[Blood screening of glucose and lipid disorders as coronary atherosclerosis risks factors in French adolescents 16 to 19-20 years old]. / Dépistage des anomalies sanguines glucidolipidiques à risque coronarien, de 16 à 19-20 ans. A propos d'une enquête menée chez 599 jeunes volontaires.

A screening of fasting blood glucose and lipids disorders, presumely linked to premature atherosclerosis namely affecting Coronary arteries, has been performed among 599 adolescents of both sexes with the goal of establishing the actual prevalence of these disorders in French population recruited through different areas of the country. All of them were between ages of 16 and 19-20 years old, and invited to give, in total gratuity, their blood samples to private and accreditable laboratories close to their living habitation. After 262 exclusions due to either previous screening not signaled before or present use of contraceptive pill in girls, only 202 boys and 135 girls remained eligible for such a prevalence study. Using plasma enzymatic dosages of CT, HDL C, (calculated) LDLC, TG, and blood glucose, cut off points for each of these parameters, were analysed as well as calculated international index of CT/HDLC and CT minus HDLC. But the first one index was shown the best tool for the final estimation of the frequency of lipid disorders, which requires primary prevention. Indeed, despite of a rather high frequency of overlaps of CT and LDLC respectively found at 16.3 and 22.5% for boys, and 27.3 and 27.5% for girls, the still higher increase of frequency of HDL C at 31% for boys and 28.1% for girls has shown a very significant compensation of these previous increases. In such a way as the authentic prevalence of atherogenic lipid disorders is found reduced in boys to 8.4% and in girls to 7.4% for CT/HDLC>/=4.5 ratio, and to 5.4% in boys and 5.2% in girls for CT less HDLC. A Familial Dominant Hypercholesterolemia was discovered only two times in two girls 16 years old. Other abnormal lipid profiles were rather those of Mixed H., type IV, chiefly mild Hypercholesterolemia, and some rare cases of HypoHDLemia. The only greater linked cardiovascular risk factor was direct parental C.V. heredity, round 30% among lipid disorders. Obesity remained rare, as well as Metabolic Syndrome in the present recruitment. Contraceptive pill increases significantly all lipid parameters and atherogenic index: chiefly CT minus HDLC which reaches almost the double of frequency (15%) versus that of girls without pill. But 53% of boys with proatherogenic lipid disorders are smokers, while only 10% of these dyslipidemic girls smoke.

Classical LCAT deficiency resulting from a novel homozygous dinucleotide deletion in exon 4 of the human lecithin: cholesterol acyltransferase gene causing a frameshift and stop codon at residue 144.

Lecithin: cholesterolacyltransferase (LCAT) transacylates the fatty acid at the sn-2 position of lecithin to the 3beta-OH group of cholesterol forming lysolecithin and the majority of cholesteryl ester found in plasma. LCAT participates in the reverse cholesterol transport pathway in man where it esterifies tissue-derived cholesterol following efflux from peripheral cells into HDL. Only 38 unique mutations in the human LCAT gene have been reported worldwide. Our French female proband presented with corneal opacity and no detectable plasma LCAT activity using either endogenous or exogenous assays. Her total plasma cholesterol and HDL cholesterol were low (2.34 mmol/l and 0.184 mmol/l, respectively) with a very high cholesterol/cholesteryl ester molar ratio (10.9:1). Plasma triglycerides were 0.470 mmol/l with low apo B (40.5 mg/dl), apo A-I (14.7 mg/dl), apo A-II (6.8 mg/dl) and apo E (2.1 mg/dl) levels. Plasma lipoprotein analysis by ultracentrifugation showed very low HDL concentrations and a characteristic shift of the lipoprotein profile towards larger, less dense particles. No proteinuria, renal dysfunction or signs of atherosclerosis were noted at age 45. Sequence analysis of her LCAT gene showed a novel homozygous TG-deletion at residues 138-139 that resulted in a frameshift causing the generation of a stop codon and premature termination of the LCAT protein at amino acid residue 144. Western blotting of the patient's plasma using a polyclonal IgY primary antibody against human LCAT failed to demonstrate the presence of a truncated LCAT protein. A 53 bp mismatched PCR primer was designed to generate an Fsp 1 restriction site in the wild type sequence of exon 4 where the mutation occurred. The 155 bp PCR product from the wild type allele produced a 103 bp and 52 bp fragment with Fsp 1 and no cleavage products with the mutant allele thus permitting rapid screening for this novel mutation.

