Stromal cell derived factor-1 (SDF-1)/CXCL12 attenuates diabetes in mice and promotes pancreatic beta-cell survival by activation of the prosurvival kinase Akt

Cross-species single-cell analysis uncovers the immunopathological mechanisms associated with IgA nephropathy progression

IgA nephropathy (IgAN) represents the main cause of renal failure, while the precise pathogenetic mechanisms have not been fully determined. Herein, we conducted a cross-species single-cell survey on human IgAN and mouse and rat IgAN models to explore the pathogenic programs. Cross-species single-cell RNA sequencing (scRNA-Seq) revealed that the IgAN mesangial cells (MCs) expressed high levels of inflammatory signatures CXCL12, CCL2, CSF1, and IL-34 and specifically interacted with IgAN macrophages via the CXCL12/CXCR4, CSF1/IL-34/CSF1 receptor, and integrin subunit alpha X/integrin subunit alpha M/complement C3 (C3) axes. IgAN macrophages expressed high levels of CXCR4, PDGFB, triggering receptor expressed on myeloid cells 2, TNF, and C3, and the trajectory analysis suggested that these cells derived from the differentiation of infiltrating blood monocytes. Additionally, protein profiling of 21 progression and 28 nonprogression IgAN samples revealed that proteins CXCL12, C3, mannose receptor C-type 1, and CD163 were negatively correlated with estimated glomerular filtration rate (eGFR) value and poor prognosis (30% eGFR as composite end point). Last, a functional experiment revealed that specific blockade of the Cxcl12/Cxcr4 pathway substantially attenuated the glomerulus and tubule inflammatory injury, fibrosis, and renal function decline in the mouse IgAN model. This study provides insights into IgAN progression and may aid in the refinement of IgAN diagnosis and the optimization of treatment strategies.

Extracellular metallothionein as a therapeutic target in the early progression of type 1 diabetes

Type 1 diabetes (T1D) is characterized by lymphocyte infiltration into the pancreatic islets of Langerhans, leading to the destruction of insulin-producing beta cells and uncontrolled hyperglycemia. In the nonobese diabetic (NOD) murine model of T1D, the onset of this infiltration starts several weeks before glucose dysregulation and overt diabetes. Recruitment of immune cells to the islets is mediated by several chemotactic cytokines, including CXCL10, while other cytokines, including SDF-1α, can confer protective effects. Global gene expression studies of the pancreas from prediabetic NOD mice and single-cell sequence analysis of human islets from prediabetic, autoantibody-positive patients showed an increased expression of metallothionein (MT), a small molecular weight, cysteine-rich metal-binding stress response protein. We have shown that beta cells can release MT into the extracellular environment, which can subsequently enhance the chemotactic response of Th1 cells to CXCL10 and interfere with the chemotactic response of Th2 cells to SDF-1α. These effects can be blocked in vitro with a monoclonal anti-MT antibody, clone UC1MT. When administered to NOD mice before the onset of diabetes, UC1MT significantly reduces the development of T1D. Manipulation of extracellular MT may be an important approach to preserving beta cell function and preventing the development of T1D.

Repressing miR-23a promotes the transdifferentiation of pancreatic α cells to β cells via negatively regulating the expression of SDF-1α

Pancreatic β-cell failure is a pathological feature in type 1 diabetes. One promising approach involves inducing transdifferentiation of related pancreatic cell types, specifically α cells that produce glucagon. The chemokine stromal cell-derived factor-1 alpha (SDF-1α) is implicated in pancreatic α-to-β like cell transition. Here, the serum level of SDF-1α was lower in T1D with C-peptide loss, the miR-23a was negatively correlated with SDF-1α. We discovered that exosomal miR-23a, secreted from β cells, functionally downregulates the expression of SDF-1α, leading to increased Pax4 expression and decreased Arx expression in vivo. Adenovirus-vectored miR-23a sponge and mimic were constructed to further explored the miR-23a on pancreatic α-to-β like cell transition in vitro, which yielded results consistent with our cell-based assays. Suppression of miR-23a upregulated insulin level and downregulated glucagon level in STZ-induced diabetes mice models, effectively promoting α-to-β like cell transition. Our findings highlight miR-23a as a new therapeutic target for regenerating pancreatic β cells from α cells.

Beta cell and immune cell interactions in autoimmune type 1 diabetes: How they meet and talk to each other

Background

Scope of review

Major conclusions

Bone marrow mesenchymal stromal cells for diabetes therapy: touch, fuse, and fix?

Bone marrow mesenchymal stromal cells (BM-MSCs) have anti-inflammatory and pro-survival properties. Naturally, they do not express human leukocyte antigen class II surface antigens and have immunosuppressive capabilities. Together with their relatively easy accessibility and expansion, they are an attractive tool for organ support in transplantation and regenerative therapy. Autologous BM-MSC transplantation alone or together with transplanted islets improves β-cell function, graft survival, and glycemic control in diabetes. Albeit MSCs’ capacity to transdifferentiate into β-cell is limited, their protective effects are mediated mainly by paracrine mechanisms through BM-MSCs circulating through the body. Direct cell–cell contact and spontaneous fusion of BM-MSCs with injured cells, although at a very low rate, are further mechanisms of their supportive effect and for tissue regeneration. Diabetes is a disease of long-term chronic inflammation and cell therapy requires stable, highly functional cells. Several tools and protocols have been developed by mimicking natural fusion events to induce and accelerate fusion in vitro to promote β-cell-specific gene expression in fused cells. BM-MSC-islet fusion before transplantation may be a strategy for long-term islet survival and improved function. This review discusses the cell-protective and anti-inflammatory characteristics of BM-MSCs to boost highly functional insulin-producing cells in vitro and in vivo, and the efficacy of their fusion with β-cells as a path to promote β-cell regeneration.

Metabolic Impact of MKP-2 Upregulation in Obesity Promotes Insulin Resistance and Fatty Liver Disease

The mechanisms connecting obesity with type 2 diabetes, insulin resistance, nonalcoholic fatty liver disease, and cardiovascular diseases remain incompletely understood. The function of MAPK phosphatase-2 (MKP-2), a type 1 dual-specific phosphatase (DUSP) in whole-body metabolism, and how this contributes to the development of diet-induced obesity, type 2 diabetes (T2D), and insulin resistance is largely unknown. We investigated the physiological contribution of MKP-2 in whole-body metabolism and whether MKP-2 is altered in obesity and human fatty liver disease using MKP-2 knockout mice models and human liver tissue derived from fatty liver disease patients. We demonstrate that, for the first time, MKP-2 expression was upregulated in liver tissue in humans with obesity and fatty liver disease and in insulin-responsive tissues in mice with obesity. MKP-2-deficient mice have enhanced p38 MAPK, JNK, and ERK activities in insulin-responsive tissues compared with wild-type mice. MKP-2 deficiency in mice protects against diet-induced obesity and hepatic steatosis and was accompanied by improved glucose homeostasis and insulin sensitivity. Mkp-2^−/− mice are resistant to diet-induced obesity owing to reduced food intake and associated lower respiratory exchange ratio. This was associated with enhanced circulating insulin-like growth factor-1 (IGF-1) and stromal cell-derived factor 1 (SDF-1) levels in Mkp-2^−/− mice. PTEN, a negative regulator of Akt, was downregulated in livers of Mkp-2^−/− mice, resulting in enhanced Akt activity consistent with increased insulin sensitivity. These studies identify a novel role for MKP-2 in the regulation of systemic metabolism and pathophysiology of obesity-induced insulin resistance and fatty liver disease.

Case Report: A Novel CXCR4 Mutation in a Chinese Child With Kawasaki Disease Causing WHIM Syndrome

WHIM syndrome, an extremely rare congenital disease with combined immunodeficiency, is mainly caused by heterozygous gain-of-function mutation in the CXCR4 gene. There have been no previous case reports of WHIM syndrome with Kawasaki disease. We herein report a case of a boy who developed Kawasaki disease at the age of 1 year. After treatment, the number of neutrophils in his peripheral blood decreased continuously. His medical history revealed that he had been suffering from leukopenia, neutropenia and low immunoglobulin since birth, and his neutrophils could return to the normal level in the presence of infection or inflammation. Clinical targeted gene sequencing of 91 genes associated with granulocyte-related disease revealed that the patient had a novel heterozygous NM_003467; c.1032_1033delTG;p.(E345Vfs*12) variant in exon 2 of CXCR4 gene. Family verification analysis by Sanger sequencing showed that his father also had heterozygous variation at this site, while other family members did not. The computer prediction software indicated that the variation had a high pathogenicity. The computational structure analysis of the mutant revealed significant structural and functional changes in the CXCR4 protein. It should be noted that when unexplained persistent neutropenia with low immunoglobulin occurs after birth, especially when there is a family history of neutropenia, immunodeficiency should be investigated with genetic testing.

