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

Protective effects of benfotiamine on cyfluthrin-induced testicular damage and sperm characteristics during the prepubertal period

Cyfluthrin, a widely used synthetic pyrethroid insecticide, poses potential risks to both human health and the environment due to its extensive application in residential, agricultural, and outdoor settings. Conversely, benfotiamine, a fat-soluble derivative of vitamin B1, offers versatile therapeutic potential. This experimental study aimed to investigate the impact of cyfluthrin exposure during the prepubertal period on sperm characteristics and testicular tissue integrity in male rats, as well as to assess the protective effects of benfotiamine. A total of 32 4-week-old Wistar albino male rats were divided into four groups. Group I received daily oral gavage of 1 ml/kg/day of olive oil (control). Group II was administered cyfluthrin (54 mg/kg/day) dissolved in 1 ml of olive oil. Group III received both cyfluthrin (54 mg/kg/day) and benfotiamine (100 mg/kg/day) in olive oil. Group IV was given benfotiamine (100 mg/kg/day) in olive oil. After 5 weeks of treatment, the rats underwent evaluations for sperm motility, epididymal sperm density, and abnormal sperm rates. Additionally, their testicular tissues were examined histologically and immunohistochemically. This study underscores the potential hazards of cyfluthrin exposure on male reproductive health and highlights the protective role of benfotiamine in mitigating these effects. It emphasizes the importance of careful pesticide usage and dosage considerations to prevent potential public health issues, including infertility, associated with long-term exposure to pesticides like cyfluthrin.

Benfotiamine improves dystrophic pathology and exercise capacity in mdx mice by reducing inflammation and fibrosis

Duchenne Muscular Dystrophy (DMD) is a progressive and fatal neuromuscular disease. Cycles of myofibre degeneration and regeneration are hallmarks of the disease where immune cells infiltrate to repair damaged skeletal muscle. Benfotiamine is a lipid soluble precursor to thiamine, shown clinically to reduce inflammation in diabetic related complications. We assessed whether benfotiamine administration could reduce inflammation related dystrophic pathology. Benfotiamine (10 mg/kg/day) was fed to male mdx mice (n = 7) for 15 weeks from 4 weeks of age. Treated mice had an increased growth weight (5-7 weeks) and myofibre size at treatment completion. Markers of dystrophic pathology (area of damaged necrotic tissue, central nuclei) were reduced in benfotiamine mdx quadriceps. Grip strength was increased and improved exercise capacity was found in mdx treated with benfotiamine for 12 weeks, before being placed into individual cages and allowed access to an exercise wheel for 3 weeks. Global gene expression profiling (RNAseq) in the gastrocnemius revealed benfotiamine regulated signalling pathways relevant to dystrophic pathology (Inflammatory Response, Myogenesis) and fibrotic gene markers (Col1a1, Col1a2, Col4a5, Col5a2, Col6a2, Col6a2, Col6a3, Lum) towards wildtype levels. In addition, we observed a reduction in gene expression of inflammatory gene markers in the quadriceps (Emr1, Cd163, Cd4, Cd8, Ifng). Overall, these data suggest that benfotiamine reduces dystrophic pathology by acting on inflammatory and fibrotic gene markers and signalling pathways. Given benfotiamine's excellent safety profile and current clinical use, it could be used in combination with glucocorticoids to treat DMD patients.

Intravital imaging of islet Ca2+ dynamics reveals enhanced β cell connectivity after bariatric surgery in mice

Bariatric surgery improves both insulin sensitivity and secretion and can induce diabetes remission. However, the mechanisms and time courses of these changes, particularly the impact on β cell function, are difficult to monitor directly. In this study, we investigated the effect of Vertical Sleeve Gastrectomy (VSG) on β cell function in vivo by imaging Ca²⁺ dynamics in islets engrafted into the anterior eye chamber. Mirroring its clinical utility, VSG in mice results in significantly improved glucose tolerance, and enhanced insulin secretion. We reveal that these benefits are underpinned by augmented β cell function and coordinated activity across the islet. These effects involve changes in circulating GLP-1 levels which may act both directly and indirectly on the β cell, in the latter case through changes in body weight. Thus, bariatric surgery leads to time-dependent increases in β cell function and intra-islet connectivity which are likely to contribute to diabetes remission.

Neuroprotective Effects of Thiamine and Precursors with Higher Bioavailability: Focus on Benfotiamine and Dibenzoylthiamine

Thiamine (vitamin B1) is essential for brain function because of the coenzyme role of thiamine diphosphate (ThDP) in glucose and energy metabolism. In order to compensate thiamine deficiency, several thiamine precursors with higher bioavailability were developed since the 1950s. Among these, the thioester benfotiamine (BFT) has been extensively studied and has beneficial effects both in rodent models of neurodegeneration and in human clinical studies. BFT has antioxidant and anti-inflammatory properties that seem to be mediated by a mechanism independent of the coenzyme function of ThDP. BFT has no adverse effects and improves cognitive outcome in patients with mild Alzheimer’s disease (AD). Recent in vitro studies show that another thiamine thioester, dibenzoylthiamine (DBT) is even more efficient that BFT, especially with respect to its anti-inflammatory potency. Thiamine thioesters have pleiotropic properties linked to an increase in circulating thiamine concentrations and possibly in hitherto unidentified metabolites in particular open thiazole ring derivatives. The identification of the active neuroprotective derivatives and the clarification of their mechanism of action open extremely promising perspectives in the field of neurodegenerative, neurodevelopmental and psychiatric conditions.

miR-150 regulates endothelial progenitor cell differentiation via Akt and promotes thrombus resolution

Background

Deep venous thrombosis (DVT) constitutes a major global disease burden. Endothelial progenitor cells (EPCs) have been described in association with recanalization of venous thrombus. Furthermore, emerging evidence suggests microRNAs are involved in this progression. The goal of this study was to investigate the influence of miR-150 on the behavior of EPCs and its potential contribution in venous thrombosis resolution.

Methods

We isolated and cultured EPCs from healthy adults. Next, early EPCs or endothelial colony-forming cells (ECFCs or late EPCs) were transfected with miR-150 agomir and antagomir. Gene expression profiles, proliferation, cytokine secretion, and angiogenic capacity of early EPCs and ECFCs were examined. The effects of miR-150 on c-Myb expression and Akt/FOXO1 signaling were also evaluated. Furthermore, a rat model of venous thrombosis was constructed to determine the in vivo function of EPCs.

Results

Our results showed that miR-150 overexpression in early EPCs significantly promoted differentiation to ECFCs and contributed to proliferation and tube formation. However, suppression of miR-150 in late EPCs inhibited proliferation and tube formation. Moreover, we identified that this progression is regulated by inhibition of c-Myb and activation of the Akt/FOXO1 pathway. Our findings also showed that miR-150 led to the enhanced resolution ability of EPCs in a rat venous thrombosis model.

Conclusions

In this study, we present a novel mechanism of miRNA-mediated regulation of EPCs and Akt activation in thrombus resolution.

