In vivo chiro-inositol metabolism in the rat: a defect in chiro-inositol synthesis from myo-inositol and an increased incorporation of chiro-[3H]inositol into phospholipid in the Goto-Kakizaki (G.K) rat

Abstract

We report our comparative studies of myo- and chiro-[3H]inositol distribution in control nondiabetic Wistar and spontaneous nonobese insulin-resistant Type II diabetic G.K. rat tissues following 78-h labeling period. From various tissue extracts, free inositols, inositol phosphates, and inositol phospholipids were isolated and analyzed. Our findings demonstrate (1) a significant difference in the metabolism of myo- and chiro-inositol in normal Wistar and G.K. rats, (2) a severe defect in conversion of myo-[3H]inositol to chiro-[3H]inositol at the inositol phospholipid level of insulin-sensitive tissues of the G.K. rat, (3) an increased incorporation of myo-[3H]inositol into purified inositol phospholipids of the G.K. rat consistent with a decreased conversion to chiro-[3H]inositol, (4) the presumed presence of a pathway which incorporates chiro-[3H]inositol into inositol phospholipids, and which is overactive in the G.K. rat compared to the Wistar rat, and (5) no or minimal conversion of chiro-[3H]inositol to myo-[3H]inositol.