Aims/hypothesis Morphological changes that occur during pancreatic endocrine cell differentiation have been shown in rodent systems to be dependent on sequential alterations in transcription factor expression. However, similar data for humans have been limited. The aim of the present study was to provide a connection between pancreatic morphology, transcription factor gene expression and protein localisation during human fetal development. Methods Human fetal pancreases were examined at early (8-12 weeks of fetal age), middle (14-16 weeks) and late (19-21 weeks) stages, using immunohistological, microarray and qRT-PCR analyses. Results We observed a significant decrease in pancreatic duodenal homeobox 1 (PDX-1) + /cytokeratin 19 + cells (p<0.001), with a simultaneous increase in PDX-1 + /insulin + cells from 8 to 21 weeks (p<0.05). Increased PDX-1/ insulin co-localisation within islet clusters was noted, while no co-expression of PDX-1 with glucagon was found, suggesting that loss of PDX-1 is essential for alpha cell formation. Given that neurogenin 3 (NGN3) expression is critical for establishing the endocrine cell programme in the rodent pancreas, we examined its expression pattern and colocalisation in PDX-1 + , insulin + and glucagon + cells. Colocalisation of NGN3 with PDX-1, insulin and glucagon was noted during early development, with significant decreases in middle and late stages (p<0.001). Our microarray and co-localisation analyses of transcription factors linked to NGN3 demonstrated that ISL1 transcription factor (ISL1), neurogenic differentiation 1 (NEUROD1), NK2 related transcription factor related, locus 2 (NKX2-2) and paired box gene 6 (PAX6) were upregulated during development and present in all four endocrine cell types, while NK6 related transcription factor related, locus 1 (NKX6-1) was expressed exclusively in beta cells. Conclusions/interpretation This study is an important step towards identifying key molecular factors involved in development of the human fetal endocrine pancreas.

The functional impact of adiponectin on pancreatic beta cells is so far poorly understood. Although adiponectin receptors (AdipoR1/2) were identified, their involvement in adiponectininduced signaling and other molecules involved is not clearly defined. Therefore, we investigated the role of adiponectin in beta cells and the signaling mediators involved. MIN6 beta cells and mouse islets were stimulated with globular (2.5 g/ml) or full-length (5 g/ml) adiponectin under serum starvation, and cell viability, proliferation, apoptosis, insulin gene expression, and secretion were measured. Lysates were subjected to Western blot analysis to determine phosphorylation of AMP-activated protein kinase (AMPK), Akt, or ERK. Functional significance of signaling was confirmed using dominant negative mutants or pharmacological inhibitors. Participation of AdipoRs was assessed by overexpression or siRNA. Adiponectin failed to activate AMPK after 10 min or 1-and 24-h stimulation. ERK was significantly phosphorylated after 24-h treatment with adiponectin, whereas Akt was activated at all time points examined. 24-h stimulation with adiponectin significantly increased cell viability by decreasing cellular apoptosis, and this was prevented by dominant negative Akt, wortmannin (PI3K inhibitor), and U0126 (MEK inhibitor). Moreover, adiponectin regulated insulin gene expression and glucose-stimulated insulin secretion, which was also prevented by wortmannin and U0126 treatment. Interestingly, the data also suggest adiponectin-induced changes in Akt and ERK phosphorylation and caspase-3 may occur independent of the level of AdipoR expression. This study demonstrates a lack of AMPK involvement and implicates Akt and ERK in adiponectin signaling, leading to protection against apoptosis and stimulation of insulin gene expression and secretion in pancreatic beta cells.Type 2 diabetes is characterized by both a loss of insulin sensitivity and beta cell dysfunction in the pancreas. Adiponectin is an adipocyte-derived hormone that shows a strong negative correlation with insulin resistance and obesity (1, 2). Studies show that whereas adiponectin knock-out mice develop insulin resistance and glucose intolerance when challenged with a high fat diet, adiponectin-overexpressing mice are highly insulin-sensitive and are resistant to diet-induced diabetes (3-6). Adiponectin is reported to stimulate fatty acid oxidation and glucose uptake and reduce gluconeogenesis in myocytes and hepatocytes, thus increasing peripheral insulin sensitivity (7). Reduced adiponectin levels are also correlated with reduced vascular function and an increase in coronary artery disease (8).Adiponectin forms trimers or higher order complexes including hexamers and oligomers (9). These higher order complexes of full-length adiponectin (fAd) 4 are the primary circulating forms, and localized proteolytic cleavage of fAd has been shown to produce globular adiponectin (gAd) (10). Two proposed homologous adiponectin receptors (AdipoR1 and AdipoR2) were cloned and shown to be wi...

c-Kit tyrosine receptor kinase, a well-established stem cell marker, is expressed in a variety of tissues including the pancreas. The involvement of c-Kit in fetal rat and human endocrine pancreatic development, survival, and function has been well characterized but primarily using in vitro experimental approaches. Therefore, the aim of the current study was to examine whether deficiency of a functional c-Kit receptor would have physiological and functional implications in vivo. We characterized the c-Kit mutant mouse, c-Kit(W-v/+), to evaluate the in vivo role of c-Kit in beta-cell growth and function. Here we report that male c-Kit(W-v/+) mice, at 8 wk of age, showed high fasting blood glucose levels and impaired glucose tolerance, which was associated with low levels of insulin secretion after glucose stimulation in vivo and in isolated islets. Morphometric analysis revealed that beta-cell mass was significantly reduced (50%) in male c-Kit(W-v/+) mice when compared with controls (c-Kit(+/+)) (P < 0.05). In parallel, a reduction in pancreatic duodenal homeobox-1 and insulin gene expression in whole pancreas as well as isolated islets of c-Kit(W-v/+) male mice was noted along with a decrease in pancreatic insulin content. Furthermore, the reduction in beta-cell mass in male c-Kit(W-v/+) mice was associated with a decrease in beta-cell proliferation. Interestingly, these changes were not observed in female c-Kit(W-v/+) mice until 40 wk of age. Our results clearly demonstrate that the c-Kit receptor is involved in the regulation of glucose metabolism, likely through an important role in beta-cell development and function.