Investigation of benfotiamine’s protective effects on liver tissue in experimental carbon tetrachloride induced liver injury

Purpose: In this study, we aimed to investigate the protective effects of benfotiamine on experimental liver injury caused by carbon tetrachloride (CCl4).Materials and Methods: In this study, 30 male Wistar albino rats were used. Rats were equally divided into 5 groups. No application was made to control group. The CCl4 group was injected i.p with1ml/kg CCl4:olive oil (1:2) mixture on the 1st and 8th days, and the CCl4+benfotiamine group was treated i.p with 1 ml/kg CCl4: olive oil (1:2) mixture twice on the 1st and 8th days and orally with 70 mg/kg/day benfotiamine. To the benfotiamine group, 70 mg/kg/day benfotiamine was given orally for 14 days. To the olive oil group, 2 ml/kg olive oil was given i.p. on 1st and 8th days. Finally, rats were decapitated. Liver tissues were removed and paraffin blocks were prepared. Tissues were stored at –80 oC for malonaldeyhde (MDA) assay.Results: There were no significant differences between the control, benfotiamine and olive oil groups. Compared with the control group, there was a significant increase in MDA, apoptosis and bax immunoreactivity in CCl4 group. Compared with the CCl4 group, there was a significant decrease in MDA, apoptosis and bax immunoreactivity in the CCl4+benfotiamine group.Conclusion: CCl4 increases MDA, apoptosis and bax immunoreactivity, and benfotiamine, given as treatment, reduces these parameters. 

D-ribose is elevated in T1DM patients and can be involved in the onset of encephalopathy

Although many mechanisms have been proposed for diabetic encephalopathy in type 2 diabetes mellitus (T2DM), the risk factors for cognitive impairment in type 1 diabetes mellitus (T1DM) are less clear. Here, we show that streptozotocin (STZ)-induced T1DM rats showed cognitive impairment in both Y maze and Morris water maze assays, accompanied with D-ribose was significantly increased in blood and urine, in addition to D-glucose. Furthermore, advanced glycation end products (AGE), Tau hyperphosphorylation and neuronal death in the hippocampal CA4/DG region were detected in T1DM rats. The expression and activity of transketolase (TKT), an important enzyme in the pentose shunt, were decreased in the brain, indicating that TKT may be involved in D-ribose metabolism in T1DM. Support for these change was demonstrated by the activation of TKT with benfotiamine (BTMP) treatment. Decreased D-ribose levels but not D-glucose levels; markedly reduced AGE accumulation, Tau hyperphosphorylation, and neuronal death; and improved cognitive ability in T1DM rats were shown after BTMP administration. In clinical investigation, T1DM patients had high D-ribose levels in both urine and serum. Our work suggests that D-ribose is involved in the cognitive impairment in T1DM and may provide a potentially novel target for treating diabetic encephalopathy.

Fenofibrate improves vascular endothelial function in diabetic mice

Microvascular and macrovascular complications are major causes of disability and death in diabetic patients. High levels of blood glucose sabotage the integrity of blood vessels and induce endothelial dysfunction. Fenofibrate is an agonist of peroxisome proliferator-activated receptor α and can reduce the incidence of cardiovascular events in diabetic patients. This study tested the hypothesis that fenofibrate could ameliorate endothelium-dependent vasodilation in diabetic mice and relieve high glucose-induced endothelial dysfunction via activating endothelial nitric oxide synthase (eNOS) and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. A streptozotocin (STZ)-induced diabetic model was established by intraperitoneal injection of STZ (dissolved in sodium citrate buffer) at a dose of 60 mg/kg for 5 consecutive days. Mice were administered fenofibrate (100 mg/kg/d, i.g.) for 14 days. The endothelial function of extracted mouse aortae was examined by evaluating acetylcholine induced endothelium-dependent relaxation combined with phenylephrine-induced vasoconstriction and sodium nitroprusside-induced endothelium-independent relaxation. Superoxide onion (O₂^-) was determined using dihydroethidium staining of aortae. Functions of mouse aortic endothelial cells (MAECs) were assessed, and expression levels of eNOS and AMPK were determined by Western blotting. Fenofibrate ameliorated the impaired endothelium-dependent relaxation in diabetic mice and decreased the level of intracellular O₂- in diabetic mouse aortae. In-vitro, fenofibrate treatment improved the impaired function of MAECs, increased nitric oxide production, and decreased the O₂- level, as well as activated eNOS and AMPK phosphorylation in cultured MAECs by high glucose. Fenofibrate could ameliorate endothelium-dependent vasodilation in diabetic mice and relieve high glucose-induced endothelial dysfunction, which was possibly related to the activation of eNOS and AMPK phosphorylation.

Isolation of allithiamine from Hungarian red sweet pepper seed (Capsicum annuum L.)

A natural fat-soluble thiamine derivative, namely N-[(4-amino-2-methylpyrimidin-5-yl)methyl]-N-[(2E)-5-hydroxy-3-(prop-2-en-1-yldisulfanyl)pent-2-en-2-yl]formamide (allithiamine) has been identified only in garlic (Allium sativum) until now. Hungarian red sweet pepper (Capsicum annuum) was found as a new source of allithiamine. Extraction procedure and analytical method were developed for the isolation of allithiamine and a chemical synthesis of the compound was also developed. First solid-liquid extraction was performed with 96 % ethanol to isolate allithiamine from pepper seeds. Thereafter, solid phase extraction was applied from ethanolic extract using C18 cartridge to concentrate and purify samples for further analysis. The structure of the synthesized and the isolated compounds was verified by reverse phase HPLC, HPLC-MS, MALD-TOF MS and NMR. Furthermore, effect of allithiamine was investigated on streptozotocin-induced diabetic mice with neuropathy. The results show that neuropathic pain sensation is improved by allithiamine treatment similarly to benfothiamine.

Diabetic retinopathy: a complex pathophysiology requiring novel therapeutic strategies

INTRODUCTION

Diabetic retinopathy (DR) is the leading cause of vision loss in the working age population of the developed world. DR encompasses a complex pathology, and one that is reflected in the variety of currently available treatments, which include laser photocoagulation, glucocorticoids, vitrectomy and agents which neutralize vascular endothelial growth factor (VEGF). Whilst these options demonstrate modest clinical benefits, none is yet to fully attenuate clinical progression or reverse damage to the retina. This has led to an interest in developing novel therapies for the condition, such as mediators of angiopoietin signaling axes, immunosuppressants, nonsteroidal anti-inflammatory drugs (NSAIDs), oxidative stress inhibitors and vitriol viscosity inhibitors. Further, preclinical research suggests that gene therapy treatment for DR could provide significant benefits over existing treatments options.

AREAS COVERED

Here we review the pathophysiology of DR and provide an overview of currently available treatments. We then outline recent advances made towards improved patient outcomes and highlight the potential of the gene therapy paradigm to revolutionize DR management.

EXPERT OPINION

Whilst significant progress has been made towards our understanding of DR, further research is required to enable the development of a detailed spatiotemporal model of the disease. In addition, we hope that improvements in our knowledge of the condition facilitate therapeutic innovations that continue to address unmet medical need and improve patient outcomes, with a focus on the development of targeted medicines.

