Connor et al. show that transcriptomic profiling of DCs exposed to two different Th2 stimuli in vivo reveals large numbers of differentially expressed genes but few similarities between conditions.

The processes regulating glucose-stimulated insulin secretion (GSIS) and its modulation by incretins in pancreatic β-cells are only partly understood. Here we investigate the involvement of β-catenin in these processes. Reducing β-catenin levels using siRNA knockdown attenuated GSIS in a range of β-cell models and blocked the ability of GLP-1 agonists and the depolarizing agent KCl to potentiate this. This could be mimicked in both β-cell models and isolated islets by short-term exposure to the β-catenin inhibitory drug pyrvinium. In addition, short-term treatment with a drug that increases β-catenin levels results in an increase in insulin secretion. The timing of these effects suggests that β-catenin is required for the processes regulating trafficking and/or release of pre-existing insulin granules rather than for those regulated by gene expression. This was supported by the finding that the overexpression of the transcriptional co-activator of β-catenin, transcription factor 7-like 2 (TCF7L2), attenuated insulin secretion, consistent with the extra TCF7L2 translocating β-catenin from the plasma membrane pool to the nucleus. We show that β-catenin depletion disrupts the intracellular actin cytoskeleton, and by using total internal reflectance fluorescence (TIRF) microscopy, we found that β-catenin is required for the glucose- and incretin-induced depletion of insulin vesicles from near the plasma membrane. In conclusion, we find that β-catenin levels modulate Ca-dependent insulin exocytosis under conditions of glucose, GLP-1, or KCl stimulation through a role in modulating insulin secretory vesicle localization and/or fusion via actin remodeling. These findings also provide insights as to how the overexpression of TCF7L2 may attenuate insulin secretion.

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Pancreatic β-cells are highly responsive to changes in glucose, but the mechanisms involved are only partially understood. There is increasing evidence that the β-catenin signalling pathway plays an important role in regulating β-cell function, but the mechanisms regulating β-catenin signalling in these cells is not well understood. In the present study we show that β-catenin levels and downstream signalling are regulated by changes in glucose levels in INS-1E and β-TC6-F7 β-cell models. We found a glucose-dependent increase in levels of β-catenin in the cytoplasm and nucleus of INS-1E cells. Expression of cyclin D1 also increased with glucose and required the presence of β-catenin. This was associated with an increase in phosphorylation of β-catenin on Ser552, which is known to stabilize the molecule and increase its transcriptional activity. In a search for possible signalling intermediates we found forskolin and cell-permeable cAMP analogues recapitulated the glucose effects, suggesting a role for cAMP and PKA (cAMP-dependent protein kinase/protein kinase A) downstream of glucose. Furthermore, glucose caused sustained increases in cAMP. Two different inhibitors of adenylate cyclase and PKA signalling blocked the effects of glucose, whereas siRNA (small interfering RNA) knockdown of PKA blocked the effects of glucose on β-catenin signalling. Finally, reducing β-catenin levels with either siRNA or pyrvinium impaired glucose- and KCl-stimulated insulin secretion. Taken together the results of the present study define a pathway by which changes in glucose levels can regulate β-catenin using a mechanism which involves cAMP production and the activation of PKA. This identifies a pathway that may be important in glucose-dependent regulation of gene expression and insulin secretion in β-cells.

Aims/hypothesis Due to their ability to regulate various signalling pathways (cytokines, hormones, growth factors), the suppressor of cytokine signalling (SOCS) proteins are thought to be promising therapeutic targets for metabolic and inflammatory disorders. Hence, their role in vivo has to be precisely determined. Methods We generated transgenic mice constitutively producing SOCS-3 in skeletal muscle to define whether the sole abundance of SOCS-3 is sufficient to induce metabolic disorders and whether SOCS-3 is implicated in physiological roles distinct from metabolism. Results We demonstrate here that chronic expression of SOCS-3 in skeletal muscle leads to overweight in mice and worsening of high-fat diet-induced systemic insulin resistance. Counter-intuitively, insulin sensitivity in muscle of transgenic mice appears to be unaltered. However, following constitutive SOCS-3 production, several genes had deregu-P. Lebrun and E. Cognard contributed equally to this work. Electronic supplementary materialThe online version of this article

Aims/hypothesis Suppressor of cytokine signalling (SOCS) proteins are powerful inhibitors of pathways involved in survival and function of pancreatic beta cells. Whereas SOCS1 and SOCS3 have been involved in immune and inflammatory processes, respectively, in beta cells, nothing is known about SOCS2 implication in the pancreas. Methods Transgenic (tg) mice were generated that constitutively produced SOCS2 in beta cells (βSOCS2) to define whether this protein is implicated in beta cell functioning and/or survival.Results Constitutive production of SOCS2 in beta cells leads to hyperglycaemia and glucose intolerance. This phenotype is not a consequence of decreased beta cell mass or inhibition of insulin synthesis. However, insulin secretion to various secretagogues is profoundly altered in intact animals and isolated islets. Interestingly, constitutive SOCS2 production dampens the rise in cytosolic free calcium concentration induced by glucose, while glucose metabolism is unchanged. Moreover, tg islets have a depletion in endoplasmic reticulum Ca 2+ stores, suggesting that SOCS2 interferes with calcium fluxes. Finally, inElectronic supplementary material The online version of this article

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In the last 20 years the prevalence of metabolic disorders, in particular type 2 diabetes (T2D), has more than doubled. Recently, a strong link between T2D and cancer, in particularly liver cancer has been reported. However, the mechanism connecting the development of type 2 diabetes and cancer remains unknown. One of the biggest drivers of liver cancer is alterations in the Wnt/β-catenin pathway. In this study, we aimed to identify the effect of glucagon on β-catenin in the isolated rat liver. We found glucagon, which is substantially raised in patients with T2D, rapidly phosphorylates β-catenin on serine 552 that is associated with increased expression of genes cyclin D1 (CCND1) and c-Myc (MYC), which are known to be involved in liver cancer. This finding may explain the increased risk of liver cancer in people with T2D.