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Background: apo (apolipoprotein) E has crucial role in lipid metabolism. The genetic variation in APOE gene is associated with monogenic disorders and contributes to polygenic hypercholesterolemia and to interindividual variability in cholesterol. APOE rare variants may be involved in the phenotype of genetic hyperlipidemias. Methods: Exon 4 of APOE were sequenced in all consecutive unrelated subjects with primary hyperlipidemia from a Lipid Unit (n=3667) and 822 random subjects from the Aragon Workers Health Study. Binding affinity of VLDL (very low-density lipoprotein) to LDL receptor of pathogenic predicted apoE variants was analyzed in vitro. Lipoprotein particle number, size, and composition were studied by nuclear magnetic resonance. Results: In addition to common polymorphisms giving rise to APOE2 and APOE4, 14 gene variants were found in exon 4 of APOE in 65 subjects. p.(Leu167del) in 8 patients with isolated hypercholesterolemia and in 8 patients with combined hyperlipidemia. Subjects with p.(Arg121Trp), p.(Gly145Asp), p.(Arg154Ser), p.(Arg163Cys), p.(Arg165Trp), and p.(Arg168His) variants met dysbetalipoproteinemia lipid criteria and were confirmed by nuclear magnetic resonance. VLDL affinity for the LDL receptor of p.(Arg163Cys) and p.(Arg165Trp) heterozygous carriers had intermedium affinity between APOE2/2 and APOE3/3. p.(Gly145Asp) and p.(Pro220Leu) variants had higher affinity than APOE3/3. Conclusions: APOE genetic variation contributes to the development of combined hyperlipidemia, usually dysbetalipoproteinemia, and familial hypercholesterolemia. The lipid phenotype in heterozygous for dysbetalipoproteinemia-associated mutations is milder than the homozygous APOE2/2-associated phenotype. Subjects with dysbetalipoproteinemia and absence of APOE2/2 are good candidates for the study of pathogenic variants in APOE . However, more investigation is required to elucidate the significance of rarer variants of apoE.

This Special Issue, “Cardiovascular Disease, Atherosclerosis and Familial Hypercholesterolemia: From Molecular Mechanisms Causing Pathogenicity to New Therapeutic Approaches”, contributes to advancing our knowledge of the molecular mechanisms that drive cardiovascular disease, atherosclerosis and familial hypercholesterolemia and the development of state-of-the-art research in the field. This Special Issues is the result of a call for papers that was sent out in late 2020 and continued till mid-2022, from which twelve papers (six original research articles, one hypothesis and five reviews) were published.

Familial hypercholesterolaemia (FH) is an autosomal dominant dyslipidaemia, characterised by elevated LDL cholesterol (LDL-C) levels in the blood. Three main genes are involved in FH diagnosis: LDL receptor (LDLr), Apolipoprotein B (APOB) and Protein convertase subtilisin/kexin type 9 (PCSK9) with genetic mutations that led to reduced plasma LDL-C clearance. To date, several PCSK9 gain-of-function (GOF) variants causing FH have been described based on their increased ability to degrade LDLr. On the other hand, mutations that reduce the activity of PCSK9 on LDLr degradation have been described as loss-of-function (LOF) variants. It is therefore important to functionally characterise PCSK9 variants in order to support the genetic diagnosis of FH. The aim of this work is to functionally characterise the p.(Arg160Gln) PCSK9 variant found in a subject suspected to have FH. Different techniques have been combined to determine efficiency of the autocatalytic cleavage, protein expression, effect of the variant on LDLr activity and affinity of the PCSK9 variant for the LDLr. Expression and processing of the p.(Arg160Gln) variant had a result similar to that of WT PCSK9. The effect of p.(Arg160Gln) PCSK9 on LDLr activity is lower than WT PCSK9, with higher values of LDL internalisation (13%) and p.(Arg160Gln) PCSK9 affinity for the LDLr is lower than WT, EC50 8.6 ± 0.8 and 25.9 ± 0.7, respectively. The p.(Arg160Gln) PCSK9 variant is a LOF PCSK9 whose loss of activity is caused by a displacement of the PCSK9 P’ helix, which reduces the stability of the LDLr-PCSK9 complex. This research was funded by Grupos Consolidados Gobierno Vasco 2021, grant number IT1720-22. A.L.-S. was supported by a grant PIF (2019–2020), Gobierno Vasco and partially supported by Fundación Biofísica Bizkaia. S.J-B. was supported by a Margarita Salas Grant 2022 from the University of the Basque Country.

