TGFβ receptor signaling is essential for inflammation-induced but not β-cell workload-induced β-cell proliferation

Scaling Insulin-Producing Cells by Multiple Strategies

In the quest to combat insulin-dependent diabetes mellitus (IDDM), allogenic pancreatic islet cell therapy sourced from deceased donors represents a significant therapeutic advance. However, the applicability of this approach is hampered by donor scarcity and the demand for sustained immunosuppression. Human induced pluripotent stem cells are a game-changing resource for generating synthetic functional insulin-producing β cells. In addition, novel methodologies allow the direct expansion of pancreatic progenitors and mature β cells, thereby circumventing prolonged differentiation. Nevertheless, achieving practical reproducibility and scalability presents a substantial challenge for this technology. As these innovative approaches become more prominent, it is crucial to thoroughly evaluate existing expansion techniques with an emphasis on their optimization and scalability. This manuscript delineates these cutting-edge advancements, offers a critical analysis of the prevailing strategies, and underscores pivotal challenges, including cost-efficiency and logistical issues. Our insights provide a roadmap, elucidating both the promises and the imperatives in harnessing the potential of these cellular therapies for IDDM.

Regeneration of Pancreatic Beta Cells by Modulation of Molecular Targets Using Plant-Derived Compounds: Pharmacological Mechanisms and Clinical Potential

Type 2 diabetes (T2D) is characterized by pancreatic beta-cell dysfunction, increased cell death and loss of beta-cell mass despite chronic treatment. Consequently, there has been growing interest in developing beta cell-centered therapies. Beta-cell regeneration is mediated by augmented beta-cell proliferation, transdifferentiation of other islet cell types to functional beta-like cells or the reprograming of beta-cell progenitors into fully differentiated beta cells. This mediation is orchestrated by beta-cell differentiation transcription factors and the regulation of the cell cycle machinery. This review investigates the beta-cell regenerative potential of antidiabetic plant extracts and phytochemicals. Various preclinical studies, including in vitro, in vivo and ex vivo studies, are highlighted. Further, the potential regenerative mechanisms and the intra and extracellular mediators that are of significance are discussed. Also, the potential of phytochemicals to translate into regenerative therapies for T2D patients is highlighted, and some suggestions regarding future perspectives are made.

Bone-marrow derived cells do not contribute to new beta-cells in the inflamed pancreas

The contribution of bone-marrow derived cells (BMCs) to a newly formed beta-cell population in adults is controversial. Previous studies have only used models of bone marrow transplantation from sex-mismatched donors (or other models of genetic labeling) into recipient animals that had undergone irradiation. This approach suffers from the significant shortcoming of the off-target effects of irradiation. Partial pancreatic duct ligation (PDL) is a mouse model of acute pancreatitis with a modest increase in beta-cell number. However, the possibility that recruited BMCs in the inflamed pancreas may convert into beta-cells has not been examined. Here, we used an irradiation-free model to track the fate of the BMCs from the donor mice. A ROSA-mTmG red fluorescent mouse was surgically joined to an INS1^Cre knock-in mouse by parabiosis to establish a mixed circulation. PDL was then performed in the INS1^Cre mice 2 weeks after parabiosis, which was one week after establishment of the stable blood chimera. The contribution of red cells from ROSA-mTmG mice to beta-cells in INS1^Cre mouse was evaluated based on red fluorescence, while cell fusion was evaluated by the presence of green fluorescence in beta-cells. We did not detect any red or green insulin+ cells in the INS1^Cre mice, suggesting that there was no contribution of BMCs to the newly formed beta-cells, either by direct differentiation, or by cell fusion. Thus, the contribution of BMCs to beta-cells in the inflamed pancreas should be minimal, if any.

Bioengineered Pancreas-Liver Crosstalk in a Microfluidic Coculture Chip Identifies Human Metabolic Response Signatures in Prediabetic Hyperglycemia

Aberrant glucose homeostasis is the most common metabolic disturbance affecting one in ten adults worldwide. Prediabetic hyperglycemia due to dysfunctional interactions between different human tissues, including pancreas and liver, constitutes the largest risk factor for the development of type 2 diabetes. However, this early stage of metabolic disease has received relatively little attention. Microphysiological tissue models that emulate tissue crosstalk offer emerging opportunities to study metabolic interactions. Here, a novel modular multitissue organ-on-a-chip device is presented that allows for integrated and reciprocal communication between different 3D primary human tissue cultures. Precisely controlled heterologous perfusion of each tissue chamber is achieved through a microfluidic single "synthetic heart" pneumatic actuation unit connected to multiple tissue chambers via specific configuration of microchannel resistances. On-chip coculture experiments of organotypic primary human liver spheroids and intact primary human islets demonstrate insulin secretion and hepatic insulin response dynamics at physiological timescales upon glucose challenge. Integration of transcriptomic analyses with promoter motif activity data of 503 transcription factors reveals tissue-specific interacting molecular networks that underlie β-cell stress in prediabetic hyperglycemia. Interestingly, liver and islet cultures show surprising counter-regulation of transcriptional programs, emphasizing the power of microphysiological coculture to elucidate the systems biology of metabolic crosstalk.

Therapeutic Strategies Targeting Pancreatic Islet β-Cell Proliferation, Regeneration, and Replacement

Diabetes results from insufficient insulin production by pancreatic islet β-cells or a loss of β-cells themselves. Restoration of regulated insulin production is a predominant goal of translational diabetes research. Here, we provide a brief overview of recent advances in the fields of β-cell proliferation, regeneration, and replacement. The discovery of therapeutic targets and associated small molecules has been enabled by improved understanding of β-cell development and cell cycle regulation, as well as advanced high-throughput screening methodologies. Important findings in β-cell transdifferentiation, neogenesis, and stem cell differentiation have nucleated multiple promising therapeutic strategies. In particular, clinical trials are underway using in vitro-generated β-like cells from human pluripotent stem cells. Significant challenges remain for each of these strategies, but continued support for efforts in these research areas will be critical for the generation of distinct diabetes therapies.

Polarized macrophages promote gestational beta cell growth through extracellular signal-regulated kinase 5 signalling

AIM

To show that depletion of pancreatic macrophages impairs gestational beta cell proliferation and leads to glucose intolerance.

MATERIALS AND METHODS

Genetic animal models were applied to study the effects of depletion of pancreatic macrophges on gestational beta-cell proliferaiton and glucose response. The crosstalk between macrophages and beta-cells was studied in vivo using beta-cell-specific extracellular-signal-regulated kinase 5 (ERK5) knockout and epidermal growth receptor (EGFR) knockout mice, and in vitro using a co-culture system.

RESULTS

Beta cell-derived placental growth factor (PlGF) recruited naïve macrophages and polarized them towards an M2-like phenotype. These macrophages then secreted epidermal growth factor (EGF), which activated extracellular signal-regulated kinase 5 (ERK5) signalling in beta cells to promote gestational beta cell proliferation. On the other hand, activation of ERK5 signalling in beta cells likely, in turn, enhanced the production and secretion of PlGF by beta cells.

CONCLUSIONS

Our study shows a regulatory loop between macrophages and beta cells through PlGF/EGF/ERK5 signalling cascades to regulate gestational beta cell growth.

