RAC1 and Hyperglycemia: In our experiments in vitro and in vivo, GGTase-I deficiency in VSMCs inhibited Rac1 activation stimulated by hyperglycemia but had no effect on the expression of total Rac1, proving in turn that knockout of GGTase-I only affected the activating process of small GTP-binding protein Rac1, possibly via inhibition of its geranylgeranylation.