Madeleine Roy

ECOGENETICS OF PARKINSON'S DISEASE: 4-HYDROXYLATION OF DEBRISOQUINE

It is postulated that Parkinsons disease is the result of environmental factors acting on genetically susceptible individuals against a background of normal ageing. Many potentially neurotoxic xenobiotics are detoxified by hepatic cytochrome P450. The function of one such system was studied in forty patients with Parkinsons disease and forty normal control subjects. Significantly more parkinsonian than control subjects had partially or totally defective 4-hydroxylation of debrisoquine. Poor metabolisers of debrisoquine tended to have had earlier onset of disease.

Mutations of low-density-lipoprotein-receptor gene, variation in plasma cholesterol, and expression of coronary heart disease in homozygous familial hypercholesterolaemia

Variation in plasma-cholesterol concentration and the expression of coronary heart disease in patients with homozygous familial hypercholesterolaemia (FH) is well documented, but the underlying reasons for variation are not clearly defined. Because FH is caused by mutations at the low-density-lipoprotein-gene locus, we compared plasma-cholesterol concentrations in 21 FH homozygotes with either the greater than 10 kb deletion (promoter region and exon 1) (11 subjects) or the exon 3 missense (trp66-->gly) mutation (10 subjects) of the low-density-lipoprotein gene. Subjects with the greater than 10 kb deletion had a higher mean plasma-cholesterol concentration than those with the exon 3 mutations (26.7 vs 16.1 mmol/L; p = 0.000006), and there was no overlap in individual plasma-cholesterol concentrations between subjects in the two groups. Although the frequency of coronary heart disease was similar in the two groups, age-of-onset was earlier in subjects with the greater than 10 kb deletion (p = 0.059). Also, coronary deaths were more frequent (p = 0.044) and occurred at an earlier age (p = 0.009) in subjects with the greater than 10 kb deletion. Our results provide evidence that there is less variation in plasma-cholesterol concentrations among FH homozygotes when they are subdivided into groups according to low-density-lipoprotein-receptor-gene defect. Furthermore, differences in plasma-cholesterol concentrations are reflected in the severity of coronary heart disease expression.

Ecogenetics of Parkinson's disease: prevalence and environmental aspects in rural areas

We make use of the unique combination of a homogeneous genetic and racial origin in the rural population of Quebec and the facilities of free and universal access to medical care, to study the distribution of the prevalence of Parkinsons disease in the 9 rural hydrographic regions of the Province. Through 3 different methods of ascertainment, confirmed by two control probes, we demonstrate that the prevalence of Parkinsons disease is of uneven distribution within rural areas. We further investigated the characteristics of the regions of high prevalence. These regions which are predominantly agricultural and areas of intensive market gardening were also the areas with the highest use of pesticides.

Plasma Concentration of Apolipoprotein E in Intermediate-Sized Remnant-Like Lipoproteins in Normolipidemic and Hyperlipidemic Subjects

Triglyceride-rich lipoprotein (TRL) remnants have been strongly implicated in the pathogenesis of atherosclerosis. To further investigate plasma remnant lipoprotein metabolism, we have determined the plasma concentration of apolipoprotein (apo) E (by polyclonal enzyme-linked immunoassay) in remnant-like lipoproteins, isolated by automated gel filtration chromatography as a fraction intermediate in size between VLDL and HDL. In normolipidemic subjects (n = 12), 1.2 +/- 0.11 mg/dL (33 +/- 2%, mean +/- SE) of total plasma apoE was associated with this fraction (termed ISL apoE). In hypercholesterolemic (type IIa, n = 12), hypertriglyceridemic (type IV, n = 12), and mixed hyperlipidemic (type IIb, n = 12) subjects, mean ISL apoE concentrations were 2.1 +/- 0.2, 2.5 +/- 0.2, and 3.8 +/- 0.4 mg/dL, respectively (P < .001 versus normal values) (45 +/- 2%, 32 +/- 2%, and 44 +/- 2% of total). ISL apoE was 8.7 +/- 1.4 mg/dL (42 +/- 3%) in type III dyslipidemic subjects (apoE2/2, n = 8). ISL apoE was positively correlated with plasma triglyceride (r = .41, P < .01), and at any given level of plasma triglyceride, subjects with an apoE2/2 or apoE3/2 phenotype tended to have a higher concentration of ISL apoE (P < .01) than apoE3/3 or E4/3 individuals. ISL apoE was also correlated (P < .001) with total plasma cholesterol (r = .66), TRL cholesterol (r = .49), TRL apoE (r = .47), LDL apoB (r = .42), and LDL+HDL triglyceride (r = .74). These results suggest that (1) a significant proportion of plasma apoE resides within an intermediate-sized remnant-like lipoprotein fraction in both normolipidemic and hyperlipidemic subjects; (2) plasma remnant lipoprotein accumulation is associated with an elevation in ISL apoE concentration; and (3) ISL apoE concentration is significantly correlated with various proatherogenic lipid parameters and may itself be a potentially important atherogenic index.