Drug Discovery of Plausible Lead Natural Compounds That Target the Insulin Signaling Pathway: Bioinformatics Approaches

The growing smooth talk in the field of natural compounds is due to the ancient and current interest in herbal medicine and their potentially positive effects on health. Dozens of antidiabetic natural compounds were reported and tested in vivo, in silico, and in vitro. The role of these natural compounds, their actions on the insulin signaling pathway, and the stimulation of the glucose transporter-4 (GLUT4) insulin-responsive translocation to the plasma membrane (PM) are all crucial in the treatment of diabetes and insulin resistance. In this review, we collected and summarized a group of available in vivo and in vitro studies which targeted isolated phytochemicals with possible antidiabetic activity. Moreover, the in silico docking of natural compounds with some of the insulin signaling cascade key proteins is also summarized based on the current literature. In this review, hundreds of recent studies on pure natural compounds that alleviate type II diabetes mellitus (type II DM) were revised. We focused on natural compounds that could potentially regulate blood glucose and stimulate GLUT4 translocation through the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. On attempt to point out potential new natural antidiabetic compounds, this review also focuses on natural ingredients that were shown to interact with proteins in the insulin signaling pathway in silico, regardless of their in vitro/in vivo antidiabetic activity. We invite interested researchers to test these compounds as potential novel type II DM drugs and explore their therapeutic mechanisms.

Interorgan crosstalk in pancreatic islet function and pathology

Pancreatic β cells secrete insulin in response to glucose, a process that is regulated at multiple levels, including a network of input signals from other organ systems. Impaired islet function contributes to the pathogenesis of type 2 diabetes mellitus (T2DM), and targeting inter-organ communications, such as GLP-1 signalling, to enhance β-cell function has been proven to be a successful therapeutic strategy in the last decade. In this review, we will discuss recent advances in inter-organ communication from the metabolic, immune and neural system to pancreatic islets, their biological implication in normal pancreas endocrine function and their role in the (mal)adaptive responses of islet to nutrition-induced stress.

SDF-1 inhibits the dedifferentiation of islet β cells in hyperglycaemia by up-regulating FoxO1 via binding to CXCR4

Islet β cell dedifferentiation is one of the most important mechanisms in the occurrence and development of diabetes. We studied the possible effects of chemokine stromal cell-derived factor-1 (SDF-1) in the dedifferentiation of islet β cells. It was noted that the number of dedifferentiated islet β cells and the expression of SDF-1 in pancreatic tissues significantly increased with diabetes. In islet β cell experiments, inhibition of SDF-1 expression resulted in an increase in the number of dedifferentiated cells, while overexpression of SDF-1 resulted in a decrease. This seemed to be contradicted by the effect of diabetes on the expression of SDF-1 in pancreatic tissue, but it was concluded that this may be related to the loss of SDF-1 activity. SDF-1 binds to CXCR4 to form a complex, which activates and phosphorylates AKT, subsequently increases the expression of forkhead box O1 (FOXO1), and inhibits the dedifferentiation of islet β cells. This suggests that SDF-1 may be a novel target in the treatment of diabetes.

Bioinformatics analysis of an animal model of diet-induced nonalcoholic fatty liver disease with rapid progression

Nonalcoholic fatty liver disease (NAFLD) develops rapidly in high-fat diet (HFD) fed Mongolian gerbil (Meriones unguiculatus). Here, we aim to explore the gene expression characteristics of Mongolian gerbil to better understand the underlying mechanism in this animal model. Mongolian gerbils were fed with normal diet or HFD for different periods. High-throughput sequencing was carried out on the hepatic mRNA and bioinformatics analysis was further performed. Eight hub genes Cd44, App, Cdc42, Cd68, Cxcr4, Csf1r, Adgre1, and Fermt3, which were involved in inflammation, fibrosis, and HCC were obtained. Four significant independent poor prognostic factors for HCC (GPC1, ARPC1B, DAB2, and CFL1) were screened out. qRT-PCR result showed that the above genes expressed high levels in different periods of modeling process. The findings of this study provide useful information for further studies on Mongolian gerbil NAFLD model.

Chronic tissue inflammation and metabolic disease

In this review, Lee and Olefsky discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes.

Obesity is the most common cause of insulin resistance, and the current obesity epidemic is driving a parallel rise in the incidence of T2DM. It is now widely recognized that chronic, subacute tissue inflammation is a major etiologic component of the pathogenesis of insulin resistance and metabolic dysfunction in obesity. Here, we summarize recent advances in our understanding of immunometabolism. We discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes. Last, we also review current and potential new therapeutic strategies based on immunomodulation.

Decreased blood vessel density and endothelial cell subset dynamics during ageing of the endocrine system

Age-associated alterations of the hormone-secreting endocrine system cause organ dysfunction and disease states. However, the cell biology of endocrine tissue ageing remains poorly understood. Here, we perform comparative 3D imaging to understand age-related perturbations of the endothelial cell (EC) compartment in endocrine glands. Datasets of a wide range of markers highlight a decline in capillary and artery numbers, but not of perivascular cells in pancreas, testis and thyroid gland, with age in mice and humans. Further, angiogenesis and β-cell expansion in the pancreas are coupled by a distinct age-dependent subset of ECs. While this EC subpopulation supports pancreatic β cells, it declines during ageing concomitant with increased expression of the gap junction protein Gja1. EC-specific ablation of Gja1 restores β-cell expansion in the aged pancreas. These results provide a proof of concept for understanding age-related vascular changes and imply that therapeutic targeting of blood vessels may restore aged endocrine tissue function. This comprehensive data atlas offers over > 1,000 multicolour volumes for exploration and research in endocrinology, ageing, matrix and vascular biology.

γ-aminobutyric acid stimulates β-cell proliferation through the mTORC1/p70S6K pathway, an effect amplified by Ly49, a novel γ-aminobutyric acid type A receptor positive allosteric modulator

AIM

To examine the mechanism of action of γ-aminobutyric acid (GABA) on β-cell proliferation and investigate if co-treatment with Ly49, a novel GABA type A receptor positive allosteric modulator (GABA_A -R PAM), amplifies this effect.

METHODS

Human or mouse islets were co-treated for 4-5 days with GABA and selected receptor or cell signalling pathway modulators. Immunofluorescence was used to determine protein co-localization, cell number or proliferation, and islet size. Osmotic minipumps were surgically implanted in mice to assess Ly49 effects on pancreatic β-cells.

RESULTS

Amplification of GABA_A -R signalling enhanced GABA-stimulated β-cell proliferation in cultured mouse islets. Co-treatment of GABA with an inhibitor specific for PI3K, mTORC1/2, or p70S6K, abolished GABA-stimulated β-cell proliferation in mouse and human islets. Nuclear p-Akt^Ser473 and p-p70S6K^{Thr421/Ser424} expression in pancreatic β-cells was increased in GABA-treated mice compared with vehicle-treated mice, an effect augmented with GABA and Ly49 co-treatment. Mice co-treated with GABA and Ly49 exhibited enhanced β-cell area and proliferation compared with GABA-treated mice. Furthermore, S961 injection (an insulin receptor antagonist) resulted in enhanced plasma insulin in GABA and Ly49 co-treated mice compared with GABA-treated mice. Importantly, GABA co-treated with Ly49 increased β-cell proliferation in human islets providing a potential application for human subjects.

CONCLUSIONS

We show that GABA stimulates β-cell proliferation via the PI3K/mTORC1/p70S6K pathway in both mouse and human islets. Furthermore, we show that Ly49 enhances the β-cell regenerative effects of GABA, showing potential in the intervention of diabetes.

