Effect of Photoperiod and Acute Stress on Facilitative Glucose Transporter GLUT3 in Siberian Hamsters (Phodopus sungorus)

Abstract

Metabolic activity in mammalian brains is dependent upon glucose utilization.  Transport of glucose to the neurons requires mediation by a family of known as facilitative glucose transporter proteins (GLUTs).  The GLUT3 isoform is solely responsible for facilitating glucose transport in mammalian brains. Studies show that age-related brain dysfunction and disease, as well as reductions in learning and memory correlate with decreased GLUT3 expression. Winter is a particularly difficult time to reproduce and survive because of the energy bottleneck caused by the coincidence of low ambient temperatures with reduced food availability. Individuals cope with this energetic bottleneck by engaging tradeoffs among expensive physiological processes through development of specific adaptations including adjustments in metabolic rate, body mass, reproduction, and immune function. Non-tropical animals determine time-of-year by monitoring photoperiod (day length) in order to evoke the appropriate suite of adaptations. However, such metabolic trade-offs can be challenged by stressors. To test the combined effects of acute stress and photoperiod on GLUT3 expression, male adult Phodopus sungorus were housed in either long or short photoperiods for 14 weeks. After 14 weeks, half of the animals from each photoperiod were subjected to restraint stress immediately prior to brain collection. Brain tissue from each animal was excised and used in GLUT3 gene expression analysis. The findings of this study demonstrate that photoperiod and acute stress do not impact the facilitative glucose transporter GLUT3 at the RNA expression level. Further research needs to be conducted in order to determine the precise mechanism which regulates the expression of the GLUT3 transporter in neurons of the hippocampus.