Serum lipids and coronary heart disease in heterozygous familial hypercholesterolemia in the Hokuriku District of Japan

Sex differences in treatment of familial hypercholesterolaemia: a meta-analysis

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) is a highly prevalent monogenic disorder characterized by elevated LDL cholesterol (LDL-C) levels and premature atherosclerotic cardiovascular disease. Sex disparities in diagnosis, lipid-lowering therapy, and achieved lipid levels have emerged worldwide, resulting in barriers to care in FH. A systematic review was performed to investigate sex-related disparities in treatment, response, and lipid target achievement in FH (PROSPERO, CRD42022353297).

METHODS

MEDLINE, Embase, The Cochrane library, PubMed, Scopus, PsycInfo, and grey literature databases were searched from inception to 26 April 2023. Records were eligible if they described sex differences in the treatment of adults with FH.

RESULTS

Of 4432 publications reviewed, 133 met our eligibility criteria. In 16 interventional clinical trials (eight randomized and eight non-randomized; 1840 participants, 49.4% females), there were no differences between males and females in response to fixed doses of lipid-lowering therapy, suggesting that sex was not a determinant of response. Meta-analysis of 25 real-world observational studies (129 441 participants, 53.4% females) found that females were less likely to be on lipid-lowering therapy compared with males (odds ratio .74, 95% confidence interval .66-.85). Importantly, females were less likely to reach an LDL-C < 2.5 mmol/L (odds ratio .85, 95% confidence interval .74-.97). Similarly, treated LDL-C levels were higher in females. Despite this, male sex was associated with a two-fold greater relative risk of major adverse cardiovascular events including myocardial infarction, atherosclerotic cardiovascular disease, and cardiovascular mortality.

CONCLUSIONS

Females with FH were less likely to be treated intensively and to reach guideline-recommended LDL-C targets. This sex bias represents a surmountable barrier to clinical care.

Genetic backgrounds and diagnosis of familial hypercholesterolemia

Lipid disorders play a critical role in the intricate development of atherosclerosis and its clinical consequences, such as coronary heart disease and stroke. These disorders are responsible for a significant number of deaths in many adult populations worldwide. Familial hypercholesterolemia (FH) is a genetic disorder that causes extremely high levels of LDL cholesterol. The most common mutations occur in genes responsible for low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), or proprotein convertase subtilisin/kexin type 9 (PCSK9). While genetic testing is a dependable method for diagnosing the disease, it may not detect primary mutations in 20%-40% of FH cases.

Familial hypercholesterolemia in Southeast and East Asia

Familial hypercholesterolemia (FH) is a relatively common autosomal dominant disorder associated with a significantly increased risk of coronary heart disease (CHD). Most (~85-90%) cases are due to pathogenic variants in the LDL-receptor gene (LDLR), while the remaining are due to pathogenic variants in the apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes, though the proportion may vary depending on geographic location. Even though at least a quarter of the world's FH population lives in Southeast and East Asia, there are substantial gaps in knowledge regarding the epidemiology of FH due to low awareness, the absence of national screening programs, and limited availability of genetic testing. In this review, we discuss the most recent and relevant information available related to diagnostic criteria, prevalence, awareness, clinical characteristics, genetic epidemiology, and treatment in the FH population of Southeast and East Asia. Increasing awareness and improving the diagnosis and management of FH will reduce the burden of premature CHD in these regions of the world.

