Detection of mitochondrial DNA mutations in patients with diabetes mellitus.
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DNA, Mitochondrial↗
Biomedical subjects
J C Alcolado
Publications and source records attributed to J C Alcolado.
Maternally inherited diabetes mellitus: the role of mitochondrial DNA defects.
Several studies have shown a consistent maternal effect in the transmission of Type 2 diabetes (NIDDM). The mitochondrial encephalomyopathies are a group of diseases characterized by maternal inheritance and a variety of mitochondrial DNA defects. Diabetes is a feature of some of these disorders and therefore the hypothesis arose that mitochondrial DNA mutations might play a role in patients with diabetes but no other features of neurological disease. Recent studies have confirmed that a specific point mutation in the gene encoding the mitochondrial tRNA for leucine segregates with diabetes and nerve deafness in families from the UK, Holland, France and Japan. Mitochondrial gene deletions have also been reported. Affected subjects present with progressive insulin deficiency and may fall into the broad classifications of either Type 1 (IDDM) or Type 2 diabetes (NIDDM). Future studies are aimed at searching for other mitochondrial gene defects in diabetes and attempting to explain the mechanism of hyperglycaemia by the development of phenotypic expression systems. Although an exciting development in the genetics of diabetes, currently described mitochondrial mutations do not fully explain the maternal effect in the transmission of Type 2 diabetes.
DNA, Mitochondrial↗
Insulin resistance and impaired glucose tolerance.
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DNA, Mitochondrial↗
Affected sib-pair analysis of the GLUT1 glucose transporter gene locus in non-insulin-dependent diabetes mellitus (NIDDM): evidence for no linkage.
Despite the strong evidence for a major role played by genetic factors in the aetiology of non-insulin-dependent diabetes mellitus (NIDDM), the genes involved are still unknown. Association studies of candidate genes for the inheritance of NIDDM have so far yielded inconclusive results. Some evidence exists for an association between NIDDM and the glucose transporter gene GLUT1, involved in basal glucose transport, although this has not been confirmed. In the present study we have tested the hypothesis of linkage between NIDDM and the GLUT1 gene, using affected sib-pairs. With this method the concordance observed for a given gene marker is compared with that expected under the assumption of no linkage between that marker and the disease. Fifty-four pedigrees (22 Italians and 32 British), for a total of 82 sib-pairs were studied by the affected sib-pair method proposed by Weeks and Lange, using two restriction fragment length polymorphisms (RFLPs) at the GLUT1 locus, the MspI RFLP, at an estimated 0.171 recombination frequency from the GLUT1 gene, and the XbaI RFLP, located within the GLUT1 gene and previously shown to be associated with the disease. Results showed that the MspI marker and NIDDM segregate independently; for the XbaI RFLP, linkage could be shown only if the results were weighted by the allele frequency [f(p) = 1/p], and only in the Italian and the combined (Italian and British) sib-pair groups. Multilocus analysis with both markers was also negative. We conclude that the GLUT1 gene is very unlikely to play a major role in the aetiology of NIDDM, although an accessory role cannot be excluded, and studies of the gene sequence should help to clarify this question.
Chromosome Mapping↗
Selection of control subjects in genetic studies of diabetes mellitus.
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Case-Control Studies↗
Mitochondrial gene defects in patients with NIDDM.
Non-insulin-dependent diabetes mellitus (NIDDM) has a strong genetic component and maternal factors have recently been implicated in disease inheritance. The mitochondrial myopathies are a group of diseases which often show maternal inheritance as a result of mtDNA defects; some patients have impaired glucose tolerance. Occasional families with maternally inherited diabetes and deafness associated with a deletion or point mutation of mtDNA have been reported. To assess the importance of mitochondrial gene defects in NIDDM, 150 unrelated diabetic subjects from Wales, UK and 68 unrelated patients with diabetes and at least one affected sibling from England, UK were studied. Southern blot analysis did not show any large mtDNA deletions or duplications. One patient had a mutation in the mitochondrial tRNAleu(UUR) gene at bp 3243. This mutation is commonly associated with the syndrome of mitochondrial encephalomyopathy, lactic acidosis and stroke like episodes (MELAS). Study of this patient and his siblings showed a distinct form of late-onset diabetes associated with nerve deafness but no clinical features of the MELAS syndrome. No diabetic subject was shown to have the mtDNA mutation at position 8344 (tRNA(lys)) which has previously been described in the syndrome of mitochondrial encephalomyopathy and red-ragged fibres (MERRF). The role of other mitochondrial gene defects in diabetes and the pathophysiological basis of glucose intolerance in patients with the MELAS mutation requires further elucidation.
