Role of oxidative stress in diabetes-mediated vascular dysfunction: unifying hypothesis of diabetes revisited

The Potential Impact of SGLT2-I in Diabetic Foot Prevention: Promising Pathophysiologic Implications, State of the Art, and Future Perspectives-A Narrative Review

The impact of diabetic foot (DF) on the healthcare system represents a major public health problem, leading to a considerable clinical and economic burden. The factors contributing to DF's development and progression are strongly interconnected, including metabolic causes, neuropathy, arteriopathy, and inflammatory changes. Sodium-glucose cotransporter 2 inhibitors (SGLT2-i), novel oral hypoglycemic drugs used as an adjunct to standard treatment, have recently changed the pharmacological management of diabetes. Nevertheless, data about the risk of limb amputation, discordant and limited to canagliflozin, which is currently avoided in the case of peripheral artery disease, have potentially discouraged the design of specific studies targeting DF. There is good evidence for the single immunomodulatory, neuroprotective, and beneficial vascular effects of SGLT2-i. Still, there is no clinical evidence about the early use of SGLT2-i in diabetic foot due to the lack of longitudinal and prospective studies proving the effect of these drugs without confounders. This narrative review aims to discuss the main evidence about the impact of SGLT2-i on the three complications of diabetes implicated in the development of DF, the state of the art, and the potential future implications.

Impaired microvascular insulin-dependent dilation in women with a history of gestational diabetes

Women with a history of gestational diabetes mellitus (GDM) have a significantly greater lifetime risk of developing cardiovascular disease and type 2 diabetes compared with women who had an uncomplicated pregnancy (HC). Microvascular endothelial dysfunction, mediated via reduced nitric oxide (NO)-dependent dilation secondary to increases in oxidative stress, persists after pregnancy complicated by GDM. We examined whether this microvascular dysfunction reduces insulin-mediated vascular responses in women with a history of GDM. We assessed in vivo microvascular endothelium-dependent vasodilator function by measuring cutaneous vascular conductance responses to graded infusions of acetylcholine (10-10-10-1 M) and insulin (10-8-10-4 M) in control sites and sites treated with 15 mM l-NAME [NG-nitro-l-arginine methyl ester; NO-synthase (NOS) inhibitor] or 5 mM l-ascorbate. We also measured protein expression of total endothelial NOS (eNOS), insulin-mediated eNOS phosphorylation, and endothelial nitrotyrosine in isolated endothelial cells from GDM and HC. Women with a history of GDM had reduced acetylcholine (P < 0.001)- and insulin (P < 0.001)-mediated dilation, and the NO-dependent responses to both acetylcholine (P = 0.006) and insulin (P = 0.006) were reduced in GDM compared with HC. Insulin stimulation increased phosphorylated eNOS content in HC (P = 0.009) but had no effect in GDM (P = 0.306). Ascorbate treatment increased acetylcholine (P < 0.001)- and insulin (P < 0.001)-mediated dilation in GDM, and endothelial cell nitrotyrosine expression was higher in GDM compared with HC (P = 0.014). Women with a history of GDM have attenuated microvascular vasodilation responses to insulin, and this attenuation is mediated, in part, by reduced NO-dependent mechanisms. Our findings further implicate increased endothelial oxidative stress in this microvascular insulin resistance.NEW & NOTEWORTHY Women who have gestational diabetes during pregnancy are at a greater risk for cardiovascular disease and type 2 diabetes in the decade following pregnancy. The mechanisms mediating this increased risk are unclear. Herein, we demonstrate that insulin-dependent microvascular responses are reduced in women who had gestational diabetes, despite the remission of glucose intolerance. This reduced microvascular sensitivity to insulin may contribute to increased cardiovascular disease and type 2 diabetes risk in these women.

Insulin Sensitivity of Adipocytes is Improved by Pomegranate Mesocarp Through Reduced Oxidative Stress and Inflammation

OBJECTIVE

Inflammatory phenomena and increase in oxidative stress in cell physiopathology progression render therapeutic strategies based on nutritional antioxidants necessary. It was thus aimed at assessing the effectiveness of the pomegranate mesocarp extract (PME) on differentiation of preadipocytes to adipocytes in the presence/absence of hydrogen peroxide (H2O2), a model mimicking insulin resistance.

METHOD

The effect of PME on lipid accumulation, protein expression of antioxidant, inflammatory and adipogenic biomarkers, reactive oxygen species production, activity of antioxidant enzymes and secretion of IL-6 has been evaluated during the differentiation of preadipocytes to adipocytes, in the presence or absence of H2O2.

RESULTS

H2O2 reduced the expression of the regulator of insulin sensitivity PPARγ and suppressed adipocyte differentiation. PME counteracted the effect of H2O2. The latter induced a higher level of fat accumulation by promoting the expressions of the adipogenic markers PPARγ, C/EBPα, FABP4 and CD36 as compared to the control and the H2O2-treated differentiating cells. During the progression of adipogenesis, highest increase (p < 0.05) in IL-6 secretion, by 3.16 and 3.85 folds, was observed on day 2 of differentiation in control and H2O2-treated cells, respectively, compared to day 0. PME significantly decreased (p < 0.01) the secretion of the cytokine in addition to suppressing the expression of NFκB. PME also prevented the reduction of superoxide dismutase, catalase and glutathione peroxidase activities that occurred during adipogenesis, by at most 33%, 119% and 42%, respectively.

CONCLUSION

These findings indicate that PME efficiently improves insulin sensitivity and can significantly counteract oxidative stress and inflammation.

Tadalafil versus pentoxifylline in the management of diabetic kidney disease: a randomized clinical trial

AIMS

To investigate the efficacy and safety of tadalafil (TAD) versus pentoxifylline (PTX) in the management of diabetic kidney disease (DKD). Some animal studies and clinical trials reported that tadalafil and pentoxifylline have a reducing effect on different blood glucose parameters and lipid profiles which contribute to progress the patients with diabetes mellitus (DM) to DKD.

METHODS

From February 2022 to March 2023, 90 patients with type 2 DM and DKD (micro-albuminuria) were enrolled in this randomized-controlled study. The patients were randomized into three equal groups: control group, TAD group, and PTX group. The three groups received traditional blood glucose lowering therapy + ramipril 10 mg PO. The TAD group also received tadalafil 20 mg PO every other day. The PTX group also received pentoxifylline 400 mg PO twice daily.

RESULTS

Both TAD and PTX groups produced statistically significant improvement in the primary outcomes by a significant reduction in Urinary albumin/creatinine ratio (UACR) which was pronounced by a reduction percentage of-47.47%, -53.73% respectively. In addition to a significant decrease in Hemoglobin A1C (HbA1c) (mmol/mol), Fasting blood glucose (FBG), 2-h postprandial blood glucose (2-h PPG) (p < 0.001). Only the PTX group showed a significant increase in Cr Cl and a significant decrease in S. Cr (p < 0.001). Only the TAD group showed a significant increase in high-density lipoprotein-cholesterol (HDL-C) (p < 0.001), while the PTX group showed a significant decrease in low-density lipoprotein-cholesterol (LDL-C) (p-value 0.011), and triglyceride (p-value 0.002). Both TAD and PTX groups showed a decrease in tumor necrosis factor-α (TNF-α) which was significant only in the PTX group (p < 0.001). There was a significant increase in malondialdehyde (MDA) (p < 0.001), and an increase in urinary neutrophil gelatinase-associated Lipocalin (uNGAL) (p-value 0.850, 0.014 respectively) which was significant only in the PTX group.

CONCLUSIONS

The use of tadalafil or pentoxifylline may serve as an effective adjuvant therapy for patients with diabetic kidney disease.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT05487755, July 25, 2022.

