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Biomedical subjects

Stefan Marklund

Publications and source records attributed to Stefan Marklund.

10 recordsLinked to original sources
PubMed2006

Genetically increased antioxidative protection and decreased chronic obstructive pulmonary disease.

RATIONALE: Increased oxidative stress is involved in chronic obstructive pulmonary disease (COPD); however, plasma and bronchial lining fluid contains the antioxidant extracellular superoxide dismutase. Approximately 2% of white individuals carry the R213G polymorphism in the gene encoding extracellular superoxide dismutase, which increases plasma extracellular superoxide dismutase 10-fold and presumably also renders bronchial lining fluid high in extracellular superoxide dismutase. OBJECTIVE: We tested the hypothesis that R213G reduces the risk of COPD. METHODS: We studied cross-sectionally and prospectively (during 24 yr) 9,258 individuals from the Danish general population genotyped for R213G. MEASUREMENTS: We determined plasma extracellular superoxide dismutase concentration, pulmonary function and COPD diagnosed by means of spirometry or through national hospitalization and death registers. MAIN RESULTS: In the general population, 97.5% were noncarriers, 2.4% were heterozygotes, and 0.02% were homozygotes. Among R213G noncarriers, extracellular superoxide dismutase plasma concentration was 148+/-52 and 142+/-43 ng/ml (mean+/-SD) in individuals with and without COPD (Student's t test, p=0.02). Among heterozygotes, corresponding concentrations were 1,665+/-498 ng/ml and 1,256+/-379 (p<0.001). The adjusted odds ratio for spirometrically diagnosed COPD in heterozygotes versus noncarriers was 0.5 (95% confidence interval: 0.3-0.9). After stratification, the equivalent adjusted odds ratio was 1.5 (0.3-6.6) among nonsmokers and 0.4 (0.2-0.8) among smokers (p value for interaction=0.10). The adjusted hazard ratio for COPD hospitalization or death during follow-up in heterozygotes versus noncarriers was 0.3 (0.1-0.8). CONCLUSIONS: Extracellular superoxide dismutase R213G heterozygosity protects against development of COPD in the Danish general population. This was observed in smokers, but not in nonsmokers.

Aged↗
PubMed2005

High-throughput data analysis for detecting and identifying differences between samples in GC/MS-based metabolomic analyses.

In metabolomics, the objective is to identify differences in metabolite profiles between samples. A widely used tool in metabolomics investigations is gas chromatography-mass spectrometry (GC/MS). More than 400 compounds can be detected in a single analysis, if overlapping GC/MS peaks are deconvoluted. However, the deconvolution process is time-consuming and difficult to automate, and additional processing is needed in order to compare samples. Therefore, there is a need to improve and automate the data processing strategy for data generated in GC/MS-based metabolomics; if not, the processing step will be a major bottleneck for high-throughput analyses. Here we describe a new semiautomated strategy using a hierarchical multivariate curve resolution approach that processes all samples simultaneously. The presented strategy generates (after appropriate treatment, e.g., multivariate analysis) tables of all the detected metabolites that differ in relative concentrations between samples. The processing of 70 samples took similar time to that of the GC/TOFMS analyses of the samples. The strategy has been validated using two different sets of samples: a complex mixture of standard compounds and Arabidopsis samples.

Arabidopsis↗
PubMed2004

Toxicity of familial ALS-linked SOD1 mutants from selective recruitment to spinal mitochondria.

One cause of amyotrophic lateral sclerosis (ALS) is mutation in ubiquitously expressed copper/zinc superoxide dismutase (SOD1), but the mechanism of toxicity to motor neurons is unknown. Multiple disease-causing mutants, but not wild-type SOD1, are now demonstrated to be recruited to mitochondria, but only in affected tissues. This is independent of the copper chaperone for SOD1 and dismutase activity. Highly preferential association with spinal cord mitochondria is seen in human ALS for a mutant SOD1 that accumulates only to trace cytoplasmic levels. Despite variable proportions that are successfully imported, nearly constant amounts of SOD1 mutants and covalently damaged adducts of them accumulate as apparent import intermediates and/or are tightly aggregated or crosslinked onto integral membrane components on the cytoplasmic face of those mitochondria. These findings implicate damage from action of spinal cord-specific factors that recruit mutant SOD1 to spinal mitochondria as the basis for their selective toxicity in ALS.