Sitagliptin ameliorates renal tubular injury in diabetic kidney disease via STAT3-dependent mitochondrial homeostasis through SDF-1α/CXCR4 pathway

Mitochondrial abnormalities play critical roles in diabetic tubular injury progression. Dipeptidyl peptidase-4 (DPP4) inhibitors are widely used antihyperglycemic agents that exert renal protective and positive effects against mitochondrial dysfunction in diabetic kidney disease (DKD). However, their underlying mechanism remains unclear. In this study, DPP4 upregulation, mitochondrial fragmentation, and altered mitochondrial dynamics-associated protein expression were observed in the tubules of DBA2/J (D2) diabetic mice with unilateral nephrectomy and in albumin-stimulated tubular cells. The inhibition of DPP4 by sitagliptin (Sita) ameliorated these mitochondrial perturbations both in vivo and in vitro, whereas DPP4 overexpression aggravated mitochondrial fusion-fission disorder and tubular cell injury in albumin-treated HK-2 cells. Downstream of DPP4, the SDF-1α/CXCR4 pathway was significantly suppressed in diabetic tubules. After Sita treatment, this signaling pathway was restored, and the mitochondrial dynamics was improved. Furthermore, a direct interaction between STAT3 and OPA1 was found in the mitochondria of tubular cells, and this effect was weakened by overloading albumin and by CXCR4 siRNA treatment, suggesting a possible link between DPP4-mediated SDF-1α/CXCR4/STAT3 signaling and mitochondrial dysfunction in diabetic tubular cells. The results suggest that a novel mechanism links the DPP4 enzyme to impaired mitochondrial dynamics homeostasis during tubular injury in DKD and highlight that the SDF-1α/CXCR4/STAT3 signaling pathway could become a potential target for managing DKD.

AMD3100 Attenuates Post-Traumatic Osteoarthritis by Maintaining Transforming Growth Factor-β1-Induced Expression of Tissue Inhibitor of Metalloproteinase-3 via the Phosphatidylinositol 3-Kinase/Akt Pathway

AMD3100 is a small-molecule inhibitor of the C-X-C motif chemokine ligand 12/C-X-C chemokine receptor type 4 (CXCL12/CXCR4) axis, while its role in aggrecan metabolism is unclear. We hypothesized that the AMD3100 modulates the transforming growth factor-β1 (TGF-β1)-induced expression of tissue inhibitor of metalloproteinase-3 (TIMP-3) in chondrocytes. We evaluated expression of CXCL12/CXCR4 and TIMP-3 in the knee joints of rats with and without osteoarthritis (OA) by immunohistochemistry, immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay (ELISA). The rats were divided into sham control, destabilization of the medial meniscus/AMD3100-treated (DMM/AMD3100-treated), and DMM/phosphate-buffered saline (PBS)-treated groups. After 6 weeks, the rats were euthanized and subjected to histological and immunohistochemical analyses. Also, interleukin (IL)-1-pretreated primary chondrocytes were cultured in the presence of empty control (−, −), CXCL12a (+,−), CXCL12a + small interfering RNA (siRNA) CXCR4 (+,+), or CXCL12a + siNC (+NC), and the expression levels of target markers were evaluated by Western blotting and real-time reverse transcription PCR (RT-PCR). The CXCL12/CXCR4 levels were higher, and the expression of TIMP-3 was lower, in the OA rats compared to the healthy control rats. The rats in the DMM/AMD3100-treated group revealed a markedly decreased immunological response and mild pathology. Treatment with CXCL12a increased expression of aggrecan and disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5) and suppressed that of TIMP-3 in IL-1-pretreated primary chondrocytes. TGF-β1 increased expression of TIMP-3, and this increase was reversed by CXCL12a via the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Moreover, these effects were inhibited by the CXCR4 antagonist AMD3100 and the PI3K inhibitor LY303511. In conclusion, inhibition of the CXCL12a/CXCR4 signaling axis maintained TIMP-3 expression via the PI3K/Akt pathway. Our findings provide insight into the mechanism by which AMD3100 prevents OA.

Muscle-derived SDF-1α/CXCL12 modulates endothelial cell proliferation but not exercise training-induced angiogenesis

Chemokines are critical mediators of angiogenesis in several physiological and pathological conditions; however, a potential role for muscle-derived chemokines in exercise-stimulated angiogenesis in skeletal muscle remains poorly understood. Here, we postulated that the chemokine stromal cell-derived factor-1 (SDF-1α/C-X-C motif chemokine ligand 12: CXCL12), shown to promote neovascularization in several organs, contributes to angiogenesis in skeletal muscle. We found that CXCL12 is abundantly expressed in capillary-rich oxidative soleus and exercise-trained plantaris muscles. CXCL12 mRNA and protein were also abundantly expressed in muscle-specific peroxisome proliferator-activated receptor γ coactivator 1α transgenic mice, which have a high proportion of oxidative muscle fibers and capillaries when compared with wild-type littermates. We then generated CXCL12 muscle-specific knockout mice but observed normal baseline capillary density and normal angiogenesis in these mice when they were exercise trained. To get further insight into a potential CXCL12 role in a myofiber-endothelial cell crosstalk, we first mechanically stretched C2C12 myotubes, a model known to induce stretch-related chemokine release, and observed increased CXCL12 mRNA and protein. Human umbilical vein endothelial cells (HUVECs) exposed to conditioned medium from cyclically stretched C2C12 myotubes displayed increased proliferation, which was dependent on CXCL12-mediated signaling through the CXCR4 receptor. However, HUVEC migration and tube formation were unaltered under these conditions. Collectively, our findings indicate that increased muscle contractile activity enhances CXCL12 production and release from muscle, potentially contributing to endothelial cell proliferation. However, redundant signals from other angiogenic factors are likely sufficient to sustain normal endothelial cell migration and tube formation activity, thereby preserving baseline capillary density and exercise training-mediated angiogenesis in muscles lacking CXCL12.

Islet Harvest in Carbon Monoxide-Saturated Medium for Chronic Pancreatitis Patients Undergoing Islet Autotransplantation

Stresses encountered during human islet isolation lead to unavoidable β-cell death after transplantation. This reduces the chance of insulin independence in chronic pancreatitis patients undergoing total pancreatectomy and islet autotransplantation. We tested whether harvesting islets in carbon monoxide-saturated solutions is safe and can enhance islet survival and insulin independence after total pancreatectomy and islet autotransplantation. Chronic pancreatitis patients who consented to the study were randomized into carbon monoxide (islets harvested in a carbon monoxide-saturated medium) or control (islets harvested in a normal medium) groups. Islet yield, viability, oxygen consumption rate, β-cell death (measured by unmethylated insulin DNA), and serum cytokine levels were measured during the peri-transplantation period. Adverse events, metabolic phenotypes, and islet function were measured prior and at 6 months post-transplantation. No adverse events directly related to the infusion of carbon monoxide islets were observed. Carbon monoxide islets showed significantly higher viability before transplantation. Subjects receiving carbon monoxide islets had less β-cell death, decreased CCL23, and increased CXCL12 levels at 1 or 3 days post transplantation compared with controls. Three in 10 (30%) of the carbon monoxide subjects and none of the control subjects were insulin independent. This pilot trial showed for the first time that harvesting human islets in carbon monoxide-saturated solutions is safe for total pancreatectomy and islet autotransplantation patients.

CCL2/MCP-1 and CXCL12/SDF-1 blockade by L-aptamers improve pancreatic islet engraftment and survival in mouse

The blockade of pro-inflammatory mediators is a successful approach to improve the engraftment after islet transplantation. L-aptamers are chemically synthesized, nonimmunogenic bio-stable oligonucleotides that bind and inhibit target molecules conceptually similar to antibodies. We aimed to evaluate if blockade-aptamer-based inhibitors of C-C Motif Chemokine Ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1) and C-X-C Motif Chemokine Ligand 12/stromal cell-derived factor-1 (CXCL12/SDF-1) are able to favor islet survival in mouse models for islet transplantation and for type 1 diabetes. We evaluated the efficacy of the CCL2-specific mNOX-E36 and the CXCL12-specific NOX-A12 on islet survival in a syngeneic mouse model of intraportal islet transplantation and in a multiple low doses of streptozotocin (MLD-STZ) diabetes induction model. Moreover, we characterized intrahepatic infiltrated leukocytes by flow cytometry before and 3 days after islet infusion in presence or absence of these inhibitors. The administration for 14 days of mNOX-E36 and NOX-A12 significantly improved islet engraftment, either compound alone or in combination. Intrahepatic islet transplantation recruited CD45⁺ leucocytes and more specifically CD45+/CD11b+ mono/macrophages; mNOX-E36 and NOX-A12 treatments significantly decreased the recruitment of inflammatory monocytes, CD11b⁺ /Ly6C^high /CCR2⁺ and CD11b⁺ /Ly6C^high /CXCR4⁺ cells, respectively. Additionally, both L-aptamers significantly attenuated diabetes progression in the MLD-STZ model. In conclusion, CCL2/MCP-1 and CXCL12/SDF-1 blockade by L-aptamers is an efficient strategy to improve islet engraftment and survival.

