A 40-year-old woman has experienced chest pain on exertion for the past 2 months. A month ago, she had pneumonia with Streptococcus pneumoniae cultured from her sputum. On physical examination, she has a body mass index of 35. A random blood glucose value is 132 mg/dL. The next day, fasting blood glucose is 120 mg/dL, followed by a value of 122 mg/ dL on the following day. She is given an oral glucose tolerance test, and her blood glucose is 240 mg/dL 2 hours after receiving the standard 75-g glucose dose. On the basis of these findings, she is prescribed an oral thiazolidinedione (TZD) drug. After 2 months of therapy, her fasting blood glucose is 90 mg/ dL. The beneficial effect of TZD in this patient is most likely related to which of the following processes?