Response of rainbow trout's (Oncorhynchus mykiss) hypothalamus to glucose and oleate assessed through transcription factors BSX, ChREBP, CREB, and FoxO1.

We aimed to obtain information regarding mechanisms that link glucose- and fatty acid-sensing systems to expression of neuropeptides that regulate food intake in the fish brain. We assessed the relative expression and protein levels of the transcription factors BSX, ChREBP, FoxO1, and CREB in the hypothalamus of rainbow trout (Oncorhynchus mykiss) treated for 6 h with either glucose or oleate in vivo (intra-cerebroventricular treatment with 1 µl 100 g body weight of 40 µg glucose or 1 µmol oleate) or in vitro (incubation with 4-8 mM glucose or 100-500 µM oleate). BSX levels decreased after oleate treatment for mRNA (10% in vitro and 47% in vivo) and protein (25%), while minor changes occurred after glucose treatment. CREB values generally decreased after glucose or oleate treatment for mRNA (50% in vivo) as well as the phosphorylation status of protein (80%). Foxo1 mRNA levels increased in vivo with glucose (129%) and decreased in vivo with oleate (60%), and protein phosphorylation status increased with glucose (in vivo) and oleate. mRNA values of chrebpα decreased in response to glucose and oleate, while protein levels decreased with oleate and increased with glucose. The results support the association of several transcription factors with metabolic control of food intake in fish.