Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the pancreas of diabetic patients with the A-to-G mitochondrial DNA (mtDNA) mutation at nucleotide position 3243 base pair (bp) have not previously been described. The clinical phenotypes of diabetes associated with the mtDNA 3243 mutation range from NIDDM to IDDM. We sought the presence of the mutation and studied volume of beta-, alpha-, and delta-cells, mitochondrial enzyme activity, and presence of apoptosis in diabetic pancreases obtained at autopsy. Pancreases were obtained from 16 patients with IDDM, from 18 patients with NIDDM, and from 11 nondiabetic patients. Mitochondrial enzyme activity was determined for cytochrome c oxidase (COX), the subunits of which are partially encoded by mtDNA, and for succinate dehydrogenase (SDH), the subunits of which are solely encoded by nuclear DNA. The volumes of islet beta-, alpha-, and delta-cells were estimated by computerized morphometry. Pancreatic cells were examined for apoptosis by an in situ end-labeling procedure. The mtDNA 3243 mutation was detected in 1 of 16 (6%) pancreases from the IDDM patients; none of the pancreases from 18 NIDDM patients and 11 nondiabetic patients had the mutation. The single patient with the mtDNA 3243 mutation was a 56-year-old woman with IDDM, aged 39 years at diabetes onset, whose mother was diagnosed with NIDDM. The patient had a history of secondary failure of oral hypoglycemic agents and had a marked decrease in the number of beta-cells. The islet beta-cells and non-beta-cells of the patient showed extremely decreased COX enzyme activity. The islet cells in the patient showed a high activity when examined for SDH. Some pancreatic exocrine cells also showed decreased COX activity with high SDH activity. In IDDM, NIDDM, and nondiabetic patients without the mtDNA 3243 mutation, only weak staining for SDH of the islet cells showed. The percentage of heteroplasmy of the mtDNA 3243 mutation in pancreatic micropunched islet specimens was 63 +/- 5% (mean +/- SD) in the islets, 32 +/- 3% in the exocrine pancreas, and 8 +/- 1% in peripheral polymorphonuclear cells. Apoptotic cells were not observed in the IDDM pancreas in the patient with the mtDNA 3243 mutation. The fact that higher levels of mutated mtDNA at 3243 bp were found in affected islets rather than in other tissue suggests that the distribution of the mutant may determine the effect on islet function. A characteristic decrease in the mitochondrial enzyme with COX activity and accelerated SDH activity of the affected islets may provide new insights into the pathogenesis of mitochondrial diabetes.
Diabetes 1997 Oct
PMID:In situ characterization of islets in diabetes with a mitochondrial DNA mutation at nucleotide position 3243. 931 51

Changes of enzyme activities in the myocardium of rats from 6 different experimental groups (normal rats, diabetic rats, hypoxic diabetic rats, each with and without Ginkgo biloba extract treatment) were measured by using both cytophotometric and biochemical methods. The activity of succinate dehydrogenase, a marker of oxidative capacity, and of menadione-dependent glycerol-3-phosphate dehydrogenase and total lactate dehydrogenase, both markers of glycolytic capacity were measured to characterize changes of the metabolic profile in myocardium. A strong correlation between cytophotometric and biochemical data were found by linear regression analysis, justifying the use of cytophotometrical enzyme activity measurements in cells of organized tissue, where biochemistry cannot provide topographical information. The comparison of the results obtained from the different groups revealed the following: Enzyme activities in the myocardium of rats with streptozotocin-induced diabetes were significantly increased by 10-30% as compared to the normal myocardium. This effect was interpreted as a metabolic compensation of the diabetic heart with reduced performance. When diabetic rats were exposed to acute hypoxia of 20 min duration, enzyme activities decreased under the normal level, to 56% of the succinate dehydrogenase activity, to 87% of glycerol-3-phosphate dehydrogenase activity and to 69% of lactate dehydrogenase activity. Treatment of rats with the oxygen radical scavenger Ginkgo biloba extract (EGb 761) over 3 months resulted primarily in an increase by 10% of oxidative capacity and in a decrease by 30% of glycolytic capacity. Under diabetic conditions a shift to more glycolytic metabolism was observed by increasing the glycolytic activity by 39% and remaining the oxidative activity.
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PMID:The correlation of cytophotometrically and biochemically measured enzyme activities: changes in the myocardium of diabetic and hypoxic diabetic rats, with and without Ginkgo biloba extract treatment. 938 12

