Microglial regulation of satiety and cognition

Abstract

Microglia have been known for decades as key immune cells that shape the central nervous system (CNS) during development and respond to brain pathogens and injury in adult life. Recent findings now suggest that these cells also play a highly complex role in several other functions of the CNS. In this review, we provide a brief overview of the established microglial functions in development and disease. We also discuss emerging research suggesting that microglia are important for both cognitive function and the regulation of food intake. With respect to cognitive function, current data suggest microglia are not indispensable for neurogenesis, synaptogenesis or cognition in the healthy young adult, although they crucially modulate and support these functions. In doing so, they are likely important in supporting the balance between apoptosis and survival of newborn neurones and in orchestrating appropriate synaptic remodelling in response to a learning stimulus. We also explore the possibility of a role for microglia in feeding and satiety. Microglia have been implicated in both appetite suppression with sickness and obesity and in promoting feeding under some conditions and we discuss these findings here, highlighting the contribution of these cells to healthy brain function.

Microglia depletion fails to abrogate inflammation-induced sickness in mice and rats

“…In addition, microglia depletion by diphtheria toxin was not associated with any evidence of impairment in learning and memory as measured by short-term memory in a novel object and place recognition tasks [16]. Further studies indicate that the anorexia induced by administration of diphtheria toxin to Cx3cr1-Dtr rats is actually due to disruption of the gustatory circuitry a the level of the paraventricular nucleus of the hypothalamus [15], indicating the complex role microglia play in brain functions additional to their traditional role in regulating neuroinflammation [24].…”

Microglia depletion fails to abrogate inflammation-induced sickness in mice and rats

“…In addition, microglia depletion by diphtheria toxin was not associated with any evidence of impairment in learning and memory as measured by short term memory in a novel object and place recognition tasks (16). Further studies indicate that the anorexia induced by administration of diphtheria toxin to Cx3cr1-Dtr rats is actually due to disruption of the gustatory circuitry a the level of the paraventricular nucleus of the hypothalamus (15), indicating the complex role microglia play in brain functions additional to their traditional role in regulating neuroinflammation (22).…”

Microglial ablation in rats disrupts the circadian system

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Research is increasingly revealing new roles for microglia in the developed brain beyond their well-known function in protecting it from pathogens and injury. 1,2 For example, recent work has demonstrated microglia are likely to be important for memory processing and executive function. [3][4][5][6] Microglial activity directed at pruning of synapses mediates memory degradation in a complement-dependent manner in a contextual fear conditioning task.

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