Impaired Melatonin Secretion, Oxidative Stress and Metabolic Syndrome in Night Shift Work

Metabolic syndrome has been associated in many studies with working in shifts. Even if the mechanistic details are not fully understood, forced sleep deprivation and exposure to light, as happens during night shifts, or irregular schedules with late or very early onset of the working program, lead to a sleep-wake rhythm misalignment, metabolic dysregulation and oxidative stress. The cyclic melatonin secretion is regulated by the hypothalamic suprachiasmatic nuclei and light exposure. At a central level, melatonin promotes sleep and inhibits wake-signals. Beside this role, melatonin acts as an antioxidant and influences the functionality of the cardiovascular system and of different metabolic processes. This review presents data about the influence of night shifts on melatonin secretion and oxidative stress. Assembling data from epidemiological, experimental and clinical studies contributes to a better understanding of the pathological links between chronodisruption and the metabolic syndrome related to working in shifts.

Diabetes Mellitus and the Kidneys

The pathomechanisms implicated in diabetic kidney disease in people are present in dogs and cats and, in theory, could lead to renal complications in companion animals with long-standing diabetes mellitus. However, these renal complications develop during a long period, and there is little to no clinical evidence that they could lead to chronic kidney disease in companion animals.

Metabolite Profiling of Antioxidant Rich Fractions of Punica granatum L. Mesocarp and CD36 Expression Regulation

OBJECTIVE

It was aimed at determining which polyphenolic compound(s) in pomegranate mesocarp extract (PME) is liable for the antioxidant, anti-glycation and anti-CD36 activities.

METHODS

The PME was fractionated using liquid-liquid extraction method. The fractions were tested for their polyphenolic content, antioxidant potency, anti-glycation activity and anti-CD36 potential. The metabolite compositions of PME and derived fractions were investigated in an untargeted manner using metabolomics in relation to its antioxidant and anti-glycation activities.

RESULTS

The ethyl acetate and n-butanol fractions of the pomegranate mesocarp demonstrated highest antioxidant and anti-glycation potencies. These fractions, represented by gallic and ellagic acids monomers, were enriched in tannins and phenolic acids. Orthogonal partial least squares discriminate analysis (OPLS-DA) modeling of ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) metabolite profiles from the different pomegranate mesocarp fractions indicated that gallic and ellagic acids were potential contributors to the antioxidant and anti-glycation effects of the pomegranate mesocarp. At cellular level, the polyphenolic-rich crude extract as well as the ethyl acetate, n-butanol and aqueous residual fractions suppressed the protein expression of CD36. The anti-CD36 activity of these extracts and fractions was attributed to the presence of punicalagin, the ellagitannins that occurred in equal amount in the different fractions.

CONCLUSION

This work demonstrated the protective effect of the non-edible part of the pomegranate fruit and showed that gallic and ellagic acids account for the antioxidant and anti-glycation activities while punicalagin is liable for the anti-CD36 activity of PME.

Skin Microhemodynamics and Mechanisms of Its Regulation in Type 2 Diabetes Mellitus

The review presents modern ideas about peripheral microhemodynamics, approaches to the ana-lysis of skin blood flow oscillations and their diagnostic significance. Disorders of skin microhemodynamics in type 2 diabetes mellitus (DM) and the possibility of their interpretation from the standpoint of external and internal interactions between systems of skin blood flow regulation, based on a comparison of couplings in normal and pathological conditions, including models of pathologies on animals, are considered. The factors and mechanisms of vasomotor regulation, among them receptors and signaling events in endothelial and smooth muscle cells considered as models of microvessels are discussed. Attention was drawn to the disturbance of Ca2+-dependent regulation of coupling between vascular cells and NO-dependent regulation of vasodilation in diabetes mellitus. The main mechanisms of insulin resistance in type 2 DM are considered to be a defect in the number of insulin receptors and impaired signal transduction from the receptor to phosphatidylinositol-3-kinase and downstream targets. Reactive oxygen species plays an important role in vascular dysfunction in hyperglycemia. It is assumed that the considered molecular and cellular mechanisms of microhemodynamics regulation are involved in the formation of skin blood flow oscillations. Parameters of skin blood microcirculation can be used as diagnostic and prognostic markers for assessing the state of the body.

SGLT2 inhibitors improve kidney function and morphology by regulating renal metabolic reprogramming in mice with diabetic kidney disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) worldwide. SGLT2 inhibitors are clinically effective in halting DKD progression. However, the underlying mechanisms remain unclear. The serum and kidneys of mice with DKD were analyzed using liquid chromatography with tandem mass spectrometry (LC–MS/MS)-based metabolomic and proteomic analyses. Three groups were established: placebo-treated littermate db/m mice, placebo-treated db/db mice and EMPA-treated db/db mice. Empagliflozin (EMPA) and placebo (10 mg/kg/d) were administered for 12 weeks. EMPA treatment decreased Cys-C and urinary albumin excretion compared with placebo by 78.60% and 57.12%, respectively (p < 0.001 in all cases). Renal glomerular area, interstitial fibrosis and glomerulosclerosis were decreased by 16.47%, 68.50% and 62.82%, respectively (p < 0.05 in all cases). Multi-omic analysis revealed that EMPA treatment altered the protein and metabolic profiles in the db/db group, including 32 renal proteins, 51 serum proteins, 94 renal metabolites and 37 serum metabolites. Five EMPA-related metabolic pathways were identified by integrating proteomic and metabolomic analyses, which are involved in renal purine metabolism; pyrimidine metabolism; tryptophan metabolism; nicotinate and nicotinamide metabolism, and glycine, serine and threonine metabolism in serum. In conclusion, this study demonstrated metabolic reprogramming in mice with DKD. EMPA treatment improved kidney function and morphology by regulating metabolic reprogramming, including regulation of renal reductive stress, alleviation of mitochondrial dysfunction and reduction in renal oxidative stress reaction.

Oxidative stress contributes to reductions in microvascular endothelial- and nitric oxide-dependent dilation in women with a history of gestational diabetes

Women with a history of gestational diabetes mellitus (GDM) are twice as likely to develop cardiovascular disease and ~7x as likely to develop type II diabetes as their age-matched counterparts. However, the mechanism(s) mediating these associations remain unclear. We hypothesized that endothelium- and NO-dependent dilation would be attenuated through oxidant stress mechanisms in the microvasculature of women with a history of GDM compared to control women with a history of uncomplicated pregnancy (HC). Ten HC (35±4yrs) and 10 GDM (34±4yrs) underwent a standard local heating protocol (42°C; 0.1°C·s^-1). Two intradermal microdialysis fibers were placed in the ventral forearm for local delivery of lactated Ringer's (control), or 5mM L-ascorbate. After full expression of the local heating response, 15mM N^G-nitro-L-arginine methyl ester NO synthase-inhibition) was perfused. Red cell flux was measured continuously by laser-Doppler flowmetry and cutaneous vascular conductance (CVC=flux/MAP) was standardized to maximum (%CVCmax; 28mM SNP + 43°C). Urine albumin:creatinine ratio (ACR) was measured. GDM had attenuated endothelium-dependent (GDM: 67±7 vs. HC: 90±4%CVCmax; p<0.001) and NO-dependent (GDM: 54±7 vs. HC: 71±3%; p=0.001) dilation at the control site and tended to have higher urine ACR (p=0.06). Both endothelium-dependent (r²=0.53, p=0.02) and NO-dependent (r²=0.56, p=0.01) dilation were related to urine ACR in GDM. L-ascorbate perfusion improved endothelium-dependent (82±5%CVCmax; p=0.03 vs. control) and NO-dependent (68±5%; p=0.02 vs. control) dilation in GDM but had no effect in HC (p>0.05). Otherwise healthy women with a history of GDM have attenuated microvascular endothelial function and this dysfunction is mediated, in part, by oxidative stress.

