The 'selfish brain' is regulated by aquaporins and autophagy under nutrient deprivation

The brain maintains its mass and physiological functional capacity compared with other organs under harsh conditions such as starvation, a mechanism termed the 'selfish brain' theory. To further investigate this phenomenon, mice were examined following water and/or food deprivation. Although the body weights of the mice, the weight of the organs except the brain and blood glucose levels were significantly reduced in the absence of water and/or food, the brain weight maintained its original state. Furthermore, no significant differences in the water content of the brain or its energy balance were observed when the mice were subjected to water and/or food deprivation. To further investigate the mechanism underlying the brain maintenance of water and substance homeostasis, the expression levels of aquaporins (AQPs) and autophagy-specific protein long-chain protein 3 (LC3) were examined. During the process of water and food deprivation, no significant differences in the transcriptional levels of AQPs were observed. However, autophagy activity levels were initially stimulated, then suppressed in a time-dependent manner. LC3 and AQPs have important roles for the survival of the brain under conditions of food and water deprivation, which provided further understanding of the mechanism underlying the 'selfish brain' phenomenon. Although not involved in the energy regulation of the 'selfish brain', AQPs were observed to have important roles in water and food deprivation, specifically with regards to the control of water content. Additionally, the brain exhibits an 'unselfish strategy' using autophagy during water and/or food deprivation. The present study furthered current understanding of the 'selfish brain' theory, and identified additional regulating target genes of AQPs and autophagy, with the aim of providing a basis for the prevention of nutrient shortage in humans and animals.