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Biomedical subjects

V Gudnason

Publications and source records attributed to V Gudnason.

At least 37 records · Page 2Linked to original sources
PubMed1997

Interaction of the cholesteryl ester transfer protein I405V polymorphism with alcohol consumption in smoking and non-smoking healthy men, and the effect on plasma HDL cholesterol and apoAI concentration.

Three hundred and sixteen healthy Icelandic men and women were examined for the effect of the cholesteryl ester transfer protein (CETP) I405V polymorphism on plasma triglycerides, HDL cholesterol (HDLC) and apoAI concentration. Genotyping was performed using an allele specific oligomelting assay and the frequency of the V allele was 0.31 (95 CI for men 0.23-0.33 and for women 0.29-0.39). In women no significant difference was associated with the V405 genotype for any plasma lipid trait. However, men who were homozygous for the V405 allele had 9% higher apoAI and 14% higher HDLC levels (p < 0.05) than those homozygous for the common I405 allele. The genotype effect was seen only in the non-smokers (p = 0.07 and < 0.05, respectively), and in those consuming alcohol (p < 0.05 for both). Analysis of interaction between the environmental, life-style factors and genotype in men for the traits of HDLC and apoAI showed statistically significant interaction of the genotype only with alcohol consumption. The non-smoking men who reported alcohol consumption and who were homozygous for the CETP V405 allele had 16% higher plasma apoAI concentration than those who carried the I405 allele, and up to 20% higher apoAI level than smokers. On the basis of prospective studies carried out on the Icelandic population, non-smoking, alcohol-consuming men who are homozygous for the V405 allele could have from 32% to 40% lower risk of having a heart attack.

Adolescent↗
PubMed1997

Single-strand conformation polymorphism analysis with high throughput modifications, and its use in mutation detection in familial hypercholesterolemia. The IFCC Scientific Division: Committee on Molecular Biology Techniques.

The identification of the specific mutation causing an inherited disease in a patient is the framework for the development of a rationale for therapy and of DNA-based tests for screening relatives. We present here a review of the single-strand conformational polymorphism (SSCP) method, which allows DNA fragments that have been amplified with specific primers and PCR to be scanned rapidly for any sequence variation. The general principles of the method are described, as are the major factors that must be considered in developing an optimal SSCP strategy, namely length of the PCR fragment and the temperature of the gel run. Options for sample denaturing gel characteristics and detection of DNA fragments are discussed. In addition, several modifications are presented that have been developed for high-throughput mutational analysis. The application of these techniques to screen for mutations in the LDL receptor gene in patients with familial hypercholesterolemia are described.

DNA↗
PubMed1997

Single-strand conformation polymorphism analysis with high throughput modifications, and its use in mutation detection in familial hypercholesterolemia. International Federation of Clinical Chemistry Scientific Division: Committee on Molecular Biology Techniques.

The identification of the specific mutation causing an inherited disease in a patient is the framework for the development of a rationale for therapy and of DNA-based tests for screening relatives. We present here a review of the single-strand conformational polymorphism (SSCP) method, which allows DNA fragments that have been amplified with specific primers and PCR to be scanned rapidly for any sequence variation. The general principles of the method are described, as are the major factors that must be considered in developing an optimal SSCP strategy, namely the length of the PCR fragment and the temperature of the gel run. Options for sample denaturing gel characteristics and detection of DNA fragments are discussed. In addition, several modifications are presented that have been developed for high-throughput mutational analysis. The application of these techniques to screen for mutations in the LDL receptor gene in patients with familial hypercholesterolemia are described.

DNA↗
PubMed1996

Use of the single strand conformation polymorphism method for rapid screening for mutations in the low density lipoprotein receptor gene in patients with familial hypercholesterolemia: effect on plasma lipid levels of different classes of mutations.

The single strand conformational polymorphism (SSCP) method was used to screen patients with familial hypercholesterolemia (FH) for mutations in the 3' part of exon 4 of the low density lipoprotein receptor (LDLR) gene. In 311 patients, six previously described mutations were identified in 29 apparently unrelated individuals (9.3%); three of the mutations are null alleles producing no protein, while the other three lead to production of a defective protein. In the patients where no mutation was detected mean total plasma cholesterol levels were 9.4 mmol/l, compared to 11.3 mmol/l in those individuals with a mutation creating a null allele, and 11.2 mmol/l in those with a mutation that resulted in the production of a defective protein (p < 0.001). These data reinforce observations of others that specific mutations in the LDL receptor gene are associated with different effects on plasma lipids, and indicate that the phenotype is influenced by the genotype.

Adult↗
PubMed1995

Effect of the StuI polymorphism in the LDL receptor gene (Ala 370 to Thr) on lipid levels in healthy individuals.

