Herein we present a method allowing an accurate analysis of islet cell viability in real time which can be applied to cells and tissues in vitro as well as in vivo. For this purpose we combined the addition of live stains with live confocal microscopy. Several fluorescent dyes such as, wheat germ agglutinin (WGA), tetramethylrhodamine methyl ester perchlorate (TMRM) and Rhod-2, were used to assess cell morphology (WGA), mitochondrial activity (TMRM) or intracellular calcium content (Rhod-2). Microscopy was performed with a microlens-enhanced Nipkow disk-based system which allows live confocal data acquisition. A precise and fast assessment of islet cell viability is achievable using the combination of such a live confocal imaging system with the above mentioned fluorescent dyes. The fast data acquisition and the high precision allowing even single organelle visualization in living cells fulfills the requirements for a fast and efficient monitoring of cell quality under different situations in vitro as well as in vivo. The result is a new method which is fast, accurate and versatile making it an ideal tool to study islet cell biology under different conditions such as after their isolation, transport, transplantation or their culture. Although insights into all these different conditions of islet cell biology are possible, and in spite of “having seen a lot” we still are learning and did not win the battle in the field of islet transplantation. However, considering the amount of other live stains available, this method can be extended and adapted to assess other vital parameters such as the generation of oxygen radicals. Therefore, we are convinced that real time live confocal imaging will be one of the key methods for a better understanding of islet cell biology, especially in the whole context of islet transplantation.

The incretin hormone glucagon-like peptide-1 is encoded by the proglucagon gene (gcg) and produced in both the gut and brainstem. While peripheral GLP-1 stimulates pancreatic beta cell proliferation and insulin secretion, brain GLP-1 controls energy homeostasis with a yet-to-be further defined mechanism. Extensive previous investigations have shown that cAMP signaling is important in the transcription of gcg and the secretion of GLP-1. Recent studies in different disciplines have deepened our understanding on the role of cAMP signaling and its crosstalk with other signaling cascades in endocrine and other cell lineages. Here we summarize recent advances from our own laboratory and elsewhere in the following three areas. A) In the gut, cAMP signaling is able to crosstalk with the Wnt signaling pathway in stimulating the production of the incretin hormones. B) In pancreatic beta cells, cAMP signaling mediates the effect of GLP-1 via cross-talking with a major Wnt signaling effector beta-catenin in stimulating beta cell proliferation. In addition, both protein kinase A (PKA) and Exchange Protein Activated by cAMP (Eapc) are involved in the degradation of TxNIP, a mediator of glucotoxicity. C) The T2D risk gene TCF7L2, which encodes another major effector of the Wnt signaling, is expressed in the brainstem gcg-expressing cells, and its functional knockdown leads to altered glucose homeostasis.