Eguinoa P, Brocklehurst S, Arana A, Mendizabal J A, Vernon R G, Purroy A
Departamento Producción Agraria, Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona, Spain.
J Anim Sci. 2003 Feb;81(2):432-40. doi: 10.2527/2003.812432x.
The effects of sex, genotype, and adipose depot on lipogenic enzyme activity have been investigated in Holstein and Pirenaican bulls and heifers, taking into account differences in adipocyte size. Fifteen Pirenaican bulls and 15 heifers and 15 Holstein bulls and 13 heifers were fattened until slaughter (12 to 13 mo old and 450 to 500 kg of body weight). During the fattening period, animals had ad libitum access to commercial concentrates and straw. The 10th rib was dissected to determine the fat content. Adipocyte size and activities of the following lipogenic enzymes were determined: glycerol 3-phosphate dehydrogenase, fatty acid synthase, nicotinamide adenine dinucleotide phosphate (NADP)-malate dehydrogenase, glucose 6-phosphate dehydrogenase, and NADP-isocitrate dehydrogenase, in the omental, perirenal, subcutaneous, and intermuscular adipose depots, respectively. Because adipocyte mean cell volume varied with sex, breed, and depot, regression analyses of log(e) activity per cell and log(e) cell volume were used to compare activities per unit volume. Sex, breed and depot had no effect (P > 0.05) on the gradients of regressions, which did not differ significantly from 1. Thus, activity per unit volume did not vary with cell size. Consequently, sex, breed, and depot effects on the regression analyses were equivalent to effects on activity per unit volume. Females had greater amounts of fat in the 10th rib (P < 0.001), larger adipocytes (P < 0.001) and, in general, greater (P < 0.05) lipogenic activity per cell, even when adjusted for cell size, than males. These findings suggest that differences in adiposity between sexes are mainly due to females having a greater capacity for lipid synthesis, and hence, hypertrophy, than males. When adjusted for differences in carcass weight, Holsteins had larger adipocytes than Pirenaicans. The abdominal depots, omental and perirenal, had a greater adipocyte size (P < 0.001) and, in general, greater lipogenic enzyme activities per cell (P < 0.05) than the subcutaneous and intermuscular carcass depots. However, when activity per cell was adjusted for cell size, subcutaneous depots had greater fatty acid synthae, glucose 6-phosphate dehydrogenase, and NADP-malate dehydrogenase activities than omental and perirenal, indicating that other factors such as nutrient supply may restrict hypertrophy of carcass adipocytes.
在荷斯坦公牛和皮雷纳公牛及母牛中，研究了性别、基因型和脂肪储存部位对生脂酶活性的影响，并考虑了脂肪细胞大小的差异。15头皮雷纳公牛、15头母牛、15头荷斯坦公牛和13头母牛被育肥至屠宰（12至13月龄，体重450至500千克）。育肥期内，动物可自由采食商业浓缩饲料和秸秆。解剖第10肋骨以测定脂肪含量。分别测定网膜、肾周、皮下和肌间脂肪储存部位的脂肪细胞大小以及以下生脂酶的活性：3 - 磷酸甘油脱氢酶、脂肪酸合酶、烟酰胺腺嘌呤二核苷酸磷酸（NADP）-苹果酸脱氢酶、6 - 磷酸葡萄糖脱氢酶和NADP -异柠檬酸脱氢酶。由于脂肪细胞平均细胞体积随性别、品种和储存部位而变化，因此使用每个细胞的活性对数（e）和细胞体积对数（e）的回归分析来比较单位体积的活性。性别、品种和储存部位对回归梯度无影响（P>0.05），回归梯度与1无显著差异。因此，单位体积的活性不随细胞大小而变化。因此，性别、品种和储存部位对回归分析的影响等同于对单位体积活性的影响。雌性第10肋骨中的脂肪量更多（P<0.001），脂肪细胞更大（P<0.001），并且一般来说，即使在根据细胞大小进行调整后，每个细胞的生脂活性也更高（P<0.05）。这些发现表明，两性之间肥胖程度的差异主要是由于雌性比雄性具有更大的脂质合成能力，因此脂肪细胞肥大。在根据胴体重量差异进行调整后，荷斯坦牛的脂肪细胞比皮雷纳牛的更大。腹部储存部位，即网膜和肾周，脂肪细胞更大（P<0.001），并且一般来说，每个细胞的生脂酶活性更高（P<0.05），比皮下和肌间胴体储存部位高。然而，当根据细胞大小调整每个细胞的活性时，皮下储存部位的脂肪酸合酶、6 - 磷酸葡萄糖脱氢酶和NADP -苹果酸脱氢酶活性比网膜和肾周更高，这表明营养供应等其他因素可能会限制胴体脂肪细胞的肥大。
