Creatine corrects muscle P-31 spectrum in gyrate atrophy with hyperornithinaemia

Background Eye fundus destruction and type II muscle fiber atrophy in gyrat e atrophy of the choroid and retina with hyperornithinaemia (GA) may be med iated by elevated ornithine concentrations which strongly inhibit creatine biosynthesis. This results in deficiency of creatine phosphate (PCr), a key intracellular energy source, as we have demonstrated in skeletal muscle of the patients by P-31 magnetic resonance spectroscopy (P-31 MRS). Materials and methods Possible correction of the relative PCr deficiency by long-term daily exogenous supplementation of creatine or its precursors wa s investigated in four GA patients receiving creatine and in five patients treated with guanidinoacetic acid-methionine combination. The relative PCr concentration, expressed as PCr/P-i (P-i; inorganic phosphate) or as PCr/AT P ratios, was compared with the values of untreated GA patients, and matche d healthy volunteers. Results Muscle PCr/Pi ratios (mean +/- SD) of the untreated and creatine su pplemented GA patients and controls were 4.9 +/- 1.4, 7.9 +/- 0.4 and 8.4 /- 1.3. Guanidinoacetate-methionine combination was similarly effective (re spective PCr/Pi ratios: 4.9 +/- 0.7, 6.3 +/- 1.1 and 10.7 +/- 2.8). Conclusion Supplementation with creatine or creatine precursors almost norm alised low muscle PCr/Pi ratios of patients with GA.