Shape and stiffness memory ionogels with programmable pressure-resistance response

Flexible pressure sensors usually require functional materials with both mechanical compliance and appropriate electrical performance. Most sensors based on materials with limited compressibility can hardly balance between high sensitivity and broad pressure range. Here, we prepare a heterophasic ionogel with shape and stiffness memory for adaptive pressure sensors. By combining the microstructure alignment for stiffness changing and shape memory micro-inclusions for stiffness fixing, the heterophasic ionogels reveal tunable compressibility. This controllable pressure-deformation property of the ionogels results in the pressure sensors' programmable pressure-resistance behavior with tunable pressure ranges, varied detection limits, and good resolution at high pressure. Broad pressure ranges to 220 and 380 kPa, and tunable detection limit from 120 to 330 and 950 Pa are realized by the stiffness memory ionogel sensors. Adaptive detection is also brought out to monitor tiny pressure changes at low stiffness and distinguish different human motions at high stiffness. Using shape and stiffness memory materials in pressure sensors is a general design to achieve programmable performance for more complex application scenarios.

Characterization of the Phytochemical Composition and Bioactivities of Anacyclus maroccanus Ball. and Anacyclus radiatus Loisel Aerial Parts: Preliminary Evidence for the Possible Development of Moroccan Plants

In the present study, the phytochemical composition and bioactivities of A. maroccanus (AM) and A. radiatus (AR), two ecotypes collected in the Demnate road and Essaouira regions, respectively, were studied to highlight a pharmacological interest and to enable possible pharmaceutical development. To this end, methanolic and ethyl acetate extracts were prepared for each ecotype by fractionation; next, their phytochemical composition was evaluated by spectrophotometric and chromatographic analysis. Moreover, in line with the available evidence for Anacyclus spp. and their traditional use, a screening of bioactivities, including antioxidant, hypoglycemic, antiglycative, chelating, and antibacterial activities, was performed. The extracts were characterized by high amounts of polyphenols, tannins, and flavonoids, especially in the methanolic extracts; these samples were also enriched in carotenoids despite a lower chlorophyll content. Chlorogenic acid and rutin were the major identified compounds. The extracts also showed interesting hypoglycemic, antiglycative, and antibacterial properties, although with differences in efficacy and potency. Present results provide more scientific basis to the ethnopharmacological uses of Anacyclus spp. and suggest a further interest in AM and AR ecotypes as natural sources of bioactive compounds and/or phytocomplexes for possible pharmaceutical and nutraceutical developments.

Effects of SGLT2 Inhibitors on Atherosclerosis: Lessons from Cardiovascular Clinical Outcomes in Type 2 Diabetic Patients and Basic Researches

Atherosclerosis-caused cardiovascular diseases (CVD) are the leading cause of mortality in type 2 diabetes mellitus (T2DM). Sodium-glucose cotransporter 2 (SGLT2) inhibitors are effective oral drugs for the treatment of T2DM patients. Multiple pre-clinical and clinical studies have indicated that SGLT2 inhibitors not only reduce blood glucose but also confer benefits with regard to body weight, insulin resistance, lipid profiles and blood pressure. Recently, some cardiovascular outcome trials have demonstrated the safety and cardiovascular benefits of SGLT2 inhibitors beyond glycemic control. The SGLT2 inhibitors empagliflozin, canagliflozin, dapagliflozin and ertugliflozin reduce the rates of major adverse cardiovascular events and of hospitalization for heart failure in T2DM patients regardless of CVD. The potential mechanisms of SGLT2 inhibitors on cardioprotection may be involved in improving the function of vascular endothelial cells, suppressing oxidative stress, inhibiting inflammation and regulating autophagy, which further protect from the progression of atherosclerosis. Here, we summarized the pre-clinical and clinical evidence of SGLT2 inhibitors on cardioprotection and discussed the potential molecular mechanisms of SGLT2 inhibitors in preventing the pathogenesis of atherosclerosis and CVD.

A personalised diet study: The interaction between ApoA2 -265T > C polymorphism and dietary inflammatory index on oxidative and inflammatory markers and lipid profile in patients with type 2 diabetes mellitus: A cross-sectional study

BACKGROUND

This study aimed to investigate the interaction between dietary inflammatory index (DII) and apolipoproteinA2 265T > C (ApoA2 -265T > C) polymorphism on inflammatory and oxidative markers and lipid profile in type 2 diabetes mellitus (T2DM) patients.

METHODS

In this cross-sectional study, 157 patients with T2DM were recruited. A food-frequency questionnaire was used for DII calculation. Inflammatory, oxidative and lipid biomarkers were measured. Real-time polymerase chain reaction (PCR) method was used for ApoA2 genotyping determination.

RESULTS

In the current study, serum 8-iso-PGF2α and CRP were significantly higher, and serum SOD activity was significantly lower in subjects with CC genotype than TT homozygous in both crude and adjusted (for DII and AAs intake) models. Also, C-allele carriers compared with people with TT genotype had lower PTX3 in both models. In addition, serum TG level was significantly higher in TC genotype than TT homozygous in adjusted model. Moreover, subjects with CC homozygous and high DII level had significantly higher 8-iso-PGF2α level compared to those with TT genotype and low DII (reference group) in adjusted (for BMI, age, sexuality and AAs intake) model. Our results also showed that in TC genotypes with low DII and CC homozygous with both low and high DII, PTX3 concentrations were significantly lower than the reference group. In addition, CC carriers with low DII had significantly higher CRP level compared to the reference group. Moreover, our results reported significant higher TG in TC genotype with low DII and also higher total cholesterol level in CC genotype with low DII than the reference group.

CONCLUSION

These findings indicate that CC genotype might predict higher inflammatory and oxidative status level compared to T allele carriers. An inflammatory diet may accelerate oxidative stress in subjects with CC genotype. However, the association between APOA2 -265T > C polymorphism and inflammation and lipid profile is presented less modifiable by DII.

Relationship Between Autophagy and Metabolic Syndrome Characteristics in the Pathogenesis of Atherosclerosis

Atherosclerosis is the main cause of mortality in metabolic-related diseases, including cardiovascular disease and type 2 diabetes (T2DM). Atherosclerosis is characterized by lipid accumulation and increased inflammatory cytokines in the vascular wall, endothelial cell and vascular smooth muscle cell dysfunction and foam cell formation initiated by monocytes/macrophages. The characteristics of metabolic syndrome (MetS), including obesity, glucose intolerance, dyslipidemia and hypertension, may activate multiple mechanisms, such as insulin resistance, oxidative stress and inflammatory pathways, thereby contributing to increased risks of developing atherosclerosis and T2DM. Autophagy is a lysosomal degradation process that plays an important role in maintaining cellular metabolic homeostasis. Increasing evidence indicates that impaired autophagy induced by MetS is related to oxidative stress, inflammation, and foam cell formation, further promoting atherosclerosis. Basal and mild adaptive autophagy protect against the progression of atherosclerotic plaques, while excessive autophagy activation leads to cell death, plaque instability or even plaque rupture. Therefore, autophagic homeostasis is essential for the development and outcome of atherosclerosis. Here, we discuss the potential role of autophagy and metabolic syndrome in the pathophysiologic mechanisms of atherosclerosis and potential therapeutic drugs that target these molecular mechanisms.

The Prophylactic Activity of Punica granatum L. mesocarp Protects Preadipocytes against Ribosylated BSA-Induced Toxicity

OBJECTIVE

It was aimed at comparing the glycating capacities of glucose and ribose in bovine serum albumin (BSA) and anti-glycation activity of pomegranate mesocarp extract (PME). The protective mechanism of PME against ribosylated BSA (BSA_RIB)-induced toxicity was also investigated.

METHODS

BSA was incubated with glucose or ribose in the presence or absence of PME for 15 days. In preadipocytes pretreated with PME, cell viability, ROS production, lipid peroxidation and mitochondrial membrane potential were investigated following 1, 6, 12, 18 and 24 h exposure to BSA_RIB. Nuclear translocation of NFκB was assessed at 1 h and 24 h of BSA_RIB insult. Accumulation of oxidized proteins, activities of intrinsic antioxidant enzymes and IL-6 secretion were also determined after 24 h exposure to BSA_RIB.

