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Biomedical subjects

H Luthman

Publications and source records attributed to H Luthman.

At least 73 records · Page 4Linked to original sources
PubMed1994

Impact of diabetic inheritance on glucose tolerance and insulin secretion in spontaneously diabetic GK-Wistar rats.

The impact of genetic factors and maternal diabetes on glucose tolerance and pancreatic beta-cell function was studied in first generation (F1) offspring generated in crosses between the spontaneously diabetic Goto-Kakizaki (GK)-Wistar rat and normoglycemic control Wistar rats (W). The (GK x W) F1 hybrids were offspring of either male GK (mGK) and female Wistar (fW) (mGK x fW) or male Wistar (mW) and female GK (fGK) (mW x fGK) rats. Already at 8 days of age, blood glucose levels were elevated in GK (7.6 +/- 0.5 vs. 4.8 +/- 0.3 mM in W; P < 0.001) and in F1 rats (6.0 +/- 0.3 in mGK x fW and 6.6 +/- 0.4 mM in mW x fGK; both P < 0.01 vs. W). In 2-month-old male rats, glucose (2 g/kg, intraperitoneally) markedly increased blood glucose levels after 60 min in GK rats (18.1 +/- 0.6 vs. 5.5 +/- 0.3 mM in W; P < 0.001) and moderately increased levels in F1 rats (9.9 +/- 0.9 in mGK x fW and 11.6 +/- 1.0 mM in mW x fGK, both P < 0.01 vs. W). Similar patterns were obtained in female rats. Repeated backcrossing of F1 with W rats successively improved glucose tolerance. In perfused pancreases of male rats, the 20-min insulin response to 16.7 mM glucose was -7.44 +/- 5.18 pmol in GK rats, 71.57 +/- 12.25 pmol in W rats, 9.00 +/- 0.89 pmol in mGK x fW rats, and 18.20 +/- 3.97 pmol in mW x fGK rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Tight linkage between the Beckwith-Wiedemann syndrome and a microsatellite marker for the TH locus.

The Beckwith-Wiedemann syndrome (BWS) is characterized by somatic overgrowth, developmental anomalies, and proneness to embryonic tumor development. The majority of cases are sporadic, but several families with an autosomal dominant mode of inheritance with variable expression and reduced penetrance have been described. In three such families, BWS has been linked to DNA markers for the insulin gene (INS) and H-ras on chromosome band 11p15. Two additional families with inherited BWS are described here. Linkage analysis has been performed with a highly informative marker for the tyrosine hydroxylase (TH) locus within the INS-IGF2 (insulin-like growth factor II)-TH gene cluster and confirms the previous observed linkage to this region (lod score 2.16 at theta = 0). Linkage analysis to TH provides a basis for informed genetic counselling and carrier detection in the hereditary form of the syndrome. Based on the hypothesis that IGF2 may be a candidate gene for BWS, we screened for mutations in the coding exons 7 and 9, but found no abnormalities in 5 unrelated BWS cases.

Beckwith-Wiedemann Syndrome↗
PubMed1993

[Physiopathology of mitochondria. From Luft's disease to aging and diabetes].

The first disease due to disturbances in a cell organelle was discovered in 1959-62, and its basis was loose-coupling of oxidative phosphorylation in the skeletal muscle mitochondria accompanied by severe alterations of their structure (Luft's disease). During the 1980s, functional disturbances and structural alterations in the mitochondria were observed in more than 100 disease entities, mainly in parts of the central nervous system and skeletal muscles. A second breakthrough in this area was the discovery in 1963-64 that mitochondria had their own DNA, mtDNA. Following the observation in 1988 of mutations of mtDNA in mitochondrial diseases, such mutations--mainly deletions and point mutations--were observed in almost all mitochondrial diseases. A remarkable extension of the area is the notion that "normal" ageing is accompanied by decreased oxidative phosphorylation and the appearance of mtDNA mutations. During the last two years, such changes have been demonstrated in diseased states in tissues and organs, which are especially reliant on oxygen supply: in the central nervous system (Parkinson's disease, some types of epilepsy and seizures, Huntington's disease, possibly also in Alzheimer's disease); in heart muscle (cardiomyopathies) and in skeletal muscle. Type 2 diabetes or NIDDM engages two tissues most reliant on oxygen consumption, the pancreatic islets (insulin secretion) and skeletal muscle (insulin sensitivity). Both these functions are genetically determined, the latter to a high degree also controlled by "environmental" factors. The evident age factor in the development of NIDDM could be on a par with the "normal" ageing process.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Steroid 21-hydroxylase (P450c21): a new allele and spread of mutations through the pseudogene.

