Abstract
Simple SummaryGrowing evidence has indicated that glucose absorption exhibits profound circadian rhythmicity, mediated entirely by glucose transporters. We observed that the daily profile of BMAL1, GLUT1 and SGLT1 expression was also synchronized in the intestine and the hepatopancreas of Litopenaeus vannamei. Our result identified for the first time that BMAL1 is a critical mediator regulating the expression of glucose transporters, which could be suppressed by constant darkness in L. vannamei.Aryl hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1) is a core circadian transcription factor that controls the 24-h cycle of physiological processes. In shrimp, the role of BMAL1 in the regulating glucose metabolism remains unclear. Firstly, we observed that the daily profile of BMAL1, GLUT1 and SGLT1 expression were synchronized in the intestine and the hepatopancreas of Litopenaeus vannamei. Then we examined the effects of BMAL1 on the gene expression of glucose transporter type 1 (SGLT1) and sodium-glucose cotransporter 1 (GLUT1) in vivo and in vitro. BMAL1 in L. vannamei shares 70.91–96.35% of sequence identities with other shrimp species and possesses the conserved helix-loop-helix domain and polyadenylation site domain. The in vitro dual-luciferase reporter assay and in vivo RNA interference experiment demonstrated that BMAL1 exerted a positive regulation effect on the expression of glucose transporters in L. vannamei. Moreover, we conducted an eight-week treatment to investigate whether light/dark cycle change would influence growth performance, and gene expression of BMAL1, GLUT1 and SGLT1 in L. vannamei. Our result showed that compared with natural light treatment, constant darkness (24-h darkness) significantly decreased (p < 0.05) serum glucose concentration, and suppressed (p < 0.05) the gene expression of BMAL1, GLUT1 and SGLT1 in the hepatopancreas and the intestine. Growth performance and survival rate were also decreased (p < 0.05) by constant darkness treatment. Our result identified BMAL1 as a critical mediator regulating the expression of glucose transporters, which could be suppressed by constant darkness in L. vannamei. It would be quite interesting to explore the mechanism of dark/light cycles on glucose transport and metabolism in L. vannamei, which might provide a feeding strategy for improving carbohydrate utilization in the future.
Highlights
The endogenous circadian clock is a timekeeping system that drives adaptation to physiological and behavioral events based on daily light change in almost all organisms [1]
We firstly examined the effects of BMAL1 on the gene expression of glucose transporter type 1 (GLUT1) and sodium glucose cotransporter 1 (SGLT1) using in vitro gene overexpression and in vivo gene knockdown technique (RNA interference)
We found that the daily profile of BMAL1, GLUT1 and SGLT1 expression was synchronized in intestine and hepatopancreas
Summary
The endogenous circadian clock is a timekeeping system that drives adaptation to physiological and behavioral events based on daily light change in almost all organisms [1]. Studies in animals have suggested that can a tissue itself express clock genes, but numerous biological processes can exhibit circadian rhythmicity, including DNA synthesis, motility and macronutrient absorption [2,3,4]. Carbohydrates in the diet are firstly digested to glucose, galactose, and fructose in the small intestine. These sugars are absorbed by enterocytes lining the upper third of the intestinal villi [6]. Growing evidence has indicated that glucose absorption exhibits profound circadian rhythmicity and is mediated entirely by glucose transporters [2,8,9]. The regulatory mechanism of circadian clock on glucose transporters has not been well described in crustaceans
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