Effects Of High Levels Of Zinc On Metabolism Of Lipids And Its Mechanism In Piglets

Zn plays an important role in fatty metabolism. However, most of previous studies were based on rats and rarely on piglets. The present study was conducted to investigate the effect of high levels of zinc on the metabolism of hepatic fatty acids. One hundred and twenty crossed-bred (Duroc×Landrace×Yorkshine) piglets with initial body weight at 26.66±2.45 kg were randomly allocated into four dietary treatments received corn-soybean meal-based diets with supplementation of 60 mg/kg,300 mg/kg,1000 mg/kg and 3000 mg/kg of Zn from ZnSO4, and respectively set as the.control group, group 1, group2 and trial group3. There were 3 replicates in each dietary treatment and 10 piglets per each replicate, which were fed for 16 days after a 7-day adaptation period. At the end of the trail, six piglets of each group (24 in total) which were nearly to average weight of that group were selected for slaughter experiment and anatomy observation. The main results were as follows:1 Compared with the control, relative liver weights of group3 enhanced 22.3% (P<0.05); relative femur weights of group 1,2,3 enhanced 13.0%(P<0.05),18.6% (P<0.05),29.4%, respectively; The ADG of trial groupl,2,3 enhanced 16.30%(P<0.05), 28.1%(P<0.05),48.9%(P<0.01).respectively.2 With the increase of zinc addition, Zn concentration of serum and tissue tended to be enhanced. Compared with the control, trial group 2,3 significantly enhanced (P<0.05). while trial groupl did not (P>0.05). Dung Zn concentration in three trial groups all significantly increased when compared with the control (P<0.05)3 Compared with the control, total triglycerids and low density lipoprotein cholesterol (LDL-C) in serum were increased (P<0.05) in all dietary treatment groups, and serum cholesterol was elevated (P<0.05) in the treatment with supplementation of 3000 mg/kg of ZnSO4.4 Compared with the control, the concentrations of Stearate (C18:0) and Octadecadienoic acid (C18:2) were decreased (P<0.05), and Oleate (18:1) levels were increased (P<0.05), but Palmitate (16:0) was unaffected (P>0.05) in the treatment with supplementation of 3000 mg/kg of ZnSO4.5 Compared with the control, levels of Stearoyl CoA desaturease (SCD1) mRNA, plasma leptin and insulin were increased (P<0.05) in the treatment with supplementation of 1000 and 3000 mg/kg of ZnSO4; also, T4 levels tended to be declined (P<0.05) with the increase in dietary zinc supplementation, and an increasing trend was shown in the levels of T3 and glucagon but the differences did not reach statistical significance (P>0.05).In conclusion, high levels of zinc up-regulated the transcription of SCD-1, repressed the transcription of PPARa, and enhanced the desaturation of C18:0 and synthesis of triglycerid as well as cholesterol. Moreover, high levels of zinc could regulate the metabolism of hepatic fatty acids by stimulating the secreation of leptin and insulin.