study, we identified a novel variant in PCSK9, p.(Arg499His), located in the C-terminal domain, in two unrelated FH patients from Spain and Italy. Methods We studied familial segregation and determined variant activity in vitro. Results We determined PCSK9 expression, secretion and activity of the variant in transfected HEK293 cells; extracellular activity of the recombinant p.(Arg499His) PCSK9 variant in HEK 293 and HepG2 cells; PCSK9 affinity to the LDL receptor at neutral and acidic pH; the mechanism of action of the p.(Arg499His) PCSK9 variant by co-transfection with a soluble construct of the LDL receptor and by determining total PCSK9 intracellular accumulation when endosomal acidification is impaired and when an excess of soluble LDLr is present in the culture medium. Our results show high LDL-C concentrations and FH phenotype in p.(Arg499His) carriers. In vitro functional characterization shows that p.(Arg499His) PCSK9 variant causes a reduction in LDLr expression and LDL uptake. An intracellular activity for this variant is also shown when blocking the activity of secreted PCSK9 and by inhibiting endosomal acidification. Conclusions We demonstrated that p.(Arg499His) PCSK9 variant causes a direct intracellular degradation of LDLr therefore causing FH by reducing LDLr availability.

International audience

Background and aim: Protein convertase subtilisin kexin type 9 (PCSK-9) inhibitors demonstrated efficacy in cholesterol reduction and in the prevention of cardiovascular events. We evaluated changes in lipid profile and carotid stiffness in patients with familial hypercholesterolemia during 12 weeks of treatment with a PCSK-9 inhibitor, Evolocumab®. Methods and results: Patients with familial hypercholesterolemia starting a treatment with Evolocumab® were included. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), small dense LDL (assessed by LDL score) and carotid stiffness were evaluated before starting treatment with Evolocumab® and during 12 weeks of treatment. Twenty-five subjects were enrolled (52% males, mean age 51.5 years). TC and LDL-C were reduced of 38% and 52%, respectively during treatment, with LDL score reduced of 46.1%. In parallel, carotid stiffness changed from 8.8 (IQR: 7.0–10.4) m/sec to 6.6 (IQR: 5.4–7.5) m/sec, corresponding to a median change of 21.4% (p < 0.001), with a significant increase in carotid distensibility (from 12.1, IQR: 8.73–19.3 kPA−1 × 10−3 at T0 to 21.8, IQR: 16.6–31.8 kPA−1 × 10−3 at T12w) corresponding to a median change of 62.8% (p < 0.001). A multivariate analysis showed that changes in LDL score were independently associated with changes in carotid stiffness (β = 0.429, p = 0.041). Conclusion: Small dense LDL reduction, as assessed by LDL score, is associated with changes in carotid stiffness in patients with familial hypercholesterolemia treated with Evolocumab®.

Cerebrotendinous Xanthomatosis (CTX) is an autosomal recessive defect of the alternative pathway of bile acid biosynthesis, due to the deficiency of mitochondrial cytochrome P450 sterol 27-hydroxylase enzyme encoded by CYP27A1. The deficit of sterol 27-hydroxylase raises cholestanol in plasma and tissues of affected patients. Although there is a marked variability of signs, symptoms, severity and age of onset, the main clinical manifestations of CTX include chronic diarrhea, bilateral cataract, tendon xanthomas and neurological dysfunction. Herein, we report the clinical, biochemical and molecular characterization of a Caucasian female affected by CTX diagnosed at 28years. The patient’s clinical history revealed neurological and behavioral manifestations already at fifth year of life, following by bilateral cataract and chronic diarrhea without xanthomas. At diagnosis, an involvement of the cervical spinal cord was also observed on MRI. Sterols profile analysis in plasma and red blood cell membranes showed very high cholestanol levels. CYP27A1 sequencing revealed a new variant (e.g., c.850_854delinsCTC) at homozygous status. The follow-up after 5months of chenodeoxycholic acid treatment showed a decrease of plasma cholestanol of 64%. After 1 year, the patient showed normalization of bowel function, reduction of risk of falls, improvement of cognitive function although brain and spine MRI and other instrumental examinations remained unchanged. This case highlights the variability of the CTX phenotype that makes it difficult to reach an early diagnosis. Biochemical and/or molecular screening of CTX should be taken into account to early start the pharmacological treatment limiting neurological damages.

Galectin-3 (Gal-3) is a β-galactoside-binding protein belonging to the lectin family with pleiotropic regulatory activities and several physiological cellular functions, such as cellular growth, proliferation, apoptosis, differentiation, cellular adhesion, and tissue repair. Inflammation, tissue fibrosis and angiogenesis are the main processes in which Gal-3 is involved. It is implicated in the pathogenesis of several diseases, including organ fibrosis, chronic inflammation, cancer, atherosclerosis and other cardiovascular diseases (CVDs). This review aims to explore the connections of Gal-3 with cardiovascular diseases since they represent a major cause of morbidity and mortality. We herein discuss the evidence on the pro-inflammatory role of Gal-3 in the atherogenic process as well as the association with plaque features linked to lesion stability. We report the biological role and molecular mechanisms of Gal-3 in other CVDs, highlighting its involvement in the development of cardiac fibrosis and impaired myocardium remodelling, resulting in heart failure and atrial fibrillation. The role of Gal-3 as a prognostic marker of heart failure is described together with possible diagnostic applications to other CVDs. Finally, we report the tentative use of Gal-3 inhibition as a therapeutic approach to prevent cardiac inflammation and fibrosis.