共轭亚油酸对草鱼肝脏和肌肉组织的细胞学形态、抗氧化能力以及脂肪代谢相关基因表达的影响

采用65d的生长实验研究共轭亚油酸(CLA)对草鱼肝脏和肌肉细胞学形态、抗氧化能力以及脂肪代谢相关基因表达的影响。共配制7种近似等氮(粗蛋白: 36 g/100 g)等脂(粗脂肪: 4.5 g/100 g)的饲料: 0 (对照组)、0.5 (CLA0.5)、1 (CLA1)、1.5 (CLA1.5)、2 (CLA2)、2.5 (CLA2.5)和3 g/100 g CLA (CLA3)。每个饲料组均设置3个生物学重复,实验鱼初始体重约为(5.08±0.08) g。实验结果显示:与对照组相比,CLA0.5-CLA2.5组草鱼肝脏和肌肉组织细胞学形态均无明显异常,但CLA3组肝细胞线粒体空泡化,内质网肿胀,排列过于紧密;肌细胞肌节结构松散,肌原纤维降解;在CLA1.5-CLA2.5组肝脏和肌肉中超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)和谷胱甘肽过氧化物酶(GPx)活力均显著上升(P<0.05);在CLA1.5-CLA3组中肝脏过氧化氢酶(CAT)活力均显著高于对照组(P<0.05),但谷胱甘肽还原酶(GR)活力无显著变化(P>0.05),且在CLA0.5-CLA3组中肌肉CAT和GR活力均无显著变化(P>0.05)。CLA1.5-CLA2组肝脏中MDA含量显著低于对照组(P<0.05),而CLA2.5-CLA3组MDA含量显著高于对照组(P<0.05)。CLA3组肌肉中MDA含量显著高于对照组(P<0.05)。与对照组相比,在CLA1.5-CLA2.5组肝脏和肌肉中乙酰辅酶A羧化酶(ACC) mRNA表达显著下调(P<0.05),脂蛋白脂酶(LPL)、激素敏感性脂肪酶(HSL)和过氧化物酶体增殖物激活受体α(PPARα)均显著上调表达(P<0.05)。在CLA2-CLA3组肝脏以及CLA1.5-CLA2和CLA3组肌肉中脂肪酸去饱和酶2(FAD2)mRNA显著上调表达(P<0.05)。过氧化物酶体增殖物激活受体γ(PPARγ)mRNA在CLA1-CLA3组肝脏中显著下调表达(P<0.05),而其在肌肉中均无显著变化(P>0.05)。综上所述,结合2%CLA在不影响草鱼的生长和饲料利用,且显著降低肝脏脂肪积累,研究结果建议,2% CLA在不影响草鱼肝脏和肌肉组织细胞学形态的前提下,可有效提高其肝脏和肌肉组织抗氧化能力并促进其脂肪分解代谢以及抑制脂肪合成代谢相关基因表达。

EFFECTS OF DIETARY CLA ON CYTOLOGICAL MORPHOLOGY,ACTIVITY OF ANTIOXIDANT ENZYMES,AND GENE EXPRESSIONS OF LIPID METABOLISM IN THE LIVER AND MUSCLE OF GRASS CARP

A 65-day trial was conducted to investigate effects of CLA on cytological morphology, activity of antioxidant enzymes, and gene expressions of lipid metabolism in the liver and muscle of grass carp. Seven isonitrogenous (crude protein: 36 g/100 g) and isolipidic (crude lipid: 4.5 g/100 g) diets were formulated: 0 CLA (control), 0.5% (CLA0.5), 1% (CLA1), 1.5 (CLA1.5), 2 (CLA2), 2.5 (CLA2.5), and 3% CLA (CLA3). Three biological replicates of fish were assigned to each diet with the initial body weight at (5.08±0.08) g. Endoplasmic reticulum in the liver, and loose sarcolemma of myocyte and degradation of myofibril in the muscle when compared with the control fish. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and the total antioxidant capacity (T-AOC) both in the liver and muscle of CLA1.5-CLA2.5 groups significantly (P<0.05) increased compared with control group. The activities of catalase (CAT) in the liver of CLA1.5-CLA3 groups were significantly (P<0.05) higher than that of control group, however, there was no significant (P>0.05) change in the glutathione reductase (GR) activity in the liver. The MDA contents in the liver of fish fed with CLA1.5-CLA2 diets were significantly (P<0.05) lower than that of control group, however, the MDA contents in the liver of fish fed with CLA2.5-CLA3 diets significantly (P<0.05) increased compared with control group. In contrast, fish fed with CLA3 had significantly higher MDA contents in the muscle (P<0.05) compared with control group. Compared with the control fish, the mRNA level of acetyl-CoA carboxylase (ACC) both in the liver and muscle of fish fed with CLA1.5-CLA2.5 diets were significantly (P<0.05) down-regulated; the mRNA levels of lipoprotein lipase (LPL), hormone-sensitive lipase (HSL), and peroxisome proliferator-activated receptor alpha (PPARα) of fish fed with CLA1.5-CLA2.5 diets were significantly (P<0.05) up-regulated; the mRNA levels of fatty acid desaturase 2 (FAD2) in the liver of fish fed with CLA2-CLA3 diets and in the muscle of fish fed with CLA1.5-CLA2 and CLA3 diets were significantly (P<0.05) up-regulated; the mRNA level of peroxisome proliferator-activated receptor gamma (PPARγ) in the liver of fish fed with CLA1-CLA3 diets was significantly (P<0.05) down-regulated. Conversely, there was no significant (P>0.05) difference for the PPARγ mRNA level in the muscle of fish fed with CLA0.5-CLA3 diets. In conclusion, supplementation of 2% CLA could significantly decrease the lipid contents in the liver and muscle without affecting cytological morphology of liver and muscle, the growth and feed utilization of grass carp by improving the antioxidant capacities in the liver and muscle.