Genetics of Hypercholesterolemia: Comparison Between Familial Hypercholesterolemia and Hypercholesterolemia Nonrelated to LDL Receptor

Severe hypercholesterolemia (HC) is defined as an elevation of total cholesterol (TC) due to the increase in LDL cholesterol (LDL-C) >95th percentile or 190 mg/dl. The high values of LDL-C, especially when it is maintained over time, is considered a risk factor for the development of atherosclerotic cardiovascular disease (ASCVD), mostly expressed as ischemic heart disease (IHD). One of the best characterized forms of severe HC, familial hypercholesterolemia (FH), is caused by the presence of a major variant in one gene (LDLR, APOB, PCSK9, or ApoE), with an autosomal codominant pattern of inheritance, causing an extreme elevation of LDL-C and early IHD. Nevertheless, an important proportion of serious HC cases, denominated polygenic hypercholesterolemia (PH), may be attributed to the small additive effect of a number of single nucleotide variants (SNVs), located along the whole genome. The diagnosis, prevalence, and cardiovascular risk associated with PH has not been fully established at the moment. Cascade screening to detect a specific genetic defect is advised in all first- and second-degree relatives of subjects with FH. Conversely, in the rest of cases of HC, it is only advised to screen high values of LDL-C in first-degree relatives since there is not a consensus for the genetic diagnosis of PH. FH is associated with the highest cardiovascular risk, followed by PH and other forms of HC. Early detection and initiation of high-intensity lipid-lowering treatment is proposed in all subjects with severe HC for the primary prevention of ASCVD, with an objective of LDL-C <100 mg/dl or a decrease of at least 50%. A more aggressive reduction in LDL-C is necessary in HC subjects who associate personal history of ASCVD or other cardiovascular risk factors

Current causes of death in familial hypercholesterolemia

Background Familial hypercholesterolemia (FH) is a codominant autosomal disease characterized by high low-density lipoprotein cholesterol (LDLc) and a high risk of premature cardiovascular disease (CVD). The molecular bases have been well defined, and effective lipid lowering is possible. This analysis aimed to study the current major causes of death of genetically defined heterozygous familial hypercholesterolemia (heFH). Methods A case‒control study was designed to analyse life-long mortality in a group of heFH and control families. Data from first-degree family members of cases and controls (nonconsanguineous cohabitants), including deceased relatives, were collected from a questionnaire and review of medical records. Mortality was compared among heFH patients, nonheFH patients, and nonconsanguineous family members. Results A total of 813 family members were analysed, 26.4% of whom were deceased. Among the deceased, the mean age of death was 69.3 years in heFH individuals, 73.5 years in nonheFH individuals, and 73.2 years in nonconsanguineous individuals, without significant differences. CVD was the cause of death in 59.7% of heFH individuals, 37.7% of nonheFH individuals, and 37.4% of nonconsanguineous individuals (P = 0.012). These differences were greater after restricting the analyses to parents. The hazard ratio of dying from CVD was 2.85 times higher (95% CI, (1.73–4.69) in heFH individuals than in individuals in the other two groups (non-FH and nonconsanguineous), who did not differ in their risk. Conclusions CVD mortality in heFH individuals is lower and occurs later than that described in the last century but is still higher than that in non-FH individuals. This improved prognosis of CVD risk is not associated with changes in non-CVD mortality

Effect of intensive LDL cholesterol lowering with PCSK9 monoclonal antibodies on tendon xanthoma regression in familial hypercholesterolemia

Background and aims: The effect of LDLc lowering with PCSK9 antibodies on tendon xanthomas (TX) is unknown. Methods: TX was measured in 24 heterozygous familial hypercholesterolemia (HeFH) cases and in 24 HeFH controls with or without PCSK9 inhibitors for at least one year. Results: Exposure to PCSK9 inhibitors in cases was 2.96 ± 1.33 years. LDLc decreased 80.8 ± 7.66% in cases and 56.9 ± 11.1% in controls. There was a decrease in maximum (-5.03%) and mean (-5.32%) TX in cases but not in controls (+3.97%, +3.16, respectively, p = 0.01). PCSK9 inhibitor treatment was independently associated with TX reduction. Conclusion: Addition of a PCSK9 inhibitor to statin and ezetimibe resulted in a greater decrease in LDLc and TX after 3 years of treatment