Dysfunction and Therapeutic Potential of Endothelial Progenitor Cells in Diabetes Mellitus

Diabetes mellitus (DM) is a chronic, multifactorial metabolic disease whereby insulin deficiency or resistance results in hyperglycemia. Endothelial cells (ECs) form the innermost layer of the blood vessel and produce and release a variety of vasoactive substances and growth factors to regulate vascular homeostasis and angiogenesis. Hyperglycemia and insulin resistance can cause endothelial dysfunction, leading to vascular complications such as coronary artery disease, peripheral arterial disease, diabetic nephropathy, neuropathy and retinopathy. The detrimental effect exerted on ECs by hyperglycemia and insulin resistance underlines the importance of reparatory mechanisms in DM. Endothelial progenitor cells (EPCs), derived from bone marrow, have been recognized as endogenous cells involved in endothelial repair and new blood vessel formation. Initially isolated from a subset of circulating CD34+ mononuclear cells, EPCs were found to possess the ability to differentiate into ECs when cultured in vitro and incorporate into newly formed vessels upon transplantation in animal models of ischemia. Due to the low frequency of CD34+ cells in circulation, the vast majority of studies investigating EPC actions have used cells that are generated through the culture of peripheral blood mononuclear cells (PBMNCs) for 4 - 7 days in endothelial selective medium. These cells, mainly of myeloid hematopoietic cell origin, were termed “Early EPCs,” of which, few expressed stem/progenitor-cell markers. Therefore, early EPCs were also termed “myeloid angiogenic cells” (MACs). When PBMNCs are cultured for over 2 weeks, early EPCs gradually diminish while so-called late EPCs appear. Late EPCs share phenotypic features with mature ECs and are therefore also termed blood-derived ECs; they will not be addressed in this review. MAC dysfunction has been observed in a variety of disease conditions including DM. In this article we review the activities and therapeutic potential of MACs in DM. We will interchangeably use “EPCs” and “MACs” to refer to the cells procured by culture of PBMNCs in EC selective medium for approximately 7 days.

Vascular toxicity of urea, a new "old player" in the pathogenesis of chronic renal failure induced cardiovascular diseases

Chronic kidney disease in children is an irreversible process that may lead to end-stage renal disease. The mortality rate in children with end-stage renal disease who receive dialysis increased dramatically in the last decade, and it is significantly higher compared with the general pediatric population. Furthermore, dialysis and transplant patients, who have developed end-stage renal disease during childhood, live respectively far less as compared with age/race-matched populations. Different reports show that cardiovascular disease is the leading cause of death in children with end-stage renal disease and in adults with childhood-onset chronic kidney disease, and that children with chronic kidney disease are in the highest risk group for the development of cardiovascular disease. Urea, which is generated in the liver during catabolism of amino acids and other nitrogenous metabolites, is normally excreted into the urine by the kidneys as rapidly as it is produced. When renal function is impaired, increasing concentrations of blood urea will steadily accumulate. For a long time, urea has been considered to have negligible toxicity. However, the finding that plasma urea is the only significant predictor of aortic plaque area fraction in an animal model of chronic renal failure -accelerated atherosclerosis, suggests that the high levels of urea found in chronic dialysis patients might play an important role in accelerated atherosclerosis in this group of patients. The aim of this review was to provide novel insights into the role played by urea in the pathogenesis of accelerated cardiovascular disease in renal failure.

High glucose-induced endothelial progenitor cell dysfunction

Vascular complications contribute significantly to morbidity and mortality of diabetes mellitus. The primary cause of vascular complications in diabetes mellitus is hyperglycaemia, associated with endothelial dysfunction and impaired neovascularization. Circulating endothelial progenitor cells was shown to play important roles in vascular repair and promoting neovascularization. In this review, we will demonstrate the individual effect of high glucose on endothelial progenitor cells. Endothelial progenitor cells isolated from healthy subjects exposed to high glucose conditions or endothelial progenitor cells isolated from diabetic patients exhibit reduced number of endothelial cell colony forming units, impaired abilities of differentiation, proliferation, adhesion and migration, tubulization, secretion, mobilization and homing, whereas enhanced senescence. Increased production of reactive oxygen species by the mitochondria seems to play a crucial role in high glucose-induced endothelial progenitor cells deficit. Later, we will review the agents that might be used to alleviate dysfunction of endothelial progenitor cells induced by high glucose. The conclusions are that the relationship between hyperglycaemia and endothelial progenitor cells dysfunction is only beginning to be recognized, and future studies should pay more attention to the haemodynamic environment of endothelial progenitor cells and ageing factors to discover novel treatment agents.

Urea-induced ROS accelerate senescence in endothelial progenitor cells

BACKGROUND AND AIMS

The pathogenic events responsible for the reduction of endothelial progenitor cell (EPC) number and function seen in patients with chronic renal failure (CRF) are poorly understood. Here we investigate the hypothesis that increased concentrations of urea associated with CRF increase ROS production directly in EPCs, causing abnormalities associated with coronary artery disease risk.

METHODS

Human EPCs were isolated from peripheral blood mononuclear cells of healthy donors and cultured in the presence or absence of 20 mmol/L urea.

RESULTS

Urea at concentrations seen in CRF induced ROS production in cultured EPCs. Urea-induced ROS reduced the number of endothelial cell colony forming units, uptake and binding of Dil-Ac-LDL and lectin-1, and the ability to differentiate into CD31- and vascular endothelial growth factor receptor 2-positive cells. Moreover, urea-induced ROS generation accelerated the onset of EPC senescence, leading to a senescence-associated secretory phenotype (SASP). Normalization of mitochondrial ROS production prevented each of these effects of urea.

CONCLUSIONS

These data suggest that urea itself causes both reduced EPC number and increased EPC dysfunction, thereby contributing to the pathogenesis of cardiovascular disease in CRF patients.

Thiamine and benfotiamine prevent stress-induced suppression of hippocampal neurogenesis in mice exposed to predation without affecting brain thiamine diphosphate levels

Thiamine is essential for normal brain function and its deficiency causes metabolic impairment, specific lesions, oxidative damage and reduced adult hippocampal neurogenesis (AHN). Thiamine precursors with increased bioavailability, especially benfotiamine, exert neuroprotective effects not only for thiamine deficiency (TD), but also in mouse models of neurodegeneration. As it is known that AHN is impaired by stress in rodents, we exposed C57BL6/J mice to predator stress for 5 consecutive nights and studied the proliferation (number of Ki67-positive cells) and survival (number of BrdU-positive cells) of newborn immature neurons in the subgranular zone of the dentate gyrus. In stressed mice, the number of Ki67- and BrdU-positive cells was reduced compared to non-stressed animals. This reduction was prevented when the mice were treated (200mg/kg/day in drinking water for 20days) with thiamine or benfotiamine, that were recently found to prevent stress-induced behavioral changes and glycogen synthase kinase-3β (GSK-3β) upregulation in the CNS. Moreover, we show that thiamine and benfotiamine counteract stress-induced bodyweight loss and suppress stress-induced anxiety-like behavior. Both treatments induced a modest increase in the brain content of free thiamine while the level of thiamine diphosphate (ThDP) remained unchanged, suggesting that the beneficial effects observed are not linked to the role of this coenzyme in energy metabolism. Predator stress increased hippocampal protein carbonylation, an indicator of oxidative stress. This effect was antagonized by both thiamine and benfotiamine. Moreover, using cultured mouse neuroblastoma cells, we show that in particular benfotiamine protects against paraquat-induced oxidative stress. We therefore hypothesize that thiamine compounds may act by boosting anti-oxidant cellular defenses, by a mechanism that still remains to be unveiled. Our study demonstrates, for the first time, that thiamine and benfotiamine prevent stress-induced inhibition of hippocampal neurogenesis and accompanying physiological changes. The present data suggest that thiamine precursors with high bioavailability might be useful as a complementary therapy in several neuropsychiatric disorders.

