Current Diagnosis and Management of Familial Hypobetalipoproteinemia 1.

Familial hypobetalipoproteinemia (FHBL) 1 is a rare genetic disorder with an autosomal codominant mode of inheritance and is caused by defects in the apolipoprotein (apo) B (APOB) gene that disable lipoprotein formation. ApoB proteins are required for the formation of very low-density lipoproteins (VLDLs), chylomicrons, and their metabolites. VLDLs transport cholesterol and triglycerides from the liver to the peripheral tissues, whereas chylomicrons transport absorbed lipids and fat-soluble vitamins from the intestine. Homozygous or compound heterozygotes of FHBL1 (HoFHBL1) are extremely rare, and defects in APOB impair VLDL and chylomicron secretion, which result in marked hypolipidemia with malabsorption of fat and fat-soluble vitamins, leading to various complications such as growth disorders, acanthocytosis, retinitis pigmentosa, and neuropathy. Heterozygotes of FHBL1 are relatively common and are generally asymptomatic, except for moderate hypolipidemia and possible hepatic steatosis. If left untreated, HoFHBL1 can cause severe complications and disabilities that are pathologically and phenotypically similar to abetalipoproteinemia (ABL) (an autosomal recessive disorder) caused by mutations in the microsomal triglyceride transfer protein (MTTP) gene. Although HoFHBL1 and ABL cannot be distinguished from the clinical manifestations and laboratory findings of the proband, moderate hypolipidemia in first-degree relatives may help diagnose HoFHBL1. There is currently no specific treatment for HoFHBL1. Palliative therapy including high-dose fat-soluble vitamin supplementation may prevent or delay complications. Registry research on HoFHBL1 is currently ongoing to better understand the disease burden and unmet needs of this life-threatening disease with few therapeutic options.

The Association of the Cholesterol Efflux Capacity with the Paraoxonase 1 Q192R Genotype and the Paraoxonase Activity.

AIMS: Paraoxonase 1 (PON1) binds to high-density lipoprotein (HDL) and protects against atherosclerosis. However, the relationship between functional PON1 Q192R polymorphism, which is associated with the hydrolysis of paraoxon (POXase activity) and atherosclerotic cardiovascular disease (ASCVD), remains controversial. As the effect of PON1 Q192R polymorphism on the HDL function is unclear, we investigated the relationship between this polymorphism and the cholesterol efflux capacity (CEC), one of the biological functions of HDL, in association with the PON1 activity. METHODS: The relationship between PON1 Q192R polymorphisms and CEC was investigated retrospectively in 150 subjects without ASCVD (50 with the PON1 Q/Q genotype, 50 with the Q/R genotype, and 50 with the R/R genotype) who participated in a health screening program. The POXase and arylesterase (AREase: hydrolysis of aromatic esters) activities were used as measures of the PON1 activity. RESULTS: The AREase activity was positively correlated with CEC independent of the HDL cholesterol levels. When stratified by the PON1 Q192R genotype, the POXase activity was also positively correlated with CEC independent of HDL cholesterol. PON1 Q192R R/R genotype carriers had a lower CEC than Q/Q or Q/R genotype carriers, despite having a higher POXase activity. Moreover, in a multiple regression analysis, the PON1 Q192R genotype was associated with the degree of CEC, independent of the HDL cholesterol and POXase activity. CONCLUSIONS: The PON1 Q192R R allele is associated with reduced CEC in Japanese people without ASCVD. Further studies on the impact of this association on the severity of atherosclerosis and ASCVD development are thus called for.

Transitional Medicine of Intractable Primary Dyslipidemias in Japan.