Identification of a second "French Canadian" LDL receptor gene deletion and development of a rapid method to detect both deletions.

Hobbs et al. (N. Engl. J. Med. 317: 734–737, 1987) reported a large deletion of approximately 10 kilobases in the 5′ portion of the human low‐density lipoprotein (LDL) receptor gene. This deletion affects about 60% of familial hypercholesterolemia (FH) heterozygotes in the French Canadian population. We have developed a rapid, convenient method for the detection of the deletion using double digestion with the restriction enzymes Xbal and EcoRV, or triple digestion with Xbal, EcoRV and XmnI, and a 650 bp cDNA probe, radio‐labeled using a random oligonucleotide primer technique. Eighty French Canadian FH heterozygotes were screened for the presence of the deletion. Forty‐seven (59%) of them were found to carry the 10 kb deletion. Using the same method, we also identified a new mutation which was found in four of the 80 (5%) FH patients. This mutation has been found to be a 5 kb deletion removing exons 2 and 3 of the LDL receptor gene, which correspond to the first two repeats of the LDL receptor binding domain. Cosegregation of the 5 kb deletion and the FH phenotype was observed in one family. Possible structure‐function relationship is discussed.

Apolipoprotein E polymorphism and heterozygous familial hypercholesterolemia. Sex-specific effects.

The impact of apolipoprotein (apo) E polymorphism on interindividual variation in plasma lipid, lipoprotein, and apolipoprotein levels was studied in a sample of familial hypercholesterolemic (FH) patients (147 women, 116 men) with the same mutation, a > 10-kilobase deletion of the low-density lipoprotein (LDL) receptor gene. Each trait was adjusted for concomitants (age, age squared, height, weight, weight squared) for each sex separately before the apoE genotypic effects were estimated. The relative contribution of concomitants to sample variability was found to be very different in women and in men. Allelic variation in the apoE gene was shown to explain a statistically significant portion of the variability in adjusted lipid traits. Moreover, the contribution of apoE polymorphism was different between sexes. In women, there was significant variability (P < .01) among apoE genotypes for total cholesterol, LDL cholesterol, and total and LDL apoB. In men, significant variability (P < .01) was observed among apoE genotypes in very-low-density lipoprotein (VLDL) cholesterol and triglyceride levels. Women with the epsilon 3/2 genotype had significantly lower means for total cholesterol, LDL cholesterol, and LDL apoB than women with the epsilon 3/3 genotype (P < .05). In men, the mean VLDL cholesterol was significantly higher for the epsilon 2/2 genotype and was significantly lower for the epsilon 4/2 genotype than the mean for the epsilon 3/3 genotype (P < .05). Overall, the greatest influence was associated with the epsilon 2 allele, and the LDL cholesterol-lowering effect of this allele was present only in FH women. No statistically significant apoE effect was shown on lipoprotein(a) levels in either sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular genetic evidence for a founder effect in familial hypercholesterolemia among French Canadians

SummaryFamilial hypercholesterolemia (FH), at a prevalence of about 1 in 200 in the French-Canadian population, is caused by a 10-kb deletion in the low-density lipoprotein (LDL) receptor gene in 60% of French-Canadian FH heterozygotes. We genotyped 159 FH patients who carry this common mutation and 221 healthy French-Canadian controls for five DNA restriction fragment length polymorphisms (RFLPs) of the LDL receptor gene. The allele numbers for four of the five RFLPs differed significantly (P < 0.001) between FH patients and control subjects. Our results suggest that the 10-kb deletion carrier allele is associated with a single haplotype (called the B haplotype). In a family study including a patient homozygous for the 10-kb deletion, we showed that the B haplotype cosegregates with the deletion in affected members and that the B haplotype is also associated with the normal allele in some members of the family. We identified 15 different haplotypes for the normal allele in 10-kb deletion carrier FH heterozygotes. These results offer strong support, at a molecular level, for the hypothesis of a founder effect for the 10-kb deletion in the French-Canadian population.

