Pancreatic β cells control glucose homeostasis via the secretion of exosomal miR‐29 family

Secreted microRNAs (miRNAs) are novel endocrine factors that play essential pathological and physiological roles. Here, we report that pancreatic β cell-released exosomal miR-29 family members (miR-29s) regulate hepatic insulin sensitivity and control glucose homeostasis. Cultured pancreatic islets were shown to secrete miR-29s in response to high levels of free fatty acids (FFAs) in vitro. In vivo, high levels of FFAs, promoted by either high-fat diet (HFD) feeding (physiopathological) or fasting (physiological), increased the secretion of miR-29s into plasma. Intravenous administration of exosomal miR-29s attenuated insulin sensitivity. The overexpression of miR-29s in the β cells of transgenic (TG) mice promoted the secretion of miR-29s and inhibited the insulin-mediated suppression of glucose output in the liver. We used selective overexpression of traceable heterogenous mutant miR-29s in β cells to confirm that islet-derived exosomal miR-29s target insulin signalling in the liver and blunt hepatic insulin sensitivity. Moreover, in vivo disruption of miR-29s expression in β cells reversed HFD-induced insulin resistance. In vitro experiments demonstrated that isolated exosomes enriched in miR-29s inhibited insulin signalling in the liver and increased hepatic glucose production. These results unveil a novel β cell-derived secretory signal-exosomal miR-29s-and provide insight into the roles of miR-29s in manipulating glucose homeostasis.