A 56-Year-Old Man Visits the Office for a Check-Up on His

A 56-year-old man visits the office for a check-up on his type 2 diabetes mellitus. The patient's glycemic control was inadequate with metformin monotherapy, so a new medication that inhibits dipeptidyl peptidase-4 was prescribed three months ago. He is in good health and reports no side effects from the new therapy. Ramipril is also used to treat the patient's hypertension. He does not smoke, drink, or use illegal drugs. The patient claims he follows dietary recommendations in general but occasionally indulges in fast food. The blood pressure is 126/74 mm Hg, and the pulse rate is 76 beats per minute. 31.4 kg/m² is the BMI. A physical examination reveals no anomalies.   Laboratory results show a hemoglobin A1c of 6.8%.  The newly prescribed medication most likely improved this patient's glycemic control through which of the following direct mechanisms?

A) Decreased dietary carbohydrate digestion
B) Decreased renal glucose reabsorption
C) Increased glucagon secretion
D) Increased glucose-dependent insulin release
E) Increased peripheral tissue glucose uptake