Lesions in the gene encoding the adrenal enzyme steroid 21-hydroxylase (P450c21) result in defective adrenal cortisol synthesis, often accompanied by aldosterone deficiency. The symptoms range from severe neonatal disease to inconspicuous symptoms in adulthood depending on the nature of the mutations. The 21-hydroxylase gene is present in close proximity to a highly homologous pseudogene, and both genes show variation in copy number between individuals. For complete DNA sequence characterization, we have applied selective polymerase chain reaction amplification and direct sequencing of all full-length steroid 21-hydroxylase genes present in individuals. Using healthy individuals with only one remaining steroid 21-hydroxylase allele as normal references, a new allele was found in two siblings, in whom clinical and laboratory findings demonstrated moderate enzyme deficiency. Full-length sequencing of this allele displayed an Arg 484 to Pro codon change in exon 10, in the same position as a previously identified GG to C mutation found in a patient with severe 21-hydroxylase deficiency. Arg 484 is located within a stretch of amino acids that are highly conserved between mammalian 21-hydroxylases. The finding of the presently reported 21-hydroxylase allele indicates that the GG to C mutation from the severely affected patient has arisen by a two-step mechanism, consisting of a G to C transversion accompanied by an adjacent G deletion. When sequencing 26 pseudogenes, both these mutations, which are not present in the pseudogenes hitherto reported, were found at low frequency together with a number of other polymorphisms. Thus, also rare mutations can spread via the pseudogene and can therefore be expected to arise independently in unrelated individuals.

Adrenal Hyperplasia, Congenital↗
PubMed1993

DNA polymorphisms in the human tyrosine hydroxylase/insulin/insulin-like growth factor II chromosomal region in relation to glucose and insulin responses.

The feasibility of disease association studies using polymorphic DNA markers in the tyrosine hydroxylase/insulin/insulin-like growth factor II chromosomal region was indicated by a high degree of linkage disequilibrium found in haplotypes. Haplotypes were resolved in the parents from Scandinavian nuclear families by studying the segregation of eight DNA polymorphisms. Comparison of observed vs expected frequencies of haplotypes, as well as pairwise measures of linkage disequilibrium, indicated a high degree of linkage disequilibrium. Five restriction fragment length polymorphisms linked to the tyrosine hydroxylase/insulin/insulin growth factor II region of chromosome 11 were investigated in relation to Type 2 (non-insulin-dependent) diabetes mellitus, and to glucose and insulin responses to glucose infusion in healthy subjects. No significant differences in genotype frequencies between Type 2 diabetic (n = 53) and healthy subjects (n = 106) were found. A significant association (p < 0.001) was initially found between genotypes defined by a PstI polymorphism located 5' of the tyrosine hydroxylase gene and the early glucose response to a standardized glucose infusion test in healthy subjects. However, a follow-up study of 112 healthy individuals failed to confirm this finding.

Alleles↗
PubMed1993

Steroid 21-hydroxylase deficiency: two additional mutations in salt-wasting disease and rapid screening of disease-causing mutations.

A method for genetic diagnosis of steroid 21-hydroxylase deficiency was developed based on allele-specific PCR. With this approach, genotyping of fourteen mutations and diagnosis of homozygous gene deletions can be performed within hours from tissue sampling. One patient with salt-wasting disease had normal genotype at all positions screened. DNA sequencing revealed two novel mutations, a G to C transversion at the conserved splice donor site of intron 7 and a TGG to TAG nonsense mutation at Trp 406 in exon 9. Allele-specific PCR was established also for these mutations and used to screen for their presence in the pseudogene. However, the two novel mutations were not found in at least 34 pseudogenes.