The roles of cell-cell and organ-organ crosstalk in the type 2 diabetes mellitus associated inflammatory microenvironment

Type 2 diabetes mellitus (T2DM) is a classic metaflammatory disease, and the inflammatory states of the pancreatic islet and insulin target organs have been well confirmed. However, abundant evidence demonstrates that there are countless connections between these organs in the presence of a low degree of inflammation. In this review, we focus on cell-cell crosstalk among local cells in the islet and organ-organ crosstalk among insulin-related organs. In contrast to that in acute inflammation, macrophages are the dominant immune cells causing inflammation in the islets and insulin target organs in T2DM. In the inflammatory microenvironment (IME) of the islet, cell-cell crosstalk involving local macrophage polarization and proinflammatory cytokine production impair insulin secretion by β-cells. Furthermore, organ-organ crosstalk, including the gut-brain-pancreas axis and interactions among insulin-related organs during inflammation, reduces insulin sensitivity and induces endocrine dysfunction. Therefore, this crosstalk ultimately results in a cascade leading to β-cell dysfunction. These findings could have broad implications for therapies aimed at treating T2DM.

Accelerated Generation of Extra-Islet Insulin-Producing Cells in Diabetic Rats, Treated with Sodium Phthalhydrazide

β-cells dysfunction plays an important role in the pathogenesis of type 2 diabetes (T2D), partially may be compensated by the generation of extra-islet insulin-producing cells (IPCs) in pancreatic acini and ducts. Pdx1 expression and inflammatory level are suggested to be involved in the generation of extra-islet IPCs, but the exact reasons and mechanisms of it are unclear. Macrophages are key inflammatory mediators in T2D. We studied changes in mass and characteristics of extra-islet IPCs in rats with a streptozotocin-nicotinamide model of T2D and after i.m. administration of 20 daily doses of 2 mg/kg b.w. sodium aminophthalhydrazide (APH). Previously, we found that APH modulates macrophage production and increases the proliferative activity of pancreatic β-cells. Expressions of insulin and Pdx1, as well as F4/80 (macrophage marker), were detected at the protein level by immunohistochemistry analysis, the concentration of pro- and anti-inflammatory cytokines in blood and pancreas—by ELISA. Diabetic rats treated with APH showed an increasing mass of extra-islet IPCs and the content of insulin in them. The presence of Pdx1⁺ cells in the exocrine pancreas also increased. F4/80⁺ cell reduction was accompanied by increasing TGF-β1 content. Interestingly, during the development of diabetes, the mass of β-cells decreased faster than the mass of extra-islet IPCs, and extra-islet IPCs reacted to experimental T2D differently depending on their acinar or ductal location.

Role of angiogenesis in beta-cell epithelial-mesenchymal transition in chronic pancreatitis-induced diabetes

Clinical evidence suggests that patients with chronic pancreatitis (CP) are prone to development of diabetes (chronic pancreatitis-related diabetes; CPRD), whereas the underlying mechanisms are not fully determined. Recently, we showed that the gradual loss of functional beta-cells in a mouse model for CPRD, partial pancreatic duct ligation (PDL), results from a transforming growth factor β1 (TGFβ1)-triggered beta-cell epithelial-mesenchymal transition (EMT), rather than from apoptotic beta-cell death. Here, the role of angiogenesis in CPRD-associated beta-cell EMT was addressed. We detected enhanced angiogenesis in the inflamed pancreas from CP patients by bioinformatic analysis and from PDL-mice. Inhibition of angiogenesis by specific antisera for vascular endothelial growth factor receptor 2 (VEGFR2), DC101, did not alter the loss of beta-cells and the fibrotic process in PDL-pancreas. However, DC101-mediated inhibition of angiogenesis abolished pancreatitis-induced beta-cell EMT and rendered it to apoptotic beta-cell death. Thus, our data suggest that angiogenesis promotes beta-cell survival in the inflamed pancreas, while suppression of angiogenesis turns beta-cell EMT into apoptotic beta-cell death. This finding could be informative during development of intervention therapies for CPRD.

Role of TGF-Beta Signaling in Beta Cell Proliferation and Function in Diabetes

Beta (β) cell dysfunction or loss is the common pathological feature in all types of diabetes mellitus (diabetes). Resolving the underlying mechanism may facilitate the treatment of diabetes by preserving the β cell population and function. It is known that TGF-β signaling plays diverse roles in β cell development, function, proliferation, apoptosis, and dedifferentiation. Inhibition of TGF-β signaling expands β cell lineage in the development. However, deletion of Tgfbr1 has no influence on insulin demand-induced but abolishes inflammation-induced β cell proliferation. Among canonical TGF-β signaling, Smad3 but not Smad2 is the predominant repressor of β cell proliferation in response to systemic insulin demand. Deletion of Smad3 simultaneously improves β cell function, apoptosis, and systemic insulin resistance with the consequence of eliminated overt diabetes in diabetic mouse models, revealing Smad3 as a key mediator and ideal therapeutic target for type-2 diabetes. However, Smad7 shows controversial effects on β cell proliferation and glucose homeostasis in animal studies. On the other hand, overexpression of Tgfb1 prevents β cells from autoimmune destruction without influence on β cell function. All these findings reveal the diverse regulatory roles of TGF-β signaling in β cell biology.

Delivery of gefitinib in synergism with thymoquinone via transferrin-conjugated nanoparticle sensitizes gefitinib-resistant non-small cell lung carcinoma to control metastasis and stemness

Epidermal growth factor receptor (EGFR) normally over-expresses in non-small cell lung cancer (NSCLC) cells. Its mutations act as oncogenic drivers in the cellular signal transduction pathway, and induce the downstream activation of numerous key cellular events involved in cellular proliferation and survival. EGFR tyrosine kinase inhibitors (EGFR-TK inhibitors), such as gefitinib and erlotinib, have been used for a long time in the treatment of NSCLC. However, they fail to overcome the EGFR-TK mutation due to the acquisition of drug resistance. It is strongly believed that the epithelial-to-mesenchymal transition (EMT) is a key player for acquired resistance and consequent limitation of the clinical efficiency of EGFR-TKIs. Therefore, a new strategy needs to be developed to overcome the resistance in NSCLC. In this current study, we have disclosed for the first time the efficiency of transferrin-modified PLGA-thymoquinone-nanoparticles in combination with gefitinib (NP-dual-1, NP-dual-2 and NP-dual-3) towards gefitinib-resistant A549 cells. The gefitinib-resistant A549 cells (A549/GR) showed 12.3-fold more resistance to gefitinib in comparison to non-resistant A549 cells. The phenotypic alteration resembling spindle-cell shape and increased pseudopodia integuments featured the EMT phenomena in A549/GR cells. EMT in A549/GR was later coupled with the loss of Ecad and expansion of Ncad, along with upregulated vimentin expression, as compared to the control A549 cells. Moreover, the invasive nature and migration potential are more amplified in A549/GR cells. Pre-incubation of A549 cells with TGFβ1 also initiated EMT, leading to drug resistance. Conversely, treatment of A549 or A549/GR cells with NP-dual-3 effectively retrieved the sensitivity to gefitinib, restricted the EMT phenomenon, and impaired the TGFβ1-induced EMT. On unveiling the underlying mechanism of therapeutic action, we found that STAT3 and miR-21 were individually overexpressed in the A549/GR cells by transfection, and followed by treatment with NP-dual-3. Simultaneously, NP-dual-3 fragmented HIF1-α induced EMT in A549/GR cells and reduced the CSCs markers, viz., Oct-4, Sox-2, Nanog, and Aldh1. These data are self-sufficient to suggest that NP-dual-3 re-sensitizes the drug-resistant A549/GR cells to gefitinib, possibly by retrieving MET phenomena via modulation of STAT3/mir-21/Akt/PTEN/HIF1-α axis. Thus, TQ nanoparticles combined with TKI gefitinib may provide an effective platform to treat NSCLC.

