Performance comparison of different classification algorithms applied to the diagnosis of familial hypercholesterolemia in paediatric subjects.

Familial Hypercholesterolemia (FH) is an inherited disorder of lipid metabolism, characterized by increased low density lipoprotein cholesterol (LDLc) levels. The main purpose of the current work was to explore alternative classification methods to traditional clinical criteria for FH diagnosis, based on several biochemical and biological indicators. Logistic regression (LR), decision tree (DT), random forest (RF) and naive Bayes (NB) algorithms were developed for this purpose, and thresholds were optimized by maximization of Youden index (YI). All models presented similar accuracy (Acc), specificity (Spec) and positive predictive values (PPV). Sensitivity (Sens) and G-mean values were significantly higher in LR and RF models, compared to the DT. When compared to Simon Broome (SB) biochemical criteria for FH diagnosis, all models presented significantly higher Acc, Spec and G-mean values (p < 0.01), and lower negative predictive value (NPV, p < 0.05). Moreover, LR and RF models presented comparable Sens values. Adjustment of the cut-off point by maximizing YI significantly increased Sens values, with no significant loss in Acc. The obtained results suggest such classification algorithms can be a viable alternative to be used as a widespread screening method. An online application has been developed to assess the performance of the LR model in a wider population.

Hepatic Sensing Loop Regulates PCSK9 Secretion in Response to Inhibitory Antibodies.

BACKGROUND: Monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9i) lower LDL-C by up to 60% and increase plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels by 10-fold. OBJECTIVES: The authors studied the reasons behind the robust increase in plasma PCSK9 levels by testing the hypothesis that mechanisms beyond clearance via the low-density lipoprotein receptor (LDLR) contribute to the regulation of cholesterol homeostasis. METHODS: In clinical cohorts, animal models, and cell-based studies, we measured kinetic changes in PCSK9 production and clearance in response to PCSK9i. RESULTS: In a patient cohort receiving PCSK9i therapy, plasma PCSK9 levels rose 11-fold during the first 3 months and then plateaued for 15 months. In a cohort of healthy volunteers, a single injection of PCSK9i increased plasma PCSK9 levels within 12 hours; the rise continued for 9 days until it plateaued at 10-fold above baseline. We recapitulated the rapid rise in PCSK9 levels in a mouse model, but only in the presence of LDLR. In vivo turnover and in vitro pulse-chase studies identified 2 mechanisms contributing to the rapid increase in plasma PCSK9 levels in response to PCSK9i: 1) the expected delayed clearance of the antibody-bound PCSK9; and 2) the unexpected post-translational increase in PCSK9 secretion. CONCLUSIONS: PCSK9 re-entry to the liver via LDLR triggers a sensing loop regulating PCSK9 secretion. PCSK9i therapy enhances the secretion of PCSK9, an effect that contributes to the increased plasma PCSK9 levels in treated subjects.

Concentration of LDLR, degree of hepatic fibrosis and hepatic steatosis in patients with chronic hepatitis B infection treated with tenofovir disoproxil fumarate.

INTRODUCTION: Epidemiological data indicate that one-third of the world's population have serological markers of hepatitis B virus infection. Hepatic steatosis is often observed in patients with chronic liver diseases. The exact mechanisms of hepatic steatosis progression and the efficacy of antiviral therapy in patients with CHB and hepatic steatosis are not yet fully understood. OBJECTIVE: The aim of the study was to investigate the LDLR concentration and degree of hepatic fibrosis and hepatic steatosis in patients with chronic hepatitis B infection during tenofovir disoproxil fumarate therapy. MATERIAL AND METHODS: The study group consisted of 54 patients with CHB. The LDLR concentration, assessment of the degree of hepatic fibrosis, hepatic steatosis, total cholesterol, low density lipoprotein, high density lipoprotein and triglyceride concentrations, were assessed at the beginning of therapy, 6 months later, and 12 months after commencement of therapy. The control group consisted of 18 healthy individuals. RESULTS: The mean LDLR concentration in the studied groups was statistically significantly lower (p<0.05) than in the controls. The antiviral therapy based on TDF had no influence on the LDLR concentration and HBsAg level. CONCLUSIONS: The results indicate a statistically significant lower(p<0.05) concentration of LDLR in patients with chronic hepatitis B infection. Negative correlations between HBsAg level and LDLR concentration in patients with chronic HBV, at all stages of the study may indicate, that HBsAg protects hepatocytes from LDL accumulation.

Rutin and Quercetin Decrease Cholesterol in HepG2 Cells but Not Plasma Cholesterol in Hamsters by Oral Administration.

