Familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is a common (1 in 500) autosomal dominant group of syndromes associated with early onset coronary artery disease or sudden death in heterozygotes. Clinical signs are not universal but the family history is often a good indicator for initial screening. Prognosis without treatment is dependent on family history and the presence of other cardiovascular risk factors. Family screening is necessary but treatment of affected children is usually postponed until puberty. Treatment of adults is primarily with statins but removal of lipoproteins by apheresis is used in severe refractory cases or in patients with homozygous FH. FH is an easily diagnosed disorder with a reasonable prognosis after treatment and therefore cases should be identified and treated.     

Familial hypercholesterolaemia in Portugal

Familial hypercholesterolaemia (FH) is characterised clinically by an increased level of circulating LDL cholesterol that leads to lipid accumulation in tendons and arteries, premature atherosclerosis and increased risk of coronary heart disease (CHD). Although Portugal should have about 20,000 cases, this disease is severely under-diagnosed in our country, this being the first presentation of Portuguese data on FH. A total of 602 blood samples were collected from 184 index patients and 418 relatives from several centres throughout Portugal. Fifty-three different mutations were found in 83 index patients, 79 heterozygous and 4 with two defective LDLR alleles. Additionally, 4 putative alterations were found in 8 patients but were not considered mutations causing disease, mainly because they did not co-segregate with hypercholesterolaemia in the families. Three unrelated patients were found to be heterozygous for the APOB(3500) mutation and two unrelated patients were found to be heterozygous for a novel mutation in PCSK9, predicted to cause a single amino acid substitution, D374H. Cascade screening increased the number of FH patients identified genetically to 204. The newly identified FH patients are now receiving counselling and treatment based on the genetic diagnosis. The early identification of FH patients can increase their life expectancy and quality of life by preventing the development of premature CHD if patients receive appropriate pharmacological treatment.     

Role of iron and glutathione redox cycle in acetaminophen-induced cytotoxicity to cultured rat hepatocytes

The aims of this study were to investigate the roles of iron as a catalyst in reactive oxygen metabolite-mediated cellular injury and of the endogenous antioxidant defenses against acetaminophen-induced cytotoxicity in cultured rat hepatocytes. Hepatocytes were isolated and cultured from either 3-methylcholanthrene-treated or untreated rats. Cytotoxicity was evaluated by measuring⁵¹Cr and lactate dehydrogenase release. Acetaminophen caused dose-dependent cytotoxicity in 3-methlycholanthrene-treated, but not untreated, cells. There was a good correlation between⁵¹Cr and lactate dehydrogenase release values. Pretreatment with both diethyl maleate, which covalently binds glutathione as catalyzed by glutathione-S-transferase, and bis(chloroethyl)-nitrosourea, an inhibitor of glutathione reductase, enhanced acetaminophen-induced cytotoxicity. Inhibition of endogenous catalase activity by pretreatment with aminotriazole did not affect acetaminophen-induced cellular damage. Addition of exogenous catalase failed to protect against acetaminophen-induced cytotoxicity. Preincubation with both deferoxamine, a ferric iron chelator, and phenanthroline, a ferrous iron chelator, diminished acetaminophen-induced cytotoxicity. These results indicate that iron is crucial in mediating acetaminophen-induced cytotoxicity and that the glutathione redox cycle, but not catalase, plays a critical role in the endogenous defenses against acetaminophen-induced cellular damage in cultured rat hepatocytesin vitro.This work was supported by the Medical Research Service of the Veterans Affairs.     

Peripheral atherosclerosis in familial hypercholesterolaemia

Unlike coronary artery disease, peripheral atherosclerosis is considered to be infrequent in heterozygous familial hypercholesterolaemia. The authors studied 20 consecutive asymptomatic familial hypercholesterolaemic patients and an age- and sex-matched control group of consecutive normolipidaemic and asymptomatic patients admitted to the hospital for elective non-vascular surgery. The patients and the controls were studied non-invasively by measuring the ankle-arm systolic blood pressure ratio at rest. Peripheral atherosclerosis was common in this study population in contrast to the control group: an abnormal (less than 0.97) pressure ratio was found in 13 patients (65%) in the study group but in only one person in the control group. Eight out of 20 patients had coronary artery disease, and seven of them had an asymptomatic concomitant peripheral artery disease. Neither the classical risk factors, i.e. age, smoking, obesity, hypertension and glucose intolerance, nor serum lipid or lipoprotein status or the parameters of cholesterol metabolism correlated with peripheral atherosclerosis. It is concluded that atherosclerosis in familial hypercholesterolaemia is a multilevel disease that frequently affects also the peripheral arteries.     

Amlodipine and captopril in moderate-severe essential hypertension

The therapeutic usefulness of adding once-daily amlodipine (10 mg) for four weeks in moderate-severe hypertensive patients uncontrolled on low dose captopril (25 mg twice daily) alone was studied in 29 patients in a double-blind, placebo-controlled two-way crossover comparison. Once daily amlodipine was shown to be an effective antihypertensive drug when combined with captopril. The amlodipine minus placebo differences in mean changes from captopril baseline values were: -18/-12 mmHg and -20/-12 mmHg for supine and standing systolic/diastolic pressures (P less than 0.001 for all four pressure variables). The combination was well tolerated, and no patient discontinued therapy. Five patients experienced ankle oedema and four patients reported flushing while receiving amlodipine/captopril.     

Casein-induced hypercholesterolaemia in rabbits is calcium-dependent

Young male rabbits were fed semi-purified diets containing either casein or soy protein, both at a normal (0.84%, w/w) and a high (1.44%, w/w) level of dietary calcium. At the normal calcium level, casein, as compared with soy protein, increased the concentration in serum of total and free cholesterol and the ratio of free cholesterol to phospholipid. Also, casein increased the intestinal phosphate absorption and decreased the faecal fat excretion. The hypercholesterolaemic response of the rabbits on the casein diet was significantly correlated with both phosphate absorption (r = +0.744) and fat excretion (r = -0.701). The increased amount of dietary calcium inhibited the casein-specific effects on both the intestinal and the serum lipid parameters. In contrast, calcium did not change these parameters in rabbits fed the soy protein diet. These results support the hypothesis that the degree of phosphorylation of casein is involved in the mechanism of the casein-induced hypercholesterolaemia by means of its effect on the enterohepatic cycle of bile acids.     

Metabolic studies with probucol in hypercholesterolaemia

Probucol (1 g/day) was administered for 6 months to 16 hypercholesterolaemic patients previously stabilized on diet alone. Total plasma cholesterol fell by 16%, LDL cholesterol by 14% and HDL cholesterol by 41%. The ratio of total cholesterol to HDL cholesterol increased by 40%. Total plasma triglycerides showed a slight upward trend. The extent of the fall in HDL cholesterol was directly proportional to the pre-treatment HDL cholesterol concentration. In 2 patients studied, treatment with Probucol produced a sustained increase in the excretion of endogenous faecal steroids, due to increased faecal bile acids. In 3 patients studied, Probucol increased the degree of cholesterol saturation in gall bladder bile. The Lithogenic Index approximated to pathological levels in 1 patient whose bile was previously relatively saturated with cholesterol. Probucol also appeared to cause a modest reduction in the degree of platelet activation in vivo, with reduced platelet prostaglandin synthesis and reduced release of platelet peptides.