Chen Guang-Hui, Hogstrand Christer, Luo Zhi, Zhang Dian-Guang, Ling Shi-Cheng, Wu Kun
1Key Laboratory of Freshwater Animal Breeding,Ministry of Agriculture of P.R.C.,Fishery College,Huazhong Agricultural University,Wuhan 430070,People's Republic of China.
2School of Medicine,King's College London,Diabetes and Nutritional Sciences Division,Franklin-Wilkins Building,150 Stamford Street,London SE1 9NH,UK.
Br J Nutr. 2017 Oct;118(8):570-579. doi: 10.1017/S0007114517002446. Epub 2017 Sep 26.
The present study explored the mechanisms of dietary Zn influencing Zn and lipid deposition in the fore- and mid- intestine in yellow catfish Pelteobagrus fulvidraco, and investigated whether the mechanism was intestinal-region dependent. For this purpose, yellow catfish were fed three diets containing Zn levels of 8·83, 19·20 and 146·65 mg Zn/kg, respectively. Growth performance, intestinal TAG and Zn contents as well as activities and mRNA expression of enzymes and genes involved in Zn transport and lipid metabolism in the fore- and mid-intestine were analysed. Dietary Zn increased Zn accumulation as well as activities of Cu-, Zn-superoxide dismutase and ATPase in the fore- and mid-intestine. In the fore-intestine, dietary Zn up-regulated mRNA levels of ZnT1, ZnT5, ZnT7, metallothionein (MT) and metal response element-binding transcription factor-1 (MTF-1), but down-regulated mRNA levels of ZIP4 and ZIP5. In the mid-intestine, dietary Zn up-regulated mRNA levels of ZnT1, ZnT5, ZnT7, MT and MTF-1, but down-regulated mRNA levels of ZIP4 and ZIP5. Dietary Zn reduced TAG content, down-regulated activities of 6-phosphogluconate dehydrogenase (6PGD), glucose-6-phosphate dehydrogenase (G6PD), malic enzyme (ME) and fatty acid synthase (FAS) activities, and reduced mRNA levels of 6PGD, G6PD, FAS, PPARγ and sterol-regulator element-binding protein (SREBP-1), but up-regulated mRNA levels of carnitine palmitoyltransferase IA, hormone-sensitive lipase (HSLa), adipose TAG lipase (ATGL) and PPARα in the fore-intestine. In the mid-intestine, dietary Zn reduced TAG content, activities of G6PD, ME, isocitrate dehydrogenase and FAS, down-regulated mRNA levels of 6PGD, G6PD, FAS, acetyl-CoA carboxylase a, PPARγ and SREBP-1, but up-regulated mRNA expression of HSLa, ATGL and PPARγ. The reduction in TAG content following Zn addition was attributable to reduced lipogenesis and increased lipolysis, and similar regulatory mechanisms were observed between the fore- and mid-intestine.
本研究探讨了饲料锌影响黄颡鱼（Pelteobagrus fulvidraco）前肠和中肠锌及脂质沉积的机制，并研究该机制是否具有肠段依赖性。为此，分别用三种锌含量为8.83、19.20和146.65 mg Zn/kg的饲料投喂黄颡鱼。分析了生长性能、肠道甘油三酯（TAG）和锌含量，以及前肠和中肠中参与锌转运和脂质代谢的酶和基因的活性及mRNA表达。饲料锌增加了前肠和中肠的锌积累以及铜锌超氧化物歧化酶和ATP酶的活性。在前肠中，饲料锌上调了锌转运蛋白1（ZnT1）、锌转运蛋白5（ZnT5）、锌转运蛋白7（ZnT7）、金属硫蛋白（MT）和金属反应元件结合转录因子1（MTF-1）的mRNA水平，但下调了锌转运蛋白4（ZIP4）和锌转运蛋白5（ZIP5）的mRNA水平。在中肠中，饲料锌上调了ZnT1、ZnT5、ZnT7、MT和MTF-1的mRNA水平，但下调了ZIP4和ZIP5的mRNA水平。饲料锌降低了TAG含量，下调了6-磷酸葡萄糖酸脱氢酶（6PGD）、葡萄糖-6-磷酸脱氢酶（G6PD）、苹果酸酶（ME）和脂肪酸合酶（FAS）的活性，并降低了6PGD、G6PD、FAS、过氧化物酶体增殖物激活受体γ（PPARγ）和固醇调节元件结合蛋白（SREBP-1）的mRNA水平，但上调了前肠中肉碱棕榈酰转移酶IA、激素敏感性脂肪酶（HSLa）、脂肪甘油三酯脂肪酶（ATGL）和PPARα的mRNA水平。在中肠中，饲料锌降低了TAG含量、G6PD、ME、异柠檬酸脱氢酶和FAS的活性，下调了6PGD、G6PD、FAS、乙酰辅酶A羧化酶a、PPARγ和SREBP-1的mRNA水平，但上调了HSLa、ATGL和PPARγ的mRNA表达。添加锌后TAG含量的降低归因于脂肪生成减少和脂肪分解增加，并且在前肠和中肠之间观察到了相似的调节机制。
