RESUMO
Familial Hypercholesterolemia (FH) is an inherited disorder that significantly increases an individual's risk of developing premature cardiovascular disease (CVD). Early intervention involving lifestyle modification and medication is crucial in preventing CVD. Prior studies have shown that lipid-lowering therapy in children is safe and effective. Despite FH being a treatable and manageable condition, the condition is still underdiagnosed and undertreated. Universal lipid screening (ULS) in children has been recommended by some medical experts in the United States as a strategy to identify cases of FH and maximize the benefits of early invention. However, lipid screening is not routinely offered in pediatric clinics. This study aimed to explore parental experience with FH diagnosis in their children, identify key facilitators and barriers in children's diagnosis and care, and examine parental perspectives on ULS in children in the United States. A total of fourteen semi-structured interviews were conducted with participants recruited through the Family Heart Foundation. Thematic analysis identified three key themes: role of family history in facilitating child's FH diagnosis, barriers and challenges in post-diagnosis care, and attitudes towards ULS in children. All participants supported ULS in children and emphasized the value of early diagnosis and treatment for FH. However, a lack of guidance or referral after the child's diagnosis was a concern raised by many participants. This underscores the need for accessible and comprehensive care amid ongoing efforts to increase pediatric diagnosis of FH.
RESUMO
Background: Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by increased LDL-cholesterol levels. About 85% of FH cases are caused by LDLR mutations encoding the low-density lipoprotein receptor (LDLR). LDLR is synthesized in the endoplasmic reticulum (ER) where it undergoes post-translational modifications and then transported through Golgi apparatus to the plasma membrane. Over 2900 LDLR variants have been reported in FH patients with limited information on the pathogenicity and functionality of many of them. This study aims to elucidate the cellular trafficking and functional implications of LDLR missense variants identified in suspected FH patients using biochemical and functional methods. Methods: We used HeLa, HEK293T, and LDLR-deficient-CHO-ldlA7 cells to evaluate the subcellular localization and LDL internalization of ten LDLR missense variants (p.C167F, p.D178N, p.C243Y, p.E277K, p.G314R, p.H327Y, p.D477N, p.D622G, p.R744Q, and p.R814Q) reported in multiethnic suspected FH patients. We also analyzed the functional impact of three variants (p.D445E, p.D482H, and p.C677F), two of which previously shown to be retained in the ER. Results: We show that p.D622G, p.D482H, and p.C667F are largely retained in the ER whereas p.R744Q is partially retained. The other variants were predominantly localized to the plasma membrane. LDL internalization assays in CHO-ldlA7 cells indicate that p.D482H, p.C243Y, p.D622G, and p.C667F have quantitatively lost their ability to internalize Dil-LDL with the others (p.C167F, p.D178N, p.G314R, p.H327Y, p.D445E, p.D477N, p.R744Q and p.R814Q) showing significant losses except for p.E277K which retained full activity. However, the LDL internalization assay is only to able evaluate the impact of the variants on LDL internalization and not the exact functional defects such as failure to bind LDL. The data represented illustrate the hypomorphism nature of variants causing FH which may explain some of the variable expressivity of FH. Conclusion: Our combinatorial approach of in silico, cellular, and functional analysis is a powerful strategy to determine pathogenicity and FH disease mechanisms which may provide opportunitites for novel therapeutic strategies.