Immune cell trafficking to the islets during type 1 diabetes

Inhibition of immune cell trafficking to the pancreatic islets during type 1 diabetes (T1D) has therapeutic potential, since targeting of T cell and B cell trafficking has been clinically effective in other autoimmune diseases. Trafficking to the islets is characterized by redundancy in adhesion molecule and chemokine usage, which has not enabled effective targeting to date. Additionally, cognate antigen is not consistently required for T cell entry into the islets throughout the progression of disease. However, myeloid cells are required to enable T cell and B cell entry into the islets, and may serve as a convergence point in the pathways controlling this process. In this review we describe current knowledge of the factors that mediate immune cell trafficking to pancreatic islets during T1D progression.

SDF-1/CXCR4 axis facilitates myeloid-derived suppressor cells accumulation in osteosarcoma microenvironment and blunts the response to anti-PD-1 therapy

Immune checkpoint inhibitors, such as anti-PD-1/PD-L1, are a novel class of inhibitors that function as a tumor suppressing factor via modulation of immune cell-tumor cell interaction. To date, PD-1/PD-L1 inhibitors have been approved for the treatment of specific types of tumors and obtained good clinical efficacy. However, patients with osteosarcoma showed poor response to anti-PD-1/PD-L1 therapy, the mechanism of which is not well understood. In this study, we found that osteosarcoma tissues were heavily infiltrated by myeloid-derived suppressor cells (MDSCs) which could inhibit cytotoxicity T cell (CTL) expansion. Further study revealed that the vast majority of tumor-infiltrating MDSCs were CXCR4 positive and could migrate toward an SDF-1 gradient. The binding of SDF-1 to its receptor CXCR4 results in the activation of downstream AKT pathway that mediates reduced apoptosis of MDSCs. We also demonstrated that AMD3100, a CXCR4 antagonist, has a synergistic effect with anti-PD-1 antibody in tumor treatment in a murine model of osteosarcoma. These findings provide the basis for establishing CXCR4 antagonist and PD-1/PD-L1 inhibitors co-administration as a novel therapeutic regimen for patients with osteosarcoma and hold great promise for improving the therapeutic effect of osteosarcoma.

Alginate-microencapsulation of human stem cell-derived β cells with CXCL12 prolongs their survival and function in immunocompetent mice without systemic immunosuppression

Pancreatic β-cell replacement by islet transplantation for the treatment of type 1 diabetes (T1D) is currently limited by donor tissue scarcity and the requirement for lifelong immunosuppression. The advent of in vitro differentiation protocols for generating functional β-like cells from human pluripotent stem cells, also referred to as SC-β cells, could eliminate these obstacles. To avoid the need for immunosuppression, alginate-microencapsulation is widely investigated as a safe path to β-cell replacement. Nonetheless, inflammatory foreign body responses leading to pericapsular fibrotic overgrowth often causes microencapsulated islet-cell death and graft failure. Here we used a novel approach to evade the pericapsular fibrotic response to alginate-microencapsulated SC-β cells; an immunomodulatory chemokine, CXCL12, was incorporated into clinical grade sodium alginate to microencapsulate SC-β cells. CXCL12 enhanced glucose-stimulated insulin secretion activity of SC-β cells and induced expression of genes associated with β-cell function in vitro. SC-β cells co-encapsulated with CXCL12 showed enhanced insulin secretion in diabetic mice and accelerated the normalization of hyperglycemia. Additionally, SC-β cells co-encapsulated with CXCL12 evaded the pericapsular fibrotic response, resulting in long-term functional competence and glycemic correction (>150 days) without systemic immunosuppression in immunocompetent C57BL/6 mice. These findings lay the groundwork for further preclinical translation of this approach into large animal models of T1D.

CXCL12-CXCR4 pathway activates brown adipocytes and induces insulin resistance in CXCR4-deficient mice under high-fat diet

Brown adipose tissue (BAT) plays a role in energy expenditure and is involved in nutrient metabolism. C-X-C chemokine ligand 12 (CXCL12)-CXCR4 pathway regulates the immune, nervous, and cardiovascular systems and affects the adipose tissue. Here, we investigated the role of this pathway as an activator of BAT. Uncoupling protein 1 mRNA and protein levels and oxygen consumption increased in the brown adipocytes treated with 100 nM CXCL12 peptide. CXCL12-mediated upregulation in P38 and extracellular signal-regulated kinase (ERK) levels was reduced by each inhibitor. Thus, the CXCL12-CXCR4 pathway activated the brown adipocytes through P38 and ERK that acted downstream of this pathway. Mice with CXCR4 defects only in the brown adipocytes were generated and fed with high-fat diet (HFD). Body weight and blood glucose after glucose injection increased in these mice. Long-term exposure to HFD deteriorated blood glucose level after glucose injection. Insulin sensitivity was exacerbated in the knockout mice fed with HFD. Serum lipid parameters and CXCL12 level in knockout mice were similar to those in control mice. These results suggest that the CXCL12-CXCR4 pathway induces brown adipocyte activity and affects nutrient metabolism under HFD load.

Exocrine tissue-driven TFF2 prevents apoptotic cell death of endocrine lineage during pancreas organogenesis

During embryogenesis, exocrine and endocrine pancreatic tissues are formed in distinct regions within the branched ductal structure in mice. We previously reported that exocrine-specific inactivation of Pdx1 by Elastase-Cre caused not only hypoplastic exocrine formation but also substantial endocrine defects resulting in diabetic phenotype, indicating the existence of an exocrine-driven factor(s) that regulates proper endocrine development. In this study, we identified Trefoil Factor 2 (TFF2) as an exocrine gene expressed from embryonic day 16.5 to adulthood in normal mice but significantly less in our Pdx1 mutants. Using in vitro explant culture of embryonic pancreatic tissue, we demonstrated that TFF2 prevented the apoptosis of insulin-producing cells but that antagonizing CXCR4, a known TFF2 receptor, suppressed this anti-apoptotic effect in the mutants. Furthermore, the antagonist in normal pancreatic tissue accelerated the apoptosis of insulin-producing cells, indicating that the TFF2/CXCR4 axis maintains embryonic insulin-producing cells in normal development. TFF2 also suppressed the apoptosis of Nkx6.1+ endocrine precursors in mutant pancreata, but this effect was unperturbed by the CXCR4 antagonist, suggesting the existence of an unknown receptor for TFF2. These findings suggest TFF2 is a novel exocrine factor that supports the survival of endocrine cells in the multiple stages of organogenesis through distinct receptors.

Absence of PARP-1 affects Cxcl12 expression by increasing DNA demethylation

Poly [ADP‐ribose] polymerase 1 (PARP‐1) has an inhibitory effect on C‐X‐C motif chemokine 12 gene (Cxcl12) transcription. We examined whether PARP‐1 affects the epigenetic control of Cxcl12 expression by changing its DNA methylation pattern. We observed increased expression of Cxcl12 in PARP‐1 knock‐out mouse embryonic fibroblasts (PARP1−/−) in comparison to wild‐type mouse embryonic fibroblasts (NIH3T3). In the Cxcl12 gene, a CpG island is present in the promoter, the 5′ untranslated region (5′ UTR), the first exon and in the first intron. The methylation state of Cxcl12 in each cell line was investigated by methylation‐specific PCR (MSP) and high resolution melting analysis (HRM). Both methods revealed strong demethylation in PARP1−/− compared to NIH3T3 cells in all four DNA regions. Increased expression of the Ten‐eleven translocation (Tet) genes in PARP1−/− cells indicated that TETs could be important factors in Cxcl12 demethylation in the absence of PARP‐1, accounting for its increased expression. Our results showed that PARP‐1 was a potential upstream player in (de)methylation events that modulated Cxcl12 expression.

