The ApoA-IV-LRP1 Signaling Axis: A Novel Insulin-Independent Pathway for the Suppression of Diabetic Hyperglucagonemia.

Apolipoprotein A-IV (ApoA-IV) is a glycoprotein secreted by the small intestine to regulate lipid metabolism and satiety. Its role in insulin-independent glucose homeostasis remains largely unknown. In this study, we demonstrate that intestinal ApoA-IV overexpression significantly attenuates diet-induced obesity and hyperglycemia following severe β-cell loss. Over a 20-week high-fat diet challenge, ApoA-IV transgenic (ApoA-IV-Tg) mice maintained significantly lower adiposity than wild-type controls, driven by elevated energy expenditure and fatty acid oxidation rather than reduced caloric intake. Beyond weight maintenance, ApoA-IV maintained excellent systemic glycemic control and enhanced peripheral insulin sensitivity. Most notably, ApoA-IV significantly attenuated hyperglycemia following streptozotocin (STZ)-induced β-cell ablation, maintaining glucose stability despite severe insulin deficiency. Mechanistically, this protection results from a blunted glucagon response and the subsequent suppression of the hepatic pCREB-G6Pase gluconeogenic signaling pathway. In vitro evidence confirms that ApoA-IV directly inhibits pancreatic α-cell glucagon secretion through an LDL receptor-related protein 1 (LRP1)-dependent pathway, reinforced by the precise co-localization of LRP1 and glucagon in pancreatic islets. Furthermore, ApoA-IV-Tg mice were protected from the STZ-induced corticosterone surge and systemic lipolysis. Collectively, these findings establish the ApoA-IV-LRP1 signaling axis as a potent metabolic switch, providing a promising insulin-independent strategy for managing obesity and diabetes.