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

Metformin improves the angiogenic functions of endothelial progenitor cells via activating AMPK/eNOS pathway in diabetic mice

Background

Endothelial dysfunction has been suggested as a possible causal link between hyperglycemia and microvascular complications in diabetes mellitus. The effect of metformin on endothelial progenitor cells (EPCs) is still unclear. This study was designed to test the hypothesis that metformin could accelerate wound healing by improving the impaired EPC functions in streptozotocin-induced diabetic mice.

Methods

Streptozotocin (STZ, 60 mg/kg/d × 5 d, i.p.) was injected to induce type 1 diabetes in male C57BL/6 mice. Mice were treated with metformin (250 mg/kg/d, i.g.) for consecutive 14 days. Wound closure was evaluated by wound area and number of CD31 stained capillaries. Functions of bone marrow-endothelial progenitor cells (BM-EPCs) were assessed by tube formation and migration assays, and expression of AMP-activated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS) was determined by western blot analysis.

Results

Metformin accelerated wound closure and stimulated angiogenesis in diabetic mice. The number of circulating EPCs was increased significantly in metformin treated diabetic mice. Abilities of tube formation and migration of BM-EPCs were impaired in diabetic mice, which were improved by metformin. Expression of both phosphorylated-AMPK and phosphorylated-eNOS was significantly increased, and nitric oxide (NO) production was enhanced by metformin in BM-EPCs of diabetic mice. In vitro, metformin improved impaired BM-EPC functions, and increased phosphorylated-eNOS expression and NO production in cultured BM-EPCs caused by high glucose, which was prevented by the AMPK inhibitor compound C.

Conclusions

Our results suggest that metformin could improve BM-EPC functions in STZ-induced diabetic mice, which was possibly dependent on the AMPK/eNOS pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0408-3) contains supplementary material, which is available to authorized users.

Paraptosis cell death induction by the thiamine analog benfotiamine in leukemia cells

Benfotiamine is a synthetic thiamine analogue that stimulates transketolase, a cellular enzyme essential for glucose metabolism. Currently, benfotiamine is used to treat diabetic neuropathy. We recently reported that oral benfotiamine induced a temporary but remarkable recovery from acute myeloid leukemia in an elderly patient who was ineligible for standard chemotherapy due to dementia and renal failure. In the present study we present evidences that benfotiamine possess antitumor activity against leukemia cells. In a panel of nine myeloid leukemia cell lines benfotiamine impaired the viability of HL-60, NB4, K562 and KG1 cells and also inhibited the growing of primary leukemic blasts. The antitumor activity of benfotiamine is not mediated by apoptosis, necrosis or autophagy, but rather occurs though paraptosis cell death induction. Mechanistic studies revealed that benfotiamine inhibited the activity of constitutively active ERK1/2 and concomitantly increased the phosphorylation of JNK1/2 kinase in leukemic cells. In addition, benfotiamine induced the down regulation of the cell cycle regulator CDK3 which resulted in G1 cell cycle arrest in the sensitive leukemic cells. Moreover, combination index studies showed that benfotiamine enhanced the antiproliferative activities of cytarabine against leukemia cells. These findings suggest that benfotiamine has antitumor therapeutic potential.

Regulation of EPCs: The Gateway to Blood Vessel Formation

Endothelial progenitor cells (EPCs) are primitive endothelial precursors which are known to functionally contribute to the pathogenesis of disease. To date a number of distinct subtypes of these cells have been described, with differing maturation status, cellular phenotype, and function. Although there is much debate on which subtype constitutes the true EPC population, all subtypes have endothelial characteristics and contribute to neovascularisation. Vasculogenesis, the process by which EPCs contribute to blood vessel formation, can be dysregulated in disease with overabundant vasculogenesis in the context of solid tumours, leading to tumour growth and metastasis, and conversely insufficient vasculogenesis can be present in an ischemic environment. Importantly, it is widely known that transcription factors tightly regulate cellular phenotype and function by controlling the expression of particular target genes and in turn regulating specific signalling pathways. This suggests that transcriptional regulators may be potential therapeutic targets to control EPC function. Herein, we discuss the observed EPC subtypes described in the literature and review recent studies describing the role of a number of transcriptional families in the regulation of EPC phenotype and function in normal and pathological conditions.

Understanding regulatory pathways of neovascularization in diabetes

Diabetes mellitus and its associated comorbidities represent a significant health burden worldwide. Vascular dysfunction is the major contributory factor in the development of these comorbidities, which include impaired wound healing, cardiovascular disease and proliferative diabetic retinopathy. While the etiology of abnormal neovascularization in diabetes is complex and paradoxical, the dysregulation of the varied processes contributing to the vascular response are due in large part to the effects of hyperglycemia. In this review, we explore the mechanisms by which hyperglycemia disrupts chemokine expression and function, including the critical hypoxia inducible factor-1 axis. We place particular emphasis on the therapeutic potential of strategies addressing these pathways; as such targeted approaches may one day help alleviate the healthcare burden of diabetic sequelae.

Evidence for altered thiamine metabolism in diabetes: Is there a potential to oppose gluco- and lipotoxicity by rational supplementation?

Growing prevalence of diabetes (type 2 as well as type 1) and its related morbidity due to vascular complications creates a large burden on medical care worldwide. Understanding the molecular pathogenesis of chronic micro-, macro- and avascular complications mediated by hyperglycemia is of crucial importance since novel therapeutic targets can be identified and tested. Thiamine (vitamin B1) is an essential cofactor of several enzymes involved in carbohydrate metabolism and published data suggest that thiamine metabolism in diabetes is deficient. This review aims to point out the physiological role of thiamine in metabolism of glucose and amino acids, to present overview of thiamine metabolism and to describe the consequences of thiamine deficiency (either clinically manifest or latent). Furthermore, we want to explain why thiamine demands are increased in diabetes and to summarise data indicating thiamine mishandling in diabetics (by review of the studies mapping the prevalence and the degree of thiamine deficiency in diabetics). Finally, we would like to summarise the evidence for the beneficial effect of thiamine supplementation in progression of hyperglycemia-related pathology and, therefore, to justify its importance in determining the harmful impact of hyperglycemia in diabetes. Based on the data presented it could be concluded that although experimental studies mostly resulted in beneficial effects, clinical studies of appropriate size and duration focusing on the effect of thiamine supplementation/therapy on hard endpoints are missing at present. Moreover, it is not currently clear which mechanisms contribute to the deficient action of thiamine in diabetes most. Experimental studies on the molecular mechanisms of thiamine deficiency in diabetes are critically needed before clear answer to diabetes community could be given.

The detrimental effects of acute hyperglycemia on myocardial glucose uptake

AIMS

Although acute hyperglycemic (AHG) episodes are linked to lower glucose uptake, underlying mechanisms remain unclear. We hypothesized that AHG triggers reactive oxygen species (ROS) production and increases non-oxidative glucose pathway (NOGP) activation, i.e. stimulation of advanced glycation end products (AGE), polyol pathway (PP), hexosamine biosynthetic pathway (HBP), PKC; thereby decreasing cardiac glucose uptake.