Physiology and Pharmacology of DPP-4 in Glucose Homeostasis and the Treatment of Type 2 Diabetes

Dipeptidyl peptidase-4 (DPP-4), also known as the T-cell antigen CD26, is a multi-functional protein which, besides its catalytic activity, also functions as a binding protein and a ligand for a variety of extracellular molecules. It is an integral membrane protein expressed on cells throughout the body, but is also shed from the membrane and circulates as a soluble protein in the plasma. A large number of bioactive molecules can be cleaved by DPP-4 in vitro, but only a few of these have been demonstrated to be physiological substrates. One of these is the incretin hormone, glucagon-like peptide-1 (GLP-1), which plays an important role in the maintenance of normal glucose homeostasis, and DPP-4 has been shown to be the key enzyme regulating its biological activity. This pathway has been targeted pharmacologically through the development of DPP-4 inhibitors, and these are now a successful class of anti-hyperglycaemic agents used to treat type 2 diabetes (T2DM). DPP-4 may additionally influence metabolic control via its proteolytic effect on other regulatory peptides, but it has also been reported to affect insulin sensitivity, potentially mediated through its non-enzymatic interactions with other membrane proteins. Given that altered expression and activity of DPP-4 are associated with increasing body mass index and hyperglycaemia, DPP-4 has been proposed to play a role in linking obesity and the pathogenesis of T2DM by functioning as a local mediator of inflammation and insulin resistance in adipose and hepatic tissue. As well as these broader systemic effects, it has also been suggested that DPP-4 may be able to modulate β-cell function as part of a paracrine system involving GLP-1 produced locally within the pancreatic islets. However, while it is evident that DPP-4 has the potential to influence glycaemic control, its overall significance for the normal physiological regulation of glucose homeostasis in humans and its role in the pathogenesis of metabolic disease remain to be established.

Genes and transcription factors related to the adverse effects of maternal type I diabetes mellitus on fetal development

PURPOSE

Maternal type I diabetes mellitus (T1DM) increases the risk of adverse pregnancy outcomes, but the corresponding mechanism is unclear. This study aims to investigate the mechanism underlying the adverse pregnancy outcomes of maternal T1DM.

METHODS

Gene expression microarray (GSE51546) was down-loaded from the Gene Expression Omnibus. This dataset included 12 umbilical cord samples from the newborns of T1DM mothers (T1DM group, N = six) and non-diabetic mothers (control group, N = six).

RESULTS

Consequently, 1051 differentially expressed genes (DEGs) were found between the two groups. The up-regulated DEGs enriched in 30 KEGG pathways. HLA-DPA1, HLA-DMA, HLA-DMB, HLA-DQA1, HLA-DQA2 and HLA-DRA enriched in "Type I diabetes mellitus". This pathway was strongly related to 14 pathways, most of which were associated with diseases. Then, a protein-protein interaction network was constructed, and 45 potential key DEGs were identified. The 45 DEGs enriched in pathways such as "Rheumatoid arthritis", "Chemokine signaling pathway" and "Cytokine-cytokine receptor interaction" (e.g. CXCL12 and CCL5). Transcription factors (TFs) of key DEGs were predicted, and a TF-DEG regulatory network was constructed.

CONCLUSIONS

Some genes (e.g. CXCL12 and CCL5) and their TFs were significantly and abnormally regulated in the umbilical cord tissue from the pregnancies of T1DM mothers compared to that from non-T1DM mothers.

Mesenchymal stromal cell secretory factors induce sustained improvements in islet function pre- and post-transplantation

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) enhance islet function both in vitro and in vivo, at least in part by secreting ligands that activate islet G-protein coupled receptors (GPCRs). We assessed whether pre-treatment with a defined "cocktail" of MSC-secreted GPCR ligands enhances islet functional survival in vitro and improves the outcomes of islet transplantation in an experimental model of diabetes.

METHODS

Isolated islets were cultured for 48 h with ANXA1, SDF-1 or C3a, alone or in combination. Glucose-stimulated insulin secretion (GSIS) and cytokine-induced apoptosis were measured immediately after the 48 h culture period and at 24 h or 72 h following removal of the ligands from the culture media. Islets were syngeneically transplanted underneath the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice and blood glucose levels monitored for 28 days.

RESULTS

Pre-culturing islets with a cocktail of ANXA1/SDF-1/C3a potentiated GSIS and protected islet cells from cytokine-induced apoptosis in vitro. These effects were maintained for up to 72 h after the removal of the factors from the culture medium, suggesting a sustained protection of islet graft functional survival during the immediate post-transplantation period. Islets pre-treated with the cocktail of MSC secretory factors were more effective in reducing blood glucose in diabetic mice, consistent with their improved functional survival in vivo.

DISCUSSION

Pre-culturing islets with a cocktail of MSC secretory products offers a well-defined, cell-free approach to improve clinical islet transplantation outcomes while avoiding many of the safety, regulatory and logistical hurdles of incorporating MSCs into transplantation protocols.

BH3 mimetics suppress CXCL12 expression in human malignant peripheral nerve sheath tumor cells

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, Schwann cell-derived neoplasms of the peripheral nervous system that have recently been shown to possess an autocrine CXCL12/CXCR4 signaling loop that promotes tumor cell proliferation and survival. Importantly, the CXCL12/CXCR4 signaling axis is driven by availability of the CXCL12 ligand rather than CXCR4 receptor levels alone. Therefore, pharmacological reduction of CXCL12 expression could be a potential chemotherapeutic target for patients with MPNSTs or other pathologies wherein the CXCL12/CXCR4 signaling axis is active. AT101 is a well-established BCL-2 homology domain 3 (BH3) mimetic that we recently demonstrated functions as an iron chelator and thus acts as a hypoxia mimetic. In this study, we found that AT101 significantly reduces CXCL12 mRNA and secreted protein in established human MPNST cell lines in vitro. This effect was recapitulated by other BH3 mimetics [ABT-737 (ABT), obatoclax (OBX) and sabutoclax (SBX)] but not by desferrioxamine (DFO), an iron chelator and known hypoxia mimetic. These data suggest that CXCL12 reduction is a function of AT101's BH3 mimetic property rather than its iron chelation ability. Additionally, this study investigates a potential mechanism of BH3 mimetic-mediated CXCL12 suppression: liberation of a negative CXCL12 transcriptional regulator, poly (ADP-Ribose) polymerase I (PARP1) from its physical interaction with BCL-2. These data suggest that clinically available BH3 mimetics might prove therapeutically useful at least in part by virtue of their ability to suppress CXCL12 expression.

An Integrated View of Immunometabolism

The worldwide obesity epidemic has emerged as a major cause of insulin resistance and Type 2 diabetes. Chronic tissue inflammation is a well-recognized feature of obesity, and the field of immunometabolism has witnessed many advances in recent years. Here, we review the major features of our current understanding with respect to chronic obesity-related inflammation in metabolic tissues and focus on how these inflammatory changes affect insulin sensitivity, insulin secretion, food intake, and glucose homeostasis. There is a growing appreciation of the varied and sometimes integrated crosstalk between cells within a tissue (intraorgan) and tissues within an organism (interorgan) that supports inflammation in the context of metabolic dysregulation. Understanding these pathways and modes of communication has implications for translational studies. We also briefly summarize the state of this field with respect to potential current and developing therapeutics.

Saxagliptin Attenuates Albuminuria by Inhibiting Podocyte Epithelial- to-Mesenchymal Transition via SDF-1α in Diabetic Nephropathy

The dipeptidyl peptidase-4 (DPP-4) inhibitor saxagliptin has been found to reduce progressive albuminuria, but the exact mechanism of inhibition is unclear. Podocyte epithelial-to-mesenchymal transition (EMT) has emerged as a potential pathway leading to proteinuria in diabetic nephropathy (DN). Stromal cell–derived factor-1α (SDF-1α), one of the substrates of DPP-4, can activate the protein kinase A pathway and subsequently inhibit its downstream effector, transforming growth factor-β1 (TGF-β1), which induces podocyte EMT. Thus, this study was designed to test the hypothesis that saxagliptin reduces progressive albuminuria by preventing podocyte EMT through inhibition of SDF-1α cleavage in DN. The results of a series of assays, including ELISA, western blotting, and immunochemistry/immunofluorescence, showed that saxagliptin treatment obviously ameliorated urinary microalbumin excretion and renal histological changes in high-fat diet/streptozotocin-induced diabetic rats. Furthermore, saxagliptin-treated diabetic rats presented with suppression of DPP-4 activity/protein expression accompanied by restoration of SDF-1α levels, which subsequently hindered NOX2 expression and podocyte EMT. In vitro, we consistently observed that saxagliptin significantly inhibited increased DPP-4 activity/expression, oxidative stress and podocyte EMT. Application of an SDF-1α receptor inhibitor (AMD3100) to cultured podocytes further confirmed the essential role of SDF-1α in podocyte EMT inhibition. In sum, we demonstrated for the first time that saxagliptin treatment plays an essential role in ameliorating progressive DN by preventing podocyte EMT through a SDF-1α-related pathway, suggesting that saxagliptin could offer renoprotection and that SDF-1α might be a potential therapeutic target for DN.

