Effects of dietary phosphorus levels on phosphorus and fatty acid transport and triglyceride deposition in the intestine of GIFT tilapia (Oreochromis niloticus)

Phosphorus is an important mineral element in animals, and it is an essential component of bone, phospholipids, nucleoproteins and nucleic acids. However, there are few studies on effects of dietary phosphorus on phosphorus content, fatty acid transport and lipid deposition in the intestines. The present study was conducted to explore the effect of dietary phosphorus levels on phosphorus and fatty acid transport, and lipid metabolism in the intestines of GIFT tilapia. Three diets were formulated with phosphorus at the levels of 1.21% (LPD), 1.75% (MPD), 2.66% (HPD). The diets were fed to juvenile GIFT tilapia for 10 weeks. Compared with the LPD group, HPD group significantly increased gene (95.7%) and protein expression (200.1%) of the SLC34A2 and total phosphorus content (79.2%) of the intestine. Compared with the LPD group, the HPD group up-regulated the expression of the fatty acid absorption-related genes cd36, fabp1, fabp2, and fatp1 and the TG synthesis-related genes dgat1(by 11.2% to 54.0%) , down-regulated the expression of the fatty acid transport-related genes apob-100 (37.7%), and increased the content of non-esterified fatty acid (NEFA) (241.1%) in the intestine. HPD also increased TG content (42.9%). In conclusion, our study showed that high dietary phosphorus increased intestinal TG content by inhibiting the fatty acid export and up-regulating the fatty acid absorption. Our study may provide a basis for the further elucidation into the mechanism of dietary phosphorus influencing phosphorus and lipid metabolism in fish.