Base Sequence↗
Variability of plasma apolipoprotein (apo) A-II levels associated with an apo A-II gene polymorphism in monozygotic twin pairs.
A dimorphic MspI RFLP (alleles M1 and M2) in an Alu unit 528 base pairs downstream from the apolipoprotein A-II gene on chromosome 1 was investigated for associations with dyslipoproteinaemia or coronary atherosclerosis. No significant differences were observed between the allele frequencies in healthy random controls (M2 = 0.850, n = 70) and patients with primary hypertriglyceridaemia (M2 = 0.846, n = 52) or severe coronary atherosclerosis (M2 = 0.819, n = 47). The apolipoprotein A-II gene may also contribute to the regulation of plasma levels or composition of HDL in response to environmental changes. To study the effect upon apolipoprotein A-II variability, 42 monozygotic twin pairs were genotyped for the MspI RFLP. Pairs with the genotype M2M2 (n = 28) had significantly smaller within-pair differences in plasma apolipoprotein A-II levels (2.2 vs 5.8 mg/dl, P < 0.02; Mann-Whitney) than those with other genotypes (n = 14). The M2 allele may be in linkage disequilibrium with a functional mutation that restricts the variability of plasma apolipoprotein A-II in response to environmental conditions. This provides a new example of a 'variability' gene, one of an important group of loci which may alter responses to hypolipidaemic therapy and cardiovascular risk.
Adult↗
Mitochondrial DNA defects in diabetes mellitus.
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DNA, Mitochondrial↗
Malignant change in dermatitis artefacta.
Dermatitis artefacta is a chronic skin lesion produced by self-trauma. Avoidance of further trauma, topical steroids and psychological therapy all play a part in the treatment of such lesions. Unresolved lesions may become large and disfiguring and subject to infection. We report a case of one such lesion in an elderly woman who persistently excoriated a cholecystectomy scar over 40 years. Malignant transformation occurred in a manner analogous to the neoplastic change observed in other types of chronic ulcer (Marjolin's ulcer). The squamous cell carcinoma presented with widespread metastases from which the patient eventually died. Recent literature concerning Marjolin's ulcers is reviewed and it is noted that this is the first reported case of death caused by malignant change in dermatitis artefacta.
Aged↗
Polymorphisms at the GLUT2 (beta-cell/liver) glucose transporter gene and non-insulin-dependent diabetes mellitus (NIDDM): analysis in affected pedigree members.
The precise genetic defects underlying the etiology of non-insulin-dependent diabetes mellitus (NIDDM) have yet to be identified. The beta-cell/liver glucose transporter gene GLUT2 represents a good candidate for the etiology of the disease, being involved in the glucose signalling for beta-cell insulin release. Population association studies of the GLUT2 gene in NIDDM have so far yielded controversial results. In order to determine the possible contribution of this gene to the inheritance of NIDDM, we have employed a new approach, where two polymorphic markers of the GLUT2 locus, detected with the restriction enzyme Taq-1, were examined for linkage with the disease in a group of 22 Italian pedigrees with affected members (n = 50). Departure from independent segregation between markers and disease was analyzed by the Affected-Pedigree-Members (APM) statistical method. Furthermore, association analysis between the Taq-1 RFLPs at the GLUT2 locus and NIDDM was performed in a group of diabetics with a strong family history, comprising the 22 probands and 23 other diabetics with an affected first-degree relative. The results indicate that there was no segregation distortion between the Taq-1 markers of the GLUT2 gene and the disease in the pedigrees examined. Also, no significant difference in genotype distribution, haplotype and allele frequencies was found between diabetics and controls for the two Taq-1 RFLPs. We conclude that genetic variation at the GLUT2 transporter gene is unlikely to contribute in a major way to the inheritance for NIDDM in this Italian population.
Aged↗
Risk factors for peripheral vascular disease in hypertensive subjects with type 2 diabetes mellitus.
