Delavaud C, Ferlay A, Faulconnier Y, Bocquier F, Kann G, Chilliard Y
Unité de Recherche sur les Herbivores, Equipe Tissu Adipeux et Lipides du Lait, INRA-Theix, Saint-Genès-Champanelle, France.
J Anim Sci. 2002 May;80(5):1317-28. doi: 10.2527/2002.8051317x.
An ovine-specific RIA, shown to be reliable for bovine leptin determination, was used to study the effects of breed, body fatness, feeding level, and meal intake on plasma leptin level in adult cattle. Eighteen fat Charolais, fat Holstein, and lean Holstein adult cows were either well-fed (130% of maintenance energy requirements [MER]) or underfed (60% of MER) for 3 wk. The breed tended to have a small effect on plasma leptin level, which was decreased by 70% (P < 0.05) in lean compared to fat Holstein cows. A strong curvilinear relationship was found between mean adipocyte volume and plasma leptin concentrations in well-fed (r = +0.95) and underfed (r = +0.91) cows. Underfeeding caused a significant decrease in plasma leptin levels from 8.0+/-3.1 to 6.1+/-2.3 ng/mL (P < 0.01). Nine adult Holstein cows initially fed at 130% of MER (control) were underfed to 21% of MER for 7 d, and five of them were refed to 237% of MER for 21 d. Plasma leptin measured 1 h before meal distribution was decreased from 5.9+/-0.4 to 3.8+/-0.2 ng/mL (P < 0.01) by underfeeding and increased to reach 8.8+/-1.0 ng/mL (P < 0.01) after refeeding. It was positively related to plasma glucose (r = +0.52, P < 0.01) and negatively related to plasma NEFA (r = -0.67, P < 0.001). Plasma leptin measured 4 h after meal distribution was positively related to feeding level and to plasma 3-OH-butyrate (r = +0.61, P < 0.005) and negatively related to plasma NEFA (r = -0.56, P < 0.01). Differences between pre- and postprandial leptin concentrations showed a decrease after meal intake in control and well-fed cows (-7 and -19%, P < 0.01, respectively) and an increase in underfed cows (+12%, P < 0.01). Leptin response to meal intake was positively related to glucose response (r = +0.66, P < 0.001) and negatively related to 3-OH-butyrate response (r = -0.78, P < 0.001). By using the "multispecies" commercial RIA, leptin concentrations were lower and we observed similar physiological responses, although less related to other hormones or metabolites. These data provide evidence, first, that a specific RIA for ruminant leptin determination is necessary to better understand leptin regulation, and second, that plasma leptin is strongly related to adipose cell size and positively related to feeding level in adult cattle, and that an effect of meal intake could be mediated by glucose and(or) ketone bodies.
一种对牛瘦素测定可靠的绵羊特异性放射免疫分析方法(RIA),被用于研究品种、体脂率、饲养水平和采食量对成年牛血浆瘦素水平的影响。18头夏洛莱肥母牛、荷斯坦肥母牛和荷斯坦瘦母牛,分别按维持能量需要量(MER)的130%(饱饲)或60%(限饲)饲养3周。品种对血浆瘦素水平影响较小,与荷斯坦肥母牛相比,荷斯坦瘦母牛的血浆瘦素水平降低了70%(P<0.05)。在饱饲(r = +0.95)和限饲(r = +0.91)母牛中,平均脂肪细胞体积与血浆瘦素浓度之间存在很强的曲线关系。限饲使血浆瘦素水平从8.0±3.1显著降至6.1±2.3 ng/mL(P<0.01)。9头成年荷斯坦母牛最初按MER的130%(对照)饲养,限饲至MER的21%持续7天,其中5头在随后21天再饲至MER的237%。餐前1小时测定的血浆瘦素水平,限饲使其从5.9±0.4降至3.8±0.2 ng/mL(P<0.01),再饲后升至8.8±1.0 ng/mL(P<0.01)。它与血浆葡萄糖呈正相关(r = +0.52,P<0.01),与血浆非酯化脂肪酸呈负相关(r = -0.67,P<0.001)。餐后4小时测定的血浆瘦素与饲养水平、血浆3-羟基丁酸呈正相关(r = +0.61,P<0.005),与血浆非酯化脂肪酸呈负相关(r = -0.56,P<0.01)。对照和饱饲母牛餐后瘦素浓度的差异显示降低(分别为-7%和-19%,P<0.01),限饲母牛则升高(+12%,P<0.01)。瘦素对采食的反应与葡萄糖反应呈正相关(r = +0.66,P<0.001),与3-羟基丁酸反应呈负相关(r = -0.78,P<0.001)。使用“多物种”商业RIA时,瘦素浓度较低,我们观察到类似的生理反应,尽管与其他激素或代谢物的相关性较小。这些数据首先证明,需要一种用于反刍动物瘦素测定的特异性RIA,以更好地理解瘦素调节;其次证明,成年牛血浆瘦素与脂肪细胞大小密切相关,与饲养水平呈正相关,采食的影响可能由葡萄糖和(或)酮体介导。