Risk of Ischemic Stroke and Peripheral Arterial Disease in Heterozygous Familial Hypercholesterolemia: A Meta-Analysis

Heterozygous familial hypercholesterolemia (HeFH) is a common genetic disorder predisposing affected individuals to lifelong low-density lipoprotein cholesterol (LDL-C) elevation and coronary heart disease. However, whether HeFH increases the risk of peripheral arterial disease (PAD) and ischemic stroke is undetermined. We examined associations between HeFH and these outcomes in a comprehensive systematic review and meta-analysis. We searched MEDLINE, EMBASE, Global Health, the Cochrane Library, and PubMed (for ahead-of-print publications) for relevant English-language studies. Maximally adjusted risk estimates were pooled under random- and fixed-effects meta-analysis to derive odds ratios (ORs) and 95% confidence intervals (CIs). We included 6 studies representing 183 388 participants. Heterozygnous familial hypercholesterolemia was associated with a higher risk of PAD (OR: 3.59 [95% CI: 1.30-9.89]). This trend was nonsignificantly preserved (OR: 2.96 [95% CI: 0.68-12.88]) in sensitivity analyses of genetically defined HeFH. Genetic HeFH was not associated with increased ischemic stroke risk (OR: 0.76 [95% CI: 0.37-1.58]) although possessing an LDL-C >4.9 mmol/L (190 mg/dL) was (OR: 1.42 [95% CI: 1.06-1.89]). We found clinical and genetic diagnoses of HeFH to be associated with increased PAD risk. Genetically confirmed HeFH may not confer an increased risk of ischemic stroke. Modest associations may exist between LDL-C and ischemic stroke risk in HeFH.

Familial Hypercholesterolemia: New Horizons for Diagnosis and Effective Management

Familial hypercholesterolemia (FH) is a common genetic cause of premature cardiovascular disease (CVD). The reported prevalence rates for both heterozygous FH (HeFH) and homozygous FH (HoFH) vary significantly, and this can be attributed, at least in part, to the variable diagnostic criteria used across different populations. Due to lack of consistent data, new global registries and unified guidelines are being formed, which are expected to advance current knowledge and improve the care of FH patients. This review presents a comprehensive overview of the pathophysiology, epidemiology, manifestations, and pharmacological treatment of FH, whilst summarizing the up-to-date relevant recommendations and guidelines. Ongoing research in FH seems promising and novel therapies are expected to be introduced in clinical practice in order to compliment or even substitute current treatment options, aiming for better lipid-lowering effects, fewer side effects, and improved clinical outcomes.

Estimating the prevalence of heterozygous familial hypercholesterolaemia: a systematic review and meta-analysis

OBJECTIVES

Heterozygous familial hypercholesterolaemia (FH) confers a significant risk for premature cardiovascular disease (CVD). However, the estimated prevalence of FH varies substantially among studies. We aimed to provide a summary estimate of FH prevalence in the general population and assess variations in frequency across different sociodemographic characteristics.

SETTING, PARTICIPANTS AND OUTCOME MEASURES

We searched MEDLINE, EMBASE, Global Health, the Cochrane Library, PsycINFO and PubMed for peer-reviewed literature using validated strategies. Results were limited to studies published in English between January 1990 and January 2017. Studies were eligible if they determined FH prevalence using clinical criteria or DNA-based analyses. We determined a pooled point prevalence of FH in adults and children and assessed the variation of the pooled frequency by age, sex, geographical location, diagnostic method, study quality and year of publication. Estimates were pooled using random-effects meta-analysis. Differences by study-level characteristics were investigated through subgroups, meta-regression and sensitivity analyses.

RESULTS

The pooled prevalence of FH from 19 studies including 2 458 456 unique individuals was 0.40% (95% CI 0.29% to 0.52%) which corresponds to a frequency of 1 in 250 individuals. FH prevalence was found to vary by age and geographical location but not by any other covariates. Results were consistent in sensitivity analyses.

CONCLUSIONS

Our systematic review suggests that FH is a common disorder, affecting 1 in 250 individuals. These findings underscore the need for early detection and management to decrease CVD risk.

