People with severe type 1 diabetes (T1D) are known to experience life-threatening hypoglycemic events as a result of alpha cell dysfunction. The phenomenon that causes α cell dysfunction is still unclear. It has been reported that β-cells regulate α cells via paracrine signaling but the underlying mechanism still remains elusive. Extracellular vesicles (EVs) are a class of small vesicles (30-2000nm) that contain a variety of biomolecules. α and β-cells in the islets have been shown to release EVs. It is hypothesized that β-cells transfer signals via EVs in order to regulate α-cell function. Loss of β-cells results in a lack of exosomal communication that causes α-cell dysfunction. Here, we investigated the role of β-cell EVs in modulating α cell function. Mouse TC1-α and βTC6 cell lines were stimulated with low and high glucose media for 24h after exosome depletion. EVs were isolated from conditioned media using differential centrifugation methods. EVs were characterized using TEM, NTA analysis, confocal microscopy, and blotting for surface markers. Alpha cells were challenged with low and high glucose conditions in the presence or absence of EVs from β- cells in order to evaluate the role of EVs in glucagon secretion. ELISA was used to measure glucagon levels in the media, q-PCR was performed on glucagon and other regulatory genes such as MafB and c-Maf. The size of EVs based on NTA analysis was found to be 50 - 200nm. Confocal images reveal that the uptake of BODIPY labeled β-cell EVs after 3h was found localized in the nucleus and cytoplasm of α-cells. Under low glucose stimulation, mRNA and protein expression of glucagon in α-cells was significantly increased in the presence of β-cell EVs (6h: P = 0.0134). Expression of mafB which is a regulator of glucagon transcription correlated with glucagon expression. These results suggest a putative role of β-cell EVs in regulating α-cell function. Our findings will aid in developing new approaches for preventing severe hypoglycemic episodes by reversing α-cell dysfunction in T1D.
J. Kalivarathan: None. P. Saravanan: None. M.F. Levy: None. M.A. Kanak: None.