Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016719 (Friedreich's ataxia)
 2,098 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There is now a great deal of evidence to link genetic defects of pyruvate metabolism to brain disease. Experimental evidence is reviewed in Chapter 12, and clinical evidence has been reviewed above. Severe lesions of components of the pyruvate dehydrogenase complex are associated with severe generalized brain disease, and milder defects with inherited ataxias. Nearly half of one series of our ataxic patients had deficient activity of pyruvate dehydrogenase, and 40% of another series have deficient activity of the lipoamide dehydrogenase component. This last group corresponds to 60% of the patients with Friedreich's ataxia and its clinical variants at UCLA. There is an association between defective activity of lipoamide dehydrogenase and disease, and the data suggest there is a structural mutation of the gene for the enzyme. Preliminary studies suggest that obligate heterozygotes as a group have enzyme activities between those for controls and those for patients. Moreover, the obligate heterozygotes from families in which there are kinetic defects of lipoamide dehydrogenase also appear to have kinetic abnormalities of the enzyme. The ataxic patients with reduced lipoamide dehydrogenase activity currently fall into two clinical groups. One is ragged-red ataxia, and the other is a disorder that is a subgroup of the classic Friedreich's ataxia syndrome. Studies need to be undertaken on a larger group of patients, with more diverse inherited ataxias, to test the present clinical associations of the enzyme defect. A dietary treatment derived from a knowledge of the presumed defect has modified the ataxia that is associated with defects of pyruvate decarboxylase, but the diet has not yet been tested with defects of lipoamide dehydrogenase.
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PMID:Evidence for a primary defect of lipoamide dehydrogenase in Friedreich's ataxia. 10 55

The activity of lipoamide dehydrogenase and two closely related enzymes was studied simultaneously in early, mild, and late passage fibroblast cultures. Friedreich's ataxia fibroblasts tended to lose pyruvate dehydrogenase and citrate synthase activities, while lipoamide dehydrogenase activity remained constant with aging of the cells. Mean pyruvate dehydrogenase activity was lower over-all in fibroblasts from ataxics. Mean citrate synthase activity was higher in ataxic fibroblasts. Present tissue culture media do not represent the best conditions in which to reproduce cofactor binding defects such as those found in other genetic diseases with structural enzyme mutations.
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PMID:Pyruvate dehydrogenase, lipoamide dehydrogenase and citrate synthase activity in fibroblasts from patients with Friedreich's and Charlevoix-Saguenay ataxia. 48 17

This overview summarizes the investigations carried out during the second part of Phase Two of the Quebec Cooperative Study of Friedreich's Ataxia. These investigations outline in more details the fundamental role played by an abnormality in the fatty acid composition (deficient linoleic acid, 18:2) of the cholesterol esters of high density lipoproteins (HDL) in the phenotypic expression of the disease. They postulate a defective incorporation of linoleic acid to surface phosphatidylcholine of chylomicrons and consequent relative and absolute decreases in lipoprotein protein components because of overpacking with defective cholesteryl esters. Secondarily to these changes, the postulated lack of activation of the lipoamide dehydrogenase (LAD) of the pyruvate dehydrogenase (PDH) complex could result in slow pyruvate oxidation, glucose intolerance, deficient synthesis of acetylcholine, and depletion of glutamic and aspartic acid pools. In parallel, abnormal phosphatidyl-choline molecules could be incorporated to membranes, resulting in specific defects in some functions of these membranes, including transport of calcium and/or taurine and myelinization. The framework of an understanding of Friedreich's ataxia is now available, but much fundamental and clinical work remains to be done to fill in and prove each one of these postulated steps.
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PMID:Friedreich's ataxia 1979: an overview. 48 23

Two unrelated patients with Friedreich ataxia were deficient in the activity of the enzyme lipoamide dehydrogenase (LAD). The enzymes from the patients' platelets differed significantly from controls in activity, in KM for lipoamide, and in KM for NADH. The data are consistent with a structural mutation of the gene coding for LAD.
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PMID:Kinetic evidence for a structural abnormality of lipoamide dehydrogenase in two patients with Friedreich ataxia. 56 87