Novel Therapies for Familial Hypercholesterolemia

OPINION STATEMENT

Both HeFH and HoFH require dietary and lifestyle modification. Pharmacotherapy of adult HeFH patients is largely driven by the American Heart Association (AHA) algorithm. A high-potency statin is started initially with a goal low-density lipoprotein cholesterol (LDL-C) reduction of >50 %. The LDL-C target is adjusted to <100 or <70 mg/dL in subjects with coronary artery disease (CAD) with ezetimibe being second line. If necessary, a third adjunctive therapy, such as a PSCK9 inhibitor (not yet approved in children) or bile acid-binding resin, can be added. Finally, LDL-C apheresis can be considered in patients with LDL-C >300 mg/dL (or >200 mg/dL with significant CAD, although now approved for LDL-C as low as 160 mg/dL with CAD). Due to the early, severe LDL-C elevation in HoFH patients, concerning natural history, rarity of the condition, and nuances of treatment, all HoFH patients should be treated at a pediatric or adult center with HoFH experience. LDL-C apheresis should be considered as early as 5 years of age. However, apheresis availability and tolerability is limited and pharmacotherapy is required. Generally, the AHA algorithm with reference to the European Atherosclerosis Society Consensus Panel recommendations is reasonable with all patients initiated on high-dose, high-potency statin, ezetimibe, and bile acid-binding resins. In most, additional LDL-C lowering is required with PCSK9 inhibitors and/or lomitapide or mipomersen. Liver transplantation can also be considered at experienced centers as a last resort.

Hypercholesterolemia and atherosclerosis in low density lipoprotein receptor mutant rats

To establish low density lipoprotein receptor (LDLR) mutant rats as a hypercholesterolemia and atherosclerosis model, we screened the rat LDLR gene for mutations using an N-ethyl-N-nitrosourea mutagenesis archive of rat gene data, and identified five mutations in its introns and one missense mutation (478T>A) in exon 4. The C160S mutation was located in the ligand binding domain of LDLR and was revealed to be equivalent to mutations (C160Y/G) identified in human familial hypercholesterolemia (FH) patients. The wild type, heterozygous, and homozygous mutant rats were fed a normal chow diet or a high fat high cholesterol (HFHC) diet from the age of 10 weeks for 16 weeks. The LDLR homozygous mutants fed the normal chow diet showed higher levels of plasma total cholesterol and LDL cholesterol than the wild type rats. When fed the HFHC diet, the homozygous mutant rats exhibited severe hyperlipidemia and significant lipid deposition from the aortic arch to the abdominal aorta as well as in the aortic valves. Furthermore, the female homozygous mutants also developed xanthomatosis in their paws. In conclusion, we suggest that LDLR mutant rats are a useful novel animal model of hypercholesterolemia and atherosclerosis.

Molecular characterization of Iranian patients with possible familial hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder of lipoprotein metabolism caused mainly by mutations in the low-density lipoprotein receptor (LDLR) and apolipoprotein B 100 (APOB) genes. Until now, the molecular basis of FH has been demonstrated in detail in many populations, but there is still very limited Molecular data concerning FH in Iran. The aim of this study was to characterize the LDLR and APOB gene mutations in an Iranian population. A total of 30 non-related Iranian possible FH subjects were studied. Diagnosis of FH was based on the Dutch Lipid Clinic Network diagnostic criteria. All samples were initially tested for three common APOB gene mutations including R3500Q, R3500 W and R3531C using PCR-RFLP assay. Subsequently, promoter and coding region of the LDLR gene was screened by PCR-SSCP analysis and positive results were confirmed by DNA sequencing. Four previously reported polymorphisms 1413G > A, 1725C > T, 1773T > C and 2140 + 5G > A were found in ~17% (5/30) of population studied. Moreover, no variation was found in APOB gene. Our data indicated that LDLR and APOB gene mutations have not contribution to possible FH in Iranian population studied here. However, we examined three common APOB mutations and LDLR in only 30 patients, and to determine the role of these genes in developing FH in Iran, more FH samples and populations needed to be investigated for the mutations of the related genes.