Assessment of French patients with LPL deficiency for French Canadian mutations.

Mutations in the LPL gene show high levels of allelic heterogeneity between and within different populations. Complete LPL deficiency has a very high prevalence in French Canadians, where only three missense mutations account for > 97% of cases, most consistent with founder mutations introduced early in Quebec by French immigrants. In order to determine whether these mutations were present in France, 12 unrelated French families with defined LPL deficiency were investigated for the presence of the mutations found in French Canadians. Of the 24 expected alleles, six (25%) represented mutations in French Canadians (Gly188Glu four alleles, Asp250Asn and Pro207Leu one allele each). Comparison of French Canadian and French alleles identified the same haplotype in all carriers of the Gly188Glu and of the Asp250Asn, suggesting a common origin. In contrast, the Pro207Leu occurred on different haplotypes in France and Quebec, compatible with a different ancestral origin.

Compound heterozygote for both rare apolipoprotein E1 (Gly127-->Asp, Arg158-->Cys) and E3(Cys112-->Arg, Arg251-->Gly) alleles in a multigeneration pedigree with hyperlipoproteinaemia.

1. A French multigeneration pedigree with hyperlipoproteinaemia was investigated for the transmission of the rare apolipoprotein E1(Gly127-->Asp, Arg158-->Cys) variant. The proband, a 46-year-old male carrying the rare apoE1 variant, presented a severe type III hyperlipoproteinaemia like his three brothers and his sister. 2. ApoE phenotyping and genotyping showed a discrepancy in the second allele carried by the proband's wife and two of her children, thus suggesting another apoE gene mutation. Cloning and sequencing of the entire exon 4 demonstrated a point mutation at codon 251, leading to an apoE3(Cys112-->Arg, Arg251-->Gly) allele. The proband's wife was normolipaemic and heterozygous for this rare isoform and the common apoE3 protein. The rare apoE3(Cys112-->Arg, Arg251-->Gly) allele has been transmitted to her two daughters. The first, aged 19, was normolipaemic and heterozygous for this allele and the common apoE2 allele. The second, carrying both the rare isoforms apoE1(Gly127-->Asp, Arg158-->Cys) and apoE3(Cys112-->Arg, Arg251-->Gly), presented a hypertriglyceridaemia at the age of 10. 3. The exploration of apoE status associated with plasma lipid levels and lipoprotein profiles in this three-generation pedigree made it possible to describe a compound heterozygote for two mutated alleles, one mutation being located in the N-terminal domain of the apoE protein and the other arising in the C-terminal domain.

A single Ser259Arg mutation in the gene for lipoprotein lipase causes chylomicronemia in Moroccans of Berber ancestry.

Lipoprotein lipase (LPL) is the rate-limiting enzyme for the hydrolysis of triglyceride-rich lipoproteins. Numerous LPL gene mutations have been described as a cause of familial chylomicronemia in various populations. In general, allelic heterogeneity is observed in LPL deficiency in different populations. However, a founder effect has been reported in certain populations, such as French Canadians. Although familial chylomicronemia is observed in Morocco, the molecular basis for the disease remains unknown. Here, we report two unrelated Moroccan families of Berber ancestry, ascertained independently in Holland and France. In both probands, familial chylomicronemia manifested in infancy and was complicated with acute pancreatitis at age 2 years. Both probands were homozygous for a Ser259Arg mutation, which results in the absence of LPL catalytic activity both in vivo and in vitro. In heterozygous relatives, a partial decrease in plasma LPL activity was observed, sometimes associated with combined hyperlipidemia. This mutation previously unreported in other populations segregated on an identical haplotype, rarely observed in Caucasians, in both families. Therefore, LPL deficiency is a cause of familial chylomicronemia in Morocco and may result from a founder effect in patients of Berber ancestry.