PlGF Reduction Compromises Angiogenesis in Diabetic Foot Disease Through Macrophages

Diabetic foot disease (DFD) is a common and serious complication for diabetes and is characterized with impaired angiogenesis. In addition to the well-defined role of vascular endothelial growth factor (VEGF) -A and its defect in the pathogenesis of DFD, another VEGF family member, placental growth factor (PlGF), was also recently found to alter expression pattern in the DFD patients with undetermined mechanisms. This question was thus addressed in the current study. We detected attenuated PlGF upregulation in a mouse DFD model. In addition, the major cell types at the wound to express the unique PlGF receptor, VEGF receptor 1 (VEGFR1), were macrophages and endothelial cells. To assess how PlGF regulates DFD-associated angiogenesis, we injected recombinant PlGF and depleted VEGF1R specifically in macrophages by local injection of an adeno-associated virus (AAV) carrying siRNA for VEGFR1 under a macrophage-specific CD68 promoter. We found that the angiogenesis and recovery of the DFD were both improved by PlGF injection. The PlGF-induced improvement in angiogenesis and the recovery of skin injury were largely attenuated by macrophage-specific depletion of VEGF1R, likely resulting from reduced macrophage number and reduced M2 polarization. Together, our data suggest that reduced PlGF compromises angiogenesis in DFD at least partially through macrophages.

β-Cell pre-mir-21 induces dysfunction and loss of cellular identity by targeting transforming growth factor beta 2 (Tgfb2) and Smad family member 2 (Smad2) mRNAs

OBJECTIVE

β-cell microRNA-21 (miR-21) is increased by islet inflammatory stress but it decreases glucose-stimulated insulin secretion (GSIS). Thus, we sought to define the effects of miR-21 on β-cell function using in vitro and in vivo systems.

METHODS

We developed a tetracycline-on system of pre-miR-21 induction in clonal β-cells and human islets, along with transgenic zebrafish and mouse models of β-cell-specific pre-miR-21 overexpression.

RESULTS

β-cell miR-21 induction markedly reduced GSIS and led to reductions in transcription factors associated with β-cell identity and increased markers of dedifferentiation, which led us to hypothesize that miR-21 induces β-cell dysfunction by loss of cell identity. In silico analysis identified transforming growth factor-beta 2 (Tgfb2) and Smad family member 2 (Smad2) mRNAs as predicted miR-21 targets associated with the maintenance of β-cell identity. Tgfb2 and Smad2 were confirmed as direct miR-21 targets through RT-PCR, immunoblot, pulldown, and luciferase assays. In vivo zebrafish and mouse models exhibited glucose intolerance, decreased peak GSIS, decreased expression of β-cell identity markers, increased insulin and glucagon co-staining cells, and reduced Tgfb2 and Smad2 expression.

CONCLUSIONS

These findings implicate miR-21-mediated reduction of mRNAs specifying β-cell identity as a contributor to β-cell dysfunction by the loss of cellular differentiation.

Worldwide flavor enhancer monosodium glutamate combined with high lipid diet provokes metabolic alterations and systemic anomalies: An overview

•

Flavor enhancing high lipid diet acts as silent killer.

•

Monosodium glutamate mixed with high lipid diet alters redox-status.

•

Monosodium glutamate mixed with high lipid diet induces systemic anomalies.

In this fast-food era, people depend on ready-made foods and engage in minimal physical activities that ultimately change their food habits. Majorities of such foods have harmful effects on human health due to higher percentages of saturated fatty acids, trans-fatty acids, and hydrogenated fats in the form of high lipid diet (HLD). Moreover, food manufacturers add monosodium glutamate (MSG) to enhance the taste and palatability of the HLD. Both MSG and HLD induce the generation of reactive oxygen species (ROS) and thereby alter the redox-homeostasis to cause systemic damage. However, MSG mixed HLD (MH) consumption leads to dyslipidemia, silently develops non-alcoholic fatty liver disease followed by metabolic alterations and systemic anomalies, even malignancies, via modulating different signaling pathways. This comprehensive review formulates health care strategies to create global awareness about the harmful impact of MH on the human body and recommends the daily consumption of more natural foods rich in antioxidants instead of toxic ingredients to counterbalance the MH-induced systemic anomalies.

TGF-β Signaling in Pancreatic Islet β Cell Development and Function

Pancreatic islet beta cells (β-cells) synthesize and secrete insulin in response to rising glucose levels and thus are a prime target in both major forms of diabetes. Type 1 diabetes ensues due to autoimmune destruction of β-cells. On the other hand, the prevailing insulin resistance and hyperglycemia in type 2 diabetes (T2D) elicits a compensatory response from β-cells that involves increases in β-cell mass and function. However, the sustained metabolic stress results in β-cell failure, characterized by severe β-cell dysfunction and loss of β-cell mass. Dynamic changes to β-cell mass also occur during pancreatic development that involves extensive growth and morphogenesis. These orchestrated events are triggered by multiple signaling pathways, including those representing the transforming growth factor β (TGF-β) superfamily. TGF-β pathway ligands play important roles during endocrine pancreas development, β-cell proliferation, differentiation, and apoptosis. Furthermore, new findings are suggestive of TGF-β's role in regulation of adult β-cell mass and function. Collectively, these findings support the therapeutic utility of targeting TGF-β in diabetes. Summarizing the role of the various TGF-β pathway ligands in β-cell development, growth and function in normal physiology, and during diabetes pathogenesis is the topic of this mini-review.

Pre-existing beta cells but not progenitors contribute to new beta cells in the adult pancreas

It has been suggested that new beta cells can arise from specific populations of adult pancreatic progenitors or facultative stem cells. However, their existence remains controversial, and the conditions under which they would contribute to new beta-cell formation are not clear. Here, we use a suite of mouse models enabling dual-recombinase-mediated genetic tracing to simultaneously fate map insulin-positive and insulin-negative cells in the adult pancreas. We find that the insulin-negative cells, of both endocrine and exocrine origin, do not generate new beta cells in the adult pancreas during homeostasis, pregnancy or injury, including partial pancreatectomy, pancreatic duct ligation or beta-cell ablation with streptozotocin. However, non-beta cells can give rise to insulin-positive cells after extreme genetic ablation of beta cells, consistent with transdifferentiation. Together, our data indicate that pancreatic endocrine and exocrine progenitor cells do not contribute to new beta-cell formation in the adult mouse pancreas under physiological conditions.

Protection from β-cell apoptosis by inhibition of TGF-β/Smad3 signaling

Prevailing insulin resistance and the resultant hyperglycemia elicits a compensatory response from pancreatic islet beta cells (β-cells) that involves increases in β-cell function and β-cell mass. However, the sustained metabolic stress eventually leads to β-cell failure characterized by severe β-cell dysfunction and progressive loss of β-cell mass. Whereas, β-cell dysfunction is relatively well understood at the mechanistic level, the avenues leading to loss of β-cell mass are less clear with reduced proliferation, dedifferentiation, and apoptosis all potential mechanisms. Butler and colleagues documented increased β-cell apoptosis in pancreas from lean and obese human Type 2 diabetes (T2D) subjects, with no changes in rates of β-cell replication or neogenesis, strongly suggesting a role for apoptosis in β-cell failure. Here, we describe a permissive role for TGF-β/Smad3 in β-cell apoptosis. Human islets undergoing β-cell apoptosis release increased levels of TGF-β1 ligand and phosphorylation levels of TGF-β's chief transcription factor, Smad3, are increased in human T2D islets suggestive of an autocrine role for TGF-β/Smad3 signaling in β-cell apoptosis. Smad3 phosphorylation is similarly increased in diabetic mouse islets undergoing β-cell apoptosis. In mice, β-cell-specific activation of Smad3 promotes apoptosis and loss of β-cell mass in association with β-cell dysfunction, glucose intolerance, and diabetes. In contrast, inactive Smad3 protects from apoptosis and preserves β-cell mass while improving β-cell function and glucose tolerance. At the molecular level, Smad3 associates with Foxo1 to propagate TGF-β-dependent β-cell apoptosis. Indeed, genetic or pharmacologic inhibition of TGF-β/Smad3 signals or knocking down Foxo1 protects from β-cell apoptosis. These findings reveal the importance of TGF-β/Smad3 in promoting β-cell apoptosis and demonstrate the therapeutic potential of TGF-β/Smad3 antagonism to restore β-cell mass lost in diabetes.