RESULTS

Ribose was a harsher glycating agent as compared to glucose and PME showed strong anti-glycation activity by suppressing (P < 0.05) the increase in levels of fluorescent AGEs, Amadori products, protein carbonyl and advanced oxidation protein products (AOPP). In preadipocytes, BSA_RIB potentiated pro-apoptotic activity by inhibiting the nuclear translocation of NFκB. BSA_RIB induced a time dependent decrease in cell viability, which was significantly suppressed (P < 0.05) by PME. The extract also significantly reduced (P < 0.05) the time dependent increase in ROS level and associated lipid peroxidation as well as loss in mitochondrial membrane potential caused by BSA_RIB. PME also counteracted the BSA_RIB-induced accumulation of oxidized proteins, decrease in intrinsic antioxidant activity and IL-6 over-secretion.

CONCLUSIONS

PME showed anti-glycation activity and afforded protection against BSA_RIB-induced toxicity, oxidative stress and inflammation in preadipocytes.

Endothelial response to glucose: dysfunction, metabolism, and transport

The endothelial cell response to glucose plays an important role in both health and disease. Endothelial glucose-induced dysfunction was first studied in diabetic animal models and in cells cultured in hyperglycemia. Four classical dysfunction pathways were identified, which were later shown to result from the common mechanism of mitochondrial superoxide overproduction. More recently, non-coding RNA, extracellular vesicles, and sodium-glucose cotransporter-2 inhibitors were shown to affect glucose-induced endothelial dysfunction. Endothelial cells also metabolize glucose for their own energetic needs. Research over the past decade highlighted how manipulation of endothelial glycolysis can be used to control angiogenesis and microvascular permeability in diseases such as cancer. Finally, endothelial cells transport glucose to the cells of the blood vessel wall and to the parenchymal tissue. Increasing evidence from the blood-brain barrier and peripheral vasculature suggests that endothelial cells regulate glucose transport through glucose transporters that move glucose from the apical to the basolateral side of the cell. Future studies of endothelial glucose response should begin to integrate dysfunction, metabolism and transport into experimental and computational approaches that also consider endothelial heterogeneity, metabolic diversity, and parenchymal tissue interactions.

Unfolding Nrf2 in diabetes mellitus

In spite of much awareness, diabetes mellitus continues to remain one of major reasons for mortality and morbidity rate all over the globe. Free radicals cause oxidative stress which is responsible for causing diabetes. The recent advancements in elucidation of ARE/keap1/Nrf2 pathway can help in better understanding of diabetes mellitus. Various clinical trials and animal studies have shown the promising effect of Nrf2 pathway in reversing diabetes by counteracting with the oxidative stress produced. The gene is known to dissociate from Keap1 on coming in contact with such stresses to show preventive and prognosis effect. The Nrf2 gene has been marked as a molecular player in dealing with wide intracellular as well as extracellular cellular interactions in different diseases. The regulation of this gene gives some transcription factor that contain antioxidant response elements (ARE) in their promoter region and thus are responsible for encoding certain proteins involved in regulation of metabolic and detoxifying enzymes.

The Role of Alpha-lipoic Acid Supplementation in the Prevention of Diabetes Complications: A Comprehensive Review of Clinical Trials

Alpha-lipoic acid (ALA) is a substantial antioxidant in the prevention of diabetes and diabetes complications. It can regenerate other antioxidants like vitamin E, vitamin C, Coenzyme Q10 and glutathione and is often known as a universal antioxidant. Antioxidants play a role in diabetes treatment due to hyperglycemia-induced stimulation of the polyol pathway and formation of advanced glycation end products (AGE) and reactive oxygen species (ROS). Clinical trials examining alpha-lipoic acid supplementation on diabetic neuropathy, nephropathy, cardiomyopathy and erectile dysfunction display positive results, particularly in pain amelioration in neuropathy, asymmetric dimethylarginine reductions in nephropathy and improved oscillatory potential and contrast sensitivity in retinopathy. In diabetic cardiomyopathy (DCM), ALA offers protection through inhibition of NF-kB activation, reduction of fas-ligand and decrease in matrix metalloproteinase-2. This comprehensive review summarises and provides an understanding of the importance of alpha- lipoic acid supplementation to prevent diabetes complications.

Modified kinetics of generation of reactive species in peripheral blood of patients with type 2 diabetes

Level of reactive species in blood is an important pathogenic factor in diabetes mellitus leading to dysfunctions of vascular endothelial and smooth muscle cells and coagulation system abnormality. A massive release of reactive species (respiratory burst), catalyzed by NADPH oxidase in blood phagocytes, is not well understood in diabetes. The work aimed to study kinetics of response to microbial particles in blood to specify changes in regulatory mechanisms of generation of reactive species in patients with type 2 diabetes. Production of reactive species in blood and isolated granulocytes was measured by luminol-dependent chemiluminescence. Respiratory burst was initiated by serum opsonized zymosan in blood samples and phorbol ester in cell samples. Kinetic parameters were calculated from experimental kinetic curves of chemiluminescence intensity. ROC curve analysis and mathematical modeling were used to reveal the most significant predictors and clarify specific mechanisms of NADPH oxidase activation. It was shown that kinetic parameters of response to opsonized zymosan (lag-time, response rate, amplitude, production of reactive species) were higher in blood of patients than controls. Amplitude and response rate were the most statistically significant predictors for distinguishing patients and controls at high glucose. It indicated NADPH oxidase activation was the target of hyperglycemia. Mathematical modeling showed hyperglycemia increased stability of NADPH oxidase complex, decreased synchronization of its assembling and elevated neutrophil capacity to phagocytosis in patients. Weak or no dependence of response kinetics on ionomycin concentration was shown in patients indicating changed Ca²⁺-dependent mechanism of NADPH oxidase activation. Hyperglycemia in type 2 diabetes causes disturbances in mechanisms of NADPH oxidase activation associated with both phagocytosis and the state of intracellular signaling systems, including Ca²⁺-dependent. We suggest that NADPH oxidase in blood granulocytes can be a promising target for clinical intervention improving management of diabetic complications associated with inflammation.

Klotho ameliorates diabetic nephropathy via LKB1-AMPK-PGC1α-mediated renal mitochondrial protection

Diabetic nephropathy (DN) is associated with renal mitochondrial injury and decreased renal klotho expression. Klotho is known as an aging suppressor, and mitochondrial dysfunction is the hallmark of aging. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) is a master regulator of mitochondrial biogenesis, and adenosine monophosphate-activated protein kinase (AMPK) is known as a guardian of mitochondria. Here, we report that recombinant soluble klotho protein (rKL) protects against DN in db/db mice via PGC1α-AMPK-mediated mitochondrial recovery in the kidney. We injected rKL into db/db and db/m mice for 8 weeks and collected the serum and kidney tissue. We treated murine renal tubular cells with rKL in vitro, with and without exposure to 30 mM high glucose (HG). rKL treatment ameliorated major disorders from diabetes, such as obesity, hyperglycemia, and intrarenal reactive oxygen species (ROS) generation, in db/db mice. rKL also diminished albuminuria, recovered renal proximal tubular mitochondria, increased renal p-AMPK and PGC1α, and down-regulated mTOR/TGF-β in db/db mice. In S1 mouse proximal tubular cells, rKL treatment ameliorated HG-mediated cellular and mitochondrial damage and enhanced oxidative phosphorylation, with an increase in PGC1α-AMPK-induced mitochondrial recovery. Our data suggest that klotho exerts a mitochondrial protective effect in diabetic kidney disease by inducing AMPK-PGC1α expression.

The ERM Complex: A New Player Involved in Diabetes-induced Vascular Leakage

BACKGROUND

Microvascular complications remain an important cause of morbidity in diabetic patients, and they are associated with a significant economic burden for healthcare systems. Vascular leakage is one of the earlier hallmarks in diabetic microvascular complications. Ezrin, Radixin and Moesin (ERM) proteins have recently been involved in vascular dysfunction under the effect of molecular mediators of diabetes complications. In this review, we will present the available evidence regarding the role of these proteins in vascular leakage and their putative implication in diabetic microvascular complications.