Transitional medicine refers to the seamless continuity of medical care for patients with childhood-onset diseases as they grow into adulthood. The transition of care must be seamless in medical treatment as the patients grow and in other medical aids such as subsidies for medical expenses in the health care system. Inappropriate transitional care, either medical or social, directly causes poorer prognosis for many early-onset diseases, including primary dyslipidemia caused by genetic abnormalities. Many primary dyslipidemias are designated as intractable diseases in the Japanese health care system for specific medical aids, as having no curative treatment and requiring enormous treatment costs for lipid management and prevention of complications. However, there are problems in transitional medicine for primary dyslipidemia in Japan. As for the medical treatment system, the diagnosis rate remains low due to the shortage of specialists, their insufficient link with generalists and other field specialists, and poor linkage between pediatricians and physicians for adults. In the medical care system, there is a mismatch of diagnostic criteria of primary dyslipidemias between children and adults for medical care expense subsidization, as between The Program for the Specific Pediatric Chronic Diseases and the Program for Designated Adult Intractable Diseases. This could lead some patients subsidized in their childhood to no longer be under the coverage of the aids after transition. This review intends to describe these issues in transitional medicine of primary dyslipidemia in Japan as a part of the efforts to resolve the problems by the Committee on Primary Dyslipidemia under the Research Program on Rare and Intractable Disease of the Ministry of Health, Labour and Welfare of Japan.

Impaired Cholesterol Efflux Capacity rather than Low HDL-C Reflects Oxidative Stress under Acute Myocardial Infarction.

AIMS: Acute myocardial infarction (AMI) causes irreversible damage to cardiomyocytes due to the discontinuation of oxygen supply and leads to systemic oxidative stress. It has been reported that high-density lipoprotein (HDL) particles have antioxidant capacity, and reduced antioxidant capacity is associated with decreased cholesterol efflux capacity (CEC). The purpose of this study was to clarify the usefulness of CEC measurement in patients with AMI. METHODS: We investigated the association between CEC and oxidative stress status in a case-control study. This study included 193 AMI cases and 445 age- and sex-matched controls. We examined the associations of CEC with HDL-cholesterol (HDL-C) and oxidized human serum albumin (HSA), an index of systemic oxidative stress status, and the effect of aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism, which has been reported to affect HDL-C level and risk for MI, on these associations. RESULTS: Both bivariable and multivariable analyses showed that CEC was positively correlated with HDL-C levels in both AMI cases and controls, with a weaker correlation in AMI cases than in controls. In AMI cases, oxidized HSA levels were associated with CEC in both bivariable and multivariable analyses, but not with HDL-C. These associations did not differ among the ALDH2 genotypes. CONCLUSIONS: CEC, but not HDL-C level, reflects systemic oxidative stress status in patients with AMI. CEC measurement for patients with AMI may be useful in that it provides information on systemic oxidative stress status as well as atherosclerosis risk.

Detectability of and interference by major and minor hemoglobin variants using a new-generation ion-exchange HPLC system with two switchable analysis modes.

Objectives: High-performance liquid chromatography (HPLC) is commonly used to measure hemoglobin A1c (HbA1c) levels and detect hemoglobin variants (Hb-Vars). HLC-723GR01 (GR01) is a new-generation automated ion-exchange HPLC system with two switchable analysis modes, namely short (30 s/test) and long modes (50 s/test). We evaluated the general performance of both analysis modes of GR01 for quantifying HbA1c and detecting Hb-Vars. Design and methods: We evaluated the instrument's precision based on CLSI protocol EP-05-A3. A comparison of the two analysis modes of GR01 against the standard mode of HLC-723G11 was performed on 100 whole blood samples. The GR01 long mode was compared with affinity HPLC (AF-HPLC) for detecting common Hb-Vars (HbE, HbD, HbS, and HbC, >20 samples). To examine the detection capability for minor Hb-Vars, we analyzed 26 Hb-Vars using multiple analyzers, including both analysis modes of GR01. Results: Both modes of GR01 had within-laboratory coefficients of variation of ≤1.0 % from four samples with HbA1c concentrations of 32-86 mmol/mol. Good correlation was observed between GR01 and HLC-723G11. The results for HbA1c detection in the presence of the major variants revealed a strong correlation between the long mode of GR01 and AF-HPLC (r = 0.986-0.998), and the difference biases ranged 0.1-1.9 mmol/mol. In the long mode, only one variant had a difference bias exceeding 14 % [10 % (%NGSP)]. Conclusion: The two analysis modes of GR01 were fast and had high accuracy and reproducibility, indicating their utility for routine clinical use in measuring HbA1c samples with Hb-Vars.