Premature atherosclerosis in patients with familial chylomicronemia caused by mutations in the lipoprotein lipase gene.

BACKGROUND: Patients with lipoprotein lipase deficiency usually present with chylomicronemia in childhood. The syndrome has been considered nonatherogenic primarily because of the low levels of low-density lipoprotein (LDL) cholesterol. We prospectively evaluated patients with lipoprotein lipase deficiency for atherosclerosis. METHODS: Evidence of carotid, peripheral, and coronary atherosclerosis was sought in four patients (two men and two women) with the phenotype of familial chylomicronemia by clinical examination over a period of 14 to 30 years and by Doppler ultrasonography, B-mode ultrasonography [corrected], and exercise-tolerance testing after the age of 40. Angiography was performed when indicated. Lipoprotein lipase deficiency was assessed in vivo and in vitro by functional assays and DNA-sequence analysis. RESULTS: All four patients had a profound functional deficiency of lipoprotein lipase with a reduced enzymatic mass due to missense mutations on both alleles of the lipoprotein lipase gene. In all four patients, peripheral or coronary atherosclerosis (or both) was observed before the age of 55. Despite following a low-fat diet in which fat composed 10 to 15 percent of the daily caloric intake, the patients had hypertriglyceridemia (mean [+/- SD] triglyceride level, 2621 +/- 1112 mg per deciliter [29.59 +/- 12.55 mmol per liter]), low plasma levels of high-density lipoprotein cholesterol (17 +/- 7 mg per deciliter [0.43 +/- 0.18 mmol per liter]), and very low levels of LDL cholesterol (28 +/- 16 mg per deciliter [0.72 +/- 0.41 mmol per liter]). Three patients had one risk factor for atherosclerosis, whereas in one male patient, heavy smoking and diabetes were associated with an accelerated course of the disease. CONCLUSIONS: Premature atherosclerosis can occur in patients with familiar chylomicronemia as a result of mutations in the lipoprotein lipase gene. Defective lipolysis may increase susceptibility to atherosclerosis in humans.

Complete paternal isodisomy for chromosome 8 unmasked by lipoprotein lipase deficiency.

Uniparental disomy (UPD)-the inheritance of two homologous chromosomes from a single parent-may be unmasked in humans by the unexpected appearance of developmental abnormalities, genetic disorders resulting from genomic imprinting, or recessive traits. Here we report a female patient with familial chylomicronemia resulting from complete lipoprotein-lipase (LPL) deficiency due to homozygosity for a frameshift mutation in exon 2 of the LPL gene. She was the normal term product of an unremarkable pregnancy and had shown normal development until her current age of 5.5 years. The father (age 33 years) and the mother (age 24 years) were unrelated and healthy, with no family history of stillbirths or malformations. The father was a heterozygous carrier of the mutation, whereas no mutation in the LPL gene was detected in the mother. Southern blotting did not reveal any LPL gene rearrangement in the proband or her parents. The proband was homozygous for 17 informative markers spanning both arms of chromosome 8 and specifically for the haplotype containing the paternally derived LPL gene. This shows that homozygosity for the defective mutation in the LPL gene resulted from a complete paternal isodisomy for chromosome 8. This is the first report of UPD for chromosome 8 unmasked by LPL deficiency and suggests that normal development can occur with two paternally derived copies of human chromosome 8.

Phenotypic expression in double heterozygotes for familial hypercholesterolemia and familial defective apolipoprotein B-100.

