Abstract
The present study aimed to investigate whether dietary choline can regulate lipid metabolism and suppress NFκB activation and, consequently, attenuate inflammation induced by a high-fat diet in black sea bream (Acanthopagrus schlegelii). An 8-week feeding trial was conducted on fish with an initial weight of 8·16 ± 0·01 g. Five diets were formulated: control, low-fat diet (11 %); HFD, high-fat diet (17 %); and HFD supplemented with graded levels of choline (3, 6 or 12 g/kg) termed HFD + C1, HFD + C2 and HFD + C3, respectively. Dietary choline decreased lipid content in whole body and tissues. Highest TAG and cholesterol concentrations in serum and liver were recorded in fish fed the HFD. Similarly, compared with fish fed the HFD, dietary choline reduced vacuolar fat drops and ameliorated HFD-induced pathological changes in liver. Expression of genes of lipolysis pathways were up-regulated, and genes of lipogenesis down-regulated, by dietary choline compared with fish fed the HFD. Expression of nfκb and pro-inflammatory cytokines in liver and intestine was suppressed by choline supplementation, whereas expression of anti-inflammatory cytokines was promoted in fish fed choline-supplemented diets. In fish that received lipopolysaccharide to stimulate inflammatory responses, the expression of nfκb and pro-inflammatory cytokines in liver, intestine and kidney were all down-regulated by dietary choline compared with the HFD. Overall, the present study indicated that dietary choline had a lipid-lowering effect, which could protect the liver by regulating intrahepatic lipid metabolism, reducing lipid droplet accumulation and suppressing NFκB activation, consequently attenuating HFD-induced inflammation in A. schlegelii.
Highlights
The present study aimed to investigate whether dietary choline can regulate lipid metabolism and suppress NFκB activation and, attenuate inflammation induced by a high-fat diet in black sea bream (Acanthopagrus schlegelii)
Recent studies reported that dietary choline supplementation affected hepatic transport and lipid deposition in various fish species, which suggested that dietary choline could reduce hepatic lipid content and influence expression of lipid metabolism genes[23,24,25,26]
Intestine and kidney were collected from all fish 24 h after injection, and snap-frozen in liquid N2 and stored at −80°C for later gene expression analysis of nfκb, il-1β, tnfα, tgfβ-1 and il-10(4,31,42,43)
Summary
The present study aimed to investigate whether dietary choline can regulate lipid metabolism and suppress NFκB activation and, attenuate inflammation induced by a high-fat diet in black sea bream (Acanthopagrus schlegelii). In fish that received lipopolysaccharide to stimulate inflammatory responses, the expression of nfκb and pro-inflammatory cytokines in liver, intestine and kidney were all down-regulated by dietary choline compared with the HFD. The present study indicated that dietary choline had a lipid-lowering effect, which could protect the liver by regulating intrahepatic lipid metabolism, reducing lipid droplet accumulation and suppressing NFκB activation, attenuating HFD-induced inflammation in A. schlegelii. Previous studies demonstrated that dietary choline could modulate immune responses by reducing expression of pro-inflammatory biomarkers such as TNF-α (tnfα), IL-1β (il-1β) and NFκB (nfκb), and up-regulating mRNA expression of anti-inflammatory cytokine IL-10 (il-10) and transforming growth factor β-1 (tgfβ-1) in vertebrates including fish[27,28,29]. NFκB is a key nuclear transcription factor tightly linked to the inflammatory response
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