The novel adipokine Placin regulates glucose homeostasis via insulin secretion and IGF1 receptor signaling.

While genome-wide association studies have linked the human PLAC9 gene to body mass index, its physiological function remains largely unexplored. This study identifies PLAC9 as a novel adipokine that is enriched in the stromal vascular fraction of adipose tissue. Its circulating levels correlate with key metabolic dysregulation markers in humans and mice. We utilized gain- and loss-of-function approaches in diet-induced obesity (DIO) and streptozotocin (STZ)-induced diabetic mouse models to demonstrate that PLAC9 is a critical regulator of systemic metabolism. Notably, knockdown of endogenous PLAC9 exacerbated metabolic impairments, while its overexpression significantly mitigated DIO-associated metabolic dysregulation. Additionally, recombinant PLAC9 protein administration alleviated hyperglycemia in insulin-resistant and insulin-deficient models. Mechanistically, PLAC9 potentiated calcium-dependent insulin secretion in pancreatic beta cells, promoted glucose uptake in the liver and skeletal muscle, and upregulated hepatic Ghr and Igf1 levels to facilitate glucose homeostasis. Based on these hormone-like properties, we propose renaming the protein Placin. Collectively, these findings establish Placin as a promising therapeutic target, offering translational potential for the management of both type 2 and type 1 diabetes.