RAF1 and Insulin resistance: Because the mitogenic mitogen-activated protein kinase (MAPK) signaling cascade via Ras, Raf, and extracellular signal-regulated kinase (ERK) activation is also involved in insulin resistance in a tissue-dependent manner15, we investigated whether chronic treatment with insulin and hCG could alter levels of phosphorylation-cellular-Raf (p-c-Raf), MAPK kinase (MEK) 1/2, and ERK1/2 (Fig. 5A).