Oxidative stress plays a pivotal role in the development of diabetes complications, both microvascular and cardiovascular. The metabolic abnormalities of diabetes cause mitochondrial superoxide overproduction in endothelial cells of both large and small vessels, as well as in the myocardium. This increased superoxide production causes the activation of 5 major pathways involved in the pathogenesis of complications: polyol pathway flux, increased formation of AGEs (advanced glycation end products), increased expression of the receptor for AGEs and its activating ligands, activation of protein kinase C isoforms, and overactivity of the hexosamine pathway. It also directly inactivates 2 critical antiatherosclerotic enzymes, endothelial nitric oxide synthase and prostacyclin synthase. Through these pathways, increased intracellular reactive oxygen species (ROS) cause defective angiogenesis in response to ischemia, activate a number of proinflammatory pathways, and cause long-lasting epigenetic changes that drive persistent expression of proinflammatory genes after glycemia is normalized ("hyperglycemic memory"). Atherosclerosis and cardiomyopathy in type 2 diabetes are caused in part by pathway-selective insulin resistance, which increases mitochondrial ROS production from free fatty acids and by inactivation of antiatherosclerosis enzymes by ROS. Overexpression of superoxide dismutase in transgenic diabetic mice prevents diabetic retinopathy, nephropathy, and cardiomyopathy. The aim of this review is to highlight advances in understanding the role of metabolite-generated ROS in the development of diabetic complications.

Oxidative stress and diabetic complications

Cancer Invasion and the Microenvironment: Plasticity and Reciprocity

Background— Aging is a major risk factor for the development of atherosclerosis and coronary artery disease. Through a microarray approach, we have identified a microRNA (miR-217) that is progressively expressed in endothelial cells with aging. miR-217 regulates the expression of silent information regulator 1 (SirT1), a major regulator of longevity and metabolic disorders that is progressively reduced in multiple tissues during aging. Methods and Results— miR-217 inhibits SirT1 expression through a miR-217–binding site within the 3′-UTR of SirT1. In young human umbilical vein endothelial cells, human aortic endothelial cells, and human coronary artery endothelial cells, miR-217 induces a premature senescence-like phenotype and leads to an impairment in angiogenesis via inhibition of SirT1 and modulation of FoxO1 (forkhead box O1) and endothelial nitric oxide synthase acetylation. Conversely, inhibition of miR-217 in old endothelial cells ultimately reduces senescence and increases angiogenic activity via...

https://lra.le.ac.uk/bitstream/2381/7850/3/fulltext.pdf

MicroRNA 217 Modulates Endothelial Cell Senescence via Silent Information Regulator 1

Type 2 diabetes is characterized by a two- to fourfold increased risk of cardiovascular disease. This is generally attributed to the adverse effects of hyperglycemia and oxidative stress on vascular biology. It has also been shown that patients with prediabetic conditions, such as impaired fasting glucose and impaired glucose tolerance, are at increased risk of cardiovascular disease as well (1). This result suggests that abnormalities in carbohydrate metabolism form a continuum that progressively worsens cardiovascular health; the first step of the adverse sequence of events that leads to the atherosclerotic process is thought to be endothelial dysfunction (2).

Vascular endothelial cells play a major role in maintaining cardiovascular homeostasis. In addition to providing a physical barrier between the vessel wall and lumen, the endothelium secretes a number of mediators that regulate platelet aggregation, coagulation, fibrinolysis, and vascular tone. The term “endothelial dysfunction” refers to a condition in which the endothelium loses its physiological properties: the tendency to promote vasodilation, fibrinolysis, and anti-aggregation. Endothelial cells secrete several mediators that can alternatively mediate either vasoconstriction, such as endothelin-1 and thromboxane A2, or vasodilation, such as nitric oxide (NO), prostacyclin, and endothelium-derived hyperpolarizing factor. NO is the major contributor to endothelium-dependent relaxation in conduit arteries, whereas the contribution of endothelium-derived hyperpolarizing factor predominates in smaller resistance vessels.

In patients with diabetes, endothelial dysfunction appears to be a consistent finding; indeed, there is general agreement that hyperglycemia and diabetes lead to an impairment of NO production and activity. The endothelium has a limited intrinsic capacity of self-repair, being built up by terminally differentiated cells with a low proliferative potential. That is why endothelial repair is accomplished through the contribution of circulating cells, namely endothelial progenitor cells (EPCs), in physiological and pathological conditions. In this review, we will outline the mechanisms of endothelial dysfunction …

