Meeting Abstract
S6.3 Wednesday, Jan. 5 The energetics of immunity: Leptin as a physiological mediator of energetic trade-offs in eco-immunology DEMAS, Gregory E.*; FRENCH, Susannah S.; Indiana University; Utah State University gdemas@indiana.edu
Immunity, like all other biological processes, requires adequate energy to sustain optimal function. The role of energy balance, however, has only recently been considered in the context of immune function and disease. Energy is not limitless; finite energy reserves must serve all physiological processes and thus must be allocated to a wide variety of often competing biological functions. At times of reduced energy availability or increased energy output, trade-offs can result in which energy is diverted from less critical physiological functions to ones more important for immediate survival. Despite the clear link between energy availability and immunity, relatively little is known regarding the physiological mechanisms by which energy regulates immune function. A variety of endocrine factors have been identified as potential candidates serving as biochemical signals of current energy availability. One likely endocrine candidate linking available energy stores with immune function is leptin. Leptin, a peptide hormone synthesized and secreted predominantly by adipose tissue, affects a wide variety of diverse actions within the immune system. Here we review the evidence in support of leptin as a key regulator of energetic trade-offs in both laboratory and field studies and across several vertebrate taxa, including mammals and reptiles. Collectively, these studies provide compelling support for the hypothesis that leptin provides a neuroendocrine signal from body fat to the immune system and plays an important role in mediating energetic trade-offs. Lastly, we will discuss how changes in physiology, driven by alterations in energetic state, may contribute in important ways to disease susceptibility. Thus, host physiology serves as an important, but often underappreciated, variable linking eco-immunology with disease ecology.