Visual Abstract, Highlights • A machine-learning model has been developed to improve accuracy on predicting the activity of missense LDLr mutations. • ClinVar was used as database, and the model function was defined by using specific characteristics of the LDLr. • A high-score prediction ML model with specificity of 92.5% and sensitivity of 91.6% has been developed to predict pathogenicity of LDLr variants. • Implementation of high-predicting capacity software constitutes a valuable approach for assessing pathogenicity of LDLr variants to help in the early diagnosis and management of FH disease. • An open-access predictive software (MLb-LDLr) is provided to the scientific community., Summary Untreated familial hypercholesterolemia (FH) leads to atherosclerosis and early cardiovascular disease. Mutations in the low-density lipoprotein receptor (LDLr) gene constitute the major cause of FH, and the high number of mutations already described in the LDLr makes necessary cascade screening or in vitro functional characterization to provide a definitive diagnosis. Implementation of high-predicting capacity software constitutes a valuable approach for assessing pathogenicity of LDLr variants to help in the early diagnosis and management of FH disease. This work provides a reliable machine learning model to accurately predict the pathogenicity of LDLr missense variants with specificity of 92.5% and sensitivity of 91.6%.

Pain causes disability and suffering to those who suffer from it and has been considered a public health problem since 1982 by the World Health Organization (WHO). In children with Infantile Cerebral Palsy (ICP) it is a challenge to identify and assess pain. In recent years the number of tools to assess pain in children has increased considerably. However, to date, there are no standardized measures for a comprehensive assessment of pain in children with cerebral palsy. General objective: To review the scales used to assess pain in children aged 6 to 12 years with Infantile Cerebral Palsy. Methodology: To obtain the articles to meet the objective of this literature review, different databases such as PUBMED, COCHRANE, SCOPUS, SCIELO, DIALNET and BIBLIOTECA UNIR were consulted. In addition to searching the databases, for Clinical Practice Guidelines, RNAO, NICE, and GUÍA SALUD were searched. Finally, to ensure a comprehensive search, a hand search was carried out on the SCIENCE DIRECT platform. As for the selection of articles, articles published from 2017 onwards were considered. As for the language of the selected articles, articles published in Spanish and English were considered. Results: To meet the objective, 20 articles were selected for the study. Of these, 7 were cross-sectional studies, 1 case-control study, 3 retrospective cohort studies, 2 prospective cohort studies, 1 prospective observational study, 1 clinical trial, 2 literature searches, 2 systematic reviews and 1 Clinical Practice Guideline. Conclusions: According to these investigations, although in terms of statistical data, the FLACC-r scale obtained the most statistically significant results, in terms of the previously selected criteria, both the FLACC-r scale and the PPP scale would be the only scales that meet all the criteria, adapting in the best way to the needs of assessing pain in children with infantile cerebral palsy. Introducción: El dolor es causante de discapacidades y sufrimiento a quien lo padece, siendo considerado problema de salud pública desde el año 1982 por la Organización Mundial de la Salud (OMS). En niños con Parálisis Cerebral Infantil (PCI) es un reto identificar y evaluar el dolor. En los últimos años el número de herramientas para evaluar el dolor en niños ha aumentado considerablemente. Sin embargo, a día de hoy, no hay medidas estandarizadas para realizar una valoración exhaustiva del dolor en niños con parálisis cerebral. Objetivo general: Revisar las escalas utilizadas para valorar el dolor en niños de 6 a 12 años con Parálisis Cerebral Infantil. Metodología: Para conseguir los artículos para responder el objetivo de esta revisión bibliográfica de la literatura se consultaron diferentes bases de datos como PUBMED, COCHRANE, SCOPUS, SCIELO, DIALNET y BIBLIOTECA UNIR. Además de buscar en las bases de datos, en cuanto a las Guías de Práctica Clínica, se buscó en RNAO, NICE, y GUÍA SALUD. Para terminar, para asegurar una búsqueda amplia, se realizó una búsqueda a mano en la plataforma SCIENCE DIRECT. En cuanto a la selección de los artículos, se tuvieron en cuenta los artículos publicados a partir del año 2017. En cuanto al idioma de los artículos seleccionados, se tuvieron en cuenta los artículos publicados en castellano e inglés. Resultados: Para responder al objetivo se seleccionaron 20 artículos para realizar el trabajo. 7 de ellos fueron estudios trasversales, 1 estudio caso control, 3 estudios cohortes retrospectivos, 2 estudios cohortes prospectivos, 1 estudio prospectivo observacional, 1 ensayo clínico, 2 búsquedas bibliográficas, 2 revisiones sistemáticas y 1 Guía de Práctica Clínica. Conclusiones: Según estas investigaciones, aunque en cuanto a los datos estadísticos, la escala FLACC-r obtuvieran los resultados estadísticamente más significativos, en cuanto a los criterios previamente seleccionados, tanto la escala FLACC-r como la escala PPP serían las únicas escalas que cumple todos los criterios, adaptándose de la mejor forma a las necesidades de valorar el dolor en niños con parálisis cerebral infantil.

