Sirtuin 1 mediated ceramide metabolism regulates intestinal mechanical barrier function in turbot (Scophthalmus maximus L.).

Sirtuin 1 (Sirt1), a member of the sirtuin family, is integral to the regulation of energy homeostasis, cellular metabolism, and stress responses. While Sirt1 has been intensively studied in mammals, studies on this gene in aquatic animals, especially turbot, is relatively limited. In this study, the sirt1 gene was cloned. The open reading frame (ORF) of the Sirt1 consists of 2187 base pairs, encoding a 728-amino-acid protein that contains a SIR2 domain. Compared with the siRNA-NC group, Sirt1 knockdown resulted in a significant downregulation of mRNA expression levels of the tight junction proteins occludin, tricellulin, claudin3, and zo1, as well as protein levels of Occludin and ZO1, within the intestinal tissue of turbot. Concurrently, it markedly inhibited the expression of genes associated with ceramide synthesis (sptlc2, kdsr, cers1, cers2, cers3, smpdl3a, smpdl3b, neu1, glb1, gba1, and sgpp2) and ceramide catabolism (sgms1a, ugcg, b4galt, and sphk1) in the same tissue. Conversely, compared to the pcDNA3.1 group, Sirt1 overexpression significantly enhanced the mRNA expression levels of occludin, tricellulin, claudin3, claudin7, and zo1, along with the protein level of Occludin. Furthermore, Sirt1 overexpression significantly elevated the expression of genes involved in ceramide synthesis (cers2, cers3, smpd3, smpdl3b, neu1, glb1, gba1, sgpp2) and ceramide catabolism (sgms1a, galt, b4galt, and sphk1). These results suggest that Sirt1 may influence the intestinal mechanical barrier by acting on the metabolic balance of ceramide and altering the expression of intestinal tight junction proteins, thus playing a crucial role in maintaining the intestinal health of turbot.