Coenzyme Q10, exercise lactate and CTG trinucleotide expansion in myotonicdystrophy

Steinert's myotonic dystrophy (DM) is a genetic autosomal dominant disease and the most frequent muscular dystrophy in adulthood. Although causative m utation is recognized as a CTG trinucleotide expansion on 19q13.3, pathogen ic mechanisms of multisystem involvement of DM are still under debate. It h as been suggested that mitochondrial abnormalities can occur in this diseas e and deficiency of coenzyme Q 10 (CoQ10) has been considered one possible cause for this. The aim of this investigation was to evaluate, in 35 DM pat ients, CoQ10 blood levels and relate them to the degree of CTG expansion as well as to the amount of lactate production in exercising muscle as indica tor of mitochondrial dysfunction. CoQ10 concentrations appeared significant ly reduced with respect to normal controls: 0.85 +/- 0.25 vs. 1.58 +/- 0.28 mug/ml (p < 0.05). Mean values of blood lactate were significantly higher in DM patients than controls (p < 0.05) both in resting conditions (2.9 +/- 0.55 vs. 1.44 +/- 1.11 mmol/L) and at the exercise peak (6.77 +/- 1.79 vs. 4.90 +/- 0.59 mmol/L), while exercise lactate threshold was anticipated (3 0-50% vs. 60-70% of the predicted normal maximal power output, p, < 0.05). Statistical analysis showed that serum CoQ10 levels were significantly (p < 0.05) inversely correlated with both CTG expansion degree and lactate valu es at exercise lactate threshold level. Our data indicates the occurrence o f reduced CoQ10 levels in DM, possibly related to disease pathogenic mechan isms associated with abnormal CTG trinucleotide amplification. (C) 2001 Els evier Science Inc.