Komatsu Tokushi, Itoh Fumiaki, Mikawa Satoshi, Hodate Koichi
Department of Animal Physiology and Nutrition, National Institute of Livestock and Grassland Science, Tsukuba Norindanchi, PO Box 5, Ibaraki 305-0901, Japan.
J Endocrinol. 2003 Sep;178(3):R1-5. doi: 10.1677/joe.0.178r001.
Resistin has been suggested to induce insulin resistance in obesity and to inhibit adipocyte differentiation. In lactating cows, glucose uptake in the mammary gland is a rate-limiting step in milk synthesis, and to supply glucose to the mammary gland, insulin resistance increases. We examined the expression of the resistin gene by real-time PCR of cDNA in the adipose tIssue and mammary gland of lactating and non-lactating cows. Lactation induced a significant increase of resistin expression in adipose tIssue compared with that in the dry period, and decreased resistin expression in the mammary gland. There were no significant differences in the expression of insulin responsive glucose transporter (GLUT4) mRNA between the adipose tIssue of lactating and non-lactating cows, and GLUT4 mRNA was not detected in the mammary gland. The plasma insulin concentration was lower in lactating cows than in non-lactating cows. These results indicate that the pattern of resistin expression in peripheral tIssues is changed in association with milk production. The increase of resistin expression and maintenance of a lower level of plasma insulin concentration may decrease glucose availability by increasing insulin resistance in adipose tIssue. Additionally, our results suggest that the decrease of resistin expression in the mammary gland may influence on the insulin-dependent glucose uptake in mammary epithelial cells during lactation.
抵抗素被认为可在肥胖状态下诱导胰岛素抵抗并抑制脂肪细胞分化。在泌乳奶牛中，乳腺对葡萄糖的摄取是乳汁合成中的限速步骤，为了向乳腺供应葡萄糖，胰岛素抵抗会增加。我们通过实时PCR检测了泌乳期和非泌乳期奶牛脂肪组织和乳腺中抵抗素基因的cDNA表达。与干奶期相比，泌乳期脂肪组织中抵抗素的表达显著增加，而乳腺中抵抗素的表达降低。泌乳期和非泌乳期奶牛的脂肪组织中胰岛素反应性葡萄糖转运蛋白（GLUT4）mRNA的表达没有显著差异，且在乳腺中未检测到GLUT4 mRNA。泌乳期奶牛的血浆胰岛素浓度低于非泌乳期奶牛。这些结果表明，外周组织中抵抗素的表达模式会随着产奶量的变化而改变。抵抗素表达的增加和血浆胰岛素浓度维持在较低水平可能会通过增加脂肪组织中的胰岛素抵抗来降低葡萄糖的可用性。此外，我们的结果表明，乳腺中抵抗素表达的降低可能会影响泌乳期乳腺上皮细胞中胰岛素依赖的葡萄糖摄取。