Apolipoprotein E polymorphism association with lipoprotein profile in endogenous hypertriglyceridemia and familial hypercholesterolemia.

Apolipoprotein (apo) E polymorphism was among the first-reported genetic polymorphisms that explained part of the normal variation in plasma cholesterol concentrations in humans. The aim of this study was to assess the influence of allelic variation at the apo E gene locus on the plasma lipoprotein profile in hyperlipidemia. The lipoprotein levels of hyperlipidemic subjects of the major apo E phenotypes (E3/2, E3/3, and E4/3) were compared. One hundred eighty-two subjects with endogenous hypertriglyceridemia and 98 subjects with familial hypercholesterolemia due to a 10-kb deletion in their low density lipoprotein (LDL) receptor genes were compared with 424 normolipidemic controls from the same environmental background. LDL concentrations were lower in the E3/2 subset than in the E3/3 or E4/3 subset in the control, hypertriglyceridemic, and familial hypercholesterolemic groups. In absolute values, the magnitude of the effect was greatest in the familial hypercholesterolemic group. However, the direction and percentage change were identical in the presence or absence of the LDL receptor defect, indicating that the apo E phenotype effect is independent of LDL receptor status. Triglyceride and very low density lipoprotein (VLDL) cholesterol concentrations were higher in E3/2 than in E3/3 or E4/3 hypertriglyceridemic subjects, but this difference was not found in the familial hypercholesterolemic or control group. Thus, there seems to be a specific interaction between apo E isoforms and VLDL metabolism in hypertriglyceridemia; allelic variation at the apo E gene locus seems to be associated with specific alterations in the plasma lipoprotein profile of subjects with well-defined types of hyperlipidemia.

Six‐year results of treatment with levodopa plus benzerazide in Parkinson's disease

Benzerazide (Ro 4-4602), was studied over a 75-month period of observation in 132 patients with Parkinsons disease. The combined therapeutic approach was without biological toxicity, was well tolerated by 95 percent of patients, and was highly effective: 72 percent of patients improved by more than 50 percent on a functional activity scale and the group as a whole improved on an objective battery by a mean of 46 percent. Neurologic side effects of abnormal involuntary movements, falls, and oscillations in performance were not improved over levodopa used alone. The combined therapy is to be preferred over the use of levodopa alone in the symptomatic management of Parkinsons disease.

Lp(a) Levels and Atherosclerotic Vascular Disease in a Sample of Patients With Familial Hypercholesterolemia Sharing the Same Gene Defect

There is considerable variation in the severity of cardiovascular disease among patients with familial hypercholesterolemia (FH). Some reports have suggested that plasma lipoprotein(a) [Lp(a)] levels may explain such variation and that FH subjects deficient in LDL receptors, especially those with coronary heart disease, tend to have elevated Lp(a) levels. We have investigated the possible role of the LDL receptor in determining plasma Lp(a) levels in genetically homogeneous FH population and the contribution of Lp(a) to cardiovascular risk. A total of 98 FH subjects and 66 healthy first- and second-degree relatives from 30 families with FH due to the French-Canadian > 10-kilobase deletion of the LDL receptor gene were studied. A reference group of 392 normolipidemic French-Canadian participants in a Heart Health Survey was used for comparison. FH subjects were subdivided into subsets of 63 individuals free from atherosclerotic vascular disease (AVD) and 35 individuals with AVD. A complete cardiovascular evaluation was performed, and plasma lipid, lipoprotein, and Lp(a) levels were measured in all subjects in the absence of medication. Apolipoprotein (a) [apo(a)] phenotype was determined in 112 of FH and non-FH subjects. The log-transformed values for plasma Lp(a) were not significantly different among the three groups: 0.98 +/- 0.54 (mean +/- SD) in FH subjects with AVD, 0.89 +/- 0.51 in FH subjects without AVD, and 0.82 +/- 0.64 in their relatives. The distribution of the apo(a) phenotypes did not differ between the FH and non-FH groups. Comparison of two age- and sex-matched subgroups of FH subjects, with and without AVD, failed to show any differences in Lp(a) level. However, mean Lp(a) log values in the reference group (n = 392) were significantly lower than values obtained for the total FH group (0.79 +/- 0.57 versus 0.92 +/- 0.52, respectively; P < .05) but were not different from those of the unaffected family members. Thus, in our sample, the LDL receptor appears not to influence plasma Lp(a) levels; rather, these levels reflect shared apo(a) genes. The cardiovascular risk in this group of subjects with FH was related to age, male sex, total and LDL cholesterol, and higher apoB but not Lp(a) levels.