METHODS AND RESULTS

A comprehensive literature search of the electronic MEDLINE database was performed between November 2017 and January 2018. As a result, 36 articles have been reviewed and discussed.

DISCUSSION

ERM proteins are cytoskeleton-membrane linkers, and when activated in endothelial cells are able to induce cytoskeleton reorganization in stress fibers leading to the disassembly of focal adhesions and the formation of paracellular gaps which result in an increase of vascular permeability. The activation of these proteins is induced by mediators involved in diabetic complications such as PKC activation, TNF-α, AGEs and oxidative stress. In conclusion, ERMs play an essential role in endothelium homeostasis and can be envisaged as a new therapeutic molecular target for preventing or arresting diabetes-induced vascular leakage.

Associated Targets of the Antioxidant Cardioprotection of Ganoderma lucidum in Diabetic Cardiomyopathy by Using Open Targets Platform: A Systematic Review

Even with substantial advances in cardiovascular therapy, the morbidity and mortality rates of diabetic cardiomyopathy (DCM) continually increase. Hence, a feasible therapeutic approach is urgently needed. Objectives. This work is aimed at systemically reviewing literature and addressing cell targets in DCM through the possible cardioprotection of G. lucidum through its antioxidant effects by using the Open Targets Platform (OTP) website. Methods. The OTP website version of 19.11 was accessed in December 2019 to identify the studies in DCM involving G. lucidum. Results. Among the 157 cell targets associated with DCM, the mammalian target of rapamycin (mTOR) was shared by all evidence, drug, and text mining data with 0.08 score association. mTOR also had the highest score association 0.1 with autophagy in DCM. Among the 1731 studies of indexed PubMed articles on G. lucidum published between 1985 and 2019, 33 addressed the antioxidant effects of G. lucidum and its molecular signal pathways involving oxidative stress and therefore were included in the current work. Conclusion. mTOR is one of the targets by DCM and can be inhibited by the antioxidative properties of G. lucidum directly via scavenging radicals and indirectly via modulating mTOR signal pathways such as Wnt signaling pathway, Erk1/2 signaling, and NF-κB pathways.

Flavonoids Activation of the Transcription Factor Nrf2 as a Hypothesis Approach for the Prevention and Modulation of SARS-CoV-2 Infection Severity

The Nrf2-Keap1-ARE pathway is the principal regulator of antioxidant and phase II detoxification genes. Its activation increases the expression of antioxidant and cytoprotective proteins, protecting cells against infections. Nrf2 modulates virus-induced oxidative stress, ROS generation, and disease pathogenesis, which are vital in the viral life cycle. During respiratory viral infections, such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an inflammatory process, and oxidative stress of the epithelium lining cells activate the transcription factor Nrf2, which protects cells from oxidative stress and inflammation. Nrf2 reduces angiotensin-converting enzyme 2 (ACE2) receptors expression in respiratory epithelial cells. SARS-CoV2 has a high affinity for ACE2 that works as receptors for coronavirus surface spike glycoprotein, facilitating viral entry. Disease severity may also be modulated by pre-existing conditions, such as impaired immune response, obesity, and age, where decreased level of Nrf2 is a common feature. Consequently, Nrf2 activators may increase Nrf2 levels and enhance antiviral mediators' expression, which could initiate an "antiviral state", priming cells against viral infection. Therefore, this hypothesis paper describes the use of flavonoid supplements combined with vitamin D3 to activate Nrf2, which may be a potential target to prevent and/or decrease SARS-CoV-2 infection severity, reducing oxidative stress and inflammation, enhancing innate immunity, and downregulating ACE2 receptors.

Antioxidant dressing therapy versus standard wound care in chronic wounds (the REOX study): study protocol for a randomized controlled trial

Background

A wound that does not heal in the orderly stages of the healing process or does not heal within 3 months is considered a chronic wound. Wound healing is impaired when the wound remains in the inflammatory stage for too long. A range of factors can delay the healing process: imbalance between proteases and protease inhibitors in the wound bed; bacterial colonization and the presence of biofilm; and oxidative stress. Recently, wound management has improved significantly. A new antioxidant dressing has been developed, which combines an absorbent matrix obtained from locust bean gum galactomannan and a hydration solution with curcumin and N-acetylcysteine. This dressing combines the advantages of moist healing in exudate management and free radical neutralization, achieving wound reactivation. The primary aim of this study is to compare the effect of the antioxidant dressing on chronic wound healing against the use of a standard wound dressing in patients with hard-to-heal wounds.

Methods

We will conduct a multicentre, single-blind, randomized controlled trial with parallel groups. Participants will be selected from three primary public health care centres located in Andalucía (southern Spain). Patients will be randomized into an intervention group (antioxidant dressing) or a control group (standard wound dressing). Assessments will be carried out at weeks 2, 4, 6 and 8. Follow-up will be for a period of 8 weeks or until complete healing if this occurs earlier.

Discussion

The findings from this study should provide scientific evidence on the efficacy of the antioxidant dressing as an alternative for the treatment of chronic wounds. This study fills some of the gaps in the existing knowledge about patients with hard-to-heal wounds.

Trial registration

ClinicalTrials.gov: NCT03934671. Registered on 2 May 2019.

Use of Chlorogenic Acid against Diabetes Mellitus and Its Complications

Chlorogenic acid (CA) is a phenolic compound commonly found in human plant-based diets. CA is the main component of many traditional Chinese medicine preparations, and in recent years, it has been found to have hypoglycemic, hypolipidemic, anti-inflammatory, antioxidant, and other pharmacological properties. Specifically, CA relieves the effects of, and prevents, diabetes mellitus (DM). In addition, CA is also beneficial against complications arising from DM, such as diabetic nephropathy (DN), diabetic retinopathy (DR), and diabetic peripheral neuropathy (DPN). Herein, we review the use of CA in the prevention and treatment of DM and its complications, providing a background for further research and medical uses.

A Translational In Vivo and In Vitro Metabolomic Study Reveals Altered Metabolic Pathways in Red Blood Cells of Type 2 Diabetes

Clinical parameters used in type 2 diabetes mellitus (T2D) diagnosis and monitoring such as glycosylated haemoglobin (HbA1c) are often unable to capture important information related to diabetic control and chronic complications. In order to search for additional biomarkers, we performed a pilot study comparing T2D patients with healthy controls matched by age, gender, and weight. By using ¹H-nuclear magnetic resonance (NMR) based metabolomics profiling of red blood cells (RBCs), we found that the metabolic signature of RBCs in T2D subjects differed significantly from non-diabetic controls. Affected metabolites included glutathione, 2,3-bisphophoglycerate, inosinic acid, lactate, 6-phosphogluconate, creatine and adenosine triphosphate (ATP) and several amino acids such as leucine, glycine, alanine, lysine, aspartate, phenylalanine and tyrosine. These results were validated by an independent cohort of T2D and control patients. An analysis of the pathways in which these metabolites were involved showed that energetic and redox metabolism in RBCs were altered in T2D, as well as metabolites transported by RBCs. Taken together, our results revealed that the metabolic profile of RBCs can discriminate healthy controls from T2D patients. Further research is needed to determine whether metabolic fingerprint in RBC could be useful to complement the information obtained from HbA1c and glycemic variability as well as its potential role in the diabetes management.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

Overexpression of calcitonin gene-related peptide protects mouse cerebral microvascular endothelial cells from high-glucose-induced damage via ERK/HIF-1/VEGF signaling

In the diabetic brain, hyperglycemia damages the cerebrovasculature and impairs neurovascular crosstalk. Calcitonin gene-related peptide (CGRP) is an important neuropeptide that is active in the vascular system. In this study, we aimed to investigate whether CGRP is involved in the high-glucose-induced damage in mouse cerebral microvascular endothelial (b.END3) cells and the possible mechanism in vitro. The overexpression of CGRP by lentiviral transduction inhibited cell apoptosis but not proliferation. In contrast to the promoting of angiogenesis and migration under normal glucose, CGRP inhibited hyperglycemia-induced tube formation but had no effect on migration. Calcitonin gene-related peptide partly reduced the increased level of intracellular reactive oxygen species (ROS) and altered nitric oxide synthase mRNA expression. Furthermore, CGRP suppressed the increased HIF-1α/VEGF-A expression and the phosphorylation of ERK1/2 in hyperglycemia. The ERK inhibitor U0126 showed similar inhibition of cell apoptosis, tube formation and HIF-1α/VEGF expression as that exhibited by lenti-CGRP. These findings demonstrate the protective role of CGRP overexpression against high-glucose-induced cerebrovascular changes in b.END3 cells, possibly through the inhibition of ERK/HIF-1/VEGF signaling.