https://care.diabetesjournals.org/content/diacare/34/Supplement_2/S285.full.pdf

Endothelial Dysfunction in Diabetes: The role of reparatory mechanisms

OBJECTIVE—Endothelial progenitor cells (EPCs) are impaired in diabetes. This study aimed to investigate the direct effects of high glucose on EPCs. RESEARCH DESIGN AND METHODS—Mononuclear cells isolated from healthy subjects were incubated with glucose/mannitol or drugs for EPC study. After 4 days of culture, attached early EPCs appeared. The monolayer late EPCs with cobblestone shape appeared at 2–4 weeks. Various immunofluroscence stainings were used to characterize the early and late EPCs. Senescence assay and the activity of endothelial nitric oxide synthase (eNOS) were determined. Migration and tube formation assay were done to evaluate the capacity for vasculogenesis in late EPCs. RESULTS—Chronic incubation with high glucose but not mannitol (osmotic control) dose-dependently reduced the number and proliferation of early and late EPCs, respectively. High glucose enhanced EPC senescence and impaired the migration and tube formation of late EPCs. High glucose also decreased eNOS, FoxO1, and Akt phosphorylation and bioavailable nitric oxide (NO) in both EPCs. The effects of high glucose could be ameliorated by coincubation with NO donor sodium nitroprusside or p38 mitogen–activated protein kinase inhibitor and deteriorated by eNOS inhibitor or PI3K (phosphatidylinositol 3′-kinase) inhibitor. Antioxidants including vitamin C, N -acetylcysteine–and polyethylene glycol (PEG)-conjugated superoxide dismutase, and PEG-catalase had no effects, whereas pyrrolidine dithiocarbamate, diphenyleneiodonium, apocynin, and rotenone even deteriorated the downregulation of both EPCs. CONCLUSIONS—High glucose impaired the proliferation and function of early and late EPCs. NO donor but not antioxidants reversed the impairments, suggesting the role of NO-related rather than oxidative stress–mediated mechanisms in hyperglycemia-caused EPC downregulation.

/pdf/high-glucose-impairs-early-and-late-endothelial-progenitor-58ktdifq27.pdf

High Glucose Impairs Early and Late Endothelial Progenitor Cells by Modifying Nitric Oxide–Related but Not Oxidative Stress–Mediated Mechanisms

Dysfunction of mature endothelial cells is thought to play a major role in both micro- and macrovascular complications of diabetes. However, recent advances in biology of endothelial progenitor cells (EPCs) have highlighted their involvement in diabetes complications. To determine the effect of glucotoxicity on EPCs, human EPCs have been isolated from peripheral blood mononuclear cells of healthy donors and cultured in the presence or absence of high glucose (33 mmol/l) or high glucose plus benfotiamine to scavenge glucotoxicity. Morphological analysis revealed that high glucose significantly affected the number of endothelial cell colony forming units, uptake and binding of acLDL and Lectin-1, and the ability to differentiate into CD31- and vascular endothelial growth factor receptor 2-positive cells. Functional analysis outlined a reduced EPC involvement in de novo tube formation, when cocultured with mature endothelial cells (human umbilical vein endothelial cells) on matrigel. To explain the observed phenotypes, we have investigated the signal transduction pathways known to be involved in EPC growth and differentiation. Our results indicate that hyperglycemia impairs EPC differentiation and that the process can be restored by benfotiamine administration, via the modulation of Akt/FoxO1 activity.

https://diabetes.diabetesjournals.org/content/diabetes/55/8/2231.full.pdf

Benfotiamine counteracts glucose toxicity effects on endothelial progenitor cell differentiation via Akt/FoxO signaling.

Aberrant activation of Wnt/β-catenin signaling is common in most sporadic and inherited colorectal cancer (CRC) cells leading to elevated β-catenin/TCF transactivation. We previously identified the neural cell adhesion molecule L1 as a target gene of β-catenin/TCF in CRC cells. Forced expression of L1 confers increased cell motility, invasion, and tumorigenesis, and the induction of human CRC cell metastasis to the liver. In human CRC tissue, L1 is exclusively localized at the invasive front of such tumors in a subpopulation of cells displaying nuclear β-catenin. We determined whether L1 expression confers metastatic capacities by inducing an epithelial to mesenchymal transition (EMT) and whether L1 cosegregates with cancer stem cell (CSC) markers. We found that changes in L1 levels do not affect the organization or expression of E-cadherin in cell lines, or in invading CRC tissue cells, and no changes in other epithelial or mesenchymal markers were detected after L1 transfection. The introduction of major EMT regulators (Slug and Twist) into CRC cell lines reduced the levels of E-cadherin and induced fibronectin and vimentin, but unlike L1, Slug and Twist expression was insufficient for conferring metastasis. In CRC cells L1 did not specifically cosegregate with CSC markers including CD133, CD44, and EpCAM. L1-mediated metastasis required NF-κB signaling in cells harboring either high or low levels of endogenous E-cadherin. The results suggest that L1-mediated metastasis of CRC cells does not require changes in EMT and CSC markers and operates by activating NF-κβ signaling.