SMAD7 enhances adult β-cell proliferation without significantly affecting β-cell function in mice

The interplay between the transforming growth factor β (TGF-β) signaling proteins, SMAD family member 2 (SMAD2) and 3 (SMAD3), and the TGF-β-inhibiting SMAD, SMAD7, seems to play a vital role in proper pancreatic endocrine development and also in normal β-cell function in adult pancreatic islets. Here, we generated conditional SMAD7 knockout mice by crossing insulin1^Cre mice with SMAD7^fx/fx mice. We also created a β cell-specific SMAD7-overexpressing mouse line by crossing insulin1^Dre mice with HPRT-SMAD7/RosaGFP mice. We analyzed β-cell function in adult islets when SMAD7 was either absent or overexpressed in β cells. Loss of SMAD7 in β cells inhibited proliferation, and SMAD7 overexpression enhanced cell proliferation. However, alterations in basic glucose homeostasis were not detectable following either SMAD7 deletion or overexpression in β cells. Our results show that both the absence and overexpression of SMAD7 affect TGF-β signaling and modulates β-cell proliferation but does not appear to alter β-cell function. Reversible SMAD7 overexpression may represent an attractive therapeutic option to enhance β-cell proliferation without negative effects on β-cell function.

Placental growth factor in beta cells plays an essential role in gestational beta-cell growth

OBJECTIVE

Pancreatic beta cells proliferate in response to metabolic requirements during pregnancy, while failure of this response may cause gestational diabetes. A member of the vascular endothelial growth factor family, placental growth factor (PlGF), typically plays a role in metabolic disorder and pathological circumstance. The expression and function of PlGF in the endocrine pancreas have not been reported and are addressed in the current study.

RESEARCH DESIGN AND METHODS

PlGF levels in beta cells were determined by immunostaining or ELISA in purified beta cells in non-pregnant and pregnant adult mice. An adeno-associated virus (AAV) serotype 8 carrying a shRNA for PlGF under the control of a rat insulin promoter (AAV-rat insulin promoter (RIP)-short hairpin small interfering RNA for PlGF (shPlGF)) was prepared and infused into mouse pancreas through the pancreatic duct to specifically knock down PlGF in beta cells, and its effects on beta-cell growth were determined by beta-cell proliferation, beta-cell mass and insulin release. A macrophage-depleting reagent, clodronate, was coapplied into AAV-treated mice to study crosstalk between beta cells and macrophages.

RESULTS

PlGF is exclusively produced by beta cells in the adult mouse pancreas. Moreover, PlGF expression in beta cells was significantly increased during pregnancy. Intraductal infusion of AAV-RIP-shPlGF specifically knocked down PlGF in beta cells, resulting in compromised beta-cell proliferation, reduced growth in beta-cell mass and impaired glucose tolerance during pregnancy. Mechanistically, PlGF depletion in beta cells reduced islet infiltration of trophic macrophages, which appeared to be essential for gestational beta-cell growth.

CONCLUSIONS

Our study suggests that increased expression of PlGF in beta cells may trigger gestational beta-cell growth through recruited macrophages.

Improved therapeutic effects on diabetic foot by human mesenchymal stem cells expressing MALAT1 as a sponge for microRNA-205-5p

Diabetic foot (DF) is a common complication of high severity for diabetes, a prevalent metabolic disorder that affects billions of people worldwide. Mesenchymal stem cells (MSCs) have a demonstrative therapeutic effect on DF, through their generation of pro-angiogenesis factors, like vascular endothelial growth factor (VEGF). Recently, genetically modified MSCs have been used in therapy and we have shown that depletion of micoRNA-205-5p (miR-205-5p) in human MSCs promotes VEGF-mediated therapeutic effects on DF. Here, we showed that a long non-coding RNA (lncRNA), MALAT1, is a competing endogenous RNA (ceRNA) for miR-205-5p, and is low expressed in human MSCs. Ectopic expression of MALAT1 in human MSCs significantly decreased miR-205-5p levels, resulting in upregulation of VEGF production and improved in vitro endothelial cell tube formation. In a DF model in immunodeficient NOD/SCID mice, transplantation of human miR-205-5p-depleted MSCs exhibited better therapeutic effects on DF recovery than control MSCs. Moreover, MALAT1-expressing MSCs showed even better therapeutic effects on DF recovery than miR-205-5p-depleted MSCs. This difference in DF recovery was shown to be associated with the levels of on-site vascularization. Together, our data suggest that MALAT1 functions as a sponge RNA for miR-205-5p to increase therapeutic effects of MSCs on DF.

Milk exosomal miRNAs: potential drivers of AMPK-to-mTORC1 switching in β-cell de-differentiation of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) steadily increases in prevalence since the 1950's, the period of widespread distribution of refrigerated pasteurized cow's milk. Whereas breastfeeding protects against the development of T2DM in later life, accumulating epidemiological evidence underlines the role of cow's milk consumption in T2DM. Recent studies in rodent models demonstrate that during the breastfeeding period pancreatic β-cells are metabolically immature and preferentially proliferate by activation of mechanistic target of rapamycin complex 1 (mTORC1) and suppression of AMP-activated protein kinase (AMPK). Weaning determines a metabolic switch of β-cells from a proliferating, immature phenotype with low insulin secretion to a differentiated mature phenotype with glucose-stimulated insulin secretion, less proliferation, reduced mTORC1- but increased AMPK activity. Translational evidence presented in this perspective implies for the first time that termination of milk miRNA transfer is the driver of this metabolic switch. miRNA-148a is a key inhibitor of AMPK and phosphatase and tensin homolog, crucial suppressors of mTORC1. β-Cells of diabetic patients return to the postnatal phenotype with high mTORC1 and low AMPK activity, explained by continuous transfer of bovine milk miRNAs to the human milk consumer. Bovine milk miRNA-148a apparently promotes β-cell de-differentiation to the immature mTORC1-high/AMPK-low phenotype with functional impairments in insulin secretion, increased mTORC1-driven endoplasmic reticulum stress, reduced autophagy and early β-cell apoptosis. In contrast to pasteurized cow's milk, milk's miRNAs are inactivated by bacterial fermentation, boiling and ultra-heat treatment and are missing in current infant formula. Persistent milk miRNA signaling adds a new perspective to the pathogenesis of T2DM and explains the protective role of breastfeeding but the diabetogenic effect of continued milk miRNA signaling by persistent consumption of pasteurized cow's milk.

