T. improves ␤-cell mass and glucose disposal in streptozotocin-induced diabetic mice and activates cAMP/PKA/␤-catenin signaling in ␤-cells in vitro. Am J Physiol Endocrinol Metab 304: E1263-E1272, 2013. First published April 9, 2013 doi:10.1152/ajpendo.00600.2012.-Recent studies have demonstrated that the COOH-terminal fragment of the incretin hormone glucagonlike peptide-1 (GLP-1), a nonapeptide GLP-1(28 -36)amide, attenuates diabetes and hepatic steatosis in diet-induced obese mice. However, the effect of this nonapeptide in pancreatic ␤-cells remains largely unknown. Here, we show that in a streptozotocin-induced mouse diabetes model, GLP-1(28 -36)amide improved glucose disposal and increased pancreatic ␤-cell mass and ␤-cell proliferation. An in vitro investigation revealed that GLP-1(28 -36)amide stimulates ␤-catenin (␤-cat) Ser 675 phosphorylation in both the clonal INS-1 cell line and rat primary pancreatic islet cells. In INS-1 cells, the stimulation was accompanied by increased nuclear ␤-cat content. GLP-1(28 -36)amide was also shown to increase cellular cAMP levels, PKA enzymatic activity, and cAMP response element-binding protein (CREB) and cyclic AMP-dependent transcription factor-1 (ATF-1) phosphorylation. Furthermore, GLP-1(28 -36)amide treatment enhanced islet insulin secretion and increased the growth of INS-1 cells, which was associated with increased cyclin D1 expression. Finally, PKA inhibition attenuated the effect of GLP-1(28 -36)amide on ␤-cat Ser 675 phosphorylation and cyclin D1 expression in the INS-1 cell line. We have thus revealed the beneficial effect of GLP-1(28 -36)amide in pancreatic ␤-cells in vitro and in vivo. Our observations suggest that GLP-1(28 -36)amide may exert its effect through the PKA/␤-catenin signaling pathway.glucagon-like peptide-1; protein kinase A; Wnt; cAMP response element-binding protein; insulin; bromodeoxyuridine THE PROGLUCAGON GENE encodes both the pancreatic hormone glucagon and the gut incretin hormone glucagon-like peptide-1 (GLP-1) (15,17). The exploration of mechanisms underlying the function of GLP-1 and another incretin hormone, gastric inhibitory polypeptide (GIP), has led to the development of two categories of novel therapeutic agents, namely GLP-1 analogs and DPP-IV inhibitors, for diabetes and potentially its complications (11,12). In addition to targeting pancreatic ␤-cells, GLP-1 also exerts its function in many other organs or tissues (1,4,7,40). The GLP-1 receptor (GLP-1R)-deficient mouse line has been utilized as a powerful tool in studying the function of GLP-1 not only in pancreatic ␤-cells but also in a number of organs that are importantly involved in glucose disposal and metabolic homeostasis (7). However, studies with this mouse model, along with investigations with other tools, suggested that certain functions of GLP-1 may not be mediated by its canonical receptor GLP-1R, whereas a previously assumed inactive form of GLP-1, namely GLP-1(9 -36)amide, has the therapeutic potential in certain cardiovascular disorders (2, 25).Both G...

Natural organic structures form via a growth mode in which nutrients are absorbed, transported, and integrated. In contrast, synthetic architectures are constructed through fundamentally different methods, such as assembling, molding, cutting, and printing. Here, we report a photoinduced strategy for regulating the localized growth of microstructures from the surface of a swollen dynamic substrate, by coupling photolysis, photopolymerization, and transesterification together. Photolysis is used to generate dissociable ionic groups to enhance the swelling ability that drives nutrient solutions containing polymerizable components into the irradiated region, photopolymerization converts polymerizable components into polymers, and transesterification incorporates newly formed polymers into the original network structure. Such light-regulated growth is spatially controllable and dose-dependent and allows fine modulation of the size, composition, and mechanical properties of the grown structures. We also demonstrate the application of this process in the preparation of microstructures on a surface and the restoration of large-scale surface damage.

The virtual synchronous generator (VSG) was proposed to emulate a synchronous machine's dynamics when integrating power electronic converter-based distributed energy resources to the power grid. However, the VSG's synchronization stability during grid faults is not fully explored. The underlying mechanism of loss of synchronization (LOS) still needs to be further revealed due to VSG's nonlinear characteristics. In this paper, a step-by-step analytical method based on combining the linear and nonlinear models is proposed to analyze VSG's dynamic behaviors during a large disturbance. The relationship between the linear and nonlinear models is first brought to light, showing that the linear model is suitable for qualitative analysis to give an intuitive physical insight. Simultaneously, the latter is adopted for quantitative analysis to assess stability after a grid fault. Moreover, to avoid the conflict of the synchronization stability and the inertia response, a transient damping method is added in the active power control loop, which can simultaneously improve the synchronization stability and frequency stability. Design guidelines are also proposed to identify the parameter of the transient damping with different inertia requirements. Finally, the experimental results verify the analytical method and the theoretical analysis.

