MANF is required for the postnatal expansion and maintenance of pancreatic B-cell mass in mice

Abstract

Global lack of mesencephalic astrocyte-derived neurotropic factor (MANF) leads to progressive postnatal loss of b-cell mass and insulin-dependent diabetes in mice. Similar to Manf2/2 mice, embryonic ablation of MANF specifically from the pancreas results in diabetes. In this study, we assessed the importance of MANF for the postnatal expansion of pancreatic b-cell mass and for adult b-cell maintenance in mice. Detailed analysis of Pdx-1Cre+/2::Manffl/fl mice revealed mosaic MANF expression in postnatal pancreata and a significant correlation between the number of MANF-positive b-cells and b-cell mass in individual mice. In vitro, recombinant MANF induced b-cell proliferation in islets from aged mice and protected from hyperglycemia-induced endoplasmic reticulum (ER) stress. Consequently, excision of MANF from b-cells of adult MIP-1CreERT::Manffl/fl mice resulted in reduced b-cell mass and diabetes caused largely by b-cell ER stress and apoptosis, possibly accompanied by b-cell dedifferentiation and reduced rates of b-cell proliferation. Thus, MANF expression in adult mouse b-cells is needed for their maintenance in vivo. We also revealed a mechanistic link between ER stress and inflammatory signaling pathways leading to b-cell death in the absence of MANF. Hence, MANF might be a potential target for regenerative therapy in diabetes.