Evidence of a developmental origin for β-cell heterogeneity using a dual lineage-tracing technology

The Cre/loxP system has been used extensively in mouse models with a limitation of one lineage at a time. Differences in function and other properties among populations of adult β-cells is termed β-cell heterogeneity, which was recently associated with diabetic phenotypes. Nevertheless, the presence of a developmentally derived β-cell heterogeneity is unclear. Here, we have developed a novel dual lineage-tracing technology, using a combination of two recombinase systems, Dre/RoxP and Cre/LoxP, to independently trace green fluorescent Pdx1-lineage cells and red fluorescent Ptf1a-lineage cells in the developing and adult mouse pancreas. We detected a few Pdx1⁺/Ptf1a^- lineage cells in addition to the vast majority of Pdx1⁺/Ptf1a⁺ lineage cells in the pancreas. Moreover, Pdx1⁺/Ptf1a⁺ lineage β-cells had fewer Ki-67⁺ proliferating β-cells, and expressed higher mRNA levels of insulin, Glut2, Pdx1, MafA and Nkx6.1, but lower CCND1 and CDK4 levels, compared with Pdx1⁺/Ptf1a^- lineage β-cells. Furthermore, more TSQ-high, SSC-high cells were detected in the Pdx1⁺Ptf1a⁺ lineage population than in the Pdx1⁺Ptf1a^- lineage population. Together, these data suggest that differential activation of Ptf1a in the developing pancreas may correlate with this β-cell heterogeneity.

The role of ORMDL3/ATF6 in compensated beta cell proliferation during early diabetes

Endoplasmic reticulum (ER) stress in beta cells induces a signaling network called the unfolded protein response (UPR), which plays a dual role in diabetes. A key regulator of ER-stress and UPR, the orosomucoid 1-like protein 3 (ORMDL3), has been shown to regulate airway remodeling through a major UPR protein, activating transcription factor 6 (ATF6), but the contribution of this regulatory axis to compensatory pancreatic beta cell proliferation in diabetes has not been studied. Here, we detected significantly lower levels of ORMDL3 mRNA in leukocytes of peripheral blood specimens from type 1 diabetes (T1D) children, compared to normal children. Moreover, these ORMDL3 levels in T1D children exhibited further decreases upon follow-up. ORMDL3 levels in islets from NOD mice, a mouse model for T1D in humans, showed a mild increase before diabetes onset, but a gradual decrease subsequently. In high glucose culture, beta cell proliferation, but not apoptosis, was increased by overexpression of ORMDL3 levels, likely mediated by its downstream factor ATF6. Mechanistically, ORMDL3 transcriptionally activated ATF6, which was confirmed in a promoter reporter assay. Together, our data suggest that ORMDL3 may increase beta cell proliferation through ATF6 as an early compensatory change in response to diabetes.

Calpastatin Mediates Development of Alzheimer's Disease in Diabetes

Aged people have a high chance to develop two prevalent diseases, diabetes and Alzheimer's disease (AD), which are characterized with hyperglycemia and neurodegeneration, respectively. Interestingly, recent evidence suggest that diabetes is a predisposing factor for AD. Nevertheless, the mechanisms underlying the association of diabetes with AD remain poorly defined. Here, we studied the effects of diabetes on AD in mice. The APP-PS1 mouse, an AD-prone strain, was administrated with streptozotocin (STZ) to destroy 75% beta cell mass to induce sustained hyperglycemia. We found that STZ-treated APP-PS1 mice exhibited poorer performance in the social recognition test, Morris water maze, and plus-maze discriminative avoidance task, compared to saline-treated normoglycemic APP-PS1 mice, likely resulting from increases in brain deposition of amyloid-β peptide aggregates (Aβ). Since formation of Aβ is known to be induced by protein hyperphosphorylation mediated by calpain (CAPN)-induced cleavage of p35 into p25, we examined levels of these proteins in mouse brain. We detected not only increased p35-to-p25 conversion, but also enhanced CAPN1 activity via increased protein but not mRNA levels. The internal CAPN1 inhibitor, calpastatin (CAST), was downregulated in STZ-treated APP-PS1 mouse brain, as a basis for the increase in CAPN1. In vitro, a human neuronal cell line, HCN-2, increased CAPN1 activity and downregulated CAST levels when incubated for 8 days in high glucose level, resulting in increased cell apoptosis. Together, these data suggest that chronic hyperglycemia may promote AD development through downregulating CAST.

Endogenous Reprogramming of Alpha Cells into Beta Cells, Induced by Viral Gene Therapy, Reverses Autoimmune Diabetes

Successful strategies for treating type 1 diabetes need to restore the function of pancreatic beta cells that are destroyed by the immune system and overcome further destruction of insulin-producing cells. Here, we infused adeno-associated virus carrying Pdx1 and MafA expression cassettes through the pancreatic duct to reprogram alpha cells into functional beta cells and normalized blood glucose in both beta cell-toxin-induced diabetic mice and in autoimmune non-obese diabetic (NOD) mice. The euglycemia in toxin-induced diabetic mice and new insulin⁺ cells persisted in the autoimmune NOD mice for 4 months prior to reestablishment of autoimmune diabetes. This gene therapy strategy also induced alpha to beta cell conversion in toxin-treated human islets, which restored blood glucose levels in NOD/SCID mice upon transplantation. Hence, this strategy could represent a new therapeutic approach, perhaps complemented by immunosuppression, to bolster endogenous insulin production. Our study thus provides a potential basis for further investigation in human type 1 diabetes.

The Role of the TGFβ Receptor Signaling Pathway in Adult Beta Cell Proliferation

Diabetes is a global epidemic and affects millions of individuals in the United States. Devising novel treatments for diabetes continues to be a great medical challenge. Postnatal beta cell growth or compensation is largely attributed to beta cell proliferation, which declines continuously with age. To boost beta cell proliferation to regenerate an adequate functional mass, there is a need to understand the signaling pathways that regulate beta cell proliferation for creating practical strategies to promote the process. Transforming growth factor β (TGFβ) belongs to a signaling superfamily that governs pancreatic development and the regeneration of beta cells after pancreatic diseases. TGFβ exerts its functions by activation of downstream Smad proteins and through its crosstalk with other pathways. Accumulating data demonstrate that the TGFβ receptor signaling pathway also participates in the control of beta cell proliferation. This review details the role of the TGFβ receptor signaling pathway in beta cell proliferation physiologically and in the pathogenesis of diabetes.

Cellular signaling pathways regulating β-cell proliferation as a promising therapeutic target in the treatment of diabetes

It is established that a decrease in β-cell number and deficiency in the function of existing β-cells contribute to type 1 and type 2 diabetes mellitus. Therefore, a major focus of current research is to identify novel methods of improving the number and function of β-cells, so as to prevent and/or postpone the development of diabetes mellitus and potentially reverse diabetes mellitus. Based on prior knowledge of the above-mentioned causes, promising therapeutic approaches may include direct transplantation of islets, implantation and subsequent induced differentiation of progenitors/stem cells to β-cells, replication of pre-existing β-cells, or activation of endogenous β-cell progenitors. More recently, with regards to cell replacement and regenerative treatment for diabetes patients, the identification of cellular signaling pathways with related genes or corresponding proteins involved in diabetes has become a topic of interest. However, the majority of pathways and molecules associated with β-cells remain unresolved, and the specialized functions of known pathways remain unclear, particularly in humans. The current article has evaluated the progress of research on pivotal cellular signaling pathways involved with β-cell proliferation and survival, and their validity for therapeutic adult β-cell regeneration in diabetes. More efforts are required to elucidate the cellular events involved in human β-cell proliferation in terms of the underlying mechanisms and functions.

Macrophage Polarization in Chronic Inflammatory Diseases: Killers or Builders?