Aging↗
PubMed2004

The 5'-AMP-activated protein kinase gamma3 isoform has a key role in carbohydrate and lipid metabolism in glycolytic skeletal muscle.

5'-AMP-activated protein kinase (AMPK) is a metabolic stress sensor present in all eukaryotes. A dominant missense mutation (R225Q) in pig PRKAG3, encoding the muscle-specific gamma3 isoform, causes a marked increase in glycogen content. To determine the functional role of the AMPK gamma3 isoform, we generated transgenic mice with skeletal muscle-specific expression of wild type or mutant (225Q) mouse gamma3 as well as Prkag3 knockout mice. Glycogen resynthesis after exercise was impaired in AMPK gamma3 knock-out mice and markedly enhanced in transgenic mutant mice. An AMPK activator failed to increase skeletal muscle glucose uptake in AMPK gamma3 knock-out mice, whereas contraction effects were preserved. When placed on a high fat diet, transgenic mutant mice but not knock-out mice were protected against excessive triglyceride accumulation and insulin resistance in skeletal muscle. Transfection experiments reveal the R225Q mutation is associated with higher basal AMPK activity and diminished AMP dependence. Our results validate the muscle-specific AMPK gamma3 isoform as a therapeutic target for prevention and treatment of insulin resistance.

AMP-Activated Protein Kinases↗
PubMed2003

Genetically reduced antioxidative protection and increased ischemic heart disease risk: The Copenhagen City Heart Study.

BACKGROUND: Extracellular superoxide dismutase (EC-SOD) is an antioxidative enzyme found in high concentrations in the arterial wall. Two to three percent of all people in Denmark carry an R213G substitution, which increases plasma concentration 10-fold. This may reduce arterial wall EC-SOD concentrations, increase intimal LDL oxidation, and therefore may accelerate atherogenesis. Our primary hypothesis was that EC-SOD-R213G predisposes to ischemic heart disease (IHD). The secondary hypothesis was that EC-SOD-R213G offers predictive ability with respect to IHD beyond that offered by measurements of plasma EC-SOD and autoantibodies against oxidized LDL (oxLDL). METHODS AND RESULTS: The primary hypothesis was tested in a prospective, population-based study of 9188 participants from The Copenhagen City Heart Study with 956 incident IHD events during 23 years of follow-up and retested cross-sectionally with independent case populations of patients with IHD (n=943) or ischemic cerebrovascular disease (ICVD) (n=617). Case populations were compared with unmatched IHD/ICVD-free control subjects from The Copenhagen City Heart Study (n=7992). The secondary hypothesis was tested by using a nested case-control study comparing patients with IHD (n=956) with age- and gender-matched control subjects (n=956). Age- and gender-adjusted relative risk for IHD in heterozygotes (n=221, 2.4%) versus noncarriers (n=8965, 97.6%) was 1.5 (95% CI, 1.1 to 2.1). Retesting confirmed this: Age- and gender-adjusted odds ratios for IHD was 1.4 (1.0 to 2.0) and for ICVD 1.7 (1.1 to 2.7). Additional adjustment for plasma EC-SOD produced an odds ratio for IHD in heterozygotes versus noncarriers of 9.2 (1.2 to 72), whereas adjustment for autoantibodies against oxLDL produced an odds ratio of 2.5 (1.2 to 5.3). CONCLUSIONS: Heterozygosity for EC-SOD-R213G is associated with increased IHD risk. Genotyping offers predictive ability with respect to IHD beyond that offered by plasma EC-SOD and autoantibodies against oxLDL.

Adult↗
PubMed2003

Expression profiling of the gamma-subunit isoforms of AMP-activated protein kinase suggests a major role for gamma3 in white skeletal muscle.

Expression patterns of the three isoforms of the regulatory gamma-subunit of AMP-activated protein kinase (AMPK) were determined in various tissues from adult humans, mice, and rats, as well as in human primary muscle cells. Real-time PCR-based quantification of mRNA showed similar expression patterns in the three species and a good correlation with protein expression in mice and rats. The gamma3-isoform appeared highly specific to skeletal muscle, whereas gamma1 and gamma2 showed broad tissue distributions. Moreover, the proportion of white, type IIb fibers in the mouse and rat muscle samples, as indicated by real-time PCR quantification of Atp1b2 mRNA, showed a strong positive correlation with the expression of gamma3. In samples of white skeletal muscle, gamma3 clearly appeared to be the most abundant gamma-isoform. Differentiation of human primary muscle cells from myoblasts into multinucleated myotubes was accompanied by upregulation of gamma3 mRNA expression, whereas levels of gamma1 and gamma2 remained largely unchanged. However, even in these cultured myotubes, gamma2 was the most highly expressed isoform, indicating a considerable difference compared with adult skeletal muscle. Immunoblot analysis of mouse gastrocnemius and quadriceps muscle extracts precipitated with a gamma3-specific antibody showed that gamma3 was exclusively associated with the alpha2- and beta2-subunit isoforms. The observation that the AMPKgamma3 isoform is expressed primarily in white skeletal muscle, in which it is the predominant gamma-isoform, strongly suggests that gamma3 has a key role in this tissue.