[Background] PCSK9 (Proprotein convertase subtilisin/kexin type 9) regulates LDL-C (low-density lipoprotein cholesterol) metabolism by targeting LDLr (LDL receptor) for lysosomal degradation. PCSK9 gain-of-function variants cause autosomal dominant hypercholesterolemia by reducing LDLr levels, the D374Y variant being the most severe, while loss-of-function variants are associated with low LDL-C levels. Gain-of-function and loss-of-function activities have also been attributed to variants occurring in the PCSK9 signal peptide. Among them, L11 is a very rare PCSK9 variant that seems to increase LDL-C values in a moderate way causing mild hypercholesterolemia., [Methods] Using molecular biology and biophysics methodologies, activities of L8 and L11 variants, both located in the leucine repetition stretch of the signal peptide, have been extensively characterized in vitro., [Results] L8 variant is not associated with increased LDLr activity, whereas L11 activity is increased by ≈20% compared with wt PCSK9. The results suggest that the L11 variant reduces LDLr levels intracellularly by a process resulting from impaired cleavage of the signal peptide. This would lead to less efficient LDLr transport to the cell membrane and promote LDLr intracellular degradation., [Conclusions] Deletion of a leucine in the signal peptide in L8 variant does not affect PCSK9 activity, whereas the leucine duplication in the L11 variant enhances LDLr intracellular degradation. These findings highlight the importance of deep in vitro characterization of PCSK9 genetic variants to determine pathogenicity and improve clinical diagnosis and therapy of inherited familial hypercholesterolemia disease., This work was supported by the Basque Government (Grupos Consolidados IT-1264-19) and Instituto de Salud Carlos III: CIBERCV and FIS PI19/0069. U. Galicia-Garcia was supported by Fundación Biofísica Bizkaia. A. Benito-Vicente was supported by Programa de especialización de Personal Investigador Doctor en la UPV/EHU (2019) 2019-2020. S. Jebari-Benslaiman and A. Larrea-Sebal were supported by a grant PIF (2017–2018) and (2019-2020), Gobierno Vasco, respectively. A.L-S was partially supported by Fundación Biofísica Bizkaia.

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.

Atherosclerosis is the main risk factor for cardiovascular disease (CVD), which is the leading cause of mortality worldwide. Atherosclerosis is initiated by endothelium activation and, followed by a cascade of events (accumulation of lipids, fibrous elements, and calcification), triggers the vessel narrowing and activation of inflammatory pathways. The resultant atheroma plaque, along with these processes, results in cardiovascular complications. This review focuses on the different stages of atherosclerosis development, ranging from endothelial dysfunction to plaque rupture. In addition, the post-transcriptional regulation and modulation of atheroma plaque by microRNAs and lncRNAs, the role of microbiota, and the importance of sex as a crucial risk factor in atherosclerosis are covered here in order to provide a global view of the disease., This work was supported by the Basque Government (Grupos Consolidados IT-1264-19). A.B.-V. was supported by Programa de especialización de Personal Investigador Doctor en la UPV/EHU (2019) 2019/2020; U.G-G. was supported by Margarita Salas Grant; and S.J. and A.L-S were supported by a grant PIF (2017–2018) and PIF (2019–2020) Gobierno Vasco, respectively.