Variability in the expression of monogenic lipid disorders may be observed in patients carrying the same DNA mutation, suggesting possible genetic or environmental interactions. Our objective was to investigate the genotype-phenotype relationships in two unrelated French patients with an aggravated expression of a dominantly inherited hypercholesterolemia. In probands, segregation analysis complemented by DNA sequencing identified heterozygous defective alleles and mutations on two nonallelic loci for two monogenic lipid disorders: familial hypercholesterolemia at the low density lipoprotein (LDL) receptor locus and familial defective apolipoprotein B-100 at the locus encoding its ligand, apolipoprotein B-100. The LDL-receptor missense mutations had been reported in French Canadians. The apolipoprotein B mutation was the Arg3500Gln founder mutation in Northern Europe. Probands had an unusual phenotype of aggravated hypercholesterolemia that was complicated with premature coronary arterial disease, although remaining responsive to lipid-lowering drugs. This phenotype was distinct from that observed in their heterozygous relatives and distinct from those observed in FH or FDB homozygotes. These cases refer to a new class of patients with digenic lipid disorders, defined by specific clinical features that result from the combined effects of two independent loci. Moreover, the observed phenotype of aggravated hypercholesterolemia gives further evidence that receptor and ligand play distinct roles in regulating LDL metabolism. Although uncommon, these cases give insight into the molecular mechanisms that underly the clinical variability of inherited hypercholesterolemia.

[Metastatic pulmonary carcinoma, revealed by Cushing syndrome, initially considered to have a pituitary origin. Course over 25 years]. / Carcinome pulmonaire métastatique, révélé par un syndrome de Cushing, initialement considéré comme d'origine hypophysaire. Evolution sur 25 ans.

It is often difficult to differentiate between Cushing's syndrome and ectopic ACTH hypersecretion which, in rare cases, may result from a carcinoid tumour. Several years may be required before development of patent Cushing's syndrome. We report the 25-year clinical course in a patient with a pulmonary carcinoid tumour. Initially, the hormone results led to the diagnosis of Cushing's syndrome and the patient was treated accordingly. Bilateral adrenectomy was performed in 1969 followed by radiotherapy of the pituitary gland in 1975 for suspected Nelson's syndrome. Actually, the carcinoid tumour, located retrocardially, had gone unnoticed until 1989. Diagnosis was suspected during a hospitalization in our unit and the patient underwent tumour exeresis and left inferior lobectomy. Despite tumour removal and demonstration of tumoural ACTH secretion, the levels of ACTH and beta-lipotrope hormone remained high suggesting lymph node and/or pulmonary metastasis. This observation emphasizes the long clinical course of carcinoid tumours despite their malignancy and the unusual response to the dexamethasone test.

Comparison of the efficacy of simvastatin and standard fibrate therapy in the treatment of primary hypercholesterolemia and combined hyperlipidemia.

Five multicenter, randomized, double-blind, placebo-controlled studies were conducted in France to compare the efficacy and safety of once-daily simvastatin treatment (10-40 mg/day) with conventional therapy with gemfibrozil 900 mg/day, ciprofibrate 100 mg/day, bezafibrate 400 mg/day, and fenofibrate 300 or 400 mg/day in a total of 800 patients with hypercholesterolemia. Simvastatin was associated with statistically significantly greater (p < or = 0.01) mean percent reductions in plasma low-density lipoprotein (LDL) cholesterol compared with each of the five fibrate regimens, even when administered at its recommended starting dose of 10 mg/day. Furthermore, approximately 90% of patients treated once daily with simvastatin experienced an at least 20% decrease in plasma LDL cholesterol compared with only 36 to 68% of patients treated with the individual fibrate agents (p < or = 0.05). The effectiveness of simvastatin in reducing LDL cholesterol did not differ as a function of the baseline plasma concentrations of total cholesterol or triglycerides. In contrast, the effectiveness of fibrate therapy in lowering plasma LDL cholesterol levels was significantly diminished (p < or = 0.05) among patients with triglyceride concentrations > 1.7 mmol/l. Plasma high-density lipoprotein (HDL) cholesterol levels were increased by approximately 10% after treatment with simvastatin or the fibrates. Although fibrate therapy was more effective overall in lowering plasma triglyceride levels, the effectiveness of simvastatin in reducing plasma triglyceride levels was generally 2- to 4-fold greater in patients with hypercholesterolemia associated with triglyceride levels > or = 2.3 mmol/l than in those with hypercholesterolemia associated with triglyceride levels < 2.3 mmol/l. The results of these studies confirm the superiority of simvastatin to standard fibrate therapy in reducing plasma levels of total and LDL cholesterol. They further indicate that once-daily treatment with simvastatin is effective in patients with isolated hypercholesterolemia or hypercholesterolemia associated with elevated triglyceride levels.