ANGPTL3 gene variants in subjects with familial combined hyperlipidemia

Angiopoietin-like 3 (ANGPTL3) plays an important role in lipid metabolism in humans. Loss-of-function variants in ANGPTL3 cause a monogenic disease named familial combined hypolipidemia. However, the potential contribution of ANGPTL3 gene in subjects with familial combined hyperlipidemia (FCHL) has not been studied. For that reason, the aim of this work was to investigate the potential contribution of ANGPTL3 in the aetiology of FCHL by identifying gain-of-function (GOF) genetic variants in the ANGPTL3 gene in FCHL subjects. ANGPTL3 gene was sequenced in 162 unrelated subjects with severe FCHL and 165 normolipemic controls. Pathogenicity of genetic variants was predicted with PredictSNP2 and FruitFly. Frequency of identified variants in FCHL was compared with that of normolipemic controls and that described in the 1000 Genomes Project. No GOF mutations in ANGPTL3 were present in subjects with FCHL. Four variants were identified in FCHL subjects, showing a different frequency from that observed in normolipemic controls: c.607-109T>C, c.607-47_607-46delGT, c.835+41C>A and c.*52_*60del. This last variant, c.*52_*60del, is a microRNA associated sequence in the 3'UTR of ANGPTL3, and it was present 2.7 times more frequently in normolipemic controls than in FCHL subjects. Our research shows that no GOF mutations in ANGPTL3 were found in a large group of unrelated subjects with FCHL

Bile acid synthesis precursors in subjects with genetic hypercholesterolemia negative for LDLR/APOB/PCSK9/APOE mutations. Association with lipids and carotid atherosclerosis

Some oxysterols are precursors of bile acid synthesis and play an important role in cholesterol homeostasis. However, if they are involved in the pathogeny of genetic hypercholesterolemia has not been previously explored. We have studied non-cholesterol sterol markers of cholesterol synthesis (lanosterol and desmosterol) and oxysterols (7a-hydroxy-4-cholesten-3-one, 24S-hydroxycholesterol and 27-hydroxycholesterol) in 200 affected subjects with primary hypercholesterolemia of genetic origin, negative for mutations in LDLR, APOB, PCSK9 and APOE genes (non-FH GH) and 100 normolipemic controls. All studied oxysterols and cholesterol synthesis markers were significantly higher in affected subjects than controls (P < 0.001). Ratios of oxysterols to total cholesterol were higher in non-FH GH than in controls, although only 24S-hydroxycholesterol showed statistical significance (P < 0.001). Cholesterol synthesis markers had a positive correlation with BMI, triglycerides, cholesterol and apoB in control population. However, these correlations disappeared in non-FH GH with the exception of a weak positive correlation for non-HDL cholesterol and apoB. The same pattern was observed for oxysterols with high positive correlation in controls and absence of correlation for non-FH GH, except non-HDL cholesterol for 24S-hydroxycholesterol and 27-hydroxycholesterol and apoB for 27-hydroxycholesterol. All non-cholesterol sterols had positive correlation among them in patients and in controls. A total of 65 (32.5%) and 35 (17.5%) affected subjects presented values of oxysterols ratios to total cholesterol above the 95th percentile of the normal distribution (24S-hydroxycholesterol and 27-hydroxycholesterol, respectively). Those patients with the highest levels of 24S-hydroxycholesterol associated an increase in the carotid intima media thickness. These results suggest that bile acid metabolism is affected in some patients with primary hypercholesterolemia of genetic origin, negative for mutations in the candidate genes, and may confer a higher cardiovascular risk. Our results confirm that cholesterol synthesis overproduction is a primary defect in non-HF GH and suggest that subjects with non-FH GH show high levels of oxysterols in response to hepatic overproduction of cholesterol

Lipid-lowering response in subjects with the p.(Leu167del) mutation in the APOE gene

Background and aims: The aim of this work was to compared the effect of lipid lowering drugs among familial hypercholesterolemia (FH) subjects with a functional mutation in LDLR (LDLR FH) and FH with the p.(Leu167del) mutation in APOE. Methods: We retrospectively selected all adults with the p.(Leu167del) mutation on lipid-lowering treatment (n = 22) attending the Lipid Unit at the Hospital Miguel Servet. Age and sex matched LDLR FH from the same Unit were randomly selected as a control group (n = 44). Results: The mean percentage reduction in LDLc was significantly higher in the p.(Leu167del) carriers (-52.1%) than in the LDLR FH (-39.7%) (p = 0.040) when on high intensity statins. Similar differences between groups were observed in non-HDLc -49.4% and -36.4%, respectively (p = 0.030). Conclusions: Subjects with p.(Leu167del) mutation have a higher lipid-lowering response to statins with or without ezetimibe than LDLR FH. This supports the use of genetics for a more efficient management of FH

Tratamiento de un varón con enfermedad de McArdle y muy alto riesgo cardiovascular con inhibidores de PCSK9