/pdf/l1-mediated-colon-cancer-cell-metastasis-does-not-require-29x3m3aook.pdf

L1-mediated Colon Cancer Cell metastasis does not Require Changes in EMT and Cancer Stem Cell Markers

Skeletal integrity is maintained by the co-ordinated activity of osteoblasts, the bone-forming cells, and osteoclasts, the bone-resorbing cells. In this study, we show that mice overexpressing galectin-8, a secreted mammalian lectin of the galectins family, exhibit accelerated osteoclasts activity and bone turnover, which culminates in reduced bone mass, similar to cases of postmenopausal osteoporosis and cancerous osteolysis. This phenotype can be attributed to a direct action of galectin-8 on primary cultures of osteoblasts that secrete the osteoclastogenic factor RANKL upon binding of galectin-8. This results in enhanced differentiation into osteoclasts of the bone marrow cells co-cultured with galectin-8-treated osteoblasts. Secretion of RANKL by galectin-8-treated osteoblasts can be attributed to binding of galectin-8 to receptor complexes that positively (uPAR and MRC2) and negatively (LRP1) regulate galectin-8 function. Our findings identify galectins as new players in osteoclastogenesis and bone remodeling, and highlight a potential regulation of bone mass by animal lectins.

/pdf/the-mammalian-lectin-galectin-8-induces-rankl-expression-4mtcsbniwd.pdf

The mammalian lectin galectin-8 induces RANKL expression, osteoclastogenesis, and bone mass reduction in mice

Skeletal integrity is maintained by the coordinated activity of osteoblasts, the bone forming cells and osteoclasts, the bone resorbing cells. Here we show that that mice overexpressing galectin-8, a secreted mammalian lectin of the galectins family, exhibit accelerated osteoclasts activity and bone turnover, which culminates in reduced bone mass, similar to cases of post-menopausal osteoporosis and cancerous osteolysis. This phenotype can be attributed to a direct action of galectin-8 on primary cultures of osteoblasts that secrete the osteoclastogenic factor RANKL upon binding of galectin-8. This results in enhanced differentiation into osteoclasts of bone-marrow cells cocultured with galectin-8-treated osteoblasts. Secretion of RANKL by galectin-8-treated osteoblasts can be attributed to binding of galectin-8 to receptor complexes that positively (uPAR and MRC2) and negatively (LRP1) regulate galectin-8 function. Our findings identify galectins as new players in osteoclastogenesis and bone remodeling, and highlight a potential regulation of bone mass by animal lectins. Impact statement: This study shows that a secreted sugar-binding protein, the mammalian lectin galectin-8, induces secretion from osteoblasts of factors that promote the differentiation of bone marrow cells into active osteoclasts. Accordingly, mice overexpressing galectin-8 exhibit accelerated osteoclasts activity and bone turnover, which culminates in reduced bone mass, similar to cases of postmenopausal osteoporosis and cancerous osteolysis. Our data implicate animal lectins as regulators of bone mass and as potential targets for the treatment of diseases associated with excessive bone loss. Competing interests: No competing interests declared Author contributions: Yaron Vinik: ; Conception and design; Acquisition of data; Analysis and interpretation of data Hadas Shatz-Azoulay: ; Conception and design; Acquisition of data; Analysis and interpretation of data Alessia Vivanti: ; Acquisition of data; Analysis and interpretation of data Navit Hever: ; Acquisition of data; Analysis and interpretation of data Yifat Levy: ; Acquisition of data; Analysis and interpretation of data Rotem Karmona: ; Acquisition of data Vlad Brumfeld: ; Analysis and interpretation of data Saja Baraghithy: ; Acquisition of data; Analysis and interpretation of data Malka Attar-Lamdar: ; Acquisition of data; Analysis and interpretation of data Sigalit Boura-Halfon: ; Conception and design; Acquisition of data; Analysis and interpretation of data Itai Bab: ; Conception and design; Analysis and interpretation of data; Drafting or revising the article Yehiel Zick: ; Conception and design; Analysis and interpretation of data; Drafting or revising the article

Alessia Vivanti

Papers

Benfotiamine counteracts glucose toxicity effects on endothelial progenitor cell differentiation via Akt/FoxO signaling.

L1-mediated Colon Cancer Cell metastasis does not Require Changes in EMT and Cancer Stem Cell Markers

The mammalian lectin galectin-8 induces RANKL expression, osteoclastogenesis, and bone mass reduction in mice

FOR PEER REVIEW - CONFIDENTIAL The mammalian lectin galectin-8 induces RANKL expression, osteoclastogenesis and bone mass reduction in mice