Dietary keto-acid feed-back on pituitary activity in gilthead sea bream: Effects of oral doses of AKG. A proteomic approach

The influence of a daily oral dose of alpha-ketoglutarate (AKG, 0.1 g/kg body weight), an intermediate metabolite in the Krebs cycle and a dietary additive, on the pituitary proteome of gilthead sea bream was determined by two-dimensional electrophoresis (2-DE). A high-resolution map of the sea bream pituitary proteome was generated. Proteins with a modified expression between Controls and AKG treated fish were further analysed by MALDI-TOF/TOF-MS and liquid chromatography combined with a nanoelectrospray (LC–MS/MS). The main changes in the proteome induced by AKG treatment were grouped. Metabolic proteins up-regulated with AKG supplementation included fructose-bis-phosphate aldolase, glyceraldehyde-phosphate dehydrogenase and malate dehydrogenase, all related to glucose metabolism (p < 0.000). Protein folding related up-regulation with AKG supplementation included two isoforms of heat shock proteins as well as cyclophylin and chaperonin (p < 0.000). An unexpected form of apolipoprotein-A-1 with lower molecular weight (15–16 kDa) was evidenced as being highly abundant in the pituitary proteome of Controls, yet it was down-regulated by AKG treatment. Finally, proteins found to be associated with regeneration of neural function namely cofilin and Vat-protein were up-regulated after AKG supplementation. The only hormone to be modified by AKG treatment was somatolactin, which was significantly down-regulated cf. Controls. In summary, these results provide evidence of a potential endocrine/metabolic regulatory loop activated by AKG supplementation.

Research highlights
► The paper is original and examines the influence of a daily oral dose of alpha-ketoglutarate (a dietary additive) and resulting molecular modifications by a proteomic approach in pituitary gilthead sea bream.
► For the first time a fish pituitary proteome was obtained and dietary AKG multifactorial alterations were related with a feed-back (nutrition to pituitary) loop.
► The pituitary proteome revealed up-regulation of proteins related to glucose metabolism and protein folding, and down-regulation of somatolactin and apolipoprotein (the most abundant protein in pituitary proteome).
► Moreover, some interesting proteins related to neural regeneration (such as cofilin and Vat-protein) were up-regulated.
► These results provide evidence of a potential endocrine/metabolic regulatory loop activated by AKG supplementation.