Adrenal Hyperplasia, Congenital↗
PubMed1993

Differences in the ratio of RNA encoding two isoforms of the insulin receptor between control and NIDDM patients. The RNA variant without Exon 11 predominates in both groups.

Two alternative forms of the insulin receptor with different affinities for insulin are expressed as a result of alternative splicing of RNA corresponding to exon 11 of the IR gene. The percentage of IR-RNA molecules without exon 11, encoding the high-affinity isoform, was determined by cDNA-mediated PCR amplification of RNA extracts from the quadriceps femoris muscle of healthy control subjects (n = 9) and NIDDM patients (n = 7). In both patients and control individuals, a majority of the IR-RNA molecules contained exon 11. In addition, the proportion of IR-RNA molecules without exon 11 was decreased in patients (21 +/- 1%) compared with control subjects (31 +/- 3%) (P = 0.018). Careful investigation of the kinetics of the PCR-based assay system, as well as the conditions for separation of the PCR products, allowed us to suggest a possible explanation of the discrepant results concerning the alternative splicing presented in previous reports. The diabetic subjects as a group had higher fasting insulin levels and lower insulin-mediated glucose uptake during a euglycemic-hyperinsulinemic clamp (P = 0.042). However, identification of the regulatory pathways leading to the splicing alteration in NIDDM patients requires further investigation.

Alternative Splicing↗
PubMed1993

Structure and chromosomal localization of human insulin-like growth factor-binding protein genes.

The insulin-like growth factor binding proteins (IGFBPs) constitute a structurally related protein family with six known members. We have mapped and regionally localized the genes coding for human IGFBP1, 2, 3, and 4, by in situ hybridization and somatic cell hybrid analysis. The IGFBP2 gene maps to chromosomal region 2q33-q34 whereas the genes for IGFBP1 and 3 are localized in a tail-to-tail fashion on chromosome 7 region p14-p12. The IGFBP4 gene is located in the chromosomal region 17q12-21.1. Structural characterization of the genes coding for IGFBP-1, 2, 3, and 5 showed that the translated parts are divided into four exons. The exons are similar both in size and sequence in all studied genes.

Amino Acid Sequence↗
PubMed1992

Steroid 21-hydroxylase deficiency: three additional mutated alleles and establishment of phenotype-genotype relationships of common mutations.

Lesions in the gene encoding steroid 21-hydroxylase [steroid hydrogen-donor: oxygen oxidoreductase (21-hydroxylating), EC 1.14.99.10] result in defective adrenal steroid synthesis; the severe forms are known as congenital adrenal hyperplasia. To facilitate complete characterization of mutations in this region of tandemly repeated genes, we have developed selective PCR amplification and direct sequencing of full-length nonpseudogene steroid 21-hydroxylase genes. This technique identifies known mutations, characterizes or excludes unknown mutations, and determines the gene-copy number. Three additional defective alleles were found. A Gly-292----Ser mutation and a frameshift mutation at Arg-484 (GG----C) were identified in patients with severe steroid 21-hydroxylase deficiency. An allele with three additional sequence variations--C----T at 4 bases upstream of translation initiation, Pro-106----Leu, and Pro-454----Ser--were identified in two siblings with late-onset deficiency. Pro-454 is conserved in four species, indicating its importance for normal enzyme function. Functional consequences of individual alleles have been determined in vivo by studying individuals with only one steroid 21-hydroxylase gene. Detailed analyses of clinical data revealed that genotyping could predict the clinical course of the disease. The locations of disease-causing mutations on different haplotypes of the steroid 21-hydroxylase gene region are described.

Adrenal Hyperplasia, Congenital↗
PubMed1992

Spatial distribution of active genes implicated in the regulation of insulin-like growth factor stimulatory loops in human decidual and placental tissue of first-trimester pregnancy.