MAIN METHODS

H9c2 cardiomyoblasts were exposed to 25 mM glucose for 24h vs. 5.5mM controls ± modulating agents during the last hour of glucose exposure: a) antioxidant #1 for mitochondrial ROS (250 μM 4-OHCA), b) antioxidant #2 for NADPH oxidase-generated ROS (100 μM DPI), c) NOGP inhibitors - 100 μM aminoguanidine (AGE), 5 μM chelerythrine (PKC); 40 μM DON (HBP); and 10 μM zopolrestat (PP). ROS levels (mitochondrial, intracellular) and glucose uptake were evaluated by flow cytometry.

KEY FINDINGS

AHG elevated ROS, activated NOGPs and blunted glucose uptake. Transketolase activity (pentose phosphate pathway [PPP] marker) did not change. Respective 4-OHCA and DPI treatment blunted ROS production, diminished NOGP activation and normalized glucose uptake. NOGP inhibitory studies identified PKCβII as a key downstream player in lowering insulin-mediated glucose uptake. When we employed an agent (benfotiamine) known to shunt flux away from NOGPs (into PPP), it decreased ROS generation and NOGP activation, and restored glucose uptake under AHG conditions.

SIGNIFICANCE

This study demonstrates that AHG elicits maladaptive events that function in tandem to reduce glucose uptake, and that antioxidant treatment and/or attenuation of NOGP activation (PKC, polyol pathway) may limit the onset of insulin resistance.

Glycogen synthase kinase-3β inhibition augments diabetic endothelial progenitor cell abundance and functionality via cathepsin B: a novel therapeutic opportunity for arterial repair

Progenitor cell therapy is hindered in patients with diabetes mellitus (DM) due to cellular senescence. Glycogen synthase kinase-3β (GSK3β) activity is increased in DM, potentially exacerbating impaired cell-based therapies. Thus, we aimed to determine if and how GSK3β inhibitors (GSKi) can improve therapeutic efficacy of endothelial progenitor cells (EPC) from patients with DM. Patients with DM had fewer EPCs and increased rates of apoptosis. DM EPCs also exhibited higher levels of GSK3β activity resulting in increased levels of phosphorylated β-catenin. Proteomic profiling of DM EPCs treated with GSKi identified 37 nonredundant, differentially regulated proteins. Cathepsin B (cathB) was subsequently confirmed to be differentially regulated and showed 40% less baseline activity in DM EPCs, an effect reversed by GSKi treatment. Finally, in vivo efficacy of cell-based therapy was assessed in a xenotransplant femoral wire injury mouse model. Administration of DM EPCs reduced the intima-to-media ratio, an effect that was further augmented when DM EPCs were pretreated with GSKi yet absent when cathB was antagonized. In DM, increased basal GSK3β activity contributes to accelerated EPC cellular senescence, an effect reversed by small molecule antagonism of GSK3β, which enhanced cell-based therapy after vascular injury.

Pharmacokinetic study of benfotiamine and the bioavailability assessment compared to thiamine hydrochloride

Benfotiamine is a lipid-soluble thiamine precursor which can transform to thiamine in vivo and subsequently be metabolized to thiamine monophosphate (TMP) and thiamine diphosphate (TDP). This study investigated the pharmacokinetic profiles of thiamine and its phosphorylated metabolites after single- and multiple-dose administration of benfotiamine in healthy Chinese volunteers, and assessed the bioavailability of orally benfotiamine administration compared to thiamine hydrochloride. In addition, concentration of hippuric acid in urine which is produced in the transformation process of benfotiamine was determined. The results showed that thiamine and its phosphorylated metabolites exhibited different pharmacokinetic characteristics in plasma, blood and erythrocyte, and one-compartment model provided the best fit for pharmacokinetic profiles of thiamine. The transformation process of benfotiamine to thiamine produced large amount of hippuric acid. No accumulation of hippuric acid was observed after multiple-dose of benfotiamine. Compared to thiamine hydrochloride, the bioavailability of thiamine in plasma and TDP in erythrocyte after oral administration of benfotiamine were 1147.3 ± 490.3% and 195.8 ± 33.8%, respectively. The absorption rate and extent of benfotiamine systemic availability of thiamine were significantly increased indicating higher bioavailability of thiamine from oral dose of benfotiamine compared to oral dose of thiamine hydrochloride.

Hydrogen peroxide induced impairment of endothelial progenitor cell viability is mediated through a FoxO3a dependant mechanism

OBJECTIVES

Increased oxidative stress has been suggested to contribute to the functional impairment of endothelial progenitor cells (EPCs). The Forkhead box O transcription factors (FoxOs) are critical regulators involved in various cellular processes including cell apoptosis. Here, we investigated whether FoxOs are required in oxidative stress induced EPC apoptosis.

METHODS AND RESULTS

EPCs were cultured from cord blood derived mononuclear cells and treated with hydrogen peroxide (H2O2) for induction of oxidative stress. Incubation with H2O2 dose dependently reduced viability and increased apoptosis in EPCs. Western blotting showed that EPCs predominantly expressed FoxO3a and the expression was markedly increased upon H2O2 treatment. Transduction with adenoviral vectors expressing either a wide-type or a non-phosphorylatable, constitutively active mutant of FoxO3a led to further increased apoptosis of EPCs after H2O2 treatment. Conversely, FoxO3a silencing rescued EPCs from these H2O2 induced deleterious effects. Overexpression of FoxO3a also increased the level of the pro-apoptotic protein Bim, whereas FoxO3a silencing downregulated H2O2 induced Bim expression. Furthermore, Matrigel assay demonstrated that FoxO3a overexpression significantly impaired the tube forming ability of EPCs, whereas its silencing completely protected EPCs from H2O2 induced decrease of capillary formation.

CONCLUSIONS

These data suggest that oxidative stress induced impairment of EPC survival is mediated through a FoxO3a dependant mechanism, possibly by transcriptional regulation of Bim. Our data indicate FoxO3a as a potential therapeutic target for improvement of EPC number and function in patients with ischemic heart disease.

Endothelial progenitor cells are related to glycemic control in children with type 1 diabetes over time

OBJECTIVE

The risk of cardiovascular death before the age of 40 is 20-fold higher in patients with type 1 diabetes mellitus (T1DM). Endothelial progenitor cells (EPCs) predict cardiovascular morbidity and mortality in patients without diabetes. We hypothesized that EPCs are modified in children with T1DM and are related to characteristics of T1DM such as glycemic control.

RESEARCH DESIGN AND METHODS

Children (n = 190; 156 T1DM subjects and 34 control subjects) were included in an observational cohort study and matched for age and sex. EPCs were enumerated by flow cytometry at the beginning (cross-sectional) and 1 year later (longitudinal). To analyze changes of variables during the observation, Δ values were calculated.

RESULTS

EPCs were significantly reduced in T1DM children versus control subjects (609 ± 359 vs. 1,165 ± 484, P < 0.001). Multivariate regression modeling revealed that glycated hemoglobin A1c (HbA1c) was the strongest independent predictor of EPCs (β = -0.355, P < 0.001). Overall glycemic control at the beginning and end of study did not differ (7.8 ± 1.2 vs. 7.8 ± 1.2 relative %, P = NS), but we observed individual HbA1c changes of -4.30/+3.10 relative %. The strongest EPC increase was observed in the patients with the most favorable HbA1c lowering during the 1-year follow-up. Accordingly, the strongest EPC decrease was demonstrated in the patients with the strongest HbA1c worsening during the time period.