Clinical Characteristics of Homozygous Familial Hypercholesterolemia in Japan: A Survey Using a National Database.

Background: The studies evaluating patients' characteristics and lipid-lowering therapy for patients with homozygous familial hypercholesterolemia (HoFH) are scarce. Objectives: This study aims to evaluate the characteristics of and treatments for patients with HoFH. Methods: This study included 201 patients who were diagnosed with definite or probable HoFH from the National Database of the Japanese Ministry of Health, Labour, and Welfare. Results: The patients' median age at diagnosis was 27 years and exhibited a bimodal distribution. Approximately 70% of patients had coronary artery disease. Regarding genetic backgrounds, mutations in the low-density lipoprotein (LDL) receptor (LDLR) were identified in most of the patients, followed by proprotein convertase subtilisin/kexin type 9 (PCSK9) and double heterozygotes of LDLR. High-intensity statins were introduced to 74% of the patients, lipoprotein apheresis was performed in 21%, and PCSK9 inhibitors were administered to 50%. The mean of LDL cholesterol before and after treatment were 10.1 mmol/L and 3.9 mmol/L, respectively. Patients with coronary artery disease had significantly decreased LDL cholesterol. A quarter of the patients (n = 49, 24%) exhibited valvular diseases, particularly aortic valvular disease (n = 34, 61%). Conclusions: The national epidemiological study of patients with HoFH showed patient's clinical and genetic characteristics and LDL-lowering therapy in Japan. There was considerable diversity in the severity of phenotypes, including LDL cholesterol levels, among patients with HoFH. In Japan, the management of LDL cholesterol in HoFH is still inadequate despite the availability of intensive lipid-lowering therapies.

The real-world data of lipid-lowering treatment in patients with peripheral artery disease and its association with severity of disease.

BACKGROUND: The risk of coronary artery disease in peripheral arterial disease (PAD) is high, life prognosis is poor, and lipid-lowering treatment with statins has been reported to improve prognosis. In clinical practice, however, hypolipidemia is more common in patients with severe PAD and statin prescription rates appear to be low, but specific data are scarce in Japan. Therefore, we conducted this cross-sectional study in collaboration with other centers of vascular surgery to determine the rate of statin prescriptions for PAD patients in real-world practice, the rate of achievement of low-density lipoprotein (LDL) cholesterol control targets, and whether statin non-use is a determinant factor of critical limb ischemia (CLI). METHODS: A total of 246 PAD patients (97 with CLI) from 5 sites were included in this study. Medical history and blood test data were obtained from medical records and interviews with patients, and were compared between CLI and non-CLI patients. RESULTS: Statin prescription rate was only 34 %. The overall LDL cholesterol control target rate was 46 % of CLI cases and 51 % of non-CLI cases, according to the lipid management criteria of the Japanese Society for Atherosclerosis 2022 guidelines. Patients in the CLI group had a lower mean body mass index and lower LDL cholesterol levels than those in the non-CLI group, suggesting that these factors were responsible for the lower statin prescription rate. However, multivariate analysis revealed that statin non-use was one of the determinants of CLI. CONCLUSIONS: Statin prescription rates for PAD patients were low in real-world practice settings in the field of vascular surgery. Since statin non-use is a determinant of CLI, there is a need to educate physicians engaged in treatment regarding lipid-lowering treatment with statins.

Association between Familial Hypercholesterolemia and Serum Levels of Cholesterol Synthesis and Absorption Markers: The CACHE Study FH Analysis.

