Abstract
The prevalence of obesity has increased rapidly in recent years and has put a huge burden on healthcare worldwide. Obesity is associated with an increased risk for many comorbidities, such as cardiovascular diseases, type 2 diabetes and hypertension. The hypothalamus is a key brain region involved in the regulation of food intake and energy expenditure. Research on experimental animals has shown neuronal loss, as well as microglial activation in the hypothalamus, due to dietary-induced obesity. Microglia, the resident immune cells in the brain, are responsible for maintaining the brain homeostasis and, thus, providing an optimal environment for neuronal function. Interestingly, in obesity, microglial cells not only get activated in the hypothalamus but in other brain regions as well. Obesity is also highly associated with changes in hippocampal function, which could ultimately result in cognitive decline and dementia. Moreover, changes have also been reported in the striatum and cortex. Microglial heterogeneity is still poorly understood, not only in the context of brain region but, also, age and sex. This review will provide an overview of the currently available data on the phenotypic differences of microglial innate immunity in obesity, dependent on brain region, sex and age.
Highlights
Microglial cells, the resident innate immune cells in the central nervous system (CNS), have risen as a key player in many pathologies, including metabolic syndrome, neurodegenerative and cardiovascular conditions
Microglial cells play a key role in obesity-associated neuroinflammation
The activation status of the microglia has been found to differ during obesity, depending on the brain region
Summary
Microglial cells, the resident innate immune cells in the central nervous system (CNS), have risen as a key player in many pathologies, including metabolic syndrome, neurodegenerative and cardiovascular conditions. Their main role is surveillance of the brain microenvironment. Microglia secrete cytokines, mediating the innate immune response. Another key microglial function, important for maintaining brain homeostasis, is phagocytosis. This review aims to assess the available studies evaluating the brain region, sex and age heterogeneity in the microglial function in obesity. The majority of the studies included in this review were performed on experimental rodents, unless stated otherwise (e.g., humans)
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