Hypoglycemic conditions enhance neonatal β-cell glucose responsiveness via AMPK/mTOR-increased KATP channel density

Le résumé fourni par la source

At birth, blood glucose levels drop sharply before rising to normoglycemic adult levels. This is accompanied by functional maturation of pancreatic β-cells and the acquisition of glucose-responsive insulin secretion. Although transcriptional programs have been well characterized, the metabolic adjustments that enhance insulin secretion in neonatal β-cells remain poorly understood. Neonatal islets exhibit a high rate of basal insulin secretion, and elevating glucose to high concentrations produces little additional stimulation (unlike adult islets). This study aimed to elucidate how neonatal pancreatic β-cells become glucose-responsive, using an in vitro protocol involving culture of neonatal islets at low glucose to emulate systemic hypoglycemia. Low-glucose exposure markedly improved glucose responsiveness of neonatal islets by selectively lowering insulin secretion at low glucose concentrations. Unlike adult β-cells, neonatal β-cells were depolarized and generated spontaneous action potentials at low glucose, resulting in elevated [Ca2+]i and a blunted response to high glucose. These changes were reversed by brief (1-2 hours) low-glucose culture, which was accompanied by increased KATP channel surface expression and activity. The effects of low-glucose incubation were mimicked by the AMPK agonist AICAR. These insights may inform strategies to restore glucose-regulated insulin secretion in type 2 diabetes.

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