Determination of urinary myo-inositol concentration by an improved enzymatic cycling method using myo-inositol dehydrogenase from Flavobacterium sp

Background: To determine myo-inositol more accurately, we improved the enzymatic cycling method. Methods: We screened myo-inositol dehydrogenase (MIDH; EC.1.1.1.18) from Flavobacterium sp., which was highly specific to myo-inositol. We measured urinary myo-inositol/creatinine ratio 2 h after 75-g oral glucose tolerance test (2 h MI) of 71 volunteers, and investigated the relationship between diabetes and urinary myo-inositol concentration. Results: The calibration curve was linear ( r=1.00) up to 2000 μmol/l, and the detection limit was 10 μmol/l. Within-run and between-run CVs were 0.5–1.1% and 0.4–1.3%, respectively. The 2 h MI of impaired fasting glycemia (IFG; 65.1±46.6 mg/g Cr, P