Varón de 60 años con hiperlipidemia familiar combinada, cardiopatía isquémica y diabetes tipo 2. Desde la infancia, intolerancia al esfuerzo intenso. Se le diagnosticó enfermedad de McArdle a raíz de rabdomiólisis asociada a estatinas tras un infarto de miocardio. Desde entonces había seguido tratamiento con dieta, fibratos y ezetimiba con buena tolerancia, pero a pesar de ello las concentraciones de colesterol LDL (cLDL) eran >180 mg/dl. Se asoció al tratamiento alirocumab 150 mg subcutáneos cada 14 días, con excelente respuesta clínica y descenso de cLDL a 15 mg/dl, manteniéndose estable desde entonces. Nuestro caso demuestra que los inhibidores de PCSK9 son eficaces y seguros en pacientes con enfermedades musculares que contraindican las estatinas y que son una alternativa terapéutica ideal para este tipo de pacientes. A 60-year-old male with familial combined hyperlipidemia, ischemic heart disease and type 2 diabetes. Since childhood, intolerance to intense exercise. The patient was diagnosed of McArdle''s disease after an episode of rhabdomyolysis associated with statins as treatment after a myocardial infarction. Since then, he had been treated with diet, fibrates and ezetimibe with good tolerance, despite this, LDL cholesterol (cLDL) remained >180 mg/dl. He started to be treated with alirocumab 150 mg/sc every 14 days, with excellent clinical response and a decrease in cLDL to 15 mg/dl. Our case shows that PCSK9 inhibitors are effective and safe in patients with muscle diseases who have statin contraindication, and they are a good therapeutic tool for these patients

Different protein composition of low-calorie diet differently impacts adipokine profile irrespective of weight loss in overweight and obese women

Background and aims: High-protein (HP) diets have shown benefits in cardiometabolic markers such as insulin or triglycerides but the responsible mechanisms are not known. We aimed to assess the effect of three energy-restricted diets with different protein contents (20%, 27%, and 35%; similar to 80% coming from animal source) on plasma adipokine concentration and its association with changes in cardiometabolic markers. Methods: Seventy-six women (BMI 32.8 +/- 2.93) were randomized to one of three calorie-reduced diets, with protein, 20%, 27%, or 35%; carbohydrates, 50%, 43%, or 35%; and fat, 30%, for 3 months. Plasma adipokine (leptin, resistin, adiponectin, and retinol-binding protein 4; RBP4) levels were assessed. Results: After 3 months, leptin concentration decreased in all groups without differences among them, while resistin levels remained unchanged. Adiponectin concentration heterogeneously changed in all groups (P for trend = 0.165) and resistin concentration did not significantly change. RPB4 significantly decreased by -17.5% (-31.7, -3.22) in 35%-protein diet (P for trend = 0.024 among diets). Triglycerides improved in women following the 35%-protein diet regardless of weight loss; RBP4 variation significantly influenced triglyceride concentration change by 24.9% and 25.9% when comparing 27%- and 35%- with 20%-protein diet, respectively. Conclusions: A 35%-protein diet induced a decrease in RBP4 regardless of weight loss, which was directly associated with triglyceride concentration improvement. These findings suggest that HP diets improve the cardiometabolic profile, at least in part, through changes in adipokine secretion. Whether this beneficial effect of HP diet is due to improvements in hepatic or adipose tissue functionality should be elucidated

Glycerol kinase deficiency in adults: Description of 4 novel cases, systematic review and development of a clinical diagnostic score

Background and aims: Glycerol kinase deficiency (GKD) is a rare genetic disorder characterized by hyperglycerolemia and glyceroluria, which could be misdiagnosed as a moderate to severe hypertriglyceridemia (HTG). We aimed to describe four novel cases of GKD, to complete a systematic review of all cases of isolated GKD published so far, and to develop a suspicion clinical diagnostic score for GKD. Methods: We reported four cases with suspicion of GKD and compared their phenotype with 584 males with triglycerides (TG) > 300 mg/dL, selected as control group (HTG non-GKD). The GK gene was sequenced in all cases. Lipoprotein particle concentrations were measured in all cases with GKD. The systematic review involved a PubMed, Cochrane and Scopus databases search to identify anthropometric and biochemical characteristics of all described cases with GKD. Results: The systematic review retrieved a total of 15 articles involving 39 subjects with GKD. GKD cases reported a history of high TG levels resistant to lipid-lowering therapy. Compared to GKD subjects (n = 43), HTG non-GKD subjects (n = 584) showed significantly higher BMI, total cholesterol, non-HDL cholesterol and gamma-glutamyltransferase, significantly lower HDL cholesterol and TG, and higher prevalence of diabetes. The proposed diagnostic score was significantly higher in GKD than in HTG non-GKD subjects. Conclusions: This is the first systematic review that compiles all GKD cases reported to date including 4 novel cases, and examine the differential GKD phenotype compared to other types of HTG. The proposed score would have a broad utility in clinical practice to avoid unwarranted lipid lowering treatment in GKD patients