Molecular genetic analysis of familial hypercholesterolemia: spectrum and regional difference of LDL receptor gene mutations in Japanese population

To determine the molecular basis of familial hypercholesterolemia (FH) in Japan, 200 unrelated patients with clinically diagnosed heterozygous FH were screened for mutations in coding and promoter region of the low density lipoprotein (LDL) receptor gene using denaturing gradient-gel electrophoresis (DGGE), DNA sequencing and Southern blotting analysis. About 37 different mutations in the LDL receptor gene were identified in 125 (62.5%) of the patients, 22 of these mutations have not been described before. The most common mutations were K790X (19.5%), P664L (6.0%), FH-Tonami-1 (6.0%), IVS15-3C>A (5.5%) and FH-Tonami-2 (4.5%), whereas the other mutations were rare. No apolipoprotein B (apoB) mutations responsible for familial ligand-defective apoB-100 (FDB) were identified. Polymorphisms of apolipoprotein E (apoE) and scavenger receptor class B type I (SR-BI) were observed to have minor effects on the lipid and lipoprotein profile. In 75 (32.5%) of the FH patients, LDL receptor gene mutations could not be identified. These patients had significantly lower total cholesterol (7.71+/-1.64 vs. 8.68+/-1.47 mmol/l, P<0.001) and LDL-cholesterol (6.02+/-1.51 vs. 6.87+/-1.47 mmol/l, P<0.001) in plasma, also a lower incidence of coronary heart disease (CHD) (22 vs. 29%, P=0.05) compared with patients with a LDL receptor gene mutation, suggesting that besides LDL receptor, defect of other genes involved in LDL metabolism may be a cause of FH with a milder phenotypic expression in Japanese population.

[Heterozygous familial hypercholesterolemia in Spain. Description of 819 non related cases]

BACKGROUND

Heterozygous familial hypercholesterolemia (hFH) is an inherited disorder commonly found among the general population. Premature cardiovascular disease, especially coronary artery disease, is the most important complication in these patients. The aim of this study was to analyze the clinical manifestations and the characteristics of cardiovascular disease in the Spanish hFH population.

PATIENTS AND METHOD

Analysis of 819 non-related cases (449 females and 370 males), with a clinical diagnosis of familial hypercholesterolemia, from 69 lipid clinics. Clinical and lipid profile at diagnosis along with personal and familial backgrounds related to cardiovascular disease were registered in a central database.

RESULTS

Mean total cholesterol at diagnosis was 412 (87) mg/dl in women, and 400 (78) mg/dl in men (p = 0.049). HDL-c was higher in females than in males (57 [14] vs. 47.7 [12.7] mg/dl, respectively, p < 0.0001). Xantomas were present in 22.5% of cases, and 21.7% of subjects had evidence of premature cardiovascular disease which was more frequent in males than in females (30.8% and 14.3%, respectively; p < 0.001). In a multivariant analysis, a significant and positive correlation was observed between cardiovascular disease and age, gender, tobacco consumption, LDL-c levels, blood pressure and body mass index.

CONCLUSIONS

The clinical manifestations and the presence of cardiovascular disease in Spanish hFH patients are similar to those described in other populations. LDL-c levels, age, gender, smoking, hypertension and body mass index are important predictors of cardiovascular disease in these patients.

Positive family history for coronary heart disease and 'midband lipoproteins' are potential risk factors of carotid atherosclerosis in familial hypercholesterolemia