Possible factors predisposing to peripheral vascular disease (PVD) in hypertensive subjects with Type 2 diabetes mellitus were studied. Details of age, sex, duration of diabetes, blood pressure, and smoking habit were recorded in 180 subjects of either White, West Indian Black or Asian ethnic origin. Glycosylated haemoglobin, fasting serum total cholesterol, total high density lipoprotein (HDL), HDL2, low density lipoprotein (LDL-cholesterol), and triglycerides were measured in all subjects. Peripheral vascular disease was defined as an ankle/brachial systolic pressure < 1.0 as measured by the Doppler technique. Multivariate analysis was performed and the following factors were identified as being strongly associated with the presence of PVD with a statistical significance of p < 0.001; LDL-cholesterol, total HDL-cholesterol, age, male sex, diet or oral hypoglycaemic therapy, diastolic blood pressure, and of p < 0.003; systolic blood pressure. When blood pressure was excluded from the analysis the other factors retained their predictive value. We conclude that hypertension and dyslipidaemia are important risk factors for peripheral vascular disease in Type 2 diabetes mellitus.
Blood Pressure↗
Sib-pair analysis of adenosine deaminase locus in NIDDM.
Recently, linkage between the ADA gene locus and MODY, a subtype of NIDDM, has been reported. The possibility that the region of chromosome 20q containing the ADA locus also may play a role in susceptibility to NIDDM needs to be investigated. Therefore, we examined the linkage between the ADA locus and NIDDM in affected siblings of 50 European white diabetic pedigrees--21 Italian and 29 British. Departure from independent segregation of the disease and an Alu VpA polymorphism within the 5' flanking region of the ADA locus was tested in the affected sib-pairs with the APM statistical method. After DNA amplification by the PCR and PAGE, five alleles were identified in the ALU VpA tract at the ADA locus in the two populations. Allele frequencies did not differ significantly between the two populations (chi 2 = 2.426, P > 0.05 [NS]). Analysis of the 50 diabetic sib sets, and independently of the Italian and British groups of affected sib pairs, revealed no segregation distortion between the marker locus and NIDDM. We conclude that mutations within or around the ADA locus are unlikely to play a major role in the etiology of NIDDM.
Adenosine Deaminase↗
Genetic polymorphisms at the human liver/islet glucose transporter (GLUT2) gene locus in Caucasian and West Indian subjects with type 2 (non-insulin-dependent) diabetes mellitus.
The liver/islet glucose transporter (GLUT2) is mainly expressed in the hepatocytes of the liver and the beta-cells of the pancreatic islets and a defect in this transporter could lead to diabetic phenotypes, such as relative hypoinsulinaemia and reduced uptake and metabolism of glucose in the liver. DNA from unrelated individuals was digested with the restriction endonucleases Bgl-I and Taq-I followed by blotting and hybridisation with a 32P-labelled GLUT2 cDNA which revealed three restriction fragment length polymorphisms (RFLPs) (B1, T1 and T2) in both Caucasian and West Indian populations. Linkage analysis between these variant sites demonstrated that the alleles of these polymorphisms were in strong linkage disequilibrium. Disease association of genetic variants at the GLUT2 locus with type 2 diabetes was examined with these RFLPs in both Caucasian (n = 54) and West Indian (n = 46) populations with type 2 diabetes. There were no significant differences in the frequency of alleles, genotypes or haplotypes between diabetic patients and non-diabetic controls. However, there were significant differences in the allele frequencies of all these three polymorphisms between Caucasian and West Indian populations.
Aged↗
Importance of maternal history of non-insulin dependent diabetic patients.
OBJECTIVE: To assess the family history of diabetes in non-insulin dependent diabetes mellitus with particular emphasis on parental phenotype. DESIGN: Family histories were obtained from an existing computerised database and supplemented by postal questionnaires. SETTING: Diabetic service of a provincial teaching hospital. SUBJECTS: A total of 1326 patients with non-insulin dependent diabetes who had been referred to diabetic clinics over the past 10 years and from whom data had been collected for inclusion in the database, of whom 347 had affected first degree relatives. Nineteen non-white patients were excluded because of the differential hereditability of the disease, and 230 (70%) patients with an affected first degree relative responded to the postal questionnaire. RESULTS: Mothers were implicated in significantly more cases than fathers in patients with a single affected parent: 125 mothers and 48 fathers from database; 82 mothers and 34 fathers from postal questionnaire; p less than 0.001 in both cases. CONCLUSIONS: Maternal influences seem to have an important role in the inheritance of non-insulin dependent diabetes.