Macrophages are key cellular components of the innate immunity, acting as the main player in the first-line defence against the pathogens and modulating homeostatic and inflammatory responses. Plasticity is a major feature of macrophages resulting in extreme heterogeneity both in normal and in pathological conditions. Macrophages are not homogenous, and they are generally categorized into two broad but distinct subsets as either classically activated (M1) or alternatively activated (M2). However, macrophages represent a continuum of highly plastic effector cells, resembling a spectrum of diverse phenotype states. Induction of specific macrophage functions is closely related to the surrounding environment that acts as a relevant orchestrator of macrophage functions. This phenomenon, termed polarization, results from cell/cell, cell/molecule interaction, governing macrophage functionality within the hosting tissues. Here, we summarized relevant cellular and molecular mechanisms driving macrophage polarization in "distant" pathological conditions, such as cancer, type 2 diabetes, atherosclerosis, and periodontitis that share macrophage-driven inflammation as a key feature, playing their dual role as killers (M1-like) and/or builders (M2-like). We also dissect the physio/pathological consequences related to macrophage polarization within selected chronic inflammatory diseases, placing polarized macrophages as a relevant hallmark, putative biomarkers, and possible target for prevention/therapy.

Long non-coding RNA MEG3 mediates high glucose-induced endothelial cell dysfunction

Long noncoding RNAs (lncRNAs) are implicated in the progression of diabetes mellitus (DM) and diabetes-induced endothelial dysfunction. Maternally expressed gene 3 (MEG3) encodes an lncRNA which is suggested to function as a tumor suppressor. Therefore, the aim of the present study was to investigate whether MEG3 is a potential regulator and molecular biomarker of high glucose-induced endothelial dysfunction. LncRNA Meg3-specific small interfering RNA (siRNA) and scrambled (Scr) siRNA were transfected for MEG3 dysfunction studies. RNA and protein expression were examined by quantitative RT-PCR (qPCR) and Western blot, respectively. The percentage of apoptotic cells was measured by flow cytometry. Cell viability was determined through MTT assay. This study demonstrates involvement of lncRNA MEG3 in high glucose-induced endothelial dysfunction. MEG3 is significantly downregulated in an endothelial cell model of hyperglycemia. In addition, MEG3 knockdown could exacerbate inflammatory damage in endothelial cells. Interestingly, MEG3 knockdown in HUVECs significantly induced proliferation and inhibited apoptosis by upregulating Bcl-2 and downregulating Bax, caspase-3, and P53. It should be noted that MEG3 knockdown could activate the TGF-β signaling pathway via upregulating TGF-β1, SMAD2, and SMAD7 and activate the Wnt/β-catenin signaling pathway via upregulating β-catenin and Cyclin D1 and downregulating TCF7L2. Our results indicate that MEG3 can be regarded as a novel therapeutic target and molecular biomarker for high glucose-induced endothelial dysfunction.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

Macrophage Polarization in Chronic Inflammatory Diseases: Killers or Builders?

Macrophages are key cellular components of the innate immunity, acting as the main player in the first-line defence against the pathogens and modulating homeostatic and inflammatory responses. Plasticity is a major feature of macrophages resulting in extreme heterogeneity both in normal and in pathological conditions. Macrophages are not homogenous, and they are generally categorized into two broad but distinct subsets as either classically activated (M1) or alternatively activated (M2). However, macrophages represent a continuum of highly plastic effector cells, resembling a spectrum of diverse phenotype states. Induction of specific macrophage functions is closely related to the surrounding environment that acts as a relevant orchestrator of macrophage functions. This phenomenon, termed polarization, results from cell/cell, cell/molecule interaction, governing macrophage functionality within the hosting tissues. Here, we summarized relevant cellular and molecular mechanisms driving macrophage polarization in “distant” pathological conditions, such as cancer, type 2 diabetes, atherosclerosis, and periodontitis that share macrophage-driven inflammation as a key feature, playing their dual role as killers (M1-like) and/or builders (M2-like). We also dissect the physio/pathological consequences related to macrophage polarization within selected chronic inflammatory diseases, placing polarized macrophages as a relevant hallmark, putative biomarkers, and possible target for prevention/therapy.

Augmentation of hypoxia-inducible factor-1-alpha in reinfused blood cells enhances diabetic ischemic wound closure in mice

Diabetes-associated dysfunction in angiogenesis predominantly contributes to impairment of wound closure, but a role of hypoxia-inducible factor 1 alpha (HIF-1a) in the process remain poorly understood. Here, we examined whether expression of HIF-1a in re-infused blood cells may improve the diabetic wound closure in mice. We found that that expression of HIF-1a in re-infused isogeneic blood cells significantly improved diabetic wound healing in mice, seemingly through augmentation of wound-associated angiogenesis. Mechanistically, expression of HIF-1a in re-infused blood cells significantly increased macrophage infiltration at the wound site, and macrophages produced vascular endothelial growth factor A (VEGF-A) to promote wound-associated angiogenesis. Together, our data suggest that augmentation of HIF-1a in reinfused blood cells may enhance diabetic ischemic wound closure.

Autophagy protects pancreatic beta cell mass and function in the setting of a high-fat and high-glucose diet

Autophagy is a major regulator of pancreatic beta cell homeostasis. Altered autophagic activity has been implicated in the beta cells of patients with type 2 diabetes, and in the beta cells of obese diabetic rodents. Here, we show that autophagy was induced in beta cells by either a high-fat diet or a combined high-fat and high-glucose diet, but not by high-glucose alone. However, a high-glucose intake alone did increase beta cell mass and insulin secretion moderately. Depletion of Atg7, a necessary component of the autophagy pathway, in beta cells by pancreatic intra-ductal AAV8-shAtg7 infusion in C57BL/6 mice, resulted in decreased beta cell mass, impaired glucose tolerance, defective insulin secretion, and increased apoptosis when a combined high-fat and high-glucose diet was given, seemingly due to suppression of autophagy. Taken together, our findings suggest that the autophagy pathway may act as a protective mechanism in pancreatic beta cells during a high-calorie diet.

ERK5 plays an essential role in gestational beta-cell proliferation

OBJECTIVES

Restoring a functional beta-cell mass is a fundamental goal in treating diabetes. A complex signalling pathway network coordinates the regulation of beta-cell proliferation, although a role for ERK5 in this network has not been reported. This question was addressed in this study.

MATERIALS AND METHODS

We studied the activation of extracellular-signal-regulated kinase 5 (ERK5) in pregnant mice, a well-known mouse model of increased beta-cell proliferation. A specific inhibitor of ERK5 activation, BIX02189, was intraperitoneally injected into the pregnant mice to suppress ERK5 signalling. Beta-cell proliferation was determined by quantification of Ki-67⁺ beta cells. Beta-cell apoptosis was determined by TUNEL assay. The extent of beta-cell proliferation was determined by beta-cell mass. The alteration of ERK5 activation and CyclinD1 levels in purified mouse islets was examined by Western blotting.

RESULTS

Extracellular-signal-regulated kinase 5 phosphorylation, which represents ERK5 activation, was significantly upregulated in islets from pregnant mice. Suppression of ERK5 activation by BIX02189 in pregnant mice significantly reduced beta-cell proliferation, without affecting beta-cell apoptosis, resulting in increases in random blood glucose levels and impairment of glucose response of the mice. ERK5 seemed to activate CyclinD1 to promote gestational beta-cell proliferation.

CONCLUSIONS

Extracellular-signal-regulated kinase 5 plays an essential role in the gestational augmentation of beta-cell proliferation. ERK5 may be a promising target for increasing beta-cell mass in diabetes patients.

