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O Pedersen

Publications and source records attributed to O Pedersen.

At least 109 records · Page 6Linked to original sources
PubMed1999

A novel Phe75fsdelT mutation in the hepatocyte nuclear factor-4alpha gene in a Danish pedigree with maturity-onset diabetes of the young.

Mutations in 5 different genes [the hepatocyte nuclear factor (HNF)-4alpha), glucokinase, HNF-1alpha, insulin promoter factor-1, and HNF-1beta genes] have been shown to cause maturity onset diabetes of the young (MODY). About 50% of all known MODY in Danish Caucasian MODY probands can be explained by mutations in the HNF-1alpha gene (MODY3). To estimate the prevalence of MODY caused by mutations in the HNF-4alpha gene (MODY1), we screened 10 non-MODY3 probands for mutations in the minimal promoter and the 12 exons of the HNF-4alpha gene. One of the probands had a novel frameshift mutation (Phe75fsdelT) in exon 2 of the HNF-4alpha gene, resulting in a premature termination of translation after 117 amino acids of the messenger RNA encoded by that allele. The mutation cosegregated with diabetes in the pedigree and was not detected in 84 unrelated Danish Caucasian healthy glucose-tolerant control subjects or in 84 type 2 diabetic patients. At the time of examination, 4 of 6 mutation carriers were treated with insulin and 2 with oral hypoglycemic medication. Two mutation carriers had late-diabetic complications. Even though the HNF-4alpha protein is known to be important in the regulation of genes involved in lipid metabolism, carriers of the mutation did not differ from age and sex-matched control subjects, in regard to levels of fasting serum total cholesterol, serum high-density lipoprotein-cholesterol, and serum triglyceride. In conclusion, by screening 10 non-MODY3 probands for mutations in the HNF-4alpha gene, we identified 1 diabetes-associated frameshift mutation (Phe75fsdelT), suggesting that defects in HNF-4alpha are a rare cause of MODY in Denmark.

Adult↗
PubMed1999

Discovery of a Met300Val variant in Shc and studies of its relationship to birth weight and length, impaired insulin secretion, insulin resistance, and type 2 diabetes mellitus.

The Shc adaptor proteins corresponding to the 46-, 52-, and 66-kDa isoforms are key transducers of growth promotion and gene expression, which are being phosphorylated by all known receptor tyrosine kinases after stimulation by growth factors such as insulin and insulin-like growth factor I. Several studies have demonstrated a relationship between intrauterine growth retardation and impaired glucose tolerance or type 2 diabetes later in life. It is unclear whether this finding is partially explained by genetic factors. In this context, abnormalities in Shc proteins are considered to be a plausible candidate. Therefore, the aim of this study was to analyze whether genetic variability of the Shc isoforms causes a decrease in cell growth and cell differentiation that could be manifested by a decrease in birth weight and length, impaired acute insulin secretion after i.v. glucose, insulin resistance, and eventually a higher prevalence of type 2 diabetes. By single strand conformation polymorphism-heteroduplex analysis of 70 patients with diabetes mellitus and subsequent nucleotide sequencing of identified single strand conformation polymorphism variant, we discovered a Met300Val substitution of the 52-kDa isoform. The amino acid variant was predicted to be present in all 3 isoforms of Shc. In a genotype-phenotype study of 360 young healthy subjects, the allelic frequency of the codon 300 polymorphism was 4.2%. In this cohort, no significant differences could be shown between carriers and noncarriers in birth weight and length, the acute insulin response to i.v. glucose, or the insulin sensitivity index, as estimated from an i.v. glucose tolerance test. In an association study of 313 type 2 diabetic patients and 226 matched glucose-tolerant subjects, there was no significant difference in allelic frequency of the Shc variant (5.1% in diabetic patients vs. 3.1% in control subjects; P = 0.11). In conclusion, by itself the Met300Val polymorphism of Shc has no major impact on birth weight and length, insulin sensitivity index, acute glucose-induced insulin secretion, or prevalence of random type 2 diabetes mellitus.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Mutational analysis of the coding regions of the genes encoding protein kinase B-alpha and -beta, phosphoinositide-dependent protein kinase-1, phosphatase targeting to glycogen, protein phosphatase inhibitor-1, and glycogenin: lessons from a search for genetic variability of the insulin-stimulated glycogen synthesis pathway of skeletal muscle in NIDDM patients.