Proteomic characterisation reveals active Wnt-signalling by human multipotent stromal cells as a key regulator of beta cell survival and proliferation

AIMS/HYPOTHESIS

Novel strategies to stimulate the expansion of beta cell mass in situ are warranted for diabetes therapy. The aim of this study was to elucidate the secretome of human bone marrow (BM)-derived multipotent stromal cells (MSCs) with documented islet regenerative paracrine function. We hypothesised that regenerative MSCs will secrete a unique combination of protein factors that augment islet regeneration.

METHODS

Human BM-derived MSCs were examined for glucose-lowering capacity after transplantation into streptozotocin-treated NOD/severe combined immunodeficiency (SCID) mice and segregated into samples with regenerative (MSC^R) vs nonregenerative (MSC^NR) capacity. Secreted proteins associated with islet regenerative function were identified using stable isotope labelling with amino acids in cell culture (SILAC)-based quantitative proteomics. To functionally validate the importance of active Wnt signalling, we stimulated the Wnt-signalling pathway in MSC^NR samples during ex vivo expansion using glycogen synthase kinase 3 (GSK3) inhibition (CHIR99201), and the conditioned culture media (CM) generated was tested for the capacity to support cultured human islet cell survival and proliferation in vitro.

RESULTS

MSC^R showed increased secretion of proteins associated with cell growth, matrix remodelling, immunosuppressive and proangiogenic properties. In contrast, MSC^NR uniquely secreted proteins known to promote inflammation and negatively regulate angiogenesis. Most notably, MSC^R maintained Wnt signalling via Wnt5A/B (~2.5-fold increase) autocrine activity during ex vivo culture, while MSC^NR repressed Wnt signalling via Dickkopf-related protein (DKK)1 (~2.5-fold increase) and DKK3 secretion. Inhibition of GSK3 activity in MSC^NR samples increased the accumulation of nuclear β-catenin and generated CM that augmented beta cell survival (13% increases) and proliferation when exposed to cultured human islets.

CONCLUSIONS/INTERPRETATION

Maintenance of active Wnt signalling within human MSCs promotes the secretion of matricellular and proangiogenic proteins that formulate a niche for islet regeneration.

Transplantation of stromal-derived factor 1α and basic fibroblast growth factor primed insulin-producing cells reverses hyperglycaemia in diabetic rats

The defective insulin production is associated with severely reduced islet cell mass leading to diabetes. Growth factors preconditioned stem cells have arisen as an effective therapy to treat many diseases including diabetes. The current study was designed to assess the effect of pretreatment of ASCs derived IPCs with combination of stromal cell derived factor 1 alpha (SDF1α) and basic fibroblast growth factor (bFGF) in improving glucose tolerance in streptozotocin induced diabetic rats. The results showed maximally significant reduction in hyperglycaemia and fibrosis, while up-regulation of survival and pancreas-specific genes, insulin levels and homing of transplanted cells in SDF-1α + bFGF IPCs transplanted rats as compared with other groups. Moreover, increased expression of insulin, glucagon and Glut-2 in pancreas of the SDF-1α + bFGF IPCs transplanted group indicated more regeneration of pancreas. Hence, the use of IPCs preconditioned with SDF-1α + bFGF would be more effective for treating diabetes.

RNA Sequencing Exposes Adaptive and Immune Responses to Intrauterine Growth Restriction in Fetal Sheep Islets

The risk of type 2 diabetes is increased in children and adults who exhibited fetal growth restriction. Placental insufficiency and intrauterine growth restriction (IUGR) are common obstetrical complications associated with fetal hypoglycemia and hypoxia that reduce the β-cell mass and insulin secretion. In the present study, we have defined the underlying mechanisms of reduced growth and proliferation, impaired metabolism, and defective insulin secretion previously established as complications in islets from IUGR fetuses. In an IUGR sheep model that recapitulates human IUGR, high-throughput RNA sequencing showed the transcriptome of islets isolated from IUGR and control sheep fetuses and identified the transcripts that underlie β-cell dysfunction. Functional analysis expanded mechanisms involved in reduced proliferation and dysregulated metabolism that include specific cell cycle regulators and growth factors and mitochondrial, antioxidant, and exocytotic genes. These data also identified immune responses, wnt signaling, adaptive stress responses, and the proteasome as mechanisms of β-cell dysfunction. The reduction of immune-related gene expression did not reflect a change in macrophage density within IUGR islets. The present study reports the islet transcriptome in fetal sheep and established processes that limit insulin secretion and β-cell growth in fetuses with IUGR, which could explain the susceptibility to premature islet failure in adulthood. Islet dysfunction formed by intrauterine growth restriction increases the risk for diabetes.

Saxagliptin Induces β-Cell Proliferation through Increasing Stromal Cell-Derived Factor-1α In Vivo and In Vitro

Dipeptidyl peptidase-4 inhibitors, such as saxagliptin, have been reported to have beneficial effects on β-cell function, but the specific underlying mechanism remains unclear. Stromal cell-derived factor-1α (SDF-1α), a chemokine produced in multiple organs, has been considered as a crucial regulator in promoting β-cell survival. Here, we speculate that SDF-1α might mediate the effect of saxagliptin on improving β-cell function. After 12-week saxagliptin treatment in high-fat diet/streptozotocin-induced diabetic rats, significant improvement in pancreas insulin secretion capacity evaluated by hyperglycemia clamp and increased β-cell to α-cell areas ratio were observed. Saxagliptin significantly induced β-cell proliferation and upregulated the expression of proliferation-related factors including c-myc and cyclind D1 determined with western blotting from the isolated islets. The expression/activity of DPP-4 was significantly reduced and paralleled with the restoration of SDF-1α levels in the saxagliptin-treated diabetic rats, subsequently the key WNT-signaling regulators, β-catenin, and AKT were activated. However, the effect of saxagliptin inducing β-cell proliferation was attenuated when we silenced the SDF-1α receptor (CXCR4) with RNAi in INS cell lines. Collectively, our data indicate that SDF-1α mediates the protective effect of saxagliptin on β-cell proliferation, suggesting that DPP-4 inhibitors have the potential role on delaying β-cell failure and SDF-1α could be a therapeutic target of β-cell regeneration.

Short-term high-fat feeding induces islet macrophage infiltration and β-cell replication independently of insulin resistance in mice

Short-term high-fat consumption stimulates mouse islet β-cell replication through unknown mechanisms. Resident macrophages (MΦs) are capable of secreting various factors involved in islet development and tissue remodeling. We hypothesized that a short-term high-fat diet (HFD) promotes MΦ infiltration in pancreatic islets and that MΦs serve as a regulator of β-cell replication. To test these hypotheses and dissect mechanisms involved in HFD-induced β-cell replication, adult C57BL/6J mice were fed a HFD for 7 days with or without administration of clodronate-containing liposomes, an MΦ-depleting agent. Mouse body and epididymal fat pad weights, and nonfasting blood glucose and fasting serum insulin levels were measured, and pancreatic islet β-cell replication, oxidative stress, and MΦ infiltration were examined. Short-term HFD promoted an increase in body and epididymal fat pad weight and blood glucose levels, along with an increased fasting serum insulin concentration. β-Cell replication, islet MΦ infiltration, and the percentage of inducible NO synthase positive MΦs in the islets increased significantly in mice fed the HFD. Immunofluorescence staining for 8-oxo-2'-deoxyguanosine or activated caspase-3 revealed no significant induction of DNA damage or apoptosis, respectively. In addition, no change in stromal-derived factor 1-expressing cells was found induced by HFD. Despite continuous elevation of nonfasting blood glucose and fasting serum insulin levels, depletion of MΦs through treatments of clodronate abrogated HFD-induced β-cell replication. These findings demonstrated that HFD-induced MΦ infiltration is responsible for β-cell replication. This study suggests the existence of MΦ-mediated mechanisms in β-cell replication that are independent of insulin resistance.