Mutations of mitochondrial DNA (mtDNA) are associated with a wide spectrum of disorders encompassing the myopathies, encephalopathies and cardiomyopathies, in addition to organ specific presentations such as diabetes mellitus and deafness. The pathogenesis of mtDNA mutations is not fully understood although it is assumed that their final common pathway involves impaired oxidative phosphorylation. The identification of a specific respiratory chain defect (complex I deficiency) in Parkinson's disease (PD) 10 years ago focused attention on the aetiological and pathogenetic roles that mitochondria may play in neurodegenerative diseases. There is evidence now emerging that mtDNA abnormalities may determine the complex I defect in a proportion of PD patients and it may prove possible to use biochemical analysis of platelet and cybrid complex I function to identify those that lie within this group. Respiratory chain defects of a different pattern have been identified in Huntington's disease (HD) (complex II/III deficiency) and Friedreich's ataxia (FA) complex I-III deficiency). In both these disorders, the mitochondrial abnormality is secondary to the primary nuclear mutation:CAG repeat in the huntingtin gene in HD, and GAA repeat in the frataxin gene in FA. Nevertheless, it appears that the mitochondrion may be the target of the biochemical defects that are the consequence of these mutations. There is a close and reciprocal relationship between respiratory chain dysfunction and free radical generation, and there is evidence for oxidative stress and damage in PD, HD and FA, which together with the mitochondrial defect may result in cell damage. Impaired oxidative phosphorylation and free radical generation may independently adversely affect the maintenance of mitochondrial transmembrane potential (Deltapsim). A fall in Deltapsim is an early event (preceding nuclear fragmentation) in the apoptotic pathway. It is possible therefore that mitochondrial dysfunction in the neurodegenerative disorders may result in a fall in the apoptotic threshold of neurones which, in some, may be sufficient to induce cell death whilst, in others, additional factors may be required. In any event, mitochondria present an important target for future strategies for 'neuroprotection' to prevent or retard neurodegeneration.
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PMID:Mitochondrial dysfunction in neurodegenerative disorders. 971 16

To address the problem of the pathogenesis in diabetic neuropathy, rats were made diabetic by streptozotocin administration, and discrete brain regions, such as cortex, cerebellum, brainstem, thalamus, and hypothalamus, were sampled for assay of activities of electron transport chain complexes I-IV at 1 and 3 mo after induction of diabetes. Significant decrease was seen in activities of dinitrophenylhydrazine DNPH-coenzyme Q reductase (complex I), coenzyme Q cytochrome-c reductase (complex III), and cytochrome-c oxidase (complex IV) from discrete brain regions with more pronounced changes in complex I. The decline in the complex I, III, and IV activity was more severe in the 3-mo group. Succinate dehydrogenase (SDH) coenzyme Q reductase (complex II), which is an enzyme shared by tricarboxylic acid (TCA) cycle and electron transport chain, showed a significant increase under the same set of conditions. These results suggest that the bioenergetic impairment has an important role in the pathophysiology of diabetes.
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PMID:The impact of diabetes on CNS. Role of bioenergetic defects. 1034 74

We present a boy of eight years of age with symptoms of Kearns-Sayre syndrome (KSS) characterised by ophthalmoparesis, palpebral ptosis, mitochondrial myopathy, pigmentous retinitis, associated to short stature, cerebellar signs, cardiac blockade, diabetes mellitus, elevated cerebrospinal fluid protein concentration, and focal hand and foot dystonia. The skeletal muscle biopsy demonstrated ragged red fibers, cytochrome C oxidase-negative and succinate dehydrogenase-positive fibers. The magnetic resonance imaging showed symmetrical signal alteration in tegmentum of brain stem, pallidum and thalamus. Mitochondrial DNA analysis from skeletal muscle showed a deletion in heteroplasmic condition. The association of dystonia to KSS, confirmed by molecular analysis, is first described in this case, and the importance of oxidative phosphorylation defects in the physiopathogenesis of this type of movement disorder is stressed.
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PMID:Kearns-Sayre syndrome "plus". Classical clinical findings and dystonia. 1068 96

Multiple symmetric lipomatosis (MSL), also known as Launois-Bensaude syndrome or Madelung's disease, is a rare disorder predominantly seen in middle-aged male patients. The disorder is characterized by large subcutaneous fat masses distributed around the neck, shoulders, and other parts of the trunk, often associated with nervous system abnormalities. A close relationship to alcoholism, metabolic disturbances and malignant tumours has been observed. Until now, MSL has only been described in adults. We report on the first two children, a 9-year-old girl and a 13-year-old boy, with the characteristic clinical findings of MSL. The girl presented with severe obesity, developmental delay, mild mental retardation, peripheral neuropathy, and latent hypothyroidism. In addition, she had elevated lactate concentrations in blood and cerebral spinal fluid suggesting mitochondrial dysfunction. Biochemical analyses of muscle showed a respiratory chain complex II deficiency. The boy suffered from severe obesity, mild mental retardation and insulin resistant diabetes mellitus. In both children, analyses of the mitochondrial genome did not reveal major deletions nor the MERRF 8344 point mutation. MSL seems to be a new neurometabolic disorder with heterogeneous clinical expression whose pathogenesis is still unknown.
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PMID:Multiple symmetric lipomatosis: an unusual cause of childhood obesity and mental retardation. 1081 86