Patients with heterozygous familial hypercholesterolemia (FH) were examined with B-mode ultrasound in order to determine intima-media thickness (IMT) in the common carotid artery, and to uncover potential risk factors responsible for the development of IMT. Ninety seven FH subjects and 132 non FH type IIa hyperlipidemic subjects were involved in the present study. Age was found to correlate positively with IMT in both FH and non FH groups. FH individuals showed a higher IMT, along with elevated low density lipoprotein (LDL) cholesterol levels, compared with age-matched non FH individuals. To clarify potential factors contributing to the formation and development of carotid atherosclerosis, we divided the FH subjects into two subgroups, namely FH with high IMT group (HIG), and those with low IMT group (LIG). We investigated those two subgroups on the presence of angiographically documented coronary heart disease (CHD), of family history of CHD and of 'midband lipoproteins' by polyacrylamide gel electrophoresis (PAGE) analysis, by matching for age and LDL-cholesterol (LDL-C) level. Fifty percent of FH men in HIG was found to have CHD, whereas only 14% of those in LIG had CHD (P<0.05). Thirty-three percent of FH women in HIG was found to have CHD, whereas only 12% of those in LIG had CHD (P<0.05). Fifty percent of FH men in HIG was found to have 'midband lipoproteins', whereas only 7% of those in LIG had 'midband lipoproteins' (P<0.01). Seventy-three percent of FH women in HIG had 'midband lipoproteins', whereas only 21% of those in LIG had 'midband lipoproteins' (P<0.0005). Fifty-five percent of FH men in HIG was had positive family history for CHD, whereas only 14% of those in LIG had positive family history for CHD (P<0.05). Sixty-three percent of FH women in HIG was found to have positive family history for CHD, whereas only 29% of those in LIG had positive family history for CHD (P<0.05). Based on these findings, we propose that, besides age and elevated levels of LDL-C, positive family history for CHD and 'midband lipoproteins' are important determinants for the development of carotid atherosclerosis in FH individuals in Japanese population.

Common mutations in the low-density-lipoprotein-receptor gene causing familial hypercholesterolemia in the Japanese population

Familial hypercholesterolemia (FH) is a common genetic disorder caused by mutations of the LDL-receptor gene. In the present study, we investigated four Japanese FH homozygotes and identified five point mutations: a splice site mutation in intron 12 (the 1845 + 2 T-->C mutation), a missense mutation in exon 7 (the C317S mutation), a nonsense mutation in exon 17 (the K790X mutation), a missense mutation in exon 14 (the P664L mutation), and a missense mutation in exon 4 (the E119K mutation). We developed simple methods for detecting these mutations. When we examined the presence of these mutations in 24 unrelated FH homozygotes, the 1845 + 2 T-->C mutation was found in 7 of them, and the other four mutations were unique for each proband. We also screened 120 unrelated FH heterozygotes for these mutations and found that the frequencies of the 1845 + 2 T-->C, C317S, K790X, P664L, and E119K mutations were 13.3% (16/120), 6.7% (8/120), 6.7% (8/120), 3.3% (4/120), and 1.7% (2/120), respectively. These mutations were found in more than 30% of unrelated Japanese FH patients. By using the detection methods developed in this study, the diagnosis of more than 30% of the genetic bases of Japanese FH heterozygotes is expected.

Cost-effectiveness considerations in the treatment of heterozygous familial hypercholesterolemia with medications

When used for the primary prevention of coronary heart disease in persons with heterozygous familial hypercholesterolemia (hFH), a hydroxymethylglutaryl coenzyme A (HMG CoA) reductase inhibitor is projected to be effective and to have very favorable cost-effectiveness ratios at low-to-medium doses. For example, 20 mg of lovastatin per day is estimated to save lives and save money in all men ages 35-44 years with hFH and in women ages 35-44 years with hFH and any other risk factor. The estimated incremental cost effectiveness of 40 mg compared with 20 mg of lovastatin for individuals with hFH ages 35-44 years was less than $45,000 per year of life saved in men with > or = 1 other risk factors and women with > or = 2 other risk factors. The estimated incremental cost-effectiveness ratio of 80 mg compared with 40 mg/day was substantially higher ($100,000 or more per year of life saved) even in the highest risk persons. The estimated cost-effectiveness ratios for primary prevention in hFH were reasonably similar to the favorable ratios for secondary prevention in the general population but substantially better than the estimated ratios for primary prevention in other adults with high cholesterol levels. Any national recommendations regarding the use of medications for individuals with hFH must include cost considerations. Our analyses support the use of low-to-moderate doses of high-cost medications for primary prevention in these patients.