The finding of a reduced insulin-stimulated glucose uptake and glycogen synthesis in the skeletal muscle of glucose-tolerant first-degree relatives of patients with NIDDM, as well as in cultured fibroblasts and skeletal muscle cells isolated from NIDDM patients, has been interpreted as evidence for a genetic involvement in the disease. The mode of inheritance of the common forms of NIDDM is as yet unclear, but the prevailing hypothesis supports a polygenic model. In the present study, we tested the hypothesis that the putative inheritable defects of insulin-stimulated muscle glycogen synthesis might be caused by genetic variability in the genes encoding proteins shown by biochemical evidence to be involved in insulin-stimulated glycogen synthesis in skeletal muscle. In 70 insulin-resistant Danish NIDDM patients, mutational analysis by reverse transcription-polymerase chain reaction-single strand conformation polymorphism-heteroduplex analysis was performed on genomic DNA or skeletal muscle-derived cDNAs encoding glycogenin, protein phosphatase inhibitor-1, phophatase targeting to glycogen, protein kinase B-alpha and -beta, and the phosphoinositide-dependent protein kinase-1. Although a number of silent variants were identified in some of the examined genes, we found no evidence for the hypothesis that the defective insulin-stimulated glycogen synthesis in skeletal muscle in NIDDM is caused by structural changes in the genes encoding the known components of the insulin-sensitive glycogen synthesis pathway of skeletal muscle.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1999

Intermediate expansions of a GAA repeat in the frataxin gene are not associated with type 2 diabetes or altered glucose-induced beta-cell function in Danish Caucasians.

A variable expansion of a GAA repeat is present in the first intron of the frataxin gene, also termed FRDA1 or X25. Long repeat lengths (>66 repeats) are present in patients with Friedreich's ataxia, while an intermediate expansion (10-66 repeats) has recently been reported to be highly associated with type 2 diabetes. Using a polymerase chain reaction-based assay, we found that 32.4% (95%CI 29.9-34.9) of 636 Danish Caucasian type 2 diabetic patients were carriers of an intermediate expansion, whereas the frequency was 30.4% (26.4-34.4) among 224 matched glucose-tolerant control subjects (P = 0.6). In the control subjects, the values of serum insulin and C-peptide responses during an oral glucose tolerance test were similar between the 69 carriers and 155 noncarriers. Furthermore, we investigated a possible relationship between expansions of the FRDA1 gene and glucose-induced beta-cell function in 338 young Caucasians (33.7% [30.1-37.3] carriers) and in 215 glucose-tolerant subjects (31.0% [26.6-35.4] carriers) with a type 2 diabetic parent. In neither population did the carriers differ from noncarriers according to values of fasting plasma glucose, serum insulin, or C-peptide, acute serum insulin, or C-peptide responses after intravenous glucose. In conclusion, intermediate expansion of the frataxin trinucleotide repeat is not associated with type 2 diabetes or altered glucose-induced insulin secretion in Danish Caucasians.

Adult↗
PubMed1998

Evidence against protein kinase B as a mediator of contraction-induced glucose transport and GLUT4 translocation in rat skeletal muscle.

Both insulin and muscle contraction stimulate glucose transport activity. However, contraction stimulation does not involve the insulin signalling intermediate phosphatidylinositol 3-kinase (PI 3-kinase). Protein kinase B (PKB) has recently been identified as a direct downstream target of PI 3-kinase in the insulin signalling pathway. We have examined here whether the two stimuli share PKB as a convergent step in separate signalling pathways. Insulin stimulates both glucose transport, GLUT4 cell-surface content and PKB activity (by 4-6-fold above basal) in a wortmannin-sensitive manner in in vitro incubated rat soleus muscles. By contrast, muscle contraction, which stimulates glucose transport and the cell surface content of GLUT4 by 3-fold above basal levels, had no effect on PKB activity. These data demonstrate that PKB is not a mediator of contraction-induced glucose transport and GLUT4 translocation.