Rutin (R) and quercetin (Q) are two widespread dietary flavonoids. Previous studies regarding the plasma cholesterol-lowering activity of R and Q generated inconsistent results. The present study was therefore carried out to investigate the effects of R and Q on cholesterol metabolism in both HepG2 cells and hypercholesterolemia hamsters. Results from HepG2 cell experiments demonstrate that both R and Q decreased cholesterol at doses of 5 and 10 µM. R and Q up-regulated both the mRNA and protein expression of sterol regulatory element binding protein 2 (SREBP2), low-density lipoprotein receptor (LDLR), and liver X receptor alpha (LXRα). The immunofluorescence study revealed that R and Q increased the LDLR expression, while only Q improved LDL-C uptake in HepG2 cells. Results from hypercholesterolemia hamsters fed diets containing R (5.5 g/kg diet) and Q (2.5 g/kg diet) for 8 weeks demonstrate that both R and Q had no effect on plasma total cholesterol. In the liver, only Q reduced cholesterol significantly. The discrepancy between the in vitro and in vivo studies was probably due to a poor bioavailability of flavonoids in the intestine. It was therefore concluded that R and Q were effective in reducing cholesterol in HepG2 cells in vitro, whereas in vivo, the oral administration of the two flavonoids had little effect on plasma cholesterol in hamsters.

Divergent low-density lipoprotein receptor (LDLR) linked to low VSV G-dependent viral infectivity and unique serum lipid profile in zebra finches.

The low-density lipoprotein receptor (LDLR) is key to cellular cholesterol uptake and is also the main receptor for the vesicular stomatitis virus glycoprotein (VSV G). Here we show that in songbirds LDLR is highly divergent and lacks domains critical for ligand binding and cellular trafficking, inconsistent with universal structure conservation and function across vertebrates. Linked to the LDLR functional domain loss, zebra finches show inefficient infectivity by lentiviruses (LVs) pseudotyped with VSV G, which can be rescued by the expression of human LDLR. Finches also show an atypical plasma lipid distribution that relies largely on high-density lipoprotein (HDL). These findings provide insights into the genetics and evolution of viral infectivity and cholesterol transport mechanisms in vertebrates.

Associations of serially measured PCSK9, LDLR and MPO with clinical outcomes in heart failure.

Aim: To investigate the temporal evolution of plasma proprotein convertase subtilisin/kexin type 9 (PCSK9), low-density lipoprotein receptor (LDLR) and myeloperoxidase (MPO) in relation to clinical outcome in chronic heart failure (CHF). Methodology & results: Trimonthly blood sampling was performed during a median follow-up of 2.2 (IQR 1.4-2.5) years in 263 CHF patients. Seventy patients reached the primary end point (PE) (cardiovascular death, heart transplantation, left ventricular assist device implantation or HF-hospitalization). MPO level was independently associated with the PE; the adjusted (for clinical factors) hazard ratio (aHR) per standard deviation difference in MPO was 1.71 (95% CI: 1.23-2.43) at any time during follow-up. PCSK9 level (HR: 1.45 [1.04-2.06]) and LDLR (HR: 0.66 [0.49-0.87]) were statistical significantly associated with the PE but only in unadjusted analyses. Slope of temporal MPO evolution (aHR: 1.34 [1.12-1.76] per 0.1 standard deviation/year difference in slope) and LDLR (aHR: 0.78 [0.61-0.90]) however, were associated with PE. Conclusion: Temporal patterns of MPO and LDLR are independently associated with clinical outcome in CHF, which illustrates the importance of assessing temporal evolutions. Clinical trial registration information: registered in ClinicalTrials.gov, number NCT01851538. https://clinicaltrials.gov/ct2/show/NCT01851538.

The enigma of soluble LDLR: could inflammation be the key?

Soluble low-density lipoprotein receptor (sLDLR) is the circulating ectodomain of transmembrane LDLR. Its blood level strongly correlates with that of triglycerides (TG). This correlation has eluded satisfactory explanation. Hypertriglyceridemia and shedding of the ectodomain of many transmembrane receptors often accompany inflammatory states. The shedding mostly occurs through cleavage by a disintegrin-and-metalloproteinase-17 (ADAM-17), an enzyme activated by inflammation. It reduces the cellular uptake of TG-loaded lipoproteins, causing their accumulation in circulation; hence the correlation between plasma sLDLR and TG. Soluble LDLR could become a new surrogate marker of inflammation.

Pharmacological aspects of ANGPTL3 and ANGPTL4 inhibitors: New therapeutic approaches for the treatment of atherogenic dyslipidemia.

