Insulin signaling of glucose uptake in skeletal muscle of lactating dairy cows

摘要

Insulin response in skeletal muscles is thought to be impaired in dairy cows during early lactation to favor nutrient supply, especially glucose, towards the mammary gland. However, the molecular mechanisms of insulin action on glucose metabolism in cows and in other ruminants are still not completely understood, particularly during early lactation. Previous studies provide evidence that peripartal insulin resistance in skeletal muscle of ruminants is caused by post-receptor changes of the insulin signaling pathway. The protein content of glucose transporter 4 (GLUT4) is reduced in skeletal muscle of goats and cows at begin of lactation (Balage et al, 1997; Kuhla et al, 2011). On the other hand, lactation does not have an effect on the number, the affinity or the activity of the tyrosine kinase of the insulin receptor (InsR) in sheep (Wilson et al, 1996) and goats (Balage et al, 1992). Furthermore, Duhlmeier et al (2005) showed differences in protein amount of GLUT 1 and 4 in oxidative and glycolytic muscles of lactating cows. We have tested the hypothesis that insulin signaling in skeletal muscle of daily cows is related to the stage of lactation and differs among various muscle types. Furthermore, we have investigated the influence of differentpost-calving metabolic status of dairy cows as reflected by divergent fat mobilization and liver fat concentration (LFC) on insulin signaling in muscle tissue.