M. Pocoví

Impact of low-density lipoprotein receptor mutational class on carotid atherosclerosis in patients with familial hypercholesterolemia

BACKGROUND AND OBJECTIVES Defects in the low-density lipoprotein receptor (LDLR) gene cause familial hypercholesterolemia (FH), a highly atherogenic condition. The effect of different LDLR mutations on coronary heart disease (CHD) risk is insufficiently defined. We assessed carotid intima-media thickness (IMT), a surrogate marker of CHD, in relation to LDLR mutational class in FH. METHODS In 436 Spanish FH patients (223 men and 213 women, age 44+/-14 years) with known LDLR mutations, alleles were classified by standard criteria as null (n=269), defective (n=162), or undetermined (n=5). LDLR defects were detected using a microarray (Lipochip) designed to uncover prevalent mutations in Spain and gene sequencing when no mutations were detected. Carotid IMT and plaque were assessed in FH patients and 268 healthy subjects. RESULTS All carotid measurements were increased in FH patients versus controls (p<0.05), irrespective of genotype. After adjustment for gender and age, patients with null alleles compared with defective alleles had similar mean and maximum common carotid artery (CCA) IMT, but higher maximum IMT at any carotid segment, with median values (95% confidence interval) of 1.25 mm (1.19-1.31) and 1.11 mm (1.05-1.18), respectively. Multivariate analysis showed that null alleles were independently associated with maximum CCA-IMT (beta=0.09, p=0.033) with an impact similar to that of gender (beta=0.10, p=0.035). CONCLUSIONS FH patients show advanced carotid atherosclerosis in relation to LDLR mutational class. The findings support the utility of genetic testing in FH beyond providing a secure diagnosis.

Association of plasma markers of cholesterol homeostasis with metabolic syndrome components. A cross-sectional study.

BACKGROUND AND AIMS Increased plasma phytosterols, which reflect enhanced cholesterol absorption, have been related to an increased risk of cardiovascular disease (CVD). However, high CVD risk conditions, such as obesity, diabetes and the metabolic syndrome (MetS) have been associated with reduced cholesterol absorption. We investigated associations between plasma noncholesterol sterols and MetS components. METHODS AND RESULTS With a cross-sectional design, we related MetS components to plasma noncholesterol sterol-to-cholesterol ratios measured by gas chromatography in 674 dyslipidemic patients and 361 healthy subjects participating in a prospective cohort study. Plasma phytosterol-to-cholesterol ratios were inversely associated with all components of the MetS. In the dyslipidemic group, multivariable analyses showed that a 1-SD increase in sitosterol-to-cholesterol ratio was associated with a reduced risk for any MetS feature, ranging from 0.57 (95% CI, 0.45 to 0.71) for visceral adiposity to 0.82 (95% CI, 0.69 to 0.98) for high blood pressure. The risk of having MetS was nearly halved, with ORs of 0.49 (95% CI, 0.38 to 0.64) or 0.56 (95% CI, 0.44-0.70), depending on the definition. Results were opposed for plasma lathosterol, a marker of cholesterol synthesis. Most findings were reproduced in the healthy cohort. ApoE genotype was unrelated to plasma noncholesterol sterols. CONCLUSION In both dyslipidemic and healthy populations, MetS is associated with increased plasma lathosterol, a cholesterol synthesis marker, and decreased plasma sitosterol, a marker of cholesterol absorption. Elevated plasma phytosterols related to a lower frequency of cardiometabolic risk factors, suggesting that they are associated with a reduced CVD risk.

FEMORAL ATHEROSCLEROSIS IN HETEROZYGOUS FAMILIAL HYPERCHOLESTEROLEMIA. INFLUENCE OF THE GENETIC DEFECT

OBJECTIVE The purpose of this study was to assess femoral atherosclerosis by ultrasound in patients with molecularly defined heterozygous familial hypercholesterolemia (FH) in comparison with matched control subjects and in relation to mutational class in the LDL receptor and apolipoprotein B (APOB) genes. METHODS AND RESULTS Femoral intima-media thickness (IMT) and plaque were evaluated in 146 FH patients carrying null alleles (n=48), defective-receptor alleles (n=62), undetermined-function alleles (n=25), or APOB defects (n=11) and in 193 healthy subjects. Twenty-three patients had coronary heart disease (CHD). The frequency of both tendon xanthomas and CHD was approximately 2-fold higher and average LDL cholesterol was 30 mg/dL higher in null-allele genotype compared with receptor-defective mutations. All femoral measurements were increased in FH patients versus controls (P<0.001), and null-allele mutations showed higher age-, sex-, and LDL cholesterol-adjusted maximum IMT than receptor-defective or APOB defects (P for trend, 0.001). By multivariate analysis, independent associations of mean IMT, a measure of early atherosclerosis, were age, LDL cholesterol, sex, and systolic blood pressure. Age, null-allele genotype, sex, and smoking explained 42% of the variability of maximum IMT, a measure of advanced atherosclerosis. CONCLUSIONS FH patients have increased femoral IMT in relation to mutational class. The findings support the usefulness of genetic testing in FH beyond securing the diagnosis.