Inhibition of insulin secretion from rat islets of Langerhans by interleukin-6. An effect distinct from that of interleukin-1

Abstract

Glucose-induced insulin secretion from islets cultured in the presence of interleukin-6 (IL-6) for 12-24 h was inhibited to a similar extent as when islets were treated with interleukin-1β (IL-1β). However, unlike IL-1β, IL-6 did not potentiate insulin secretion during an acute (30 min) exposure of islets to the cytokine, nor did it inhibit DNA synthesis during a 24 h culture period. A 12 h pretreatment of islets with tumour necrosis factor-α (TNF-α) combined with IL-1β potentiated the inhibitory effect of IL-1β on secretion, such that 20 mM-glucose-induced insulin secretion was abolished. No synergistic inhibition of secretion was observed with TNF-α and IL-6. However, IL-1β and IL-6 were found to inhibit insulin secretion in an additive manner. These results suggest that IL-6 inhibits insulin secretion in a manner distinct from that of IL-1β, and that IL-6 is unlikely to mediate the inhibitory effects of IL-1β or TNF-α on rat islets of Langerhans.