Regulation of β-cell mass by hormones and growth factors

Abstract

Substantial new information has accumulated on molecular mechanisms of pancreas development, regulation of β-cell gene expression, and the role of growth factors in the differentiation, growth, and regeneration of β-cells. The present review focuses on some recent studies on the mechanism of action of cytokines such as growth hormone (GH) and prolactin (PRL) in β-cell proliferation and gene expression - in particular, the role of signal transducers and activators of transcription (STAT) proteins. The implication of the discovery of suppressors of cytokine signaling (SOCS) proteins for the interaction between stimulatory and inhibitory cytokines, including GH, PRL, leptin, and the proinflammatory cytokines interleukin-1 and interferon-γ, in β-cell survival is not yet clear. Recent studies indicate a role of cell adhesion molecules and the delta-like protein preadipocyte factor 1/fetal antigen 1 (Pref-1/FA-1) in cytokine-induced β-cell growth and development. Surprisingly, glucagon-like peptide-1 (GLP-1) was recently found to stimulate not only insulin secretion but also β-cell replication and differentiation, which may present a new perspective in treatment of type 2 diabetes. Together with the intriguing reports on positive effects of insulin on both β-cell growth and function, a picture is emerging of an integrated network of signaling events acting in concert to control β-cell mass adaptation to insulin demand.