Rokka, Sabita

Obesity is a complex metabolic disease that is the leading risk factor for cardiovascular disease. In obesity, adipose arteries exhibit robust endothelial dysfunction (ED). A major hallmark of ED is loss in flow induced vasodilation (FIV). Kir2.1 is an inwardly rectifying K+ channel that contributes to FIV through the downstream production of nitric oxide, a potent vasodilator. Work from our group demonstrated that in addition to loss in FIV, endothelial cells (ECs) isolated from obese mice exhibited blunted Kir2.1 currents. Plasma long chain fatty acids (LCFAs) are well established to be elevated in obesity and have been separately shown to inhibit Kir2.1 channels. CD36 is the major fatty acid translocase responsible for the uptake of LCFAs and we therefore aimed to determine if CD36 was contributing to this loss in Kir2.1 function. We previously showed that global CD36 ablation restores endothelium-dependent dilations to flow. These findings prompted us to explore the role of EC CD36 in negatively regulating Kir2.1 function. We performed patch clamp electrophysiology experiments on freshly isolated ECs from the Tie2eCreCD36fl/fl model and determined that EC CD36 ablation restores Kir2.1 currents in obesity. To further explore the established relationship between Kir2.1 and FIV, we performed ex vivo pressure myography experiments to evaluate endothelial dependent dilations to flow. EC CD36 ablation restored responses to flow in arteries from obese mice, an effect that could be blunted by inhibiting Kir2.1 suggesting that CD36 ablation in endothelium rescues the Kir2.1 contribution to FIV. To determine if obesity alters the expression of endothelial CD36, arteries from mice and humans undergoing bariatric surgery were isolated and en face preparations were stained to locate the EC layer and assess CD36 expression. Confocal imaging of en face arteries coupled with flow cytometry on isolated endothelial cells revealed that obesity did not alter the expression of CD36 in endothelium of mesenteric arteries relative to controls in WT mice or humans. As expression did not change, we next probed functionality of CD36 in obese vs. control in mice and humans. Arteries were exposed to a fluorescent fatty acid, BODIPY C-16, at various time points followed by en face preparations and confocal microscopy. As expected, obese vessels exhibited elevated amounts of fatty acid uptake (FAU) at all time points relative to control in mice and humans, suggesting an increase in CD36. To further confirm this change in function, we repeated FAU experiments in the Tie2eCreCD36fl/fl model and found that EC CD36 ablation attenuated FAU in obese vessels compared to both their lean and genotype controls. Taken together, this work suggests that an increase in CD36 function drives impairment of Kir2.1. This work establishes a CD36/Kir2.1 axis worthy of further exploration including understanding how CD36 and LCFAs are impairing Kir2.1 upstream. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Obesity is a prevalent metabolic condition that is strongly associated with the development of cardiovascular disease. Adipose arteries exhibit robust endothelial dysfunction in diet-induced obese mice. Obesity is also associated with elevated plasma long chain fatty acids (LCFAs), well-established contributors to endothelial dysfunction, which require a receptor to facilitate their uptake. CD36, facilitates LCFA uptake which when in excess contributes to endothelial dysfunction. Our previous work demonstrated that global CD36 ablation restores endothelium-dependent dilations to flow. Therefore, to determine if an upregulation in CD36 expression was driving these differences, we first assessed if obesity alters endothelial CD36 expression using flow cytometry and immunofluorescence imaging. For flow cytometry experiments mesenteric arteries were digested and sorted to identify the endothelial cell population (i.e., CD45-CD31+ cells). En face preparations were stained for VE-cadherin to locate the endothelial cell layer using confocal microscopy. In both experiments, an antibody that detects an extracellular epitope of CD36 was used to detect membrane expression. Obesity did not alter the expression of CD36 in endothelium of mesenteric arteries relative to lean counterpart controls in WT mice. We next aimed to determine if obesity influences the functional capacity of endothelial CD36. First, we measured LCFA uptake in mesenteric arteries from lean and obese WT mice. Arteries were exposed to a fluorescent palmitic acid analogue, BODIPYC-16, and internalized endothelial LCFA uptake was assessed at different time points using confocal microscopy. Arteries from obese mice had elevated endothelial LCFA uptake and lipid accumulation relative to lean controls. To determine if the effects of obesity on LCFA uptake were mediated by endothelial CD36, we repeated the fluorescent LCFA uptake experiments using the Tie2eCreCD36 fl/fl model. First, to determine if endothelial cell CD36 was driving obesity induced endothelial dysfunction, mesenteric arteries were isolated from lean and diet-induced obese Tie2eCreCD36 fl/fl mice. Arteries from Tie2eCreCD36 fl/fl diet induced obese mice exhibited attenuated fatty acid uptake, compared to their lean and obese genotype controls. Next, we measured endothelial function ex vivo via pressure myography. Mesenteric arteries from obese Tie2eCreCD36 fl/fl mice exhibited a restored response to flow induced vasodilation relative to respective controls suggesting a role for endothelial cell CD36 in mediating endothelial dysfunction perhaps through promoting lipid accumulation in obesity. Ongoing work within our lab is aimed at determining the mechanism underlying obesity-induced alterations to endothelial CD36 and how the observed increase in LCFAs may be contributing to reduced endothelial function. Center of Biomedical Research Excellence in Cardiovascular Health (COBRE): 5P20GM113125-08, University of Delaware Research Fund (UDRF) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.