Chronic tissue inflammation resulting from obesity is an underlying cause of insulin resistance and type 2 diabetes. But the mechanism by which this occurs has remained cloaked, until now. In a paper, published in the journal Cell on September 21, 2017, University of California San Diego School of Medicine researchers identified exosomes — extremely small vesicles or sacs secreted from most cell types — as the missing link. The article is titled “Adipose Tissue Macrophage-Derived Exosomal miRNAs Can Modulate In Vivo and In Vitro Insulin Sensitivity.” “The actions induced by exosomes as they move between tissues are likely to be an underlying cause of intercellular communication causing metabolic derangements of diabetes,” said Jerrold Olefsky, MD, Professor of Medicine in the Division of Endocrinology and Metabolism at UC San Diego School of Medicine and senior author of the paper. “By fluorescently labeling cells, we could see exosomes and the microRNA they carry moving from adipose (fat) tissue through the blood and infiltrating muscle and liver tissues.” During chronic inflammation, the primary tissue to become inflamed is adipose tissue. Forty percent of adipose tissue in obesity is comprised of macrophages — specialized immune cells that promote tissue inflammation. Macrophages in turn create and secrete exosomes. When exosomes get into other tissues, they use the microRNA (miRNA) they carry to induce actions in the recipient cells.
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