AIM: Serum levels of cholesterol absorption and synthesis markers are known to be associated with cardiovascular risk. Familial hypercholesterolemia (FH) is a well-known inherited disorder presenting elevated low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels and premature coronary disease. In this study, we aim to examine the differences in terms of serum markers of cholesterol metabolism between FH and non-FH individuals and to examine their associations with serum lipid levels. METHODS: In this study, we utilized data on serum markers of cholesterol metabolism, namely, lathosterol (Latho, synthesis marker), campesterol (Campe, absorption marker), and sitosterol (Sito, absorption marker) measured by gas chromatography of the CACHE consortium, which comprised of 13 research groups in Japan. Clinical data were compiled using REDCap system. Among the 2944 individuals in the CACHE population, we selected individuals without lipid-lowering medications and hemodialysis patients for this CACHE study FH analysis. Multivariable adjustment was performed to assess the associations. RESULTS: In this study, we analyzed data from 51 FH patients and 1924 non-FH individuals. After adjustment for possible confounders, the FH group was shown to have significantly higher Campe and Sito concentrations and insignificantly higher Latho concentrations than the non-FH group. These marker concentrations showed nonlinear associations with TC in the FH group. Campe/Latho and Sito/Latho ratios were significantly higher in the FH group than in the non-FH group. CONCLUSION: FH group had significantly elevated serum Campe and Sito concentrations and insignificantly elevated Latho concentrations; thus, intestinal cholesterol absorption relative to hepatic cholesterol synthesis was suggested to be elevated in patients with FH. Serum Latho, Campe, and Sito concentrations showed nonlinear associations with TC in the FH group.

Additive Effects of Drinking Habits and a Susceptible Genetic Polymorphism on Cholesterol Efflux Capacity.

AIMS: High levels of high-density lipoprotein cholesterol (HDL-C) are not necessarily effective in preventing atherosclerotic cardiovascular disease, and cholesterol efflux capacity (CEC) has attracted attention regarding HDL functionality. We aimed to elucidate whether drinking habits are associated with CEC levels, while also paying careful attention to confounding factors including serum HDL-C levels, other life style factors, and rs671 (＊2), a genetic polymorphism of the aldehyde dehydrogenase 2 (ALDH2) gene determining alcohol consumption habit. METHODS: A cross-sectional study was performed in 505 Japanese male subjects who were recruited from a health screening program. Associations of HDL-C and CEC levels with drinking habits and ALDH2 genotypes were examined. RESULTS: The genotype frequencies of ALDH2 ＊1/＊1 (homozygous wild-type genotype), ＊1/＊2 and ＊2/＊2 (homozygous mutant genotype) were 55%, 37% and 8%, respectively. Both HDL-C and CEC levels were higher in ALDH2 ＊1/＊1 genotype carriers than in ＊2 allele carriers. Although HDL-C levels were higher in subjects who had a drinking habit than in non-drinkers, CEC levels tended to be lower in subjects with ≥ 46 g/day of alcohol consumption than in non-drinkers. Furthermore, CEC levels tended to be lower in ALDH2 ＊1/＊1 genotype carriers with a drinking habit of ≥ 46 g/day than non-drinkers, while for ＊2 allele carriers, CEC levels tended to be lower with a drinking habit of 23-45.9 g/day compared to no drinking habit. CONCLUSIONS: Our results suggest that heavy drinking habits may tend to decrease CEC levels, and in the ALDH2 ＊2 allele carriers, even moderate drinking habits may tend to decrease CEC levels.

A Low-Frequency APOB p.(Pro955Ser) Variant Contributes to the Severity of/Variability in Familial Hypercholesterolemia.