We have previously shown that the insulin-like growth factor-2 (IGF-2) gene is partially coexpressed with the IGF-1 and -2 receptor genes in proliferative cytotrophoblasts of the human extraembryonic tissue. Here we show that high levels of IGF-2 gene expression are not restricted to the embryonic tissue but can also be found in the decidua compacta. The IGF-2 gene is thus expressed at high levels in the mesenchymal stroma of the decidua to establish potentially short-range communication with primarily IGF-1 receptor-positive mesenchymal stroma cells. Conversely, the glandular and surface epithelia coexpress the IGF-1 receptor and IGF-1 genes, while the IGF-2 gene is not detected above background levels. The potential control mechanisms of these cell-cell signalling pathways were investigated by the analysis of the spatial distribution of active IGF binding proteins (IGFBP) genes. The IGFBP-3 gene is coexpressed with the IGF-2 gene in proliferative cytotrophoblasts of the embryonic placenta. While active IGFBP-1 and -2 genes in our hands cannot be detected in the embryonic placenta, all three IGFBP genes are expressed in complex and overlapping patterns in the decidua compacta. The results are discussed in terms of how the various IGFBP genes may operate in different cell types to restrict IGF local stimulatory pathways.

Blotting, Northern↗
PubMed1992

Localization of the human insulin-like growth-factor-binding protein 4 gene to chromosomal region 17q12-21.1.

Insulin-like growth-factor-binding proteins (IGFBPs) constitute a family of structurally related proteins that specifically bind insulin-like growth factors and modulate their functions. In this study, the chromosomal localization was determined for the gene encoding IGFBP4, i.e. inhibitory-IGFBP. A polymerase chain reaction (PCR) fragment corresponding to the previously published cDNA sequence was used to isolate overlapping cosmid clones. By fluorescent in situ hybridization to metaphase chromosomes, the IGFBP4 gene was then localized to chromosomal region 17q21-21.1. This result was in agreement with PCR analysis of a panel of somatic cell hybrids.

Base Sequence↗
PubMed1992

Contiguous localization of the genes encoding human insulin-like growth factor binding proteins 1 (IGBP1) and 3 (IGBP3) on chromosome 7.

In extracellular fluids the insulin-like growth factors (IGFs) are bound to specific binding proteins (IGBPs). The genes for two members of this protein family have been mapped, the IGBP1 gene to human chromosomal region 7p14-p12 and the IGBP2 gene to region 2q33-q34. In this study, somatic cell hybrid analysis indicated that IGBP3 is also located on chromosome 7. Pulsed-field gel electrophoresis was used to demonstrate the close physical linkage between IGBP1 and IGBP3. Overlapping cosmid clones encompassing these genes were isolated, and restriction endonuclease mapping showed that the genes are arranged in a tail-to-tail fashion separated by 20 kb of DNA. Further characterization of the IGBP1 DNA sequence disclosed a duplication of the intron 3-exon 4 junction within the third intron. In addition, we report RFLPs for ApaLI and TaqI in the IGBP1 locus.

Amino Acid Sequence↗
PubMed1992

Quantitative determination of mdr1 gene expression in leukaemic cells from patients with acute leukaemia.

By using a quantitative RNA-RNA solution hybridisation method, the average number of mdr1 RNA transcripts per cell was measured in total nucleic acid extracts of leukaemic cells from patients with acute leukaemia. The results in different types of leukaemia were (number of patients with detectable mdr1 RNA/total number of patients; median number of transcripts per cell in samples with detectable mdr1 RNA); de novo untreated acute myelocytic leukaemia (AML): 20/44; 0.7, secondary acute myelocytic leukaemia: 8/13; 1.1, acute lymphocytic (ALL) and undifferentiated leukaemia: 5/14; 0.6, relapsed leukaemia: 7/15; 0.7. Forty-six patients with de novo untreated acute leukaemia (AML: n = 34, ALL: n = 12) were evaluable for response to induction chemotherapy. Twelve of 18 patients (67%) with detectable mdr1 RNA levels achieved complete remission compared to 23 of 28 (82%) with undetectable levels (P = 0.40). The remission duration tended to be longer among patients with undetectable mdr1 RNA (P = 0.08). Leukaemic cells were analysed on consecutive occasions in 12 patients. The level of expression increased in four and decreased in two. In conclusion, expression of mdr1 RNA is common in acute untreated leukaemia. However, treatment with cytostatic drugs seems only rarely to increase the proportion of leukaemic cells that express mdr1 RNA. Expression of the mdr1 gene could be one of several equally important factors contributing to drug resistance in acute leukaemia.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Haplotypes of the steroid 21-hydroxylase gene region encoding mild steroid 21-hydroxylase deficiency.