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. Pancreatic islet-specific overexpression of Reg3␤ protein induced the expression of pro-islet genes and protected the mice against streptozotocin-induced diabetes mellitus. Am J Physiol Endocrinol Metab 300: E669 -E680, 2011. First published January 18, 2011; doi:10.1152/ajpendo.00600.2010.-Reg family proteins have been implicated in islet ␤-cell proliferation, survival, and regeneration. The expression of Reg3␤ (pancreatitis-associated protein) is highly induced in experimental diabetes and acute pancreatitis, but its precise role has not been established. Through knockout studies, this protein was shown to be mitogenic, antiapoptotic, and anti-inflammatory in the liver and pancreatic acinars. To test whether it can promote islet cell growth or survival against experimental damage, we developed ␤-cell-specific overexpression using rat insulin I promoter, evaluated the changes in normal islet function, gene expression profile, and the response to streptozotocin-induced diabetes. Significant and specific overexpression of Reg3␤ was achieved in the pancreatic islets of RIP-I/Reg3␤ mice, which exhibited normal islet histology, ␤-cell mass, and in vivo and in vitro insulin secretion in response to high glucose yet were slightly hyperglycemic and low in islet GLUT2 level. Upon streptozotocin treatment, in contrast to wild-type littermates that became hyperglycemic in 3 days and lost 15% of their weight, RIP-I/Reg3␤ mice were significantly protected from hyperglycemia and weight loss. To identify specific targets affected by Reg3␤ overexpression, a whole genome DNA microarray on islet RNA isolated from the transgenic mice revealed more than 45 genes significantly either up-or downregulated. Among them, isletprotective osteopontin/SPP1 and acute responsive nuclear protein p8/NUPR1 were significantly induced, a result further confirmed by real-time PCR, Western blots, and immunohistochemistry. Our results suggest that Reg3␤ is unlikely an islet growth factor but a putative protector that prevents streptozotocin-induced damage by inducing the expression of specific genes.pancreatitis-associated protein; DNA microarray; real-time polymerase chain reaction; Western blot; immunofluorescence; Reg family proteins; transgenic mice A NORMAL ␤-CELL MASS is a crucial element against the development of diabetes mellitus and is determined by at least four independent parameters, i.e., mitogenic replication, cell size expansion, neogenesis (from other pancreatic cells), and apoptosis (42). The net rate of ␤-cell growth is the balance among the rates of ␤-cell replication, hypertrophy, neogenesis, and apoptosis (10). Various growth factors such as hepatocyte growth factor and glucagon-like peptide-1 (GLP-1) have been reported to stimulate islet cell expansion (12, 13, 43). For a therapeutic purpose, ␤-cell mass could also be supplemented by islet cell transplantation where growth factors were shown to promote the survival and/or expansion of transplanted cells in rodents (8,43). Unfortunately, very few of these factors have been pr...

The development of lipid nanoparticle (LNP) formulations for targeting the bone microenvironment holds significant potential for nucleic acid therapeutic applications including bone regeneration, cancer, and hematopoietic stem cell therapies. However, therapeutic delivery to bone remains a significant challenge due to several biological barriers, such as low blood flow in bone, blood–bone marrow barriers, and low affinity between drugs and bone minerals, which leads to unfavorable therapeutic dosages in the bone microenvironment. Here, we construct a series of bisphosphonate (BP) lipid-like materials possessing a high affinity for bone minerals, as a means to overcome biological barriers to deliver mRNA therapeutics efficiently to the bone microenvironment in vivo. Following in vitro screening of BP lipid-like materials formulated into LNPs, we identified a lead BP-LNP formulation, 490BP-C14, with enhanced mRNA expression and localization in the bone microenvironment of mice in vivo compared to 490-C14 LNPs in the absence of BPs. Moreover, BP-LNPs enhanced mRNA delivery and secretion of therapeutic bone morphogenetic protein-2 from the bone microenvironment upon intravenous administration. These results demonstrate the potential of BP-LNPs for delivery to the bone microenvironment, which could potentially be utilized for a range of mRNA therapeutic applications including regenerative medicine, protein replacement, and gene editing therapies.

ObjectiveDisruption of TCF7L2 in mouse pancreatic β-cells has generated different outcomes in several investigations. Here we aim to clarify role of β-cell TCF7L2 and Wnt signaling using a functional-knockdown approach.MethodsAdenovirus-mediated dominant negative TCF7L2 (TCF7L2DN) expression was conducted in Ins-1 cells. The fusion gene in which TCF7L2DN expression is driven by PTRE3G was utilized to generate the transgenic mouse line TCF7L2DNTet. The double transgenic line was created by mating TCF7L2DNTet with Ins2-rtTA, designated as βTCFDN. β-cell specific TCF7L2DN expression was induced in βTCFDN by doxycycline feeding.ResultsTCF7L2DN expression in Ins-1 cells reduced GSIS, cell proliferation and expression of a battery of genes including incretin receptors and β-cell transcription factors. Inducing TCF7L2DN expression in βTCFDN during adulthood or immediately after weaning generated no or very modest metabolic defect, while its expression during embryonic development by doxycycline feeding in pregnant mothers resulted in significant glucose intolerance associated with altered β-cell gene expression and reduced β-cell mass.ConclusionsOur observations support a cell autonomous role for TCF7L2 in pancreatic β-cells suggested by most, though not all, investigations. βTCFDN is a novel model for further exploring the role of TCF7L2 in β-cell genesis and metabolic homeostasis.

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