Lactogens Reduce Endoplasmic Reticulum Stress-Induced Rodent and Human ß-Cell Death and Diabetes Incidence in Akita Mice.

ABSTRACT

Diabetes occurs due to a loss of functional ß-cells, resulting from ß-cell death and dysfunction. Lactogens protect rodent and human ß-cells in vitro and in vivo against triggers of ß-cell cytotoxicity relevant to diabetes, many of which converge onto a common pathway of endoplasmic reticulum (ER) stress. However, whether lactogens modulate the ER stress pathway is unknown. This study examines whether lactogens can protect ß-cells against ER stress and mitigate diabetes incidence in Akita (Ak) mice, a rodent model of ER stress-induced diabetes, akin to neonatal diabetes in humans. We show that lactogens protect INS-1 cells, primary rodent and human ß-cells in vitro against two distinct ER stressors, tunicamycin and thapsigargin, through activation of the JAK2/STAT5 pathway. Lactogens mitigate expression of proapoptotic molecules in the ER stress pathway that are induced by chronic ER stress in INS-1 cells and rodent islets. Transgenic expression of placental lactogen in ß-cells of Ak mice drastically reduces the severe hyperglycemia, diabetes incidence, hypoinsulinemia, ß-cell death, and loss of ß-cell mass observed in Ak littermates. These are the first studies in any cell type demonstrating that lactogens modulate the ER stress pathway, causing enhanced ß-cell survival and reduced diabetes incidence in the face of chronic ER stress.