Blood antioxidants (vitamin E and beta-carotene) in long-term low density lipoprotein apheresis.

We measured vitamin E and beta-carotene in the serum and in circulating lipoproteins in a large population of 15 patients with familial hypercholesterolaemia who were undergoing long-term treatment by low density lipoprotein (LDL) apheresis. The technique used for apheresis was dextran sulphate cellulose adsorption. The results showed that before LDL apheresis, patients had high vitamin E and normal beta-carotene levels in the serum and in the VLDL+LDL fraction. There were no relationships between serum levels of vitamin E and beta-carotene and the duration of LDL-apheresis. Low vitamin E and beta-carotene levels in the HDL fraction could be related to the low HDL concentrations in these patients. Vitamin E/cholesterol ratios were similar to those of the normolipaemic controls whereas beta-carotene/cholesterol ratios were lower. After LDL-apheresis treatment, the ratios in the HDL fraction fell whereas the ratios in the serum and in the VLDL and LDL fraction did not change. This study shows that these patients exhibited no deficiency in either serum of VLDL-LDL of vitamin E or beta-carotene after long-term treatment by LDL-apheresis and that the status of these antioxidants in serum was independent of the duration of treatment.

Homozygous deletion of exon 9 causes lipoprotein lipase deficiency: possible intron-Alu recombination.

We studied a homozygous deletion in the lipoprotein lipase gene at the molecular level. Comprising the end of intron 8, the whole of exon 9, and about two-thirds of intron 9, this 2.136-kb deletion caused complete lipoprotein lipase deficiency and severe hypertriglyceridemia (type I hyperlipoproteinemia). Intron 9 of a normal control subject was also sequenced in order to define the exact borders of the deletion. Up to now, only the first 0.721 kb of intron 9 had been sequenced. Thus the complete sequence of intron 9 (3.090 kb) is now available. Three Alu sequences were characterized in the normal intron 9, while the proband had only the third complete Alu sequence. The first Alu sequence was located in the deleted region, and only the left arm of the second was present, as the deletion began near its center. A stem-loop structure involving a 14-nt region towards the end of intron 8 and an Alu sequence in intron 9 might have led to the deletion. Sequence analysis showed that the three Alu sequences belonged to the 40-million-year-old Alu-Sa subclass.

Identification of a new apolipoprotein E variant (E2 Arg142-->Leu) in type III hyperlipidemia.

A new rare apolipoprotein E mutant was identified as we were investigating the apolipoprotein E genotype of patients with type III hyperlipidemia (HLP III). The unusual DNA restriction fragment length polymorphism profile and then the sequence analysis of a PCR amplified fragment of the proband's apo E gene revealed a simple base substitution (G-->T) at nucleotide 3836. This mutation leads to the replacement of arginine by leucine at position 142 of the mature protein. The proband carried the mutant allele at the heterozygous status with an epsilon 3 allele. Subsequently, analysis of the proband's father's apo E gene showed that same mutated allele associated with an epsilon 2 allele. The two subjects presented a dysbetalipoproteinemia in which this new apo E variant could be implicated.

[Elevation of lipoprotein(a) levels in patients following transplantation for ischemic cardiopathy]. / Augmentation des concentrations de lipoprotéine (a) chez les malades greffés pour cardiopathie ischémique.

