A defect in vivo in the epimerization of myoinositol to chiro-inositol in insulin sensitive tissuesof the GK type 2 diabetic rat has been elucidated.Thus, administered D-chiro-inositolmay act to bypass a defective normal epimerizationof myo-inositol to D-chiro-inositolassociated with insulin resistance and act to atleast partially restore insulin sensitivity and glucosedisposal. The gene discussed is INS; the disease is Insulin resistance.