Endothelial Toxicity of High Glucose and its by-Products in Diabetic Kidney Disease

Alterations of renal endothelial cells play a crucial role in the initiation and progression of diabetic kidney disease. High glucose per se, as well as glucose by-products, induce endothelial dysfunction in both large vessels and the microvasculature. Toxic glucose by-products include advanced glycation end products (AGEs), a group of modified proteins and/or lipids that become glycated after exposure to sugars, and glucose metabolites produced via the polyol pathway. These glucose-related endothelio-toxins notably induce an alteration of the glomerular filtration barrier by increasing the permeability of glomerular endothelial cells, altering endothelial glycocalyx, and finally, inducing endothelial cell apoptosis. The glomerular endothelial dysfunction results in albuminuria. In addition, high glucose and by-products impair the endothelial repair capacities by reducing the number and function of endothelial progenitor cells. In this review, we summarize the mechanisms of renal endothelial toxicity of high glucose/glucose by-products, which encompass changes in synthesis of growth factors like TGF-β and VEGF, induction of oxidative stress and inflammation, and reduction of NO bioavailability. We finally present potential therapies to reduce endothelial dysfunction in diabetic kidney disease.

Hypoglycemic, Antiglycation, and Cytoprotective Properties of a Phenol-Rich Extract From Waste Peel of Punica granatum L. var. Dente di Cavallo DC2

Pomegranate peel is a natural source of phenolics, claimed to possess healing properties, among which are antioxidant and antidiabetic. In the present study, an ethyl acetate extract, obtained by Soxhlet from the peel of Dente di Cavallo DC2 pomegranate (PGE) and characterized to contain 4% w/w of ellagic acid, has been evaluated for its hypoglycemic, antiglycation, and antioxidative cytoprotective properties, in order to provide possible evidence for future nutraceutical applications. The α-amylase and α-glucosidase enzyme inhibition, interference with advanced glycation end-products (AGE) formation, and metal chelating abilities were studied. Moreover, the possible antioxidant cytoprotective properties of PGE under hyperglycemic conditions were assayed. Phenolic profile of the extract was characterized by integrated chromatographic and spectrophotometric methods. PGE resulted able to strongly inhibit the tested enzymes, especially α-glucosidase, and exerted chelating and antiglycation properties. Also, it counteracted the intracellular oxidative stress under hyperglycemic conditions, by reducing the levels of reactive oxygen species and total glutathione. Among the identified phenolics, rutin was the most abundant flavonoid (about 4 % w/w). Present results suggest PGE to be a possible remedy for hyperglycemia management and encourage further studies to exploit its promising properties.

Mechanism of TangGanJian on nonalcoholic fatty liver disease with type 2 diabetes mellitus

CONTEXT

TangGanJian (TGJ) has a curative effect in the clinical treatment of nonalcoholic fatty liver disease (NAFLD) with type 2 diabetes mellitus (T2DM), while the mechanism involved in the treatment process remains unclear.

OBJECTIVE

This study details the mechanism of TGJ on the treatment of NAFLD with T2DM.

MATERIALS AND METHODS

NAFLD was induced in T2DM rat model. Male Wistar rats were assigned into six groups: Group I (control), Group II (model), Group III (pioglitazone, 0.5 mg/kg), Group IV (high dose of TGJ, 24.8 g/kg), Group V (middle dose of TGJ, 12.4 g/kg) and Group VI (low dose of TGJ, 6.2 g/kg). All rats in each group were treated with the corresponding drugs by gavage for 8 weeks. Haematoxylin and eosin analysis was conducted. The indicators of inflammatory and oxidative stress were analysed utilizing one-way ANOVA.

RESULTS

The contents of TNF-α (15.794 ± 3.302 pg/mL), IL-6 (76.801 ± 8.491 pg/mL), IL-1β (100.101 ± 13.150 pg/mL), CRP (1.052 ± 0.079 pg/mL) and MDA (3.972 ± 0.159 pg/mL) were obviously elevated in NAFLD with T2DM rats compared to controls. Except for the IL-6, the levels of other markers declined in a dose-dependent manner after treatment with TGJ. The SOD (14.139 ± 1.479 U/mgprot) and GSH-PX (81.511 ± 5.276 U/mgprot) levels significantly decreased in NAFLD with T2DM rats, while the levels of these indicators increased after treatment with TGJ.

CONCLUSIONS

TGJ may be a therapy for the NAFLD with T2DM rats by modulating the inflammatory response and the oxidative stress capacity.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Beneficial effects of cherry consumption as a dietary intervention for metabolic, hepatic and vascular complications in type 2 diabetic rats

Background

Oxidative stress (OS) plays an important role in type 2 diabetes (T2D) pathogenesis and its complications. New therapies target natural antioxidants as an alternative and/or supplemental strategy to prevent and control them. Our previous chemical and biological studies highlighted the important antioxidant activities of cherries, among other fruits and vegetables, thus we aimed to determine in vivo effects of 2-month long cherry consumption using a high-fat/high-fructose (HFHF) model of diabetic-rats (Lozano et al. in Nutr Metab 13:15, 2016).

Methods

After 2 months of HFHF, male Wistar rats were divided into: HFHF and HFHF enriched in cherry (nutritional approach) or standard diet ND (lifestyle measures) and ND plus cherry during 2 months. Metabolic, lipidic, oxidative parameters were quantified. Tissues (liver, pancreas and vessels) OS were assessed and hepatic (steatosis, fibrosis, inflammation) and vascular (endothelial dysfunction) complications were characterized.

Results

T2D was induced after 2 months of HFHF diet, characterized by systemic hyperglycaemia, hyperinsulinemia, glucose intolerance, dyslipidaemia, hyperleptinemia, and oxidative stress associated with endothelial dysfunction and hepatic complications. Cherry consumption for 2 months, in addition to lifestyle measures, in T2D-rats decreased and normalized the systemic disturbances, including oxidative stress complications. Moreover, in the vessel, cherry consumption decreased oxidative stress and increased endothelial nitric oxide (NO) synthase levels, thus increasing NO bioavailability, ensuring vascular homeostasis. In the liver, cherry consumption decreased oxidative stress by inhibiting NADPH oxidase subunit p22phox expression, nuclear factor erythroid-2 related factor 2 (Nrf2) degradation and the formation of reactive oxygen species. It inhibited the activation of sterol regulatory element-binding proteins (1c and 2) and carbohydrate-responsive element-binding protein, and thus decreased steatosis as observed in T2D rats. This led to the improvement of metabolic profiles, together with endothelial and hepatic function improvements.

Conclusion

Cherry consumption normalized vascular function and controlled hepatic complications, thus reduced the risk of diabetic metabolic disorders. These results demonstrate that a nutritional intervention with a focus on OS could prevent and/or delay the onset of vascular and hepatic complications related to T2D.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0744-6) contains supplementary material, which is available to authorized users.

