(65e) Endothelial Modulation of Adiponectin Oligomer Transport and Function

Adiponectin has exhibited positive effects in regulating of systemic metabolism and insulin sensitivity through tissues such as liver, skeletal muscle, and centrally in the brain. With the ability to form high molecular weight (HMW) oligomers and circulating molecules of 30 to potentially 1080 kDa, adiponectin must cross the endothelium to have metabolic effects. Our laboratory has reported differential efficacy of these oligomers on insulin sensitivity and clinical data suggest that the HMW form is most important for metabolic health. Recent data has also demonstrated oligomer size-dependence on adiponectin clearance. Here, we have produced all oligomers of adiponectin in mammalian cells and used FPLC to fractionate adiponectin by molecular size. We have measured the Stokes radii of adiponectin to be approximately 5, 10, and 25nm for the trimeric, hexameric, and high molecular weight (HMW) forms, respectively. These molecular transport sizes, particularly that of the HMW, present transport limitations across endothelial barriers with low intercellular permeabilities such as in muscle or in the brain. Model murine MS1, bEnd.3, and EOMA endothelial cell lines were used in in vitro transwell permeability studies to calculate the relative transport of oligomers across different endothelium. We demonstrate size-dependent exclusion of adiponectin oligomers in MS1 and bEnd.3 cells, and in EOMA cells, a microvascularture model, equivalent transport of trimeric and HMW adiponectin for their diffusive sizes. Each cell type had notable differences in the amount of intracellular adiponectin at the experiments’ end; expression of adiponectin receptors correlated with internalization. Cells transfected with T-cadherin demonstrated increased surface binding. In total, these findings suggest active adiponectin transport mechanisms. In vivo, increasing vessel permeability pharmacologically, or through inducible transgenic overexpression of VEGF, reduced the circulatory half-life of adiponectin. These data demonstrate that the effects of different adiponectin oligomers on tissue metabolism may depend on the distinct endothelial character of a given tissue.