In pioglitazone-treated subjects , plasma adiponectin concentration increased threefold from 13 0.5 to 38 2.5 g/mL ( P < 0.001 ) and was strongly correlated with the improvement in SI ( r = 0.436 , P < 0.001 ) and modestly correlated with glucose area under the curve during oral glucose tolerance test ( r = 0.238 , P < 0.005 ) and insulin secretion/insulin resistance index ( r = 0.306 , P < 0.005 ) .