AMP-Activated Protein Kinases↗
PubMed2003

Sustained decrease in superoxide dismutase activity underlies constrictive remodeling after balloon injury in rabbits.

OBJECTIVE: The redox pathophysiology of vascular repair is incompletely understood. We assessed the role of vascular superoxide dismutase (SOD) activity in oxidative/nitrative stress and caliber loss postinjury (PI). METHODS AND RESULTS: Rabbits submitted to iliac artery balloon overdistension were followed for 14 days PI. Significant decrease in vascular SOD activity occurred at 7 and 14 days PI (by 45% and 34%, respectively, versus control, 96+/-1 U/mg, P<0.05). Separation in concanavalin-A column showed that both extracellular SOD (ecSOD) and CuZn SOD activities were reduced, whereas Western analysis showed normal or augmented protein expression. Immunoreactivity to nitrotyrosine, neuronal NO synthase (NOS), and inducible NOS (iNOS) increased in media and neointima PI; iNOS mRNA also augmented. Administration of ecSOD from days 7 to 14 PI corrected the SOD activity decrease and minimized caliber loss by 59% (P=0.007) despite unaltered neointima. Nitrate levels markedly increased with ecSOD in injured artery homogenates (26+/-5 versus 4+/-0.3 micromol/L per mg, P=0.001). Such increase was 70% inhibited by specific iNOS antagonist 1400w. Nitrotyrosine and neuronal NOS expression decreased after ecSOD. CONCLUSIONS: Sustained low vascular SOD activity has a key role in constrictive remodeling after injury, promoting oxidative/nitrative stress and impairment of iNOS-derived NO bioavailability. SOD function may critically determine whether iNOS induction is beneficial or deleterious in vivo.

Animals↗
PubMed2002

A large duplication associated with dominant white color in pigs originated by homologous recombination between LINE elements flanking KIT.

The Dominant White (I/KIT) locus is one of the major coat color loci in the pig. Previous studies showed that the Dominant White (I) and Patch (IP) alleles are both associated with a duplication including the entire KIT coding sequence. We have now constructed a BAC contig spanning the three closely linked tyrosine kinase receptor genes PDGFRA-KIT-KDR. The size of the duplication was estimated at about 450 kb and includes KIT, but not PDGFRA and KDR. Sequence analysis revealed that the duplication arose by unequal homologous recombination between two LINE elements flanking KIT. The same unique duplication breakpoint was identified in animals carrying the I and IP alleles across breeds, implying that Dominant White and Patch alleles are descendants of a single duplication event. An unexpected finding was that Piétrain pigs carry the KIT duplication, since this breed was previously assumed to be wild type at this locus. Comparative sequence analysis indicated that the distinct phenotypic effect of the duplication occurs because the duplicated copy lacks some regulatory elements located more than 150 kb upstream of KIT exon 1 and necessary for normal KIT expression.

Alleles↗
PubMed2002

A nonsense mutation in the FMO3 gene underlies fishy off-flavor in cow's milk.

Fish-odor syndrome or Trimethylaminuria (OMIM #602079) in humans is an inborn error of metabolism associated with a characteristic fishy body odor due to elevated levels of trimethylamine (TMA) in body fluids. It is caused by loss-of-function mutations in FMO3 encoding flavin-containing mono-oxygenase 3. A fishy off-flavor is occasionally observed in cow's milk and it has been established recently that this phenotype is due to elevated TMA levels. Here, we report that fishy off-flavor in cow's milk is caused by a nonsense mutation (R238X) in the bovine FMO3 ortholog. RT-PCR analysis indicated that the mutant transcript is present in a very low amount. The mutation was found to be surprisingly common (q = 0.155) in one breed of cattle.

Amino Acid Substitution↗