CONCLUSIONS

This is the first prospective study demonstrating diminished EPCs in children with T1DM. The association of better glycemic control with an increase in EPC numbers within 1 year suggests that a reduction of the high cardiovascular disease burden might be mediated likewise.

Restoring stem cell mobilization to promote vascular repair in diabetes

Diabetes triggers endothelial dysfunction, which is linked to increased risk of cardiovascular diseases. Stem and progenitor cells from the bone marrow are involved in the maintenance of vascular integrity. Diabetic patients show a dysfunction of these cells, which might represent a novel pathophysiological mechanism of vascular disease. Specifically, stem and progenitor cells fail to egress from the bone marrow (BM) due to BM pathological alterations and unresponsiveness to mobilizing stimuli. In this review, we describe impaired stem cell mobilization in diabetes as a mechanism of failed vascular repair and we provide evidence that pharmacological strategies can restore mobilization. We discuss recent advances in the knowledge of aberrant organization of the diabetic BM and its implications for impaired mobilization. Finally, we describe in detail the pharmacological exploitation of the G-CSF/DPP-4(CD26)/SDF-1α axis as a novel strategy to improve mobilization and attain vascular repair in diabetes.

The role of FoxO4 in the relationship between alcohol-induced intestinal barrier dysfunction and liver injury

Forkhead box 'Other' (FoxO) proteins, a subgroup of the Forkhead transcription factor family, play an important role in mediating the effects of insulin and growth factors on diverse physiological functions. In this study, we investigated the role of FoxO4 in the relationship between alcohol liver disease and intestinal barrier dysfunction using an animal model. Six to eight-week-old male WT rats were divided into eight groups. They were separately administered corn starch dissolved in PBS; 40% alcohol (5 g/kg body weight) through stomach feeding every 12 h/time, three times in total; tumor necrosis factor α (TNFα) (10 µg/kg) injected intraperitoneally 30 min before alcohol administration; wortmannin (1.4 mg/kg) 30 min before alcohol administration; IGF-1 (0.2 mg/kg) 30 min before alcohol administration; anti-TNFα (5 mg/kg) injected intravenously 30 min before alcohol administration. In addition, two placebo groups were treated with PBS either intraperitoneally or intravenously prior to alcohol administration. TNFα and endotoxin in plasma were measured by ELISA and Tachypleus Amebocye Lysate assays. Immunohistochemistry and western blotting were used to identify the mechanisms of FoxO4 action in regulating epithelial permeability. Furthermore, electron microscopy, reverse transcription-polymerase chain reaction and western blotting were used to examine the expression of tight junction proteins and nuclear factor-κB (NF-κB). Compared with the control group, TNFα in the alcohol group was significantly higher. TNFα could induce FoxO4 phosphorylation; p-FoxO4 was limited into the cytoplasm and inactivated; inactive FoxO4 which was in high levels lost the ability to suppress NF-κB. Therefore, the expression of NF-κB was increased and it downregulated tight junction protein (including ZO-1 and occludin) expression, and increased epithelial permeability. As a result, intestinal bacteria grew excessively, endotoxin was released into the portal circulation and liver injury deteriorated. These results indicate that a complex network of mechanisms is involved in the beneficial effects of FoxO4 in epithelial barrier dysfunction. TNFα can upregulate phosphorylation of FoxO4. FoxO4 which is located in the nucleus is limited into the cytoplasm and inactivated; it loses the ability to suppress NF-κB activity, it downregulates the expression of tight junction proteins and increases epithelial permeability. Disruption of the intestinal barrier allows endotoxin and other bacterial products in the gut lumen to pass into the portal circulation and cause hepatic inflammation. At the same time, the changes of liver injury deteriorate.

Benfotiamine counteracts smoking-induced vascular dysfunction in healthy smokers

Background. Smoking induces endothelial dysfunction (ED) mainly by exacerbating oxidative stress (OS) and inflammation. Benfotiamine, a thiamine prodrug with high bioavailability, prevents nicotine-induced vascular dysfunction in rats. It remained unknown whether this effect also occurs in humans. Methods. Therefore, 20 healthy volunteers (mean age: 38 years) were investigated twice, 7–10 days apart in a randomized, cross-over, and investigator-blinded design. Vascular function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery and by measurements of the soluble vascular cell adhesion molecule (sVCAM)-1. Investigations were performed after an overnight fast as well as 20 minutes after one cigarette smoking. On another day, the same procedure was applied following a 3-day oral therapy with benfotiamine (1050 mg/day). Ten patients were randomized to start with smoking alone, and ten started with benfotiamine. Results. Results are expressed as (mean ± SEM). Smoking acutely induced a decrease in FMD by 50% (^∗∗P < 0.001 versus baseline) an effect significantly reduced by benfotiamine treatment to 25%^∗§ (^∗P < 0.05 versus baseline, ^§P < 0.05 versus smoking alone). Smoking-induced elevation in sVCAM-1 was also prevented by benfotiamine. The endothelium-independent vasodilatation remained unaltered between days. Conclusion. In healthy volunteers, smoking blunts vascular function mirrored by a decrease in FMD and an increase in sVCAM-1. Short-term treatment with benfotiamine significantly reduces these effects, showing protective vascular properties.

Benfotiamine prevents increased β-amyloid production in HEK cells induced by high glucose

OBJECTIVE

To determine whether high glucose enhances β-amyloid (Aβ) production in HEK293 Swedish mutant (APPsw) cells with Aβ precursor protein (APP) overexpression, and whether under this condition benfotiamine reduces the increased Aβ production.

METHODS

HEK293 APPsw cells were cultured with different concentrations of glucose for different times. The Aβ content in the supernatant was determined by ELISA. To investigate the mechanism by which benfotiamine reduced Aβ production, glycogen synthase kinase-3 (GSK-3) activity and expression were measured after the cells were cultured with 5.5 g/L glucose for 12 h.

RESULTS

With 1.0, 3.0, 4.5, 5.5, 6.5, 7.5, 8.5, or 10.5 g/L glucose, Aβ production by HEK293 APPsw cells was highest in the presence of 5.5 g/L glucose for 6 and 12 h. The difference in Aβ content between 5.5 and 1.0 g/L was most marked after incubation for 12 h. Benfotiamine at 20 and 40 μg/mL significantly reduced Aβ production in cells incubated with 5.5 g/L glucose for 12 h. Moreover, 40 μg/mL benfotiamine significantly enhanced the ratio of phosphorylated GSK-3 to total GSK-3, together with consistent down-regulation of GSK-3 activity.

CONCLUSION

High glucose increases Aβ production by HEK293 APPsw cells while benfotiamine prevents this increase. This is correlated with the modulation of GSK-3 activity.

