Mitochondrial CD36 expression is increased in endothelial cells exposed to elevated glucose in vitro
Authors: Johnson Erica , Nguyen Thanh , Fancher Ibra 
Published: May 2023

Background and Objective: Obesity is a multifactorial metabolic disease encompassing several cardiovascular risk factors including hyperglycemia. CD36 is a fatty acid translocase scavenger receptor and a glycoprotein which was previously shown to be upregulated by obesity and in response to elevated glucose. Furthermore, recent studies have identified the expression of CD36 in mitochondria of a variety of cell types which, following upregulation of mitoCD36 expression, would have significant impact on cellular respiration. Therefore, we aimed to determine the effect of elevated glucose on mitochondrial CD36 expression in endothelial cells in vitro. Methods: We treated human adipose microvascular endothelial cells (HAMECs) with high glucose (200 mg/dL) and mannitol (osmotic control; 200 mg/dL) for 24, 48, 72, or 96 hours. The control group was maintained in standard media containing 100 mg/dL glucose. Following treatments, CD36 expression was assessed via Western blot, qPCR, flow cytometry and immunocytochemistry (ICC). An antibody targeting an extracellular epitope of CD36 was used to identify membrane expression where appropriate. ICC was performed on distinct groups of nonpermeabilized and permeabilized cells to detect changes in membrane vs. internal expression, respectively. Mitochondria were isolated from HAMECs using positive selection of TOM40 via magnetic associated cell sorting. Statistics: A one-way Kruskal Wallis (p < 0.05) was used followed by Dunn Sidak post hoc tests to determine significant differences. Results: HAMECs exposed to elevated glucose exhibited an increase in CD36 expression in total cell lysates and in permeabilized cells after 72 hrs. However, no changes were detected in CD36 membrane expression or in CD36 gene expression in response to elevated glucose suggesting that internal expression of CD36 protein is increased through mechanisms independent of transcription under these conditions. To determine if CD36 expression was elevated specifically in mitochondria following exposure to elevated glucose, mitochondria were isolated and purified from HAMECs. CD36 expression was revealed to be increased in the mitochondrial fraction of glucose treated cells perhaps indicating alterations to mitochondrial respiration in the presence of sustained elevated glucose. Discussion and Conclusions: Our findings reveal that mitochondrial CD36 expression is elevated in endothelial cells exposed to sustained increases in glucose in vitro, which may impact mitochondrial respiration in the presence of other macronutrients like fatty acids. Ongoing studies in our lab are aimed at identifying the functional effects of increased mitoCD36 on endothelial cell respiration when challenged with fatty acids. This study was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under award number 2P20GM113125 (Ibra Fancher). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.