Gene expression signature predicts human islet integrity and transplant functionality in diabetic mice

There is growing evidence that transplantation of cadaveric human islets is an effective therapy for type 1 diabetes. However, gauging the suitability of islet samples for clinical use remains a challenge. We hypothesized that islet quality is reflected in the expression of specific genes. Therefore, gene expression in 59 human islet preparations was analyzed and correlated with diabetes reversal after transplantation in diabetic mice. Analysis yielded 262 differentially expressed probesets, which together predict islet quality with 83% accuracy. Pathway analysis revealed that failing islet preparations activated inflammatory pathways, while functional islets showed increased regeneration pathway gene expression. Gene expression associated with apoptosis and oxygen consumption showed little overlap with each other or with the 262 probeset classifier, indicating that the three tests are measuring different aspects of islet cell biology. A subset of 36 probesets surpassed the predictive accuracy of the entire set for reversal of diabetes, and was further reduced by logistic regression to sets of 14 and 5 without losing accuracy. These genes were further validated with an independent cohort of 16 samples. We believe this limited number of gene classifiers in combination with other tests may provide complementary verification of islet quality prior to their clinical use.

SMAD3/Stat3 Signaling Mediates β-Cell Epithelial-Mesenchymal Transition in Chronic Pancreatitis-Related Diabetes

Many patients with chronic pancreatitis develop diabetes (chronic pancreatitis-related diabetes [CPRD]) through an undetermined mechanism. Here we used long-term partial pancreatic duct ligation (PDL) as a model to study CPRD. We found that long-term PDL induced significant β-cell dedifferentiation, followed by a time-dependent decrease in functional β-cell mass-all specifically in the ligated tail portion of the pancreas (PDL-tail). High levels of transforming growth factor β1 (TGFβ1) were detected in the PDL-tail and were mainly produced by M2 macrophages at the early stage and by activated myofibroblasts at the later stage. Loss of β-cell mass was then found to result from TGFβ1-triggered epithelial-mesenchymal transition (EMT) by β-cells, rather than resulting directly from β-cell apoptosis. Mechanistically, TGFβ1-treated β-cells activated expression of the EMT regulator gene Snail in a SMAD3/Stat3-dependent manner. Moreover, forced expression of forkhead box protein O1 (FoxO1), an antagonist for activated Stat3, specifically in β-cells ameliorated β-cell EMT and β-cell loss and prevented the onset of diabetes in mice undergoing PDL. Together, our data suggest that chronic pancreatitis may trigger TGFβ1-mediated β-cell EMT to lead to CPRD, which could substantially be prevented by sustained expression of FoxO1 in β-cells.

Unique Features of Pancreatic-Resident Regulatory T Cells in Autoimmune Type 1 Diabetes

Recent progress in regulatory T cells (Tregs) biology emphasizes the importance of understanding tissue-resident Tregs in response to tissue-specific environment. Now, emerging evidence suggests that pancreatic-resident forkhead box P3⁺ Tregs have distinguishable effects on the suppression of over-exuberant immune responses in autoimmune type 1 diabetes (T1D). Thus, there is growing interest in elucidating the role of pancreatic-resident Tregs that function and evolve in the local environment. In this review, we discuss the phenotype and function of Tregs residing in pancreatic tissues and pancreatic lymph nodes, with emphasis on the unique subpopulations of Tregs that control the disease progression in the context of T1D. Specifically, we discuss known and possible modulators that influence the survival, migration, and maintenance of pancreatic Tregs.

GLP-1/Exendin-4 induces β-cell proliferation via the epidermal growth factor receptor

Exendin-4 is a long acting glucagon-like peptide 1 (GLP-1) analogue that is an agonist for the GLP-1 receptor, a G-protein coupled receptor (GPCR). Exendin-4 is used to clinically improve glucose tolerance in diabetic patients due to its ability to enhance insulin secretion. In rodents, and possibly in humans, exendin-4 can stimulate β-cell proliferation. The exact mechanism of action to induce β-cell proliferation is not well understood. Here, using a β-cell specific epidermal growth factor receptor (EGFR) null mouse, we show that exendin-4 induced an increase in proliferation and β-cell mass through EGFR. Thus, our study sheds light on the role of EGFR signaling in the effects of exendin-4 on the control of blood glucose metabolism and β-cell mass.

Suppression of microRNA-205-5p in human mesenchymal stem cells improves their therapeutic potential in treating diabetic foot disease

Diabetes is a prevalent disease endangering human health, while diabetic foot disease (DF) is one of the most severe complications of diabetes. Mesenchymal stem cells (MSCs) have been used in DF treatment, taking advantage of the differentiation potential of MSCs into endothelial cells and their production and secretion of trophic factors like vascular endothelial growth factor (VEGF). Molecular modification of MSCs to improve their therapeutic effects has been recently applied in treating other diseases, but not yet in DF. Here, we found that micoRNA-205-5p (miR-205-5p) is expressed in human MSCs, and miR-205-5p inhibits protein translation of VEGF through its interaction with 3′-UTR of the VEGF mRNA. Expression of antisense of miR-205-5p (as-miR-205-5p) significantly increased both cellular and secreted VEGF by MSCs, which significantly improved the therapeutic effects of MSCs on DF-associated wound healing in diabetic NOD/SCID mice. Together, our data suggest that miR-205-5p suppression in MSCs may improve their therapeutic effects on DF, seemingly through augmentation of VEGF-mediated vascularization.

Phytosterol esters attenuate hepatic steatosis in rats with non-alcoholic fatty liver disease rats fed a high-fat diet

Given the adverse effects of drugs used for NAFLD treatment, identifying novel and effective natural compound to prevent NAFLD is urgently needed. In the present study, the effects of phytosterol esters (PSEs) on NAFLD were explored. Adult SD rats were randomized into five groups: normal chow diet (NC), high-fat diet (HF), low-, medium- and high-dose PSE treatment plus high-fat diet groups (PSEL, PSEM, and PSEH). Our results showed that the levels of LDL-C in the PSEL group and hepatic TG, TC, and FFA in the three PSEs groups were significantly decreased. Notably, the uric acid (UA) level was significantly decreased by PSEs intervention. The hepatic inflammatory stress was ameliorated via the inhibition of the cytokines, including TGF-β, IL-6, IL-10 and CRP in the PSEs intervention groups. Further, the oxidative status was improved by PSE treatment through adjusting the enzyme activity (SOD and XOD) and decreasing the MDA level. These beneficial effects of PSE may have been partly due to its regulation on the expression of TGF-β1, TGF-β2, TNF-α, UCP-2, PPAR-α and PPAR-γ in hepatic tissue at both mRNA and protein level. The results of this study suggest that PSEs may be used as therapeutic agents for the prevention and progression of NAFLD and that hyperuricemia is induced by high-fat diet consumption.

Beta Cell Regeneration in Adult Mice: Controversy Over the Involvement of Stem Cells

Islet transplantation is an effective therapy for severe diabetes. Nevertheless, the short supply of donor pancreases constitutes a formidable obstacle to its extensive clinical application. This shortage heightens the need for alternative sources of insulin-producing beta cells. Since mature beta cells have a very slow proliferation rate, which further declines with age, great efforts have been made to identify beta cell progenitors in the adult pancreas. However, the question whether facultative beta cell progenitors indeed exist in the adult pancreas remains largely unresolved. In the current review, we discuss the problems in past studies and review the milestone studies and recent publications.

Forkhead Box Protein 1 (FoxO1) Inhibits Accelerated β Cell Aging in Pancreas-specific SMAD7 Mutant Mice

The mechanisms underlying the effects of exocrine dysfunction on the development of diabetes remain largely unknown. Here we show that pancreatic depletion of SMAD7 resulted in age-dependent increases in β cell dysfunction with accelerated glucose intolerance, followed by overt diabetes. The accelerated β cell dysfunction and loss of proliferation capacity, two features of β cell aging, appeared to be non-cell-autonomous, secondary to the adjacent exocrine failure as a "bystander effect." Increased Forkhead box protein 1 (FoxO1) acetylation and nuclear retention was followed by progressive FoxO1 loss in β cells that marked the onset of diabetes. Moreover, forced FoxO1 expression in β cells prevented β cell dysfunction and loss in this model. Thus, we present a model of accelerated β cell aging that may be useful for studying the mechanisms underlying β cell failure in diabetes. Moreover, we provide evidence highlighting a critical role of FoxO1 in maintaining β cell identity in the context of SMAD7 failure.

