Familial Hypercholesterolemia: JACC Focus Seminar 4/4

Detecting familial hypercholesterolemia (FH) early and "normalizing" low-density lipoprotein (LDL) cholesterol values are the 2 pillars for effective cardiovascular disease prevention in FH. Combining lipid-lowering therapies targeting synergistic/complementary metabolic pathways makes this feasible, even among severe phenotypes. For LDL receptor-dependent treatments, PCSK9 remains the main target for adjunctive therapy to statins and ezetimibe through a variety of approaches. These include protein inhibition (adnectins), inhibition of translation at mRNA level (antisense oligonucleotides or small interfering RNA), and creation of loss-of-function mutations through base-pair editing. For patients with little LDL receptor function, LDL receptor-independent treatment targeting ANGPTL3 through monoclonal therapies are now available, or in the future, antisense/small interfering RNA-based approaches offer alternative approaches. Finally, first-in-human studies are ongoing, testing adenovirus-mediated gene therapy transducing healthy LDLR DNA in patients with HoFH. Further development of the CRISPR cas technology, which has shown promising results in vivo on introducing PCSK9 loss-of-function mutations, will move a single-dose, curative treatment for FH closer.

Investigating Lipid-Modulating Agents for Prevention or Treatment of COVID-19: JACC State-of-the-Art Review

Coronavirus disease-2019 (COVID-19) is associated with systemic inflammation, endothelial activation, and multiorgan manifestations. Lipid-modulating agents may be useful in treating patients with COVID-19. These agents may inhibit viral entry by lipid raft disruption or ameliorate the inflammatory response and endothelial activation. In addition, dyslipidemia with lower high-density lipoprotein cholesterol and higher triglyceride levels portend worse outcomes in patients with COVID-19. Upon a systematic search, 40 randomized controlled trials (RCTs) with lipid-modulating agents were identified, including 17 statin trials, 14 omega-3 fatty acids RCTs, 3 fibrate RCTs, 5 niacin RCTs, and 1 dalcetrapib RCT for the management or prevention of COVID-19. From these 40 RCTs, only 2 have reported preliminary results, and most others are ongoing. This paper summarizes the ongoing or completed RCTs of lipid-modulating agents in COVID-19 and the implications of these trials for patient management.

Icosapent ethyl: scientific and legal controversies

Icosapent ethyl (Vascepa) is a purified preparation of the omega-3 fatty acid eicosapentaenoic acid, which is marketed by Amarin Pharma based in Ireland. The product was initially approved by the US Food and Drug Administration for the use of a high dose (4 g/day) in the treatment of hypertriglyceridaemia. On the basis of the results of the REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl Intervention Trial), the agency later granted a label extension to include the additional indication of a reduction in risk of cardiovascular events in persons with serum triglyceride levels of 150 mg/dL or greater and established cardiovascular disease or diabetes. Data supporting the efficacy of omega-3 fatty acids in the prevention of cardiovascular disease have been inconsistent and controversial. The story of the development of icosapent ethyl has been fraught with challenges, including the invalidation of six core patents on the product, and recently, the completion of a new clinical trial, STRENGTH (Long-Term Outcomes Study to Assess STatin Residual Risk Reduction With EpaNova in HiGh CV Risk PatienTs With Hypertriglyceridemia), that directly contradicts REDUCE-IT and calls into question whether icosapent ethyl is actually effective in the secondary prevention of cardiovascular events. This article traces the course of the development of this fascinating product and discusses its complex medical, regulatory and legal history, which is still continuing to unfold.

FABP5 promotes lymph node metastasis in cervical cancer by reprogramming fatty acid metabolism