3-O-Methylglucose↗
PubMed1998

Organisation of the coding exons and mutational screening of the uncoupling protein 3 gene in subjects with juvenile-onset obesity.

Uncoupling proteins (UCPs) are mitochondrial transporters that uncouple the cellular respiration releasing stored energy as heat. Recently a third member of the UCP family was identified. Human UCP3 is different from UCP1 and UCP2 by its high and preferential expression in skeletal muscle and consequently the UCP3 gene is an attractive candidate gene for obesity. In this study we have determined the intron/exon organization of the coding region of the UCP3 gene and performed single strand conformation polymorphism (SSCP) analysis and direct sequencing of variants of the gene in 60 Caucasian subjects with juvenile-onset obesity. We detected 4 nucleotide substitutions in the intron regions and 2 silent amino acid variants. During the identification of the intron/exon structure of the gene in a normal healthy male subject with a BMI of 23.5 kg/m2, a nucleotide substitution replacing a glycine with a serine was identified at codon84. This variant was neither found among 156 subjects with juvenile-onset obesity nor among 205 control subjects. In a population based sample of 380 young healthy subjects the Gly/Ser84 variant was found in one female subject with a BMI of 25.5 kg/m2 and a fat mass of 23.7 kg. We conclude it is unlikely that variants in the coding region of the UCP3 gene contribute to the pathogenesis of juvenile-onset obesity among Danish Caucasians.

Adolescent↗
PubMed1998

Common amino acid substitutions in insulin receptor substrate-4 are not associated with Type II diabetes mellitus or insulin resistance.

The family of insulin receptor substrates (IRS1-4) is defined by proteins with an overall similar structure. IRS-1 and IRS-2 have been shown to have key roles in cellular transmission of the action of insulin, insulin-like growth factor-1 and various cytokines. We have previously identified amino acid polymorphisms in the human IRS-1 and IRS-2 proteins. Given the documented importance of IRS-1 and -2 in insulin signalling and the implications of distribution of these genes for the pathogenesis of insulin resistance and diabetes, we decided that the most recently identified member of the IRS family, IRS-4, was a relevant candidate to examine for genetic variability which might be associated with subsets of diabetes or insulin resistance. The gene encoding IRS-4 was analysed by the single strand conformation polymorphism technique in 83 Danish Caucasians with Type II (non-insulin-dependent) diabetes mellitus. Five amino acid polymorphisms were identified: Leu34Phe, Arg411Gly, Gly584Cys, His879Asp and Lys883Thr. In an association study of 324 patients with Type II diabetes and 267 control subjects with normal glucose tolerance the polymorphism at codon 34 was found with allelic frequencies of 3.9 and 2.3 %, respectively, the variant at codon 411 with allelic frequencies of 3.9 and 5.6%, respectively, and the variant at codon 879 with frequencies of 19.2 and 18.0%, respectively. Each carrier of the codon 34 polymorphism was also a carrier of the codon 411 and codon 879 variants and similarly, carriers of the variant at codon 411 were also carriers of the polymorphism at codon 879. The variants at codon 584 and 883 were each found in only one Type II diabetic patient. The allelic frequencies of the variants at codon 411 and 879 were also determined in 380 young healthy subjects (4.6 and 18.1 %, respectively). The insulin sensitivity index as estimated by Bergman's minimal model of the young healthy subjects carrying either polymorphism was indistinguishable from the carriers of wild-type IRS-4. Moreover, none of the men were heterozygous for the IRS-4 polymorphisms indicating that the gene is located on the X-chromosome. In conclusion, amino acid polymorphisms in human IRS-4 are common in Caucasians but are not associated with Type II diabetes or with insulin resistance in young healthy subjects.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Discovery of amino acid variants in the human glucose-dependent insulinotropic polypeptide (GIP) receptor: the impact on the pancreatic beta cell responses and functional expression studies in Chinese hamster fibroblast cells.

