Oral Presentation The 13th International Congress of the Immunology of Diabetes Society 2013

Endogenous IL-22 is an Intrinsic Suppressor of β-cell ER Stress and Islet Inflammation and Exogenous IL-22 Restores Glycaemic Control in Obesity (#39)

Sumaira Z Hasnain 1 , Brooke Harcourt 1 , Danielle J Borg 1 , Hui Tong 1 , Choa Ping Ng 1 , Indrajit Das 1 , Ran Wang 1 , Alice CH Chen 1 , Josephine Forbes 1 , Jon Whitehead 1 , John B Prins 1 , Michael McGuckin 1
  1. Mater Medical Research Institute, Woolloongabba, QLD, Australia

IL-22 is a thought to function mainly in the skin and mucosae where it boosts barrier function and wound repair. However, the IL-22 receptor (IL-22R1) is most highly expressed by secretory cells in the pancreatic islets. In murine MIN6N8 β-cells IL-22 potently suppresses ER stress induced by palmitate, inflammatory cytokines or tunicamycin, in a STAT1/3-dependent mechanism independent of the unfolded protein response. Healthy murine islets cultured in IL-22R1 antibody showed increased ER stress and decreased glucose-stimulated insulin secretion (GSIS), demonstrating that IL-22-IL-22R1 signalling is a component of normal islet function. Healthy islets exposed to ER stress-inducing cytokines or tunicamycin had diminished GSIS, however co-culture with IL-22 prevented ER stress and normalised GSIS. In contrast, in islets from mice with high fat diet induced obesity (HFDIO) which showed chronic ER stress and hypersecretion of insulin, IL-22 suppressed ER stress and reduced GSIS to that seen in non-obese islets. Obese islets show increased expression of multiple innate effector cytokines and the chemokine Mip2α that exacerbate ER stress. Ex vivo exposure to IL-22 significantly reduced Mip2α expression which is likely to suppress islet leukocyte recruitment and activation. HFDIO mice treated with IL-22 normalised random fed blood glucose within 7 days and showed normal glucose tolerance and fasting insulin by 2 weeks, at which time insulin resistance was unchanged. However, by 4 weeks of treatment insulin sensitivity was largely restored. Islets from IL-22-treated obese mice showed greatly reduced proinsulin secretion in response to challenge with glucose and GLP-1. These islets also had near complete suppression of ER stress and inflammation, increased stored insulin and decreased proinsulin. Taken together these data suggest that IL-22 is a natural regulator of β-cell insulin biosynthesis and secretion, protecting the β-cell from stress, preventing hypersecretion of poor quality insulin, and blocking the development of innate islet inflammation.