Genetic and environmental factors affecting the incidence of coronary artery disease in heterozygous familial hypercholesterolemia

This study explores the influence of selected genetic and environmental factors on the clinical expression of heterozygous familial hypercholesterolemia (FH). A detailed examination of the physical and biochemical features of FH was performed in a large cohort of 208 females and 156 males. Females with FH had higher levels of total, low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol when compared with males, although the concentration of HDL cholesterol was significantly lower for both sexes when compared with normals. The reported incidence of coronary artery disease (CAD) was 31% for men and 13% for women, which was lower when compared with figures from previous studies. The average age of onset of coronary symptoms was delayed in females, with a mean age of 55 years compared with 48 years for males (p less than 0.05). A greater risk of developing CAD in men was associated with lower levels of HDL cholesterol and a history of smoking. In women, however, CAD was associated with elevated triglycerides and the presence of hypertension. The frequencies of the epsilon 2, epsilon 3, and epsilon 4 alleles of apolipoprotein E in 125 unrelated FH subjects did not differ significantly from the normal population. In addition, there was no apparent relation between apo E4 and the concentration of any of the parameters in the plasma lipid profile; however, the presence of the E2 isoform was associated with significantly elevated triglycerides in both sexes. This study has allowed us to identify those factors, which, in addition to total cholesterol levels, are associated with the development of premature coronary atherosclerosis in heterozygous FH.

Familial hypercholesterolemia and apolipoprotein E4

The purpose of this study was to elucidate the relationship between two genetic factors associated with raised blood cholesterol, i.e. familial hypercholesterolemia (FH) and apolipoprotein (apo) E4. A group of 50 unrelated heterozygous FH patients aged 33-71 years were studied together with 129 normolipidemic subjects. A significantly higher frequency of apo E4 phenotypes was found in FH patients (30.0%) than in normolipidemic subjects (15.5%). FH patients were divided into two groups with and without apo E4. Plasma total cholesterol (Chol) and triglyceride (TG) levels were significantly higher, and plasma low density lipoprotein-cholesterol (LDL-Chol) level tended to be higher in FH patients with apo E4 than in those without apo E4. In addition, the prevalence of ischemic heart disease (IHD) was significantly higher in FH patients with apo E4 (73.3%) than in those without apo E4 (31.4%). No significant difference was noted in age and in the prevalence of obesity, diabetes, hypertension and smoking between the FH groups with and without apo E4. These results suggest that apo E4 is associated with higher levels of total Chol and TG and, at least in part, contributes to the predisposition to IHD in FH.

Coronary angiographic characteristics in Japanese patients with heterozygous familial hypercholesterolemia

Coronary angiographic findings were analyzed in 51 consecutive patients (36 males and 15 females) with heterozygous familial hypercholesterolemia (FH) and 279 consecutive patients (216 males and 63 females) without FH (non-FH). The coronary stenosis index and over 75% stenosis vessel subset were almost three times as high in the FH group. The incidence of myocardial infarction was almost twice as high in the FH group. Levels of total cholesterol and its lipoprotein fractions, except HDL-cholesterol, were almost twice as high in the FH group. In the FH group aged under 50 years, the two parameters of coronary angiogram and the incidence of myocardial infarction were significantly higher in males than in females. However, in the group aged over 50 years, all three parameters were not significantly different between those in males and females. The level of HDL-cholesterol was significantly lower in males than in females. A significantly higher incidence (18%) of coronary ectasia was observed in the FH group compared with the incidence (2%) in non-FH. All patients with coronary ectasia were males, except one female with FH. On comparison of the males among the FH patients with those among the non-FH patients matched for total cholesterol, age and other risk factors, the FH patients were associated with a significantly higher degree of coronary atherosclerosis and lower level of HDL-cholesterol. Seven FH patients with a normal coronary angiogram were observed. However, any factors as regards age, total cholesterol, HDL-cholesterol and Achilles tendon thickness failed to distinguish between the FH patients with a normal coronary angiogram and those without.(ABSTRACT TRUNCATED AT 250 WORDS)