Among the determinants of atherosclerotic cardiovascular disease (ASCVD), genetic and experimental evidence has provided data on a major role of angiopoietin-like proteins 3 and 4 (ANGPTL3 and ANGPTL4) in regulating the activity of lipoprotein lipase (LPL), antagonizing the hydrolysis of triglycerides (TG). Indeed, beyond low-density lipoprotein cholesterol (LDL-C), ASCVD risk is also dependent on a cluster of metabolic abnormalities characterized by elevated fasting and post-prandial levels of TG-rich lipoproteins and their remnants. In a head-to-head comparison between murine models for ANGPTL3 and ANGPTL4, the former was found to be a better pharmacological target for the treatment of hypertriglyceridemia. In humans, loss-of-function mutations of ANGPTL3 are associated with a marked reduction of plasma levels of VLDL, low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Carriers of loss-of-function mutations of ANGPTL4 show instead lower TG-rich lipoproteins and a modest but significant increase of HDL. The relevance of ANGPTL3 and ANGPTL4 as new therapeutic targets is proven by the development of monoclonal antibodies or antisense oligonucleotides. Studies in animal models, including non-human primates, have demonstrated that short-term treatment with monoclonal antibodies against ANGPTL3 and ANGPTL4 induces activation of LPL and a marked reduction of plasma TG-rich-lipoproteins, apparently without any major side effects. Inhibition of both targets also partially reduces LDL-C, independent of the LDL receptor. Similar evidence has been observed with the antisense oligonucleotide ANGPTL3-LRX. The genetic studies have paved the way for the development of new ANGPTL3 and 4 antagonists for the treatment of atherogenic dyslipidemias. Conclusive data of phase 2 and 3 clinical trials are still needed in order to define their safety and efficacy profile.

Heterozygosity in LDLR rs2228671 and rs72658855 Gene is Associated with Increased Risk of Developing Coronary Artery Disease in India -A Case-Control Study.

OBJECTIVE: Coronary artery disease (CAD) is one of the most common causes of death worldwide. Risk factors of CAD include high LDL-C, low high-density lipoprotein (HDL), hypertension, lack of exercise, genetic factors, etc. Polymorphisms of the LDLR gene have been associated with CAD in previous studies. METHODS: The LDLR-rs72658855 C>T genotyping was detected by using allele-specific PCR (ASPCR). The association of rs2228671 and rs72658855 with CAD in a south Indian cohort (200 CAD patients and 200 matched healthy controls was studied. RESULTS: Our findings showed that rs2228671 gene variability is associated with increased susceptibility to coronary artery disease in the codominant inheritance model for variant CC vs. CT OR 3.42(1.09-10.7), with P<0.034. A non-significant association was reported in the recessive inheritance model for the variant (CC+CT) vs. TT OR 0.56(0.16-1.95), at P<0.36. and in the dominant inheritance model for variant CC vs. (CT+TT) OR 2.8(1.07-7.34), at P<0.032 .In case of allelic comparison, it was indicated that the LDLR rs2228671-T allele was associated with an increased risk of developing CAD compared to C allele OR=2.4, with 95% CI (1.05-5.64) and P< 0.036 . Our findings showed that LDLR rs72658855 C>T gene variability was associated with an increased susceptibility to coronary artery disease in the codominant inheritance model for variant CC vs. CT OR 1.7(1.1-2.6), at P<0.015 and in the dominant inheritance model for variant CC vs. (CT+TT) OR 1.66(1.07-2.58), at P<0.0.02.. In case of allelic comparison, a non-significant association was reported in LDLR rs72658855-T and C allele. CONCLUSION: We concluded that the heterozygosity in LDLR-rs72658855 and rs2228671 and T allele in LDLR rs2228671 are strongly associated with increased susceptibility to coronary artery disease. These results must be validated by future well-designed studies with larger sample sizes and different populations.

Cyclase-associated protein 1 is a binding partner of proprotein convertase subtilisin/kexin type-9 and is required for the degradation of low-density lipoprotein receptors by proprotein convertase subtilisin/kexin type-9.

AIMS: Proprotein convertase subtilisin/kexin type-9 (PCSK9), a molecular determinant of low-density lipoprotein (LDL) receptor (LDLR) fate, has emerged as a promising therapeutic target for atherosclerotic cardiovascular diseases. However, the precise mechanism by which PCSK9 regulates the internalization and lysosomal degradation of LDLR is unknown. Recently, we identified adenylyl cyclase-associated protein 1 (CAP1) as a receptor for human resistin whose globular C-terminus is structurally similar to the C-terminal cysteine-rich domain (CRD) of PCSK9. Herein, we investigated the role of CAP1 in PCSK9-mediated lysosomal degradation of LDLR and plasma LDL cholesterol (LDL-C) levels. METHODS AND RESULTS: The direct binding between PCSK9 and CAP1 was confirmed by immunoprecipitation assay, far-western blot, biomolecular fluorescence complementation, and surface plasmon resonance assay. Fine mapping revealed that the CRD of PCSK9 binds with the Src homology 3 binding domain (SH3BD) of CAP1. Two loss-of-function polymorphisms found in human PCSK9 (S668R and G670E in CRD) were attributed to a defective interaction with CAP1. siRNA against CAP1 reduced the PCSK9-mediated degradation of LDLR in vitro. We generated CAP1 knock-out mice and found that the viable heterozygous CAP1 knock-out mice had higher protein levels of LDLR and lower LDL-C levels in the liver and plasma, respectively, than the control mice. Mechanistic analysis revealed that PCSK9-induced endocytosis and lysosomal degradation of LDLR were mediated by caveolin but not by clathrin, and they were dependent on binding between CAP1 and caveolin-1. CONCLUSION: We identified CAP1 as a new binding partner of PCSK9 and a key mediator of caveolae-dependent endocytosis and lysosomal degradation of LDLR.