Endothelial Fcγ Receptor IIB Activation Blunts Insulin Delivery to Skeletal Muscle to Cause Insulin Resistance in Mice

Modest elevations in C-reactive protein (CRP) are associated with type 2 diabetes. We previously revealed in mice that increased CRP causes insulin resistance and mice globally deficient in the CRP receptor Fc gamma receptor IIB (Fc gamma RIIB) were protected from the disorder. Fc gamma RIIB is expressed in numerous cell types including endothelium and B lymphocytes. Here we investigated how endothelial Fc gamma RIIB influences glucose homeostasis, using mice with elevated CRP expressing or lacking endothelial Fc gamma RIIB. Whereas increased CRP caused insulin resistance in mice expressing endothelial Fc gamma RIIB, mice deficient in the endothelial receptor were protected. The insulin resistance with endothelial Fc gamma RIIB activation was due to impaired skeletal muscle glucose uptake caused by attenuated insulin delivery, and it was associated with blunted endothelial nitric oxide synthase (eNOS) activation in skeletal muscle. In culture, CRP suppressed endothelial cell insulin transcytosis via Fc gamma RIIB activation and eNOS antagonism. Furthermore, in knock-in mice harboring constitutively active eNOS, elevated CRP did not invoke insulin resistance. Collectively these findings reveal that by inhibiting eNOS, endothelial Fc gamma RIIB activation by CRP blunts insulin delivery to skeletal muscle to cause insulin resistance. Thus, a series of mechanisms in endothelium that impairs insulin movement has been identified that may contribute to type 2 diabetes pathogenesis.