Gene expression of resistin in adipose tissue and mammary gland of lactating and non-lactating cows.

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.