Pleurotus albidus Modulates Mitochondrial Metabolism Disrupted by Hyperglycaemia in EA.hy926 Endothelial Cells

Hyperglycaemia exacerbates the production of reactive oxygen species (ROS), contributing to the multiple complications associated with diabetes. Mitochondrial dysfunction is also known to be associated with diabetes. Therefore, the aim of this work was to study the effect of Pleurotus albidus extract on the mitochondrial dysfunction induced by hyperglycaemia in EA.hy926 endothelial cells. The results showed that P. albidus treatment prevented the increase in the activity of complex I of the electron transport chain and minimized the ROS production induced by hyperglycaemia. In addition, the extract minimized oxidative damage to lipids and proteins, caused an imbalance in the antioxidant enzyme activities of superoxide dismutase and catalase, and decreased the nitric oxide levels induced by hyperglycaemia. These data contribute to our understanding of the mitochondrial disorder induced by hyperglycaemia as well as establishing the conditions required to minimize these alterations.

Comparative suppressing effects of black and green teas on the formation of advanced glycation end products (AGEs) and AGE-induced oxidative stress

This study aimed at investigating and comparing the anti-diabetic potential of black and green teas. Biochemical analyses indicate higher antioxidant potency, significantly correlated with the phytochemicals present, in green teas compared to black teas. Both extracts afforded a similar level of protection to erythrocytes against peroxyl radical-induced lysis. Non-cytotoxic concentration of green and black tea extracts significantly reduced the reactive oxygen species (ROS) production (P < 0.01), lowered the oxidation of proteins (P < 0.05) and decreased the IL-6 secretion (P < 0.01) induced by AGEs or H₂O₂ in 3T3-L1 preadipocytes. Both teas also inhibited the decline in the enzymatic activities of superoxide dismutase, catalase and glutathione peroxidase induced by the pro-oxidants. The teas further suppressed the glycation of BSA mediated by glucose, ribose and MGO by reducing fluorescent AGE, fructosamine, protein carbonyl and AOPP levels. Black and green teas also inhibited the activities of α-amylase (AA₅₀: 589.86 ± 39.51 and 947.80 ± 18.20 μg mL^-1, respectively) and α-glucosidase (AA₅₀: 72.31 ± 4.23 and 100.23 ± 8.10 μg mL^-1, respectively). The teas afforded a comparable level of protection at the cellular level and against glycation while black tea exerted the highest carbohydrate hydrolysing enzymes inhibitory activity. Our results clearly show that black and green teas represent an important source of antioxidants with anti-diabetic potential.

Metabolic profiling of visceral adipose tissue from obese subjects with or without metabolic syndrome

Obesity represents one of the most complex public health challenges and has recently reached epidemic proportions. Obesity is also considered to be primarily responsible for the rising prevalence of metabolic syndrome, defined as the coexistence in the same individual of several risk factors for atherosclerosis, including dyslipidemia, hypertension and hyperglycemia, as well as for cancer. Additionally, the presence of three of the five risk factors (abdominal obesity, low high-density lipoprotein cholesterol, high triglycerides, high fasting glucose and high blood pressure) characterizes metabolic syndrome, which has serious clinical consequences. The current study was conducted in order to identify metabolic differences in visceral adipose tissue (VAT) collected from obese (body mass index 43-48) human subjects who were diagnosed with metabolic syndrome, obese individuals who were metabolically healthy and nonobese healthy controls. Extensive gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS/MS) analyses were used to obtain the untargeted VAT metabolomic profiles of 481 metabolites belonging to all biochemical pathways. Our results indicated consistent increases in oxidative stress markers from the pathologically obese samples in addition to subtle markers of elevated glucose levels that may be consistent with metabolic syndrome. In the tissue derived from the pathologically obese subjects, there were significantly elevated levels of plasmalogens, which may be increased in response to oxidative changes in addition to changes in glycerolphosphorylcholine, glycerolphosphorylethanolamine glycerolphosphorylserine, ceramides and sphingolipids. These data could be potentially helpful for recognizing new pathways that underlie the metabolic-vascular complications of obesity and may lead to the development of innovative targeted therapies.

Endocrine Disruptors Leading to Obesity and Related Diseases

The review aims to comprehensively present the impact of exposure to endocrine disruptors (EDs) in relation to the clinical manifestation of obesity and related diseases, including diabetes mellitus, metabolic syndrome, cardiovascular diseases, carcinogenesis and infertility. EDs are strong participants in the obesity epidemic scenery by interfering with cellular morphological and biochemical processes; by inducing inflammatory responses; and by presenting transcriptional and oncogenic activity. Obesity and lipotoxicity enhancement occur through reprogramming and/or remodeling of germline epigenome by exposure to EDs. Specific population groups are vulnerable to ED exposure due to current dietary and environmental conditions. Obesity, morbidity and carcinogenicity induced by ED exposure are an evolving reality. Therefore, a new collective strategic approach is deemed essential, for the reappraisal of current global conditions pertaining to energy management.

Bone disease in diabetes: another manifestation of microvascular disease?

Type 1 and type 2 diabetes are generally accepted to be associated with increased bone fracture risk. However, the pathophysiological mechanisms of diabetic bone disease are poorly understood, and whether the associated increased skeletal fragility is a comorbidity or a complication of diabetes remains under debate. Although there is some indication of a direct deleterious effect of microangiopathy on bone, the evidence is open to question, and whether diabetic osteopathy can be classified as a chronic, microvascular complication of diabetes remains uncertain. Here, we review the current knowledge of potential contributory factors to diabetic bone disease, particularly the association between diabetic microangiopathy and bone mineral density, bone structure, and bone turnover. Additionally, we discuss and propose a pathophysiological model of the effects of diabetic microvascular disease on bone, and examine the progression of bone disease alongside the evolution of diabetes.

Natural antioxidant polyphenols on inflammation management: Anti-glycation activity vs metalloproteinases inhibition

The diet polyphenols are a secondary metabolites of plants able to act on inflammation process. Their anti-inflammatory activity is articulated through several mechanisms that are related to their antioxidative and radical scavengers properties. Our work is focused on a novel approach to inflammatory disease management, based on anti-glycative and matrix metalloproteinases (MMPs) inhibition effects, as a connected phenomena. To better understand these correlation, polyphenols Structure-Activity Relationship (SAR) studies were also reported. The antioxidant polyphenols inhibit the AGEs at different levels of the glycation process in the following ways: (1) prevention of Amadori adduct oxidation; (2) trapping reactive dycarbonyl compounds; (3) attenuation of receptor for AGEs (RAGE) expression. Moreover, several flavonoids with radical scavenging property showed also MMPs inhibition interact directly with MMPs or indirectly via radical scavengers and AGEs reduction. The essential polyphenols features involved in these mechanisms are C2-C3 double bond and number and position of hydroxyl, glycosyl and O-methyl groups. These factors induce a change in molecular planarity interfering with the hydrogen bond formation, electron delocalization and metal ion chelation. In particular, C2-C3 double bond improve the antioxidant and MMPs inhibition, while the hydroxylation, glycosylation and methylation induce a positive and negative correlation, respectively.

Molecular and Cellular Mechanisms of Cardiovascular Disorders in Diabetes

The clinical correlations linking diabetes mellitus with accelerated atherosclerosis, cardiomyopathy, and increased post-myocardial infarction fatality rates are increasingly understood in mechanistic terms. The multiple mechanisms discussed in this review seem to share a common element: prolonged increases in reactive oxygen species (ROS) production in diabetic cardiovascular cells. Intracellular hyperglycemia causes excessive ROS production. This activates nuclear poly(ADP-ribose) polymerase, which inhibits GAPDH, shunting early glycolytic intermediates into pathogenic signaling pathways. ROS and poly(ADP-ribose) polymerase also reduce sirtuin, PGC-1α, and AMP-activated protein kinase activity. These changes cause decreased mitochondrial biogenesis, increased ROS production, and disturbed circadian clock synchronization of glucose and lipid metabolism. Excessive ROS production also facilitates nuclear transport of proatherogenic transcription factors, increases transcription of the neutrophil enzyme initiating NETosis, peptidylarginine deiminase 4, and activates the NOD-like receptor family, pyrin domain-containing 3 inflammasome. Insulin resistance causes excessive cardiomyocyte ROS production by increasing fatty acid flux and oxidation. This stimulates overexpression of the nuclear receptor PPARα and nuclear translocation of forkhead box O 1, which cause cardiomyopathy. ROS also shift the balance between mitochondrial fusion and fission in favor of increased fission, reducing the metabolic capacity and efficiency of the mitochondrial electron transport chain and ATP synthesis. Mitochondrial oxidative stress also plays a central role in angiotensin II-induced gap junction remodeling and arrhythmogenesis. ROS contribute to sudden death in diabetics after myocardial infarction by increasing post-translational protein modifications, which cause increased ryanodine receptor phosphorylation and downregulation of sarco-endoplasmic reticulum Ca(++)-ATPase transcription. Increased ROS also depress autonomic ganglion synaptic transmission by oxidizing the nAch receptor α3 subunit, potentially contributing to the increased risk of fatal cardiac arrhythmias associated with diabetic cardiac autonomic neuropathy.