Islet inflammation in type 2 diabetes and physiology

The finding of islet inflammation in type 2 diabetes (T2D) and its involvement in β cell dysfunction has further highlighted the significance of inflammation in metabolic diseases. The number of intra-islet macrophages is increased in T2D, and these cells are the main source of proinflammatory cytokines within islets. Multiple human studies of T2D have shown that targeting islet inflammation has the potential to be an effective therapeutic strategy. In this Review we provide an overview of the cellular and molecular mechanisms by which islet inflammation develops and causes β cell dysfunction. We also emphasize the regulation and roles of macrophage polarity shift within islets in the context of T2D pathology and β cell health, which may have broad translational implications for therapeutics aimed at improving islet function.

A synopsis of factors regulating beta cell development and beta cell mass

The insulin-secreting beta cells in the endocrine pancreas regulate blood glucose levels, and loss of functional beta cells leads to insulin deficiency, hyperglycemia (high blood glucose) and diabetes mellitus. Current treatment strategies for type-1 (autoimmune) diabetes are islet transplantation, which has significant risks and limitations, or normalization of blood glucose with insulin injections, which is clearly not ideal. The type-1 patients can lack insulin counter-regulatory mechanism; therefore, hypoglycemia is a potential risk. Hence, a cell-based therapy offers a better alternative for the treatment of diabetes. Past research was focused on attempting to generate replacement beta cells from stem cells; however, recently there has been an increasing interest in identifying mechanisms that will lead to the conversion of pre-existing differentiated endocrine cells into beta cells. The goal of this review is to provide an overview of several of the key factors that regulate new beta cell formation (neogenesis) and beta cell proliferation.

Epidermal Growth Factor Receptor Signaling Regulates β Cell Proliferation in Adult Mice

A thorough understanding of the signaling pathways involved in the regulation of β cell proliferation is an important initial step in restoring β cell mass in the diabetic patient. Here, we show that epidermal growth factor receptor 1 (EGFR) was significantly up-regulated in the islets of C57BL/6 mice after 50% partial pancreatectomy (PPx), a model for workload-induced β cell proliferation. Specific deletion of EGFR in the β cells of adult mice impaired β cell proliferation at baseline and after 50% PPx, suggesting that the EGFR signaling pathway plays an essential role in adult β cell proliferation. Further analyses showed that β cell-specific depletion of EGFR resulted in impaired expression of cyclin D1 and impaired suppression of p27 after PPx, both of which enhance β cell proliferation. These data highlight the importance of EGFR signaling and its downstream signaling cascade in postnatal β cell growth.

MiR-497 enhances metastasis of oral squamous cell carcinoma through SMAD7 suppression

SMAD7 is a key inhibitor of transforming growth factor β (TGFβ) receptor signaling, which regulates the alteration of cancer cell invasiveness through epithelial-mesenchymal cell conversion. Since microRNAs (miRNAs) play a potential role in the tumorigenesis, cancer cell growth and metastases of oral squamous cell carcinoma (OSCC), determination of the involved miRNAs that may regulate SMAD7-mediated OSCC cell invasion appears to be one important question. Here, we found that the levels of miR-497 were significantly increased and the levels of SMAD7 were significantly decreased in OSCC specimens, compared to the paired adjacent non-tumor tissue. Moreover, miR-497 and SMAD7 inversely correlated in OSCC specimens. The 5-year survival of the patients with higher miR-497 levels in the resected OSCC was worse than those high miR-497 levels. Bioinformatics analyses showed that miR-497 targeted the 3'-UTR of SMAD7 mRNA to inhibit its translation, which was proved by luciferase reporter assay. Furthermore, miR-497 overexpression increased SMAD7-suppressed cell invasion, while miR-497 depletion decreased SMAD7-suppressed cell invasion in OSCC cells, in both a transwell cell invasion assay and a scratch would healing assay. Together, our data suggest that suppression of miR-497 in OSCC cells may promote cancer cell invasion via suppression of SMAD7, and highlight miR-497 as an intriguing therapeutic target to prevent OSCC metastases.

STAT3 modulates β-cell cycling in injured mouse pancreas and protects against DNA damage

Partial pancreatic duct ligation (PDL) of mouse pancreas induces a doubling of the β-cell mass mainly through proliferation of pre-existing and newly formed β-cells. The molecular mechanism governing this process is still largely unknown. Given the inflammatory nature of PDL and inflammation-induced signaling via the signal transducer and activator of transcription 3 (STAT3), the activation and the role of STAT3 in PDL-induced β-cell proliferation were investigated. Duct ligation stimulates the expression of several cytokines that can act as ligands inducing STAT3 signaling and phosphorylation in β-cells. β-Cell cycling increased by conditional β-cell-specific Stat3 knockout and decreased by STAT3 activation through administration of interleukin-6. In addition, the level of DNA damage in β-cells of PDL pancreas increased after deletion of Stat3. These data indicate a role for STAT3 in maintaining a steady state in the β-cell, by modulating its cell cycle and protection from DNA damage.

Inhibition of TGF-β Signaling Promotes Human Pancreatic β-Cell Replication

Diabetes is associated with loss of functional pancreatic β-cells, and restoration of β-cells is a major goal for regenerative therapies. Endogenous regeneration of β-cells via β-cell replication has the potential to restore cellular mass; however, pharmacological agents that promote regeneration or expansion of endogenous β-cells have been elusive. The regenerative capacity of β-cells declines rapidly with age, due to accumulation of p16(INK4a), resulting in limited capacity for adult endocrine pancreas regeneration. Here, we show that transforming growth factor-β (TGF-β) signaling via Smad3 integrates with the trithorax complex to activate and maintain Ink4a expression to prevent β-cell replication. Importantly, inhibition of TGF-β signaling can result in repression of the Ink4a/Arf locus, resulting in increased β-cell replication in adult mice. Furthermore, small molecule inhibitors of the TGF-β pathway promote β-cell replication in human islets transplanted into NOD-scid IL-2Rg(null) mice. These data reveal a novel role for TGF-β signaling in the regulation of the Ink4a/Arf locus and highlight the potential of using small molecule inhibitors of TGF-β signaling to promote human β-cell replication.

Transient Suppression of TGFβ Receptor Signaling Facilitates Human Islet Transplantation

Although islet transplantation is an effective treatment for severe diabetes, its broad application is greatly limited due to a shortage of donor islets. Suppression of TGFβ receptor signaling in β-cells has been shown to increase β-cell proliferation in mice, but has not been rigorously examined in humans. Here, treatment of human islets with a TGFβ receptor I inhibitor, SB-431542 (SB), significantly improved C-peptide secretion by β-cells, and significantly increased β-cell number by increasing β-cell proliferation. In addition, SB increased cell-cycle activators and decreased cell-cycle suppressors in human β-cells. Transplantation of SB-treated human islets into diabetic immune-deficient mice resulted in significant improvement in blood glucose control, significantly higher serum and graft insulin content, and significantly greater increases in β-cell proliferation in the graft, compared with controls. Thus, our data suggest that transient suppression of TGFβ receptor signaling may improve the outcome of human islet transplantation, seemingly through increasing β-cell number and function.