Stromal cell-derived factor-1 is upregulated by dipeptidyl peptidase-4 inhibition and has protective roles in progressive diabetic nephropathy

The role of stromal cell-derived factor-1 (SDF-1) in the pathogenesis of diabetic nephropathy and its modification by dipeptidyl peptidase-4 (DPP-4) inhibition are uncertain. Therefore, we studied this independent of glucagon-like peptide-1 receptor (GLP-1R) signaling using two Akita diabetic mouse models, the diabetic-resistant C57BL/6-Akita and diabetic-prone KK/Ta-Akita. Increased SDF-1 expression was found in glomerular podocytes and distal nephrons in the diabetic-prone mice, but not in kidneys from diabetic-resistant mice. The DPP-4 inhibitor linagliptin, but not the GLP-1R agonist liraglutide, further augmented renal SDF-1 expression in both Glp1r(+/+) and Glp1r(-/-) diabetic-prone mice. Along with upregulation of renal SDF-1 expression, the progression of albuminuria, glomerulosclerosis, periglomerular fibrosis, podocyte loss, and renal oxidative stress was suppressed in linagliptin-treated Glp1r(+/+) diabetic-prone mice. Linagliptin treatment increased urinary sodium excretion and attenuated the increase in glomerular filtration rate which reflects glomerular hypertension and hyperfiltration. In contrast, selective SDF-1 receptor blockade with AMD3100 reduced urinary sodium excretion and aggravated glomerular hypertension in the Glp1r(+/+) diabetic-prone mice. Thus, DPP-4 inhibition, independent of GLP-1R signaling, contributes to protection of the diabetic kidney through SDF-1-dependent antioxidative and antifibrotic effects and amelioration of adverse renal hemodynamics.

Effectiveness of AMD3100 in treatment of leukemia and solid tumors: from original discovery to use in current clinical practice

AMD3100, also known as plerixafor, was originally developed as an anti-human immunodeficiency virus (HIV) drug, and later characterized as a C-X-C chemokine receptor type 4 (CXCR4) antagonist. Previous reviews have focused on the application of AMD3100 in the treatment of HIV, but a comprehensive evaluation of AMD3100 in the treatment of leukemia, solid tumor, and diagnosis is lacking. In this review, we broadly describe AMD3100, including the background, functional mechanism and clinical applications. Until the late 1990s, CXCR4 was known as a crucial factor for hematopoietic stem and progenitor cell (HSPC) retention in bone marrow. Subsequently, the action and synergy of plerixafor with Granulocyte-colony stimulating factor (G-CSF) led to the clinical approval of plerixafor as the first compound for mobilization of HSPCs. The amount of HSPC mobilization and the rapid kinetics promoted additional clinical uses. Recently, CXCR4/CXCL12 (C-X-C motif chemokine 12) axis was found to be involved in a variety of roles in tumors, including leukemic stem cell (LSC) homing and signaling transduction. Thus, CXCR4 targeting has been a treatment strategy against leukemia and solid tumors. Understanding this mechanism will help shed light on therapeutic potential for HIV infection, inflammatory diseases, stem-cell mobilization, leukemia, and solid tumors. Clarifying the CXCR4/CXCL12 axis and role of AMD3100 will help remove malignant cells from the bone marrow niche, rendering them more accessible to targeted therapeutic agents.

Anti-Inflammatory Effects of Metformin Irrespective of Diabetes Status

Supplemental Digital Content is available in the text.

Rationale:

The diabetes mellitus drug metformin is under investigation in cardiovascular disease, but the molecular mechanisms underlying possible benefits are poorly understood.

Objective:

Here, we have studied anti-inflammatory effects of the drug and their relationship to antihyperglycemic properties.

Methods and Results:

In primary hepatocytes from healthy animals, metformin and the IKKβ (inhibitor of kappa B kinase) inhibitor BI605906 both inhibited tumor necrosis factor-α–dependent IκB degradation and expression of proinflammatory mediators interleukin-6, interleukin-1β, and CXCL1/2 (C-X-C motif ligand 1/2). Metformin suppressed IKKα/β activation, an effect that could be separated from some metabolic actions, in that BI605906 did not mimic effects of metformin on lipogenic gene expression, glucose production, and AMP-activated protein kinase activation. Equally AMP-activated protein kinase was not required either for mitochondrial suppression of IκB degradation. Consistent with discrete anti-inflammatory actions, in macrophages, metformin specifically blunted secretion of proinflammatory cytokines, without inhibiting M1/M2 differentiation or activation. In a large treatment naive diabetes mellitus population cohort, we observed differences in the systemic inflammation marker, neutrophil to lymphocyte ratio, after incident treatment with either metformin or sulfonylurea monotherapy. Compared with sulfonylurea exposure, metformin reduced the mean log-transformed neutrophil to lymphocyte ratio after 8 to 16 months by 0.09 U (95% confidence interval, 0.02–0.17; P=0.013) and increased the likelihood that neutrophil to lymphocyte ratio would be lower than baseline after 8 to 16 months (odds ratio, 1.83; 95% confidence interval, 1.22–2.75; P=0.00364). Following up these findings in a double-blind placebo controlled trial in nondiabetic heart failure (trial registration: NCT00473876), metformin suppressed plasma cytokines including the aging-associated cytokine CCL11 (C-C motif chemokine ligand 11).

Conclusion:

We conclude that anti-inflammatory properties of metformin are exerted irrespective of diabetes mellitus status. This may accelerate investigation of drug utility in nondiabetic cardiovascular disease groups.

Clinical Trial Registration:

Name of the trial registry: TAYSIDE trial (Metformin in Insulin Resistant Left Ventricular [LV] Dysfunction). URL: https://www.clinicaltrials.gov. Unique identifier: NCT00473876.

Myocardial Ischemia Induces SDF-1α Release in Cardiac Surgery Patients

In the present observational study, we measured serum levels of the chemokine stromal cell-derived factor-1α (SDF-1α) in 100 patients undergoing cardiac surgery with cardiopulmonary bypass at seven distinct time points including preoperative values, myocardial ischemia, reperfusion, and the postoperative course. Myocardial ischemia triggered a marked increase of SDF-1α serum levels whereas cardiac reperfusion had no significant influence. Perioperative SDF-1α serum levels were influenced by patients' characteristics (e.g., age, gender, aspirin intake). In an explorative analysis, we observed an inverse association between SDF-1α serum levels and the incidence of organ dysfunction. In conclusion, time of myocardial ischemia was identified as the key stimulus for a significant upregulation of SDF-1α, indicating its role as a marker of myocardial injury. The inverse association between SDF-1α levels and organ dysfunction association encourages further studies to evaluate its organoprotective properties in cardiac surgery patients.

Hexarelin Protects Rodent Pancreatic Β-Cells Function from Cytotoxic Effects of Streptozotocin Involving Mitochondrial Signalling Pathways In Vivo and In Vitro

Mitochondrial functions are crucial for pancreatic β-cell survival and glucose-induced insulin secretion. Hexarelin (Hex) is a synthetic small peptide ghrelin analogue, which has been shown to protect cardiomyocytes from the ischemia-reperfusion process. In this study, we used in vitro and in vivo models of streptozotocin (STZ)-induced β-cell damage to study the protective effect of Hex and the associated mechanisms. We found that STZ produced a cytotoxic effect in a dose- and time-dependent manner in MIN6 cells (a mouse β-cell line). Hex (1.0 μM) decreased the STZ-induced damage in β-cells. Rhodamine 123 assay and superoxide DHE production assay revealed that Hex ameliorated STZ-induced mitochondrial damage and excessive superoxide activity in β-cells. In addition, Hex significantly reduced STZ-induced expression of cleaved Caspases-3, Caspases-9 and the ratio of pro-apoptotic protein Bax to anti-apoptotic protein Bcl-2 in MIN6 cells. We further examined the in vivo effect of Hex in a rat model of type 1 diabetes induced by STZ injection. Hex ameliorated STZ-induced decrease in plasma insulin and protected the structure of islets from STZ-induced disruption. Hex also ameliorated STZ-induced expression of cleaved Caspase-9 and the Bax in β-cells. In conclusion, our data indicate that Hex is able to protects β-cell mass from STZ-caused cytotoxic effects involving mitochondrial pathways in vitro and in vivo. Hex may serve as a potential protective agent for the management of diabetes.

Redifferentiation of expanded human islet β cells by inhibition of ARX

Ex-vivo expansion of adult human islet β cells has been evaluated for generation of abundant insulin-producing cells for transplantation; however, lineage-tracing has demonstrated that this process results in β-cell dedifferentiation. Redifferentiation of β-cell-derived (BCD) cells can be achieved using a combination of soluble factors termed Redifferentiation Cocktail (RC); however, this treatment leads to redifferentiation of only a fraction of BCD cells. This study aimed at improving redifferentiation efficiency by affecting the balance of islet progenitor-cell transcription factors activated by RC treatment. Specifically, RC treatment induces the transcription factors PAX4 and ARX, which play key roles in directing pancreas endocrine progenitor cells into the β/δ or α/PP developmental pathways, respectively. Misactivation of ARX in RC-treated BCD cells may inhibit their redifferentiation into β cells. Blocking ARX expression by shRNA elevated insulin mRNA levels 12.8-fold, and more than doubled the number of insulin-positive BCD cells. ARX inhibition in expanded α-cell-derived cells treated with RC did not cause their transdifferentiation into insulin-producing cells. The combination of RC and ARX shRNA treatment may facilitate the generation of abundant insulin-producing cells for transplantation into patients with type 1 diabetes.