A case of heterozygous familial hypercholesterolemia associated with hyperthyroidism: effects of triiodothyronine on low-density lipoprotein receptor and cholesterol synthesis

A 58-year-old patient with heterozygous familial hypercholesterolemia (FH) showed normal levels of serum cholesterol (193 mg/dL) in coexistence with hyperthyroidism. After hyperthyroidism therapy with radioiodine and methimazole, the patient's lipid profile showed high concentrations of cholesterol (whole serum 318 mg/dL, VLDL 35 mg/dL, LDL 217 mg/dL, HDL 44 mg/dL). There was a significant inverse correlation between serum cholesterol levels and serum thyroxine levels (r = -0.815, p less than 0.01). Effects of triiodothyronine on LDL degradation and cholesterol synthesis from 14C-labeled acetate were studied in cultured skin fibroblasts. Triiodothyronine (T3) stimulated both LDL degradation and cholesterol synthesis in the cells from normal subjects and patients with heterozygous FH. The T3 increased cellular cholesterol synthesis markedly in the cells from patients with homozygous FH but did not increase LDL receptor activity. These results suggest that normal serum cholesterol levels in our case result in part from an enhancement of LDL receptors by thyroid hormone.

The assessment of Achilles tendon size in primary hypercholesterolaemia by computed tomography

The Achilles tendons of 43 men and women were examined by conventional radiography and by computed tomography (CT). Eleven subjects were normolipidaemic and 32 had familial hypercholesterolaemia, of whom 19 were considered to have polygenic hypercholesterolaemia and 13 monogenic. Achilles tendon xanthomata were identifiable by both radiography and CT. In assessing the size of xanthomata, CT had advantages since the junction between muscle and tendon was easily identified and all the dimensions and the cross-sectional area of the tendon could be measured. The area of Achilles tendons was closely correlated with body height in normolipidaemic men and women and patients with polygenic hypercholesterolaemia. In monogenic hypercholesterolaemia this relationship was lost. The tendons of the normolipidaemic group and of patients with polygenic hypercholesterolaemia were indistinguishable, whereas those of patients with monogenic hypercholesterolaemia were significantly larger. Neither the maximum nor the average CT attenuation values of the tendons differed significantly between the 3 groups. Of the patients with monogenic hypercholesterolaemia, those whose Achilles tendons were less than 200 mm2 in area had received treatment longer than those with larger tendons. CT shows promise as a means of assessing the therapeutic response of patients with monogenic familial hypercholesterolaemia.

Effects of ML-236b (compactin) on sterol synthesis and low density lipoprotein receptor activities in fibroblasts of patients with homozygous familial hypercholesterolemia

We studied biochemical genetics of low density lipoprotein (LDL) receptor mutations in fibroblasts from six homozygous and five heterozygous patients with familial hypercholesterolemia (FH). Three of six homozygotes are receptor-negative type and the other three homozygotes are receptor-defective type. In the cells from three receptor-negative homozygotes, the receptor binding, internalization, and degradation of (125)I-LDL were 0.5+/-0.3 ng/mg protein (mean+/-SEM), 14+/-8 and 8+/-6 ng/mg protein per 6 h (four normal cells; 44+/-3, 386+/-32, and 1,335+/-214 ng/mg protein per 6 h), respectively. In the cells from three receptor-defective homozygotes, the receptor binding, internalization, and degradation of (125)I-LDL were 6+/-2, 29+/-8, and 90+/-32 ng/mg protein per 6 h, respectively. In these six homozygotes, two pairs of siblings are included. Two siblings in the same family were classified as receptor-negative and two siblings in another family were classified as receptor-defective. The receptor-negative phenotypes and the receptor-defective phenotypes bred true in individual families. The cells from five heterozygotes showed approximately 46% of the normal activities of receptor.ML-236B, competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), completely inhibited the incorporation of [(14)C]acetate into digitonin-precipitable sterols in fibroblasts from normal subjects and heterozygous and homozygous patients with FH with the concentration of 0.5 mug/ml. However, at 0.05 mug/ml of ML-236B sterol synthesis in fibroblasts from homozygotes was not completely suppressed in contrast to normal and heterozygous cells. Moreover, after preincubation with 0.05 mug/ml of ML-236B for 24 h in medium containing lipoproteins, sterol synthesis in the cells from receptor-negative homozygote showed 75% of the initial activity compared with that of 25% without preincubation. In the cells from a normal subject and a heterozygote, sterol synthesis was inhibited even after preincubation. These results suggest that (a) the inhibitory effect of ML-236B is overcome in homozygote cells by their high intracellular levels of HMG-CoA reductase and (b) that a higher dose of ML-236B may be required to lower serum cholesterol levels in FH homozygotes than in heterozygotes.