The two incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), are insulinotropic factors released from the small intestine to the blood stream in response to oral glucose ingestion. The insulinotropic effect of GLP-1 is maintained in patients with Type II (non-insulin-dependent) diabetes mellitus, whereas, for unknown reasons, the effect of GIP is diminished or lacking. We defined the exon-intron boundaries of the human GIP receptor, made a mutational analysis of the gene and identified two amino acid substitutions, A207 V and E354Q. In an association study of 227 Caucasian Type II diabetic patients and 224 matched glucose tolerant control subjects, the allelic frequency of the A207 V polymorphism was 1.1% in Type II diabetic patients and 0.7% in control subjects (p = 0.48), whereas the allelic frequency of the codon 354 polymorphism was 24.9% in Type II diabetic patients versus 23.2% in control subjects. Interestingly, the glucose tolerant subjects (6% of the population) who were homozygous for the codon 354 variant had on average a 14% decrease in fasting serum C-peptide concentration (p = 0.01) and an 11% decrease in the same variable 30 min after an oral glucose load (p = 0.03) compared with subjects with the wild-type receptor. Investigation of the function of the two GIP receptor variants in Chinese hamster fibroblasts showed, however, that the GIP-induced cAMP formation and the binding of GIP to cells expressing the variant receptors were not different from the findings in cells expressing the wildtype GIP receptor. In conclusion, amino acid variants in the GIP receptor are not associated with random Type II diabetes in patients of Danish Caucasian origin or with altered GIP binding and GIP-induced cAMP production when stably transfected in Chinese hamster fibroblasts. The finding of an association between homozygosity for the codon 354 variant and reduced fasting and post oral glucose tolerance test (OGTT) serum C-peptide concentrations, however, calls for further investigations and could suggest that GIP even in the fasting state regulates the beta-cell secretory response.

Alleles↗
PubMed1998

Mutations in the hepatocyte nuclear factor-1alpha gene in Caucasian families originally classified as having Type I diabetes.

Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene are the cause of maturity-onset diabetes of the young type 3 (MODY3), which is characterised by a severe impairment of insulin secretion and an early onset of the disease. Also at onset of diabetes some MODY patients show similar clinical symptoms and signs as patients with Type I (insulin-dependent) diabetes mellitus. The objective of this study was to estimate the prevalence of MODY3 patients misclassified as Type I diabetic patients. From a large population-based sample of unrelated Danish Caucasian Type I diabetic patients with an affected first degree relative, 39 patients (6.7%) who did not carry any high-risk HLA-haplotypes, i.e. DR3 or DR4 or both were examined by single-strand conformational polymorphism scanning and direct sequencing of the coding region and the minimal promoter of the HNF-1alpha gene. Four of the 39 Type I diabetic patients (10%) were identified as carrying mutations in the HNF-1alpha gene. One patient carried a missense mutation (Glu48Lys) in exon 1, two patients carried a missense mutation (Cys241Gly) in exon 4 and one patient carried a frameshift mutation (Pro291fsdelA) in exon 4. The mutations were all identified in heterozygous form, segregated with diabetes, and were not identified in 84 unrelated, healthy subjects. Furthermore, family history in three of the four families showed diabetes in four consecutive generations, suggestive of an autosomal dominant inheritance. In conclusion, about 10% of Danish diabetic patients without a high-risk HLA-haplotype, originally classified as having Type I diabetes could have diabetes caused by mutations in the HNF-1alpha gene. Clinical awareness of family history of diabetes and mode of inheritance might help to identify and reclassify these diabetic subjects as MODY3 patients.

Adolescent↗
PubMed1998

The effect of two frequent amino acid variants of the hepatocyte nuclear factor-1alpha gene on estimates of the pancreatic beta-cell function in Caucasian glucose-tolerant first-degree relatives of type 2 diabetic patients.