We have examined the effect on plasma lipid levels of a single base change in exon 8 of the LDL receptor gene that causes an amino acid change Ala 370 to Thr in a sample of 318 Icelandic individuals selected at random from the general population. The change destroys a StuI restriction site and was detected by digestion of pooled samples in groups of 5. The frequency of the loss of the cutting site was 0.05 (95% CI = 0.014-0.054). In men, those with the Thr allele (n = 18) had 8.3% higher total cholesterol, 11.8% higher LDL cholesterol and 10.3% higher apolipoprotein B than those with the common Ala allele, whereas in women those with the Thr allele (n = 12) had levels lower by 7.4%, 13.3% and 10.1% respectively. These differences reached statistical significance only in the men (p < 0.05). Functional analysis of CHO cells transfected with constructs of the LDL receptor cDNA carrying the Ala370 and Thr370 alleles showed that within the limits of the assays there was no difference in function of the LDL receptor protein as measured by uptake and degradation of LDL. The data raise the possibility that amino acid substitutions that could affect LDL receptor function below the limits of detection by conventional assays, may have an effect on plasma lipid levels in the general population.

Adolescent↗
PubMed1995

Response to drugs and diet in a compound heterozygote for familial hypercholesterolaemia.

A boy with a total plasma cholesterol concentration of 20.9 mmol/l which fell significantly with a low fat diet, cholestyramine and simvastatin, was shown to have two different mutations in the low density lipoprotein receptor gene, demonstrating that some patients with homozygous familial hypercholesterolaemia show a good lipid lowering response to treatment.

Base Sequence↗
PubMed1995

Utilities for high throughput use of the single strand conformational polymorphism method: screening of 791 patients with familial hypercholesterolaemia for mutations in exon 3 of the low density lipoprotein receptor gene.

We have modified several aspects of the single strand conformational polymorphism (SSCP) method to increase the speed with which the technique can be used for mutation detection. The methods attain high resolution of small mobility differences using long (30 cm) gels and use a modified polymerase reaction to maximise detection sensitivity using a minimised quantity of 32P. By using custom cut "sharktooth" combs (4.5 mm between teeth) as the slot formers, commercially available multichannel pipettes (9 mm tip to tip) can be used to load eight or 12 samples at a time from standard microtitre plates. PCR products that have been prepared and radiolabelled using simplified protocols are loaded on to the gel, and after a precalculated time of electrophoresis another set of samples can be loaded, either with combs moved across 2.25 mm or onto the same gel tracks. The run conditions are calculated so that there is no overlap between the bands produced by the two loadings, thus doubling the amount of information that can be gained from one gel. A computer program has been developed to solve equations to determine suitable timings for repetitive loadings. Finally, a modification of the gel pouring system is described so that two gels can be poured between three standard glass plates, with both gels run simultaneously. Of the order of 1000 PCR reactions can be prepared and analysed in 24 man hours using five 40 cm x 30 cm gel tanks. The application of these techniques is described to detect SSCPs in exon 3 of the low density lipoprotein receptor (LDLR) gene in 791 patients with familial hypercholesterolaemia (FH). Eight different SSCP patterns were seen, one of which was caused by the previously described E80K mutation, which was present in 11 patients (1.4%). In total, 32 patients (4%) were identified with exon 3 mutations.

Alleles↗
PubMed1994

Effect on plasma lipid levels of different classes of mutations in the low-density lipoprotein receptor gene in patients with familial hypercholesterolemia.

We used the single-strand conformational polymorphism method to screen 311 patients with familial hypercholesterolemia from London lipid clinics and Southampton and South West Hampshire health district for mutations in the 3' part of exon 4 of the low-density lipoprotein (LDL) receptor gene. This part of the gene codes for repeat 5 of the binding domain of the LDL receptor, which is known to be critical for the receptor-mediated removal of both triglyceride-rich lipoprotein remnants and LDL. Six previously described mutations were identified in 29 apparently unrelated individuals (9.3%), with the mutations all lying within a 50-bp fragment of the gene. Three of the mutations are null alleles producing no protein, and the other three lead to production of a defective protein. The effect of the different gene mutations on lipid levels was examined, after the data were combined with information on previously reported mutations in this patient group. Mean LDL cholesterol levels were highest in those individuals with a mutation creating a null allele (9.54 mmol/L) and were similar to levels in those individuals with a mutation affecting repeat 5 that resulted in the production of a defective protein (9.37 mmol/L). In this sample, previously identified patients with a defective protein mutation outside repeat 5 had lower mean levels of LDL cholesterol (7.78 mmol/L), which were similar to levels seen in patients in whom the specific mutation had not been identified (7.31 mmol/L). Overall, these differences were highly statistically significant (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

Use of the single-strand conformational polymorphism method to detect recurrent and novel mutations in the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia: detection of a novel mutation Asp200-->Gly.