Patients with cervical cancer (CCa) with lymph node metastasis (LNM) have an extremely poor prognosis. Elucidation of the molecular mechanisms underlying LNM may provide clinical therapeutic strategies for CCa. Upregulation of fatty acid-binding protein 5 (FABP5) expression in CCa tumours was demonstrated to positively correlate with LNM. However, the precise role and mechanisms of FABP5 in the LNM of CCa remain unknown. Methods: The diagnostic value of FABP5 as a predictor of LNM in CCa was evaluated in CCa tumour samples. The functional role of FABP5 and its upstream and downstream regulatory factors were investigated by gain-of-function and loss-of-function assays in vitro and in vivo. A mouse model of LNM was used to determine the effect of FABP5 on LNM and the therapeutic value of FABP5 targeting. Results: We demonstrated that FABP5 was markedly upregulated in CCa with LNM and correlated with poor prognosis. FABP5 protein was an independent predictor of LNM in a multivariate logistic analysis. Furthermore, FABP5 promoted epithelial-mesenchymal transition, lymphangiogenesis, and LNM by reprogramming fatty acid (FA) metabolism. Mechanistically, FABP5 promoted lipolysis and FA synthesis, which led to an increase in intracellular fatty acids (FAs) that activated NF-κB signalling, thus inducing LNM. Importantly, administration of orlistat, which attenuates FA metabolism reprogramming, inhibited FABP5-induced LNM in CCa. The pro-metastatic effect of FABP5 was reduced by miR-144-3p. Moreover, miR-144-3p was significantly downregulated and FABP5 was upregulated in CCa in a hypoxic microenvironment. Conclusion: Our findings highlight a FA metabolism-dependent mechanism of FABP5-induced LNM. Moreover, the expression and biological function of FABP5 can be regulated by miR-144-3p in hypoxia. Our study identifies FABP5 as a potential diagnostic biomarker and therapeutic target for LNM in CCa.

Apical sodium-dependent bile acid transporter inhibition with volixibat improves metabolic aspects and components of non-alcoholic steatohepatitis in Ldlr-/-.Leiden mice

Interruption of bile acid recirculation through inhibition of the apical sodium-dependent bile acid transporter (ASBT) is a promising strategy to alleviate hepatic cholesterol accumulation in non-alcoholic steatohepatitis (NASH), and improve the metabolic aspects of the disease. Potential disease-attenuating effects of the ASBT inhibitor volixibat (5, 15, and 30 mg/kg) were investigated in high-fat diet (HFD)-fed Ldlr-/-.Leiden mice over 24 weeks. Plasma and fecal bile acid levels, plasma insulin, lipids, and liver enzymes were monitored. Final analyses included liver histology, intrahepatic lipids, mesenteric white adipose tissue mass, and liver gene profiling. Consistent with its mechanism of action, volixibat significantly increased the total amount of bile acid in feces. At the highest dose, volixibat significantly attenuated the HFD-induced increase in hepatocyte hypertrophy, hepatic triglyceride and cholesteryl ester levels, and mesenteric white adipose tissue deposition. Non-alcoholic fatty liver disease activity score (NAS) was significantly lower in volixibat-treated mice than in the HFD controls. Gene profiling showed that volixibat reversed the inhibitory effect of the HFD on metabolic master regulators, including peroxisome proliferator-activated receptor-γ coactivator-1β, insulin receptor, and sterol regulatory element-binding transcription factor 2. Volixibat may have beneficial effects on physiological and metabolic aspects of NASH pathophysiology.

Efficacy of bezafibrate on fibroblasts of glutaric acidemia type II patients evaluated using an in vitro probe acylcarnitine assay

INTRODUCTION

We evaluated the effects of bezafibrate (BEZ) on β-oxidation in fibroblasts obtained from patients with glutaric acidemia type II (GA2) of various clinical severities using an in vitro probe (IVP) assay.

METHODS

Cultured fibroblasts from 12 patients with GA2, including cases of the neonatal-onset type both with and without congenital anomalies (the prenatal- and neonatal-onset forms, respectively), the infantile-onset, and the myopathic forms, were studied. The IVP assay was performed by measuring acylcarnitines (ACs) in the cell culture medium of fibroblasts incubated with palmitic acid for 96h in the presence of 0-800μM BEZ using tandem mass spectrometry.

RESULTS

The IVP assay showed that 100μM BEZ markedly reduced the level of palmitoylcarnitine (C16) in the neonatal-onset, infantile-onset, and myopathic forms of GA2, either increasing or maintaining a high level of acetylcarnitine (C2), which serves as an index of energy production via β-oxidation. In the prenatal-onset form, although a small reduction of C16 was also observed in the presence of 100μM BEZ, the level of C2 remained low. At concentrations higher than 100μM, BEZ further decreased the level of ACs including C16, but a concentration over 400μM decreased the level of C2 in most cases.

DISCUSSION

BEZ at 100μM was effective for all GA2 phenotypes except for the prenatal-onset form, as a reduction of C16 without deterioration of C2 is considered to indicate improvement of β-oxidation. The effects of higher doses BEZ could not be estimated by the IVP assay but might be small or nonexistent.