Haplotypes of the complement 4 (C4) and steroid 21-hydroxylase [21-OHase; steroid hydrogen-donor: oxygen oxidoreductase (21-hydroxylating), EC 1.14.99.10] repeated gene complex were studied in nine families with at least one member affected with a mild form of 21-OHase deficiency. DNA probes from different parts of the repeated C4/21-OHase unit were used to follow the segregation of hybridization patterns in the families. Ten structurally distinct haplotypes of the C4/21-OHase gene region were identified, and the encoded phenotype was assigned to 34 of the 36 C4/21-OHase haplotypes. Four structurally different haplotypes with three C4/21-OHase repeat units were found. Eight of the nine haplotypes found with triplications of the C4/21-OHase repeat unit encoded the mild form of 21-OHase deficiency, whereas one particular triplicated haplotype encoded a severe form of the disease. In one case the mild form of 21-OHase deficiency was encoded by a haplotype with a single C4/21-OHase repeat unit. Mild 21-OHase deficiency was predicted in a patient by the presence of a triplicated haplotype. The finding of deranged 21-OHase genes on all triplicated C4/21-OHase haplotypes indicate that most of these common haplotypes carry mutated 21-OHase genes, and thus may cause functional polymorphism of general importance in the population.

Adrenal Hyperplasia, Congenital↗
PubMed1991

Structure and localization of the human insulin-like growth factor-binding protein 2 gene.

Insulin-like growth factor binding proteins (IGFBPs) are extracellular proteins that specifically bind IGF and modulate their effects. The human IGFBP2 gene was studied and shown to be localized to chromosome 2 region q33-q34, by somatic cell hybrid analysis and in situ hybridization. Structural characterization of the gene showed that it consists of four exons with three introns of lengths 27.0, 1.0, and 1.9 kilobase-pairs. Comparison of the encoded protein sequence of each exon in IGFBP1, 2, and 3 reveals the highest amino acid identity, 28%, in exon 1, while the lowest was found in exon 2. However, pairwise sequence comparisons demonstrate 50% identity between the protein sequences encoded by exon 4 in IGFBP1 and 2, while their respective identities with IGFBP3 are only 25 and 30%.

Amino Acid Sequence↗
PubMed1991

DNA haplotype analysis suggests linkage disequilibrium in the human insulin receptor gene.

Haplotypes of the insulin receptor gene were resolved in parents from Scandinavian nuclear families by studying the segregation of seven restriction fragment length polymorphisms (RFLPs). Of 97 unrelated parents, 41 had non-insulin-dependent diabetes mellitus (NIDDM). Considerable linkage disequilibrium in the region of the insulin receptor gene was found. Pairwise non-random associations were found between proximate RFLP sites, indicating the absence of recombinational hot spots between these sites. Thus, association studies between DNA polymorphisms at this locus and disease susceptibility genes could well be feasible in this population. Differences in the distribution of insulin receptor haplotypes were examined between NIDDM patients and healthy subjects. However, the differences observed were not statistically significant.

Adult↗
PubMed1991

Screening for insulin receptor gene DNA polymorphisms associated with glucose intolerance in a Scandinavian population.

The significance of insulin receptor gene variants in the aetiology of Type 2 (non-insulin-dependent) diabetes mellitus has been investigated by analysis of restriction fragment length polymorphisms in a genetically homogeneous Swedish population. Seven polymorphisms were analysed, spanning functionally important regions of the insulin receptor locus. Four of these polymorphisms were mapped more accurately within the gene compared to previous studies. The genotype distribution was compared in 76 Type 2 diabetic patients and 84 healthy control subjects. No significant differences were found in the distribution of genotypes between diabetic and control subjects at the p less than 0.01 level. In order to study the possible association between quantitative measures of glucose metabolism and these DNA polymorphisms, the fasting glucose and insulin concentrations were compared in the different genotype groups of control subjects and mildly diabetic patients treated with diet. No differences in fasting glucose or insulin concentrations were found at the p less than 0.005 level of significance. In conclusion, no significant associations were found between insulin receptor gene DNA polymorphisms and glucose intolerance.

Blood Glucose↗