CONTEXT: Heterozygous familial hypercholesterolemia (HeFH) is caused by a rare pathogenic variant in the LDLR, APOB, and PCSK9 genes. However, the causative variants in these genes have not been identified in approximately 40% of HeFH patients. OBJECTIVE: Our aim was to identify novel (or additional) genes/variants that contribute to HeFH. METHODS: Whole-exome sequencing was performed for 215 family members from 122 families with HeFH without pathogenic variants in the LDLR or PCSK9 genes. RESULTS: We could not find novel causative familial hypercholesterolemia (FH) genes/variants by family analysis. Next, we examined all APOB variants. Twenty-four nonsynonymous APOB variants were identified. The allele frequencies of the c.2863C > T:p.(Pro955Ser) variant in the HeFH probands and the general Japanese population were 0.15 and 0.034, respectively [odds ratio 4.9 (95% CI 3.4-7.1); P = 6.9 × 10-13]. The patients harboring the c.2863C > T:p.(Pro955Ser) variant accounted for 9.8% (n = 63) of unrelated patients with HeFH (n = 645). The penetrance of the c.2863C > T:p.(Pro955Ser) variant was low in the pedigree-based genetic analysis. In an in vitro assay, low-density lipoprotein (LDL) uptake from patients with the homozygous c.2863C > T:p.(Pro955Ser) variant was 44% of the LDL uptake from control subjects, and it was similar to that of the LDL uptake from patients with the known pathogenic heterozygous p.(Arg3527Gln) variant. CONCLUSIONS: The low-frequency APOB c.2863C > T:p.(Pro955Ser) variant is not an FH-causative variant, but it has a moderate effect size in HeFH. These findings suggest that the combination of the APOB c.2863C > T:p.(Pro955Ser) variant and age, environmental factors, or other genetic factors contributes to the severity of or variability in the HeFH phenotype.

HDL, cholesterol efflux, and ABCA1: Free from good and evil dualism.

Homozygotes for loss-of-function mutations in ABCA1 cause Tangier disease. The phenotype of their markedly reduced or loss of blood high-density lipoprotein (HDL) cholesterol, as well as examination of ATP-binding cassette transporter A1 (ABCA1)-deficient mice, proved that ABCA1 is a key player in HDL production. The ABCA1-mediated cholesterol efflux is the first step in the reverse cholesterol transport system and understanding the regulation of its expression was expected to lead to the development of anti-atherosclerotic drugs. However, from the viewpoint of intracellular cholesterol homeostasis, it is difficult to say that simple activation of ABCA1 or promotion of cholesterol efflux is a good strategy. To date, there is no evidence that HDL-increasing drugs by enhancing ABCA1 expression prevent atherosclerotic disease in humans. On the other hand, in situations where intracellular cholesterol homeostasis is disrupted by inflammation, aging, or metabolic abnormalities, a strategy that restores reduced ABCA1 expression and cholesterol efflux in a timely and localized manner may be useful.

The impact of gene variants on the thickness and softness of the Achilles tendon in familial hypercholesterolemia.

BACKGROUND AND AIMS: Familial hypercholesterolemia (FH) is characterized by high low-density lipoprotein (LDL)-cholesterol, xanthoma of the Achilles tendon (AT), and premature coronary artery disease (CAD). Ultrasonography can assess AT thickness and softness, making it useful for evaluating AT in FH diagnosis. We aimed to clarify whether FH-causative LDLR or PCSK9 variants affect AT thickness or softness. METHODS: In total, 248 FH and 60 non-familial hypercholesterolemia (non-FH) patients (total: 308) aged ≥30 years were enrolled. Patients with FH were classified according to genotype. AT thickness and elasticity index (EI) as softness were measured by ultrasonography. RESULTS: In FH patients with LDLR variants, AT was significantly thicker and softer than it was in FH patients with PCSK9 variants, FH patients without LDLR or PCSK9 variants, and patients with non-FH. The proportion of patients harboring LDLR variants significantly increased with AT thickness (p = 2.0 × 10-31) and softness (p = 1.4 × 10-18). Among those with AT thickness>8.5 mm and EI < 3.9, patients with LDLR variants accounted for 89% and 83%, respectively. The odds of AT thickening, AT softening and CAD increased 13.3-fold, 4.9-fold, and 2.1-fold, adjusted for the LDL-C year score by the presence of LDLR variants compared with those of patients without LDLR or PCSK9 variants. PCSK9 variants did not influence AT thickening or softening or CAD prevalence. CONCLUSIONS: LDLR variants affected AT thickness and softness independent of the LDL-C year score, but PCSK9 variants did not. Evaluating AT is important for identifying FH patients with LDLR variants at high risk for CAD.

