Down-regulation of insulin receptors in Propionibacterium acnes-activated macrophages in the mouse.

Intraperitoneal administration of Propionibacterium acnes in CD-1 mice was associated with the reduction in number of insulin receptors in peritoneal macrophages (M phi), and with elevated levels of insulin in plasma and the peritoneal cavity. When insulin levels returned to normal, insulin receptors in P. acnes-M phi were still reduced. Insulin appears to contribute significantly to the down-regulation of the M phi-insulin receptors during the early stage of activation. Other biologically active substances released during M phi activation might assume greater influence on insulin resistance in activated M phi at a later stage. The induction of transient hyperinsulinemia in P. acnes-treated mice might be attributed to the effect of concurrently elevated interleukin-1 (IL-1) released in the early course of M phi activation.