['Glucose and fatty acids comprise the primary substrates for myocardial energy metabolism. The normal myocardium switches toward glucose metabolism in the setting of stress; the inability to affect such a switch is a fundamental mechanism behind "diabetic" or "insulin-resistant" cardiomyopathy. The purpose of this mechanistic study was to evaluate the effects of treatment with the dipeptidyl peptidase (DPP) 4 inhibitor sitagliptin on myocardial glucose uptake in patients with nonischemic cardiomyopathy.', 'Twelve nondiabetic subjects with nonischemic cardiomyopathy underwent metabolic testing and assessment of myocardial glucose uptake by (18)F-fluorodeoxyglucose positron-emission tomographic/computerized tomographic imaging at baseline and after 4 weeks of sitagliptin therapy. Sitagliptin therapy resulted in a significant increase in myocardial glucose uptake (19% increase; P\xa0= .04). Although most patients had at least a slight increase in glucose uptake, there was an overall bimodal response, with 6 patients ("responders") demonstrating large increases (>20%) in glucose uptake and 6 patients ("nonresponders") demonstrating <5% increases or slight decreases. Triglyceride-high-density lipoprotein ratios significantly dropped in the 6 responders compared with the 6 nonresponders (P < .02).'] Does dipeptidyl peptidase 4 inhibition increase myocardial glucose uptake in nonischemic cardiomyopathy?