Serum lipids, lipoprotein lipids and coronary heart disease in patients with xanthelasma palpebrarum

Serum lipids and lipoprotein lipids were studied in 53 patients (21 males and 32 females) with xanthelasma palpebrarum and 40 age-matched normal controls (20 males and 20 females). Patients were subdivided into patients with normolipidemia, hyperlipidemia or familial hypercholesterolemia (FH). In both male and female patients with hyperlipidemia or FH, the serum cholesterol (Chol) levels were significantly higher than in normal controls. In both male and female patients with normolipidemia or hyperlipidemia, the VLDL-Chol levels were significantly higher than in normal controls. Male patients with FH showed significantly higher levels of VLDL-Chol than normal controls. Both male and female patients with normolipidemia, hyperlipidemia or FH showed significantly higher levels of LDL-Chol, lower HDL-Chol levels and lower HDL-Chol/LDL-Chol ratios than normal controls. In both male and female patients with hyperlipidemia and in male patients with FH, the serum triglyceride (TG) levels were significantly higher than in normal controls. Both male and female hyperlipidemic patients showed significantly higher levels of VLDL-TG than normal controls. In male patients with FH, the VLDL-TG levels were significantly above the control levels. In male patients with normolipidermia, the LDL-TG levels were significantly higher than in normal controls. In both male and female patients with hyperlipidemia or FH, the LDL-TG levels were significantly higher than in normal controls. The HDL-TG levels in patients with normolipidemia (males) or FH (females) were significantly lower than in normal controls. The prevalence of coronary heart disease in patients with normolipidemia, hyperlipidemia or FH was 29.4%, 24.0% and 45.4%, respectively.

Effects of lipoproteins on plasma viscosity

Patients with hypertriglyceridemia and mixed hyperlipidemia have been found to have mean plasma viscosities significantly higher than controls (P less than 0.005). In a group of 70 hyperlipidemic patients and controls, plasma viscosity was correlated with plasma triglyceride concentration (r = 0.56, P less than 0.01) and to a lesser extent with the concentration of plasma cholesterol (r = 0.29, P less than 0.05). When isolated lipoprotein fractions were added to lipoprotein-free plasma in increasing concentration over a physiological range, a highly significant linear relationship between plasma viscosity and chylomicron concentrations (r = 0.98, P less than 0.001) was apparent. Furthermore, when chylomicrons were removed by ultracentrifugation, viscosity returned to baseline levels. Added VLDL produced a lesser effect (r = 0.70, P less than 0.001) and added LDL, over the range of cholesterol concentration studied, had no influence on viscosity. These studies indicate that chylomicrons in particular can increase plasma viscosity. Viscosity increases of the magnitude demonstrated may in turn alter blood flow and thus contribute to symptoms such as intermittent claudication. Chylomicron-induced increases in plasma viscosity and subsequent decreases in local pancreatic blood flow may be one of the factors involved in the known relationship between severe chylomicronemia and acute pancreatitis.