The single-strand conformational polymorphism (SSCP) method was used to look for mutations in the 3' half of exon 4 of the low-density lipoprotein receptor gene in patients with familial hypercholesterolaemia (FH). One set of conditions were found which allowed the detection of four of the mutations that have previously been reported in this part of the gene and detected in patients in the United Kingdom: the 3-bp deletion (del Gly197) the 2-bp deletion (STOP 216), the Asp206-->Glu mutation and the Cys210-->STOP. The method was used to screen 50 patients with definite or probable FH from London. Two were identified who were carriers of the 3-bp deletion of Gly197, one who was a carrier of the Asp206-->Glu mutation and one who was a carrier of a novel mutation that alters Asp200-->Gly. This mutation creates a cutting site for the restriction enzyme MspI. In a further sample of 200 patients from London with FH one additional apparently unrelated individual was detected who was a carrier of this defect. Thus in the sample of 50 patients, four (8%) had a mutation in this part of exon 4 that could be readily detected using the SSCP method, suggesting that this approach will be useful for rapid screening for mutations in patients with FH.

Aspartic Acid↗
PubMed1993

Six DNA polymorphisms in the low density lipoprotein receptor gene: their genetic relationship and an example of their use for identifying affected relatives of patients with familial hypercholesterolaemia.

We have determined the relative allele frequency and estimated linkage disequilibrium between six DNA polymorphisms of the low density lipoprotein (LDL) receptor gene. Polymorphisms were detected using the enzymes SfaNI, TaqI, StuI, HincII, AvaII, and NcoI after DNA amplification by the polymerase chain reaction. Strong linkage disequilibrium was detected between many of the pair wise comparisons in a sample of 60 patients heterozygous for familial hypercholesterolaemia (FH). Using the enzymes HincII, NcoI, and SfaNI, 85% of patients were heterozygous for at least one polymorphism and thus potentially informative for cosegregation studies. The polymorphisms were used to follow the inheritance of the defective allele of the LDL receptor gene in the relatives of a patient with FH. Assays of LDL receptor activity on lymphoblastoid cell lines from two members of the family was used to confirm that the proband, but not the hypercholesterolaemic brother, had a defect in the LDL receptor. In the family, none of the children had inherited the allele of the LDL receptor gene inferred to be defective. The problems associated with this cosegregation approach to identify relatives of patients with a clinical diagnosis of FH are discussed.

Alleles↗
PubMed1993

Identification of recurrent and novel mutations in exon 4 of the LDL receptor gene in patients with familial hypercholesterolemia in the United Kingdom.

A group of 200 patients with familial hypercholesterolemia (FH) who were attending lipid clinics in the London area have been screened for four known point mutations and a microdeletion in exon 4 of the low density lipoprotein receptor gene by polymerase chain reaction (PCR) amplification of genomic DNA and either enzyme digestion of the product or hybridization with allele-specific oligonucleotides. A point mutation of Ser156-->Leu that was initially described in a Puerto Rican family was found in one patient of Polish origin on a different haplotype from that described originally and thus is likely to have occurred independently. A 3-bp deletion that causes deletion of amino acid Gly197 was found in six of the patients, who were all of Jewish origin and who shared the same haplotype for the mutant allele. A mutation of Asp206-->Glu that has been described in the Afrikaner population was found in three patients, two of UK origin and one a recent immigrant from South Africa. In all cases the haplotype of the mutant allele was compatible with that described in the original patient. The mutations at Asp154 reported in South African patients and at Glu207 reported in French Canadian patients were not detected in this sample. However, two additional mutations have been identified in this sample: the first, a 2-bp deletion in codon 206 that was found in five patients, all of British ancestry, and the second, a point mutation in a single patient of Irish origin that creates a stop codon at residue Cys210.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1993

The molecular genetics of pediatric lipid disorders: recent progress and future research directions.

Over the last 10 years, the explosion of molecular biology and molecular genetic techniques have allowed major advances in the diagnosis and management of a wide variety of human disorders. These range from accurate and simple screening for carriers of thalassemia (Old JM, Varawalla NY, Weatherall DJ: Lancet 2:834-837, 1990) to the use of preimplantation diagnosis of embryos at risk for untreatable congenital defects (Monk M, Holding C: Lancet 1:985-988, 1990) and the development of gene therapy for treatment of disorders such as adenosine deaminase deficiency (Sharp D: Lancet 1:1277-1278, 1991). These same molecular techniques have also been applied to pediatric lipid disorders with some notable successes, both in their diagnosis and understanding the mechanisms of the resulting pathology, including the recent experiments (Wilson JM, Grossman M, Wu CH, Chowdhury NR, Wu GY, Chowdhury JR: J Biol Chem 267:963-967, 1992) that have led to proposals to treat homozygous familial hypercholesterolemia by gene therapy. The purpose of this review is to detail this molecular genetic progress for two of the disorders that result in disturbed triglyceride metabolism in infants, lipoprotein lipase deficiency and apo CII deficiency, and four disorders that lead to disturbed cholesterol levels in infancy, abetalipoproteinemia, hypobetalipoproteinemia, familial defective apo B, and familial hypercholesterolemia. We will also address the question of how knowledge of the mutation causing the defect in a particular patient could be clinically useful and highlight areas of research for the future.

