ALPHA-KETOGLUTARATE INDUCES NUCLEAR RECEPTORS RATHER THAN NRF2 IN THE FRUIT FLY Drosophila melanogaster

Aim. To test whether expression of Nrf2 targets in the fruit fly Drosophila melanogaster are activated by diet supplemented with alpha-ketoglutarate (AKG). Methods. The Canton-S strain of D. melanogaster was used in the study. Female flies were reared in demographic cages (150 flies per group) on the medium containing 5% sucrose, 5% yeast, 1.2% agar, 0.18% nipagin. Experimental diet was supplemented with 10 mM disodium salt of AKG. The flies were reared during 21 days and after that were anesthetized with carbon dioxide and snap-frozen in liquid nitrogen for further biochemical studies. Expression of genes Ugt37A2, GstD2, and Cyp6a2, coding for a uridine diphosphate glycosyltransferase family 37 member A2, glutathione S-transferase D2, and cytochrome P450 6a2, respectively, respectively, was analyzed using semi-quantitative reverse transcription polymerase chain reaction followed by visualization of the products in agarose gel. The gene Tbp (TATA-box binding protein) was used as a reference gene. Results. Flies fed AKG-supplemented diet during 21 days had 2.8-fold higher level of the Cyp6a2 expression than control flies. At the same time, AKG-supplemented food did not affect expression of Ugt37A2 and GstD2 genes. Conclusions. Continuous consumption of AKG-supplemented food results in the increase in the levels of messenger ribonucleic acid of Cyp6a2 gene, a target of transcriptional factors Nrf2 and DHR96, but not Ugt37A2 and GstD2 genes. Since expression of the latter two genes was unaffected by AKG-supplemented diet, it indicates that AKG may influence other transcriptional regulators, such as nuclear receptors that have common targets with Nrf2.