Adult↗
Association between a restriction fragment length polymorphism at the liver/islet cell (GluT 2) glucose transporter and familial type 2 (non-insulin-dependent) diabetes mellitus.
Patients with Type 2 (non-insulin-dependent) diabetes mellitus and a strong family history of the disease may represent a sub-group where genetic factors play a preeminent role in transmission of the disease. A defect in the liver/islet cell glucose transporter (GluT 2) could explain many of the pathophysiological features of the disease. In order to test the hypothesis that genetic variation at the GluT 2 locus contributes genetic susceptibility to Type 2 diabetes, 60 unrelated Caucasian diabetic patients with at least one affected sibling were genotyped for a Taq 1 restriction fragment length polymorphism marker. Hybridisation with a cDNA GluT 2 probe identified two alleles of sizes 13 kilobase (T1) and 19 kilobase (T2). The allele frequencies in the diabetic group with a family history were significantly different from those in a racially-matched control population of 122 subjects with no personal or family history of the disease (diabetic patients T1 = 0.96, T2 = 0.04, control subjects T1 = 0.89, T2 = 0.11, p less than 0.03). However, when the study was repeated with 54 diabetic patients with indeterminate family history, statistical significance was not reached although the allele frequencies showed a similar trend. The findings of this study support the hypothesis that a genetic variant of the liver/islet cell glucose transporter may contribute to familial susceptibility in Type 2 diabetes.
Alleles↗
Lipoprotein and hepatic lipase gene variants in coronary atherosclerosis.
Lipoprotein lipase is the rate determining enzyme for the removal of triglyceride rich lipoproteins from the blood stream. We examined whether genetic variation at the lipoprotein lipase gene locus is related to the occurrence of premature coronary artery disease. Two restriction fragment length polymorphisms, revealed by the enzymes HindIII and PvuII, demonstrated alleles designated H1 (17.5 kb), H2 (8.7 kb), P1 (7.0 kb), P2 (4.4 kb and 2.5 kb) respectively. These were studied in 70 Caucasian subjects with severe coronary atherosclerosis in comparison with 122 Caucasian healthy controls. The allelic frequencies for cases and controls were respectively: H2 0.770, 0.579 (P less than 0.001); P2 0.575, 0.554 (P NS). The allelic frequencies of the HindIII and BglII polymorphic sites at the hepatic lipase gene locus were also studied in the same groups of subjects. These showed no differences between cases and controls. We conclude that DNA variation at or adjacent to the lipoprotein lipase gene may contain genetic determinants for the occurrence of premature coronary artery disease.
Alleles↗
Calcification in the human choroid plexus, meningiomas and pineal gland.
Calcification in the stroma of adult telencephalic choroid plexus was studied of 20 postmortem brains and one biopsy by light microscopy, transmission and scanning electron microscopy and compared with calcification in psammoma bodies in normal arachnoid, five spinal meningiomas and in calcospherites of six pineal glands. Fifteen fetal and newborn choroid plexuses were also examined by light microscopy. Calcium deposition was observed in the subepithelial regions of the adult choroid plexus, in the walls of blood vessels but was mostly seen in spherical psammoma bodies. Collagen whorls 20-60 microns in diameter and surrounded by arachnoid cells, were observed in the stroma of the choroid plexus; calcium, phosphorous and iron were deposited in the collagen whorls to form psammoma bodies. Matrix vesicles and spicules resembling hydroxyapatite were associated with the arachnoid cells surrounding the collagen whorls and with the collagen fibres within the whorls. The dense amorphous calcified core of each psammoma body was surrounded by an outer coating of entwined collagen fibres readily visible by scanning electron microscopy. Similar psammoma bodies were occasionally observed in normal arachnoid. Psammoma bodies in meningiomas resembled those in the choroid plexus stroma. Calcospherites in the pineal differed from psammoma bodies; they were lobulated, more irregular in shape and did not have a collagen base. The results of this study suggest that psammoma bodies in the choroid plexus, as in meningiomas, form by a process of dystrophic calcification associated with arachnoid cells and collagen fibres. The presence of iron in the choroid plexus psammoma bodies may be a result of haemorrhage into the stroma. The mechanism of calcification in pineal remains unclear.
Adult↗