The objective of the research was to identify the presence of adiponectin receptors and to study adiponectin action on glucose uptake and growth in mouse mammary epithelial cells. These cells expressed adiponectin receptors, AdipoR1 and AdipoR2. Insulin (10 ng/ml) or insulin like growth factor-I (IGF-I, 10 ng/ml) alone did not alter the degree of AdipoR1 and AdipoR2 genes expression from 0 to 4 h incubation. Prolactin (10 ng/ml) or epidermal growth factor (EGF, 10 ng/ml) alone also did not induce the two genes’ mRNA in the incubation time. Adiponectin (1 μg/ml) alone or pre-incubation of insulin alone (100 ng/ml) for 2 h prior to adiponectin stimulation did not increase 2-deoxy-D-glucose,[1,2-3H] uptake but adiponectin+pre-incubation of insulin significantly increased glucose uptake compare to control (p<0.05). In a similar way, insulin alone or pre-incubation of adiponectin alone (2 h) did not increase glucose uptake but insulin+pre-incubation of adiponectin increased glucose uptake compare to control (p<0.05). Insulin sensitization for 2 h prior to adiponectin stimulation tended to increase glucose uptake response by the following adiponectin stimulation showing small interaction effect between insulin and adiponectin (p<0.1). However, adiponectin sensitization for 2 hours prior to insulin stimulation did not shown interaction effect between adiponectin and insulin (p>0.1). The glucose uptake by both of hormones seems to be not interactive but additive (p<0.05). Adiponectin in the presence of 2% FBS decreased DNA synthesis of mammary epithelia (p<0.05). AICAR (100 or 200 μM), AMPK activator, decreased mammary epithelial cell growth in the presence of 2% FBS. These results indicate that adiponectin pathway has inhibitory effect on mammary epithelial cell growth.

The insulin-like growth factor (IGF) pathway is a key signal transduction pathway involved in cell proliferation, migration, and apoptosis. In dairy cows, IGF family proteins and binding receptors, including their intracellular binding partners, regulate mammary gland development. IGFs and IGF receptor interactions in mammary glands influence the early stages of mammogenesis, i.e., mammary ductal genesis until puberty. The IGF pathway includes three major components, IGFs (such as IGF-I, IGF-II, and insulin), their specific receptors, and their high-affinity binding partners (IGF binding proteins [IGFBPs]; i.e., IGFBP1–6), including specific proteases for each IGFBP. Additionally, IGFs and IGFBP interactions are critical for the bioactivities of various intracellular mechanisms, including cell proliferation, migration, and apoptosis. Notably, the interactions between IGFs and IGFBPs in the IGF pathway have been difficult to characterize during specific stages of bovine mammary gland development. In this review, we aim to describe the role of the interaction between IGFs and IGFBPs in overall mammary gland development in dairy cows.