A 56-year-old male presents to your office for a follow-up visit to discuss the management of his type 2 diabetes. The patient was diagnosed with type 2 diabetes 5 years ago. His blood sugar levels have been suboptimal despite adherence to a healthy diet and regular exercise. He has been taking metformin 1000 mg twice daily, but his HbA1c has remained elevated at 8.2%. He reports no significant side effects from metformin but struggles with postprandial glucose spikes. He denies any symptoms of hypoglycemia. On physical examination, his BMI: 28.5 kg/m²; Blood Pressure: 126/78 mmHg and Heart rate: 72 bpm, regular. Laboratory test results revealed HbA1c: 8.2%; Fasting blood glucose: 160 mg/dL; Renal function: eGFR 98 mL/min/1.73m² and Liver function tests: Normal. You would like to initiate another medication from the DPP-4 inhibitor class for glucose control in this patient. What is the primary mechanism of action of DPP-4 inhibitors in managing type 2 diabetes?