Strategies to reverse endothelial progenitor cell dysfunction in diabetes

Bone-marrow-derived cells-mediated postnatal vasculogenesis has been reported as the main responsible for the regulation of vascular homeostasis in adults. Since their discovery, endothelial progenitor cells have been depicted as mediators of postnatal vasculogenesis for their peculiar phenotype (partially staminal and partially endothelial), their ability to differentiate in endothelial cell line and to be incorporated into the vessels wall during ischemia/damage. Diabetes mellitus, a condition characterized by cardiovascular disease, nephropathy, and micro- and macroangiopathy, showed a dysfunction of endothelial progenitor cells. Herein, we review the mechanisms involved in diabetes-related dysfunction of endothelial progenitor cells, highlighting how hyperglycemia affects the different steps of endothelial progenitor cells lifetime (i.e., bone marrow mobilization, trafficking into the bloodstream, differentiation in endothelial cells, and homing in damaged tissues/organs). Finally, we review preclinical and clinical strategies that aim to revert diabetes-induced dysfunction of endothelial progenitor cells as a means of finding new strategies to prevent diabetic complications.

FoxO1, the transcriptional chief of staff of energy metabolism

FoxO1, one of the four FoxO isoforms of Forkhead transcription factors, is highly expressed in insulin-responsive tissues, including pancreas, liver, skeletal muscle and adipose tissue, as well as in the skeleton. In all these tissues FoxO1 orchestrates the transcriptional cascades regulating glucose metabolism. Indeed, FoxO1 is a major target of insulin which inhibits its transcriptional activity via nuclear exclusion. In the pancreas, FoxO1 regulates β-cell formation and function by a balanced dual mode of action that suppresses β-cell proliferation but promotes survival. Hepatic glucose production is promoted and lipid metabolism is regulated by FoxO1 such that under insulin resistance they lead to hyperglycemia and dyslipidemia, two features of type 2 diabetes. In skeletal muscle FoxO1 maintains energy homeostasis during fasting and provides energy supply through breakdown of carbohydrates, a process that leads to atrophy and underlies glycemic control in insulin resistance. In a dual function, FoxO1 regulates energy and nutrient homeostasis through energy storage in white adipose tissue, but promotes energy expenditure in brown adipose tissue. In its most recently discovered novel role, FoxO1 acts as a transcriptional link between the skeleton and pancreas as well as other insulin target tissues to regulate energy homeostasis. Through its expression in osteoblasts it controls glucose metabolism, insulin sensitivity and energy expenditure. In a feedback mode of regulation, FoxO1 is also a target of insulin signaling in osteoblasts. Insulin suppresses activity of osteoblastic FoxO1 thus promoting beneficial effects of osteoblasts on glucose metabolism. The multiple actions of FoxO1 in all glucose-regulating organs, along with clinical studies suggesting that its glycemic properties are conserved in humans, establish this transcription factor as a master regulator of energy metabolism across species.

Defective recruitment, survival and proliferation of bone marrow-derived progenitor cells at sites of delayed diabetic wound healing in mice

AIMS/HYPOTHESIS

Bone marrow (BM)-derived endothelial progenitor cells (EPC) promote tissue healing and angiogenesis, whereas altered EPC biology may favour diabetic complications. We tested the hypothesis that diabetes impairs the contribution of BM-derived cells at sites of wound healing.

METHODS

Four weeks after induction of diabetes in C57BL/6 mice, hindlimb skin wounds were created and monitored by digital imaging and histology. Circulating EPCs were quantified by flow cytometry before and after wounding. In separate experiments, bone marrow from C57BL/6 mice constitutively producing green fluorescent protein (GFP) was transplanted into myeloablated wild-type mice before induction of diabetes. We quantified proliferation, apoptosis and endothelial differentiation of tissue GFP(+) cells. Net recruitment of GFP(+) cells was estimated by correcting the number of tissue GFP(+) cells at each time point for basal levels, apoptosis and proliferation rates.

RESULTS

Diabetes delayed wound healing, with reduced granulation tissue thickness and vascularity, and increased apoptosis. Circulating EPC levels were not modified by 4 week diabetes and/or skin wounding. BM-derived EPCs (GFP(+)vWf(+) [von Willebrand factor] cells) within the granulation tissue were significantly reduced in diabetic compared with control mice. BM-derived GFP(+) cells showed increased apoptosis and decreased proliferation in diabetic versus non-diabetic wound tissues. Estimated net recruitment of BM-derived GFP(+) cells was reduced on day 1 after wounding in diabetic mice.

CONCLUSIONS/INTERPRETATION

Diabetic-delayed wound healing was associated with defective recruitment, survival and proliferation of BM-derived progenitor cells. Local treatments aimed at restoring EPC homing and survival might improve tissue healing in diabetes.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Could thiamine pyrophosphate be a regulator of the nitric oxide synthesis in the endothelial cell of diabetic patients?

Thiamine (Vitamin B1) is considered an essential micronutrient for humans; its deficient intake brings about the Wernicke-Korsakoff syndrome (encephalopathy and psychosis) or beriberi (a neurological and cardiovascular disease). Once thiamine enters the cells it is phosphorylated by thiamine pyrophosphokinase (TPPK), and converted into the coenzyme thiamine pyrophosphate (TPP), the active form of thiamine. TPP is a relevant cofactor for transketolase (TK), α-ketoglutarate dehydrogenase (αKDH), and pyruvate dehydrogenase (PDH), all these enzymes are fundamental for glucose metabolism. Diabetes mellitus (DM), however, is considered both a deficient thiamine and deficient energy state, as a consequence of the limited TPP synthesis. Recent evidences have shown that the administration of thiamine or lipid-soluble derivatives, such as benfotiamine (developed to improve the bioavailability of thiamine), has positive effects in the diabetic patient (after thiamine is transformed into TPP). For this reason, administration of supplements with TPP in the diabetic patients is recommended to avoid complications, like neuropathy and nephropathy. It has been suggested that these beneficial effects are a consequence of the activation of TK (pentose pathway) or the PDH complex in mitochondria. Nitric oxide (NO) is synthesized by the endothelial cell and is also an important element for the viability and functionality of this cell type. However, in the DM patient, a deficient synthesis of NO has been reported. It is relevant to mention that recent evidences have led to propose mitochondrial activity as an important regulator of nitric oxide synthesis (ON). We consider that the exogenous administration of TPP facilitates the utilization of this molecule, regulating some metabolic processes such as phosphorylation of thiamine by TPPK, energy consumption (ATP), as well as mitochondrial activity, inducing eventually NO synthesis. If this is confirmed, the administration of TPP to the diabetic patient would provide additional protection to endothelial cells, reducing the risk of vascular damage, to which the diabetic patient is highly susceptible.

A fork in the path: Developing therapeutic inroads with FoxO proteins

Advances in clinical care for disorders involving any system of the body necessitates novel therapeutic strategies that can focus upon the modulation of cellular proliferation, metabolism, inflammation and longevity. In this respect, members of the mammalian forkhead transcription factors of the O class (FoxOs) that include FoxO1, FoxO3, FoxO4 and FoxO6 are increasingly being recognized as exciting prospects for multiple disorders. These transcription factors govern development, proliferation, survival and longevity during multiple cellular environments that can involve oxidative stress. Furthermore, these transcription factors are closely integrated with several novel signal transduction pathways, such as erythropoietin and Wnt proteins, that may influence the ability of FoxOs to act as a “double-edge sword” to sometimes promote cell survival, but at other times lead to cell injury. Here we discuss the fascinating but complex role of FoxOs during cellular injury and oxidative stress, progenitor cell development, fertility, angiogenesis, cardiovascular function, cellular metabolism and diabetes, cell longevity, immune surveillance and cancer.