The objective of the present study was to investigate whether the frequent amino acid polymorphisms, Ile/Leu27 and Ser/Asn487, of the hepatocyte nuclear factor-1alpha gene were associated with alterations in glucose-induced serum C-peptide and serum insulin responses among glucose-tolerant first-degree relatives of type 2 diabetic patients. The study comprised 2 independent Danish cohorts. Among 74 unrelated type 2 diabetic relatives, 12 homozygous carriers of the Ile/Leu27 polymorphism had a 32% decrease in the 30-min serum C-peptide level (P = 0.01), as well as a 39% decrease in the 30-min serum insulin level (P = 0.02) during an oral glucose tolerance test. Ten homozygous carriers of the Ile/Leu27 variant did, however, not differ from wild-type carriers, with respect to the acute circulating insulin and serum C-peptide responses during an i.v. glucose tolerance test in the same study cohort. In a larger (more than 3-fold) study group of 230 glucose tolerant offspring of 62 type 2 diabetic probands, 33 homozygous carriers of the Ile/Leu27 variant did not differ, with respect to either serum insulin and serum C-peptide levels during an oral glucose tolerance test or acute serum insulin and serum C-peptide responses during an i.v. glucose tolerance test. We therefore consider the former positive finding as a statistical type I error. There were no differences in the above mentioned variables between carriers of the Ser/Asn487 polymorphism and wild-type carriers within any of the 2 study populations. Nor did carriers of combined genotypes, i.e. carriers of both the Ile/Leu27 and the Ser/Asn487 variants, show any associations with the examined variables. In conclusion, the Ile/Leu27 and Ser/ Asn487 polymorphisms of the hepatocyte nuclear factor-1alpha gene have apparently no major impact on the pancreatic beta-cell function, after an oral and i.v. glucose challenge, in Caucasian first-degree relatives of type 2 diabetic patients.

Adult↗
PubMed1998

The Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene contributes to the interindividual variation in serum C-peptide response during an oral glucose tolerance test: evidence from studies of 231 glucose-tolerant first degree relatives of type 2 diabetic probands.

The third form of maturity-onset diabetes of the young is caused by mutations in the hepatocyte nuclear factor-1alpha gene. Recently, we demonstrated an association between a prevalent polymorphism at codon 98, Ala/Val98, of this gene and a 20% decreased insulin release during an oral glucose tolerance test (OGTT) in middle-aged glucose-tolerant Danish Caucasian subjects. The major objective of the present study was to replicate this finding among glucose-tolerant first degree relatives of type 2 diabetic patients of the same ethnic origin. All participants, 231 glucose-tolerant offspring of 62 type 2 diabetic probands, underwent an OGTT with measurements of plasma glucose, serum insulin, and serum C peptide during the test. Thirty-three heterozygous carriers of the Ala/Val variant were identified, whereas no subjects had the variant in its homozygous form. Ala/Val carriers had a 20% reduction in serum C peptide at 30 min during the OGTT (1225+/-636 vs. 1507+/-624 pmol/L; P=0.02) compared to wild-type carriers. No significant differences in serum insulin levels during the OGTT were observed between carriers of the variant and Ala/Ala homozygotes. In conclusion, among Danish glucose-tolerant first degree relatives of type 2 diabetic patients the Ala/Val98 polymorphism of the hepatocyte nuclear factor-1alpha gene is associated with a decreased serum C-peptide secretion during an OGTT. This finding confirms our previously reported observation of the functional importance of the variant to insulin secretion during an OGTT among middle-aged healthy subjects.

Adult↗
PubMed1998

Analysis of the relationship between fasting serum uric acid and the insulin sensitivity index in a population-based sample of 380 young healthy Caucasians.

AIM: To determine whether fasting serum uric acid is associated with the insulin sensitivity index or with other anthropometric, metabolic or environmental features of the insulin resistance syndrome in a population-based sample of young healthy Caucasians. METHODS: The protocol included 380 unrelated Caucasian subjects (age 18-32 years) who had their insulin sensitivity index and glucose effectiveness measured during a combined intravenous glucose (0.3 g/kg body weight) and tolbutamide (3 mg/kg body weight) tolerance test. A number of anthropometric and biochemical tests, including the level of fasting serum uric acid, were carried out. RESULTS: In univariate analyses the concentration of fasting serum uric acid was negatively correlated to the insulin sensitivity index in both men (r2 = -0.25, P = 0.001) and women (r2 = -0.25, P < 0.001). In multivariate analysis controlling for age, gender, body mass index, waist to hip ratio, maximal aerobic capacity, fasting serum triglyceride and creatinine, daily intake of alcohol, smoking, use of oral contraceptives, and disposition for non-insulin dependent diabetes mellitus, the insulin sensitivity index was not significantly associated with fasting serum uric acid. However, 51% of the variation in the fasting serum uric acid level could be explained, and fasting serum triglyceride was the most important determinant of fasting serum uric acid. CONCLUSION: The major determinant of the fasting serum uric acid level in young healthy Caucasians is the fasting concentration of serum triglyceride, which has been shown to be a biochemical feature of the insulin resistance syndrome. Thus, hyperuricaemia appears to be an indirect part of the insulin resistance syndrome through its association with fasting hypertriglyceridaemia.