Untreated familial hypercholesterolemia (FH) leads to atherosclerosis and early cardiovascular disease. Mutations in the low-density lipoprotein receptor (LDLr) gene constitute the major cause of FH, and the high number of mutations already described in the LDLr makes necessary cascade screening or in vitro functional characterization to provide a definitive diagnosis. Implementation of high-predicting capacity software constitutes a valuable approach for assessing pathogenicity of LDLr variants to help in the early diagnosis and management of FH disease. This work provides a reliable machine learning model to accurately predict the pathogenicity of LDLr missense variants with specificity of 92.5% and sensitivity of 91.6%., This study was supported by grants from the Basque Government (Cesar Martin, Grupos Consolidados IT-1264-19). Mr Larrea-Sebal was supported by a FPI grant from Gobierno Vasco (2019–2020). Dr Benito-Vicente was supported by Programa de especialización de Personal Investigador Doctor en la UPV/EHU (2019) 2019-2020. Dr Galicia-Garcia was supported by Fundación Biofísica Bizkaia. Ms Jebari-Benslaiman was supported by grant PIF (2017–2018), Gobierno Vasco.

[Background and aims] Lipoprotein(a) [Lp(a)] concentration in heterozygous familial hypercholesterolemia (heFH) is not well established. Whether the genetic defect responsible for heFH plays a role in Lp(a) concentration is unknown. We aimed to compare Lp(a) in controls from a healthy population, in genetically diagnosed heFH and mutation-negative hypercholesterolemia subjects, and to assess the influence on Lp(a) of the genetic defect responsible for heFH., [Methods] We conducted a cross-sectional study, performed in a lipid clinic in Spain. We studied adults with suspected heFH and a genetic study of FH genes (LDLR, APOB, APOE and PCSK9) and controls from de Aragon Workers’ Health Study. HeFH patients from the Dyslipidemia Registry of the Spanish Atherosclerosis Society (SEA) were used as validation cohort., [Results] Adjusted geometric means (95% confidence interval) of Lp(a) in controls (n = 1059), heFH (n = 500), and mutation-negative subjects (n = 860) were 14.9 mg/dL (13.6, 16.4), 21.9 mg/dL (18.1, 25.6) and 37.4 mg/dL (33.3, 42.1), p < 0.001 in all comparisons. Among heFH subjects, APOB-dependent FH showed the highest Lp(a), 36.5 mg/dL (22.0, 60.8), followed by LDLR-dependent FH, 21.7 mg/dL (17.9, 26.4). These differences were also observed in heFH from the SEA cohort. The number of plasminogen-like kringle IV type−2 repeats of LPA, the hypercholesterolemia polygenic score or LDLc concentration did not explain these differences. In LDLR-dependent FH, Lp(a) levels were not different depending on the affected protein domain., [Conclusions] Lp(a) is elevated in mutation-negative subjects and in heFH. The concentration of Lp(a) in heFH varies in relation to the responsible gene. Higher Lp(a) in heFH is not explained by their higher LDLc., This study was supported by grants from the Spanish Ministry of Economy and Competitiveness PI 18/01777, PI 19/00694 and CIBERCV; and Gobierno de Aragón B-14. These projects are co-financed by Instituto de Salud Carlos III and the European Regional Development Fund (ERDF) of the European Union ‘‘A way to make Europe”.

Type 2 diabetes (T2D), a heterogeneous disorder derived from metabolic dysfunctions, leads to a glucose overflow in the circulation due to both defective insulin secretion and peripheral insulin resistance. One of the critical risk factor for T2D is obesity, which represents a global epidemic that has nearly tripled since 1975. Obesity is characterized by chronically elevated free fatty acid (FFA) levels, which cause deleterious effects on glucose homeostasis referred to as lipotoxicity. Here, we review the physiological FFA roles onto glucose-stimulated insulin secretion (GSIS) and the pathological ones affecting many steps of the mechanisms and modulation of GSIS. We also describe in vitro and in vivo experimental evidences addressing lipotoxicity in β-cells and the role of saturation and chain length of FFA on the potency of GSIS stimulation. The molecular mechanisms underpinning lipotoxic-β-cell dysfunction are also reviewed. Among them, endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, inflammation, impaired autophagy and β-cell dedifferentiation. Finally therapeutic strategies for the β-cells dysfunctions such as the use of metformin, glucagon-like peptide 1, thiazolidinediones, anti-inflammatory drugs, chemical chaperones and weight are discussed.