Hyperinsulinemia drives glomerular podocyte injury and albuminuria via a self-perpetuating GSK3β-IRS1 insulin desensitization circuit.

Epidemiological evidence indicates that hyperinsulinemia is an independent risk factor for albuminuria and renal impairment, yet its molecular basis remains unclear. In prediabetic db/db mice, hyperinsulinemia coincided with albuminuria, podocyte injury, and impaired glomerular insulin signaling, characterized by insulin receptor exhaustion and hypoactivity of the IRS1/PI3K/Akt insulin signaling. This led to diminished inhibitory phosphorylation of GSK3βS9 in podocytes, denoting GSK3β hyperactivity. Notably, GSK3β co-localized and physically interacted with IRS1 in glomerular podocytes, phosphorylating IRS1S332 as a direct substrate. In cultured podocytes, prolonged high insulin exposure induced insulin receptor depletion, GSK3β hyperactivity, and increased inhibitory phosphorylation of IRS1S332, forming a self-perpetuating cycle of insulin desensitization and podocyte injury. GSK3β appears to play a key role, as ectopic expression of a constitutively active GSK3β mutant GSK3βS9A enhanced inhibitory phosphorylation of IRS1S332, desensitized insulin signaling, and exacerbated podocyte injury. In contrast, forced expression of a kinase-dead mutant of GSK3β or inhibition of GSK3β with a selective small-molecule inhibitor tideglusib abrogated inhibitory phosphorylation of IRS1S332, restored insulin sensitivity and protected podocytes. In vivo, GSK3βS9A knock-in mice exhibited impaired insulin signaling and podocyte injury with albuminuria. Conversely, tideglusib treatment in prediabetic db/db mice attenuated podocyte injury and insulin resistance, thereby improving albuminuria. Collectively, hyperinsulinemia directly elicits albuminuria and renal impairment via a cascade of molecular events involving insulin receptor exhaustion, reduced insulin signaling, and GSK3β hyperactivity, which promotes IRS1 inhibition and thereby forms a self-amplifying GSK3β-IRS1 circuit of insulin desensitization and podocyte injury. Targeting GSK3β could disrupt this pathogenic loop and mitigate hyperinsulinemia-induced renal injury.