Peptide YY in Type 2 Diabetes: A Complementary Gut Hormone with Therapeutic Potential Beyond GLP-1

Type 2 diabetes (T2D) is a complex metabolic disease characterized by insulin resistance, progressive β-cell dysfunction, and persistent hyperglycemia. While GLP-1 receptor agonists have revolutionized the management of T2D by improving glycemic control and reducing body weight, their insulinotropic effects increase the workload on pancreatic β-cells, which may hasten β-cell decline in certain individuals. Peptide YY (PYY), a gut-derived hormone secreted alongside glucagon-like peptide-1 (GLP-1) from L-cells, presents a unique and complementary therapeutic approach. In contrast to GLP-1, PYY does not directly induce insulin release but confers metabolic advantages by suppressing appetite through Y2 receptor pathways, enhancing insulin sensitivity via peripheral Y1/Y4 receptors, and slowing gastric emptying to minimize postprandial glucose surges. Notably, recent research suggests PYY supports the preservation and restoration of pancreatic islets by improving their structure and function without increasing the secretory demand. PYY levels are substantially increased after bariatric surgery, where it plays a pivotal role in weight-loss-independent improvements in glycemic regulation and islet hormone dynamics. These attributes position PYY as a strong candidate for use in combination with GLP-1 analogs, especially in individuals with advanced β-cell impairment or those who respond inadequately to GLP-1 monotherapy. This review discusses PYY's physiological functions, mechanistic actions, and therapeutic opportunities in T2D, highlighting its potential as a valuable adjunct or alternative in gut-hormone-oriented treatment strategies.