Pyruvate metabolism in Friedreich's ataxia.

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.