Oliveira D M, Chalfun-Junior A, Chizzotti M L, Barreto H G, Coelho T C, Paiva L V, Coelho C P, Teixeira P D, Schoonmaker J P, Ladeira M M
Department of Animal Science, Universidade Federal de Lavras, Lavras, Minas Gerais, Brazil, 37.200-000.
Department of Biology, Universidade Federal de Lavras, Lavras, Minas Gerais, Brazil, 37.200-000.
J Anim Sci. 2014 Dec;92(12):5426-36. doi: 10.2527/jas.2014-7855. Epub 2014 Nov 17.
Degree of unsaturation of fatty acids, which is influenced by lipid source and level of metabolism in the rumen, is a major determinant in how dietary lipids affect genes that regulate beef marbling. A total of 28 Red Norte bulls with an initial live weight of 361±32 kg (P>0.05) were used in a completely randomized experimental design to analyze the expression of genes that are involved in lipid metabolism in the longissimus dorsi (LD) when diets contained soybean grain or rumen-protected fat, with or without monensin. Treatments were arranged as a 2×2 factorial, with 4 treatments and 7 replicates per treatment. Half of the animals that received soybean or rumen-protected fat were supplemented with 230 mg head(-1) d(-1) of monensin. Gene expression was analyzed by reverse-transcription quantitative PCR (RT-qPCR). Expression of sterol regulatory element-binding protein-1c (SREBP-1c) in the LD muscle was not affected by lipid source or monensin (P>0.05). There was an interaction effect (P<0.05) between lipid source and monensin for peroxisome proliferator-activated receptor α (PPAR-α) and stearoyl-CoA desaturase (SCD) expression, where greater gene expression was found in animals fed soybean plus monensin and the lower gene expression was found in animals fed rumen-protected fat plus monensin. Expression of lipoprotein lipase (LPL) and fatty acid-binding protein 4 (FABP4) were greater (P<0.05) in the LD muscle of animals fed soybean. Monensin had no effect on LPL and FABP4 expression when soybean without monensin was fed, but when rumen-protected fat was fed, monensin increased LPL expression and decreased FABP4 expression (P<0.05). Linoleic and arachidonic acids had negative correlations (P<0.05) with the expression of PPAR-α, SCD, FABP4, and LPL genes. PPAR-α gene expression was not correlated with SREBP-1c but was positively correlated with SCD, FABP4, LPL, and glutathione peroxidase (GPX1) gene expression (P<0.001). Lipid sources and monensin interact and alter the expression of PPAR-α, SCD, acetyl CoA carboxylase α (ACACA), LPL, FABP4, and GPX1. These changes in gene expression were most associated with arachidonic and α-linolenic acids and the ability of lipid sources and monensin to increase these fatty acids in tissues.
脂肪酸的不饱和度受脂质来源和瘤胃代谢水平的影响，是日粮脂质影响调节牛肉大理石花纹的基因的主要决定因素。采用完全随机试验设计，选用28头初始体重为361±32 kg（P>0.05）的红北公牛，分析日粮含有大豆粕或瘤胃保护脂肪且添加或不添加莫能菌素时，背最长肌（LD）中参与脂质代谢的基因表达情况。处理按2×2析因设计，有4种处理，每种处理7个重复。接受大豆粕或瘤胃保护脂肪的动物中有一半补充230 mg/头·天的莫能菌素。通过逆转录定量PCR（RT-qPCR）分析基因表达。LD肌肉中固醇调节元件结合蛋白-1c（SREBP-1c）的表达不受脂质来源或莫能菌素的影响（P>0.05）。对于过氧化物酶体增殖物激活受体α（PPAR-α）和硬脂酰辅酶A去饱和酶（SCD）的表达，脂质来源和莫能菌素之间存在交互作用（P<0.05），其中饲喂大豆粕加莫能菌素的动物基因表达更高，而饲喂瘤胃保护脂肪加莫能菌素的动物基因表达更低。脂蛋白脂肪酶（LPL）和脂肪酸结合蛋白4（FABP4）在饲喂大豆粕的动物的LD肌肉中的表达更高（P<0.05）。饲喂无莫能菌素的大豆粕时，莫能菌素对LPL和FABP4的表达没有影响，但饲喂瘤胃保护脂肪时，莫能菌素增加LPL的表达并降低FABP4的表达（P<0.05）。亚油酸和花生四烯酸与PPAR-α、SCD、FABP4和LPL基因的表达呈负相关（P<0.05）。PPAR-α基因表达与SREBP-1c不相关，但与SCD、FABP4、LPL和谷胱甘肽过氧化物酶（GPX1）基因表达呈正相关（P<0.001）。脂质来源和莫能菌素相互作用并改变PPAR-α、SCD、乙酰辅酶A羧化酶α（ACACA）、LPL、FABP4和GPX1的表达。基因表达的这些变化与花生四烯酸和α-亚麻酸以及脂质来源和莫能菌素在组织中增加这些脂肪酸的能力最相关。