Adult↗
PubMed1998

Decreased tolbutamide-stimulated insulin secretion in healthy subjects with sequence variants in the high-affinity sulfonylurea receptor gene.

The high-affinity sulfonylurea receptor (SUR1) is, as a subunit of the ATP-sensitive potassium channel, an important regulator of insulin secretion in the pancreatic beta-cell. The aim of this study was to examine if genetic variability of the SUR1 gene was associated with NIDDM or altered pancreatic beta-cell function. Mutational analysis of all the 39 SUR1 exons, including intron-exon boundaries, in 63 NIDDM patients revealed two missense variants, five silent variants in the coding region, and four intron variants. The two missense variants (Asp673Asn and Ser1369Ala) and two sequence variants (ACC-->ACT, Thr759Thr and a c-->t intron variant in position -3 of the exon 16 splice acceptor site) were examined for association with NIDDM and for a possible influence on insulin and C-peptide secretion after intravenous glucose and tolbutamide loads in a random sample of unrelated, healthy, young Danish Caucasians. The Asp673Asn variant in exon 14 was only identified in one NIDDM patient, and the allelic frequency of the Ser1369Ala was similar among 247 control subjects (0.38 [95% CI 0.34-0.42]) and 406 NIDDM patients (0.40 [0.37-0.43]). The allelic frequency of the silent exon 18 Thr775Thr variant was 0.051 (0.035-0.067) in NIDDM patients (n=392) and 0.027 (0.013-0.041) in control subjects (n=246; chi2=4.99, P=0.03). The allelic frequency of the intron variant was similar among NIDDM patients (0.45 [0.42-0.48]) and control subjects (0.44 [0.40-0.48]). Of 386 NIDDM patients, 17 had the combined genotype exon 18 C/T and intron -3c/-3t (0.044 [0.024-0.064]), whereas 3 of 243 control subjects had the same combined genotype (0.012 [0-0.026]; chi2=4.87, P=0.03; odds ratio: 3.69 [1.07-12.71]). Of 380 unrelated, healthy, young Danish Caucasians, 10 (0.026 [0.010-0.042]) had the combined at-risk genotype. These subjects had, on average, a 50% reduction in serum C-peptide and a 40% reduction in serum insulin responses upon tolbutamide injection (P=0.002 and P=0.05, respectively) but normal serum C-peptide and insulin responses upon glucose injection. In conclusion, a silent polymorphism in exon 18 of the SUR1 gene is associated with NIDDM in a Danish Caucasian population. In combination with an intron variant, the association is higher, and young, healthy carriers of the intragenic combination have reduced serum C-peptide and insulin responses to a tolbutamide load.

ATP-Binding Cassette Transporters↗
PubMed1997

Expression of protein-tyrosine phosphatases in the major insulin target tissues.

Protein-tyrosine phosphatases (PTPs) are key regulators of the insulin receptor signal transduction pathway. We have performed a detailed analysis of PTP expression in the major human insulin target tissues or cells (liver, adipose tissue, skeletal muscle and endothelial cells). To obtain a representative picture, all tissues were analyzed by PCR using three different primer sets corresponding to conserved regions of known PTPs. A total of 24 different PTPs were identified. A multiprobe RNase protection assay was developed to obtain a semiquantitative measure of the expression levels of selected PTPs. Surprisingly, PTP-LAR, previously suggested to be a major regulator of the insulin receptor tyrosine kinase, was expressed in extremely low levels in skeletal muscle, whereas the related receptor-type PTP-sigma and PTP-alpha were expressed in relatively high levels in all four tissues. The low levels of LAR PTP mRNA in skeletal muscle were further confirmed by Northern blot analysis.

Adipose Tissue↗