Characterization of Polyvascular Disease in Heterozygous Familial Hypercholesterolemia: Its Association With Circulating Lipoprotein(a) Levels.

Background Heterozygous familial hypercholesterolemia (HeFH) more likely exhibits extensive atherosclerotic disease at multiple vascular beds. Lipoprotein(a) (Lp(a)) is an atherogenic lipoprotein that elevates HeFH-related atherosclerotic cardiovascular disease risks. Whether circulating Lp(a) level associates with polyvascular propagation of atherosclerosis in subjects with HeFH remains uncertain. Methods and Results The current study analyzed 370 subjects with clinically diagnosed HeFH who received evaluation of systemic arteries. Polyvascular disease (polyVD) was defined as more than 2 coexisting atherosclerosis conditions including coronary artery disease, carotid stenosis, or peripheral artery disease. Clinical characteristics and lipid features were analyzed in subjects with HeFH and polyVD; 5.7% of patients with HeFH (21/370) had polyVD. They were more likely to have a clustering of risk factors, tendon (P<0.001) and skin xanthomas (P=0.004), and corneal arcus (P=0.026). Furthermore, an elevated Lp(a) level (P=0.006) and a greater frequency of Lp(a) level ≥50 mg/dL (P<0.001) were observed in subjects with HeFH and polyVD. On multivariable analysis adjusting risk factors and lipid-lowering agents, Lp(a) ≥50 mg/dL (odds ratio [OR], 5.66 [95% CI, 1.68-19.0], P=0.005), age, and family history of premature coronary artery disease independently predicted polyVD in subjects with HeFH. Of note, the prevalence of polyVD rose to 33.3% in patients with HeFH and age >58 years old, family history of premature coronary artery disease, and Lp(a) ≥50 mg/dL (OR, 10.3 [95% CI, 3.12-33.4], P<0.001). Conclusions An increased level of circulating Lp(a) levels predicted concomitance of polyVD in patients with HeFH. The current findings suggest subjects with HeFH and Lp(a) ≥50 mg/dL as a high-risk category who require meticulous screening of systemic vascular beds.

Association between Achilles Tendon Softness and Atherosclerotic Cardiovascular Disease in Patients with Familial Hypercholesterolemia.

AIMS: Achilles tendon (AT) xanthomas are a specific physical finding of familial hypercholesterolemia (FH) and AT thickness has been used for its diagnosis and evaluation of its severity. Recently, we reported that the AT of FH patients was softer than that of non-FH patients and the combined use of a cut-off value for AT softness with that for AT thickness improved diagnostic accuracy. However, an association between AT softness and severity of atherosclerosis has not been reported. Accordingly, the present study aimed to investigate whether AT softness was associated with carotid atherosclerosis and presence of atherosclerotic cardiovascular disease (ASCVD) in FH. METHODS: The AT of 176 genetically diagnosed FH patients and 98 non-FH patients was examined to measure AT thickness and the elasticity index (EI) as an indicator for assessing AT softness using ultrasonography. RESULTS: Increased age was associated with AT softness, and overweight was negatively related to AT softness. There were significant inverse correlations between EI and maximum and mean intima-media thickness (IMT) within the common carotid artery only among FH patients. In multiple linear regression analysis, although the relationship between EI and mean IMT was attenuated, the association between EI and maximum IMT remained robust. In logistic regression analysis adjusted for age, sex and traditional cardiovascular risk factors (smoking history, presence of hypertension, presence of diabetes mellitus, overweight, LDL-cholesterol, HDL-cholesterol, and Log triglycerides), EI was associated with presence of ASCVD (Odds ratio per 1-SD increase, 0.37; 95% CI, 0.15 - 0.86; P=0.0252). CONCLUSION: The degree of lipid deposition in the AT of FH patients could be assessed by its thickness as well as its softness. AT softness is not only useful in diagnosing FH but is also associated with the severity of carotid atherosclerosis and presence of ASCVD. In addition, these findings suggest that AT softness would be helpful in risk assessment for FH patients.