OBJECTIVES: Increased levels of serum lipoprotein (a) in heart transplant patients has been recently shown to be related to early recurrence of coronary artery disease. In order to evaluate the effect of the ischaemic origin of the heart disease we compared lipoprotein (a) levels observed in heart transplant patients who underwent transplantation due to ischaemic heart disease and non-obstructive cardiomyopathy with those in healthy control subjects. METHODS: Serum levels lipoprotein (a) were measured in 62 cardiac transplantation recipients who had a hyperlipidemia. The results were compared with those of 212 control subjects matched for age and who were referred for hyperlipidemia. RESULTS: In the whole population 40 patients had been operated on for coronary heart disease and 22 for idiopathic cardiomyopathy. The two populations did not differ with regard to their cardiovascular risk factors except for the smoking status. The mean Lp(a) values were significantly higher in the subjects with coronary heart disease as compared with those with idiopathic cardiomyopathy (0.33 +/- 0.24 and 0.21 +/- 0.17 mg/dl respectively; p < 0.05). The latter were not different from the control group (0.22 +/- 0.19 mg/ml). We did not find any difference between the two populations concerning the drugs taken by the patients (especially cyclosporine), LDL-cholesterol, creatinine, fasting blood glucose and TSH. CONCLUSION: Our data confirm the relation between coronary atherosclerosis and high lipoprotein (a) levels.

Evidence of non-deficient low-density lipoprotein receptor patients in a pool of subjects with clinical familial hypercholesterolemia profile.

For this study, we selected 41 adult patients with the classic clinical diagnosis of heterozygous familial hypercholesterolemia (FH), which is characterized by a low-density lipoprotein (LDL) cholesterol level above the 95th percentile, xanthomas, and/or personal or familial cardiovascular history. We used an indirect immunocytofluorimetric assay to classify these 41 subjects according to LDL receptor function on lymphocytes. We found that LDL receptor activity was normal in nine patients. A large study of plasma lipid, lipoprotein, and apolipoprotein levels found no significant difference between patients with and without LDL receptor defect. Familial defective apolipoprotein (apo) B-100 (FDB) and LDL-binding defects were not found in the nine patients without LDL receptor defect. These results suggest that other defects in the regulation of lipoprotein metabolism are capable of giving rise to a clinical and biochemical disorder indistinguishable from classic FH.

[Frameworks of recognition and classification of primary hyperlipidemia]. / Cadres de reconnaissance et de classification des hyperlipidémies primitives.

A both useful and simple classification of primary hyperlipidemias must be at the disposal of all medical doctors, namely general practitioners and cardiologists. The practical classification we have proposed and published since 1971, fulfills this aim. Three main frames of hyperlipidemias are individualized: 1) pure or essential hypercholesterolemia 2) mixed or combined hyperlipidemias 3) major hyperglyceridemia: either exogenous or endogenous. In each of these frames, some clinical specific features, as well as some very simple biologic characteristics allow sometimes an immediate orientation towards some definite varieties of primary hyperlipidemias, now perfectly identified at the level of molecular genetic (tendinosum xanthoma with or without planar xanthomas, palm creases syndrome, tuberous or tubero eruptive xanthomas, etc...). Similarly, occurrence of cardiovascular complications, chiefly coronary, in a rather early age, and with a striking repetition in other members of family, as well of attacks of acute or subacute pancreatitis in other forms, helps considerably for orientation of the diagnosis. For all these reasons, systematic reconstitution of genetic tree on, at least, three generations in absolutely necessary. Prevalence, in various populations, of the genetic origin of these various primary disorders of lipid metabolism is round one out of 500 at the heterozygote state. Even if all the genes candidates are not yet finished to be identified, much of them are now perfectly known, in their localisation on DNA and in their multiple mutations. Possibility of combination of different gene defects can be also met; and more and more are described. This extraordinary and explosive knowledge in this field is now to be described.

[Molecular genetics in pure primary hypercholesterolemia]. / Apports de la génétique moléculaire dans les hypercholestérolémies pures primitives.