Bile acid receptors in non-alcoholic fatty liver disease

Accumulating data have shown that bile acids are important cell signaling molecules, which may activate several signaling pathways to regulate biological processes. Bile acids are endogenous ligands for the farnesoid X receptor (FXR) and TGR5, a G-protein coupled receptor. Gain- and loss-of-function studies have demonstrated that both FXR and TGR5 play important roles in regulating lipid and carbohydrate metabolism and inflammatory responses. Importantly, activation of FXR or TGR5 lowers hepatic triglyceride levels and inhibits inflammation. Such properties of FXR or TGR5 have indicated that these two bile acid receptors are ideal targets for treatment of non-alcoholic fatty liver disease, one of the major health concerns worldwide. In this article, we will focus on recent advances on the role of both FXR and TGR5 in regulating hepatic triglyceride metabolism and inflammatory responses under normal and disease conditions.

The mechanism of lipid raft mediating chemoresistance of cervical cancer

OBJECTIVE

To investigate the mechanism of lipid raft mediating chemotherapy resistance in cervical cancer.

METHODS

This experiment was carried out in the Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China from June 2010 to February 2011. Hela cells were divided into 6 groups: control group (Ctrl), cisplatin group (Cis), lipid raft interference agent group (MCD), NADPH oxidase inhibitor group (Apo), lipid raft interference agent combined with cisplatin group (MCD+Cis), and NADPH oxidase inhibitor combined with cisplatin group (Apo+Cis). After the cervical cancer cells were treated with a correspondent agent for 24 hours, the number of surviving cells were measured utilizing cell counting kits-8 (CCK-8), and the hypoxia inducible factor-1alpha (HIF-1alpha) levels were detected by Western blotting. Reactive oxygen species (ROS) levels were measured indirectly by detection of dichlorodihydrofluorescein fluorescence activity.

RESULTS

The cell growth of MCD slowed down (survival cells was 62% compared with the Ctrl group), with the Apo group showing a similar effect (65% in the control group), and 49% for the Cis group, MCD+Cis was 21%, and Apo+Cis was 23%. While the level of HIF-1alpha protein and ROS of the MCD group, Apo group, Cis group, MCD+Cis group and Apo+Cis group were decreased significantly compared to the control group. The level of HIF-1alpha of MCD group decreased by 69.9%, Apo group by 60.2%, Cis group was 55.5%, MCD+Cis group by 21.1% and Apo+Cis group by 25.4%, while the level of ROS also decreased in the MCD group by 38.6%, Apo group by 35.3%, Cis group by 24%, MCD+Cis group by 12.3% and Apo+Cis group by 12.8%.

CONCLUSION

Lipid raft may up-regulate ROS level and HIF-1alpha expression through activating NADPH oxidase, and thus promote chemotherapy resistance in cervical cancer.

Function of the Niemann-Pick type C proteins and their bypass by cyclodextrin

PURPOSE OF REVIEW

This review summarizes the recent findings on the mechanism of action of the Niemann-Pick type C (NPC) proteins and their bypass by cyclodextrin.

RECENT FINDINGS

NPC disease is caused by dysfunction in either the NPC1 or NPC2 protein. These proteins function in the same pathway for the removal of unesterified cholesterol from late endosomes/lysosomes. In NPC-deficient cells, cholesterol derived from the endocytosis of LDLs becomes sequestered in the late endosomes/lysosomes. Recent studies have indicated that these two cholesterol-binding proteins act in tandem in mediating the egress of cholesterol from the late endosomes/lysosomes. Patches of amino acids on NPC1 and NPC2 appear to interact so that the hydrophobic transfer of cholesterol from NPC2 to NPC1 is achieved. Although no effective treatment for NPC disease is currently available, exciting new studies have shown that treatment of NPC-deficient mice with the cholesterol-binding compound, cyclodextrin, reduces the neurodegeneration and markedly extends the life span of Npc1-/- mice, suggesting a potential therapeutic approach for the treatment of individuals with NPC disease.

SUMMARY

Experimental data are consistent with a model for the sequential action of the NPC1 and NPC2 proteins in moving cholesterol out of the late endosomes/lysosomes. Recent data demonstrate that treatment of NPC-deficient mice with cyclodextrin extends their life span, thereby suggesting a potential therapy for NPC patients.