Early urinary biomarkers of diabetic nephropathy in type 1 diabetes mellitus show involvement of kallikrein-kinin system

BACKGROUND

Additional urinary biomarkers for diabetic nephropathy (DN) are needed, providing early and reliable diagnosis and new insights into its mechanisms. Rigorous selection criteria and homogeneous study population may improve reproducibility of the proteomic approach.

METHODS

Long-term type 1 diabetes patients without metabolic comorbidities were included, 11 with sustained microalbuminuria (MA) and 14 without MA (nMA). Morning urine proteins were precipitated and resolved by 2D electrophoresis. Principal component analysis (PCA) and Projection to latent structures discriminatory analysis (PLS-DA) were adopted to assess general data validity, to pick protein fractions for identification with mass spectrometry (MS), and to test predictive value of the resulting model.

RESULTS

Proteins (n = 113) detected in more than 90% patients were considered representative. Unsupervised PCA showed excellent natural data clustering without outliers. Protein spots reaching Variable Importance in Projection score above 1 in PLS (n = 42) were subjected to MS, yielding 33 positive identifications. The PLS model rebuilt with these proteins achieved accurate classification of all patients (R2X = 0.553, R2Y = 0.953, Q2 = 0.947). Thus, multiple earlier recognized biomarkers of DN were confirmed and several putative new biomarkers suggested. Among them, the highest significance was met in kininogen-1. Its activation products detected in nMA patients exceeded by an order of magnitude the amount found in MA patients.

CONCLUSIONS

Reducing metabolic complexity of the diseased and control groups by meticulous patients' selection allows to focus the biomarker search in DN. Suggested new biomarkers, particularly kininogen fragments, exhibit the highest degree of correlation with MA and substantiate validation in larger and more varied cohorts.

Diabetic cardiomyopathy: a clinical entity or a cluster of molecular heart changes?

BACKGROUND

Although the increasing rate of cardiovascular mortality in patients with diabetes is thought to be due to the coronary atherosclerosis caused mainly by compounding factors such as dyslipidaemia and hypertension, it is now well documented that diabetes alone can lead to a vast array of molecular changes in the heart.

DESIGN

The aim of this article was to comprehensively review the pathophysiological and molecular changes leading to diabetic cardiomyopathy (DCM), as well as to critically analyse the literature that offers evidence in favour and against the existence of the overt clinical expression of this entity.

RESULTS

We included in the discussion studies that have revealed the existence of diabetic cardiomyopathy with unique remodelling pattern when compared to other types of cardiomyopathies. On the other hand, several studies debate the existence of clinically discernible cardiomyopathy caused only by diabetes and were also presented and discussed in details.

CONCLUSION

Clinicians should be aware of DCM when facing patients with diabetes in order both to recognize on time relevant symptoms and to intensively look for and treat other compounding factors, apart from optimal glucose control. Furthermore, the elucidation of the pathophysiological mechanisms leading to DCM could provide new therapeutic targets for heart disease, which will be wonderful for the good of our patients.

Uncoupling of Vascular Nitric Oxide Synthase Caused by Intermittent Hypoxia

Objective. Obstructive sleep apnea (OSA), characterized by chronic intermittent hypoxia (CIH), is often present in diabetic (DB) patients. Both conditions are associated with endothelial dysfunction and cardiovascular disease. We hypothesized that diabetic endothelial dysfunction is further compromised by CIH. Methods. Adult male diabetic (BKS.Cg-Dock7^m +/+ Lepr^db/J) (db/db) mice (10 weeks old) and their heterozygote littermates were subjected to CIH or intermittent air (IA) for 8 weeks. Mice were separated into 4 groups: IA (intermittent air nondiabetic), IH (intermittent hypoxia nondiabetic), IADB (intermittent air diabetic), and IHDB (intermittent hypoxia diabetic) groups. Endothelium-dependent and endothelium-independent relaxation and modulation by basal nitric oxide (NO) were analyzed using wire myograph. Plasma 8-isoprostane, interleukin-6 (IL-6), and asymmetric dimethylarginine (ADMA) were measured using ELISA. Uncoupling of eNOS was measured using dihydroethidium (DHE) staining. Results. Endothelium-dependent vasodilation and basal NO production were significantly impaired in the IH and IADB group compared to IA group but was more pronounced in IHDB group. Levels of 8-isoprostane, IL-6, ADMA, and eNOS uncoupling were ≈2-fold higher in IH and IADB groups and were further increased in the IHDB group. Conclusion. Endothelial dysfunction is more pronounced in diabetic mice subjected to CIH compared to diabetic or CIH mice alone. Oxidative stress, ADMA, and eNOS uncoupling were exacerbated by CIH in diabetic mice.

New thiazolidinediones affect endothelial cell activation and angiogenesis

Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor-γ (PPARγ) agonists used in treating type 2 diabetes that may exhibit beneficial pleiotropic effects on endothelial cells. In this study, we characterized the effects of three new TZDs [GQ-32 (3-biphenyl-4-ylmethyl-5-(4-nitro-benzylidene)-thiazolidine-2,4-dione), GQ-169 (5-(4-chloro-benzylidene)-3-(2,6-dichloro-benzyl)-thiazolidine-2,4-dione), and LYSO-7 (5-(5-bromo-1H-indol-3-ylmethylene)-3-(4-chlorobenzyl)-thiazolidine-2,4-dione)] on endothelial cells. The effects of the new TZDs were evaluated on the production of nitric oxide (NO) and reactive oxygen species (ROS), cell migration, tube formation and the gene expression of adhesion molecules and angiogenic mediators in human umbilical vein endothelial cells (HUVECs). PPARγ activation by new TZDs was addressed with a reporter gene assay. The three new TZDs activated PPARγ and suppressed the tumor necrosis factor α-induced expression of vascular cell adhesion molecule 1 and intercellular adhesion molecule 1. GQ-169 and LYSO-7 also inhibited the glucose-induced ROS production. Although NO production assessed with 4-amino-5-methylamino-2',7'-difluorofluorescein-FM probe indicated that all tested TZDs enhanced intracellular levels of NO, only LYSO-7 treatment significantly increased the release of NO from HUVEC measured by chemiluminescence analysis of culture media. Additionally, GQ-32 and GQ-169 induced endothelial cell migration and tube formation by the up-regulation of angiogenic molecules expression, such as vascular endothelial growth factor A and interleukin 8. GQ-169 also increased the mRNA levels of basic fibroblast growth factor, and GQ-32 enhanced transforming growth factor-β expression. Together, the results of this study reveal that these new TZDs act as partial agonists of PPARγ and modulate endothelial cell activation and endothelial dysfunction besides to stimulate migration and tube formation.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe, diabetes mellitus (DM) is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder. DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy. The mechanistic target of rapamycin (mTOR) is a promising agent for the development of novel regenerative strategies for the treatment of DM. mTOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis, insulin resistance, insulin secretion, stem cell proliferation and differentiation, pancreatic β-cell function, and programmed cell death with apoptosis and autophagy. mTOR is central element for the protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), Wnt1 inducible signaling pathway protein 1 (WISP1), and growth factors. As a result, mTOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease. Future studies directed to elucidate the delicate balance mTOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.