Apolipoproteins B↗
PubMed1992

Characterization of deletions in the LDL receptor gene in patients with familial hypercholesterolemia in the United Kingdom.

A sample of 200 patients with a clinical diagnosis of heterozygous (189) or homozygous (11) familial hypercholesterolemia (FH) attending lipid clinics in the London area have been screened for the presence of major gene defects in the low density lipoprotein (LDL) receptor gene by Southern blotting of genomic DNA with specific probes. This study is part of a project to determine the frequency of known mutations in the LDL receptor gene in this population. A new polymorphism for the enzyme Bgl II was identified by hybridization with a probe specific for the promoter plus exon 1 of the LDL receptor gene. The observed frequency of the rare allele, characterized by a Bgl II fragment of 13 kb compared with 10 kb for the common allele, was 0.08 in this group of FH patients. Several individuals who were heterozygous for the rare allele were also heterozygous for a mutation elsewhere in the LDL receptor gene that is known to cause FH. Eight different mutations, seven deletions and one duplication, were detected in a total of nine patients, accounting for 4.5% of the mutant alleles in this group. Three of the mutations are apparently identical to deletions that have been described previously in FH patients of British or European origin, while the remaining five have not been described. Two of these were in patients of Polish and Asian Indian origin, while the other three were in patients of apparently British ancestry.

Alleles↗
PubMed1992

Interaction between a polymorphism of the apo A-I promoter region and smoking determines plasma levels of HDL and apo A-I.

Epidemiological studies have demonstrated that the risk of coronary artery disease (CAD) is increased in smokers but reduced in individuals with elevated plasma levels of high density lipoprotein cholesterol (HDL-C) and apolipoprotein (apo) A-I. In a sample of 315 men and women from Iceland, the mean levels of HDL-C and apo A-I in smokers were, respectively, 12% and 6% lower in men and 7% and 6% lower in women compared with nonsmokers. In the men who were nonsmokers, a guanine (G) to adenine (A) (G/A) substitution 75 bp upstream from the start of transcription of the apo A-I gene was associated with elevated levels of HDL-C and apo A-I, with those carrying the A allele having levels of HDL-C and apo A-I roughly 10% higher than those with only the G allele. This genotype effect was abolished in the men who smoked and absent in the sample of women. Based on the reported protective effect associated with elevated levels of apo A-I and HDL-C, men carrying the A allele would have roughly a 20% lower relative risk of CAD compared with those without the A allele, but only if they remained nonsmokers. This gene polymorphism would therefore be an important factor in determining those men who would most benefit from avoidance or cessation of smoking. Determining the mechanism of such interaction between genotype and environment will be important in understanding the etiology of CAD.

Adolescent↗
PubMed1991

Identification of the 664 proline to leucine mutation in the low density lipoprotein receptor in four unrelated patients with familial hypercholesterolaemia in the UK.

Mutations in the gene for the low density lipoprotein (LDL) receptor cause Familial Hypercholesterolaemia (FH). One such mutation, a cytosine to thymine change in the codon for amino acid 664, causes proline (CCG) to be replaced by leucine (CTG) at this position, and creates a Pst I site in exon 14 of the gene. This mutation, previously identified in an FH homozygote of Asian Indian origin, results in a receptor with a reduced binding affinity for LDL and in delayed processing of the precursor form of the protein in cultured cells. A total of 224 unrelated heterozygous and 4 homozygous FH patients from London was screened for this mutation using direct amplification of genomic DNA by the polymerase chain reaction (PCR) and restriction digestion of the PCR product. Four patients were identified who were heterozgous for this mutation and the C to T base change was confirmed by sequencing. Affected relatives of these patients were also found to have the mutation. The effect of the mutation on LDL-receptor function in lymphoblastoid cell lines obtained from two of these patients was similar to that observed in heterozygous relatives of the original proband (MM). Eight polymorphisms of the LDL receptor gene were used to determine the haplotype of the defective allele carried by the patients and the individual (MM) in whom the mutation was first discovered. Two different haplotypes were found, suggesting that the mutation, which occurs at a CpG 'hotspot', has arisen independently at least twice. The presence of the same single base change in the LDL-receptor gene in several unrelated patients has not previously been reported in a population which is not geographically or culturally isolated.

Adolescent↗