Pure primary hypercholesterolemia include a set of lipid disorders related to the metabolism of Low Density Lipoproteins (LDL), which are now recognised as causes of atherosclerosis. Although many genetic and environmental factors contribute to their pathogenesis, two major genes influence LDL metabolism: the LDL receptor and its natural ligand, apolipoprotein B. These genes have been characterised and localised on human chromosomes, and can be studied at the molecular level. The many gene defects observed on both these loci as causes of primary hypercholesterolemia, have demonstrated the genetic heterogeneity of these disorders (one phenotype related to different predisposing loci). The candidate gene approach, is a method that can overcome the difficulties of this genetic heterogeneity. Using simplified molecular techniques it can be used in predictive diagnosis, pointing the predisposing locus, leading to the identification of causative mutations and guiding therapeutic strategies. Hence, new inborn errors of metabolism for which the molecular basis is well defined are now recognised, delineating the remaining defects to be characterised that also underlie primary hypercholesterolemia. These disorders account for the most frequent monogenic disorders in the French population. A better knowledge of their influence among other predisposing causes of atherosclerosis, will help define new preventive strategies based on the genetic component to its predisposition.

[Pathology of the human apolipoprotein E gene]. / Pathologie du gène de l'apolipoprotéine E humaine.

Apolipoprotein E (apo E) is a polymorphic glycoprotein that plays an essential part in the binding to receptors for the uptake of chylomicrons and VLDL remnants and of LDL. The three major isoforms are E3 (Cys112/Arg158), E4 (Arg112/Arg158) and E2 (Cys112/Cys158). The apo E genetic variation has a great impact. In most of type III familial hyperlipoproteinemias (HLP), E2 is implicated at the homozygote status. In other cases, rare alleles are directly responsible for dominant type III HLP. Apo E polymorphism is an essential determinant in the interindividual variations of lipids in healthy subjects in various populations. Its influence can be significant on the efficacy of nutritional or therapeutic interventions. The allele epsilon 4 appears to be associated with an increased risk of premature atherosclerosis. Recently, epsilon 4 was demonstrated to be associated with an early Alzheimer's disease onset. Apo E polymorphism contributes to the lipid disorders in diabetes and obesity. The analysis of apo E polymorphism can be carried out with two conceptually different approaches. The first one is based on the separation of plasma isoforms of the protein by isoelectric focusing or bidimensional electrophoresis. The other one consists in the application of molecular biology techniques (PCR and endonuclease restriction profiles) for a detection of the common alleles and of several rare alleles, avoiding the possible errors of the phenotyping technique of the apo E protein. The application of genetic engineering allows a better understanding of the role played by apo E towards its receptors and in other molecular interactions which are not well known up to now.

[Molecular genetics and lipoprotein lipase deficiency]. / Génétique moléculaire et déficit en lipoprotéine lipase.

Lipoprotein lipase (LPL) deficiency is the main cause of familial chylomicronemia, a disease characterised by high fasting plasma triglyceride levels, that can be complicated with acute pancreatitis. This autosomal recessive disorder is rare (1/10(6) in the general population). Classically this disorder is non atherogenic, and the heterozygotes are asymptomatic. To date, 35 gene mutations have been described throughout the world. We have studied 12 families in which the molecular basis for LPL deficiency had been established (direct sequencing of PCR products) by the presence of mutations on the LPL gene, in the 18 homozygous probands. We have found 13 mutations: 7 missense mutations in exons 5 and 6, 3 deletions of few bases in exons 3 and 4, 1 insertion one base in exon 2, one large deletion of exon 9, and one partial duplication of exon 6. PCR and enzymatic restriction of the LPL gene were used as methods for screening mutations or analysing polymorphic markers. This allowed a discrimination between heterozygote carriers (C, n = 35) and non carriers (NC, n = 26). Both groups were comparable for age, sex ratio, body mass index, life style habits, and other risk factors for atherosclerosis. Comparison (U-test Mann Whitney) of plasma lipid values revealed a lower HDL cholesterol level (C: 0,47 +/- 0,11 g/l vs NC: 0,58 +/- 0,18 g/l, p < 0.05) and a higher triglyceride level (C: 1,15 +/- 0,73 g/l vs NC: 0,77 +/- 0,43 g/l, p < 0.05) in heterozygotes. Conversely to the homozygous state, heterozygous LPL deficiency predisposes to a lipid profile that may be atherogenic evenly frequent (approximately 1/500) in the general population.