Alteration of platelet function contributes to microthrombus formation and may play an important role in the pathogenesis of diabetic micro- and macroangiopathies. However, the molecular mechanism for platelet dysfunction observed in patients with diabetes has not been fully elucidated. In this study, the direct effects of hyperglycemia on platelet function in vitro were investigated. Hyperglycemia increased reactive oxygen species generation in human platelets, and this effect was additive with that of collagen. Thenoyltrifluoroacetone (TTFA), an inhibitor of mitochondrial electron transport chain complex II, and carbonyl cyanide m-chlorophenylhydrazone (CCCP), an uncoupler of oxidative phosphorylation, completely prevented the effects of hyperglycemia, suggesting that reactive oxygen species arise from the mitochondrial electron transport chain. Hyperglycemia potentiated both platelet aggregation and the subsequent release of platelet-derived growth factor AB induced by a nonaggregating subthreshold concentration of collagen, which were also completely inhibited by TTFA or CCCP. Furthermore, hyperglycemia was found to inhibit protein tyrosine phosphatase (PTP) activity and increase phosphorylation of the tyrosine kinase Syk in platelets exposed to collagen. Hyperglycemia-induced PTP inhibition and Syk phosphorylation were found to be completely prevented by TTFA, CCCP, or Mn(III)tetrakis (4-benzoic acid) porphyrin, a stable cell-permeable superoxide dismutase mimetic. These results suggest that hyperglycemia-induced mitochondrial superoxide generation may play an important role in platelet dysfunction observed in patients with diabetes.
Diabetes 2001 Jun
PMID:Hyperglycemia potentiates collagen-induced platelet activation through mitochondrial superoxide overproduction. 1137 52

The secondary signals emanating from increased glucose metabolism, which lead to specific increases in proinsulin biosynthesis translation, remain elusive. It is known that signals for glucose-stimulated insulin secretion and proinsulin biosynthesis diverge downstream of glycolysis. Consequently, the mitochondrial products ATP, Krebs cycle intermediates, glutamate, and acetoacetate were investigated as candidate stimulus-coupling signals specific for glucose-induced proinsulin biosynthesis in rat islets. Decreasing ATP levels by oxidative phosphorylation inhibitors showed comparable effects on proinsulin biosynthesis and total protein synthesis. Although it is a cofactor, ATP is unlikely to be a metabolic stimulus-coupling signal specific for glucose-induced proinsulin biosynthesis. Neither glutamic acid methyl ester nor acetoacetic acid methyl ester showed a specific effect on glucose-stimulated proinsulin biosynthesis. Interestingly, among Krebs cycle intermediates, only succinic acid monomethyl ester specifically stimulated proinsulin biosynthesis. Malonic acid methyl ester, an inhibitor of succinate dehydrogenase, also specifically increased glucose-induced proinsulin biosynthesis without affecting islet ATP levels or insulin secretion. Glucose caused a 40% increase in islet intracellular succinate levels, but malonic acid methyl ester showed no further effect, probably due to efficient conversion of succinate to succinyl-CoA. In this regard, a GTP-dependent succinyl-CoA synthetase activity was found in cytosolic fractions of pancreatic islets. Thus, succinate and/or succinyl-CoA appear to be preferential metabolic stimulus-coupling factors for glucose-induced proinsulin biosynthesis translation.
Diabetes 2002 Aug
PMID:Succinate is a preferential metabolic stimulus-coupling signal for glucose-induced proinsulin biosynthesis translation. 1214 63

We report on a unique patient with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) presenting optic atrophy, cardiomyopathy, and bilateral striatal necrosis before stoke-like episodes became apparent. Skeletal muscle total mitochondrial DNA analysis identified a heteroplasmic A to G point mutation in the tRNA(Lys) gene at position 8296. Skeletal muscle pathology revealed typical MELAS findings, including ragged-red fibers cytochrome c oxidase positive strongly succinate dehydrogenase-reactive blood vessels. Recent reports describe the 8296 mutation identified in patients with diabetes mellitus or myoclonus epilepsy with ragged-red fibers, not MELAS. We conclude that the 8296 mutation is likely to be pathogenic and that it may be not only a mutation responsible for diabetes mellitus or myoclonus epilepsy with ragged-red fibers but also for MELAS.
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PMID:Atypical MELAS associated with mitochondrial tRNA(Lys) gene A8296G mutation. 1250 10

The aim of the present study was to investigate the effects of dietary supplementation with the pyridoindole antioxidant stobadine on histochemical parameters in kidney of streptozotocin-induced diabetic rats. Diabetic male Wistar rats were fed a standard diet or a diet supplemented with stobadine (0.05% w/w) for 24 weeks. The diabetic state was characterized by significantly elevated plasma levels of glucose and glycated hemoglobin, severe reduction of total body weight and relatively enlarged kidneys. Kidney alkaline phosphatase activity was not changed by diabetes. Activity of 5'-nucleotidase, K(+)-dependent p-nitrophenylphosphatase, ATPase and mitochondrial succinic dehydrogenase were markedly decreased in kidneys of diabetic rats. In contrast, activity of beta-hydroxybutyrate dehydrogenase was moderately increased in kidney of diabetic rats as compared to controls. Long-term treatment of diabetic animals with stobadine attenuated histochemical changes in kidney tissue.
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PMID:The pyridoindole antioxidant stobadine attenuates histochemical changes in kidney of streptozotocin-induced diabetic rats. 1255 12


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