CXCL12 protects pancreatic β-cells from oxidative stress by a Nrf2-induced increase in catalase expression and activity

Due to intrinsically low levels of antioxidant enzyme expression and activity, insulin producing pancreatic β-cells are particularly susceptible to free radical attack. In diabetes mellitus, which is accompanied by high levels of oxidative stress, this feature of β-cells significantly contributes to their damage and dysfunction. In light of the documented pro-survival effect of chemokine C-X-C Ligand 12 (CXCL12) on pancreatic β-cells, we examined its potential role in antioxidant protection. We report that CXCL12 overexpression enhanced the resistance of rat insulinoma (Rin-5F) and primary pancreatic islet cells to hydrogen peroxide (H₂O₂). CXCL12 lowered the levels of DNA damage and lipid peroxidation and preserved insulin expression. This effect was mediated through an increase in catalase (CAT) activity. By activating downstream p38, Akt and ERK kinases, CXCL12 facilitated Nrf2 nuclear translocation and enhanced its binding to the CAT gene promoter, inducing constitutive CAT expression and activity that was essential for protecting β-cells from H₂O₂.

Annexin A1 Is a Key Modulator of Mesenchymal Stromal Cell-Mediated Improvements in Islet Function

We have previously demonstrated that coculture of islets with mesenchymal stromal cells (MSCs) enhanced islet insulin secretory capacity in vitro, correlating with improved graft function in vivo. To identify factors that contribute to MSC-mediated improvements in islet function, we have used an unbiased quantitative RT-PCR screening approach to identify MSC-derived peptide ligands of G-protein-coupled receptors that are expressed by islets cells. We demonstrated high expression of annexin A1 (ANXA1) mRNA by MSCs and confirmed expression at the protein level in lysates and MSC-conditioned media by Western blot analysis and ELISA. Preculturing islets with exogenous ANXA1 enhanced glucose-stimulated insulin secretion (GSIS), thereby mimicking the beneficial influence of MSC preculture in vitro. Small interfering RNA-mediated knockdown of ANXA1 in MSCs reduced their capacity to potentiate GSIS. MSCs derived from ANXA1(-/-) mice had no functional capacity to enhance GSIS, in contrast to wild-type controls. Preculturing islets with ANXA1 had modest effects on their capacity to regulate blood glucose in streptozotocin-induced diabetic mice, indicating that additional MSC-derived factors are required to fully mimic the beneficial effects of MSC preculture in vivo. These findings demonstrate the feasibility of harnessing the MSC secretome as a defined, noncellular strategy to improve the efficiency of clinical islet transplantation protocols.

Administration of a CXCL12 Analog in Endotoxemia Is Associated with Anti-Inflammatory, Anti-Oxidative and Cytoprotective Effects In Vivo

Background

The chemokine receptor CXCR4 is a multifunctional receptor which is activated by its natural ligand C-X-C motif chemokine 12 (CXCL12). As CXCR4 is part of the lipopolysaccharide sensing complex and CXCL12 analogs are not well characterized in inflammation, we aimed to uncover the systemic effects of a CXCL12 analog in severe systemic inflammation and to evaluate its impact on endotoxin induced organ damages by using a sublethal LPS dose.

Methods

The plasma stable CXCL12 analog CTCE-0214D was synthesized and administered subcutaneously shortly before LPS treatment. After 24 hours, mice were sacrificed and blood was obtained for TNF alpha, IFN gamma and blood glucose evaluation. Oxidative stress in the liver and spleen was assessed and liver biotransformation capacity was determined. Finally, CXCR4, CXCL12 and TLR4 expression patterns in liver, spleen and thymus tissue as well as the presence of different markers for apoptosis and oxidative stress were determined by means of immunohistochemistry.

Results

CTCE-0214D distinctly reduced the LPS mediated effects on TNF alpha, IFN gamma, ALAT and blood glucose levels. It attenuated oxidative stress in the liver and spleen tissue and enhanced liver biotransformation capacity unambiguously. Furthermore, in all three organs investigated, CTCE-0214D diminished the LPS induced expression of CXCR4, CXCL12, TLR4, NF-κB, cleaved caspase-3 and gp91 phox, whereas heme oxygenase 1 expression and activity was induced above average. Additionally, TUNEL staining revealed anti-apoptotic effects of CTCE-0214D.

Conclusions

In summary, CTCE-0214D displayed anti-inflammatory, anti-oxidative and cytoprotective features. It attenuated reactive oxygen species, induced heme oxygenase 1 activity and mitigated apoptosis. Thus, the CXCR4/CXCL12 axis seems to be a promising target in the treatment of acute systemic inflammation, especially when accompanied by a hepatic dysfunction and an excessive production of free radicals.

A genetic mouse model for progressive ablation and regeneration of insulin producing beta-cells

The putative induction of adult β-cell regeneration represents a promising approach for the treatment of type 1 diabetes. Toward this ultimate goal, it is essential to develop an inducible model mimicking the long-lasting disease progression. In the current study, we have established a novel β-cell ablation mouse model, in which the β-cell mass progressively declines, as seen in type 1 diabetes. The model is based on the β-cell specific genetic ablation of the transcription initiation factor 1A, TIF-IA, essential for RNA Polymerase I activity (TIF-IA(Δ/Δ)). Using this approach, we induced a slow apoptotic response that eventually leads to a protracted β-cell death. In this model, we observed β-cell regeneration that resulted in a complete recovery of the β-cell mass and normoglycemia. In addition, we showed that adaptive proliferation of remaining β-cells is the prominent mechanism acting to compensate for the massive β-cell loss in young but also aged mice. Interestingly, at any age, we also detected β-like cells expressing the glucagon hormone, suggesting a transition between α- and β-cell identities or vice versa. Taken together, the TIF-IA(Δ/Δ) mouse model can be used to investigate the potential therapeutic approaches for type 1 diabetes targeting β-cell regeneration.

The Importance of the CXCL12/CXCR4 Axis in Therapeutic Approaches to Diabetes Mellitus Attenuation

The pleiotropic chemokine (C–X–C motif) ligand 12 (CXCL12) has emerged as a crucial player in several diseases. The role of CXCL12 in diabetes promotion and progression remains elusive due to its multiple functions and the overwhelming complexity of diabetes. Diabetes is a metabolic disorder resulting from a failure in glucose regulation due to β-cell loss and/or dysfunction. In view of its ability to stimulate the regeneration, proliferation, and survival of β-cells, as well as its capacity to sustain local immune-isolation, CXCL12 has been considered in approaches aimed at attenuating type 1 diabetes. However, a note of caution emerges from examinations of the involvement of CXCL12 in the development of diabetes and its complications, as research data indicate that CXCL12 displays effects that range from protective to detrimental. Therefore, as a beneficial effect of CXCL12 in one process could have deleterious consequences in another, a more complete understanding of CXCL12 effects, in particular its functioning in the cellular microenvironment, is essential before CXCL12 can be considered in therapies for diabetes treatment.

Improving pancreatic islet in vitro functionality and transplantation efficiency by using heparin mimetic peptide nanofiber gels

Pancreatic islet transplantation is a promising treatment for type 1 diabetes. However, viability and functionality of the islets after transplantation are limited due to loss of integrity and destruction of blood vessel networks. Thus, it is important to provide a proper mechanically and biologically supportive environment for enhancing both in vitro islet culture and transplantation efficiency. Here, we demonstrate that heparin mimetic peptide amphiphile (HM-PA) nanofibrous network is a promising platform for these purposes. The islets cultured with peptide nanofiber gel containing growth factors exhibited a similar glucose stimulation index as that of the freshly isolated islets even after 7 days. After transplantation of islets to STZ-induced diabetic rats, 28 day-long monitoring displayed that islets that were transplanted in HM-PA nanofiber gels maintained better blood glucose levels at normal levels compared to the only islet transplantation group. In addition, intraperitoneal glucose tolerance test revealed that animals that were transplanted with islets within peptide gels showed a similar pattern with the healthy control group. Histological assessment showed that islets transplanted within peptide nanofiber gels demonstrated better islet integrity due to increased blood vessel density. This work demonstrates that using the HM-PA nanofiber gel platform enhances the islets function and islet transplantation efficiency both in vitro and in vivo.