Pancreatic Brsk2 amplifies parasympathetic signals to promote type 2 diabetes

ABSTRACT The parasympathetic nervous system (PNS) modulates postprandial glucose metabolism via innervating pancreas; however, its significance in the pathogenesis of type 2 diabetes (T2DM) remains unclear. Here we show that brain-specific serine/threonine-protein kinase 2 (Brsk2), accumulated in obese mouse islets, responds to PNS activation and initiates pre-absorptive insulin release. In inducible mouse models, excessive Brsk2 amplifies parasympathetic signaling to β cells and increases their secretion, ensuing insulin resistance and T2DM. Conversely, Brsk2 inhibition prevents and treats HFD-induced metabolic abnormities via avoiding β-cell oversecretion. Mechanistically, parasympathetic acetylcholine activates cholinergic receptor M3 (Chrm3), then Chrm3 recruits and stabilizes Brsk2, which in turn phosphorylates phospholipase A2 activating protein (Plaa). A Chrm3-Brsk2-Plaa axis stimulates β-cell hypersecretion during both pre-absorptive and absorptive stages in HFD-feeding mice, thus imposing insulin resistance and β-cell dysfunction. Blocking parasympathetic signaling to β cells by Brsk2 protein restoration, autonomic mediation drugs, or vagotomy restricted diabetes development. Moreover, three human BRSK2 variants are associated with hyperinsulinemia, insulin resistance, and T2DM in the Chinese population. These findings reveal that Brsk2 links parasympathetic nervous system to nutrition-overload induced T2DM.