Meeting Abstract

P3.193  Tuesday, Jan. 6  Insulin affects immune responses differentially in reproductive and non-reproductive Siberian Hamsters (Phodopus sungorus) GARCIA, NW*; GREIVES, TJ; DEMAS, GE; Indiana University; Indiana University; Indiana University nwgarcia@indiana.edu

Many animals living in temperate clines experience relatively predictable seasonal changes in environmental conditions and utilize photoperiodic cues to predict these environmental changes. Most non-tropical mammals must re-allocate finite energy reserves from systems not critical to immediate survival (e.g., immunity) to systems critical to immediate survival (e.g., thermoregulation) and rely environmental cues (i.e., photoperiod) to trigger these adaptations. The seasonal attenuation of immune function is likely regulated by endocrine signals indicating the amount of energy available to the animal. For example, recent research has demonstrated changes in immune functioning in response to the adipose hormone leptin. In addition, the pancreatic hormone insulin is also released in response to elevated blood glucose levels and may indicate readily available energy to the central nervous system. The aim of the present study was to determine the role of insulin in signaling energy status and investment in immune function in animals held under varying photoperiod conditions. To this end, exogenous insulin was administered to reproductive long-day (16:8 L:D) and non-reproductive short-day (8:16 L:D) housed Siberian hamsters (Phodopus sungorus). Hamsters were then challenged with an innocuous antigen, keyhole limpet hemocyanin, and immune response was measured. Insulin treatment significantly enhanced immune response in short-day but not long-day hamsters. These data suggest a role for insulin as a neuroendocrine signal integrating seasonal energetic changes and immune responses.