Changes in the levels and phosphorylation status of Akt, AMPK, CREB and FoxO1 in hypothalamus of rainbow trout under conditions of enhanced glucosensing activity.

There is no available information about mechanisms linking glucosensing activation in fish and changes in the expression of brain neuropeptides controlling food intake. Therefore, we assessed in rainbow trout hypothalamus the effects of raised levels of glucose on the levels and phosphorylation status of two transcription factors, FoxO1 and CREB, possibly involved in linking these processes. We also aimed to assess the changes in the levels and phosphorylation status of two proteins possibly involved in the modulation of these transcription factors: Akt and AMPK. Therefore, in pooled preparations of hypothalamus incubated for 3 and 6 h in the presence of 2, 4 or 8 mmol l-1 d-glucose, we evaluated the response of parameters related to glucosensing mechanisms, neuropeptide expression and levels and phosphorylation status of the proteins of interest. The activation of hypothalamic glucosensing systems and the concomitant enhanced anorectic potential occurred in parallel with activation of Akt and inhibition of AMPK. The changes in these proteins relate to neuropeptide expression through changes in the level and phosphorylation status of transcription factors under their control, such as CREB and FoxO1, which displayed inhibitory (CREB) or activatory (FoxO1) responses to increased glucose.