Enhancement of insulin‐stimulated myocardial glucose uptake in patients with Type 2 diabetes treated with rosiglitazone

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Abstract
Aims  Peroxisome proliferator‐activated receptor γ (PPARγ) activators have recently been identified as regulators of cellular proliferation, inflammatory responses and lipid and glucose metabolism. These agents prevent coronary arteriosclerosis and improve left ventricular remodelling and function in heart failure after myocardial infarction. Improvement in myocardial metabolic state may be one of the mechanisms behind these findings. The aim of this study was to investigate the effects of rosiglitazone on myocardial glucose uptake in patients with Type 2 diabetes. Placebo and metformin were used as control treatments.Methods  Forty‐four patients were randomized to treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.) or placebo in a 26‐week double‐blinded trial. Myocardial glucose uptake was measured using [18F]‐2‐fluoro‐2‐deoxy‐D‐glucose ([18F]FDG) and positron emission tomography (PET) during euglycaemic hyperinsulinaemia before and after the treatment.Results  Rosiglitazone increased insulin‐stimulated myocardial glucose uptake by 38% (from 38.7 ± 3.4 to 53.3 ± 3.6 µmol 100 g−1 min−1, P = 0.004) and whole body glucose uptake by 36% (P = 0.01), while metformin treatment had no significant effect on myocardial (40.5 ± 3.5 vs. 36.6 ± 5.2, NS) or whole body glucose uptake. Myocardial work as determined by the rate‐pressure‐product was similar between the groups. Neither treatment had any significant effect on fasting serum free fatty acids (FFA) but the FFA levels during hyperinsulinaemia were more suppressed in the rosiglitazone group (−47%, P = 0.02). Myocardial glucose uptake correlated inversely to FFA concentrations both before (r =−0.54, P = 0.002) and after (r = −0.43, P = 0.01) the treatment period in the pooled data. Furthermore, the increase in myocardial glucose uptake correlated inversely with interleukin‐6 (IL‐6) concentrations (r = −0.58, P = 0.03).Conclusions  In addition to the improvement in whole body insulin sensitivity, rosiglitazone treatment enhances insulin stimulated myocardial glucose uptake in patients with Type 2 diabetes, most probably due to its suppression of the serum FFAs.

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