The emerging relationship between regenerative medicine and physical therapeutics

Dramatic changes in the health care landscape over the next few decades undoubtedly will affect rehabilitation specialists' practice. In the multidisciplinary field of regenerative medicine, cell, tissue, or organ substitutes are used to enhance the healing potential of the body. Given that the restoration of normal functioning of injured or diseased tissues is expected to be the ultimate goal of these therapies, the future of regenerative medicine is, undeniably, tightly intertwined with that of rehabilitation. Rehabilitation specialists not only must be aware of cutting-edge medical advances as they relate to regenerative medicine but also must work closely with basic scientists to guide the development of clinically relevant protocols. The purposes of this article are to provide a current perspective on biological approaches to the management of musculoskeletal disorders and to highlight the needed integration of physical therapeutics with regenerative medicine.

Oxidative stress and diabetic complications

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.

Effects of a short-term exercise training on serum factors involved in ventricular remodelling in chronic heart failure patients

OBJECTIVES

We studied the effect of a short-term (3 weeks) exercise training program on the number of circulating CD34/KDR(+) endothelial progenitor cells (EPCs) and on serum levels of matrix metalloproteinases (MMPs) in chronic heart failure (CHF) patients as well as on serum capacity to foster colony forming units-endothelial cells (CFU-ECs) in vitro.

METHODS

Effectiveness of training was assessed by the 6-minute walking test (6MWT). Peripheral blood and serum were obtained from fourteen patients with CHF due to coronary artery disease before and after an inpatient aerobic exercise training program. At admission and at discharge we analysed circulating EPC number and serum levels of MMPs, TIMP-1 and TNF-α. The number and function of CFU-EC colonies were evaluated in cultures performed with serum obtained before and after training.

RESULTS

After training, distance walked at 6MWT and number of circulating CD34/KDR(+) cells increased (from 154 ± 27 to 233 ± 48 m; P<0.0001 and from 5 ± 3 to 9 ± 6 cells/ml P<0.05, respectively). Conversely, serum concentrations of MMP-1 and TIMP-1 decreased significantly (from 11.4 ± 2.4 to 6.3 ± 1.1 ng/ml, and from 320.4 ± 41.2 to 167.2 ± 12.6 ng/ml, respectively, both P<0.01), while MMP2/TIMP-1 and MMP-9/TIMP-1 ratios increased. Interestingly, we found increased CFU-EC proliferation in cultures performed with serum obtained after training.

CONCLUSIONS

Considering that both EPCs and MMPs might play a role in vascular remodeling, the increased number of EPCs and MMP activities observed in this study, suggest that the selected short-term exercise training could be a potential therapeutic strategy to rescue cardiac function in CHF patients.

Tumor necrosis factor-α regulates p27 kip expression and apoptosis in smooth muscle cells of human carotid plaques via forkhead transcription factor O1

Apoptosis of vascular smooth muscle cells (SMCs) is controlled by a balance between the effect of growth factors and cytokines, and is involved in plaque instability in advanced atherosclerotic lesions. Recently, we reported high levels of atheroma-associated cytokines, including tumor necrosis factor-α (TNF-α), in carotid plaques of symptomatic patients. These cytokines induce apoptosis of vascular SMCs, and thus could be responsible for plaque rupture, a clinically devastating event. In this study, we examined the effect of TNF-α on the cell cycle inhibitor p27(kip) and apoptosis of SMCs in human carotid plaques, and the underlying mechanism. Both Forkhead box subclass o1 (FoxO1) and p27(kip) were more strongly expressed in symptomatic than asymptomatic atherosclerotic plaques. TNF-α significantly induced the expression of FoxO1 in asymptomatic plaque SMCs in a dose- and time-dependent manner via JNK signaling pathway. TNF-α also induced phosphorylation of FoxO1, resulting in its cytoplasmic translocation/nuclear exclusion of transcription factors. The effect of TNF-α was blocked by the PI3K inhibitor, LY294002. Meanwhile, TNF-α not only induced the p27(kip) expression and cell cycle arrest in the G(0)-G(1) phase, but also enhanced caspase-3 activity and induced apoptosis in SMCs of asymptomatic plaques. However, the potential effect of TNF-α on the cell cycle inhibitor p27(kip) and apoptosis of SMCs was inhibited by siRNA against FoxO1 in asymptomatic patients. These data suggest the involvement of FoxO1 transcription factor in TNF-α-induced expression of a cell cycle regulatory protein and apoptosis of SMCs, thus regulating the stability of atherosclerotic plaques with carotid stenosis.

Endothelial and cardiac progenitors: boosting, conditioning and (re)programming for cardiovascular repair

Preclinical studies performed in cell culture and animal systems have shown the outstanding ability of stem cells to repair ischemic heart and lower limbs by promoting the formation of new blood vessels and new myocytes. In contrast, clinical studies of stem cell administration in patients with myocardial ischemia have revealed only modest, although promising, results. Basic investigations have shown the feasibility of adult cells reprogramming into pluripotent cells by defined factors, thus opening the way to the devise of protocols to ex vivo derive virtually unexhausted cellular pools. In contrast, cellular and molecular studies have indicated that risk factors limit adult-derived stem cell survival, proliferation and engraftment in ischemic tissues. The use of fully reprogrammed cells raises safety concerns; therefore, adult cells remain a primary option for clinicians interested in therapeutic cardiovascular repair. Pharmacologic approaches have been devised to restore the cardiovascular repair ability of failing progenitors from patients at risk. In the present contribution, the most advanced pharmacologic approaches to (re)program, boost, and condition endothelial and cardiac progenitor cells to enhance cardiovascular regeneration are discussed.

The defensive effect of benfotiamine in sodium arsenite-induced experimental vascular endothelial dysfunction

The present study has been designed to investigate the effect of benfotiamine, a thiamine derivative, in sodium arsenite-induced vascular endothelial dysfunction (VED) in rats. Sodium arsenite (1.5 mg(-1) kg(-1) day(-1) i.p., 2 weeks) was administered in rats to produce VED. The development of VED was assessed by employing isolated aortic ring preparation and estimating the serum and aortic concentrations of nitrite/nitrate. Further, the integrity of vascular endothelium in thoracic aorta was assessed by scanning electron microscopy. Moreover, the oxidative stress was assessed by estimating serum thiobarbituric acid reactive substances (TBARS) and aortic superoxide anion generation. The administration of sodium arsenite markedly produced VED by attenuating acetylcholine-induced endothelium-dependent relaxation, decreasing serum and aortic concentrations of nitrite/nitrate, and impairing the integrity of vascular endothelium. Further, sodium arsenite produced oxidative stress by increasing serum TBARS and aortic superoxide generation. The treatment with benfotiamine (25, 50, and 100 mg(-1) kg(-1) day(-1) p.o.) or atorvastatin (30 mg(-1) kg(-1) day(-1) p.o., a standard agent) prevented sodium arsenite-induced VED and oxidative stress. However, the beneficial effects of benfotiamine in preventing the sodium arsenite-induced VED were attenuated by co-administration with N-omega-nitro-L: -arginine methyl ester (L: -NAME) (25 mg(-1) kg(-1) day(-1), i.p.), an inhibitor of NOS. Thus, it may be concluded that benfotiamine reduces oxidative stress and activates endothelial nitric oxide synthase to enhance the generation and bioavailability of NO and subsequently improves the integrity of vascular endothelium to prevent sodium arsenite-induced experimental VED.