Pyruvate dehydrogenase (PDH), alpha-keto glutarate dehydrogenase (alpha-KGDH) and lipoamide dehydrogenase (LAD) were measured in platelets of 11 patients with typical Friedreich's ataxia and 10 normal control subjects. Serum LAD was also evaluated in the same patients. No statistically significant changes were found in platelets for the group as a whole, although some patients had low values (more than one standard deviation below control mean). Serum LAD was significantly reduced in the patients with Friedreich's ataxia. This was not due to associated diabetes.
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PMID:Serum and platelet lipoamide dehydrogenase in Friedreich's ataxia. 64 85

Lipoamide dehydrogenase was identified in cultured skin fibroblasts of normal individuals and patients with Friedreich's ataxia. The optimum conditions for its assay were defined. Data disclosed a normal range of 36--122 mumol/min/mg protein in control fibroblasts and 61--112 mumol/min/mg protein in patients fibroblasts. Numerous precautions should be taken in handling fibroblast cultures for lipoamide dehydrogenase determination.
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PMID:Lipoamide dehydrogenase in cultured human skin fibroblasts. 66 42

Friedreich's ataxia patients show evidence of an abnormally elevated and prolonged response of pyruvate and lactate to a glucose load, with normal fasting levels. However, ther is a bimodal distribution of this response with high and low pyruvate responders. This trait appears to be determined genetically, However, although in vivo tests suggest low oxidation of pyruvate, we were unable to confirm any in vitro impairment of each of the components of the pyruvate dehydrogenase (PDH) complex. We conclude that the defect is in the metabolic regulation of PDH, probably at the E3 (lipoamide dehydrogenase) step.
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PMID:Pyruvate metabolism in Friedreich's ataxia. 100 Apr 25

Muscle pyruvate dehydrogenase complex (PDHC) activity was studied in 70 patients with different neuromuscular disorders. Children had higher total PDHC and lipoamide dehydrogenase (LAD) activities than adults. There were no significant differences in muscle PDHC activity in patients with Friedreich ataxia, patients with other ataxias, or age-matched controls. Kinetic analysis of LAD showed no differences in Km for lipoamide between Friedreich ataxia patients and controls.
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PMID:Human muscle pyruvate dehydrogenase activity. 668 64

To see whether kinetic assays of lipoamide dehydrogenase could be used for carrier detection or preclinical diagnosis, Michaelis-Menten constants (KmL and KmH) for the enzyme were determined in platelets from families with a form of recessive Friedreich ataxia and low activities of the enzyme. The KmL of patients' enzyme was 132 +/- 5 microM lipoamide (mean +/- SEM) versus 56 +/- 9 microM for controls (p less than 0.001), and KmH for the patients was 421 +/- 19 microM versus 147 +/- 14 microM for the controls (p less than 0.001). The activity and Km values of one patient's enzyme were abnormal 1 year before neurologic signs appeared. The Km values for the enzymes of the six parents were also elevated (average KmL, 105 +/- 10 microM; average KmH, 378 +/- 47 microM, p less than 0.02). The maximal activities of the parents' enzymes, relative to a mitochondrial marker, were intermediate between the mean maximal control activity and the mean activity for the affected offspring. The data suggest that the abnormalities of lipoamide dehydrogenase are inherited in a recessive pattern in these families.
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PMID:Preclinical diagnosis and carrier detection in ataxia associated with abnormalities of lipoamide dehydrogenase. 689 25

This study extends previous observations of pyruvate metabolism in the spino-cerebellar degenerations by screening for abnormalities of pyruvate oxidation using the rise in blood pyruvate after an oral glucose load and examining the activity of the lipoamide dehydrogenase (LAD) moeity of the pyruvate dehydrogenase complex in the serum of 31 patients with Friedreich's ataxia, hereditary spastic ataxia and primary cerebellar degeneration. Serum LAD activity was significantly reduced in 10 Friedreich's ataxia patients when compared to controls and to 10 patients with spastic ataxia, thus confirming previous studies. Two patients with Friedreich's ataxia and 2 with primary cerebellar degeneration had abnormal blood pyruvate curves after oral glucose loading. The findings suggest that abnormal pyruvate oxidation occurs in some cases of Friedreich's ataxia and primary cerebellar degeneration and that the abnormality of pyruvate metabolism is not necessarily reflected in the serum LAD activity of these patients. The relevance of these findings to the heterogeneity of the hereditary ataxias is discussed.
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PMID:An investigation of pyruvate metabolism in patients with cerebellar and spinocerebellar degeneration. 689 66


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